Wikipedia:Reference desk/Science: Difference between revisions

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::::I'm not sure the bit about Odin is true in the original mythology (I've read the Prose Edda and much of the Poetic one, though I may have forgotten something); this reminds me more of the interpretation in Wagner's Ring Cycle, and/or G.B.Shaw's interpretation of that interpretation. Anyway, certainly the restriction to not breaking covenants means that he is not really omnipotent, he is restricted by at least this law, or perhaps even by an entity that imposes the law.
::::I'm not sure the bit about Odin is true in the original mythology (I've read the Prose Edda and much of the Poetic one, though I may have forgotten something); this reminds me more of the interpretation in Wagner's Ring Cycle, and/or G.B.Shaw's interpretation of that interpretation. Anyway, certainly the restriction to not breaking covenants means that he is not really omnipotent, he is restricted by at least this law, or perhaps even by an entity that imposes the law.
::::Re:"Odin and all the other gods are anthropomorphic, which is a very dubious notion to say the least". The word "anthropomorphic" is POV-laden, as it literally means (1) "described as being similar to humans to some extent", but in practice is used as (2) "described as being similar to humans to an unrealistic extent", and what is an "unrealistic extent" remains to be debated. I think it's obvious that any god is anthropomorphic in sense (1) - being similar to humans to some extent - and it can be argued that any god is anthropomorphic in sense (2) as well - being similar to humans to an unrealistic extent. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/|]] ([[User talk:|talk]]) 15:32, 17 August 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
::::Re:"Odin and all the other gods are anthropomorphic, which is a very dubious notion to say the least". The word "anthropomorphic" is POV-laden, as it literally means (1) "described as being similar to humans to some extent", but in practice is used as (2) "described as being similar to humans to an unrealistic extent", and what is an "unrealistic extent" remains to be debated. I think it's obvious that any god is anthropomorphic in sense (1) - being similar to humans to some extent - and it can be argued that any god is anthropomorphic in sense (2) as well - being similar to humans to an unrealistic extent. <span style="font-size: smaller;" class="autosigned">—Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/|]] ([[User talk:|talk]]) 15:32, 17 August 2009 (UTC)</span><!-- Template:UnsignedIP --> <!--Autosigned by SineBot-->
:::::By "anthropomorphic" in this context, I meant specifically "so similar to humans as to be indistinguishable from them upon casual observation". This would be true in the case of Norse gods -- or indeed most of the gods from pagan mythology of the European nations -- but in the case of Jehovah, the Judeo-Christian God, this is not necessarily true (and indeed, He is most likely NOT anthropomorphic in this sense). Same with Allah, the Islamic god, according to the Koran he is not anthropomorphic but more like some kind of cosmic force (although I ''really'' have to wonder ''what kind'' of god would choose a child molester as his prophet, but that's a whole other topic altogether). [[Special:Contributions/|]] ([[User talk:|talk]]) 23:47, 17 August 2009 (UTC)
:::::By "anthropomorphic" in this context, I meant specifically "so similar to humans as to be indistinguishable from them upon casual observation". This would be true in the case of Norse gods -- or indeed most of the gods from pagan mythology of the European nations -- but in the case of Jehovah, the Judeo-Christian God, this is not necessarily true (and indeed, He is most likely NOT anthropomorphic in this sense). Same with Allah, the Islamic god, according to the Koran he is not anthropomorphic but more like some kind of cosmic force (although I ''really'' have to wonder ''what kind'' of god would choose a [[Muhammad|child molester]] as his prophet, but that's a whole different topic altogether). [[Special:Contributions/|]] ([[User talk:|talk]]) 23:47, 17 August 2009 (UTC)
:::::An infinitely powerful god can be anthropomorphic if he/she/it feels like it. You could imagine how that would come in handy. Odin just needed a good lawyer. I'm sure he could find a way to repeal his pact with humanity without breaking the pact in the process. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 21:52, 17 August 2009 (UTC)
:::::An infinitely powerful god can be anthropomorphic if he/she/it feels like it. You could imagine how that would come in handy. Odin just needed a good lawyer. I'm sure he could find a way to repeal his pact with humanity without breaking the pact in the process. [[User:SteveBaker|SteveBaker]] ([[User talk:SteveBaker|talk]]) 21:52, 17 August 2009 (UTC)

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August 12

Southern New Zealand

Do New Zealand usually get snow in the south? the south tip is 47 degrees away from equator, since it has marine climate I don't think it can get snow at land basin level. Can summer get up to like 70 F?-- (talk) 00:45, 12 August 2009 (UTC)

Do you mean south island or the south of the south island? A lot of the south island gets snow in winter, they have permantent glaciers and the whole works. You're right about avereage summer temps being around 70f. Vespine (talk) 00:55, 12 August 2009 (UTC)
I mean south island. Land basin level like Irvine, CA ground level not moountain. I thought it is unlikely to get snow in valley-basin level, just mountain gets permanent glacier level.-- (talk) 01:34, 12 August 2009 (UTC)
Looks like it snows all the way down to sea level -just not often.[1] (talk) 01:45, 12 August 2009 (UTC)
The record high temperature for Christchurch is 42 C (108 F). —Preceding unsigned comment added by (talk) 02:02, 12 August 2009 (UTC)
Punta Arinas is 53 South, the tip of new Zealand is 47 South in latitude. They don't get much snow, just occassionally (not every year) but bone-chilly!-- (talk) 02:07, 12 August 2009 (UTC)
In Queenstown not much snow this year. Avg. is like 40s this winter, avg low of low 30s. Is just enough for oranges to freeze.-- (talk) 02:11, 12 August 2009 (UTC)
Take a look at [2] or older dates [3] e.g. [4] and reach your own conclusions. You may be also interested in the individual monthly summaries [5]. Sadly this does not provide stuff like the mean temperatures for places other then a few main centres but you can get older data at [6], e.g. [7]. Beyond the data in the summaries, there are is no per location data for snowfalls that I'm aware of probably because you're right, it happens infrequently enough that it isn't of great interest to many people Nil Einne (talk) 08:41, 12 August 2009 (UTC)
In my 4 years in Dunedin (2004-2007), every year we had at least light snowfalls at sea level. In particularly cold years it can settle up to 5cm or so for a couple of days. It snows on the beaches too. Aaadddaaammm (talk) 13:26, 12 August 2009 (UTC)

hot ice on Uranus and Neptune

For a long time I always wonder what is a hot ice in Uranus and neptune's liquid layers. Is it a semi-solid junks? Does slush mean tarlike substance or I don't know what. Some scientist beielve Uranus and Neptune's mantle is made of molten rock, water and ice thoguh-- (talk) 03:30, 12 August 2009 (UTC)

The sections Uranus#Internal_structure and Neptune#Internal_structure give pretty good descriptions. They say that each planet has a small core of molten rock and metal (since those are the densest) and then a liquid mantle above that of mostly water, methane and ammonia. These chemicals are referred to as "ices" but that doesn't mean they're in a solid or slush form. See Volatiles. Rckrone (talk) 04:12, 12 August 2009 (UTC)

Speed of sound in a fluid

According to my physics textbook, the speed of sound in a fluid is v=sqrt(B/ρ), where B is the Bulk modulus and ρ is density. How is this derived? Mo-Al (talk) 05:34, 12 August 2009 (UTC)

For one way to derive it, see section 31.4 in this book. Red Act (talk) 06:24, 12 August 2009 (UTC)
Conversely, one might say that the microscopic bulk modulus is defined by the macroscopic fluid speed. It depends which direction you consider more "basic" or "fundamental" - I think most fluid physicists would say that the bulk modulus, being essentially an implication of the molecular theory of gas (or liquid), is more fundamental than the sound speed. Nimur (talk) 20:58, 12 August 2009 (UTC)

IQ and Dunning-Kruger effect

Are people with a high IQ less prone to the Dunning-Kruger effect and Impostor syndrome? NeonMerlin 07:38, 12 August 2009 (UTC)

AFAIK the complexe d'imposture is more likely to affect people with a high IQ than others since it tends to affect people who are over-achievers to the point where their own success seems surreal to them. However, I am just basing the response on what I was taught on a "being an executive mentor" course a decade ago so this may be wrong (plus these people read psychology which is pretty sloppy as a science from the point of view of establishing "facts")--BozMo talk 09:40, 12 August 2009 (UTC)
OR: I have high IQ scores and often have feelings similar to the impostor effect, but I'm no over-achiever. I'm simply depressive.  —Tamfang (talk) 22:33, 6 October 2009 (UTC)
Reading the article on the Dunning-Kruger effect however seems to indicate that it is exactly the opposite: specifically it is much more likely to affect low IQ individuals. Given that these two are obvious opposites I hope this isn't a homework question. --BozMo talk 09:45, 12 August 2009 (UTC)
This paper seems to be relevant.--droptone (talk) 12:28, 12 August 2009 (UTC)

Viewing the Perseids meteor shower from Netherlands

I've read the article on Perseids meteor shower. It says that the meteors are more visible in the Northern Hemisphere. I'm in the Netherlands. What I'd like to know is where in the sky to look towards. I can look mainly north, toward the big dipper and northern star, or any other direction. I can look straight up, or more towards the horizon. Last night, I saw one meteor, in about 5 minutes watching, and it went directly across the face of the Big Dipper, more or less in the northeastern sky. Thanks if you have advice. —Preceding unsigned comment added by (talk) 08:50, 12 August 2009 (UTC)

As noted in the article on the Perseids, the meteors of this shower appear to come from the constellation Perseus - so you want to be looking in that direction. To find out where the constellation Perseus is, look on a star map (for instance, here) - in the evening, Perseus will be low in a NNE direction, below Cassiopeia. — QuantumEleven 09:40, 12 August 2009 (UTC)
The radiant is in Perseus, so meteors closer to the radiant are faster and leave shorter trails; they're the ones which enter the atmosphere directly and quickly burn up. Farther from the radiant, the meteors are slower and leave long, impressive trails because they skim the atmosphere instead of plunging directly into it. You probably want to see some of those, so the best place to look is 20-40 degrees away from the radiant, not at it. --Bowlhover (talk) 09:20, 13 August 2009 (UTC)
If you find somewhere with a clear sky and not too much clutter on the horizon (ie not in the middle of tall buildings) - then head out there during the peak of the shower, you won't need to know which direction to look - it'll be pretty obvious as the meteors streak past. If Perseus is low in the sky for you (as QuantumEleven says) then the meteors will be just grazing the atmosphere. That means that you may not see so many as when Perseus is high in the sky - but those that you do see should leave long, impressive trails across a large fraction of the sky. SteveBaker (talk) 11:27, 12 August 2009 (UTC)
I usually lie on my back and look straight up. That way you catch lots of meteors with your peripheral vision. They can be a very long way from the radiant. Of course once the moon is up you need to look away from it, otherwise it will "blind" you.--Shantavira|feed me 11:50, 12 August 2009 (UTC)
On the BBC yesterday it said if you find the Moon and look about 60 degrees away from it you should see the meteors quite clearly. I can't remember which direction to turn away from the moon, but you will of course be able to experiment for yourself! --TammyMoet (talk) 17:25, 12 August 2009 (UTC)

Time Dilation with Radioactive Elements.

I'm not too well educated in this stuff but from what I get time is dilated (slows down) for a observer moving with a speed v relative to an observer at rest (or otherwise). I know this has been confirmed with ultraprecise clocks on planes. I just was wondering if a guy gets on a plane with 100 grams on C-14 and goes at a speed so that each second for him is 2 seconds for an observer at rest (which I'm just estimating would be sqrt(.75c)). After 2 halflifes of C-14 for the observer at rest (11460 years) would there be 50 grams of C-14 (which means only one halflife worth of decay) left for the guy on the plane. I mean this just to be roughly 50 grams because I think that half-lifes aren't exact- that you can't exactly predict whether it decays or not (Schrodinger's cat?). Everything tells me it should be 50 grams but for some reason I was just curious. Has any test like this been done? (talk) 09:10, 12 August 2009 (UTC)

Yes. The half-life is determined in the rest frame of the decaying element. The observer at rest will indeed have to wait two half-lifes to see 50 grams of C14 decay.

This is observed experimentally with muons in cosmic radiation : the muon is a very short-lived particle which is created in the upper atmosphere by cosmic radiation. Judging from the muon half-life, you would not expect the muon to reach the earth's surface, since it will have decayed long before that. However, the muons are very fast, and their time goes slower than ours. This is why muons do reach the earth's surface. —Preceding unsigned comment added by (talk) 09:43, 12 August 2009 (UTC)

I believe there have also been experiments run in particle accelerators with decaying particles that verify the predictions of special relativity very precisely. --Tango (talk) 16:00, 12 August 2009 (UTC)
Ok thanks Tango that was what I was looking for. I knew about the muons but for some reason I kept thinking the radioactive elements would ignore special relativity (!?). (talk) 16:34, 12 August 2009 (UTC)

Purpose of cylinder at back of Renault FT-17 tank

From the Humanities RD:

What is the purpose of the "tail" apparatus on this Renault FT-17 tank, including the cylinder and chains? (This tank is exhibited in the Compiègne Forest at the location where the armistice of the First World War was signed.)

From the side
From the back

David.Monniaux (talk) 10:27, 12 August 2009 (UTC) —Preceding unsigned comment added by Quest09 (talkcontribs)

The tail bit was used to aid the tank in crossing trenches. Bear in mind that the motor was located at the rear of the vehicle. Thus the tank could have moved its unsupported front over the gap of the trench without "toppling" over. I could not find any information on the purpose of the barrel and the chains. --Cookatoo.ergo.ZooM (talk) 11:00, 12 August 2009 (UTC)
The barrel and chains look kind of like a small, unassembled Mine flail. Very thin though. Fribbler (talk) 11:04, 12 August 2009 (UTC)
Yes, but this tank is from Great War and mine flail, according to the article, were first used in the WWII.Quest09 (talk) 11:10, 12 August 2009 (UTC)
Hmmm. No other pictures I found had these on it. Perhaps it was simply a spare fuel tank and tow-chains (the chains do have hooks) for salvaging damaged vehicles? Fribbler (talk) 11:16, 12 August 2009 (UTC)
Other stuff tied on at the back
The barrel doesn't appear to be a part of the tank per-se. None of the other pictures of the tank in our article show a barrel there. In the picture to the left here, you can see that there is a bunch of other stuff tied on at the back of the vehicle. I suspect that the crew simply used it as a place to conveniently stow things that they didn't have room for inside. (They were pretty cramped in there!) The barrel has "OIP" and then "30" written on the top. I could believe that it's a 30 litre barrel...but I have no idea what "OIP" means. Similarly, the chain (there is only one - the thinner one in the background is just a part of the exhibition area) may just be a tow chain or something - it has hooks at either end, so that's pretty likely. Those early tanks got stuck and broke down a LOT - carrying a tow chain would have been a good idea! These photos from Compiegne are really nice - they should be in our article about the tank somewhere. SteveBaker (talk) 11:19, 12 August 2009 (UTC)
OIP may be 'Omnium International des Pétroles', a french company formed in 1911, though I can't find much more about it. Mikenorton (talk) 12:06, 12 August 2009 (UTC)
I would say spare fuel for the barrel. The tail can be unbolted and let down, then have a barrel rolled on. Then you could baulk the tail with a 4x4 and just back the tank up to close the tail. Once you get up close to the battle zone, you siphon out the fuel in the barrel. And if you have to store fuel outside the vehicle in battle conditions, well that's as far away as you can carry it from the people.
It does seem that the tail is for climbing embankments/trenches. On the chain, I got nuthin'. It could be used to tow a weight with ground pressure closer to human values to set off anti-personnel mines, indeed if that barrel was filled with sand, it would do quite well as a mine-finder. Franamax (talk) 12:03, 12 August 2009 (UTC)
How about shooting the fuel drum, and then shoot the crew when they bailed out of the tank? I doubt it would be tenable inside with all that petrol running down the back. But carrying spare fuel on the back would beat running out of fuel. Maybe they refueled when they arrived at the battlefield but left the tank behind when they assaulted the trenches. Edison (talk) 15:23, 12 August 2009 (UTC)
External fuel drums are not uncommon in tanks. You use the external tank to get from the friendly area to the combat area. Then, you discard the tank. Now, once in the combat area, you have a full tank of fuel and all those tanks who didn't have an external tank used up half their fuel to get to the combat area. There is very little risk of someone attacking the external tank since it is only used in friendly areas. As a side benefit, those with external tanks are allowed to expend nearly all their internal fuel during combat. All they need to do is leave the combat area and then a new external tank can be attached to get all the way back to the tank's unit. -- kainaw 15:28, 12 August 2009 (UTC)
If I recall, even some of the more modern Soviet tanks (T-72 perhaps?) used oil drums as external fuel tanks, with a switch to jettison the things if you found yourself in combat. Googlemeister (talk) 15:32, 12 August 2009 (UTC)
Correct. There was a T-72 on display when I was at 29 Palms. It had an external tank. I do not know of any modern American tanks that have external fuel capability. -- kainaw 15:34, 12 August 2009 (UTC)
It seems the M1 Abrams at least does (that article says "Another was put out of action in an incident when fuel stowed in an external rack was struck by heavy machine gun rounds") and this article gives the M1's range "with external tanks". -- Finlay McWalterTalk 17:14, 12 August 2009 (UTC)
Even in a combat situation, it still seems preferable to have the majority of the fuel stored outside of the tank. If the fuel is hit, the tank might be stranded with limited range (only what is inside its internal tank); but the majority of the damage would be dissipated without destroying the tank and injuring its crew. Nimur (talk) 20:32, 12 August 2009 (UTC)
Even in a tank I am not sure that you want a barrel of volatiles to be a nice vulnerable target for explosive shells and even something like a heavy machine gun. Probably better that the fuel is not hit at all, and you refuel every 200 miles or so from your friendly supply units fuel trucks. Back in WW1, might have been a different story. Googlemeister (talk) 14:03, 13 August 2009 (UTC)

stringing power strips

When there is a shortage of outlets, and you have a lot of things to plug in, is there any danger in stringing together several power strips to meet the needs? --Halcatalyst (talk) 12:25, 12 August 2009 (UTC)

It depends on the circuitry you have in your house, and it's capabilities. At some point, for any circuitry, with enough things turned on and drawing current you are going to trip the circuit breaker, or fuse or whatever. When we first moved into our house a few years ago, we couldn't run the microwave and toaster at the same time without tripping the breaker for the kitchen, so we had someone re-do some of the electrical work. —Akrabbimtalk 12:35, 12 August 2009 (UTC)
So long as you don't exceed the current capacity of either the circuit or each strip, and assuming all the ground pins work and there's no bare wires or other problems, you should be fine. If you are plugging in a lot of varying loads or things you use all at once, you need to do some math to be sure you aren't causing an overload. Check the number of watts for each device, add them up and divide by a hundred. Compare that to the number of amps of the fuse or circuit breaker and you should be OK. For instance, if you have a 1200-watt heater and a 40-watt light, (1200+40)/100 = 12.4, which would be fine on a 15-amp circuiot. However, plugging all of your rock band's equipment into one string of power strips could be a bad idea. Franamax (talk) 12:42, 12 August 2009 (UTC)
Note that this calculation only works if you live in places with 115V mains voltage (eg the US). For 220V mains voltage, divide by 220. — QuantumEleven 14:22, 12 August 2009 (UTC)
Fire. It is always a bad idea to plug a power strip into another power strip and, although I suppose it depends on where you are, I would imagine in most places it's against the fire code. At least, I know it is in New York. If you really need more than 2x6 outlets, you should consider extension cords to other outlets nearby or getting extra ones installed for safety and legal reasons. ~ Amory (usertalkcontribs) 13:04, 12 August 2009 (UTC)
Out of curiosity, how does plugging several power strips into each other increase the risk of fire? — QuantumEleven 14:23, 12 August 2009 (UTC)
more plugs = more 'opportunities' for failure? (talk) 15:10, 12 August 2009 (UTC)
It can cause Power quality problems due to the increased resistance in the ground path. I knew an audio/video recording studio which developed unacceptable hum (in the analog days) due to the high ground resistance from the connections of plugs when they octopussed the wiring via power strips. The problem went away when every piece of equipment was grounded to the same point and only hard wired outlets were used. Having many outlets fed from one outlet increases the risk of a fire, since the breaker might not work, the fuse might be oversized (30 amp fuse protecting a circuit rated at 15 amps), or there might be an oxidized high resistance connection in the wiring, or other problems.. Electrical safety codes were written in blood, so to speak. Edison (talk) 15:18, 12 August 2009 (UTC)
When I was about 5, i found where my parents kept all the double adapters, so i thought it would be fun to plug then all into the wall. I think I got to about 4 or 5 until i got a big shock. Learned that lesson the hard way. Vespine (talk) 02:05, 13 August 2009 (UTC)
The term de jour is Daisy chain (electrical engineering). --Tagishsimon (talk) 02:10, 13 August 2009 (UTC)

Transmission of swine flu

Is it that H1N1 flu may get transmitted into your body ONLY when you come in contact (about 6 feet close) with a suspected case of SWINE FLU ,or flying in the air it may enter inside? (talk) 14:57, 12 August 2009 (UTC)

I think, I may be wrong, that H1N1 cannot live on surfaces very long and that contact is the main way of spreading. Dogposter 15:14, 12 August 2009 (UTC)

"This is thought to occur in the same way as seasonal flu occurs in people, which is mainly person-to-person transmission through coughing or sneezing of people infected with the influenza virus. People may become infected by touching something with flu viruses on it and then touching their mouth or nose."[8] -- (talk) 15:15, 12 August 2009 (UTC)
Our article on influenza says "The length of time the virus will persist on a surface varies, with the virus surviving for one to two days on hard, non-porous surfaces such as plastic or metal, for about fifteen minutes from dry paper tissues, and only five minutes on skin". Gandalf61 (talk) 15:17, 12 August 2009 (UTC)
It should also be reemphasized that H1N1 or "Swine flu" is entirely "typical" in terms of being a flu; it is not more contageous, more virulent, and does not cause worse symptoms than any other standard strain of Influenza A that come around every year. The only problem is that, as a relatively rare and new strain, we don't have the vaccines for it yet. But otherwise, it is just the flu. --Jayron32 01:39, 13 August 2009 (UTC)
Reliable source please? Stats at the 2009 flu pandemic article seem to indicate indicate higher mortality among the infected than typical seasonal flu. I suppose this could be the gap between the number actually infected and those going to a hospital or doctor and getting tested, but mild cases of seasonal flu also are likely to forgo doctor visits. As for transmissability, it continued to spread in the Northern Hemisphere countries through the summer when the seasonal flu drops off. It is not a matter of just not having the vaccines. Edison (talk) 03:20, 13 August 2009 (UTC)
It's not just lack of vaccines, it is lack of natural immunity. I've seen estimates that about a third of people will get swine flu over the next couple of years, a given strain of seasonal flu won't infect anywhere near that many people and that isn't because of vaccines - in the UK, at least, only vulnerable groups are vaccinated against seasonal flu. If you have had one strain of flu you will generally have some degree of immunity to other similar strains. I don't think there are any strains similar to swine flu in circulation, so very few people have any significant immunity to it. Of course, that doesn't change the fact that it is just flu and a few days bedrest will cure it in the vast majority of people. --Tango (talk) 02:52, 13 August 2009 (UTC)
And while right now it is "just the 'flu", the reason the World's epidemiologists are so worried is that studies of its genetic code reveal that it has far more potential than the average strain of 'flu to mutate into something (a) much more contagious and (b) much more deadly, as did the H1N1 Spanish 'flu of 1918, which it more closely resembles than most seasonal 'flues. (talk) 03:44, 13 August 2009 (UTC)
I've heard that point before, but I've never heard any estimates of the likelihood of it happening. Do you know of any? I suspect (based on past experience with such news stories) it is extremely unlikely and is being sensationalised by the media. --Tango (talk) 17:12, 13 August 2009 (UTC)
The publicity about the importance of hand washing and use of hand sanitizers, and staying home when sick, may decrease the incidence of seasonal flu and common cold as a side effect. The swine flu seems to be killing a larger portion of infected healthy young adults and pregnant women that seasonal flu usually does. Edison (talk) 19:22, 13 August 2009 (UTC)

Bluetooth Marketting

What is meant by bluetooth marketting???where is it used???Need some details on it please.thanks. —Preceding unsigned comment added by Gd iitm (talkcontribs) 16:26, 12 August 2009 (UTC)

Check out Bluetooth marketing. Aaadddaaammm (talk) 16:47, 12 August 2009 (UTC)

It doesnt give the exact details on what is meant by bluetooth marketing and the software used in it.Pls help —Preceding unsigned comment added by (talk) 18:28, 12 August 2009 (UTC)

Grantt Chart

hey friends,

wiki dosent contains anyting about grantt charts.i m facing some problems in understanding a problem on grantt chart. please help me how to understand it. a grantt plan with a 80% gurantee is used on a job that is 30% process controlled.The plan uses a standard hourly rate of Rs20 and a bonus rate of Rs 25 per hour.the standard time for this job is 0.1 hourper piece.determine earnings per day(8 hour) of work,if 85 pieces were produced on a given day.comment on merit of plan.

SCI-hunter (talk) 12-8-2009 —Preceding unsigned comment added by SCI-hunter (talkcontribs) 17:18, 12 August 2009 (UTC)

Do you mean Gantt charts? --TammyMoet (talk) 17:22, 12 August 2009 (UTC)

thanks for the link.but do help me to get through the question.. (talk) —Preceding undated comment added 07:32, 13 August 2009 (UTC).

Wikipedia doesn't do your homework for you. I suggest looking at the notes you took during class. DJ Clayworth (talk) 19:18, 13 August 2009 (UTC)

How to cause hypomania

Are there any known methods for causing hypomania in oneself or a willing subject? NeonMerlin 17:39, 12 August 2009 (UTC)

This is not medical advice, but the symptoms sound a lot like someone who has done quite a bit of cocaine. -- (talk) 18:13, 12 August 2009 (UTC)
"Induced Hypomania" is usually caused by anti-depressants. One similar situation where we get a similar profile of signs and symptoms would be a person who has just achieved something, be that passed an exam, completed a marathon etc. Fribbler (talk) 18:22, 12 August 2009 (UTC)


When does NASA expect to start sending back photos of pluto? How large of a window do they have to get good high res photos? Googlemeister (talk) 19:39, 12 August 2009 (UTC)

(ec) This should help with your answer - New Horizons#Planned. The probe will make a pass at 11:47 UTC, July 2015. It will be traveling at 13.78 km/s, or about 31,000 miles per hour, so the window is probably not very large, especially given it will be only 10,000 - 14,000 km away at that time and will flyby Charon, Hydra, and Nix within 15 minutes. They already have a picture, but it ain't exactly hi-res... File:112806_pluto_animation.gif. ~ Amory (usertalkcontribs) 20:25, 12 August 2009 (UTC)
I assume you're talking about the New Horizons mission. It arrives at Pluto on July 14, 2015. Based on the length of its encounter with Jupiter, I'd guess there's a two- to four-week window of good observations for the Pluto encounter. — Lomn 20:26, 12 August 2009 (UTC)
Ah, I see our article goes into much more detail at the Pluto flyby subsection. New Horizons will have greater resolution than Hubble for about three months. However, as for when NASA expects NH to start returning pictures of Pluto -- that first happened in 2006. — Lomn 20:28, 12 August 2009 (UTC)

The window will be small, however, you can take several hundred pictures within 30 minutes, right? And you aren't NASA. I say we'll have an awesome slide-show awaiting us when they release it. —Preceding unsigned comment added by Hubydane (talkcontribs) 19:51, 14 August 2009 (UTC)

Pain sensitive areas on human body

What are some surprisingly pain sensitive areas on the human body? My cuz told me if you took your finger and hook your perputrator in the mouth (outside the teeth) like a fish, it would be very painful for him. However I tried it on myself and its not that painful like a swift kick in the you-know-where for guys. --Reticuli88 (talk) 20:01, 12 August 2009 (UTC)

Perhaps you could read Pressure point. There are a few mentioned in that article. Googlemeister (talk) 20:13, 12 August 2009 (UTC)
Repeatedly twist a knuckle into the upper/mid sternum area (where the bone is near the surface) - or make a fist and rapidly rub your foreknuckles up and down the same area. Surprisingly painful. --Kurt Shaped Box (talk) 22:03, 12 August 2009 (UTC)
I really like going for the inner wrist or inner elbow. If someone's infringing on your space it's often with their arms; these are the two soft, nerve-y points that are thereby exposed. You squeeze, they feel pain, you release, they are fine. No lasting damage. Vranak (talk) 04:23, 13 August 2009 (UTC)
You physically assault people who get too close to you?? Exxolon (talk) 00:39, 14 August 2009 (UTC)
I have done so in the past, yes, but only with my brother. Vranak (talk) 16:36, 15 August 2009 (UTC)

If someone assaults you, simply punch as hard as you can directly on their clavicle (collar bone). It's an easy bone to break, but surprisingly painful. Other painful places: 1. Gonads 2. Ribs 3. The inner thigh, close to the gonads 4. Kick 'em in the knee. 5. If you place your finger on the back of you lower jaw (close to your earlobe) then move 1/2 in - 1 in toward the chin. Move your finger toward your throat. There is a gland there, and I guarantee that if you poke anyone there hard enough, you win. Hubydane (talk) 19:56, 14 August 2009 (UTC)

Punching someone in the solar plexus (just below the sternum) really hurts too, and also "takes the wind" out of the assailant (which would put you at an advantage in the fight, or give you time to escape). An uppercut to the jaw would work too, but you gotta be quick with the punch. FWIW (talk) 03:41, 16 August 2009 (UTC)

Fat joe

Would it be possible to 'brew' coffee in a fat (for instance olive oil or clarified butter) rather than in water? Is this ever done for culinary purposes? If the boiling point of olive oil is so much higher than that of water, it seems to me that it would be a better substrate for coffee, because the grounds would rech a higher temperature without burning. I would prepare it in a pan, as if I were making a roux, and keeping the temperature a bit below 100 C. Then I would strain the oil to remove the grounds. Having produced coffee oil (or coffee butter), I can't think of what use it might be put to. I guess you could use it as a flavoring, or allow the butter to cool and use it as a spread. Would it be fully caffeinated? LANTZYTALK 20:07, 12 August 2009 (UTC)

It will probably wreck the plumbing of your coffee machine if it is a drip or percolator design. Also, these machines need to heat the liquid up to steam; I don't know if oil will vaporize in a way that will flow through the plumbing. Maybe an all-passive device such as a Moka pot (not a mocha pot!) would be a better maker for your purposes. I'd still worry about gumming up the fluid paths with oily residue; it will be tough to clean and your future coffee will taste weird until you get rid of the residue. The coffee flavors, including the caffeine, are present in the fat/oil of the coffee bean, so they should dissolve nicely if you can get hot oil to flow over them. However, most culinary uses will just grind the coffee very very finely (finer than espresso) and mix it directly into a cake-batter or other food item. Nimur (talk) 20:37, 12 August 2009 (UTC)
I wouldn't be using a coffee maker or any such device. To quote myself, "I would prepare it in a pan, as if I were making a roux." LANTZYTALK 22:39, 12 August 2009 (UTC)
My apologies for asking a question within a question, but it seemed relevant so I thought I'd go ahead: would the nature of the solvent used to do the brewing (i.e. polar/non-polar) be important? Basically, would 'brewing' coffee in oil cause the caffeine (and other chemicals) in a standard cup of coffee to be extracted from the bean in the same way (or even at all) that using water would? If so, how does the extraction proceed chemically? Korokke (talk) 21:59, 12 August 2009 (UTC)
Indeed, this is the kernel of my question. I am curious about the chemistry here. LANTZYTALK 22:39, 12 August 2009 (UTC)
Water, being a semi-polar, semi-nonpolar solvent, works well at extracting coffee oils, and caffeine. Water laced with carbon dioxide is even better at pulling the caffeine out; this is called "decaffeination" and it works by a combination of physical and chemical solution (you probably cannot get a supercritical fluid in a frying pan - not even a pressure cooker). This 1972 patent suggests several edible esters which are "more effective". Oil will probably also dissolve the caffeine and other oils in the grounds. This report suggests some solvents will override the flavor of the coffee. This report suggests a water + oil + emulsifier mixture as even better than oil. Nimur (talk) 22:45, 12 August 2009 (UTC)
What about a mixture of water and hot ethanol? Then evaporate the ethanol off if you don't want an alcoholic drink. It also depends whether the caffeine is protonated or not -- I imagine that in the presence of tannins, a lot of the caffeine will be in protonated form and therefore would not like to bind with nonpolar solvents. John Riemann Soong (talk) 13:19, 13 August 2009 (UTC)
Thanks for the comments, everyone. LANTZYTALK 02:22, 15 August 2009 (UTC)

polar day animals

During the polar day, how do animals know when to sleep? —Preceding unsigned comment added by (talk) 21:54, 12 August 2009 (UTC)

When they are tired? There's no reason for conventional circadian rhythm. "Hours" are a human invention; they have no real basis in nature, except that in some regions, they map well to an astronomical cycle; in polar regions, animals are adapted to the day-night cycle that they experience. Nimur (talk) 22:40, 12 August 2009 (UTC)
Other than right exactly at the poles, there are always daily fluctuations in light levels, even if there is some light through the entire day -- the fluctuations grow larger the farther you move from the poles. I don't remember seeing any research specifically about polar animals, but it seems likely that they have heightened sensitivity to small fluctuations. ("Hours" may be a human invention, but 24-hour-ish circadian rhythms are built deeply into animal biology -- the genes that drive them in fruit flies have a strong resemblance to the genes that drive them in mammals.) Looie496 (talk) 22:57, 12 August 2009 (UTC)
That is interesting, because 200 MYA, the day was only 23 standard hours. I wonder if really really old species might have had biology for say a 20 hour day. Googlemeister (talk) 13:55, 13 August 2009 (UTC)
Even at the poles, there is variation - the earth's rotational axis is tilted remember. SteveBaker (talk) 02:48, 13 August 2009 (UTC)
At the poles, the sun appears to rotate around the observer but stays the same distance above the horizon for the whole day. As you move away from the poles, it starts to shift up and down as well as appearing to rotate. Looie496 (talk) 15:43, 13 August 2009 (UTC)
There is seasonal variation, there isn't daily variation (unless the sun is fairly low and goes behind hills at some times during the day). --Tango (talk) 23:29, 13 August 2009 (UTC)


I just watched a programme on TV with airport border officials placing metal tubes through an X-ray scanning machine to check the internal contents. To me, these tubes appeared shiny, and thus light must have been reflected off the smooth surface of the tube (a property which makes metals appear shiny, right?) If X-rays are merely photons of a different wavelength to that of visible light, wouldn't they be reflected too, and thus the internal contents of the tube would not be visible since the photons would be reflected away from the surface? Even so, they did manage to view the contents, so how is this possible?

Regards, --—Cyclonenim | Chat  22:50, 12 August 2009 (UTC)

Different wavelength of photons are absorbed by different materials. In order for a photon to be absorbed (and, in the case of a mirror, re-remitted), there has to be an electron that can use the photons energy to change to a different energy state. In individual atoms and non-conducting crystals, there are only discrete levels of energy an electron can have, and only photons that correspond to the change in energy between two such states can be absorbed or emitted. Metals are very good conductors and very shiny because their electrons are not in discrete orbitals, but merge into energy bands. Thus, for a photon with an energy that is much smaller than the widths of those bands, there will normally be an electron ready to absorb it. As the energy goes up, the chance to find a photon that can absorb the energy while staying in a given band goes down. X-ray photons are energetic enough that absorption is a relatively rare event, hence they can pass through many substances quite well. --Stephan Schulz (talk) 23:36, 12 August 2009 (UTC)
I would like to point out that even though the answer above is essentially correct, it makes the fairly commom mistake of stating that reflected photons are absorbed and re-emitted. Reflected photons are never absorbed, they are reflected. Dauto (talk) 00:02, 14 August 2009 (UTC)
For more information, see the transmittance, absorbance and reflectivity articles, which mention how all those optical properties depend on the incident photon’s wavelength (or frequency), and electronic band structure and band gap for more detailed information about the quantum mechanical properties of a solid that result in those optic properties. Red Act (talk) 23:58, 12 August 2009 (UTC)
It's not hard to visualise: Imagine a piece of red tinted glass. You hold it up to the light - white light heads into the glass - only red light comes out. All of the other colors are absorbed or reflected. It's the same deal with your container - it lets "x-ray light" through and absorbs or reflects all of the "visible colors". SteveBaker (talk) 02:46, 13 August 2009 (UTC)

Goumi (Elaeagnus multiflora)

What is the highest daytime temperature that Elaeagnus multiflora can tolerate? Thanks in advance, --Dr Dima (talk) 23:45, 12 August 2009 (UTC)

Global warming

News always say global warming but we don't notice this much greenhouse gas. In Los Angeles-orange county climate changes hasn't been affect too much. Antartica, Greenland, and Artic Circle places haven't been affect too much. The winter is getting colder. In Miami, last winter got as cold as 30 F enough to freeze an orange solid rock. How is global warming affecting the climate changes? The place my 10th grade english teacher grew up in New Jersey start snow in late October then melt in April.-- (talk) 23:55, 12 August 2009 (UTC)

Of course we "notice" the increase in greenhouse gases - see Keeling curve. Greenland and the Arctic have been warming up very significantly, as has most of the rest of the globe. See this graphic. Climate trends are long-term - typically measured over 30 years or more, looking at one year or the other is insignificant. Have you read global warming and instrumental temperature record? --Stephan Schulz (talk) 00:31, 13 August 2009 (UTC)
The Arctic circle not affected too much? The Arctic ice has been repeatedly setting records in recent years for how little ice it gets down to in the summer, and it’s expected to be completely ice-free during the summer within a matter of years, something that hasn’t happened in the last 700,000 years. It’s a very rare thing going on in the Arctic. See Arctic shrinkage. Red Act (talk) 01:09, 13 August 2009 (UTC)
Your teacher, just like many, many people, is using their personal experience to make a judgment about whether global warming is real. Personal experience, unfortunately, is anecdotal evidence and is worth, basically, nothing, because they are using very few data points and reliance on human memory (as in, "Feels cold today. Hm."). Confirmation bias unfortunately results. Reading the scientific reports would be more valuable. Tempshill (talk) 01:53, 13 August 2009 (UTC)
It's "global" warming - and "climate" change. It's not necessarily "local" warming or "weather" change. The distinction is crucial. On the average, the entire planet is getting warmer. That doesn't mean that some places won't get cooler - that's perfectly possible. The climate is changing - that's a long-term thing...the short term weather may change - or it may not. Some places in the world may get much warmer than the average - other places, not so much.
For example, here in Texas, summer days vary from about 90 degrees (F) to about 110 degrees F. The "weather" can vary by about 20 degrees from day to day through the summer. But the average temperature of the planet has only increased by a few degrees. Let's say it's 3 degrees of average global increase: So, sitting here in Texas, watching the thermometer, we might start seeing extreme 113 degree days - breaking the occasional record - and we might find that there are no more 90 degree days - with the temperature only ever getting down to 93. But most of the time, the temperature goes up and down - if it's 105 today, does that prove there is global warming? Not really...105 degree days have always been here.
You have to look at the big picture. That glaciers are retreating all around the world. That the ice at the north pole is vanishing at an alarming rate - that the south polar ice is breaking up - that plants and animals that are normally seen close to the equator are becoming more common further from the equator. That cold-loving plants are becoming harder to find in low lying areas and you can increasingly only find them higher up on mountain slopes. Trust me, this is very real - but that doesn't mean that all of a sudden you're going to get really, really hot weather every day...that's just not how it works. SteveBaker (talk) 02:40, 13 August 2009 (UTC)
Yes, having 3 exceptionally cold winters and cool summers in a row where I am does not prove that global warming is not happening, because this area is not the entire globe. Googlemeister (talk) 13:49, 13 August 2009 (UTC)
As I pointed out above, the "entire planet" probably is not getting warmer. The average surface temperature is rising, or the average ocean surface temperature - because the climate and atmospheric interactions are redistributing energy in a different way - very probably due to the chemical changes that human industrial activity has unleashed into the atmosphere (notably, carbon, but also water vapor, CFCs, and other things that are less well understood). For the planet to actually warm, there would need to be a change in the incident solar radiation. The issue is more properly called "global climate change" than "global warming" - even when the most significant worries are warmer summers and melting polar ice caps. There is a really huge ambiguity when people talk about the "temperature of earth" - and they should use more precise terminology to avoid confusion. When the earth's surface (where we live) raises temperature, that energy has to come from somewhere - either the high atmosphere must cool, or the solar radiation must have increased; or some similar planetary-scale energy exchange; but extra heat energy does not just appear from nowhere because our atmospheric composition has subtly changed. Nimur (talk) 15:53, 13 August 2009 (UTC)
Um what? I would say it's accurate to say the entire planet is getting warmer. You missed out a key point. The greenhouse effect means that without a change in incident solar radiation you can get a warmer planet, as less of the heat escapes. See also radiative forcing. I think it's mostly accurate to say Venus is quite a different temperature from Titan for reasons beyond the difference in incident solar radiation. As far as I'm aware a significant part of the energy we're referring to escapes to regions of space long beyond what we would normally call our atmosphere so I don't think it's accurate to say where just talking about a redistributions of heat from the high atmosphere to the low atmosphere and surface. P.S. This explaination is probably a little too simplistic and I'd welcome any improvements. I do agree more careful use of terminology may be wise. Nil Einne (talk) 18:39, 13 August 2009 (UTC)
And another nitpick, Nil Einne - with all due respect, you are doing exactly what I was talking about, with regard to Venus. You are conflating its surface temperature with its planetary temperature - when in fact, Venus' planetary temperature is lower than it should be, based on its proximity to the sun. Go explain that with the greenhouse effect! The surface temperature is extremely high - enough to melt lead - but the planet temperature is about 50 kelvins below the expected (Fraknoi et. al), NASA fact sheet. Nimur (talk) 19:43, 13 August 2009 (UTC)
A hotter planet radiates energy faster - not just faster, A LOT FASTER, with tiny perturbations resulting in huge radiative cooling changes - , via radiational cooling. As far as I am aware, no such change in the blackbody spectrum of Earth has been observed, ever. When we see a hotter ocean, it means that somewhere else, something is cooling faster to dissipate that energy - take a look at this 2003 NASA news brief - ""Extreme cold is required to form ice in a dry environment like the mesosphere," says Thomas. Ironically, global warming helps. While greenhouse gases warm Earth's surface, they actually lower temperatures in the high atmosphere. " (To be fair, this statement and many like it were the subject of fierce academic debate, and appeared in an EOS journal release which I am currently looking for...) Nimur (talk) 19:32, 13 August 2009 (UTC)
Found it - Are Noctilucent Clouds Truly a "Miner's Canary" for Global Change? - EOS vol. 84, #28, July 2003. Nimur (talk) 19:36, 13 August 2009 (UTC)
Your premise that incident solar radiation needs to change (presumably increase) for the planet to get warmer is false. -- (talk) 17:08, 15 August 2009 (UTC)
Sez who? You got any proof of that? (talk) 06:33, 16 August 2009 (UTC)
Nimur is probably right in saying that the "entire planet" isn't getting warmer...including the whole body of the planet rather than just the surface, oceans and atmosphere that is. However, that's really something of a nit-pick. To all of us humans, the plants and animals and everything else we care about - the temperature of the top couple of feet of soil, the water and the air are really all we care about. The temperature of all of the things we care about is increasing - and that's what matters. Use of the word "global" is commonly taken to mean "just the surface stuff". When we talk about a "global flu pandemic" - we don't seriously imagine that there is a flu outbreak at the center of the earth. When we say there is a "global recession" - we don't mean that there are banks going out of business at the center of the earth. So "global warming" is a perfectly cromulant with it! SteveBaker (talk) 00:26, 14 August 2009 (UTC)
It's not only about terminology - it's instructive and helps conceptualize the problem when you realize that what is actually happening is a redistribution of the energy in our atmosphere, and the consequences that follow are changes in weather patterns. Nimur (talk) 14:32, 14 August 2009 (UTC)

August 13

Insane Plants

I am researching plants. Specifically plants with some exciting or dreadful, indeed, insane aspects to them. I have covered the corpse flower and things like henbane and datura and am looking to see if anyone can point me to some more. (talk) 00:05, 13 August 2009 (UTC)

Well I am very fond of all carnivorous plants. Plants that eat animals... insane! -- (talk) 00:14, 13 August 2009 (UTC)
"Mad cucumber" Ecballium elaterium is fun :) --Dr Dima (talk) 00:16, 13 August 2009 (UTC)
Those are much more interesting than their stub article would suggest. There are a lot of videos of them if you look on YouTube for "exploding cucumber" and things like that. They don't just release their seeds in a way that can be "seen by the naked eye," they apparently shoot them out quite violently... [9] In general, the Rapid plant movement plants are pretty neat. -- (talk) 00:36, 13 August 2009 (UTC)
How about the mandrake, 'sprouted from the death-ejected sperm of a hanged man'? Adambrowne666 (talk) 00:44, 13 August 2009 (UTC)
Mandrake (plant) aka Jihn's eggs = fun indeed. --Dr Dima (talk) 00:47, 13 August 2009 (UTC)
In the "not so fun" category you can try Castor oil plant, curare vines (Abuta, Chondrodendron, also Strychnos) - all very poisonous. Try also cholla cactus, it's just nasty :) --Dr Dima (talk) 00:51, 13 August 2009 (UTC)
There is also sensitive plant, which closes its leaflets when disturbed.CalamusFortis 03:18, 13 August 2009 (UTC)
You might consider the plants depicted and described by Leo Lionni in his book Parallel Botany, the contemplation of which might well cause the contemplatee some mental distress. (talk) 03:29, 13 August 2009 (UTC)
Weird: Lithops, Resurrection fern, Wollemia, Welwitschia, Rafflesia arnoldii, Wolffia. --Sean 17:43, 13 August 2009 (UTC)
Catnip? It has mind-control over cats :) -- (talk) 16:21, 14 August 2009 (UTC)
Dunno - "control" isn't the word that comes immediately to mind when you see a cat tripping-out on catnip. SteveBaker (talk) 02:34, 15 August 2009 (UTC)

Why are some dishes so greasy?

Most oily dishes can be washed easily with soap, but some require dishwashing fluids. What's the diff? (talk) 00:20, 13 August 2009 (UTC)

Probably the composition of fat. Some fats solidify at room temperature, some don't. See Fat and saturated fatty acids. --Dr Dima (talk) 00:27, 13 August 2009 (UTC)
You wash dishes with soap? Unless you guys use the word soap to mean some sort of dish soap, but I only use soap for my hands and in the shower. Everyone I know uses some sort of dishwashing liquid in the kitchen sink. Vespine (talk) 02:03, 13 August 2009 (UTC)
In the USA, where the IP is from, we call dish soap "soap." A different kind of soap, but as you say, soap nonetheless. There are even kinds sold that claim to function as both dish and hand soap. ~ Amory (usertalkcontribs) 04:48, 13 August 2009 (UTC)
There is also no good reason why you couldn't use dish soap in the shower in a pinch. It just takes a lot more water then normal soap for it to stop making suds. Googlemeister (talk) 13:45, 13 August 2009 (UTC)
I imagine some use mere surfactant effects, emulsifying oils and water, while stronger liquids might directly attack lipids. John Riemann Soong (talk) 08:46, 13 August 2009 (UTC)
To the best of my knowledge, all dishwashing liquids use surfactant effect and do not "directly attack lipids". You want something to "directly attack lipids", try baking soda or sodium carbonate (powdered "detergent" for dishwashing machines), or even Drano (though this last option could be dangerous for washing dishes). (talk) 04:27, 16 August 2009 (UTC)

Hideous mermaid image

Ages ago, I found on the internet a black and white illustration, possibly an engraving, of a skrinkled up little corpse of a purported mermaid - not the Feejee Mermaid, but one less human, more ghastly. I wanted to use it on the cover page of something I'm writing, but foolishly I seem to have deleted it from my files. Can anyone find it for me? (I'm thinking now it may not have been a mermaid after all, but just some random scientific curiosity from a wunderkammer somewhere).

Thanks in advance.

Adambrowne666 (talk) 00:41, 13 August 2009 (UTC)

A shrinkled up little corpse that’s more ghastly than the Fiji mermaid? That looks like a pretty ghastly shrinkled up little corpse to me. Red Act (talk) 00:56, 13 August 2009 (UTC)
It's plenty skrinkled up, let me tell you. Adambrowne666 (talk) 01:01, 13 August 2009 (UTC)
There is [this], but it's probably not what you're looking for. I'm pretty sure that this is the FeeJee Mermaid before it became known by that name. It's uglier than the usual drawing, though. APL (talk) 01:39, 13 August 2009 (UTC)
Thanks, APL, but yeah, not what I'm looking for - my uncertain memory tells me there wasn't much of a face at all, and if it was engraved, it was finer work, darker in hue. I think it predates the Feejee Mermaid by at least a century. Sorry, I realise how unlikely it is for this question to be answered. Adambrowne666 (talk) 02:25, 13 August 2009 (UTC)
What about this little lady? LANTZYTALK 06:52, 13 August 2009 (UTC)
I'm starting to feel like an ingrate - everyone's been v generous, and here I am just saying no no no; so, sorry, Antzy, but no; that's another incarnation of the Feejee Mermaid Adambrowne666 (talk) 08:54, 13 August 2009 (UTC)
It's frustrating. I'm sure I've seen woodcuts of dead alleged mermaids before that weren't the FeeJee mermaid, but I have no idea where I've seen them. APL (talk) 13:41, 13 August 2009 (UTC)
Jenny Haniver

May I introfduce you to Jenny Haniver? Perhaps not in thr Littlr Mermaid class nor yet in that of Wonder Woman, but let's not ne picky. B00P (talk) 07:35, 14 August 2009 (UTC)

This really doesn't match your description exactly, but it is what I immediately thought of. I remembered reading about a "hoax mermaid" that had purportedly washed up on a beach: The link is on page three of four, the first page is an article discussing the hoax itself. Maedin\talk 19:39, 14 August 2009 (UTC)

Thanks heaps, all, for your tireless attempts - I'll likely use one of the better Feejee Mermaids if I can't find the one I'm thinking of. In the meantime, though, I'm gonna try the Humanities Desk. Thanks again Adambrowne666 (talk) 02:30, 16 August 2009 (UTC)

Ice Age

Does ice Age happen once every certain amount of time or ice age is non-stoppable matter like Greenhouse effect. Does Ice Age go away after certain time, or it is accumulative like global warming?-- (talk) 02:55, 13 August 2009 (UTC)

Have you read Ice age? You may also find Timeline of glaciation interesting. Global warming will go away after a certain time if we stop pumping extra greenhouse gases into the atmosphere, it might just take a long time and do a lot of damage along the way (especially if we trigger a runaway greenhouse effect as some people fear we are going to). --Tango (talk) 03:01, 13 August 2009 (UTC)
How do you know if "global warming" "will go away... if we stop pumping extra greenhouse gases into the atmosphere" -- will doing that change the amount of solar radiation reaching the Earth? And besides, what do you mean "we" will "trigger a runaway greenhouse effect"? In other words, what evidence do you have that "global warming" is caused by some so-called "greenhouse effect" and not by an increase in the amount of solar radiation? (talk) 04:34, 16 August 2009 (UTC)

neural optimization.. how to,..

hey friends,

i have obtained 10 straight lines as solution of a 10 differential equations say u=f(t)(t=time). i need to optimize u by varying to go for it in matlab tool box. (talk) —Preceding undated comment added 07:37, 13 August 2009 (UTC).

CVX: Matlab Software for Disciplined Convex Programming is the standard around these parts. You might also find LSQR useful. I believe LSQR is now included with MATLAB. Nimur (talk) 19:49, 13 August 2009 (UTC)

Moon at 100 km

What would happen if tomorrow the moon just appeared in a new, circular orbit, where it skirted the atmosphere through the length of the journey? (I know the moon is actually retreating and this couldn't really happen but I'm curious about the possible consequences). How long would it take for atmospheric drag to bring its path into contact with the surface? TheFutureAwaits (talk) 09:53, 13 August 2009 (UTC)

Tidal forces would likely disrupt the moon into a ring. The earth also would be seriously damaged by tidal forces. Graeme Bartlett (talk) 09:57, 13 August 2009 (UTC)
A ring like a planetary ring? —Akrabbimtalk 12:47, 13 August 2009 (UTC)
Yes, as a planetary ring. 100 km is well within Earth's Roche limit. Interestingly, the Earth would also lie within the Moon's Roche limit (which is about 120 km above the lunar surface) -- so yes, Graeme Bartlett is entirely correct that damage to the Earth, from tidal forces alone, would be incredibly severe. I would guess you're talking damage on the order of liquifying most of the surface, even before impact. A wild-ass guess puts time to collisions starting within a week, but not finishing for years, due to the Moon being ripped to shreds (some portions of the moon would be 1800 km up and well above most of the atmosphere). — Lomn 12:57, 13 August 2009 (UTC)
Whaaat, you mean The Distance of the Moon didn't really happen...? (talk) 13:19, 13 August 2009 (UTC)
Very low earth orbits, like a 100 km altitude, usually suffer from air drag, and decay rapidly (within weeks or months, depending on characteristics of the object. Nimur (talk) 15:59, 13 August 2009 (UTC)
Yes ... but bear in mind that the Moon is much larger than your average (artificial) satellite, most of it is outside of the atmosphere, and it has an awful lot of momentum. As far as atmospheric drag is concerned, this would dump so much energy into the atmosphere that it would probably strip off most of the atmosphere before it had any appreciable effect on the Moon. But as other contributors have pointed out, tidal forces will rip the Moon apart long before that happens. Gandalf61 (talk) 16:28, 13 August 2009 (UTC)
Yes, I don't think the atmosphere would last more than a few hours, a couple of days at most, although some of it might be replaced by the water and even rock on both the Earth and Moon vaporising. The Roche limit doesn't really apply to objects as rigid as the Earth and Moon, but it gives a good idea of how close you can get before you start to have problems. Anything not tied down is in trouble! --Tango (talk) 16:40, 13 August 2009 (UTC)
Why doesn't the Roche limit apply? I thought it applies exactly for such a situation - the tidal forces are so overwhelmingly strong that they outweigh the gravitational self-attraction of the constituent materials of the moon. The only reason the moon is "rigid" is because gravitational energy was sufficiently strong to fuse the rocks together (i.e. by melting) - but the Roche limit defines the point where that effect is smaller than the tidal shear force. Needless to say, we don't have a lot of empirical examples for comparison; bt I think the principle applies, and the moon would fracture. Just figure that the orbital period at 100 km should be about one or two hours; while at the far side of the moon (100km + moon diameter), the stable orbital period would be some factor slower (10x? I'm too lazy to do a back of the envelope calculation). Whatever that differential in speed is would be shearing the moon apart. Nimur (talk) 17:12, 13 August 2009 (UTC)
Now those rocks have fused they would continue to be held together even if gravity disappeared. The moon (and much of the Earth) would indeed be ripped apart, but you can't simply look at the Roche limit. Read the second paragraph of Roche limit. --Tango (talk) 17:18, 13 August 2009 (UTC)
Frankly, I think our second para of Roche limit looks pretty weak. There's no cite on its claims (of the anomalous moons being held together by non-grav forces), and Metis (moon) (one of the supposed Roche-defying bodies) cites the moon's continued integrity as evidence that it's outside the Roche limit. Since the RL is density-dependent, an orbital radius that turned one moon into a ring system may leave another intact. Additionally the selected examples subsection of RL notes both anomalous moons as orbiting outside the rigid Roche limits, and a great many moons orbiting inside the fluid limits. That said, I'm no expert in this field. — Lomn 18:34, 13 August 2009 (UTC)
(outdent) - I disagree that melting a rock gives it a stronger bond than the gravity which provided the source energy for the melting and physical bonding to form. I'll try to find some sources and edit Roche limit - but I'm pretty sure that conservation of energy is at play here - the rock can not be held together by a binding energy stronger than the gravity which initially bound it (unless it started out molten - but this is not widely supported by the accretion theory - the rock should have started off cool, and only melts due to gravitational compression heating). Nimur (talk) 19:16, 13 August 2009 (UTC)
I think somebody owes Steve a dollar. We're not talking about energy, we are talking about force, they are very different (albeit related) things. When physical bonding has taken place that is going to mean it can survive some force pulling it apart, that means the tidal forces will have to cancel out gravity and then pull apart the bonds, that is going to take greater force that just cancelling out gravity, which is all that would be required to pull apart a pile of rubble (a lot of these kind of calculations are based on the moons/asteroids being piles of rubble, as many smaller ones are). --Tango (talk) 21:06, 13 August 2009 (UTC)
I don't think I owe Steve a dollar. I'm simply stating that a force can't be stronger than the energy gradient which creates it. That's the definition of a force, , where U is a potential energy field. In this case, U is gravitational energy. The rock can only melt and "fuse together" if the force due to gravity is sufficiently strong to melt it - there's no other source of energy (or force, or anything). Nimur (talk) 21:38, 13 August 2009 (UTC)
I never said the force was stronger than gravity, it is in addition to gravity so the total is, of course, greater. --Tango (talk) 22:20, 13 August 2009 (UTC)

Interesting answers guys! I'm currently writing a sci-fiction story about this situation and appreciate all your insight! (Essentially aliens slow the orbit of the moon to force it into an extremely low orbit)So what would this all be like for a person on the surface? Would they feel themselves being pulled in the direction of the moon? Could they jump higher? How big would it look? What would happen if you woke up one day, walked outside and the moon was 100 km away? TheFutureAwaits (talk) 19:13, 13 August 2009 (UTC)

Given that we've been discussing how quickly the Moon would render the Earth entirely uninhabitable at that distance, and how the Earth would rip the Moon entirely to shreds, this is all moot. You can easily calculate the Moon's angular diameter at 100 km altitude and subtract the relevant surface gravities if you like, but I won't imply that any of this is what it "would be like for a person on the surface". By this point, either the Moon would already be gone (per the Earth's Roche limit, if aliens move the moon), or the Earth would be uninhabitable (per the Moon's Roche limit, if aliens teleport the moon). Either way, rocks fall, everyone dies. — Lomn 19:54, 13 August 2009 (UTC)
Yeah, but you have about three days to prevent complete disaster at that point. —Akrabbimtalk 20:26, 13 August 2009 (UTC)
If aliens want to kill everyone, there are a lot better ways then to move an object the size of the moon. Heck a couple of well placed nukes and we would more likely do it ourselves with our own equipment. Googlemeister (talk) 20:29, 13 August 2009 (UTC)
A "couple of well-placed nukes" could kill maybe about twenty million people, but won't "kill everyone" -- you'd have to start an all-out nuclear war between Russia and the US for that to happen. (talk) 05:20, 16 August 2009 (UTC)
A couple of well placed nukes WOULD start an all out nuclear exchange between Russia and the US in all likelyhood. Googlemeister (talk) 15:10, 17 August 2009 (UTC)
Not if they're traced to someone else, like Iran or Pakistan (yes, there are ways to trace a nuke back to its manufacturer even after it's gone off). It would have to be done very soon after the explosion, but it can be done. (See the novel The Sum of All Fears by Tom Clancy.) (talk) 22:53, 17 August 2009 (UTC)
I think you need to understand the concept of tidal forces a little better. If the moon were to get that close - the force of gravity due to the earth on the side of the moon nearest to the earth would be enormously larger than on the side furthest from the earth. Moreover, the side of the moon furthest from the earth is travelling around in a circle with a much greater diameter than the side closest to the earth - and that adds to the centrifugal force that it experiences. The result is that the moon is being pulled apart by gravity on the one side and centrifugal force on the other. At some point, (The "Roche limit") the pulling and tearing forces become greater than the structural strength of the moon - and it simply flies apart. When that happens, each individual little rock flies off into it's own orbit - but their mutual gravitation flattens that orbit into a disk. So long before the moon got as low as you are suggesting, it would have disintegrated - turning Earth into a mini-Saturn. As others have pointed out, the reverse is also the case - the Earth is obviously affected by tidal forces of the moon (if you leave on a beach, you'll notice this!) - and at the altitude you specify, the earth would also be beyond the roche limit of the moon - so both bodies would simply fly apart at that separation. Eventually, all of the pieces would fall back together making a single new planet...which would likely retain a ring system for a few centuries before all of the debris either collected to make a new moon - or fell back onto the newly formed planet. But if the moon were nudged gradually closer rather than magically teleported to that distance, it would simply start to disintegrate long before it got as close as you suggest.
From the point of view of science fiction - you can go two ways with it. Either the universe doesn't work the way we think - and (essentially) the aliens can use magic to slow down the moon and stop it from breaking up - and give you the story you want regardless of mere scientific niceties...or you're trying to write a reasonably scientifically plausible story. If it's the former - then just say that the aliens use a force field to hold the moon together and ignore what everyone here is saying. If it's the latter than ask yourself about aliens with the power at hand to slow down 7x1022kg of moon by something close to a kilometer per second - that's an INSANE amount of energy. If they have that much energy at hand, wouldn't it be simpler just to pick up a couple of mountain-sized asteroids and slam them into the earth? The effect on life would be about the same...and the energy requirements would be microscopic in comparison. It just doesn't make sense that they'd do that. SteveBaker (talk) 22:48, 13 August 2009 (UTC)
I doubt the Earth would be completely ripped apart. It would be only just inside the Roche limit and has significant tensile strength, so I'm fairly sure it would survive, but the damage would be enormous. The atmosphere and oceans would be in trouble - they have essentially no tensile strength and are right on the edge of the Earth, so would be ripped away, the Earth's core, on the other hand, would be far enough away from the Moon and it is held together quite strongly so would remain intact, as would most of the mantle, probably all of it and most of the crust. --Tango (talk) 23:25, 13 August 2009 (UTC)
Oh - just all of the oceans, atmosphere and the first few kilometers of dirt and rock....well, that's OK then! I can't imagine what I was worried about! :-) SteveBaker (talk) 00:15, 14 August 2009 (UTC)

First, remember than an object in a lower orbit moves faster than one in a higher orbit. So to move an object from a high orbit into a lower one, you don't just "slow it down". If a force is applied over an extended time in a direction that slows the object's motion, it will gradually move into a lower orbit but it will actually be moving faster all the time, as its potential energy gets converted to kinetic energy. This is the way satellites behave when their orbit decays due to atmospheric drag, for instance. (For simplicity I assume we are talking about orbits that are circular or pretty nearly so.) With a suitable power source, the Moon could be lowered into a low orbit this way over a period of months or years.

The other way to move an object into a lower orbit -- the way it would be done with today's rockets -- is to start by applying a stronger force in the direction that slows its motion. Its speed will become lower, but it will now be at the high end (apogee) of an elliptical transfer orbit. As the satellite falls closer to the primary (the Earth), its speed increases. When it reaches the low end of the orbit (perigee), you again apply a force to slow it down, and this converts the orbit to a circular one. (The important thing to remember is that when no external force is being applied, the orbit always passes through the last place where a force was applied. So to change to an orbit that does not intersect the original one, you need to apply force twice.) By this method the Moon could be lowered into a low orbit over a period of a couple of days.

With a still stronger force, it could be done even faster, but then the transfer orbit would have to be hyperbolic -- without the second application of force to put the Moon back into orbit, it would escape the Earth's gravity altogether.

If you're talking about the Moon being teleported rather than accelerated into the new orbit, then it's not being slowed down. It's being placed in a new position and given a suitable higher speed that will put it in circular orbit, although it will have less potential energy than before.

At 100 km above the Earth's surface, the center-to-center distance is 1,738 + 6,378 - 100 = 8,016 km. The normal distance varies from 363,100 to 405,700 km, so let us say it would be 1/48 as much. So the first thing is that the Moon would look 48 times as wide as it does now.

Next, the period of the Moon's orbit would be greatly reduced according to Kepler's Third Law. It would be to sqrt(1/48³) power of what it is now, or about 2 hours. As seen from a given location, there would be a Moonrise or Moonset every hour or so. In latitudes near enough to the equator, the much larger Moon would eclipse the Sun 6 times a day, but they would not be like the eclipses we know now where the Sun is just barely covered and the Moon's motion in front of it is slow. The Moon would blank out the Sun in less than a minute, and would in many cases cover the whole corona, but within a few minutes it would equally rapidly move clear of the whole sun again, returning daylight to normal.

The Moon would also be in total eclipse most of the time it was above the ground at night; it would only shine brightly when close to the horizon.

Now the tides. Tidal force varies as the inverse cube of the distance, so it would be about 48³ = about 110,000 times normal! This is still not enough to disrupt the solid Earth, but it's plenty to tickle some seismic faults and trigger some of those earthquakes that are expected "sometime in the next hundred years". More important, effects on the sea would be huge -- coastal lowlands throughout the world might become wholly or partly uninhabitable due to high tides, and that includes major cities such as Los Angeles, New York, Rio de Janeiro, London, Mumbai, Tokyo, Sydney, and many, many more throughout the world's seacosts. It's hard to estimate how high the tides would be since they would come once an hour instead of every 12+ hours, and the patterns of motion would be different than today. But they would certainly be big.

And the atmosphere would be similarly disrupted -- it feels tides too -- although it's hard to say what the effect would be. Violent weather seems a likely bet, though.

All this is true as long as the Moon stays more or less in one piece. The Earth's tidal force on the Moon, which is much stronger than the Moon's tidal force on the Earth, would also be 110,000 times stronger than normal, and stronger than the Moon's own gravity -- that's what "being inside the Roche limit" means. So maybe the Moon would break up under the stress and form a ring around the Earth. That depends on its tensile strength and I won't attempt to calculate whether it's likely. Dust and loose objects on the Moon's surface, like the Apollo landers, would float free of it, in any case, and enter orbit independently.

Finally, note that the Moon rotates once per month and unless something was deliberately done to change this, it would continue to be true in its new orbit. Consequently it would no longer always have the same face turned towards the Earth, but would look noticeably different from one Moonrise to the next.

--Anonymous, 22:01 UTC, August 13, 2009.

The Moon would be so far inside the Roche limit that I would be very surprised if the tensile strength was enough to save it. You also having taken atmospheric drag into account - there is still quite a lot of atmosphere at 100km, maybe not enough to slow the Moon down considerably, but plenty to cause some considerable heating. --Tango (talk) 22:42, 13 August 2009 (UTC)

I just wan't to point out that the RL calculation assumes that the orbiting body is much smaller than the other one. Because of that, all statements above mentioning the fact that the earth would be within the moon's RL are nonsense. Pieces of the earth would not fly upwards. The moon, on the other hand, would be destroyed as pointed out. Dauto (talk) 23:51, 13 August 2009 (UTC)

I'm just going to go out on a limb and suggest that Roche-limit-related fracturing would be most likely moot, because at 100 km, I suspect the moon would simply collide with the earth due to orbital instability and amplifying perturbations from circular orbit; after collision, we've got a whole new mess of non-ideal, non-rigid-body mechanics to deal with. I think we're all in consensus about the catastrophic nature of this scenario, one way or the other. Nimur (talk) 01:07, 14 August 2009 (UTC)
Just one thing Nimur. A quick search of Wolframreveals... The Roche Limit is the point where a body with no tensile strength would be torn apart. As people say this wouldn't tear apart the Earth because it has tensile strenght. A real body can pass the Roche limit of the planet its orbiting without being torn apart. From what76.94.88.196 (talk) 06:36, 14 August 2009 (UTC)
Ok, I suppose I might have been somewhat incorrect in the definition (by assuming that tensile strength was accounted for); apologies to Tango and others for my adamant statements earlier. Nimur (talk) 14:40, 14 August 2009 (UTC)

While we're hypothesizing...

One question that came up in my mind hasn't been addressed. (I haven't read any of the referenced pages, by the way.) As a moon-sized object in a decaying orbit starts to hit upper atmosphere, would the friction on one side of said moon be enough to start it revolving on an axis again?

Think of the tires on a landing aircraft. They get up to speed pretty quickly from friction with the runway, which is only on one side of the tire. Is there enough friction present in the low-orbiting-moon scenario to cause the same effect, or to override whatever force has stopped the moon from revolving in the first place?

Further unrealistic assumptions about breaking up in orbit may be necessary :-) --DaHorsesMouth (talk) 22:35, 14 August 2009 (UTC)

I suspect the answer is "yes", but I should point out that the Moon is revolving on its axis now, it's just revolving at the same rate it is orbiting, so we always see the same face. Its orbit and revolution become locked like that due to tidal forces, it's called tidal locking. --Tango (talk) 00:40, 15 August 2009 (UTC)

CPU gold content

Who can tell me an approximate quantity of gold and other noble metals in various CPU? Renaldas Kanarskas (talk) 10:57, 13 August 2009 (UTC)

Googling "how much gold in a computer" comes up with a number of links to suggest that there are very small amounts of gold in a computer, in the form of gold plating, which is not very much gold. One thread suggests that "One ton (2000 lbs) of "average" circuit board from modern computers and electronics generally yields (in a very good system) between 8 and 11 troy ounces of 24k gold." There is much more silver, and minute amounts of everything else. [10] -- (talk) 13:47, 13 August 2009 (UTC)
It really comes in two places - some of the pins of some of the connectors are coated with a microscopically thin layer of gold - and inside the actual chips themselves, incredibly thin gold wires are sometimes used to connect the edges of the silicon wafer to the pins of the chip that lead out onto the circuit board. In both cases, the amount of gold is incredibly small. It's also exceedingly difficult to extract on any commercial scale because it's mixed up with all manner of other weird and wonderful metals. But look at it like this: We can now make low-cost net-books for $100 to $200. With gold costing $950 an ounce - if there was any significant amount of gold in there - they'd cost a lot more! Manufacturers are not obsessing about the amount that the gold in these machines is costing them - so we may conclude that it's negligable. SteveBaker (talk) 14:03, 13 August 2009 (UTC)
AFAIK there will be no gold actually in the CPU - i.e. the inside the chip compartment. In the "olden" days gold was indeed used for bond wires, and occasionally even for "wiring" on the chip. However, this is no longer the case and aluminium based bond wires and chip wiring have been the norm for a while. Gold is generally a bad thing for silicon chips, since it causes recombination centres which shorten minority carrier lifetimes, so it's pretty common to avoid it at all costs. --Phil Holmes (talk) 14:07, 13 August 2009 (UTC)
On the other hand, older computers and electronics (1970's) had quite a bit of gold, mostly because the technology to apply very thin conisitent coatting was not available, so the coating on the connectors was much thicker. Also, since the individual chips were much less integegrated, there were proportionally more wires and connectors. -Arch dude (talk) 17:24, 13 August 2009 (UTC)

Are cats really this clever? Was this just coincidence or are cats really this clever? The cat would have needed to have gone through quite a long chain of thought, and be capable of altruism, to have purposedly done this. Is it more like to be merely coincidence, since many fires occur in which cats do nothing. (talk) 12:09, 13 August 2009 (UTC)

Cats are clever enough routinely to hassle humans when they want some change in the environment: the production of food, the opening of a door, &c. It's not a very great stretch between such commonplaces and the event described. --Tagishsimon (talk) 12:14, 13 August 2009 (UTC)
If the story happened exactly as presented it would be a remarkable story. But the detail that makes it remarkable seems completely unverifiable. How does the author know that the cat entered a burning building? (Did a human observe the cat enter the burning building? If so, why didn't the human raise the alarm?) If the cat was already sleeping in the building when it caught fire it's not hard to believe that it would seek out a human to deal with the issue.
There have been other cases[11][12] of cats waking their owners in fires. All of these involve cats that were already in the house. If Hugo really entered the building after it had caught on fire as the article suggests, that would be really impressive.
While the cat was certainly a hero, I'd be surprised if that was its primary intention. Too me, it seems far more likely that the cat perceived that the house had a serious problem and he wanted it fixed immediately for his own sake. APL (talk) 13:29, 13 August 2009 (UTC)
There are stories of dogs doing this kind of thing too - but in their case, it's more likely because they are pack animals. But I agree, the only remarkable thing is that the cat supposedly re-entered the building after it caught fire - and that's a completely unverifiable detail. However, if you Google "cat enters burning building" - you get 100,000 hits - it's a common meme that a mother cat will re-enter a burning building multiple times to bring out her kittens, so there may be basis in fact. SteveBaker (talk) 13:52, 13 August 2009 (UTC)
I've certainly seen a mother cat making multiple trips to move kittens away from something she considered dangerous (me and my friend who were playing with the kittens on top of the bed they were living under!), so I can't see why she wouldn't have done the same in the case of fire. --Tango (talk) 16:45, 13 August 2009 (UTC)

non-therapy ancillary services

In medicine, what does the term "non-therapy ancillary services" refer to? This is included in the House healthcare bill (HR 3200) page 230 and other places. (talk) 12:29, 13 August 2009 (UTC)

Respite care, financial aid, home help, assistance with transportation etc. Caring for the non-medical needs of ill patients. Fribbler (talk) 12:34, 13 August 2009 (UTC)

Quantum mechanics and determinism

Please excuse the probable ignorance displayed in my asking this question, as I have only a poorly informed lay understanding of how quantum stuff works- but I guess if I knew it all I wouldn't have to ask questions about it!

I was wondering about whether quantum physics and the uncertainty principle actually preclude the possibility of a deterministic classical Universe even at the smallest scale. I was reading A Brief History of Time, and Hawking commented that if anything did happen before the Big Bang (like a previous Universe or something) it could have no observational consequences for this Universe so science could not speculate about it even if it wanted to. I was wondering if this was parallelled in the uncertainty principle- is there a possibility of particles having an exact speed and position, but because they could never be observed science cannot speculate about them?

Basically my question is: is quantum mechanics a definition of the boundaries of what is knowable about the Universe, or does it actually preclude the existence of anything certain? And if so, how?

Thanks much, Dan Hartas (talk) 12:31, 13 August 2009 (UTC)

Quantum theory certainly precludes perfect determinism at the smallest scales. If you take a single atom of Uranium-232, you have literally no way to determine when it will decay into an atom of Thorium. You can say that there is a 50/50 chance that it'll have decayed within the half-life of U232 (68.9 years) - but if you come back 7 years or 70 years later and discover that it hasn't decayed yet - then ask the same question, the answer doesn't change - it's still a 50/50 chance that it'll decay in the NEXT 68.9 years! The atom doesn't have a 'clock' inside telling it when to decay - and it doesn't get worn down with time and become 'ready' to's just completely random. But as you work at higher scales, that randomness generally averages out so at the scale of humans, things seem pretty deterministic. If you take a bucketful of Uranium-232 (which is probably a bad idea!), you know with absolute certainty that half of it will have decayed into Thorium after precisely 68.9 years. However, since some things are "chaotic" (in the mathematical sense of being highly sensitive to small things) - it is true to say that quantum level indeterminism does have an effect at the 'macro' scale. To pick the commonest example of the weather - which is "chaotic" - we've all heard that the beat of a butterflies wing could cause a tornado halfway around the planet years later...well, the decay of a single atom of uranium could cause changes on a similar quantum randomness can indeed drive extremely unstable macro-scale things like weather patterns.
However, the issue of there being no information from before the big bang is a different matter entirely. Because the universe appears to have started as a 'singularity' (an infinitesimal dot - a point with zero size), then there is very little information content possible within it. Particles don't exist, there are no velocities, positions, nothing like that. The point may have mass - but that might be infinite, so there isn't any information there either. In an information-theory sense, there is no place for the information about what happened "before" to be stored. Of course Hawking claimed that there was no "before".
I suppose that since the singularity was so small, it would be affected by quantum theory indeterminism - so for the very first few picoseconds of the big bang, it might also have been ruled by things like the uncertainty principle - meaning that any information that had passed into our universe from whatever came before would be totally scrambled anyway...but that's not a necessary precondition. The mere fact that it was a singularity sharply limits the amount of information it could possibly contain...and that's enough to ensure that we can't directly observe what came before. However, even the existance of a "before" is somewhat contentious. It's arguable that time itself was started by the big bang and even the concept of a "before" is meaningless. That would be a somewhat beautiful conclusion because it cuts off the need to go into this infinite regress of asking what created the big bang...then what created the thing that created the big bang...and so on. If time started at the instant of the big bang then we have the complete "creation story" nailed down already.
SteveBaker (talk) 13:30, 13 August 2009 (UTC)
So if you take 2 U232 atoms and wait one half life, is one of them going to be Thorium and the other U232 or could they both be one or the other? Googlemeister (talk) 13:40, 13 August 2009 (UTC)
The configuration would have the same probability distribution as flipping two coins, substituting "heads" with "does not decay / uranium" and "tails" with "decays / thorium" (assuming the thorium hasn't itself decayed). 25% chance of no decay, 25% chance of total decay, and 50% chance of partial decay. — Lomn 13:44, 13 August 2009 (UTC)

Our article on Hidden variable theory deals directly with the OP's question, although it is written at a level that may present difficulties for somebody without much physics background. Looie496 (talk) 15:32, 13 August 2009 (UTC)

We need to be clear though that only a minority of physicists really support hidden variable theory - and even then, only one particular flavor of it (Bohm theory) is really acceptable since it's the only one that agrees with conventional indeterministic quantum theory and experimental evidence. This addresses the OP's question - but it's not a solid answer. Since Bohm theory doesn't exhibit the property of 'locality' - this interpretation poses problems that are exactly as bad as indeterminism in practice - they just give you the warm, fuzzy feeling that at it's heart, the universe isn't random - it simply behaves precisely as if it were totally random! SteveBaker (talk) 21:56, 13 August 2009 (UTC)
The universe described by Quantum Mechanics is completely deterministic, however, from the point of view of an observer within the universe, the outcome of an event can be completely non-deterministic, without even a theoretic possibility of predicting an outcome. To see how this is the case, consider the following thought experiment: I challenge you to predict the outcome of a random event, in this case flipping a coin. It is my contention that I will win our challenge at least some of the time because you are unable to predict the outcome of the random event. What I haven't taken into account is that you have a special power of knowing the current state of every particle in the universe. Since all you have to do is measure the exact position of the coin and all the variables that contribute to the flipping motion (the state of my hand muscles, the coins weight, air resistance, etc.), you will win the challenge every time. The question is, how can I possibly regain my ability to win the challenge given your remarkable super abilities? If I utilize the principles of quantum mechanics, I can do it like so: when flipping the coin, I actually create two copies of it, one that lands on heads and the other that lands on tails. At the same time, I am creating two copies of you, and the two copies will see different results for the coin flip. There is no point in asking which coin landed on which side; since else everything except the coin state is identical, which one is which is completely arbitrary. In addition, I'll add the constraint that you can't communicate with your parallel self copy in any way; once you get copied you go along after that completely independently. Now, in this scenario, you will always see the coin flip as being a completely random event. There is no way, even in principle, to know which side you will see come up, because you cannot "choose" which copy of yourself becomes "you"; "you" are observing both possible scenarios in separated lines of causality, but each copy of you assumes that his version of events is actually what happened. Your complete knowledge of the state of every particle in the universe still stands; you knew with 100% certainty that I was going to make a copy of the coin and of you the moment before I did it, so the situation is completely deterministic (and might still appear completely deterministic from the perspective of a godlike observer who could "see" both outcomes happening), but as an actor who is made up of the same particles in the universe as the coin is made of, the randomness of the event is absolute. Truthforitsownsake (talk) 03:32, 14 August 2009 (UTC)
But if absolutely everything is deterministic, how do you create two copies that will see different results for the coin flip ? If the two copies start out identical (as they presumably are if they are faithful copies) and everything is deterministic then they evolve identically and so they see identical results for the coin flip. And if you reverse the coin in one copy and not in the other then you have created a non-determinsitic discontinuity in the history of one copy, and I can tell whether I am in the "true" copy or the "reversed" copy. Gandalf61 (talk) 13:03, 14 August 2009 (UTC)
The fact that I am holding a quantum coin and not a classical one is what enables me to create two copies with different results deterministically. I am not reversing the coin in one copy and leaving it alone in another; before I flip the coin, it is in neither the heads or tails flipped state because I haven't flipped it yet. After I flip the coin, it will always be in both the heads and tails flipped state. From your perspective before I flip the coin, you can determine that it will definitely be in both the heads and tails flipped state after I flip it, because my action of flipping it is already determined. The problem is that each copy of you after I flip the coin will see the opposite result state from the other, and see their result as a single canonical random observation. Of course, one cannot actually do such things with real coins since they are macroscopic; the coin in this example is just standing in for the state of a quantum particle. —Preceding unsigned comment added by Truthforitsownsake (talkcontribs) 14:21, 14 August 2009 (UTC)
Okay, so its a quantum coin, and you duplicate its wave function, which evolves identically in the two copies. Then in one copy I observe the coin and its wave function collapses into the state "heads" and in the other copy I observe the coin and its (identical) wave function collapses into the state "tails". So ... how exactly is that wave function collapse a deterministic process ? Gandalf61 (talk) 15:49, 14 August 2009 (UTC)
The wavefunction is never duplicated; there is only ever one. The wavefunction is what evolves deterministically in time, and it contains all the information about which states the coin (and you) will be in in the future. What you're calling a "collapse" is a shorthand way of referring to a particular configuration which will be in a part of the wavefunction at some point in time, but there is a corresponding other portion in which the opposite "collapse" configuration will occur as well. Truthforitsownsake (talk) 18:22, 14 August 2009 (UTC)
Are you talking about quantum entanglement ? Gandalf61 (talk) 20:04, 14 August 2009 (UTC)
I'm talking about whether it's possible to predict the outcome of a quantum event, even in principle. Truthforitsownsake (talk) 23:09, 14 August 2009 (UTC)


I am a retired American living in northeast Brazil where ant and termite invasions are a constant problem. In fact, no matter where I have lived (Michigan and Florida) ants have been an aggrevation. In Brazil, I recently bought an insecticide named "Ecoatta" that claims to be non-toxic and comes highly recommended here. Supposedly, it destroys the "queen" when the "workers" carry the poison back to the nest.

When I spray a small amount on a cluster of ants that are swarming a morsel of food that someone has inadvertently dropped on the floor or left on a table they only become agitated and disperse--perhaps back to their nest. Within a day or so, there are absolutely no signs of ants where before there had been. I am impressed and would like to know more about these products to recommend to family and friends in the U.S. but Google and other searches have not turned up anything useful. Perhaps you can help me find an equivalent product in the U.S. if one exists. If such a product is available, I believe it obsoletes the use of many conventional spray insecticides that typically line the shelves of our stores.

Specifics on the spray bottle:

Name: Eccoatta, non-toxic, "natural ingredients." Composition: Lactic acid 0.1%, Animal protein 0.12% Manufacurer: Empreendimentos Azuleida LTDA Contact:, ph 55-71-9987-7711

Thank You189.97.59.48 (talk) 13:20, 13 August 2009 (UTC)

Does it say anything else on the bottle - ie "active ingredients" ? Unless lactic acid is toxic to ants, which seems unlikely. (talk) 21:10, 13 August 2009 (UTC)
I believe it is actually named EcoAtta (eco for "eco friendly" and atta for "ant"). It is referred to here as being a Brazilian product. There are no other hits on Google for EcoAtta. Using other search engines, I found a bottle of EcoAtta for sale here. -- kainaw 22:24, 13 August 2009 (UTC)
Well some proteins can be potential toxins -- and they can also interfere with pheromone and hormone systems -- but perhaps the company doesn't want to disclose just what type of proteins it's using (for trade secret purposes). I'd be worried that if the proteins are too specific it'd be easy for colonies adapt via mutation though. John Riemann Soong (talk) 13:12, 14 August 2009 (UTC)
Besides, a venom that kills ants might not necessarily work against termites. FWiW (talk) 05:16, 16 August 2009 (UTC)

Influence of the Southern Oscillation on tropospheric temperature

Any thoughts on this, and any studies that you've found that you can cite which comment on it in anything other then glowing and fanatical words?

I haven't heard the supporters of global warming comment on it and I'd like to see if some have.

Thanks, Chris M. (talk) 17:18, 13 August 2009 (UTC)

It's to early for peer-reviewed comments to have made it through the system, but there are comments at RealClimate [13] and Open Mind [14]. In particular, the first author of the paper agrees that their methodology cannot detect a secular underlying trend [15]. Also see [16] for some more comments. --Stephan Schulz (talk) 18:26, 13 August 2009 (UTC)

Paper coffee cups and cold liquids

I have noticed that whenever I use a standard paper coffee cup for iced coffee, the cup almost immediately starts to go soggy, whereas with hot coffee, the same effect does not happen. I was curious about the reasons for this and have a suspicion though I might be way off base. Since these are wax impregnated (I believe), is it that the cold contracts the wax and thus causes it to flake or open up lots of seams such that the liquid then penetrates the paper, whereas hot liquid, though it could dissolve some of the wax (I wonder how much wax I eat a year in this manner) would do so uniformly, so it would not cause a fundamental breakdown of the water repelling properties of the wax so quickly? As I said, just hypothesizing.--Fuhghettaboutit (talk) 17:22, 13 August 2009 (UTC)

I never drink iced coffee from paper cups, but my guess is that the cups are only waxed on the inside, and that iced coffee causes condensation on the outside which soaks into the paper. Looie496 (talk) 18:08, 13 August 2009 (UTC)
I agree, that's what it looks like to me, too. The same will happen if you take a paper cup of ice-cooled soft drinks to a reasonably humid place (i.e. outside in Miami). --Stephan Schulz (talk) 18:50, 13 August 2009 (UTC)

What about Jerome Drexler and cosmology?

I see many references to Jerome Drexler and his theories about dark matter, dark energy, and relativistic particles, etc. What I find is that they are all written by Jerome Drexler himself, and they are often flogging his three books. I was hoping to find some objective discussion of his theories on Wikipedia, but he is not mentioned once. This leads me to believe is a wacko, but it would be helpful to find some objective evaluation somewhere, such as Wikipedia.

I have one theory and that is that Drexler himself has suppressed any discussion here because it would be unfavorable.

I would certainly appreciate your comments, and any pointers to an authoritative evaluation of Drexler and his theories.

JFistere (talk) 17:42, 13 August 2009 (UTC)

Google scholar doesn’t turn up one single paper by him on astronomy or cosmology in a peer reviewed source, which would be rather astonishing it was really true that he was such a genius that “No one else has plausibly explained these cosmic phenomena”[17] (five separate astronomy and cosmology topics). Sounds like just another nut job. Red Act (talk) 18:16, 13 August 2009 (UTC)
(edit conflict) Wikipedia articles require reliable sources, and it's hard to find any for him. He has no journal publications, his books are self-published, and using Google I haven't been able to find any reviews of his work in reputable places. So it seems that there isn't really any material available to use for a Wikipedia article. This is a relatively common situation with writers on "fringe" topics, unfortunately. It would be nice for Wikipedia to give the "real story", but we can't do it if there aren't any sources. (PS, I've found that it's better to avoid phrases like "nut job".) Looie496 (talk) 18:19, 13 August 2009 (UTC)
What term do you prefer? “Crackpot”? “Crank”? At any rate, we certainly don't need an article on a self-published crackpot. Red Act (talk) 18:45, 13 August 2009 (UTC)
I think it would be very difficult for Drexler to suppress an article about himself here on Wikipedia. If someone had created that article, he could vandalise it - maybe delete all of it's content even - but you'd still find it in a search. It takes admin privileges to actually delete an article - and admins who go around deleting articles without going through the official processes don't remain as admins for very long! It's much more likely that he simply does not have the notability required to justify an article...
  • He fails all the criteria as an academic (Wikipedia:Notability (academics)) because his work isn't cited elsewhere.
  • His books clearly fail Wikipedia:Notability (books) because they have not been given awards, or mentioned much elsewhere.
  • WP:AUTHOR is his best chance...but he fails almost all of those criteria too - and is pretty weak on the ones he doesn't outright fail.
So, no - I don't think he's worth a Wikipedia article - and I'm sure he hasn't bee suppressing any article that may have been written. SteveBaker (talk) 21:05, 13 August 2009 (UTC)
These sorts of fellows (it is always, isn't it?) are either deluded or charlatans, so perhaps "nut job" is the more charitable phrase. --Sean 15:57, 14 August 2009 (UTC)
It's better to avoid such terms, because they potentially violate WP:BLP (which yes, does apply to all pages on wikipedia, including the RD) unless perhaps you are just describing what a reliable source says about the person, but it's clear no one is, because we've established there are few or none on him. If his theories are completely unsupported, just say that, similar to the way you would (hopefully anyway) discuss problems concerning a wikipedian. Outside wikipedia you are of course free to say whatever you want, although it often remains best to avoid getting too personal Nil Einne (talk) 16:58, 16 August 2009 (UTC)

Micro black hole scenario

I think we can agree that there is no significant black hole threat to the earth from the LHC or any other machine being thought about.

However, that doesn't keep us from conducting a thought experiment: A microscopic black hole will "evaporate" very quickly, before it can collect enough additional matter to stay in existence. But what if were a little more massive? Would it begin to collect particles from nearby atoms? What would be the geometry of such a situation? How close would the nearby atom, or particle have to be?

Let's specify that it begins to collect particles. There are two possibilities: 1) It continues to grow and 2) Due to a random fluctuation, it runs out of nearby particles and evaporates anyway.

Continuing with Scenario 1), it will be attracted by gravity, and start falling towards the center of the earth, eating its way through the bottom of the LCH or whatever created it, and continue on down. Would it oscillate from one side of the earth to the other indefinitely, or is there a damping factor to cause it to come to "rest" at the center of the earth?

The creation of this black hole would be hard to detect, since it is happening on a subatomic scale, and it is collecting matter at a rate just barely enough to allow the black hole to survive, a few particles at a time, at first.

Let's assume it came to rest at the center of the earth as a very small black hole, and continued to collect matter. I think there would be no net change in observable gravity for some time period. How long would that period be? Seconds, months, years? Would the earth become a more or less empty shell? If so, how large would the "hollow" region be? A diameter of one cm, one km, 1,000 km? Of course the central region wouldn't be empty, because the black hole would be pulling matter towards itself.

How long would it be before its effects became noticeable? It could be quite a while since in the radial direction at least, gravity would not change. From the surface of the earth, does a point mass look the same gravitationally as the same mass distributed through the earth's volume? Let's change the scenario and allow the black hole to continue oscillating through the earth. Now the direction of gravity will fluctuate. In that case, how long before it is detected?

What other aspects of this thought experiment are interesting?

JFistere (talk) 18:30, 13 August 2009 (UTC)

Skipping past the "how big should it be?" part, I can answer the rest.
  • It'll eventually come to rest at the center of the Earth, per friction.
  • There will never be a true change in gravity -- no new mass is being created. The Moon's orbit will never be affected.
  • However, the Earth will collapse to fill any hollows, so as to attain hydrostatic equilibrium. This will reduce the Earth's radius, and thus increase gravity at the surface of the Earth (because the surface has moved).
  • How long? Eh, too much theoreticalness. I'd ballpark millions of years, but it's very heavily dependent on starting conditions (the rate of consumption will rise exponentially). — Lomn 18:57, 13 August 2009 (UTC)
So for some time we would just notice a gradual weight loss(edit) the same weight when we stepped on the scales, and an around the world trip would be shorter? Edison (talk) 19:11, 13 August 2009 (UTC)
No, why would you feel lighter? Anyways, a black whole that would normally evaporate in one second has a mass of about 20 tons, and a Schwarzschild radius of 3e-23m. That's about 100 million times smaller than the diameter of of a proton. It will be very hard to feed the 20 tons of mass or so per second needed to balance the Hawking radiation into that small a space. --Stephan Schulz (talk) 19:24, 13 August 2009 (UTC)
I think that was a typo. He said earlier one's weight would increase. JFistere (talk) 20:38, 13 August 2009 (UTC)
What everyone tends to miss here is that a mini-black hole with a mass of (say) 1kg - still only has the gravitational attraction at (say) 10cm from it's center that a 1kg ball of iron would have at 10cm...which is to say, utterly negligable. It's only when you get very close to the black hole that you notice its gravitational pull at all. That's because the acceleration is proportional to the square of the distance. But in order for a 1kg mass to have enough gravitational pull to make a difference, you have to be insanely close to it...much less than the radius of an atom. That's the only reason we don't get sucked into 1kg iron spheres...we just can't get close enough to them (even when we're touching them). So the probability of even one more atom happening to get close enough to our 1kg black hole to get 'eaten' by it is pretty small...and even if it does eat an atom once in a while, atoms don't weigh much. You won't even start to notice it's gravitational pull at 'reasonable' distances until it's grown enormously - and statistically, that's really unlikely. When you start to factor in the evaporation rates - it's truly impossible for a mini-black hole to have any detectable effect on something as big as a planet. SteveBaker (talk) 20:56, 13 August 2009 (UTC)
20 tons of matter evaporating in a second is going to be releasing a great deal of energy, so much so that nothing will get close to it due to radiation pressure if not particle pressure. Graeme Bartlett (talk) 12:19, 14 August 2009 (UTC)
Or we could work backwards. Say we want to start with a black hole with an event horizon with a similar scale to an atomic nucleus - say 10-15 m across. This is about 1020 Planck lengths, so mass is of the order of 1020 Planck masses or about 1012 kg (modulo some factors of 2). I reckon this is about the mass of a modest mountain or small asteroid - so not so very "micro". But we don't have to worry about evaporation any more, as primordial black hole says a black hole with a mass of 1012 kg has a lifetime equal to the age of the universe. Gandalf61 (talk) 12:42, 14 August 2009 (UTC)
Question: At the scale of an atomic nucleus - would such a micro-black hole produce the strong & weak nuclear forces - or would they be unable to escape the event horizon? If it does, wouldn't it actually repel atoms more strongly than it attracts them? SteveBaker (talk) 12:59, 14 August 2009 (UTC)
Why would the strong and weak forces repel atoms? The weak force doesn't do much, but the strong force is what holds nucleons and nuclei together. What usually holds atoms apart is electromagnetism and their electron clouds. --Tango (talk) 18:23, 14 August 2009 (UTC)

Study on tea and stress

The media in the UK is currently promulgating that "tea reduces stress", referencing a study by a psychologist at City University London named Malcolm Cross. Unfortunately I can't find the study anywhere, including Google, Google Scholar and Pubmed. Can anyone else find it? Here are some media sources: [18] [19] [20] [21]. --Mark PEA (talk) 18:49, 13 August 2009 (UTC)

I searched a bunch of medicine and psychology databases with no success. Perhaps the paper hasn't been published yet? I've certainly come across previous occasions when the newspapers have gotten all worked up by a pre-publication press release, for example, although I can't find one of those on the university's website or the site of the sponsors, Direct Line, either. A paper isn't listed on Dr. Cross's bio. Nothing at the BBC, either, which is unfortunate, as they tend to link to original documents. While I couldn't find a paper, Direct Line have put up a website and apparently had someone blend some special tea for them. On another note, I never knew we had an article on Potential effects of tea on health! --Kateshortforbob talk 21:17, 13 August 2009 (UTC)
I had better luck using Google News -- you can download a PDF of the executive summary here. Looie496 (talk) 23:14, 13 August 2009 (UTC)

Human skin color

What kind is human skin response to different light frequencies? I'm thinking about projecting the colors of the rainbow onto a face to 3d scan it with just a few images. -- (talk) 20:28, 13 August 2009 (UTC)

Your phrase "response to different light frequencies" is a very complicated way of saying the word "color". In other words, we could rephrase your question as: "What color is human skin?"...which I think you already know the answer to! Using "structured light" to do 3D digitisation is a reasonable one - but it's extremely tricky when you have to rely on the color of the surface. Projecting a grid of white light onto the face - in an otherwise dark environment is really a better approach - which is why that's how it's generally done. Another thing you need to think about is that pretty much all cameras don't respond to all the colours of the spectrum - they respond to red, green and blue. Hence you won't have the separation of information you're expecting to get. SteveBaker (talk) 20:44, 13 August 2009 (UTC)
Thanks for the answer. When I made the question I thought more about some generic rule for darker vs paler vs whatever skins, but you are probably right hinting this isn't a too good idea. On a second thought high contrast shapes sound a lot better (especially when I don't have access to too fine cameras). -- (talk) 21:17, 13 August 2009 (UTC)
Reflectance of the human skin has been studied in detail. You can start with the Color Science textbook by Wyszecki and Styles. In the 1982 edition see page 63, figures 2(1.4.6) and 3(1.4.6). --Dr Dima (talk) 22:21, 13 August 2009 (UTC)
Actually, Wyszecki & Styles is a really good textbook. It is a much better idea to just read it (rather than to jump straight to the page 63). --Dr Dima (talk) 22:25, 13 August 2009 (UTC)
This is actually something of a nontrivial question - human perception of colour has only about three degrees of freedom, which is not nearly enough to uniquely describe absorption across the entire visible light spectrum. I think it would be fun to do more research into the "complete colour" of many different everyday objects. Dcoetzee 22:28, 13 August 2009 (UTC)
Correct, with only three cone types in our retinas we can not perceive the details of the absorption spectra of surfaces under any given natural illuminant. That's why it is such a good idea to read the textbook, and to try to understand what it is that we see perceive as color, and how the color percept changes with the changes in illuminant, absorption spectrum, background, and so on. --Dr Dima (talk) 22:53, 13 August 2009 (UTC)
However, the question is about digital imaging. I suspect that the rainbow being projected is not a true spectrum, but an image of one, projected with only three primary colors. The camera used to image the face after a rainbow has been projected on it will likely also use three primary colors, hopefully ones very close to the projector's. So the question becomes simply "What color is human skin, as seen by an RGB camera." You could easily get a "baseline" value by switching the projector to show all white, and then compare that image to the rainbow colored image. APL (talk) 23:23, 13 August 2009 (UTC)
While it's true that our poor, pathetic eyes can't see all of those colours, that's unimportant in this case because all commonly available cameras have the exact same restriction. They are designed to see the same way we do. So what we see is what the camera sees. You could certainly use a monochrome camera and a large selection of colored filters to build a camera that could see in many more frequencies - but the entire point of the OP's proposed technique is to do it all with just one picture. If you can take your time and take lots of pictures then you can either move the projected light source, move the camera or move the subject in order to get enough information to make a 3D image...those techniques being much simpler than messing around with 'pan-spectral-imaging' and completely avoiding the issues of people with different colored skin, what to do about colored hair, eyes, lips and other things that would undoubtedly complicate getting a 'rainbow' image into a 3D form. I agree with the point that actually generating a true spectrum isn't exactly trivial. Using sunlight and a prism is probably the simplest solution - but it would be horribly inconvenient in many applications of 3D scannera. Synthetic "true white" light sources (those with roughly equal quantities of all of the frequencies) are very rare most cases, the spectrum of artificial light is such that you don't get a good 'rainbow' at all.
Our OP might like to investigate my personal Wiki - where I present a design that I did for a 3D scanner using a video camera and a laser pointer: [22]. That project has been taken up by a team of OpenSource programmers who have turned my 'quick hack' into something that really works very nicely: [23]. If you have a decent digital video camera already - you can build this in an hour and have working 3D scans in a day.
SteveBaker (talk) 00:08, 14 August 2009 (UTC)
It's really only two degrees of freedom. While the eye's response has 3 degrees of freedom, only two of those are what we call "colour", the 3rd is brightness. There are other ways of dividing them up, of course, but having one as brightness is the most useful. This diagram shows one way of depicting the two remaining dimensions (in a nice normalised fashion). As you can see, all the colours are shown on a region of a plane, so it is clearly a 2D space. (Note, the colours in the image are approximations, your screen can't produce the whole range.) --Tango (talk) 00:31, 14 August 2009 (UTC)
I'm a little lost - how do you intend to get depth information from color information? Amplitude is only weakly related to depth; so whatever color light you shine, you still have to do some postprocessing to convert (guess) the true depth. I don't know why different colors would have different mappings between depth and amplitude, so a single image would probably work just as well as several color-channels. Nimur (talk) 01:17, 14 August 2009 (UTC)
The general idea is to use some kind of 'structured' light to extract 3D information from a 2D photograph.
Put simply - suppose you use a slide projector to shine a regular grid of white lines onto a bumpy surface like someone's face. Then, take a photo of that surface from a little way off to one side of the projector. By noting the position of the grid lines in the photo, you can deduce how the regular grid was distorted by being projected onto that surface. That allows you (in principle - and in rather limited situations) to recover three dimensional position information from a two dimensional photograph.
The problem is that you only get to sample at the resolution of the grid - and it's hard to tell from the photo which grid intersection in the photo is from which intersection from the projector. The finer you make the grid, the harder that determination becomes - and the coarser you make the grid, the more surface detail you miss.
For that reason, more often, instead of using a grid - you use a simple straight line or even just a dot and scan it across the surface - taking lots of pictures, maybe with a video camera. This lets you use laser light - for extra precision. As demonstrated on my Wiki. Using "time" as one of the parameters gives you a way to know precisely where the light was being shone when each photo from the video was taken - and gives you vastly higher precision (my home-made scanner gets better than 0.5mm precision - and it's built out of Lego, a cam-corder and a $5 laser pointer!).
The trouble with that for the particular case of scanning human faces is that people can't sit still long enough - and shining lasers into people's eyes is NOT recommended!
Our OP is thinking to shine a "rainbow" of light onto the surface instead of a grid and to measure the color of each point in the photo to discover where a particular color from the projector ended up on the surface...this works just like the grid - but leaves no ambiguity because each point indicates where from the projection it came from by virtue of it's color - and it's as precise as you have color fidelity in light and camera. It's a rather clever idea actually.
Sadly, it fails for anything other than a perfectly uniform white surface because you can't easily tell whether a color variation at a particular point is due to a 3D displacement of the surface - or whether it's a change in reflectivity of the underlying material. So, the light that falls (for example) on the person's lips might look a little more red than it would if it had landed on the person's cheek (say)...and that would fool the image processing software into guessing that the light from the projector had been displaced by more than it really had. Bottom line is that the OP's idea is quite ingenious - but sadly not very useful for annoying practical reasons.
My rotating scanner is also imperfect - it doesn't work well for very shiney surfaces because they bounce the light off so it hits other parts of the object. None of these kinds of scanners handle parts of the surface that are never lit by the light (or which are never visible from the camera). There is an inherent compromise between this 'shadowing' problem (which forces you to keep the light source and camera very close together) and the desire to get more displacement of the image for any given 3D bump size by moving the two further apart.
However, for things like faces, the technique works really well.
SteveBaker (talk) 02:40, 14 August 2009 (UTC)
You might make it work with two images, a white light image then the rainbow image. Still seems like it'd be tricky. APL (talk) 05:42, 14 August 2009 (UTC)
Also, why go with a regular rainbow? You could go with a much more complex pattern. (Something that would probably look like noise) that way pixels that are similar in tone are not normally next to each other. APL (talk) 06:19, 14 August 2009 (UTC)
Yep - there are many alternative ways to do it - but they all require some kind of "structured light" - and some means to identify which "pixel" from the projected light source you are seeing at which position in the photograph(s). I could certainly imagine some kind of random dot pattern and some kind of image recognition trick that would match the pattern in the photo to the original pattern that was projected...but the distortion of the image and the problems of some parts of the source image not being present at all in the photo conspire to make this a fairly tricky software task. With a simple turntable-based system where the object was rotated under a vertical line of red laser light - I was able to extract a respectable 3D object with just 500 lines of software...very simple indeed. There are other techniques such as "shape from shading" (Photometric Stereo) - and I see we have an article about Structured light and even Structured-light 3D scanner. One cool trick I saw recently entailed taking two photographs, one with a flash and one without. Subtracting one image from the other gets you an approximation for the surface reflectivity - and factoring that out of the image allows you to use the brightness of the resulting monochrome image to estimate the slope of each pixel relative to the light source direction using lamberts law. Then you can integrate the slope information to get height. It's actually rather error-prone - but for many purposes it lets you get what you need. SteveBaker (talk) 12:52, 14 August 2009 (UTC)

Fun with negative refraction?

Hi. Are there any specific optical effects with negative refractive materials that one would consider interesting? For example, how would I look in a mirror with a negative refractive index? Or, how would the world look like through a negative refractive window, etc. etc.? Thanks in advance, Kreachure (talk) 23:49, 13 August 2009 (UTC)

Basically negetive means that it will go the opposite way. For example when you put a a pen in water it appears bigger, negetive will make it appear skinnier, so much so that it might appear to be invisible (so thin you can't see it) but light from the other side still gets through ok. —Preceding unsigned comment added by (talk) 03:36, 14 August 2009 (UTC)

August 14

Gull-proof sack?


How does this work, exactly? --Kurt Shaped Box (talk) 00:05, 14 August 2009 (UTC)

Looks like they have an embedded weave of fibers in there that makes it more difficult for gulls to peck a hole in the bag. (talk) 00:12, 14 August 2009 (UTC)
Tyvek, possibly, or something similar. --Tagishsimon (talk) 00:15, 14 August 2009 (UTC)
Is the market for specifically-seagull-proof woven garbage bags really that large, or is this just a special printed label on an otherwise generic animal-resistant sturdy trash bag? Nimur (talk) 01:10, 14 August 2009 (UTC)
Good question. I wonder if large gulls (they being the ones who generally raid bin bags in towns) have more powerful bites than, say housecats or foxes? It's actually quite possible, considering that the jaw muscles are bringing all the pressure of the bite to bear on a much smaller surface area than you'd find in the mouth of a mammal. --Kurt Shaped Box (talk) 01:30, 14 August 2009 (UTC)
In many British localities, the problem of seagulls attacking garbage sacks pre-collection and spreading their contents all over the street is very considerable. I recently read a long blog entry touching on this problem in Edinburgh (though it was more about the misapplied monitoring of those who compounded the problem by putting their sacks out too early): not sure if it's netiquette/Wiki-appropriate to post a link here, though. (talk) 01:32, 14 August 2009 (UTC)
I agree the scale of the problem, but note that Edinburgh has suffered a garbage collection strike in recent times which will have exacerbated the problem for them. --Tagishsimon (talk) 01:48, 14 August 2009 (UTC)
I don't know if this is the case in Edinburgh but I've heard that in some places, once the gulls have strewn the rubbish all over the street, the bin men are all like "Meh, it's not our problem now - it's not in a bag/wheelie bin" and they'll leave it there to rot. --Kurt Shaped Box (talk) 01:53, 14 August 2009 (UTC)
Haha, you read Language Log? John Riemann Soong (talk) 14:09, 14 August 2009 (UTC)
Well spotted, John! Both read and occasionally comment on. (talk) 16:48, 14 August 2009 (UTC)
A couple of weblinks for reference: East Devon council, BBC News. It's a re-usable bag, so presumably there's a normal polythene bag within; they're for users who do not have access to a wheelie bin, and Devon, at least, is charging a fiver for them. --Tagishsimon (talk) 02:01, 14 August 2009 (UTC)
For a sack?! Time to go into business: Undercut them by 50% and you'll still be making a huge profit margin. Tempshill (talk) 03:04, 14 August 2009 (UTC)
Am I the only person who squinted at the photo and concluded it was some kind of a sack for reusable seagulls? It would parse SO much easier if it had been written:
          Seagull Proof
           Refuse Sack
Or maybe it's just time to get my eyeglasses upgraded :-)
--DaHorsesMouth (talk) 22:43, 14 August 2009 (UTC)
It just needs some punctuation: "seagull-proof" needs a hyphen and only the first word should have been capitalised. Although: "Reusable seagull? Proof! Refuse sack."...yeah, I'd refuse the sack alright. SteveBaker (talk) 02:30, 15 August 2009 (UTC)
I'd sincerely hope that you weren't intending on (re)using the seagull for evil. --Kurt Shaped Box (talk) 01:28, 17 August 2009 (UTC)
I'm having a hard time imagining a non-evil use for some kind of zombie re-used seagull - which (since they have proof) is the only reason I need to refuse the sack. I hope this clarifies the situation. SteveBaker (talk) 21:57, 17 August 2009 (UTC)

Sitting too close to a TV

Is it true that sitting too close to a TV is dangerous? And if so, then why is it ok to have a computer monitor so close to your face? ScienceApe (talk) 01:18, 14 August 2009 (UTC)

a) because it strains the muscles in your eyes
b) it's not okay to sit too close to the computer monitor for long periods of time, for the same reason.
Regards, --—Cyclonenim | Chat  01:44, 14 August 2009 (UTC)
No, it's not true. I've been sitting close to computer screens for close to 40 years - and aside from being a little astigmatic in one eye (requiring glasses for driving - but nothing else), I'm doing fine. I had my eyes tested just a few weeks ago - and my eyesight hasn't changed in the slightest over the last 30 years. Admittedly, I'm not a good statistical sample - but I've worked with an awful lot of people who also spend their entire waking hours glued to a screen - and I don't see any horrible eye injuries. There have been many studies about this kind of thing and no clear results have ever been attributed to computer use. Sure, you can get eyestrain - but that's not a permanent condition. You eye muscles are like most other muscles - they get tired - you rest them - they recover. It's a good idea to take a break from computer use for at least a few minutes in every 20 minutes (mostly so you get a change of posture and a break from typing) - and using that time to focus off into something in the distance will help to relax your eye muscles and avoid strain. Almost all of the problems relating to computer use relate to bad sitting posture, poorly adjusted work-stations, lack of exercise and repetitive strain issues due to too much rapid typing - or excessive mouse use. I'm pretty sure that the "Don't sit too close to the TV, you'll hurt your eyes." admonition that probably everyone's mother has delivered repeatedly has more to do with you blocking the adult's view rather than any evil deathrays emitting from the screen. SteveBaker (talk) 02:13, 14 August 2009 (UTC)
I think the best thing is to direct people to Myopia#Etiology and pathogenesis. SB's claim that 'many studies about this kind of thing and no clear results have ever been attributed to computer use' is not entirely accurate. As the article mentions, some studies have found evidence frequent near work (which includes computer use and sitting very close to the TV) may be a contributing factor, while others have not. In other words, it's a case of, we still can't be sure, rather the being definite either way (this doesn't exclude the possibility the evidence is far stronger in one direction). Edit: After some external discussions about this, I feel I should emphasise near work includes a lot of things besides normal computer use and sitting very close to a TV. It obviously includes stuff like reading a book. Also I've been wondering whether to mention this or it will just confuse things but I decided to go ahead. I believe one of the reasons why there is a fair amount of suspicion environmental factors may be at play is because of the greatly increasing apparent prevalence of myopia seen in some populations (especially East Asian I believe) that appear to be correlated to industrialisation and development. It's possible these are related to improved diagnosis and perhaps a greater demand for visual acuity but the trend appears to be quite strong and I believe several factors including some of the studies the article discusses suggest something else may be at play Nil Einne (talk) 04:22, 14 August 2009 (UTC)

Some screens emit radiations that can be harmful. —Preceding unsigned comment added by Quest09 (talkcontribs) 16:28, 14 August 2009 (UTC)

Can you point us to sources supporting your otherwise uncorroborated assertion? (talk) 16:46, 14 August 2009 (UTC)
TVs do emit harmful "radiations," namely the horrible programming that rots the mind. But I think Quest09 is referring to radioactivity. I recall a study from the 1990's that did find detectable radiation from the face of CRTs, both computer monitors and TVs. The radiation was found to be from radon in the dust that accumulates on on the front of the class due to eletrostatic attraction induced by the charge buildup. The same effect probably occurs for plasma screens but not for LCDs. The correct mediation is to clean the screen, and of course to clean any other dust buildup in your house. -Arch dude (talk) 17:28, 14 August 2009 (UTC)
Found a ref: [24] -Arch dude (talk) 17:32, 14 August 2009 (UTC)

More about it: (...) most surveys of cathode ray tubes in the literature were made while the units were energized and indicated low-energy x-rays, (...) See [25] Moms were right after all, sitting too close to TV can harm you. --Quest09 (talk) 18:31, 14 August 2009 (UTC)

You might want to read that reference more carefully. That was not x-rays from the CTR beam. It was gamma radiation from the materials from which the tubes were manufactured. "Significalnly above background" is a term from the field of statistics, where "significant" means that the results are statistically higher than background, not "significant" as in harmful to health. Note that bricks, stones, and cinder blocks also emit radiation that is "significalntly above background," and fo the same reason: trace amounts of transuranics in the earth from which they are made. The radon/dust effect I mentioned above is a whole lot higher, at five times background, but is still not very unhealthy. -Arch dude (talk) 20:27, 14 August 2009 (UTC)
My reference is a reference about low energy x-ray radiation, even if its main topic is radioactivity in cathode ray tube. Quest09 (talk) 11:10, 17 August 2009 (UTC)

Mineralogy of the Black Stone

Muslim legends state that the Black Stone fell from the heavens. Has it ever been analyzed to determine whether it's a meteorite? NeonMerlin 05:58, 14 August 2009 (UTC)

As of 9 months ago, at least, the black stone had not actually been scientifically analyzed, although one geologist (Zaghloul al-Naggar) was wanting to take a sample to do so.[26] This page claims that “Western Scientists have confirmed that the black stone…is an outside meteorite object”, but the audio file that that claim links to, which is an interview with Zaghloul al-Naggar, does not actually support the claim that there has been an actual analysis of the stone. Note that although Zaghloul al-Naggar has a PhD in geology, he hasn’t published any peer-reviewed research, his web site is all about promoting islam, and he has called Jews “devils in human form”[27]. So it’s questionable as to how unbiased he would be able to be, even if he actually did an analysis of the black stone at some point. Red Act (talk) 07:31, 14 August 2009 (UTC)
P.S. This same web page also links to an audio file in which Zaghloul al-Naggar explains how through his careful interpretation of the quran, time descriptions in the quran can be shown to be consistent with the speed of light, accurate to three decimal places. With such a strong susceptibility to confirmation bias, and given that islamic tradition requires the stone to have fallen from heaven, it seems essentially impossible to me that Zaghloul al-Naggar would conclude that the black stone was anything other than a meteorite, if he ever does get his hands on a sample, regardless of what the black stone is actually made of. And I can’t find anything about anyone else with any scientific credentials hoping to get a sample and do an actual analysis. Red Act (talk) 08:15, 14 August 2009 (UTC)
I don't think anyone would be willing to do an actual analysis -- if he/she does and it turns out to be anything other than a meteorite, the Islamics would put a fatwa on his/her head (just as they did to Theo van Gogh (film director) for making an anti-Islamic documentary). Few scientists would be brave enough to risk that. (talk) 00:16, 18 August 2009 (UTC)
I find it appaling that in the 21st century we are still in an age where practically the whole planet can be intimidated by the beliefs of people who worship a rock that fell from the sky.. Vespine (talk) 00:25, 21 August 2009 (UTC)

Direction of rotation of helicoptor blades

Which way do helicopter blades rotate? (i.e. clockwise or counterclockwise, when viewed from top) Is it standard? or does it vary across models? Is there any reason to prefer one way or the other? or is it arbitrary? -- (talk) 06:07, 14 August 2009 (UTC)

American generally go counter-clockwise, the other type is French which go clockwise, other countries pick between the two. I believe clockwise is more common outside the US. It is pretty much arbitrary, like which side of the road you drive on. Vespine (talk) 06:17, 14 August 2009 (UTC)
From Helicopter rotor#Rotor configurations: “When viewed from above, the main rotors of helicopter designs from Germany, United Kingdom and the United States rotate counter-clockwise, all others rotate clockwise.” Of course, some helicopters have dual main rotors, in which case they rotate in opposite directions. Red Act (talk) 06:32, 14 August 2009 (UTC)
You can usually tell just by looking at the rotor blades - the blades are thicker on one side and taper down to a knife-edge on the other - just like the wing on an airplane. The fatter edge of the blade is the "leading" edge - it meets the on-coming air-flow. SteveBaker (talk) 12:39, 14 August 2009 (UTC)
On most helicopters it is easier to look at which side the tail rotor is, right side for clockwise and left side for counter-clockwise. MilborneOne (talk) 16:36, 14 August 2009 (UTC)
Unless it has fantail design, like the Eurocopter EC 135, then you are back to SB's method. Googlemeister (talk) 16:42, 14 August 2009 (UTC)
I was going to mention the tail rotor - but then it occurred to me that it shouldn't matter which side it's it's possible that this isn't a hard-and-fast rule (although I agree it's common). The pitch of the tail rotor can be adjusted to direct its thrust in either direction - I can't see why it would need to be on a particular side of the tail. SteveBaker (talk) 02:24, 15 August 2009 (UTC)

Electric power stations

how does a electric power station pay for itself. The esolar 5MW station has me wondering. -- (talk) 07:13, 14 August 2009 (UTC)

The owners of the power station sell the electricity produced in the Electricity market. Apparently California (where I think the station you're asking about is located) has a wholesale electricity market, where "competing generators offer their electricity output to retailers. The retailers then re-price the electricity and take it to market, in a classic example of the middle man scenario." AlmostReadytoFly (talk) 07:23, 14 August 2009 (UTC)
As for "how do they build it in the first place" - they get a loan, which they later repay with money from selling the electricity. Dcoetzee 07:54, 14 August 2009 (UTC)
Besides that, there are subsidies, depending on the type of power station and the country or state. Icek (talk) 11:42, 14 August 2009 (UTC)
By changing power suppliers, I recently changed from a standard residential rate of 11.34 cents per kwh to 8.50 cents per kwh. The power comes to me from the same grid and through the same pole transformer. There were no wiring changes at all. To add insult to injury, the original supplier (PennPower) still bills me, but passes the money to the new supplier (Dominion People Plus). No doubt PP gets a small fee for doing the billing. I live in NW Pennsylvania. —Preceding unsigned comment added by (talk) 15:55, 14 August 2009 (UTC)
Why is consolidated billing an insult or an injury (i.e., does it really matter where you mail your check)? As you said, "The power comes to me from the same grid and through the same pole transformer. There were no wiring changes at all." That infrastructure probably has significant startup investment and ongoing maintenance costs. Even if you mailed Dominion directly for the actual poewr generation, you are still using services of PP to get the power, so you would expect Dominion to tack additional charges to be passed back to PP anyway. DMacks (talk) 19:58, 15 August 2009 (UTC)


Is molten iron still attracted by a magnetic field? I know that heat erases magnetic properties of a magnet, so molten iron can't be a magnet, but I don't know if it can be subject to external magnetism. -- (talk) 10:16, 14 August 2009 (UTC)

Above the Curie temperature (the temperature at which you "erase magnetic properties"), iron no longer behaves ferromagnetically but paramagnetically. It is still attracted towards stronger magnetic fields, but the attraction is weaker - see Curie's law. There are also diamagnetic substances which are repelled by magnetic fields (but most only weakly so, except for superconductors). I don't know exactly how iron behaves in the molten state, but this article might be useful (if you have access to it). Icek (talk) 11:33, 14 August 2009 (UTC)

Positioning sound

I was having a dispute yesterday about the extent to which our perception of where sound comes from is based on what we see. It seems to me that with only 2 ears, you could only place the source of a sound on a plane - that is, you could not tell whether it is in front of, above, behind or below you. Is there any way of discerning these without rotating your head while listening, or would a blind person not be able to tell whether an instantaneous click sound was produced behind his head or in front of it? Insperatum (talk) 10:22, 14 August 2009 (UTC)

Sound localization is not only done by differences in the sounds from the 2 ears, but also by different dampening of frequencies at different angles by the pinna. This can in turn be used to create the illusion of 3D sound with speakers arranged in a plane. Icek (talk) 11:40, 14 August 2009 (UTC)
Yep - basically, we can do simple stereo localization by the obvious tricks of comparing the delay between the sound waves entering our two ears. But because our heads are not symmetrical - a sound coming from above passes through a different mass of bone and brain than one coming from below. That causes different delays, reflections and absorption of different frequencies in the sound. We're able to detect that change in the quality of the sound and use it to estimate that third dimension...albeit imperfectly. There is an audio recording system from a company called Sennheiser which uses a pair of microphones embedded into the ears of a fake plastic head which is designed to transmit, delay and reflect sound just like a real human head. If you listen to a sennheiser recording on a pair of in-ear headphones, then you can clearly hear that third dimension of sound. There was a while in the 1970's when you could buy sennheiser recordings of all sorts of music. Unfortunately, you have to listen to them on headphones - the effect is largely destroyed if you use loudspeakers. There are some computer software techniques that crudely simulate the effects of all of that 'stuff' that happens in your head and applies that to sounds used in computer games. The effect is moderately successful - but again, it only works well when you are using in-ear headphones. SteveBaker (talk) 12:27, 14 August 2009 (UTC)
I seem to recall that there's some debate about the mechanisms of 3D acoustic perception; it seems likely that the brain fuses in some visual cues into the mix, in addition to the stereo-ear-channel processing for delays and frequency-dependent amplitude variations. Nimur (talk) 14:44, 14 August 2009 (UTC)
How do ear muff-style headphones compare to in-ear style? --Sean 16:17, 14 August 2009 (UTC)
In this case, not well. You really need the speakers to be in roughly the same position in your ears as the microphones in the fake head. I believe there have been some successes at making synthetic 3D audio using cup-type headphones. SteveBaker (talk) 02:21, 15 August 2009 (UTC)
What if you had a 7 speaker home entertainment system? John Riemann Soong (talk) 15:11, 14 August 2009 (UTC)
Well - if they are positioned all around you (including above and below), I presume that suitable recordings could be made for them that would reproduce 3D moderately well. SteveBaker (talk) 02:21, 15 August 2009 (UTC)
"Visual capture" or the "ventriloquism effect"[28], [29] is the phenomenon of sight overruling auditory localization. When 16 mm movies were the common mode of audiovisual presentation, sometimes the speaker was on the projector, or was somewhere other than behind the projection screen. But during the movie, the audience was able to perceive the speech as coming from the actors' images on the screen. With only 2 ears, absent head movement such as tilting the head, we can localize sounds in the lateral dimension but not in the vertical dimension.[30] It would take 3 ears, not in a line, to truly localize in 3 dimensions. Edison (talk) 15:17, 14 August 2009 (UTC)
It is certainly possible to tell, with the eyes closed, and without head movement, whether natural sounds in the environment are coming from in front or behind. With binaural sound from earphones, this does not seem to be the case. This includes "binaural" recordings made with mics inside an artificial head. I did not note front/rear localization in listening to such a recording through earphones. Perhaps as stated elsewhere the influence on sound quality of the head aids in this for normal environmental sound. As for "visual capture," I can remember watching a movie, with the speaker behind me on the 16mm projector, when the projector lamp went out. The sound source location seemed to "fly" swiftly, but not instantaneously, from the movie screen, in front, to the projector, behind. Edison (talk) 22:20, 14 August 2009 (UTC)
One common reason for not hearing the 3D effect is if you have your earphones swapped into the wrong ears. I found the stennheiser recordings pretty convincing. SteveBaker (talk) 02:21, 15 August 2009 (UTC)
Off-topic, but the McGurk effect is an interesting case of sight overruling sound. --Sean 16:17, 14 August 2009 (UTC)
It seems to me that the need for visual queues is easily debunked. I know two blind people rather well. They are better at localizing a sound than I am. They have no visual queues. So, they are doing it strictly with two ears. -- kainaw 17:16, 14 August 2009 (UTC)
Not directly relevant to the question, but it may be interesting to know that barn owls localize sound in two dimensions by having one ear tilted up and the other tilted down -- this causes amplitude and time differences to carry indpendent information. Looie496 (talk) 17:34, 14 August 2009 (UTC)
It is difficult to locate the source of a single-frequency (sinewave) tone without moving the head. I have also observed that my cat snoozes contentedly while surrounded by all these household noises that it has become used to: radio, TV, traffic, door slams, kids yelling, etc. However a firework overhead upsets pussy greatly. It is clearly not the volume but the unexpected direction of the sound that causes alarm. Cuddlyable3 (talk) 18:25, 14 August 2009 (UTC)
That's not surprising though - the brain is relying on different transmission properties of different frequencies within a natural sound source. A simple, pure, sine wave wouldn't provide enough cues. You'd probably do better with 'white noise' or more natural sounds. SteveBaker (talk) 02:21, 15 August 2009 (UTC)

←Slightly off-topic, but holophonics may be of interest, as may this sound clip (use headphones). Fribbulus Xax (talk) 22:12, 14 August 2009 (UTC)

toxicity of crown ethers

Is it me or would a tiny amount of crown ether be potentially very toxic if ingested? I was wondering, because there aren't many mentions of safety precautions / MSDS stuff on our articles that cover them. John Riemann Soong (talk) 14:12, 14 August 2009 (UTC)

They are moderately toxic page 5.
Long term effects are unknown. (talk) 14:19, 14 August 2009 (UTC)
John, it seems silly to even have to say this, but several of your previous questions seem to suggest that you plan to eat the results of your chemistry experiments. Please, don't do this. There's no way that the Reference Desk, or the publishers of the MSDS, or any other source, can know what is actually in your concoction. If you're so interested in food science, maybe you can consider interning in a lab or a company which specializes in chemistry for food applications. That way, you can play around with some expert supervision. Like many scientists, I'm sure you're excited about homebrew lab experiments, but whether you're working with chemicals, explosives, pressurized gases, (whatever) - the rules of lab safety don't disappear just because you're unsupervised. Nimur (talk) 14:51, 14 August 2009 (UTC)
While we're on the subject of crown ethers and toxicity, has anyone tried to use them as antidotes for mercury poisoning? I know they're good chelating agents, but would they work for chelating mercury out of a person's body? (talk) 04:45, 16 August 2009 (UTC)
I don't know of any published info about that. Would be more likely with a crown thioether (sulfur seems to be a better ligand for mercury than oxygen is). Would want to put some sort of hydrophilic chain attached, since crown ethers are good for solubilizing ions in non-ionic solvents (compare structures of given treatements in the mercury-poisoning article), and the goal is to make the mercury excretable rather than stay in any lipophilic environment. Also, crown-ethers are good and specific chelating agents for cationic metals, but only work well if the metal atom fits inside the crown. For example, 12-crown-4 holds Li+, 15-Crown-5 holds Na+ and K+, and 18-crown-6 holds K+. Given the amount of such ions in the body, need something with a pretty high and specific affinity for mercury. Mercury is large, so would need a pretty large ring to get decent binding I would think. Although interestingly, our 15-Crown-5 article says that one has good selectivity for lead. DMacks (talk) 16:11, 16 August 2009 (UTC)
Water solubility increases with ring size, so that may also help solubility. John Riemann Soong (talk) 16:44, 16 August 2009 (UTC)
So, a hydrophilic-derivatized 15-crown-5-thioether could work for lead (and thus prob'ly for mercury too)? That's a good idea... where can I get the funding and the starting materials? DMacks, are you interested in this project? (talk) 00:26, 17 August 2009 (UTC)
I just looked up the MSDS for 15-crown-5: it's got a health hazard rating of 2 and a REALLY big LD-50, so toxicity problems will likely be relatively minor (after all, the antidotes in use now, like British Anti-Lewisite are also moderately -- or in some cases not-so-moderately -- toxic). A bigger issue at this time is, will it work like we want it to? (talk) 02:53, 17 August 2009 (UTC)
Guess we'd better start with lit-search. Turns out synthesis and use of crown-thioethers for chelation of mercury ions with apparently good selectivity is known. [31] among other refs don't even require advanced academic search engines to find. I didn't narrow down to physiological uses. DMacks (talk) 06:34, 17 August 2009 (UTC)
Great -- someone else has beat us to our idea AGAIN!!! It's hard to be an inventor these days, ain't it -- you come up with some great idea, and then you find out someone else has already put it on the market. Kinda sucks, don't it? Well, let's you and me keep coming up with more ideas till we come up with something nobody thought of yet. (talk) 23:08, 17 August 2009 (UTC)
Thioethers have sharper bond angles, don't they? Won't that change the geometry a bit? John Riemann Soong (talk) 04:59, 17 August 2009 (UTC)

blood in the water

Some species of sharks are known to be able to detect blood in water at great distances. Are there any bony fishes that have this ability? Googlemeister (talk) 16:39, 14 August 2009 (UTC)

Sorry to nitpick and not answer, but it would be more precise to say sharks detect blood in water at very low concentrations. (talk) 17:39, 14 August 2009 (UTC)
I don't quibble with the OP's words "detect blood at great distances" but if anyone can give a figure for a typical distance, can they say how long it takes for the blood to travel that distance? Cuddlyable3 (talk) 17:57, 14 August 2009 (UTC)
The diffusion rate of the blood would depend on the temperature of the water and local currents. My hunch is that the diffusion rate is going to not be uniform in all directions and vary significantly. The shark article gives the unsourced figure for sensitivity "as little as one part per million of blood in seawater". You can make a circular cow type approximation as to how far away the shark can sense blood while ignoring the time factor by assuming X amount of blood was spilt and assuming it is evenly mixed at the concentration of one part per million in a sphere of water. The radius of the sphere represents the distance the shark will sense blood. 1 mL of blood (several drops) mixed in 999,999 mLs of water gives 1ppm blood. 1 mL of anything is 1 cm3. 1,000,000 cm3 corresponds to a sphere with a radius of 62 cm. According to blood, "the average adult has a blood volume of roughly 5 liters" or 5000 cm3. Adding in the blood you get a volume of liquid of 5,000,000,000 cm3. That corresponds to a sphere with a radius of ~ 1060 cm or 10.6 meters. (talk) 01:22, 15 August 2009 (UTC)
some predatory bony fish without the lateral line (the organ which sharks detect the struggles of fish and blood) they can detect it but in higher concentrations. around 10,000 p.p.m —Preceding unsigned comment added by The mophead (talkcontribs) 18:29, 14 August 2009 (UTC)
The lateral line detects motion (with little hairs, like your inner ears), and sometimes electrical impulses, but how could it detect blood in the water? --Sean 20:59, 14 August 2009 (UTC)
I'm fairly sure it can't. They taste/smell (the difference is minimal) the blood. --Tango (talk) 21:45, 14 August 2009 (UTC)
Catfish probably can although I'm not sure they would be looking for blood specifically. According to this book, catfish are very sensitive to amino acids. A channel catfish can sense alanine at 10-9 to 10-11 M. If I did my math right that corresponds to a minimum sensitivity of roughly 1 to 100 parts per trillion. (talk) 01:45, 15 August 2009 (UTC)
Catfish thrive as bottom feeders in muddy rivers, so scent is a main means of finding prey. No visibility to see the food. Edison (talk) 19:15, 15 August 2009 (UTC)

acid question

If you place a gold alloy in acid that is not aqua regia (90% AU, 10% Cu) will the acid dissolve only the copper leaving you with a somewhat porous remainder? Googlemeister (talk) 16:49, 14 August 2009 (UTC)

The principle is known (see Raney Nickel), but only 10% copper will probably not provide a connected network of voids for this to happen, (try 20%) (also copper doesn't dissolve in many acids...) (talk) 17:56, 14 August 2009 (UTC)
Copper will dissolve fine in pure nitric acid while gold will not. That may work. Also, if you grind up the alloy into a fine powder, you may be able to get enough surface area to get more of the copper out. --Jayron32 04:57, 15 August 2009 (UTC)

chameleons: will they eat off your hand?

i have a pet yeman chameleon and im not sure if they will eat of my hand. or will it count my hand as competition for food? —Preceding unsigned comment added by The mophead (talkcontribs) 18:25, 14 August 2009 (UTC)

This thread says that they can and will bite, depending on the temperament of the animal. --Sean 20:34, 14 August 2009 (UTC)
Are you asking whether they will eat food out of your palm, or if they will devour your hand itself? The grammar of "eat off" is ambiguous. -- (talk) 21:59, 14 August 2009 (UTC)
I have a bird that tries to eat off my fingers every time I put my hand in the cage, but it rarely breaks the skin. Edison (talk) 22:22, 14 August 2009 (UTC)
Is it a parrot of some denomination? They tend to do that. Unless the bird is obviously scared of your hand or annoyed by your presence, it's likely a substitute for the playful(ish) beak sparring that they engage in with others members of the same flock. --Kurt Shaped Box (talk) 00:01, 15 August 2009 (UTC)
I also enjoy the ambiguity of the hand competing with the chameleon and with the food.  :) --Sean 23:45, 14 August 2009 (UTC)
May I remind respondants that per Wikipedia:Reference_desk/guidelines we are specifically told: don't poke fun at a poorly-written question. SteveBaker (talk) 02:07, 15 August 2009 (UTC)
I'm honestly just confused about what they are asking. I'm not sure I understand what the bit about competition for food is meant to imply. -- (talk) 04:31, 15 August 2009 (UTC)
There is a difference between "They eat off your hand" and "They eat your hand off"... Dauto (talk) 21:45, 15 August 2009 (UTC)
I had a pet chameleon when I was a kid, living in Kenya (I have no idea what kind of chameleon). It was a very small specimen - maybe just about an inch long with it's tail curled up. It would stand on the tip of my finger while I carried it around the room looking for flies and other insects for it to feed on. Because it had a 2" tongue (pretty remarkable for a 1" animal!) - you'd just have to get it within range of it's victim and it would do the rest! However, it only seemed interested in live insects - so "hand-feeding" in the conventional sense was impossible. It never bit me...but it was pretty tiny. SteveBaker (talk) 02:14, 15 August 2009 (UTC)

Calculating my daily calorie intake needed to lose weight

If I know my current weight and my height, what's the best way of estimating how many calories I should eat each day to stay at that weight? (The idea being that I then reduce that amount so that I gradually lose weight). Thanks (talk) 18:46, 14 August 2009 (UTC)

There are numerous estimation calculators online, but you probably should not put a great deal of faith in them as metabolism (baseline calorie usage) can vary a great deal among different people who weigh the same. The US government usually assumes people eat 2,000 kcal a day when they provide nutrition values. Googlemeister (talk) 18:49, 14 August 2009 (UTC)
See Schofield equation and Harris-Benedict equation. For more in-depth information, see this. Red Act (talk) 19:14, 14 August 2009 (UTC)
There are calculators online that take in a lot of info about your height, weight, and activities, that try to give you an indication of what your baseline is. Google "Base metabolic rate". -- (talk) 19:31, 14 August 2009 (UTC)
It's all a matter of having calories consumed greater than calories coming in. There are some estimations online of how much each activity uses, and you can calibrate that to yourself by, say, walking on a treadmill that you can calibrate. I would say the easiest way to lose weight is physical activity rather than dieting; just eat a healthy diet (veggies, fruit, some dairy, some protein, etc.) and spend a lot of time playing games outside, walking, etc. Awickert (talk) 04:36, 16 August 2009 (UTC)
Come to think of it, when I was more athletic, I used to burn ~6000 calories per day. Of course, that's a little on the intense end, but (since I enjoy food and exercise) I would say that more playing outside and working out is much easier (for me) than less eating. Awickert (talk) 04:47, 16 August 2009 (UTC)
The National Weight Control Registry consists of data about a set of people who have successfully lost a minimum of 30 pounds, and kept it off for a minimum of a year. Of the people in the NWCR, 98% modified their food intake in some way to lose weight, and 94% increased their physical activity.[32] So it is quite unusual to succeed at weight loss in the long term without both modifying food intake and increasing physical activity, but the data suggests that of the two, modifying food intake is the most crucial. Red Act (talk) 08:33, 16 August 2009 (UTC)

Gene Identification

Besides the "knockout" technique what other techniques are used to identify a gene's purpose i.e. genes such and such are for hair and genes xyz are for the color or texture? —Preceding unsigned comment added by (talk) 21:26, 14 August 2009 (UTC)

Probably the most commonly used method is to analyze the gene's DNA sequence similarity to other genes whose functions are known. Looie496 (talk) 21:41, 14 August 2009 (UTC)
You're basically asking for the methods of genetics, molecular biology, biochemistry, cell biology, and physiology. It's a bit too much for one post, but here are some other examples: Genomics studies the organization of the gene and regulatory sequences (this is much easier now with the completion of various genome projects). In the good old days you would clone the cDNA from a gene expression library but this is rarely needed anymore, since most genes have been cloned at this point. Still, it can be interesting to clone alternative splice forms of the gene from different tissues. Gene expression analysis using northern blots, in situ hybridization, or DNA microarrays can show where the gene is expressed and give some idea of what tissues it is important in. Western bloting can be used to study the protein and whether it is post-translationally modified. Various biochemistry techniques are used to study protein-protein interactions. Immunohistochemistry can be used to detect the intracellular location of the protein, which gives some hints about what it does. Cell culture is used to study the gene in vitro. Depending on the initial clues about what the protein does, there will be more specialized methods specific to a given type of protein. People use comparative genetics and model organisms to see if the gene is conserved during evolution which would suggest a fundamental function. Often a gene's family member can be studied in a more simple organism before learning what it does in humans. Transgenic animals use gene overexpression to get information complementary to the knock-out. Ok, that should get you started. --- Medical geneticist (talk) 22:58, 14 August 2009 (UTC)

What about if we had an idea that the genes to make hair color like blonde for example if we knew that it was on chromosome 9, could they with any success study 1000 people who are natural blondes and look for genes that are the same (mostly) to try to uncover the genes involved in creating the blonde hair color? —Preceding unsigned comment added by (talk) 04:31, 15 August 2009 (UTC)

Yes, you can do exactly that type of thing using families, with a technique called linkage analysis; or in larger groups of unrelated individuals using genome-wide association studies. However, one limitation is that although you may find a genomic location that is associated with a trait in a family or in a population, you would still need to do additional work to identify which gene in that area was responsible for the association, and then even more work to prove that the association represents a causal relationship between the gene and the disease/trait. Also, if a trait or disease is complex, the linkage or association studies may only reveal part of the story. --- Medical geneticist (talk) 17:08, 15 August 2009 (UTC)

August 15

Power of gull bites - any data?

Following on from the question above - are there actually any stats available for how much pressure various gull species can bring to bear with their beaks? I just had a quick look on Google but I couldn't find anything useful. --Kurt Shaped Box (talk) 00:20, 15 August 2009 (UTC)

I feel lazy but you can use the information in this paper which is based on finches but includes various data related to gulls to extrapolate. (M. A. A. van der Meij and R. G. Bout. "Scaling of jaw muscle size and maximal bite force in finches." The Journal of Experimental Biology. 207, 2745-2753. 18 May 2004) Also this person may know the answer if you want to contact him. (talk) 02:07, 15 August 2009 (UTC)

executive chair that has a trigger

anyone having knowledge of such a chair please contact me at [email address removed]. I am 80 years of age and probably well never be able to find this site again.

I also do not buy whatever you may be selling so please do not fill my screen with offers.

the chair is constructed entirely of bentwood and steel by a master maker. when the trigger is touched it flies into peices with enough force to knock more than one person down.

I know the history since WWII and it has never been activated in all these years. after using it since 1995 I was walkig by and strcuk it with my walker. my left shouler was bruied very badly, something hit my right arm between the shouler and elbow with enough force to damage the radial nerve so much that I may never have use of my hand.

your will be appreciated. I —Preceding unsigned comment added by (talk) 18:06, 14 August 2009 (UTC)

I copied this from WP:VPM. --Golbez (talk) 00:39, 15 August 2009 (UTC)
I have removed your email address to prevent you getting spammed. We don't respond by email, so hopefully you will manage to find this site again. --Tango (talk) 00:45, 15 August 2009 (UTC)
Could it have been a support spring that snapped, letting some material fly? Nimur (talk) 00:58, 15 August 2009 (UTC)
One-way rocking chair. Cuddlyable3 (talk) 18:27, 16 August 2009 (UTC)

How does evolution work where sexual selection is minimal?

I’m thinking of insects like bees and ants. The queens mate with a single drone which happens to be nearby. How do possibly beneficial mutations occurring in the colony propagate when sexual selection is minimal? With mayflies, there is a virtual orgy lasting a few hours at the end of their lives. How do beneficial mutations work when indiscriminate sexual activity is the norm? Myles325a (talk) 04:39, 15 August 2009 (UTC)

Through other kinds of natural selection? --Kjoonlee 05:10, 15 August 2009 (UTC)
I think you're thinking of the sort of sexual selection where mammals choose mates that appear healthy and fertile; but simple ability to survive and breed is surely a more fundamental driver of natural selection. Also, I'm no entomologist, but are you certain that the sexual activity you mentioned is truly indiscriminate? Tempshill (talk) 06:38, 15 August 2009 (UTC)
Sexual selection was never thought of as the primary mover of evolution; it was used by Darwin and others in order to explain certain things that don't fit well with natural selection. The case of the eusocial, colony insects doesn't fit into the sexual selection model all that well, but that isn't surprising—sexual selection does not always apply, it is a sub-set of natural selection. -- (talk) 15:29, 15 August 2009 (UTC)
Kinship selection is at play in populations such as bees and termites in which most workers share the same genes. Imagine Reason (talk) 20:00, 15 August 2009 (UTC)
Remember : The total number of ants in a colony is a red herring. As is the lifespan of individual worker ants. Only the life-cycle of the queen is important, evolution-wise. Consider that ant colonies have "generations" shorter than human generations, and that most ant colonies are reproduced exclusively through sexual reproduction. So really, sex in ant colonies is not "minimal". They reproduce sexually just as much as we do.
(The queen mates with a male ('for life') then she gives birth to a few daughters and a few sons. The fact that she also gives birth to about a zillion sterile workers doesn't matter.) APL (talk) 05:41, 16 August 2009 (UTC)
Nobody said sex was minimal. They said sexual selection was minimal—competition between members of the same species for the right to reproduce. -- (talk) 18:00, 16 August 2009 (UTC)
Why would it be any less? A queen ant leaves her parent colony to fly around searching for a suitable mate. Male ants similarly leave their parent colonies to fly around searching for a suitable mate. Why would you assume that there's less sexual selection here than with any other insect? APL (talk) 18:37, 16 August 2009 (UTC)

Multiple universe theory proves God exists?

If multiverse theory is true, and every possible universe exists, including many with completely different laws of physics to our own, does this mean that in at least one one of these universes an omnipotent entity (God) capable of moving between universes MUST exist? Incidentally I am an atheist, but I do find the idea of a multiverse plausible. —Preceding unsigned comment added by Trevor Loughlin (talkcontribs) 09:11, 15 August 2009 (UTC)

No. -- (talk) 09:27, 15 August 2009 (UTC)
No is the correct answer. The existence of other universes is metaphysical speculation. It is completely untestable and therefore of zero interest either in explaining things or proving things. On top of which despite being a mainstream Christian (by European standards) I find the idea of God being an entity moving between universes (or moving around at all for that matter) completely absurd. Before you even think about God existing though I suggest you think long and hard about whether you exist and what on earth that means. --BozMo talk 10:54, 15 August 2009 (UTC)
If it is possible to move between them then they aren't really separate universes, in my opinion. But that is semantics, the answer is "no" regardless. I don't know of any multiverse theory (there are several) where different universes have completely different laws of physics, just different fundamental constants and/or different initial conditions and/or different results of random events. --Tango (talk) 11:25, 15 August 2009 (UTC)
And even if they have completely different physical laws, omnipotent concepts of god are logically impossible - as the old "can god make a stone so heavy he cannot lift it?" question illustrates --Stephan Schulz (talk) 11:29, 15 August 2009 (UTC)
Surely it's 'a stone that cannot be lifted by an omnipotent being' that's logically impossible? In any case, such debates have little to do with either physics or the everyday practice of religion. No-one expects their god to go around lifting infinitely heavy rocks, so no-one is bothered by this purely theoretical contradiction. AlexTiefling (talk) 11:39, 15 August 2009 (UTC)
Ex falso quodlibet. Logically, if you have any contradiction in your theory, its inconsistent. But indeed, few people really think about an "omnipotent" god. Usually, they imagine only a very very potent god. Which is why I wrote about "omnipotent concepts of god" (as the original question specified an omnipotent god), not "any god". --Stephan Schulz (talk) 12:22, 15 August 2009 (UTC)
I don't understand the distinction. "God" and "omnipotent being" sound pretty synonymous to me. --Tango (talk) 11:42, 15 August 2009 (UTC)
In a polytheistic context, they're certainly not synonymous. In a monotheistic context, it's substantially irrelevant whether or not they're synonymous. Religious people don't ask if God will create an unliftable rock. They ask 'Lord, will you now restore the Kingdom of Israel?', or 'Which of your Lord's blessings would you deny?'. The idea of interpreting the idea of God in terms of a strict definition of omnipotence has absolutely no resemblance to the idea of God entertained by the typical religious person. There are many criticisms of the 'unliftable rock' problem: If God is omnipotent, why can't he create logical contradictions? If the rock is heavy enough, won't it become a planet/a star/a black hole, such that 'lifting' is a useless concept? This problem no more invalidates the idea of God than the idea of 'the set of all sets that are not members of themselves' invalidates the idea of sets. It's just a juvenile thought-experiment. AlexTiefling (talk) 12:10, 15 August 2009 (UTC)
Sorry, I meant in the context of this discussion. Stephan said "omnipotent concepts of god", so I assumed we were using "god" in a vague Abrahamic sense. There are plenty of alternative definitions of the word. --Tango (talk) 12:27, 15 August 2009 (UTC)
FWIW I think the concept of technically omnipotent is fairly modern (I would hazard 300AD without getting any books down from the top shelf). Of course there are lots of poetic statements in the psalms etc but probably not by people with any concept of what that might mean, just as pre Herodotus the concept of historical statement was dubious. I think "could win any battle" rather than "can win every battle without casualties" or as Stephan put it "very potent" is probably the Abrahamic God. But as Alex has said most people these days are not really there. The question is whether the universe can be understood with reference to a greater being in the same way that a 41 year old lump of flesh can be understood with reference to a person called Stephan. --BozMo talk 15:50, 15 August 2009 (UTC)
AFAIK, Christian and generally Abrahamic theologists have predominantly considered God to be perfect, omniscient and omnipotent in a philosophical sense. The fact that everyday practitioners can't or won't see a problem does not make it disappear. If people have more "modest" requirements and only expect God to be omnipotent in those matters that concern them personally - well, it should at least be pointed out that even this is a very ambitious claim, and that acknowledging some fundamental principles to be independent of God and pre-God moves His image in the wrong direction - towards a giant, ingenious, invisible alien floating somewhere in intergalactic space, subject to the laws of physics and to the occasional headache. -- (talk) 22:18, 16 August 2009 (UTC)
AFAIK no serious Christian Theologian since Thomas Aquinas has had the view you state is "predominant". Pretty much zip. Sorry. --BozMo talk 17:38, 17 August 2009 (UTC)
Well, you see, the problem is that in this respect, Thomas Aquinas was pretty much unchallenged until secularization in the 19/20th century; and no new view on this has really become predominant and "standard" since then. Sure, in the 20th century lots of theologists have been trying to "fix" these attributes in various ways (it's their job, after all), making some modifications to them in order to save the basic idea; some, such as Charles Hartshorne, have even dared dispute some of them. But, mutatis mutandis, the divine attributes remain mainstream and are normally "rescued" in some way or other, because they are essential to the whole business: a God that has defects and limited capabilities and knowledge is simply less competitive on the market. For "omnipotence" one can check, on Google Books, "Almighty God: a study of the doctrine of divine omnipotence" by Gijsbert van den Brink. For "omniscience" - "God, foreknowledge, and freedom" by John Martin Fischer. For "perfection" - "The untamed God: a philosophical exploration of divine perfection, simplicity and immutability" by Jay Wesley Richards. For all three you can see "The Christian God" by Richard Swinburne and "Philosophical foundations for a Christian worldview" by Moreland and Craig.-- (talk) 21:25, 17 August 2009 (UTC)
In addition, here are a few specific citations for the divine attributes remaining mainstream: Christian sources - "Handbook of Christian apologetics: hundreds of answers to crucial questions" by Kreeft and Tacelli, p.72; "The God who risks: a theology of providence" by Sanders, p.194 "Reason for the hope within" by Murray, p.83); neutral sources - "A companion to philosophy of religion", by Quinn and Taliaferro, p.22,56, "Philosophical Inquiry: Classic and Contemporary Readings" by Adler and Elgin, p.877. -- (talk) 22:12, 17 August 2009 (UTC)
I'm a Christian, and I also think the answer to this question is a resounding 'no'. Both the existence of one or more gods, and the existence of one or more alternate universes, are metaphysical speculation. These speculations are entirely independent, and can in principle be made to say whatever an individual speculator wants. Their levels of acceptance depend on their plausibility, and the idea that the one theory is linked to the other seems quite implausible, and certainly has a very low level of acceptance. Ideas of proof and determination don't come into play at all, and I'd question if this is really a 'science' question at all. AlexTiefling (talk) 11:39, 15 August 2009 (UTC)
Modern notions of a multiverse are not metaphysical speculation; they're much more credible than the pseudoscientific claims of religion. Other universes might not be observable, but if a theory like M-theory which predicts them is confirmed to be true, that would be indirect scientific evidence for the existence of a multiverse. Granted, it wouldn't be particularly good evidence and wouldn't convince most people, but any evidence at all places the multiverse hypothesis above the level of religion. --Bowlhover (talk) 15:15, 15 August 2009 (UTC)
What multiverses does M-theory predict? If you define "universe" as a collection of causally connected events (which I would) then, by definition, you cannot make any observations of other universes, so cannot directly demonstrate their existence. --Tango (talk) 16:51, 15 August 2009 (UTC)
IMHO you are right about that Tango. As said twice it is metaphysical speculation and multiple universes is generally an "of the gaps" type argument of varying disguise used to explain extraordinary coincidences in the universe (e.g. dynamics of the big bang was just right: bigger and we would have imploded smaller we would have expanded too fast for planets). A multiverse explains by saying there are zillions of completely isolated big bangs with universes but we can only observe the one which happened to work. Polkinghorne says evidence for a God, some say evidence for mulitverse and inflation offers another theory. But its a rare example in my view of Polkinghorne's logic being flawed (because metaphysical speculation about God's extra-universal role is still metaphysical speculation, we can only look at the observable universe and infer about it). --BozMo talk 18:18, 15 August 2009 (UTC)
A zillion-big-bangs theory is not comparable to the "God of the gaps". A zillion-big-bangs theory assumes that almost the same things that we have already observed may have occurred also in instances which we haven't been able to observe, but abiding largely by the same laws of physics we know. A God theory assumes that something the like of which we have never observed has occurred, abiding by laws that we, with the state of our present knowledge, can't possibly imagine.-- (talk) 22:18, 16 August 2009 (UTC)

Ignoring Omnipotence beyond logical possibility, lets just settle for Q from Star Trek then?

  • I think the conclusion to come to is that the idea of multiple universes can prove or disprove nothing. The "theory" is mostly philosophical postulation and moonbeam-fondling. However, if we wanted to forget about "proving" anything and just do some philosophising, I think it's worth looking to the theology. Many predominant monothesitic religions contend that Everything (note the capital 'E') is presided over by a being somewhat beyond our space, and Judeo-Christianity follows a God that is characterised as incomprehensible and above our reality. In speaking about a deity that is, in a sense, beyond reality, it seems less than meaningful to discuss how its (or His, in the Christian case) existence relates to multiple universes. —Anonymous DissidentTalk 16:01, 15 August 2009 (UTC)
"Only Many Worlds can explain quantum superposition effects" (talk) 19:52, 15 August 2009 (UTC)
Wrong type of multiverse. The Many Worlds interpretation of Quantum Mechanics is about different universes for every "choice" the universe has to make, the kind of multiverse we're talking about is where each universe has different physical laws/constants (and each of those universes could split into a multiverse of the first type). It's possible the two meanings could be combined if the physical laws/constants turn out to be a result of quantum fluctuations in the early universe, I suppose, but I don't believe any such theory has become mainstream. --Tango (talk) 23:47, 15 August 2009 (UTC)

Every possible universe cannot include impossible universes where laws of physics are violated or where every mystical notion is somewhere realized. The OP as a declared atheist seems to be confident about what cannot exist, so maybe the OPs question reflects a longing to find a God. Cuddlyable3 (talk) 18:09, 16 August 2009 (UTC)

Some responses in this thread seemed somewhat abrupt (apparently the OP was judged not to treat the sensitive issue of God with due seriousness, and his thought experiment was suspected of being irreverent or even blasphemous). The last post was probably the least helpful of all (maybe writing that the OPs question reflects a longing to find a God reflects a longing to find someone longing to find a God, and my writing the above reflects my longing to find someone longing to find someone longing... never mind). Also, I think it's obvious that the idea was - if multiverse theory were to be proven, would that prove the existence of God, too? So nobody is expected to dispute multiverse theory itself here. Even under these conditions, and with a risk of repetition, I concur with everybody else that the answer is "no". If multiverse A disallows an omnipotent God and multiverse B allows an omnipotent God, this God's omnipotence would still obtain only in multiverse B, so the one thing he could never do is move to multiverse A and exercize his omnipotence there. Of course, the whole way of posing the question is a little unfair to monotheism, because it presumes that the laws of the universe predate and restrict the divine person potentially operating in it. Monotheism is, in principle, based on the opposite causation: the person comes first. I think this is naturally and intuitively appealing to us humans, taking into account how we grow up and live. In the thought experiment, the God of Multiverse B is only omnipotent because Multiverse B allows him to; since there must be a general set of rules which determine how the parameters or features of any individual Multiverse determine its God-friendliness, it's obvious that there is a more general domain within which these rules hold true, let's call it the Super-Universe, or less reverently - Universe Universe (UU), and within UU Gods are not omnipotent. At all. To obtain an omnipotent God, we need to assume instead that God comes first, s/he is the first letter of the alphabet so to speak, and all sorts of laws, concepts, attributes etc are secondary. Hard to imagine, of course, but not necessarily impossible to accept - it depends on one's motivation.-- (talk) 22:18, 16 August 2009 (UTC)

Well said. But the question itself is an excellent one and can be put in another form that has nothing to do with religion or even deities. One could ask that in a multi-verse system, with an infinite number of universes, where hypothetically anything could exist, including deities or omnipotent or omniscient phenomena, surely there would be scenarios where something from one universe could encroach on another universe? To contribute to the OP's question you could posit that even if a deity/god existed in another universe, surely that would not prove its existence in ours. It's an excellent question, and someone familiar with the philosophy of multi-verses can really answer it. Rfwoolf (talk) 23:24, 16 August 2009 (UTC)
The problem is in the 'kind' of multiverse we're talking about. The one that seems like it might be true (the multiple worlds interpretation of quantum theory) is the one where the laws of physics are the same in all of them. Ergo, no magic to make gods with. Infinitely powerful beings are simply not possible in our universe. If there are other universes with OTHER laws of physics - then indeed, all bets are off. However, if a universe with the right laws of physics to allow there to be gods in it were to exist (whatever that means) - then that's certainly no guarantee that these entities can cross into our universe - because here, our laws don't permit them to exist. But if ANYTHING could "cross" from one universe to another, that would kinda blow away the idea that they are separate universes. If things could cross - you'd think we'd see evidence of peculiar laws of physics showing up all over the place in our universe - and we don't. SteveBaker (talk) 23:34, 16 August 2009 (UTC)
Infinitely anything won't fit into the universe Steve.--BozMo talk 18:23, 17 August 2009 (UTC)
If God (or gods) exists then he must be part of the omniverse (a word I just coined only to discover we have an article on it! I think the definition in there is equivalent to what I mean - it contains everything that exists in the broadest possible sense), that omniverse must have some kind of rules governing it (whether they are rules we are capable of understanding is another matter entirely) and God is subject to those rules. The idea that "God comes first" doesn't make sense - the omniverse has to exist for God to exist. Of course, the omniverse doesn't necessarily has a concept of time (it certainly doesn't have our concept of time), so the ideas of "first" and "cause and effect" doesn't necessarily apply. --Tango (talk) 00:01, 17 August 2009 (UTC)
Ever take a look at Norse mythology? Well, according to Norse legend, the High God Odin is all-powerful -- but only as long as he keeps all his covenants with all his subjects; as soon as he willfully breaks even one covenant, all his power would vanish just like that. Seems just a little like what you're talking about here, as far as your statement that "God is subject to [the rules governing the omniverse]". (Of course, in Norse mythology, Odin and all the other gods are anthropomorphic, which is a very dubious notion to say the least...) (talk) 00:44, 17 August 2009 (UTC)
Yes, that's not a bad example, although it isn't consistent with our theories of physics that isn't really a problem - we know our theories aren't perfect because we don't have a theory of everything. There are gaps (like Quantum Gravity) that we have yet to fill. Valhalla could fit into one of those gaps. (Unlikely, but not impossible.) --Tango (talk) 13:33, 17 August 2009 (UTC)
So Tango do you think YOU fit into one of the gaps, or conscious being with free will generally do--BozMo talk 18:23, 17 August 2009 (UTC)?
As a Christian, I wouldn't say specifically that "Valhalla could fit into one of the gaps", but well, some kind of afterlife could surely be consistent with our knowledge of the universe (and I'm sure that sooner or later, afterlife will be proven to exist beyond reasonable doubt). (talk) 23:28, 17 August 2009 (UTC)
I'm not sure the bit about Odin is true in the original mythology (I've read the Prose Edda and much of the Poetic one, though I may have forgotten something); this reminds me more of the interpretation in Wagner's Ring Cycle, and/or G.B.Shaw's interpretation of that interpretation. Anyway, certainly the restriction to not breaking covenants means that he is not really omnipotent, he is restricted by at least this law, or perhaps even by an entity that imposes the law.
Re:"Odin and all the other gods are anthropomorphic, which is a very dubious notion to say the least". The word "anthropomorphic" is POV-laden, as it literally means (1) "described as being similar to humans to some extent", but in practice is used as (2) "described as being similar to humans to an unrealistic extent", and what is an "unrealistic extent" remains to be debated. I think it's obvious that any god is anthropomorphic in sense (1) - being similar to humans to some extent - and it can be argued that any god is anthropomorphic in sense (2) as well - being similar to humans to an unrealistic extent. —Preceding unsigned comment added by (talk) 15:32, 17 August 2009 (UTC)
By "anthropomorphic" in this context, I meant specifically "so similar to humans as to be indistinguishable from them upon casual observation". This would be true in the case of Norse gods -- or indeed most of the gods from pagan mythology of the European nations -- but in the case of Jehovah, the Judeo-Christian God, this is not necessarily true (and indeed, He is most likely NOT anthropomorphic in this sense). Same with Allah, the Islamic god, according to the Koran he is not anthropomorphic but more like some kind of cosmic force (although I really have to wonder what kind of god would choose a child molester as his prophet, but that's a whole different topic altogether). (talk) 23:47, 17 August 2009 (UTC)
An infinitely powerful god can be anthropomorphic if he/she/it feels like it. You could imagine how that would come in handy. Odin just needed a good lawyer. I'm sure he could find a way to repeal his pact with humanity without breaking the pact in the process. SteveBaker (talk) 21:52, 17 August 2009 (UTC)
Would Loge fit the bill as a "good lawyer"? He was infamous for giving crooked advice -- which is why the other gods didn't really trust him. ;-) (talk) 23:19, 17 August 2009 (UTC)
Tango's argument was that "God comes first" doesn't make sense, because God is inevitably pre-conditioned by the Universe in which he exists. Well, one could argue that God was the Universe in its initial state, and then he created those parts of the Universe that are not strictly speaking part of himself, but still, in view of their origin (he had created them, and being omnipotent, he had created them perfectly in accordance with his purpose), he has retained absolute control of them. In the beginning was absolute Goodness&Wisdom, then It sort of budded or secreted from itself stuff like mathematics, logic, physics etc, so as to finally produce another thing with the potential for goodness and wisdom - namely us humans. I don't think this is logically impossible.
Another possibility is that physics and logic are not even a creation of God, but have been part of God from the start. In this case, the question often asked is: can he then can violate physics and hence his own nature? The answer would be the same as to the question whether he can do something evil: "Yes, he can in the sense of being capable, but he can't in the sense of being likely to do it - because he simply doesn't want to, because he is what he is." So I still stand by the "God comes first" option as the assumption best poised to lead to the desired conclusion. Cheers! -- (talk) 15:17, 17 August 2009 (UTC)
91.148, you should be a theologist. :-) (talk) 23:31, 17 August 2009 (UTC)

All possible paths don't lead to all possible outcomes.... Elocute (talk) 21:54, 17 August 2009 (UTC)

Species of monkey

Monkey eating.jpg

Can anyone identify what species this monkey is?  Chzz  ►  13:55, 15 August 2009 (UTC)

Rhesus macaque? -- (talk) 14:53, 15 August 2009 (UTC)
Crab eating macaque according to --Muhammad(talk) 17:21, 15 August 2009 (UTC)
Sounds painful. Edison (talk) 19:12, 15 August 2009 (UTC)
That must be a big crab if it can eat a whole macaque. --Jayron32 01:48, 16 August 2009 (UTC)

One of those things that you really should know about the human body...

Hi! So, I have a question that you really should have learnt the answer to in high school, but it seems to me that no one did (I've asked five people this, and gotten five different answers). As we all know, men create sperm throughout their life inside their testicles, while women only have a limited number of ova that they get at birth and are stored inside their ovaries (I'm right so far, yes?). Here's my question: on average, how many eggs does a human female have? In total? I've heard everything from a few hundred to a few hundred thousand (which was what I thought, incidentally), with most people guessing at the lower range. Neither the ovum nor the ovary article would enlighten me on the subject.

I would be most thankful if you fine fellows could make up for the collective failure of me and my friends' human biology education and provide me with an answer. Cheers! (talk) 17:43, 15 August 2009 (UTC)

It depends, and we may be wrong. Women do not have a store mature ova, but rather progenitor cells. The number of these decreases over time, but there are apparently several million of them. See Oogenesis#Number_of_primary_oocytes. In other words, women don't "run out of eggs" in menopause. --Stephan Schulz (talk) 18:02, 15 August 2009 (UTC)
The same article sited above also states
Recently, however, two publications have challenged the ovarian biology dogma that a finite number of oocytes are
et around the time of birth.[4][5] Renewal of ovarian follicles from germline stem cells (originating from bone
marrow and peripheral blood) was reported in the postnatal mouse ovary.
Due to the revolutionary nature of these claims, further experiments are required to examine the dynamics of small
follicle formation.
So may be the premiss of the question is incorrect. Dauto (talk) 21:40, 15 August 2009 (UTC)

Human presence detection technique

Hello! I'm presently working on a personal project which would require me to detect human presence in a room of 35'x20'x12'(l x b x h),as part of my objective. I've in mind PIR sensors but i'm afraid they might not respond accurately at ambient air temperatures over 40oCelcius. Is there any alternative way of detecting human presence in a room other than PIR? P.S. Capacitive method is not viable as room houses multiple em radiating sources. And passive millimeter-wave (MMW) sensors are seemingly over my expertise grade it would seem.

A THANK YOU before hand to whoever might help me figure this problem out. —Preceding unsigned comment added by LONGBOW001 (talkcontribs) 20:29, 15 August 2009 (UTC)

Is a computer and webcam(s) an option to try? There already exists a program called motion (also in debian repositories) that lets you define commands to run when there's motion in video camera image. -- (talk) 20:54, 15 August 2009 (UTC)
To properly solve this problem, you need to define some environmental conditions. You want to detect a human, but what other things are going to be present that you need to avoid detecting? If warm objects will be present, infrared or thermal detection will have an unacceptable false-positive rate. If other animals or pets will be present, you need to identify a human distinctly from, say, a cat - or whatever else is in there. If you want to identify a specific human, you might need facial recognition software or some other biometrics. If you are willing to have the human actively participate in the identification process, such as by wearing an RFID tag, this can simplify the process. Nimur (talk) 21:42, 15 August 2009 (UTC)
Have you considered using a petoscope? (talk) 04:54, 16 August 2009 (UTC)
Pressure-sensitive mats. Cuddlyable3 (talk) 17:51, 16 August 2009 (UTC)

Candle pendulum

What is going on in this video? --Reticuli88 (talk) 20:42, 15 August 2009 (UTC)

The side of the candle that is lower will dump the hot wax. The side that is higher will hold the hot wax. Because the lower side dumped the hot wax, it is lighter. So, it rises. Then, the lower part dumps its wax. The higher part does not. So, the lower part becomes lighter and it rises. Another way to imagine this is a see-saw with a bucket on each end. If the bucket is lower, the water will dump out. Now, continually fill the buckets with water. The lower one will dump out the water while the higher one fills up with water. The higher one will lower and dump the water. You can also toss in a bit about one end of the candle getting shorter but I seriously doubt that has much effect compared to the loss of volume by dumping out the hot wax. -- kainaw 21:01, 15 August 2009 (UTC)
Unless that's a really volatile candle, I suspect we're also seeing some time lapse imagery - the burn rate and oscillations look like they're sped up somewhat. Nimur (talk) 21:46, 15 August 2009 (UTC)
Not just dripping either, (Most candle wax winds up in the air.) Notice how the flame cuts into the candle more on the downward side. I assume that wax is consumed faster on that side. APL (talk) 05:32, 16 August 2009 (UTC)
The right end is lit first and starts losing weight before the left is lit, so the candle initially tilts anticlockwise. The tilt then stabilises because the left flame is angled more towards the wax body and so melts it faster. Now both ends burn in an unusual sudeways mode. Note that the flames bend towards the center. We can't see the whole airflow but hot air must rise from the flames and be replaced by cool air from beneath. Two circulating airflows close together generate more friction than a single flow, therefore the former is not stable and there is turbulent combination of the flow modes. A slight imbalance in the turbulences tilts the candle. This has a regenerative effect at the physical resonant frequency of the see-saw where the air disturbance of the candle body adds to the thermal disturbances of the flames. The oscillation of the candle builds up so it becomes obvious that the two flames are alternately contributing to the same upward convection. Factors contributing to the oscillation are the flames alternately burning into or away from the candle body, and possibly (not visible) molten wax running down the gutter at the lower end and dropping off, making that end lighter.Cuddlyable3 (talk) 17:42, 16 August 2009 (UTC)

Faraday Cage

I've always thought that microwaves were Faraday cages. I saw a demonstration where they put a radio inside a Faraday cage (it wasn't a very good one but somewhat effective) and naturally the radio quality turned to shit. I was wondering why when I put my phone in the microwave oven and close the microwave door (naturally not turning on the microwave) my phone still could receive calls (I called it and it rang). I thought the whole point of a Faraday cage was to shield the objects inside. Thanks (talk) 20:53, 15 August 2009 (UTC)

The mesh on the front panel of the microwave (that let you see in) are calibrated to be just the right size to keep the microwaves inside. Signals at different wavelength can pass through it, though. (Which is why you can see through it—visible light can pass through easily). I imagine that the cell phone wavelengths are more varied than the microwaves' and can make it through. -- (talk) 21:05, 15 August 2009 (UTC)
We discussed this in December 2008. My excellent response was so fantastic that nobody else even needed to follow up on it! I will copy it here for your reading pleasure: Nimur (talk) 21:49, 15 August 2009 (UTC)

The question you are asking is, roughly restated, "does the microwave have a shield?" It should be more properly restated, to be very precise, as "What is the non-linear anisotropic attenuation-vs-frequency characteristic of the microwave casing, and what frequencies of attenuation overlap those frequencies used by the cellular phone?" First of all, let's clarify a few details:

  • Microwaves and cell phones commonly do operate at the same or similar frequency band (for example, 2.45 GHz). But, maybe your microwave and cell phone operate at different frequencies... it depends on whether your phone uses GSM, where you bought your microwave, etc. You can check this with the marshmallow test, or if you're smart, just read the label on the back of the microwave oven.
  • Microwaves commonly include a few features, such as a wave guide or horn to guide the microwave energy in a specific direction (towards the food)
  • After the microwave energy is "in the oven", it bounces around, off the walls, maybe even setting up resonant waves. So, any "shielding" should really be surrounding the entire oven, with strongest protection at the places of strongest electromagnetic fields (typically, directly opposite the "horn" where the waves come in.
  • Microwave ovens probably use a "crappy" but generally single-frequency tonal magnetron to create the electromagnetic waves. So, the shielding is quite probably a "notch filter" (isolating out that single frequency and preventing it from passing).
  • By the second law of thermodynamics, any (passive) shielding should be bidirectional - that is, if the energy can't get out, then energy can't get in, either.
  • Shielding is also not measured as "all or nothing" - it's measured as an attenuation. That means that the shield lowers the intensity of the radiation, but does not make the signal disappear completely. Now comes the non-linear part. The case in consideration compares two very very very different orders of magnitude - nearly one kilowatt of oven radiation, blasting from eight inches away, compared to a few milliwatts transmitted by the phone and maybe nanowatts (picowatts even!) received from the tower. (Depending on "details," your phone may need bi-directional communication to initiate the reception of a call; or it may just need to receive a single incoming message from the tower). So it may not be safe to say that the shielding materials attenuate by a fixed amount over this entire range of power levels. It's possible that very-low intensity signals, like those from the phone, are not attenuated much at all; while high-power signals are brought down to safe intensities (and no further)
  • Cell phones use very complicated modulation to make sure that the data can be deciphered even when the signal is very very weak. This is what advertisers often mean when they say "fewer dropped calls" (though they might also be talking about density of towers). Specifically, some of the QAM spread-spectrum coding schemes are particularly insensitive to single-frequency interferers. So if the So even if the microwave shielding is "pretty good" at notching out (stopping) that single frequency that the oven operates at, the cell phone data may be fairly undeterred.
  • And the anisotropic part makes a huge difference! The cell-phone probably has a crummy antenna, which may mean it has a weird angular reception pattern. And, the microwave oven shielding is probably not uniform either (presumably concentrated on blocking regions of highest radiation while cooking!) So, if you rotate the phone, you may get dramatically different reception patterns. And this is totally assuming that there is no resonant coupling between the 2.4-GHz resonant chamber of the oven, and the 2.4-GHz dipole antenna inside the phone. Who knows what may happen to the reception pattern if that effect is non-negligible! In summary, the orientation of the phone with respect to the oven, and the orientation of the oven with respect to the nearest tower, will dramatically change the results. (see Radiation pattern for more graphical explanation).

So, it can actually be fairly complicated to say whether a given microwave will "shield" a given cell-phone from a call. Irrespective of the result of that test, it is not really a good way to determine whether the oven casing effectively blocks out the microwave energy used during cooking. Nimur (talk) 17:00, 10 December 2008 (UTC)\

Thanks for that excellent response Nimur. As for the microwave blocking the microwave energy I sure hope so because alot of times I put my head next to the microwave to watch the food that I'm heating up so if the casing doesn't I'm screwed I guess... :) (talk) 23:41, 15 August 2009 (UTC)
Thank you Nimur for the pleasure of reading your fantastically excellent response. But the marshmallow test won't tell anything about the cell phone operating frequency. And where does your hypothesis that the oven shielding is non-linear come from, when this implies there is some material change, ionisation or arcing somewhere? By spread-spectrum modulation I think you mean CDMA not QAM. If you want the OP to investigate the effects of orienting the phone and oven, the attention should be directed to the received signal strength indicator in the phone (if it has one) rather than just whether it receives a call. The OP may be reassured that the screening is adequate by checking whether a moist rag held close to the operating oven gets warm (it shouldn't). Cuddlyable3 (talk) 16:42, 16 August 2009 (UTC)
As far as the mobile phone operating frequency, the best way to check that is to look for a label. Inside my mobile phone, underneath the battery, is a bunch of FCC information, and I can see that my phone operates at either 900MHz or 1.8 GHz. You can also check this stuff on the web, this website applies to my phone model. As far as the non-linear attenuation, my assertion is that everything, including simple stuff like dielectric "constants," are inherently nonlinear, if you analyze them over a large enough experimental range. This Google Scholar search indicates active research into such material-dependent nonlinear attenuation; it seems I may be on the right track here. Though material-changes can be responsible for nonlinear behavior, they aren't the only reason why a measured value might deviate from a simple constant. A cursory glance through some research papers suggest that atomic structures and crystal lattices in the material may play a role. Regarding the phone's signal strength meter: I don't know about your microwaves, but mine doesn't have good visibility to the interior, so I doubt that I could read the phone's signal-strength indicator; anyway, it's hard to know exactly what that readout means (there can be time-averaging; digital post-processing, etc). Nimur (talk) 17:44, 16 August 2009 (UTC)
Nimur your Nokia mobile phone is a standard model for GSM which uses TDMA and FDMA (not spread spectrum). It has a received signal strength display that is averaged over 5 to 10.5 seconds (see RXLEV[33]). The display is in logarithmic steps (decibels) exactly defined in the ETSI GSM specifications. Microwave ovens are usually internally illuminated and your phone display should be legible in some positions looking through the door grille. As the OP says, microwave ovens are constructed as a Faraday cage of steel without "exotic" materials. Alleged non-linear attenuation by this cage would imply that a significant fraction of the heating power typically 600W is absorbed by something other than the food. Asserting that everything is nonlinear doesn't quantify anything here. Cuddlyable3 (talk) 20:25, 17 August 2009 (UTC)

Musical tastes and mental health diagnosis

Can musical tastes be a factor in diagnosing a mental illness or absence thereof? NeonMerlin 23:26, 15 August 2009 (UTC)

It looks like there has at least been some research in that area, yes. E.g., see the papers "Clinical diagnosis by the IPAT music preference test"[34] and "Can music preference indicate mental health status in young people?"[35] Red Act (talk) 07:57, 16 August 2009 (UTC)
I'd imagine so in many cases of anhedonia.Mo-Al (talk) 08:03, 16 August 2009 (UTC)
You may want to check Oliver Sacks´ book "Musicophilia: Tales of Music and the Brain". --Cookatoo.ergo.ZooM (talk) 08:11, 16 August 2009 (UTC)

Feeling tired when hiking, resting, then continuing

Why do humans need to rest? What good does it do? Why cannot the body just keep on supplying the energy at a constant rate without needing rest periods? And, when you are on a long hike or march, has anyone found out the optimum length and frequency of rest periods? (talk) 23:49, 15 August 2009 (UTC)

There are two consumers of energy -- one is the nervous system (via the action potential), and the other is the ATP-driven motor that contracts the muscle fibres. The action potential is instantaneous, releasing electrochemical gradients a bit at a time to send signals -- but if you send a lot of signals you can deplete this potential. (Sometimes you need hours to restore the gradient to full strength again, because the gradient is restored by ion pumps that pump ions one ion at a time.)You can deplete the supply of ATP within cells while blood sugar is abundant, because it takes time for the cells to absorb the sugars, metabolise it via oxygen as a terminal electron acceptor, and make ATP with it. Also, fatigue is partially a safety mechanism. The body doesn't wait till cells are completely depleted of ATP -- you'd collapse, not to mention that cells need energy to stay alive (pump in certain ions/nutrients, repair damage to DNA, membrane holes and other materials) and running out of ATP would be bad. Imagine if the body simply allowed you to walk until your heart and lungs gave out? John Riemann Soong (talk) 01:20, 16 August 2009 (UTC)
As for your last question: back during the Civil War, Stonewall Jackson had his troops march for 1 hour, then rest for 10 minutes before continuing the march for another hour, and repeating this cycle until either the troops reached the objective, or had to stop for the night. This worked really well, so I'd say that 1 hour march / 10 minutes rest would be close to optimal. FWiW (talk) 05:06, 16 August 2009 (UTC)
A lots of exercise routines use similar cycles. 20 minutes exercise and 1 minutes rest, repeated, for example. It does seem to be effective to have short breaks every so often - the important thing seems to be resting before you reach your limit. --Tango (talk) 16:19, 16 August 2009 (UTC)
The other thing that can cause a need for rest is running out of oxygen in the relevant muscles so they have to use anaerobic respiration and get a build up of lactic acid, your muscles will then start to hurt and you eventually have to stop. That should only happen for high intensity exercise, though, I doubt hiking would cause it. It is more of a problem for 400m runners, or something. --Tango (talk) 16:19, 16 August 2009 (UTC)

August 16


in niobium, what can be the possible orbital arrangement? i think it should be - 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d3

but in my book the last two are - 5s1 4d4

which one is correct and why (the half-filled orbital concept can't come here as d3 isn't half-filled)? —Preceding unsigned comment added by (talk) 02:59, 16 August 2009 (UTC)

The huristic you have learned to fill electron orbitals in order is only an approximation, the actual filled orbitals will differ slightly. The "half filled" rule which applies to Chromium and Copper are an attempt to "justify" variations from the strict rules. Remember that the electron filling rules are a human invention, and that the elements themselves were not necessarily informed of the rules; even if they were they are not bound to follow them. If you are trying to get a homework problem right, you should probably just follow the rules and use the expected 5s2 4d3 configuration. The actual configuration has been experimentally confirmed to be 5s1 4d4 since it better explains niobium's +4 oxidation state (see Niobium); a state that would be unlikely to exist if the configuration were 5s2 4d3 (where you would ONLY expect the +3 and +5 states). Just remember that real, physical data will sometimes contradict the little games we invent to explain electron configuration. The standard orbital filling model works MOST of the time, with a few notable exceptions. The "half-filled" rule your teacher taught you is a kludge designed to explain away elements like chromium and copper; niobium cannot be explained away by anything except "the model does not work for that one". --Jayron32 03:51, 16 August 2009 (UTC)
The rules are a simple generalisation of the Schrodinger equation so you don't have to perform Hartree-Fock equations every time you want to estimate how orbitals are filled. John Riemann Soong (talk) 21:03, 16 August 2009 (UTC)

Chirping transformer

Why is the power adapter of my computer chirping like a bird, at a rate of roughly 1 chirp per second? Yes, I know it's malfunctioning; I just want to know how the malfunction is causing it to chirp. -- (talk) 03:11, 16 August 2009 (UTC)

Does it have a built-in fan? (Most desktop power supplies do.) Probably the fan is wobbling slightly. That can produce very regular "chirping" noises. APL (talk) 05:33, 16 August 2009 (UTC)
No, this is a laptop adapter. I'm sure the sound is coming from the power adapter, not the laptop itself. -- (talk) 06:09, 16 August 2009 (UTC)
Switched mode power supplies can make a noise ,probably due to varying forces on components (capacitors etc) as an input voltage is chopped to maintain output voltage.
Is it very loud? (talk) 12:16, 16 August 2009 (UTC)
I would suspect a capacitor is about to fail, or a capacitor has already failed, and there is a new resonant frequency in the supply. Not much should be happening at 1 Hz in an AC-DC power supply - low frequencies typically involve the large, front-end holding capacitors, but those usually are calibrated for kilohertz-ish time constants. Unfortunately it's very hard to diagnose; capacitor failure doesn't always leave any visible signs. Another possibility is that there is a short circuit somewhere in your load (on the computer motherboard) and the failsafe shutdown (if your PSU has one) is triggering at 1Hz and immediately restarting. Nimur (talk) 18:40, 16 August 2009 (UTC)

Capacitance and materials

I'm currently learning about capacitors, and trying to understand the concept of capacitance. Is it dependent upon the material which the capacitor's plates are made out of? Mo-Al (talk) 08:02, 16 August 2009 (UTC)

No but it depends hugely on the material between and around the plates and the area of the surface. --BozMo talk 08:06, 16 August 2009 (UTC)
Also the geometry(shape and size) of the capacitor.[[36]]--Leon (talk) 14:34, 16 August 2009 (UTC)
Capacitance. Cuddlyable3 (talk) 16:08, 16 August 2009 (UTC)
Well, of course the plates have to be made of something pretty highly conductive, e.g., a metal. And the number of free electrons has to be sufficient. But those are very minimal requirements. Looie496 (talk) 17:53, 16 August 2009 (UTC)
So does this mean that two capacitors that are of the same shape, and have the same dilectric, but whose plates are made of different (conductive) materials will have the same capacitance? Mo-Al (talk) 19:04, 16 August 2009 (UTC)
Sure, to within a reasonable accuracy. But when you try it in the lab in my experience if the dilectric is ionic it is difficult to eliminate battery effects as well and they are obviously dependent on the metal. So don't try and prove it as a school physics project unless you are incredibly careful--BozMo talk 19:41, 16 August 2009 (UTC)
A spelling error shall be stamped out with extreme prejudice before the infection spreads further. The word is DIELECTRIC. Cuddlyable3 (talk) 22:09, 16 August 2009 (UTC)

Cast iron stove paint

I am really after someone who know about paints. Sorry that the story is a bit long. I live in a cool climate (UK) with an (old) outdoor swimming pool. Since I have effectively unlimited free wood (I burn about 6 tonnes a year heating the house) I built a bonfire boiler out of scrap lying in the garden to heat the swimming pool. It cost around 50 USD to do and works pretty well (200 degree litres a minute) and over a few days makes an impact on the pool so I am keen to prolong its life. The top part of the boiler (hood and chimneys basically) is made from an old broken Victorian cast iron "Loughborough" boiler and weighs about 150kg. This cast iron has been outside in all weathers for at least a century (it was left under a tree in our garden along with a Victorian bathing hut and all sorts of nonsense) and is still mainly sound. This top piece sits above a steel pipe circulating heating fluid and is double skinned. Nonetheless to get good heat transfer I routed the fire vents through the skins on the way to the chimney and the outside surface of it gets pretty hot. Once I started using this boiler I noticed the rate of rusting of the cast iron had accelerated considerably presumably because the heat was stripping off protective layers. I tried cleaning it and putting two brands of "stove paint" on it but each only lasted one cycle of burn-rain-burn. So I tried "Hammerite" which weathers incredibly well on other iron/steel but had already discolored and I guess is degrading. Questions (1) is there some kind of enamel paint which would do better in rust-heat-rain (2) is it worth trying to cover the Hammerite with stove paint on the basis the degrading requires contact with air and the stove paint might well have failed because of a rusting process under the paint (3) do any primers survive this kind of heat? Hammerite and stove paint both say don't prime (4) Any other ideas? I could I guess cover the whole surface with fire cement but that would be a bit ugly and it is not clear to me if that would survive either. --BozMo talk 08:05, 16 August 2009 (UTC)

Please give the price in pounds. You are British, live in Britain, and many readers here are British. (talk) 10:45, 16 August 2009 (UTC)
How is that of any relevance to the question? --antilivedT | C | G 10:48, 16 August 2009 (UTC)
It is relevant to the question because the OP is British, lives in Britain, and many readers here are British, yet strangely has not given the amount in British currency. (talk) 13:05, 16 August 2009 (UTC)
More British people understand foreign currencies than the other way round. Say 30 guineas anyway. --BozMo talk 14:39, 16 August 2009 (UTC)
He can quote the cost in dollars as well as pounds to be polite to both our British and our American chums. I'm sure he did not pay the costs in dollars. (talk) 17:00, 16 August 2009 (UTC)
He may quote prices in any currency he likes. Local or foreign, common or obscure. We do not need self-appointed culture police running around telling people to be true to their home currency. APL (talk) 18:32, 16 August 2009 (UTC)
1)Perhaps you can put a roof over the entire contraption to keep it dry? 2)You can also try to add a zinc sacrificial anode. 3)I have no idea if you could galvanize the thing. -Arch dude (talk) 11:15, 16 August 2009 (UTC)
(after research) take a look at Electroplating#Brush electroplating. -Arch dude (talk) 11:33, 16 August 2009 (UTC)
The problem with galvanizing I think it the heating. When I have had galvanized garden incinerators in the past the galvanization tends to strip as soon as they are in use. And in case our friend above protests about a Brit using US spelling unusually "z" in these words is correct usage in British English as always practiced by the Cambridge University Press (even though some Brits use s also). --BozMo talk 14:39, 16 August 2009 (UTC)
The OPs problem is similar to that of painting a car exhaust system. Look at [37]. Cuddlyable3 (talk) 16:03, 16 August 2009 (UTC)
You could try going to a car parts store and buying the stuff you use to paint car engine parts with. It's generally resistant to pretty high temperatures - check what it says on the can. SteveBaker (talk) 23:18, 16 August 2009 (UTC)
Another suggestion from the field: You need to get every last speck of rust off the original piece, and whatever you put on as the first coat over it has to "bond" to the bare iron. Inquire of a really old-time "plumbing and heating" contractor -- you're looking for guys who work on steam heating systems rather than "heating and air conditioning" guys, who are just sheet metal benders -- and ask who they subcontract (or hire out?) radiator refinishing to.
That said, however, it is possible that the temperatures at which your're working are just too high for any kind of paint. The same guys could probably advise you on that!
For the record, it doesn't matter at all whether the price is quoted in pounds or dollars or won :-)
--DaHorsesMouth (talk) 02:25, 17 August 2009 (UTC)
What is the conversion between pounds, bob, and guineas? U.S. hardware stores (iron mongers to Brits) sell high temp paints which seem to last better than what you report. They are intended for barbecues. I believe Rustoleum sells "Barbecue Black." Also look into paints used on steam locomotives. Edison (talk) 03:49, 17 August 2009 (UTC)
1 guinea = 1 pound + 1 bob
1 pound = 20 bob
1 bob = 1 shilling
--TammyMoet (talk) 13:35, 17 August 2009 (UTC)

Does exercise make people less drunk?

I alcohol can be used as a source of energy by humans. Does that mean you can " burn it away " by doing exercise? In other words: if I'm drunk will I be sober faster if I jog a few kilometers? (providing of course that I am still able to walk properly)PvT (talk) 11:01, 16 August 2009 (UTC)

Not really ... alcohol isn't like blood sugar, and it isn't a "preferred carbohydrate". See Ethanol metabolism#Thermodynamic_Considerations. Where the metabolism of sugars and the metabolism of alcohol merges is when they are converted into an acetyl group and bound as a thioester with coenzyme A to form acetyl-CoA. The first step of ethanol metabolism involves its conversion into acetaldehyde, and this *costs* energy (it's endergonic). Arguably, this is the "slow step" of the reaction, and why it takes so long to clear ethanol from the body. Unlike glycolysis, this first step doesn't give you any payoff, so less incentive for the body to use it. There's some minor payoff when acetaldehyde gets converted into acetic acid, but this is quite small compared to say, the decarboxylation step of pyruvic acid metabolism, in the oxidative metabolism of sugars (where a whole molecule of carbon dioxide is released).
The really big payoff of ethanol metabolism is when acetic acid is converted to acetyl-CoA and then the oxidised into water and carbon dioxide. But the sheer majority of ethanol never gets converted into an acetyl group on acetyl-CoA ... it gets converted to acetic acid which is then filtered out by your kidneys. Alcohol is treated as a toxin in your body. Unlike say, glucose, which enter the cell via special glucose channels, there are no special "alcohol channels" to allow ethanol molecules to pass through cell membranes ... say muscle cells. So what happens to alcohol in the bloodstream? It must be processed by liver cells who allow toxins to pass through them so enzymes can process them. (Liver cells get regularly killed by all this toxic waste handling of course, which is why your liver is one of those special organs that can grow back.) What will liver cells do with acetic acid? Probably nothing -- they aren't the ones doing the muscle work. They die, get recycled, the acetic acid ends up in your kidneys and it's passed out as urine (after you drink lots of water to allow renal excretion).
Note you really can't do anything to increase the rate of BAC removal ... you can do symptomatic things that make you feel somewhat better, but the only way to increase the rate of BAC removal is to increase the efficacy of your liver cells. (gene enhancement ... better enzymes ... more liver cells... etc.) And of course if you regularly poison your liver cells, your liver will slow down as well. Furthermore, alcohol is such a minor carbohydrate that even if muscle cells did metabolise alcohol, when you exercise you'd be mainly using sugar, and once in a while, every 100 ATP cycles or so, alcohol would be picked to be metabolised (if muscle cells would use alcohol at all). Alcohol metabolism evolved as a means of dealing with the alcohol toxins of bacteria, not for energy processing. It's probably very good that your muscles don't try to metabolise alcohol -- muscle cells don't grow back as easily as liver cells, you see. John Riemann Soong (talk) 13:46, 16 August 2009 (UTC)

See also Ethanol metabolism#Common_Misconceptions. "There is a common misconception that drinking alcohol leads to weight gain. This has never been proven in the literature and is the subject of ongoing debate among experts..." John Riemann Soong (talk) 13:47, 16 August 2009 (UTC)

On an episode of MythBusters, they concluded that is was plausible that exercise could help lessen the effects of alcohol: MythBusters_(2008_season)#Stone_Cold_Sober —Preceding unsigned comment added by (talk) 13:53, 16 August 2009 (UTC)

I think the effect is purely symptomatic. Receiving vigourous nervous system input of course, would be a stimulatory effect that could potentially alleviate the neurodepressive effects of alcohol if the right stimulation is applied. Besides, breathalyser tests aren't really that reliable as blood tests. (The first can only be used as a reasonable warrant for an arrest. You need a blood test to secure a conviction.) I have no idea why getting slapped in the face will lower your BAC. John Riemann Soong (talk) 13:58, 16 August 2009 (UTC)
A simplistic guess would be: slap in face → anger / increased sympathetic activity → increased blood flow to liver → increased ethanol metabolism.
Did they definitely say that BAC lowered after being slapped in the face though? and was it statistically significant? --Mark PEA (talk) 15:46, 16 August 2009 (UTC)
It's a bit more complicated than that. Alcohol, along with benzodiazepine and barbiturate tranquilizers, has effects on the brain that are strongly arousal-dependent. The underlying causes are not fully understood, but the effect is so strong that a dose can be fatal if the subject falls asleep but survivable if the subject is kept awake by slapping, cold-showers, etc. The concentration of the drug in the blood doesn't change much, but the way the brain responds to it does. Looie496 (talk) 17:50, 16 August 2009 (UTC)
What I have taken away from this thread is that if I am ever stopped for suspected driving while intoxicated, after consuming a few beers, and told that after some period I will be tested for blood alcohol, my best strategy is to continuously slap myself in the face, while avoiding other forms of exercise. Has anyone tried this? Edison (talk) 03:44, 17 August 2009 (UTC)
Actually, you should do nothing at all, allow yourself to test positive, be convicted, and lose your licence. This is the smartest thing to suggest to anyone stupid enough to drive while intoxicated. On the other hand, when you show up black and blue from having slapped yourself repeatedly, you could create a diversion by claiming you were beaten by the cops, ;-) Maedin\talk 11:59, 17 August 2009 (UTC)
That would be a utilitarian's opinion on what to do. Most people, however, care more about themselves than other people, so the prospect of having one's licence revoked, losing one's job, etc. is not favorable, therefore they will choose to slap themselves. --Mark PEA (talk) 16:25, 17 August 2009 (UTC)

Does a compressed spring weigh more than an uncompressed one?

Einstein established an equivalence between mass and energy with E = mc^2. If energy and mass are thus equivalent, this means it makes sense to talk about the total "mass-energy" of a particular system, in that a body's mass is actually the total energy contained within.

Does this mean that a compressed spring, since it stores potential energy, will weigh more than an uncompressed (but otherwise identical) spring? (talk) 12:44, 16 August 2009 (UTC)

Yes exactly, it has more mass. Dmcq (talk) 12:55, 16 August 2009 (UTC)
Really? Then does a rock have more mass when I hold it over my head than it does when on the ground? Wikiant (talk) 12:59, 16 August 2009 (UTC)
Ever so slightly. The energy of the rock is many times (many orders of magnitude) greater than the 10 J or so you gain by holding it over the ground. In a compressed spring, what you are doing is pushing atomic nuclei ever so slightly (this is elastic deformation)) beyond their optimal distances, and this stores energy in the form of greater electrostatic repulsion. In effect this makes the nuclei and the electrons ever slightly more massive, but the difference is so miniscule it cannot be measured reliably. John Riemann Soong (talk) 13:13, 16 August 2009 (UTC)
Hmmm. Are you sure about the rock? I can see the spring, easily. But the rock gains potential energy, and that energy is no really inherent in the rock, but depends on the gravitational field of the rock and the Earth. By Chuck-Norris-symmetry, if you lift the rock, the Earth should also gain mass. Does it gain more or less than the rock? Or the same? Or does this depend on the observer? --Stephan Schulz (talk) 14:32, 16 August 2009 (UTC)
I mean, I really should say the Earth-rock-lifter system. Separating masses attracted to each other is like separating attractive charges. I really don't know a lot about relativity, but my impression is that rest mass doesn't increase, so who gains the increased mass is indeed observer-dependent. John Riemann Soong (talk) 14:38, 16 August 2009 (UTC)
But that suggests that, as the rock moves an infinite distance away from the earth, the earth-rock system approaches infinite mass, no? Wikiant (talk) 15:47, 16 August 2009 (UTC)
You only need a finite amount of energy to reach escape velocity. Dmcq (talk) 16:27, 16 August 2009 (UTC)
And that's because of the inverse square law ... as masses separate the gravitational attraction between them rapidly decreases. John Riemann Soong (talk)
The compressed spring is used as an example in our article on mass–energy equivalence, which says "A spring's mass increases whenever it is put into compression or tension. Its added mass arises from the added potential energy stored within it, which is bound in the stretched chemical (electron) bonds linking the atoms within the spring". Chemical bonds are electrostatic, so the additional energy/mass is stored in the electromagnetic field. Similarly, when you lift a rock, the additional energy/mass is stored in the gravitational field. Gandalf61 (talk) 14:54, 16 August 2009 (UTC)
A field has mass? A spring weighs more when it is compressed? Cuddlyable3 (talk) 15:45, 16 August 2009 (UTC)
You've got it. Energy is put in to lift a rock. That energy has an associated mass and the gravitational field gains that amount of mass when the energy is used to lift the rock. So if the spring is used to lift the rock the spring loses mass but the whole system still has the same amount of mass. Dmcq (talk) 16:25, 16 August 2009 (UTC)
I'm sorry, but this isn't making sense. I've heard two contradictory statements: (1) increase the distance between rock and earth and the earth-rock system gains mass, and (2) as masses separate, gravitational attraction decreases (implying that the potential energy of the rock declines and therefore the mass of the earth-rock system decreases). It appears that, as the rock-earth distance approaches infinity, the mass of the system approaches infinity if (1) is true and zero if (2) is true. Which is it? Wikiant (talk) 18:39, 16 August 2009 (UTC)
The error is "gravitational attraction decreases, implying that the potential energy declines." The correct statement is that as they separate, the gravitation attraction decreases, therefore the potential energy increases more slowly. What you have to remember is that the potential energy you add to a rock by lifting it depends on the total work you did to lift it -- the higher you go, the more potential energy it has. That's why it does more damage if you drop it from 50 feet than if you drop it from 5 inches. If you lift it so high that gravity is noticeably weaker, that doesn't change the fact that you're still adding potential energy as you lift it further -- you just aren't doing it as fast. --Anonymous, 19:03 UTC, August 16, 2009.
And as for (1) vs. (2), neither one is true. The correct statement is that as the potential energy (and therefore the mass) increases more and more slowly, it asymptotically approaches a limiting value. Specifically, the most energy you can add to a rock (more precisely, to the Earth/rock system) by lifting the rock away from the Earth's surface (all the way to infinity) is GMm/r, where G is Newton's gravitational constant, M and m are the masses of the Earth and the rock, and r is the Earth's radius. (See under potential energy.) This corresponds to a mass increase of GMm/rc², which if I calculate correctly comes out to about something on the order of 1/1,000,000,000 of the rock's mass m. --Anonymous, 19:10 UTC, August 16, 2009.
Excellent! Thanks. Wikiant (talk) 20:09, 16 August 2009 (UTC)

But does this mean that if two linked springs were rotated around each other (in outer space),and one was compressed during half of the cycle, wouldn't the center of mass alter to allow a (very weak) reactionless drive to be created, in violation of Newtons third law of motion!?Trevor Loughlin (talk) 02:56, 17 August 2009 (UTC)

Please understand that a spring powered clock theoretically gains mass when you wind it, just as a grandfather clock with a weight to power it gains mass when you elevate the weight. If I accelerate my car to 125 miles per hour (200 km/h), as I did in my misspent youth, it also gains mass, but no practical scale could ever measure the mass increase. It would be many orders of magnitude smaller than the resolution of practical scales. In cyclotrons, the mass increase of the particles accelerated to an appreciable fraction of the speed of light has to be taken into account or the devices would not work. We can confirm relativistic mass increase, experimentally, in extreme cases, but we cannot observe it in everyday situations. Edison (talk) 03:39, 17 August 2009 (UTC)
As for what Trevor said if your spring setup is what I think it is (so that when one spring is compressed the other spring is stretched) to me it seems it wouldn't work because (besides the whole violating the 3rd law part) when you stretch a spring 1 m you store the same amount of energy as if you compressed it 1 m, so the center of mass wouldn't change. Also last month in Scientific American there was an article about moving yourself through space by flailing your arms and legs. From what I remember it works because of the curvature of space (and so is very neglible unless you are standing next to a black hole). Suppose you are standing on a curved surface (like the Earth). You walk in a straight line, after some miles turn 60 degrees, and repeat till you have walked three straight lines forming what would be a triangle. If you calculate the center of mass as the point connecting all the meridians of the sides, and then do it again as as the point 2/3 of the way down from one of the vertex's (which should bring the same point) you get different points. This difference (the fact your center of mass isn't precisely defined) allows you to move yourself (instead of just moving forward and coming back) —Preceding unsigned comment added by (talk) 04:09, 17 August 2009 (UTC)
Listen guys, I have a big huge suspension spring in my basement, I stood on the bathroom scale and squeezed it. Nothing happened.</extreme intentional ignorance for the purpose of humor>ZS 11:49, 17 August 2009 (UTC)
Of course not. The energy that went into the spring, making it heavier, came from the chemical potential in your muscles. So the overall energy content of the system (you+spring) did not change. You need to weigh just the uncompressed spring, then compress it and re-weight. Alternatively, you can weigh yourself before and after the exercise, and subtract your body weight to cancel for the energy (and hence mass) you lost. --Stephan Schulz (talk) 12:10, 17 August 2009 (UTC)

Each spring is left to spring back to its normal state, not "stretched" during part of the cycle, but is compressed during the other part. But the power to weight of such a device (even if it worked ,which I don't know) would not have a practical application. But supposing you had two linked cyclotrons loaded with relativistic charged particles- protons for example swinging around each other, and switched one cyclotron off during part of the cycle? Would the centre of mass alter in a way sufficient for practical reactionless drive-or have I simply thought up a new version of "EM drive"-I don't know if this works either, though the Chinese are working on it now apparently. Also, if a spacecraft is ever constructed to achieve relativistic speeds, would the increase in mass cause the craft to collapse in on itself with gravitational effects?Trevor Loughlin (talk) 12:07, 17 August 2009 (UTC)

No. The rest mass doesn't change, and the spacecraft always perceives itself "at rest". — Lomn 13:04, 17 August 2009 (UTC)
If you turn off your cyclotron the protons travel in a straight line and crash into the sides of the tunnel. I'm not understanding your design... (either the springs one or the cyclotron one). Could you describe how one of them works in detail? What is causing this periodic compression and relaxation of the springs, for example? --Tango (talk) 13:14, 17 August 2009 (UTC)
On releasing trevor's spring all I can foresee is that simple harmonic motion ensues, with the energy that was potential, now oscillating to and fro from kinetic. Energy cannot be destroyed trevor, and so unless some sort of object leaves the system the mass of the system will remain the same. Elocute (talk) 21:47, 17 August 2009 (UTC)

Toothpastes with two anti-bacterial ingredients

Which toothpastes, particularly those available in the UK, have two or more anti-bacterial ingredients please? Mentadent P is one, but few places stock it. (talk) 13:01, 16 August 2009 (UTC)

Excuse my ignorance, but why does the number of such ingredients matter? Surely its their efficacy?--Leon (talk) 14:31, 16 August 2009 (UTC)
See here Note: I am not looking for a debate on the merits or otherwise of various toothpaste ingredients. Thanks. (talk) 16:51, 16 August 2009 (UTC)
Is it possible for mouth bacteria to develop resistance against antibacterial ingredients? John Riemann Soong (talk) 14:47, 16 August 2009 (UTC)
Certainly, and the flora in the human mouth are legion both in number of species and number of organisms (even after brushing, flossing, and using mouthwash). Sterilization of the mouth is not feasible (perhaps not even desirable), so what's the point of using antibacterial toothpaste unless it has been demonstrated, in carefully-controlled studies, to reduce a major problem (e.g. caries and/or gingivitis) without causing short- or long-term problems? Without such evidence, this practice could cause much more harm than good. This is all general comment and is not meant to substitute for or diminish any advice you might be given by a health professional. --Scray (talk) 15:36, 16 August 2009 (UTC)

Is anyone going to answer the question asked please? (talk) 16:41, 16 August 2009 (UTC)

Up till today I wasn't aware of a toothpaste with more than one antibacterial agent - unless you include fluoride, the only antibacterial agent I'm aware of in toothpaste (UK) is Triclosan. Perhaps there aren't any? (talk) 21:32, 16 August 2009 (UTC)
According to [38] (not the greatest of sources), it has triclosan and Zinc Citrate. I also came across this rather old study [39] which compares the activity levels. There also seem to be a lot of studies looking into the effects of the triclosan/zinc citrate combo [40] Nil Einne (talk) 22:50, 16 August 2009 (UTC)
This is a Science reference desk, so you're going to find it rather difficult to avoid discussion on which agents are truly "antibacterial" in anything other than the marketing literature. Many anitbacterials (antibiotics) have the perverse effect of actually promoting bacterial growth by eliminating beneficial (commensal) bacteria and promoting resistance in general when used in improper doses, so the focus here is rightly on whether the toothpastes in reality have a two-component action. Perhaps you would like to rephrase your question as "Which toothpastes claim to have two anti-bacterial ingredients?" - and then it becomes more of a RefMisc question than a RefScience question... Franamax (talk) 23:54, 16 August 2009 (UTC)
What sort of ridiculous people do you take us for? Do not use the science reference desk to ask questions that will be answered by those who answer by using Google to search for answers -- use Google yourself and spare us. DRosenbach (Talk | Contribs) 03:09, 17 August 2009 (UTC)
Please do not assume yourself to be ridiculous, or be emotive. It is impossible to predict beforehand if answers to questions asked will have answers from specialised knowledge, or just Google 'research' prompted by the question. Even with the latter, searchers may turn up information that the OP had not found despite spending some time previously searching, as happened in my case. (talk) 12:48, 17 August 2009 (UTC)
Impossible to predict...quite presumtuous. DRosenbach (Talk | Contribs) 22:33, 17 August 2009 (UTC)

From a lead given above, I have found this which indicates that Crest Complete, Mentadent, and Colgate Total are such toothpastes. Crest Complete is said to be the most effective, while Colgate Total is not effective. However the study is open to question by apparantly being funded by the manufacturer of Crest Complete. (talk) 12:48, 17 August 2009 (UTC)

De Havilland Dragon Rapide

What is the small propeller on the upper wing of this plane? —Preceding unsigned comment added by (talk) 14:47, 16 August 2009 (UTC)

(Guessing) It looks unnecessarily large to be (only) an airspeed sensor. I think it is an air-powered electric generator. Cuddlyable3 (talk) 15:22, 16 August 2009 (UTC)
It is a wind-powered electric generator MilborneOne (talk) 15:35, 16 August 2009 (UTC)

Fluorescent light comes on only after long, variable delay. Probable cause?

Here's a real-life puzzler: Fluorescent lights in a fixture would come on only after a long, variable delay (20 – 30 mins., sometimes longer). The fixture may have an electronic ballast (no starter is visible where it can be replaced easily). What might be the cause of the strange behavior? —Preceding unsigned comment added by (talk) 15:31, 16 August 2009 (UTC)

Do the filaments at each end of the fluorescent tube glow during the start delay? If yes then try a new tube. If no then something is wrong with the starter (which is sometimes hard to see behind the tube). Cuddlyable3 (talk) 15:50, 16 August 2009 (UTC)
There's no visible glow during the delay. If you flip the switch to off before the light comes on, you'll see a brief flicker of light. Occasionally flipping the switch back and forth a few times would cause the light to come on without the delay, but that's not always successful. -- (talk) 16:13, 16 August 2009 (UTC)
That is the symptom of a bad transformer in a "starterless" fixture. Replace the transformer. This is fairly cheap and easy to do (about like repairing a lamp or light fixture) but do not try it yourself unless you are comfortable with electricity. A dead transformer usually (but not always) has exuded some sticky melted tar: if you see tar, you know for sure it's bad. In my house, I gave up and refitted all of my tube flourescent fixtures to use compact flourescents. I removed the old transformers and wiring and added a bunch of screw-type scokets (four dual sockets) to each fixture. The compact flourescents are somewhat less efficient, but with tube flourescents I was always replacing either the bulbs or the transformers, and worrying that badd transformers were killing bulbs or vice versa. With the CFs, you just replace the bulb, the bulbs are each independent, and I can eventually shift to LEDs when they become economical. -Arch dude (talk) 20:14, 16 August 2009 (UTC)
Although LED fluorescent tube replacements seem more common (at least when I last looked) albeit perhaps can't be considered economical. E.g. [41] Nil Einne (talk) 23:01, 16 August 2009 (UTC)
I could understand a second, or a few seconds to reach full brightness, but 20 minutes is abnormal, and suggestive of some abnormality of the ballast, the starter, the bulb, or the wiring. Edison (talk) 03:30, 17 August 2009 (UTC)

BLAST search always fruitless?

I have reason to believe that GCTGAGAGAGAGAAAAAAAAAAATCAG is part of the human genome but when I go here, enter the sequence and click 'begin search', followed by 'view report', I get no matches. I also get the same result even with a simple string like CAT - what am I doing wrong? ----Seans Potato Business 16:39, 16 August 2009 (UTC)

I suspect that the presence of so-called low-complexity sequences (those highly-repetitive portions) are being automagically disregarded by the matching algorithm. Since the bulk of your sequence is low-complexity (highly-repetitive), all hits are getting filtered out. In the query screen that you've linked, look in the 'Optional parameters' box and change the 'Filter' setting from 'default' to 'none'. This will force BLAST to search using the entire sequence. Unfortunately, you're going to get a very large number of hits, as highly-repetitive regions tend to occur frequently by chance (due to gene slippage during copying). TenOfAllTrades(talk) 19:49, 16 August 2009 (UTC)
I'm not saying that slippage would generate the whole sequence spontaneously, only that it can extend the repetitive sections (the multiple GA and A repeats) in this sequence. TenOfAllTrades(talk) 21:35, 16 August 2009 (UTC)
The USCS genome browser places your sequence at chr14:51,714,964-51,714,983 using a BLAT algorithm. From what I understand, BLAT is better for looking for short, exact matches, than BLAST. It seems NCBI used to have an option to "search for short, nearly exact matches" but this is now part of the usual BLAST algorithm. FWIW I also got no hits using the NCBI version of BLAST, changing a couple of parameters. Weird... --- Medical geneticist (talk) 23:09, 16 August 2009 (UTC)

Artificial membrane

Hi, I would like to know if there are artificial membrane capable to separate CO2 and, at the same time, let the O2 and H2O molecules pass. If it is possible, I would like to know some commercial name. Thanks. —Preceding unsigned comment added by (talk) 16:48, 16 August 2009 (UTC)

It sounds like you're looking for a Carbon dioxide scrubber, like you'd find on a Rebreather or a space ship, but they're more complicated than a simple membrane. APL (talk) 18:21, 16 August 2009 (UTC)
Most CO2 scrubbers work by absorption rather than membrane filtration. In the most commonly used type, CO2 is absorbed by metal oxide or hydroxide (often KOH or CaO, sometimes LiOH too) to form the corresponding carbonate, which is then regenerated back to the oxide / hydroxide by heating with the release of CO2 (into a different gas stream, of course). Absorption by amine solution is pretty commonly used too (the amine acts as a Lewis base). And for really thorough CO2 removal (for example, in coal liquefaction plants), physical absorption with refrigerated methanol (at -30 C) is often used -- it's expensive, but it removes CO2 to less than 100 parts per billion. Which method is best for you will of course depend on what you'll be using it for (and especially on the volume-flow of your gas stream, the CO2 partial pressure, and the maximum remaining CO2 level desired). So if you could tell me what is it you're trying to do, I could maybe point you in the right direction. (talk) 01:13, 17 August 2009 (UTC)

Thanks to the both of you., I would like to grow algae, so I need CO2 trapped in the internal side of the membrane (but not as carbonate), and I would like to let O2 and H2O (made from the algae) spread to the external side. —Preceding unsigned comment added by (talk) 01:22, 17 August 2009 (UTC)

Oh -- I was assuming that you wanted to remove CO2 rather than concentrate it. (That's a natural assumption for me, cause most of my experience with CO2 scrubbing is in the context of a coal gasification plant.) Well, for your aquarium, I'd recommend passing the "product stream" (the mixture of O2/H2O/CO2 that comes out of the tank) through activated carbon, which will preferentially adsorb CO2 (but not O2), and then once the carbon is saturated with CO2, passing a stream of water (if the "product stream" is aqueous) or nitrogen (if the "product stream" is gaseous) through the CO2-saturated carbon and back into the tank. That will put the CO2 back into the tank while letting the O2 and H2O out -- essentially doing the same job as the membrane that you were asking about. (talk) 03:20, 17 August 2009 (UTC)

I understand; the matter is that it would be a very large colture volume, so I can't use adsorbtion. It's not easy at all, but you were very kind. —Preceding unsigned comment added by (talk) 12:25, 17 August 2009 (UTC)

Couldn't we use a principle similar to reverse osmosis? Just find membrane holes that will selectively allow oxygen and water, but not carbon dioxide. This seems possible, as CO2 contains 3 heteroatoms, oxygen only contains two, and water only contains one (and the hydrogen atoms should be small in comparison). On the other hand, it could be a problem if CO2 and O2 as linear molecules could slip in via the size of a single heteroatom. But CO2 is heavier than oxygen, so maybe that element could be combined too. How efficient would the CO2 filtration have to be? I mean if this only removes 50% of the CO2 with each pass, that might be good enough for some purposes. John Riemann Soong (talk) 13:23, 17 August 2009 (UTC)


  • CO2 selective polymer membranes often contain amino groups -eg search "CO2 membrane selective amine"
  • O2 selective membranes incorporate an oxygen carrier eg something like haemoglobin - see
  • water is a liquid.. I don't know any trade names. According to thermodyamics you'll have to supply energy to do the separation - probably as a pressure drop accross the membrane. (talk) 15:03, 17 August 2009 (UTC)
Zeolites are another possibility - CO2 and O2 are the same width, but CO2 is longer, it also has different chemical properties. Search "zeolite O2 CO2" (talk) 15:26, 17 August 2009 (UTC)
Don't you have to supply energy in reverse osmosis too? John Riemann Soong (talk) 20:57, 17 August 2009 (UTC)

"Good" or "Bad" Firewood

We recently had a storm come through and damage two trees to the point we had to take them down and cut them into firewood. What level of MMBTU/Chord makes a type of wood a good firewood? Based on that, are the Mulberry and Ash trees we cut good firewood? Ks0stm (TC) 17:46, 16 August 2009 (UTC)

This site [42] has a table listing the MBTU values of various trees. --Cookatoo.ergo.ZooM (talk) 18:46, 16 August 2009 (UTC)
But the critical thing for firewood is not MBTU but water content and how inclined to spit they are. Ash is generally rated as the best possible firewood. The very old rhyme we are all taught is fairly reliable except for Elm which burns fine (but superstition says don't do it)
Beechwood fires are bright and clear
If the logs are kept a year
Chestnut only good they say
If for long it's laid away
Make a fire of elder tree
Death within your house will be
But ash new or ash old
Is fit for a Queen with a crown of gold

Birch and Fir logs burn too fast
Blaze up bright and do not last
It is by the Irish said
Hawthorn bakes the sweetest bread
Elmwood burns like churchyard mould
Even the very flames are cold
But ash green or ash brown
Is fit for a Queen with a golden crown

Poplar gives a bitter smoke
Fills your eyes and makes you choke
Apple wood will scent your room
With an incense-like perfume
Oaken logs, if dry and old
Keep away the winters cold
But ash wet or ash dry
A king shall warm his slippers by.
or another version of the same poem:
Beechwood fires burn  bright and clear
If the logs are kept a year
Store your beech for Christmastide
With new holly laid beside
Chestnuts only good they say
If for years tis stayed away
Birch and firwood burn too fast
Blaze too bright and do not last
Flames from larch will shoot up high
Dangerously the sparks will fly
But Ashwood green and Ashwood brown
Are fit for a Queen with a golden crown

Oaken logs, if dry and old
Keep away the winters cold
Poplar gives a bitter smoke
Fills your eyes and makes you choke
Elmwood burns like churchyard mould
Even the very flames burn cold
Hawthorn bakes the sweetest bread
So it is in Ireland said
Applewood will scent the room
Pears wood smells like a flower in bloom
But Ashwood wet and Ashwood dry
A King may warm his slippers by.

--BozMo talk 19:05, 16 August 2009 (UTC)

DVD lasers

I've seen lots of speculation on the internet about taking the lasers out of DVD-R drives and putting them into flashlights, etc.e.g. These lasers are apparently powerful enough to pop balloons, burn retinas, and other not-very-safe things.

My question: how far can these project? How far are they dangerous? How much exposure would be necessary to, say, damage a human eye in a permanent way? What kind of eye-wear would be protective? The example above has a visibly red laser—what if one used the infrared laser from a CD-R drive? Or the violet laser of a bluray drive? How much of a threat is this, in the end?

I ask only because I am curious about the blinding-potential that exists out there in the world, were someone to be malicious about it, which is a disturbing thought. I thought one of you mad scientists could fill me in. -- (talk) 18:16, 16 August 2009 (UTC)

This reference says that DVDs have Class 3B or Class 3R lasers. See Laser safety for precautions. -Arch dude (talk) 19:59, 16 August 2009 (UTC)
A class 3 laser is a fairly dangerous thing. Even a class 2 laser can damage your eye with just a quarter second of exposure. A class 3 laser can wreck your vision in less time than you can blink - so the scope for accidents while messing around with them is significant - it's easy to think you're pointing the laser across the room - then hit a mirror or a window or something and bounce the light back into your eyes. IR and UV lasers are doubly dangerous because you can't tell you're looking into one until you can't see clearly anymore. Even the little class 1 or class 1M lasers in laser pointers can damage your eyes with enough exposure. There really is no such thing as a "safe" laser - even the ones in green laser pointers rely on you looking away and blinking to save your sight.
As to how far they can project...that's the thing about lasers - they don't get dimmer with range (well, at least not very quickly). In theory a laser beam is a parallel beam - so all of the energy stays together instead of safely spreading out like 'ordinary' light. In practice, most lasers are not perfectly parallel - but still, it's kinda meaningless to talk about a "range".
SteveBaker (talk) 23:11, 16 August 2009 (UTC)
What I'm really trying to get at is: let's say there's a huge crowd of people at some kind of major event (let's say, the Superbowl). Could one guy with a CD writing drive laser (which is in the infrared, if I understand the optical drive page correctly, but is still in a wavelength that can do damage) plugged into a big mag-lite be able to secretly do major eye damage to lots of people there? -- (talk) 00:45, 17 August 2009 (UTC)
OOH! Class 3a lasers can blind you in 1/4 second! Then why are they sold as pointers/cat toys? Could it be because the output is less than 5 milliwatts? How does that compare to the energy (per square mm) falling on the retina when I look at snow or a anything painted white under full sunlight? The BS alert just sounded full volume. Edison (talk) 03:27, 17 August 2009 (UTC)
Luckily for us Edison, we aren't talking about class III A lasers. True their output is less then 5 milliwats, which is why no one considers them dangerous. However a class III A laser isn't a class 3 B laser. Btw I can't remeber the name for the unit that measures the amount of energy from sunlight that falls on the ground. It has some really strange units (not Joules/square meter). Anyone remember? EDIT: I remember now: the unit I was thinking off was the langley (and it was in J/sq. m. (talk) 04:52, 17 August 2009 (UTC)

Yeah - you have to be very careful. The OLD classification scheme used roman numerals and was based on some highly unsound science. The NEW classification uses arabic numerals and is a much more accurate description of the safety of lasers. So a class III laser is like a laser pointer or something - but a class 3 laser is able to blind you before you can blink. SteveBaker (talk) 21:36, 17 August 2009 (UTC)
A quarter of a second is a huge span of time if you're trying to blind someone from across a football stadium. Most people couldn't hit someone's pupil at that range with a rifle, let alone a laser pointer.
To do this you would have do construct a laser pointer with a tripod and a scope. Even then you'd still need tremendous skill and a lot of luck. It'd be a lot easier to just walk up to people and throw bleach in their face. APL (talk) 16:52, 17 August 2009 (UTC)
Right, except you'd get caught if you did that. If you had an infrared laser at some distance in a concealable case, nobody is going to know who did it. That's the issue I'm asking about, in the end. -- (talk) 19:19, 17 August 2009 (UTC)
You'd either need to be so close to someone that it would be obvious that you were the one with the laser, or you'd need a super elaborate aiming contraption.
You'd never blend into the crowd with a laser-pointer that looks like a sniper-rifle on a tripod. The target you're trying to hit (and maintain contact with) is minuscule even at close range.
(If the laser is IR it's even MORE difficult to aim, because you don't have the red dot to use as reference.) APL (talk) 19:58, 17 August 2009 (UTC)

What is the risk of brief laser exposure compared to briefly staring into the sun? Which (comparing the class of laser to a cloudless summer in England for example) would cause permanent damage the quickest? (I have NO plans to try this out!) Also, is staring into a shop laser scanner (out of curiosity at the scintillation effects) dangerous? My retinal scan shows no damage, though perhaps being short-sighted lessens the focus/damage? Trevor Loughlin (talk) 13:07, 17 August 2009 (UTC)

Shop scanners don't point at a single location, they flick rapidly back and forth across a path. So the damage would be less than their power output would imply. Vimescarrot (talk) 14:23, 17 August 2009 (UTC)
There seems to be some doubts up there whether the lasers can damage ones' eyes. I don't think there's ANY doubt that a strong laser can do that, and I imagine that a laser that can pop a balloon is strong enough to damage one's photoreceptors. If a stadium is rather too large to hit a small eye target (which I think is probably true), what about smaller distances? Or put another way—what's the minimum distance (estimated) that this would be a serious problem? (esp. if the one with a laser has both a scope of some sort, and some basic way to stabilize the laser). -- (talk) 19:19, 17 August 2009 (UTC)
I don't think the lasers used in barcode scanners are class 3 - there is no reason for them to need to be that bright. They're probably class 1 - which are relatively safe. But as Vimescarrot points out - they are scanning so rapidly that the average brightness wouldn't be low enough to hurt you even if they were more powerful than that. The concern with such contraptions is what happens when the mechanism that oscillates the laser breaks...typically, everyone peers into the machine to see what broke! I bought a piece of a supermarket scanner mechanism on eBay for my 3D scanner project - and it doesn't move the laser at all. It has a holographic lens that stretches the laser spot out into a line - which it bounces off mirrors to make the criss-cross pattern. No moving parts...nothing to go wrong. SteveBaker (talk) 21:36, 17 August 2009 (UTC)

August 17

Bell peppers

Are bell peppers true berries under the botanical definition? --‭ݣ 01:52, 17 August 2009 (UTC)

Yes, they are.CalamusFortis 01:58, 17 August 2009 (UTC)

Phases of matter -- all relative

Are all elements in gaseous form on the surface of the Sun? DRosenbach (Talk | Contribs) 03:38, 17 August 2009 (UTC)

I'm struggling to understand exactly what you mean by your question. Something that I think is relevant is that the Sun does not really have a "surface". There is giant ball of gas and it gets denser and hotter until it is opaque to electromagnetic radiation. That's what we see when we look at the sun. It's a gradient, not a absolute line. If you were to move towards the centre of the sun, there would be no specific point where you would say I was just above the surface and now I'm just below. Vespine (talk) 04:25, 17 August 2009 (UTC)
I think the answer to your question is yes. On what looks to be the surface of the sun, every substance we know of on the earth is a gas, it is too high for solids or liquids to exist. Graeme Bartlett (talk) 08:39, 17 August 2009 (UTC)
..or no, depending on how one reads the question. First, I'd suspects most elements are actually a plasma anywhere near the "surface" of the sun. A plasma is or is not a gas, depending on the ontology (if the 4 states of matter are disjoint, its not, from a thermodynamic POV it is). But secondly, are all elements on the surface of the sun? Probably not. I'd suspect that all naturally occurring ones are, though. --Stephan Schulz (talk) 09:10, 17 August 2009 (UTC)
I would suspect that the dense elements (Uranium, lead etc) would not be at the surface but in the center of the sun, but perhaps there are trace amounts at the surface. Googlemeister (talk) 14:16, 17 August 2009 (UTC)
My question may not have been my stated in the proverbial, but intention was to ask it in that way -- would all elements be in gaseous form at or near what appears to be the surface of the sun? DRosenbach (Talk | Contribs) 23:16, 17 August 2009 (UTC)
It is a little difficult to work out because boiling points depend on pressure. If we assume that at the surface the pressure is near to zero (which makes sense for the edge of the sun - there isn't much outside it) then you basically can't have liquids, they would boil instantly, so we're actually looking at the temperatures at which elements under low pressure sublime. Unfortunately we don't seem to have a List of elements by low pressure sublimation point (we have lots of other lists of elements, but not that one) article, so I'm drawing a blank! I'm also not sure about the pressure at the surface of the sun being near zero, the corona is usually considered to be outside the surface and it will cause some pressure, I'm just not sure if it is negligible or not. --Tango (talk) 00:28, 18 August 2009 (UTC)
Also our Sun does not contain "all" the naturally occuring elements, including lead and uranium. Those do not exist on the Sun as far as we know even in trace amounts. Only more massive stars have enough oomph to spit out heavier elements. Our sun is made up Hydrogen and Helium and of only about 10 other elements, none of which are heavier then iron or nickel.Vespine (talk) 00:50, 18 August 2009 (UTC)
If they are on Earth, then they will be in the Sun. The Earth formed out of the same nebula as the Sun. They are greater abundance on the Earth (proportionally speaking) because the Earth has lost most of its hydrogen and helium, but that doesn't change the absolute amounts. --Tango (talk) 00:54, 18 August 2009 (UTC)
According to Sun, the "effective surface temperature" of the sun is at 5778 degK. List of elements by boiling point says that Rhenium has the highest boiling point of all elements - and both it and Tungsten would just barely be liquid at 5778K (Tungsten boils at 5828K and Rhenium at 5869K). However, the sun's corona is at 5 million degrees and the core is at 16 million this is a fairly 'careful' answering of our OP's question. SteveBaker (talk) 01:13, 18 August 2009 (UTC)


Is it just me, or does looking at this make you want to squint, even though it's no brighter than a pure white screen? Is it like an optical illusion, because your brain thinks it's looking at the sun, so you squint by reflex? DRosenbach (Talk | Contribs) 04:14, 17 August 2009 (UTC)

I looked at it and the corners of my eyes tightened, and then I forced them back by telling myself that it was just a picture. But while looking at it, I felt nervous about something. So yes, I'm programmed to not look directly at the sun. Whew. Awickert (talk) 04:18, 17 August 2009 (UTC)
Me too. Very cool effect - I would not have expected this at all. --Stephan Schulz (talk) 13:13, 17 August 2009 (UTC)
Yes, same response here, I guess the eye tightening is a sort of acquired reflex. (talk) 13:23, 17 August 2009 (UTC)
Could it be that it is simply a higher contrast image than a blank white screen? —Akrabbimtalk 13:56, 17 August 2009 (UTC)
I'm inclined to agree with Akkrabbim here, though I can't cite any studies to back it up. You're looking at this picture, and it appears that the figure in the middle is blown out by the 'bright' subject — so you squint to try to see missing detail that's been washed out. TenOfAllTrades(talk) 14:09, 17 August 2009 (UTC)
This (and many other) tricks are well-known to us evil computer game graphics geeks who seek to elicit real-world emotions from people staring at tiny, dim, flat screens! If you animate it to simulate the rate of change of light perception due to your irises rapidly shrinking to tiny little dots, it's even more effective. SteveBaker (talk) 20:21, 17 August 2009 (UTC)
Ah, so making the image darker, makes the viewer think they are looking at a very bright object. You are truly an evil genius :) (talk) 20:28, 17 August 2009 (UTC)
A plain white filled circle would not cause the squinting reflex. The streaks and secondary images are characteristic of an "overloaded" eye lens + retina, to which sight the iris muscle is programmed to contract. Cuddlyable3 (talk) 21:27, 17 August 2009 (UTC)

Sleep deprivation and hallucinations

How long must sleep deprivation generally be maintained to achieve hallucinations? Is it always the safest method of doing so? NeonMerlin 04:35, 17 August 2009 (UTC)

Hallucinations are not a guaranteed side effect of sleep dep, they are a possible side effect. My record is staying awake for 4 days (over 80 hours) and I don't think I experienced any hallucinations, well nothing vivid or memorable anyway. I also do not believe intentional sleep deprivation is considered "safe". I am not aware of any safer and legal ways to more reliably achieve hallucinations, though there are several safer but illegal ways to do it, which I could not recommend in a public forum but for purely informative purposes you can start with the article on hallucinogen. Vespine (talk) 04:56, 17 August 2009 (UTC)
The definition of hallucination should also be taken into account. I believe sleep deprivation produces deliriant-like hallucinations, which is where one is unable to determine what is real or not (it is often compared to dreaming whilst being awake). The hallucinations produced by psychedelics can usually be distinguished from reality by those intoxicated, and they are generally stereotyped as things such as: colourful lines, streaks, shimmers, halos, etc.
We can't give medical advice on what is the safest way of achieving hallucinations. I suggest you read the articles that are wikilinked in this discussion. I should also mention that being delirious can lead to behaviour putting one's life into danger. The man in this article took nowhere near the lethal dose of diphenhydramine, but it sounds as though the delirium led him to fatally wound himself with an electric fan. --Mark PEA (talk) 16:08, 17 August 2009 (UTC)
I think sleep deprivation is reasonably safe if you avoid any sort of risky situation, but the level necessary to get hallucinations is so unpleasant that I can't imagine anybody doing it for that reason, especially considering that the hallucinations themselves are likely to be unpleasant. Looie496 (talk) 17:25, 17 August 2009 (UTC)
This is fun reading. (Unrelated, but fun reading.) Bus stop (talk) 20:41, 17 August 2009 (UTC)
I think it will depend on how you stay awake. If you just do it by willpower alone then you'll probably be fine - your body will force you to sleep before it becomes harmful, the human body is generally very good at stopping us from doing stupid things. If something happens to wake you up every time you start to drift off then you could reach dangerous levels of sleep deprivation. --Tango (talk) 01:01, 18 August 2009 (UTC)

Press releases on research papers

Do any scientists regularly produce press releases on their own research papers to improve the accuracy of media coverage? NeonMerlin 07:06, 17 August 2009 (UTC)

See here for the scary truth. --Stephan Schulz (talk) 09:12, 17 August 2009 (UTC)
LOL! That is marvellous :) — QuantumEleven 15:11, 17 August 2009 (UTC)
We publish our results in as many places as we can. It's not the fault of the science community that the majority of the world prefers to consume media from secondary and tertiary sources - academic journals are widely available. Nimur (talk) 16:53, 17 August 2009 (UTC)
Indeed. In fact, most of the short pieces in science news magazines such as "New Scientist" are based on press releases. Sad to say, some scientists show much less discipline in writing press releases than in the journal articles they are based on, although the pressure for glitz from university press offices certainly comes into play. Looie496 (talk) 17:19, 17 August 2009 (UTC)
(ec) That comic is pretty accurate, and the next one too. Probably most of the science articles in a typical newspaper are adapted (or quoted verbatim) from a press release, but the press releases are not written to improve the accuracy of the reporting, they're written to make the sponsoring university look good so that they can attract more donors. Sometimes the researchers themselves write documents apparently intended to help reporters, like this one, but it's pretty uncommon. -- BenRG (talk) 17:21, 17 August 2009 (UTC)
At many universities there are people paid full time to figure out what researchers are up to and to try and publicize it. It's not a bad job, I hear, given the current state of journalism in general. -- (talk) 19:11, 17 August 2009 (UTC)

No fish native to a river is poisonous?

I saw it on TV. True or false? I know that certain fishes, like the Candiru or Piranhas can seriously harm or kill you, but couldn't find any poisonous river fish.--Quest09 (talk) 11:28, 17 August 2009 (UTC)

Not sure - some catfish have spines (not teeth) that include a poisonous secretion
Perhaps it meant a posionous bite? (talk) 11:59, 17 August 2009 (UTC)
Then they meant "venomous" not "poisonous" (common mistake). --Tango (talk) 13:28, 17 August 2009 (UTC)
Or not? Catfish have venom- but not in the bite. (talk) 14:44, 17 August 2009 (UTC)
The flesh of all animals is edible (so says a survival handbook I once read). It is only the internal organs that could be poisonous, if you are careful to avoid them you should be fine. --Tango (talk) 13:28, 17 August 2009 (UTC)
The closest thing I can think of is the platypus which has poisonous/venomous/ouchy spurs. Aaadddaaammm (talk) 13:37, 17 August 2009 (UTC)
That depends on how broadly one interprets 'native' (and 'river'). (I'm also assuming, per Tango, that you're going for 'venomous' here.) There are a number of families of marine fish which have developed species adapted to river life. The stonefish, for instance, primarily occupy coastal waters of the Pacific, but a few species (like Notesthes robusta) have adapted to life in streams and tidal estuaries. Trichinus draco, the Greater weever, is now found in the Thames. There are a number of other 'edge cases' which rather blur the general rule you heard. TenOfAllTrades(talk) 14:02, 17 August 2009 (UTC)
The Greater weever doesn't seem to match Tango's description of venomous, there are plenty of venomous purely freshwater species that use venom as a defence. (talk) 14:44, 17 August 2009 (UTC)
I never gave a description of venomous, I just said that delivering a toxin by biting is venomous. Venom can be delivered by bites or stings. Poison has to be ingested. --Tango (talk) 17:49, 17 August 2009 (UTC)
You are right. Isn't venomous a subset of poisonous though? (talk) 18:52, 17 August 2009 (UTC)
Venomous = poisons things by attacking without dying, like a venomous snake. Poisonous = poisons things when those things eat it, like a poisonous fruit. Dcoetzee 21:02, 17 August 2009 (UTC)
Is catfish defensive spine venomous or poisonous or both? (talk) 21:12, 17 August 2009 (UTC)
Venomous, you don't get harmed by eating the spine, you get harmed by being stabbed by it. Of course, the venom glands (or whatever) of a venomous animal will presumably be poisonous. --Tango (talk) 01:02, 18 August 2009 (UTC)


1) In a stirling cycle,the volume varies between 0.03 and 0.06m3,the maximum pressure is 0.2MPa and the temperature varies between 540oC and 270oC.The working fluid is air. a)Find the efficiency and the workdone per cycle for the simple cycle. b)Find the efficiency and the workdone per cycle for the cycle with an ideal regenerator,and compare with the carnot cycle having the same isothermal heat supply process and the same temperature range.

referance:stirling  cycle.

2)A boat moved by a jet propulsion,discharge water through a jet of area 0.02m2,the water being drawn from inlet opening facing the direction of motion.The total drag is estimated to be 17.66u2Nm,where u is the speed of the boat in m/s.If the boat moves at 54km/h,determine:

          a)relative  velocity of jet;
          b)energy supplied by the jet and power of the motor required to work the  pumps;
          c)efficiency  of  propulsion.
Take the density of water 1020kg/m3 and efficiency of the  pump set 75%.
 referance :FLUID MACHINERY.  —Preceding unsigned comment added by (talk) 11:41, 17 August 2009 (UTC) 
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Thank you.

What lizard is this?

I was in Istanbul and saw this lizard. I was wondering if it could be used if there isn't a decent picture of this particular species of lizard. It was waiting for me to take its picture.

Personally, I'd place my bet on it being in the Lacertidae family, but I could never identify the genus, let alone the species. Perhaps someone at WP:WikiProject Amphibians and Reptiles would be more useful here.-- (talk) 14:35, 17 August 2009 (UTC)
I was thinking of a variety of anole, Polychrotidae family. But I am not too confident on that one. --Jayron32 15:41, 17 August 2009 (UTC)

Prion Terrorism

Could concentrated and extracted "Mad Cow" prions be a potential terrorist or state bio-weapon? Could they be distributed as a fine mist? —Preceding unsigned comment added by Trevor Loughlin (talkcontribs) 12:19, 17 August 2009 (UTC)

It wouldn't be very effective for terrorism. Even if it could be manufactured in sufficient quantities and distributed like you describe, most people wouldn't even be aware that they were 'infected' for many decades, or perhaps not until they were autopsied fifty years from now. Wouldn't give much terror bang for the buck. Much easier and more effective to blow something up. APL (talk) 12:58, 17 August 2009 (UTC)
With that being said, odds are if someone created a scare of prions, that cuuld cause high levels of panic and life alteration in a society. ~ Amory (usertalkcontribs) 15:07, 17 August 2009 (UTC)
It's not particularly useful as a state or military weapon; as APL notes the development of symptoms would take years, and infected individuals would be unlikely to transmit infection. (There's no point to using a weapon that doesn't have any effect until years after the war is over, unless you want to invite retribution by similar means.) As a terrorist weapon, it wouldn't have any immediate visible effect, so it's not going to kill people. It could be very effective as a scare tactic, however. A 'fine mist' would be difficult to use, and probably not an effective route of administration. Far more effective to spike food or beverages. Transmission in animals requires several milligrams of brain homogenate from an infected animal: [43]. The effective dose in humans is very uncertain. TenOfAllTrades(talk) 14:24, 17 August 2009 (UTC)
Quibble: Sure there could be a point to using a weapon with a really long "fuze". Suppose Country #1 wanted to wipe out the population of Small Country #2, and Country #1 had access to an effective, nonreversible sterility agent with a secret formula. Country #1 disperses it all throughout Small Country #2. Ten years later, nobody in Small Country #2 is having any kids, and in 50 years the population has crashed, or Small Country #2 is 90% immigrants and is pliable to new political suggestion from Country #1. Mission accomplished! That said, this speculation has nothing to do with prions. Tempshill (talk) 17:06, 17 August 2009 (UTC)
You've been watching Stargate. Vimescarrot (talk) 20:52, 17 August 2009 (UTC)
In general, bioterrorism in reality is a lot more difficult and a lot less effective than "security experts" would have you believe. Aum Shinrikyo learned this the hard way: they're one of the richest and most well-connected terrorist organizations in the world, and after several expensive, botched attempts at bioterrorism, they finally managed to kill a total of 12 people with sarin, which (unlike prions) is a highly lethal nerve agent. As APL succinctly put it, it's much easier and more effective to blow something up. --Ashenai (talk) 15:14, 17 August 2009 (UTC)
For a wonderful, short little history of how easy it is to blow something up, see Mike Davis, Buda's Wagon: A Brief History of the Car Bomb. -- (talk) 21:40, 17 August 2009 (UTC)

Turbopumps on rockets

Turbopumps are used on liquid-fuelled rockets to pressurise the fuel and oxidiser before they reach the combustion chamber. What powers the turbopumps (turbochargers on cars use the car exhaust for power, what does a rocket turbopump use)? — QuantumEleven 14:56, 17 August 2009 (UTC)

The turbopumps are powered by a preburner, which burns a small amount of fuel and oxidizer to run the turbopumps. In the picutre, the preburner is number 6. The preburner provides hot gas to run the turbine (number 5), which drives the turbopumps (numbers 3 and 4). anonymous6494 15:25, 17 August 2009 (UTC)
Rocket liquid fuel engine.svg
(ec) There's a fairly extensive discussion in this page linked from our article. For cryogenic fuels and oxidizers (liquid oxygen, liquid hydrogen), some pumps can be driven simply by heating the liquid to ambient temperature or above and allowing the expanding gas produced to drive the turbine. With other fuels, a preburner can be used which combines fuel and oxidizer to generate a small amount of hot, pressurized gas. There are several variations on these themes, which offer different methods of preheating the fuels, and which vent the turbine exhaust in different ways. TenOfAllTrades(talk) 15:27, 17 August 2009 (UTC)
It depends on the design. Sometimes, the turbos are powered by a totally separate source (e.g. a battery or a small separate combustion engine). Other times, they tap off the main propulsion energy source, or use the decompression of a refrigerated fluid to power the pump. All of these scenarios have various advantages and disadvantages to the stability, robustness, and mass budget of the rocket. If mass and flight-time is not an issue, the probable best solution is an electric motor; but this requires a large battery (and suffers from scalability - large mass-flux rockets can't really work off an electric turbo pump) - so more often, the turbo either kicks in later or gets an electric start and eventually draws energy from the primary propulsion source. Nimur (talk) 16:56, 17 August 2009 (UTC)


What color is pure gold if there is no light shining on it? Is it possible to have color without having reflected light? Googlemeister (talk) 16:36, 17 August 2009 (UTC)

The same. What colour is blue paint in the dark? <rhetorical> (talk) 16:39, 17 August 2009 (UTC)
(EC with above)This sounds like "If a tree falls in the forest, and no one hears it, did it make a sound" sort of metaphysical discussion. How do you define color:
  • As wavelength(s) of electromagnetic radiation
  • As human perception of those wavelengths
  • Is the potential to do something the same as actively doing it?
There's just way too many ways to interpret the question to answer it with a definative answer. --Jayron32 16:42, 17 August 2009 (UTC)
It is possible to have color without reflected light. I have a keychain that has a combination of tritium and phosphorus it appears pale green even in pitch blackness. This is because it emits a pale green light. Light has to be involved one way or the other. APL (talk) 16:45, 17 August 2009 (UTC)
Maybe the atomic absorption/emission spectrum of gold is relevant here. That's about as close to the "natural" inherent color of atomic gold as any definition can come. But because gold is a noble metal, and a transition metal, its valence electron behavior is a bit pathological - I'm not sure there's a very well-defined emission spectrum (at least, not as simple as, say the Hydrogen spectrum). Nimur (talk) 17:00, 17 August 2009 (UTC)
True, but then we get involved in the metaphysical discussion of whether or not something which normally has a color can be said to have a color even if it is not currently emitting/reflecting light. Is it enough to say that something has a color if we define a set of conditions where light could not possibly be involved? Its the "tree falling" discussion all over again... --Jayron32 16:59, 17 August 2009 (UTC)
Color, as most philosophers currently see it, is fundamentally a property of a material -- the color of an object defines the relationship between the light that strikes it and the light it emits. So it is completely proper to say that the color of gold is orange. What complicates things is that we perceive light itself as having a color, but these perceptions are tricky and paradoxical in some respects.
If the gold is hot enough, it will emit light, but the spectral distribution will vary with temperature. Edison (talk) 18:52, 17 August 2009 (UTC)
This is purely a linguistic thing. We use the word "color" for at least two phenomena: Firstly, the spectral characteristics of light coming from an object towards our eyes. Secondly, the inherent reflectivity-as-a-function-of-frequency (or transmissivity-as-a-function-of-frequency) of a material. So if you are talking about the color of gold in the first sense - then the answer depends on what color of light you're shining on it...or indeed if you are shining light on it at all. In this first sense of the word, the gold is black when there is no light shining on it. The second sense implies a property of gold (that it is golden) that is the same irrespective of whether there is light shining onto it or what color that light is. For some senses of the term, we actually use different descriptive words. We say that gold is "golden" - and not "orange" because we know that gold is highly reflective and "orange" somehow doesn't seem right. This problem is most clearly demonstrated when you ask what color a mirror is. Most people (if forced into giving an answer) would say "silvery" - implying something that reflects all frequencies equally - but "white" would be an acceptable answer. What gets difficult is when you have highly reflective surfaces that don't have these "special" names...a "green" car doesn't look at all green under an old-fashioned orange street-lamp. When this happens, we have to resort to circumloqutions like "That green car looks yellow!" is so often the case, language is a mess - but the science is quite clear. SteveBaker (talk) 20:13, 17 August 2009 (UTC)
Gold leaf can be beaten thin enough to become translucent. The transmitted light appears greenish blue, because gold strongly reflects yellow and red.<> Cuddlyable3 (talk) 21:04, 17 August 2009 (UTC)
(replying to Steve) It's even trickier than that, because our color perceptions are to a substantial degree illumination-invariant. This can lead to some weird effects. For example, suppose you are in a room with fluorescent lights, and looking at a piece of white paper next to an active computer monitor. Suppose you change from fluorescent to incandescent lighting (which is bluer) -- what you will perceive is that the image on the computer monitor shifts color while the piece of paper keeps the same color, exactly the opposite of what happens to the light they emit. Looie496 (talk) 21:19, 17 August 2009 (UTC)

Ants sting instead of bite?

Am I the only person who assumed that ants bite with their mandibles instead of stinging with . . . something else? The ant in this photograph has scary-looking jaws, but apparently they are not responsible for the ant's painful "sting". Where exactly do they keep the sting? Do they spray or inject (the ant article mentions both as a possibility)? I've pulled up all of the information I can find on this species on the 'net, and they are consistently referred to as having a sting and not a bite, but no further details are given. Maedin\talk 16:50, 17 August 2009 (UTC)

Our article on fire ants is informative. It states that most ants use a "bite and spit" combination to "sting"; while a fire ant uses an abdomen-mounted stinger, much like a bee, to do so. So the answer to your question is "it depends on the species of ant". --Jayron32 16:56, 17 August 2009 (UTC)
To elaborate, an ant clamps down with its mandibles, but the actual injury is sustained when it stings the target. Ants are related to bees and wasps.CalamusFortis 17:12, 17 August 2009 (UTC)
Didn't you see Them!? B00P (talk) 18:59, 17 August 2009 (UTC)
Obviously I didn't, ;-) Thanks a lot for your responses; it would still be nice to know whether Myrmecia esuriens stings with a stinger in its abdomen, or bites (or clamps) and spits. I don't see any specific mention of a physical stinger in any of the sources I could find, so I will have to assume that it's the latter method. Maedin\talk 19:41, 17 August 2009 (UTC)

Recycled ants?

I crushed an ant on a window sill and left it there. A few minutes later I returned and found what appeared to be another ant carrying my first victim away. What is the purpose of this behavior? Do ants bury their dead? —Preceding unsigned comment added by (talk) 17:18, 17 August 2009 (UTC)

More likely the first ant will be lunch. Googlemeister (talk) 17:46, 17 August 2009 (UTC)
Perhaps a ceremonial lunch in which the recently deceased will be remembered fondly for its contributions to ant culture. Bus stop (talk) 17:49, 17 August 2009 (UTC)
The decedant? DMacks (talk) 17:59, 17 August 2009 (UTC)
The ant's religious affinities are not known at this time. Bus stop (talk) 18:07, 17 August 2009 (UTC)
Protestant. DMacks (talk) 18:16, 17 August 2009 (UTC)
You've heard of "the Elephants' Graveyard," but, it seems, not "the Ants' Cemetary," Also the corpse is being studied by the ant equivalent of Gil Grissom to determine who the killer is. I'd leave town if I were you. B00P (talk) 19:15, 17 August 2009 (UTC)
I suppose the ant version of Grissom understands and is obsessed with humans? ~ Amory (usertalkcontribs) 19:18, 17 August 2009 (UTC)
I would think that, prior to deciding if the body should be carried off, they would determine the antecedant cause of death. StuRat (talk) 00:17, 18 August 2009 (UTC)
There was an interesting thing about this behavior on TV sometime ago. Evidently the dead ant gives off some kind of smell/pheremone that the other ants detect which kicks them into "Remove the body from the nest" behavior. The researcher (sorry - I forget his name) figured out what the chemical was and had a lot of fun smearing microscopic drops of it onto live ants - who would be grabbed and carried screaming and kicking from the nest by their former colleagues. As soon as they dumped the "corpse" outside the nest, it would immediately come scurrying back in - only to be grabbed and ejected again. Pretty funny actually. So evidently, the nest-mates don't eat the corpse (that would probably be a bad idea anyway because this could cause the spread of diseases through the nest). I have no idea what the smell causes them to do when they're outside the nest...but evidently there is still some behavior involved. SteveBaker (talk) 20:00, 17 August 2009 (UTC)
Maybe it was [[]], who studies myrmecology. Bus stop (talk) 20:14, 17 August 2009 (UTC)
Wilson doesn't do stuff with chemicals... And I'm sure Steve would remember if it was E.O. Wilson! -- (talk) 20:36, 17 August 2009 (UTC)
OK. I couldn't even think of E. O. Wilson's name. I had to search for ant man or some such search terms. Bus stop (talk) 20:44, 17 August 2009 (UTC)
Chemically-induced bullying... very funny, I'm sure, Steve. --Tango (talk) 20:04, 17 August 2009 (UTC)
Actually, this only applies to ants who are infected by a particular killer spore. Ants can tell normal dead ones from ones killed by a dangerous contagious disease. Dcoetzee 20:59, 17 August 2009 (UTC)
As to what Steve said there was some furthur thing with the ant pheromone and it didn't work precisly that way. I just can't remember how it was different. I'll post link if I can remember. EDIT: Here's the link from where I first heard the story Steve heard. Now if only I can find the later story that added some stuff to this one... (talk) 23:29, 17 August 2009 (UTC)

Digital Electronics

What exactly is the differece between priority encoder and a priority decoder??

This FAQ may contain your answer. As I assume you know, a priority encoder gives a binary code telling you which is the highest-priority input (e.g. an interrupt) that is active. It seems that a priority decoder is just an ordinary decoder that converts the binary code from the priority encoder back to one of many outputs (e.g. interrupts again). In other words, a priority decoder is logically the same as an ordinary encoder, but it just has the word 'priority' added to indicate that it is being used in conjunction with a priority encoder. --Heron (talk) 20:10, 17 August 2009 (UTC)
This question was cross-posted on the Computing desk. I'm merging it to here. Nimur (talk) 20:47, 17 August 2009 (UTC)

What exactly is the differece between priority encoder and a priority decoder?? —Preceding unsigned comment added by Piyushbehera25 (talkcontribs) 18:41, 17 August 2009 (UTC)

Have you read Encoder and Decoder? An encoder reduces the number of bits, while a decoder increases the number of bits. Cascading the two devices, you can reconstruct the original signal (one device performs the adjoint operation to the other). Nimur (talk) 20:16, 17 August 2009 (UTC)

DNA ligation in vitro

I have a mix of standard d(N)6 random DNA hexamers, and I want to ligate them to the 3' end of an arbitrary single-stranded DNA oligomer. Neither is currently modified in any way. Does anybody have any suggestions for a relatively cheap and easy way of going about this? – ClockworkSoul 18:42, 17 August 2009 (UTC)

Aha! This should do nicely. – ClockworkSoul 19:09, 17 August 2009 (UTC)

I misread the title as "DNA litigation in vitro". Gave rise to some interesting mental images! --Anonymous, 20:26 UTC, August 17, 2009.


what is the lube covering suppository for constipation. it looks like vasaline but i dont think its that —Preceding unsigned comment added by (talk) 21:05, 17 August 2009 (UTC)

You'd have to tell us which brand of suppository you have to know for sure. Suppositories are often encased in a capsule of glycerin, which is itself a lubricant. Just the warmth of your finger (or other parts) can cause some melting so that the suppository is self-lubricating. It is very unlikely to be Vaseline or any other non-water-soluble lubricant, for a variety of reasons. --Sean 21:26, 17 August 2009 (UTC)

i dont know the brand it was it was in the 90s. there was lube all over it it was goopy like vasaline. they were not induvidulaly packaged. i think they were in a round tin. —Preceding unsigned comment added by (talk) 22:39, 17 August 2009 (UTC)

Cant (road/rail)

I have taken issue with this article as it appears to be about two separate things. Camber and bank, the former being the raise in the middle of a road in both straight and curved sections that is there for drainage reasons, and secondly bank, the slope of a road on a curved sections to allow vehicles to pass at higher speed.

But before taking action I thought it best to agree with some people to which of these both cant and camber actually refer. Particularly as I have not heard of the term "cant" before. Thank you. Elocute (talk) 21:34, 17 August 2009 (UTC)

Suppositories - q for the medical people here

How common is it for patients to swallow prescribed suppositories by mistake? You hear stories about it but is it a particularly widespread error? -- (talk) 21:55, 17 August 2009 (UTC)

Looking for a nutrition web site

No big deal, you say ? Well, I'm looking for a site which will list foods which are good for diabetics, those with high blood pressure, those with kidney failure, etc. Still no big deal ? Well, I want it to recommend foods for those with multiple medical conditions. (Note that I'm not asking anyone here to recommend any foods, just a site where I can look it up myself.) Ideally you should be able to weight the medical conditions, say if you only have slightly high blood pressure but have severe diabetes. In that case avoiding foods with a high glycemic index would be more important than avoiding salt. It should also list foods from best to worst, for the given medical conditions and weighting factors. So, does such a site exist, or must I create it myself ? StuRat (talk) 22:24, 17 August 2009 (UTC)

For advice that personalised I would suggest people get their doctor to refer them to a professional nutritionist. I think there are too many factors involved for a website to give reliable results. --Tango (talk) 01:05, 18 August 2009 (UTC)

August 18


What can I feed a harvestman? Mac Davis (talk) 00:13, 18 August 2009 (UTC)

Have you read the article? I found plenty of relevant information at Harvestman#Behavior. Intelligentsium 00:33, 18 August 2009 (UTC)
Small insects and "all kinds of plant matter"? I was looking for something specific. Maybe they are just not very picky. Thanks! Mac Davis (talk) 01:01, 18 August 2009 (UTC)