The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
Specifically, what are the:
a) labs or primary researchers
b) books
c) conferences
d) one-off papers
... which have to do with the neuroscience of empathy?
Please include only primary academic sources - i.e. not popular press, unscientific publications, or the like. (Exception: popular-format books by people who are in fact real researchers are OK, e.g. most of Paul Ekman's recent books.)
Most important to me is the list of labs / researchers, preferably with links to pages where I can directly download PDFs of their papers, as the primary use for this list is as a list of places I should apply to for my PhD.
The Society for Neuroscience annual conference is in Chicago, October 17-21. You may consider attending and finding out for yourself what you like and where you should apply. I don't know if you have to be a member to attend (I'm a member anyway), but it's easy to find out. The SFN homepage is at http://www.sfn.org/ . Also, Tango's advice is really good. Just google or google-scholar for "empathy", "neuroscience", "mirror neurons", "insula", "anterior cingulate", or any combinations thereof, and you will find all you are looking for and more. And, good luck! Empathy is really a fascinating research topic. --Dr Dima (talk) 01:35, 20 May 2009 (UTC)[reply]
Hmm, I wouldn't really recommend going to SFN in order to find a school, it's kind of an overwhelming experience. Anyway, if I had to recommend a place to somebody who could get in anywhere, I would recommend University College London, with the Friths, Ray Dolan, etc. It's a hot topic, though, and there are people all over the place working on it. Looie496 (talk) 02:38, 20 May 2009 (UTC)[reply]
I'm afraid the $550 (+ hotel & travel) non-member price is a bit too steep for me; otherwise, it looks interesting... but very general. I'm only interested in (dedicating my life to) limited parts of the field of neuroscience; I feel a general conference would be a bit too shotgun. (FWIW, I'm very disappointed I missed the Berkeley conference on mirror neurons recently - I heard of it too late. I live in Berkeley, it was exactly on MNs, and it was free to boot! Sigh.)
Yes, I know how to use Google Scholar; my hope was to find somewhat more personal pointers, as GS can be a bit like finding a specific kind of needle in a stack of popularity-ranked hay. I'd love to, but practically speaking there's no way I can actually read through all the stuff there to find out the handful of people whose research is really what I want. This is something that domain knowledge is very helpful for making a lot easier. Thanks! Sai Emrys¿?✍02:48, 20 May 2009 (UTC)[reply]
Many conferences use student volunteers to man the doors, check badges and such like. When you do that, you can generally hang out at the back of the conference hall while sessions are in progress and catch most of the event for free. Obviously travel and accommodation is still an issue. But it's worth calling the conference organizers - expressing your enthusiasm and interest for this narrow field - they may be able to cut you a deal - or even offer a small grant/scholarship to help to get you there. It's definitely worth a try - especially with such a tightly focussed conference. SteveBaker (talk) 03:59, 20 May 2009 (UTC)[reply]
Ah, you're in Berkeley -- and I see from your resume that you got an undergrad degree there. The best advice I can give is to try to get a "technician" job in a lab that does something similar to what you're interested in -- there are several people there interested in social neuroscience, and all of them are top notch. There's nothing better than hands-on experience for getting a good fix on who is doing the stuff you care about most, and it's also a big plus for getting into a top-notch program. (To Steve: SFN is one of the largest academic conferences in the country, with typically about 50,000 attendees -- tightly focused is not what I would call it. It's a circus. They do provide a bit of support, but they wouldn't support somebody who isn't currently in an academic program.) Looie496 (talk) 04:26, 20 May 2009 (UTC)[reply]
Throwing a ball of wool (or twine) to a lion/tiger...
The Desert Museum puts ice in the mountain lion cages for their enjoyment if I remember correctly. A google of zoo lion enrichment found this website which says: "To stimulate predatory behavior, keepers toss hay-filled burlap sacks or cardboard boxes into the lion and tiger enclosures, which the cats pounce on and shred as if they were prey. Keepers may add olfactory interest to these items by scenting them with zebra or camel urine, perfumes, hunting lures, and herbs. In the tiger yard, keepers can hook up to a tree a giant spring covered with PVC pipe to which they attach a hard plastic Boomer Ball® or burlap sack. The tigers attack and tug at the unyielding item as if it were struggling prey. For the small cats, keepers hide meat and prey items throughout the enclosures. In the summertime, the fishing cats hunt for live goldfish released into their pools." A search for zoo enrichment might yield some more results. My guess is that a suitably sized ball of twine would generate interest from a large felid, but a zoo might not put an object which might present a tangling or choking hazard in their enclosures. If they could keep them from unravelling it enough to choke or tangle it might work. A zoo keeper would be a good person to ask. Sifakatalk03:10, 20 May 2009 (UTC)[reply]
Certainly I've seen balls in big cat zoo exhibits - so I presume they play with them. I doubt it matters much whether it happens to be a ball of wool or a plastic soccer ball or whatever. Of course this is all about zoo animals - who need all of this 'enrichment' to keep them interested in life in their tiny enclosures with all of their natural instincts being effectively turned off. Whether a wild Lion or Tiger out there in it's native habitat would give a ball of wool a second glance is an entirely different matter...I suspect the very young ones would - but not the adults. SteveBaker (talk) 03:52, 20 May 2009 (UTC)[reply]
Genus
Where can I find information describing when a genus split from others in its family? Specifically I am writing about genus Abramites, though specific information isn't neccesarily needed, just how to find it.DrewSmith What I've done07:13, 20 May 2009 (UTC)[reply]
First a remark: I'm no expert in fishs or phylogenetics, just a geneticist. I think, there is no clear answer to your question. Even for families that are "hot research topics" like hominidae the exact time points of speciation are unknown. All you can do is apply a model of the time course of genetic changes, and then come up with some rough estimate how much time it took to accumulate the differences you see. A quick googling didn't bring up any research paper that did this for Abramites, though, so I think the answer is: No one really looked into this. TheMaster17 (talk) 09:14, 20 May 2009 (UTC)[reply]
I took some pics of butterflies a couple of days ago and I wasn't able to fully identify them. I have some hints about the genus/species for two of them, but I can't be sure.
The pics were taken in southern Romania, in a forest along the Dâmboviţa river. Can anyone help? bogdan (talk) 09:45, 20 May 2009 (UTC)[reply]
I have a textbook saying the work done is the product of the force applied and the distance the object moved. But is this ultimately right? Because if I apply the same force for the same time to a faster-moving object, it would result in more work done. Or the distance moved by initial speed of the object must be subtracted from the distance? Work = Force*Time seems better to me.
Like sushi (talk) 11:44, 20 May 2009 (UTC)[reply]
No, it's right. Force*Time is momentum. Kinetic energy ("work" just means "energy added") is proportional to the square of velocity, rather than velocity itself, that is the key point. The energy required to make a 1kg object go 1m/s faster depends on the initial speed - if it starts off stationary you need 1/2mv2=1/2J, if it starts off at 10m/s you need 1/2m(112-102)=10.5J. --Tango (talk) 12:13, 20 May 2009 (UTC)[reply]
Yes. Consider a constant 10N force applied to a 1kg mass starting from rest. In the first second the mass accelerates from rest to 10 ms-1, so the work done is 50 J. In the next second the mass accelerates from 10 ms-1 to 20 ms-1, so the work done is 150 J. Gandalf61 (talk) 12:36, 20 May 2009 (UTC)[reply]
Does that mean the object moving, no force applied, also, well, having work?
An object moving with constant velocity has constant kinetic energy. Work is the increase in energy, which would be zero. --Tango (talk) 13:19, 20 May 2009 (UTC)[reply]
We must note that the formula Work = Force x Distance is not exactly right. There are two..erm.. errors. (i) It should be displacement, not distance. Note the difference. Distance is the total length of the path traversed. Displacement is just the distance between the initial and final points alone. For example, if you move on a semicircle, the distance is the length of the path, namely pi*radius. But the displacement is merely the distance between the initial and final points, which is twice the radius. (ii) This formula is valid only for a constant force. For a time varying force, this must be integrated along the path to get the work done, so keep it in mind to apply this formula only for constant forces. Rkr1991 (talk) 12:46, 20 May 2009 (UTC)[reply]
Even though I have no doubt about the formulas, it has always bugged me that KE is quadratic in velocity, and that (as a result) it's not force times duration. What your intuition is picking up on is momentum, not work; the (change in) momentum is the product of force and time, and is called impulse. --Tardis (talk) 13:09, 20 May 2009 (UTC)[reply]
Still, it doesn't cost any extra to adapt it for the more general case. I was having the same thought as DanielC. —Tamfang (talk) 02:24, 21 May 2009 (UTC)[reply]
It costs understanding for people that aren't familiar with vectors. You don't know if the OP knows anything about vectors or not. --Tango (talk) 14:54, 21 May 2009 (UTC)[reply]
Since Rkr1991 made a point of distinguishing between displacement and distance, I wouldn't bet against Rkr's understanding the basics of vectors. —Tamfang (talk) 03:22, 25 May 2009 (UTC)[reply]
How to best boil water?
If we try to heat something by burning fuel, common sense tells us that there is a certain most suitable magnitude of fire. Setting aside the effect of incomplete combustion, (if we use a mixed gas of combustable and oxygen,that will be avoided) Is it better for energy efficiency to make the fire as large as possible, or as small as possible, or there is a golden middle?
If we heat it too slowly, the heated object seems to cool down while heating, on the other hand, if we are not trying to heat all the surroundings, the heated gas seems to drive away the gas still not having cooled down yet, and thus, a loss of energy.
Like sushi (talk) 12:16, 20 May 2009 (UTC)[reply]
It's not really the size of the fire, but the efficiency of getting the heat from the fire to the water. Storm kettles are very good in that regard. The most efficient way to boil water is, I believe, with an electric kettle, though. --Tango (talk) 12:40, 20 May 2009 (UTC)[reply]
My mother's coffee-making device heats the water as it's coming out. This has the distinct advantage of not having to heat more of the water than you're going to use. This is somewhat off-topic, though, since you're asking about fire.... 90.193.232.41 (talk) 18:02, 20 May 2009 (UTC)[reply]
To efficiently use a kettle or pan of water on the gas range (or "hob"), adjust the flame so that the bottom of the vessel is heated without excess heat escaping around it. This will not make it boil faster, but will get the job done with less fuel. A larger vessel may need a larger flame. A covered pan will boil faster than an open one. The use of water from the "hot" tap is to be avoided for cooking, since it may have more dissolved undesirable substances. With an electric Calrad type burner, select a setting which again matches the size of the heated area to the size of the bottom of the pan. The same quantity of water should boil quicker in a broad pan than a narrow one due to the larger heated surface. A pan with copper cladding might heat quicker than an all steel or thick cast iron one. I suspect that a black or dark bottom pan would absorb heat faster than a white or reflective metallic one, unless the dark coating is thick enough to act as insulation. Edison (talk) 23:06, 20 May 2009 (UTC)[reply]
You would be better off just moving to a country with a mains voltage that allows decent electric kettles. In the UK you can easily get 3kW kettles that boil water far more quickly that you would on a hob. --Tango (talk) 16:25, 21 May 2009 (UTC)[reply]
Yes, those can be extremely efficient. I'm not entirely sure how they work, do they need time to charge inbetween uses? --Tango (talk) 16:25, 21 May 2009 (UTC)[reply]
Unability to lose fat?
I have been working out for the past six months and I have lost a lot of body fat and gained muscle which I am very happy. I am female and have naturally very thin arms and legs so, as you can guess, I tend to gain weight in my torso. However, all these months, my stomach and back fat have remained the same. It doesn't matter how many miles I jog, sit ups and push ups I do, kickboxing (one hour session - 5 days a week) AND playing basketball and volleyball per week.
FYI - doc said at my checkup that I am healthy and eat right but I need to lose weight in my middle. He said something about women who are apple shaped are likely to have heart attacks when older.
I know that I am genetically predispositioned (mom is short and pudgy) to have a pot belly but it possible for some people to never lose that fat? --Reticuli88 (talk) 12:50, 20 May 2009 (UTC)[reply]
Your question appears to be asking if there is a medical justification for your inability to lose fat. That requires a medical diagnosis. It is impossible to give a medical diagnosis over the Internet. If you simply want information on medical studies about fat loss, please ask specifically for information about medical studies. Do not include personal medical information. As it is, your question is too much a request for medical advice to be answered. See the guidelines at the top of the page - we will not provide medical advice. -- kainaw™12:56, 20 May 2009 (UTC)[reply]
(Non medical oppinion). A lot of the health freaks at my gym talk about hitting "plateau", for either weight loss or gain. Seems the human body gets used to certain level of regular exertion and calorie intake. They generally suggest changing your regime to suprise the body again - so either a further reduction in calorie intake (booo!), or mixing up your excercise for a while, such as swimming / lifting weights, while giving the running a rest.
Does anyone know how much the body adapts to a diet (or can point to a journal)? I know i can reduce by 500 Cal/day from the average 2500 and it makes no difference, but reducing by 1000 Cal/day causes weight loss (and 500 Cal/day extra gives weight gain). There must be research on the calorie level when these things happen on average.YobMod08:18, 21 May 2009 (UTC)[reply]
This article [[2]] may point you towards the research that prompted your doctor's comments. Also see Adipose tissue#Visceral fat. It is reportedly harder to get rid of than the one stored in other tissue. When starting an exercise program or going on a diet a lot of excess water is often lost from tissues. This is frequently mistaken for "loosing fat". Miracle diet ads create unrealistic expectation as to how fast health weight reduction can be achieved. 71.236.24.129 (talk) 10:54, 21 May 2009 (UTC)[reply]
CO2
The en:wiki (:en:Carbon dioxide) has for the meltingpoint of CO2: -78.5 °C, the german de:wiki (de:Kohlenstoffdioxid) tells us it (called Schmelzpunkt) is: -56.6 °C.
The en:wiki states for the boiling point of CO2: -56.6 °C, the german de:wiki gives for the same (called Siedepunkt) -78.5 °C.
Why did it go so wrong, and how to fix it? --VanBurenen (talk) 12:53, 20 May 2009 (UTC)[reply]
When heating a solid first it will melt, then boil. Thus the boiling temperature has to be the higher of the two. The -56C is higher (hotter) then the -78C. So I think the en:wiki is (now) right and all the other wiki's (and Wolfram Alpha) are wrong... (Or I am nuts?) --VanBurenen (talk) 13:23, 20 May 2009 (UTC)[reply]
Don't ask me, I'm about as reliable as... uh, not sure what, today. I did think that it looked pretty odd when I wrote it, but I'm sure that's what Alpha says. I'm NOT sure that it's correct, on the other hand! -- Aeluwas (talk) —Preceding undated comment added 13:53, 20 May 2009 (UTC).[reply]
Under typical lab conditions (~1 atm pressure), solid CO2 sublimes directly to the gas at -78°C, and has no liquid form. Liquid CO2 only exists under certain pressure conditions, so separate melting/boiling points only make sense at high pressures. See File:Carbon dioxide pressure-temperature phase diagram.svg. I think the problem with the en:wiki article is that is uses "melting point" as a standard field, which is incorrect in this case. So the melting point given is really the sublimation point, and note the boiling point is given for a particular high pressure.YobMod14:51, 20 May 2009 (UTC)[reply]
Hubble Propulsion
Greetings, giant brains! Please tell me where I begin to veer off course during the following series of postulates: A) The Hubble Space Telescope has a mechanism that allows it to change direction so that it can track pieces of the sky for long periods of time, and turn to other subjects when its ground-based masters desire. B) Since the Hubble cannot store years worth of propulsive material to eject and change direction, it must use forces generated by the movement of internal battery-powered mechanics to accomplish this trick. C) It is therefore possible to create a giant solar-powered, wing-flapping, bird-like spaceship to travel all over the solar system. No ejection of propulsive material required. Sappysap (talk) 13:28, 20 May 2009 (UTC)[reply]
Changing orientation is easy since it only requires a temporary change in angular momentum (which can be offset by an opposite temporary change in angular momentum in another part of the craft). Moving around (at least, moving further than the size of the craft) requires a change in linear momentum which cannot be offset by part of the craft, it needs to be offset by something leaving the craft (generally exhaust gasses from a rocket engine). --Tango (talk) 13:37, 20 May 2009 (UTC)[reply]
Hubble can't move itself from one place to another without propellant. It can ROTATE by moving its gyroscopes around. Gyroscope goes clockwise, Hubble goes counter-clockwise. And vice versa. You can't move around like that. (Sure you could throw the gyroscope out the back and the Hubble would move forward slightly, but then you'd just be using gyroscopes as propellant.) APL (talk) 13:51, 20 May 2009 (UTC)[reply]
You might be interested in ion propulsion, which can indeed create a great deal of thrust with only a little bit of ejected matter simply by ejecting it at very high speeds. --Sean16:26, 20 May 2009 (UTC)[reply]
Hubble definitely uses gyroscopes - those can be powered from the solar panels. The basic idea is that if you spin a gyroscope's wheel in one direction - equal and opposite reaction means that the even bigger, heavier satellite spins in the opposite direction. With three sets of wheels at right angles - you can rotate in any direction. Hence, no (C) - sorry. You can use this trick to rotate a spacecraft - but to accelerate it bodily - you need some reaction mass. The faster you can throw the mass away - the less fuel you need - hence Ion drives which send a very small amount of material out at extremely high speeds. You could also use a solar sail - which uses light, bouncing off of a very large mirror as the 'reaction mass'. However, Hubble doesn't need anything like that. The little propellant it has left is being conserved in order that it can be used for its final de-orbit burn at the end of its life. SteveBaker (talk) 17:57, 20 May 2009 (UTC)[reply]
Also, the emptiness of space is relative to what we are accustomed to, so the idea itself is not wholly empty. Consider the solar wind, but I do not think anybody has seriously entertained the idea of moving wings like a bird in outer space. As far as the Hubble goes, it is only the orientation of the telescope part of the satellite that Hubble manipulates with its gyroscope (not the location, which is in a fixed orbit), as SteveBaker has already essentially described.Julzes (talk) 16:11, 26 May 2009 (UTC)[reply]
Get a rotating office chair and a bowling ball. Put chair in center of room, self in chair and hold the ball. Keep your feet off the ground. Demonstrate that you can achieve B) rotary motion by swinging the ball. Try to achieve C) linear motion by any amount of flapping etc. If it's not possible in two dimensions it won't be possible in three dimensions. Cuddlyable3 (talk) 20:56, 20 May 2009 (UTC)[reply]
The trouble is that there is friction involved in the office chair scenario - and because you get different amounts of static friction than dynamic friction, you can move your arms slowly forward without the chair moving because of the high static friction - then fling them back violently and move forwards a few inches. This process can be repeated as often as needed to propel oneself around the room. However, in the almost fictionless environment of space - this trick doesn't work. SteveBaker (talk) 01:42, 21 May 2009 (UTC)[reply]
I am looking for a way to listen to music / podcasts in multiple locations in my apartment. All my music / podcasts are on my PC - in my old place I could hear the music from the speakers next to the PC anywhere in the apartment, but in my new (bigger :) ) apartment the PC sits at one end of the apartment, so as soon as I enter another room I can no longer hear it.
I am willing to lay down some cables, but wireless solutions would be wonderful (especially as the distance from my PC to the kitchen would be a good 25-30m of cable, to go around doorframes etc). I would love to have sound in two locations (in addition to the speakers next to the PC).
I have thought about just taking the audio signal from my PC and running it through some y splitters and feeding it to multimedia speakers which I would install in the other rooms. Unfortunately, this involves wiring (a lot of it, I'd have to run wires from my PC to two locations), and I'm not sure what splitting the signal like this (not to mention the 25m of cabling!) would do to the sound quality. I have also thought about feeding the signal to an amp, which would then output to two independent sets of stereo speakers - but, again with the cabling, and some cursory shopping around has revealed no amps with several speaker outputs, does this even exist? Lastly, a colleague has mentioned using some kind of internet radio, which would listen wirelessly (over my WLAN) to a stream from my PC, but I don't know where to start with such an idea.
Wireless devices specifically intended for this do exist. A quick bit of googling found this, but I make no recommendations. I believe there are various such devices on offer, so you'll need to do your own research to find what is right for you. --Tango (talk) 15:58, 20 May 2009 (UTC)[reply]
Apple's Airport Express allows wireless streaming of iTunes music. You can download add ons that let the system stream other things - Airfoil I think is one of the products. I personally have an Airport Express and it works really well for linking your iTunes up to another set of speakers - and with my laptop on the network I can use that as 1 (admittedly giant) remote control for my stereo. I must warn, however, that user reviews on the product have been mixed with many reports of the product dieing after a year or two. ny156uk (talk) 16:27, 20 May 2009 (UTC)[reply]
I dont' know if this is what you have in mind, but if you would be happy playing it through your television/whatever speakers are hooked up to your television, I bought a WDTV this weekend and have been very happy with it. You plug in any kind of USB drive and it'll play it on your television over composite or HDTV cables. It's primarily for playing computer videos on your tv, but it will play mp3s (and pictures) as well. The only problem (for music) is it doesn't seem very good at splitting up by album: you have to go by artist or folder, and then it gives the files in those folders by alphabetical order. I'm not sure if it can play playlists... Also it doesn't have a network card. You could conceivably hook up a networked drive to it (such as the My Book World Edition) but it probably makes more sense to just put all your music on a separate hard disk and attach it. I got one for $150 Canadian at Best Buy, on Amazon they are $105 US.TastyCakes (talk) 16:56, 20 May 2009 (UTC)[reply]
If you don't mind headphones you should get a pair of decent wireless headphones. I love my Sennheiser HDR-130, super comfy with good sound quality, but tend to fall down at the slightest tilt from my head (so far it has survived what, 50 1.8m drops?). --118.90.137.39 (talk) 04:58, 21 May 2009 (UTC)[reply]
My suggestion is a receiver with a multi-room output. This mean that you will plug 2 (or more, but 2 is common) pairs of speakers into the receiver, and then you can choose which of the pairs are on at any given time, regardless of the signal coming in (you can have none, either or both on at a time). I have this set up at my house: My iPod plugs into the receiver, and I can listen to it in my basement. If at any time I want to walk into my backyard and keep listening, I can hit the zone 2 button on my receiver and the outside speakers will turn on and mirror what's playing while the music continues in my basement. This also fixes your costly wiring problem, since you just need 2 speaker wires for each pair, and speaker wire is generally pretty cheap if you get it in bulk. I would stay away from many wireless devices, ESPECIALLY those fm radio transmitters, because the quality is horrible, which really really bothers me (but if you don't mind horrible sounding fuzzy music than that's the easiest solution). -Pete5x5 (talk) 16:07, 21 May 2009 (UTC)[reply]
I've been successful before in installing an audio driver that allows you to transmit audio output over Ethernet from one PC to another. I combined two programs, one that allows you to digitally redirect a virtual audio output back into a virtual audio input channel (you can also do this with a 1/8" male-male cable and your speaker output/mic in), and one that allows mic input to be broadcast over a LAN. Combine this with standard wireless Ethernet and cheap netbooks, and it's quite easy to get audio from one place to another. Dcoetzee
Human Skulls
Do people with different face shapes have different shaped skulls? Or is the difference made by skin, muscles and cartilage? —Preceding unsigned comment added by 82.44.54.169 (talk) 16:59, 20 May 2009 (UTC)[reply]
Well, I think it is a combination of factors. I agree that the skull does play a significant role. I remember when I was reading about the first face transplant the doctors saying the recipient would end up with a face that is somewhere between their old face and the donor's face since they kept the same bone structure but got new skin, etc. --Tango (talk) 17:44, 20 May 2009 (UTC)[reply]
The bones make an enormous difference. The triangle formed by the eyes and mouth are essential in both natural and machine facial recognition, and that triangle is determined almost entirely by the skull. If the skull wasn't a big deal, you could put facial prosthetics on a person to make them look just like anyone larger than themselves, but that's just not the case -- Mission Impossible to the contrary. --Sean17:49, 20 May 2009 (UTC)[reply]
Cartilage and soft tissue attaches to bone at some points and vessels feed through holes. There used to be a saying in paleontology that the fossil of an Elephant would be reconstructed to look like a Hamster because the soft tissue didn't leave a trace. This has been changed with the more recent developments in the field where similarities in fine bone structure of (recently dead) living creatures is compared to pits and holes and attachment ridges left in the fossilized bones. Bone is not a stable structure. It grows and cells get replaced. Soft tissue differences leave a trace on the bone. 71.236.24.129 (talk) 07:08, 21 May 2009 (UTC)[reply]
All the tissues impact the appearance of the face. Notice that if a person gains or loses a lot of weight, the appearance of their face changes substantially, without their bone structure changing - this shows that the face isn't determined entirely by bone structure. Dcoetzee10:46, 21 May 2009 (UTC)[reply]
mt doom
I am drawing a satirical comic parodying Lord of the Rings. Basically Sam and Frodo get into a fight at the top over who has to buy the beer back at the Shire and Frodo gets pushed in. I need to know if it is likely that his hair would catch fire before he hits the lava, assuming hobitts have a similar terminal velocity and hair burning properties as humans would and that the fall distance to the lava is sufficient to achieve terminal velocity. 65.121.141.34 (talk) 20:17, 20 May 2009 (UTC)[reply]
Hair won't catch on fire because of the free fall itself. Terminal velocity for a flailing human is too slow - it won't generate enough friction, as evidenced by all the skydivers which reach terminal velocity without catching fire. In the absence of a spark, you need to get a substance to the autoignition temperature in order for it to catch fire. I couldn't find a figure for the autoignition temperature of hair, but for paper it's around 450 F (230 C - although some sources claim it's higher, around 840 F/450 C. It of course depends on the type of paper, etc). Lava can get up to 2,200 F (1,200 C), so it might be reasonable to claim that at some point above the lava the temperature reaches the 450-840 F range for autoignition of paper. If hair's autoignition temperature is similar to paper, hair should spontaneously ignite at that point. How long it'll be on fire will depend on how far away from the lava the temperature reaches the autoignition temperature. But a satirical comedy featuring hobbits in a magical universe probably can take some license with the facts ;-). -- 128.104.112.117 (talk) 20:50, 20 May 2009 (UTC)[reply]
I actually got it from averaging and rounding the 424-474 F range listed in the autoignition temperature. But I knew about Fahrenheit 451 - in fact footnote 1 in that article is where I got the "some sources claim it's 840 F" info. -- 128.104.112.117 (talk) 15:56, 21 May 2009 (UTC)[reply]
Is it possible to be good at sport gamble or is it just good luck? Since a player is competing against the mob and the mob is always right, is it possible?--88.6.117.202 (talk) 20:52, 20 May 2009 (UTC)[reply]
The "mob" isn't always right. The odds are based on what the mob thinks is likely to happen, if you know more than the mob then you can profit (consistently - anyone can profit inconsistently with just luck). You usually can't know more just by being clever, you need better sources of information. If you have contacts involved in the sport feeding you information (eg. "so-and-so's injury is worse than they're making out, he probably won't last the whole match") you can get an advantage. Personally, I prefer to gamble on things where I can increase my own chances using skill - eg. poker. --Tango (talk) 21:13, 20 May 2009 (UTC)[reply]
Umm, regarding the above tantalizing comment, and this little tidbit and reviewing Poker, Betting (poker) and Bluff (poker), I think there is an article opportunity here: Poker, how to play intelligently. Sorry about the short notice but I just saw your comment and thought that with all of the trivial articles we have around here that this one would stand as non-trivial, for sure. I think that you've got something to add but, that's just a guess. Ya think? -hydnjo (talk) 03:14, 21 May 2009 (UTC)[reply]
Wikipedia is not a how-to guide. There are plenty of websites offering tips on how to play poker, many of them are quite good (for a complete beginner wanting to get good enough to win money off their friends, you would need something a bit more than google to learn how to win major tournaments). --Tango (talk) 14:51, 21 May 2009 (UTC)[reply]
Like the stock-market, there are a few anomolies, but in reality it is unlikely to be worthwhile. See the efficient markets hypothesis. Sports gambling is a kind of market, and a lot of academic research by economists has been done. Anomolies include the favorite-longshot bias. It used to be possible to sometimes exploit the tote in the past, but the rules have been changed. You might in theory be able to develop a handicapping system that gave you a small advantage over chance. But, if you are smart enough to be able to do all this, then you would certainly be able to earn far more money doing something else. In reality, you will almost certainly lose money in the long run. 78.146.198.122 (talk) 21:17, 20 May 2009 (UTC)[reply]
The trick is always to exploit inefficiencies in the market. In this case, the fact that not everyone has the same information. --Tango (talk) 14:51, 21 May 2009 (UTC)[reply]
You could search the bookies for Arbitrage (spelling) opportunities whereby you bet on all outcomes and are guaranteed a (usually small) win. E.g. A league football (soccer) game has 3 outcomes. Home win, draw, home loss (or away win if you prefer). If site X has odds of 4/1 for home win, site Y has odds of 4/1 for the draw and site Z has odds of 4/1 for home loss you can put money on all possible outcomes and be guaranteed a return. These sorts of situations will occasionally come up but given the difficulty and effort of finding (and taking advantage) of them they're not really viable as a 'pursuit'. Lots of betters will use statistical tactics to hedge bets and reduce down their odds of losing, whilst trying not to reduce the value if they do win. Professional Gamblers certainly do exist, I know one. I don't know what you mean by the mob but bookmakers certainly arrange their odds so that they win regardless of the event outcome. ny156uk (talk) 21:40, 20 May 2009 (UTC)[reply]
Tango means that the odds you can get (or the line) depends on the alleged wisdom of crowds. If the Patriots are favored by 8 points over the Rams, and masses of bettors ("the mob") put money on the Patriots, then, as Ny156uk implies, the bookmakers will adjust the odds so that the Patriots are favored by 8 and one-half points, and then by 9, and so forth until the betting is roughly equal on both sides, so the bookmaker is finally sure to profit no matter who wins because he's only paying out $10 for every $11 that was bet (or so).
To answer the original anon's question, it's possible to win, yes, which can be illustrated easily if you consider illegally bribing players or referees, which certainly has happened many, many times. Unfortunately I don't know any references that discuss how many people are able to do this (more legally) for a living. Tempshill (talk) 22:35, 20 May 2009 (UTC)[reply]
Yes, one of the most effective ways of getting more information than the "mob" is to bribe people so you have a key piece of information others don't have - that so-and-so is going to throw the match. --Tango (talk) 14:51, 21 May 2009 (UTC)[reply]
When you are thinking of placing a bet of any kind, it is wise to consider the multi-billion dollar casino the "house" has managed to build - and how they raised the capital to build it. The stakes are always against you; the Bellagio didn't get built by having the odds in your favour, right? Matt Deres (talk) 01:46, 21 May 2009 (UTC)[reply]
For random games, like roulette, that is absolutely correct. There is no way to win at roulette other than getting lucky (or cheating!). The results of a horse race aren't random, though, which opens up possibilities. --Tango (talk) 14:51, 21 May 2009 (UTC)[reply]
You can win at horse racing if you base your bets on the speed of each horse rather than its form. AFAIK horse speeds are not published (presumably because that would spoil the fun), and you have to work them out for yourself. But this does work; success has everything to do with spending a few hours on your homework and very little to do with luck.--Shantavira|feed me08:20, 21 May 2009 (UTC)[reply]
The speed of a horse is not constant, otherwise you would just have to go through results for the last few weeks and find out which horses in the race you are betting on have beaten which other horses in the race previously. You don't need much of an advantage to get profitable in horse racing, the house edge isn't particularly great. It doesn't matter if you lose the occasional bet, as long as you win more than your lose. --Tango (talk) 14:51, 21 May 2009 (UTC)[reply]
I sometimes get junk mail about horse racing betting systems - where for a large subscription you get sent betting tips which have been produced by some secret system. Is there an article about thse? I'm confident that such systems do not work, but I'm curious about what the secret system may be. Similarly with other secret money-making schemes that I also get sent junk mail about. 78.146.67.27 (talk) 12:16, 21 May 2009 (UTC)[reply]
The secret system will just be a load of nonsense, if you receive anything at all after giving them your money. It is obviously a scam because anyone knowing such a system could make far more money just using it themselves than they could make selling it. --Tango (talk) 14:51, 21 May 2009 (UTC)[reply]
One "secret system" (which a sometime-gambling friend once experienced) works as follows (numbers are for example only). The scammer identifies by adverts or otherwise 400 receptive gamblers (unknown to each other), and sends each a free "exclusive" prediction of the outcome of a race. If there are 4 horses in the race he'll send 100 a prediction of horse A winning, 100 horse B and so on. After the race, 100 will think he called it correctly. He then repeats the process with another race (perhaps for a small fee), then another (for a larger fee), until he's got about 6 marks who think he really knows his stuff. Now he offers to sell them the next "prediction" either for a fairly hefty sum, or on the condition that they put on a sizeable additional bet on his behalf, or both. Assuming they fall for it, he's assured of 6 hefty fees, and/or the proceeds of at least one large winning bet that he didn't have to stake. I'm glad to say that my friend figured out the scam before committing himself to the last step. 87.81.230.195 (talk) 23:58, 21 May 2009 (UTC)[reply]
Ah! An interesting corroboration I was unaware of as I avoid most TV. FWIW, the experience I recounted occurred around 1980, but I'm sure the method (or System) has been around for a lot longer. 87.81.230.195 (talk) 11:42, 22 May 2009 (UTC)[reply]
Ya, and at the moment, she is trying to google why she is suddenly so famous after 47 million years. More than that she is surprised at why her food is taking so long to digest. Unfortunately she cannot write anything in her own article at Wikipedia because of conflict of interest. But expect a question or two here at refdesk in few days maybe, because she will know many more startling things about herself in coming days and more temptation to come and ask here. - DSachan (talk) 23:10, 20 May 2009 (UTC)[reply]
Coraline was easily one of my favourite films of the past year. Even after seeing it in normal 2-D, it was well worth the price of seeing it again in Real-D (if only for the folded paper mice at the very, very end, after the theatre was empty!). Our article says that the DVD release will include both versions, but our article about Real D Cinema indicates that that process requires some pretty heavy duty specs to show in 3-D. Are those specs only applicable to projected films (i.e. a theatre) or will the normal DVD/Blu-Ray versions be the same quality as the film? Matt Deres (talk) 01:38, 21 May 2009 (UTC)[reply]
I don't see how they can show the 3D version on a standard or HD TV screen. In movie theatres, the 3D effect is produced by displaying the left eye and right eye images with different planes of polarization - and the 3D glasses filter out the undesired image for each eye. But a TV screen can't do that. There are 3D technologies that do work with TV - for example by drawing the left-eye image in red and the right-eye image in cyan and using glasses with colored lenses - but that produces nasty flicker and weird color fringing. Alternatively, they can display left and right eye images in alternate frames and use rather expensive 'LCD shutter glasses' which alternately blank out the left and right eye images alternately - but those have to be synchronised to the video stream somehow - which entails special electronics in the video player (or in the cable between the video player and the TV) to send a signal to the glasses (typically via infra-red) to tell it which eye to blank out for the following 1/60th second (1/50th in the UK). Some company once did a similar thing with a little gadget with a rubber suction cup that you stick onto the bottom-left corner of your TV screen that picks up light from a flickering black or white square and relays it to the glasses. But the cost of shutter glasses is pretty steep - and the red/cyan glasses suck - so I can't see how they plan to do this for the DVD/BluRay market. SteveBaker (talk) 12:50, 21 May 2009 (UTC)[reply]
It will probably be red/cyan. Other films shot in the Real-d process have been released to Blu-ray in red/cyan. (example: My Bloody Valentine 3D)
Personally, I enjoy movies in red/cyan, but a lot of people have trouble converging the image, get headaches, etc. APL (talk) 16:45, 21 May 2009 (UTC)[reply]
It seems as though doing polarization-based 3D on an LCD screen would be pretty easy. LCDs require an outer polarizing layer anyway, and if you replaced it with alternating horizontal and vertical polarizers then ordinary viewing would be unaffected but H-V polarized sunglasses would send each pixel to only one eye. If they'd shipped LCDs like that from the beginning then there'd be a huge installed base of 3D ready screens now. Seems like a sad missed opportunity. -- BenRG (talk) 20:40, 21 May 2009 (UTC)[reply]
It would be pretty expensive to do that in the absence of a market demand. So many good technological ideas fail because of this kind of chicken-and-egg situation. There are no 3D TV's - so there are no 3D movies for TV - so there are no 3D TV's. It's not that we don't want 3D movies on TV - it's that we can't figure out how to get there from here. Personally, I think the LCD shutter approach is a better one for the home - it requires no change to the TV whatever - so you don't have to throw away your $3,000 80" flatscreen plasma in order to see 3D movies. But it does require an IR transmitter (about $10) and actively switching glasses (maybe $30 a pair). That would be relatively expensive if you want a lot of people to be able to watch the movie at the same time (which is why they don't do that in the 3D movie theatres) - but much MUCH cheaper than a new TV set for situations where only 3 or 4 people need to be able to watch at the same time. Also they work equally well for non-LCD TV's such as plasma, DLP, CRT, OLED, etc. But it's still a chicken-and-egg situation. Unless a whole bunch of movie-makers release video's in that format on the same day that the hardware manufacturers release the glasses - it's just not going to happen. SteveBaker (talk) 14:50, 22 May 2009 (UTC)[reply]
There are already LCD monitors (not TVs) that do that. E.g. iZ3D and the Zalman Trimon. See also [3]. There is also a small number of movies released in field sequential or sensio 3D, see [4]. You may also be interested in the Meant to be Seen 3D forums although primarily about gaming, they do have a forum for movies [5]. Most 3D rendered games can of course be played in (stereo) 3D albeit with some potential issues such as related to aiming, mouse cursors and 2D interfaces. For a long time nVidia had semi decent drivers (which they inhereted from someone I forget at the moment) supporting a variety of 3D modes. They didn't survive the Vista switch nor the switch to general purposes shaders i.e. Geforce8/9 very well and were relaunched eventually along with nVidia's shutter glasses with more limited hardware support. However now that nVidia is actually paying some attention perhaps game developers will too. There are also some decent drivers for shutter glasses from iZ3D for both ATI and nVidia although these are not free. Previously there were a variety of poor quality drivers from others that sometimes worked with ATI. Nil Einne (talk) 21:39, 22 May 2009 (UTC)[reply]
Yeah - it's really tough to do that well without help from the game programmers - the driver just doesn't have enough information to get it right. But adding it into a game isn't tough - the real problem is that it halves your frame rate - and serious gamers don't like that. Casual gamers might go for it - but they don't generally want to pay the money for high-end hardware. As games programmers, we'd rather use that horsepower to make a nicer non-stereo game than to make a 3D game for 1% of the market. Of course there is always the Virtual Boy. SteveBaker (talk) 23:32, 22 May 2009 (UTC)[reply]
Red/Cyan glasses work for me - but the color is a problem. Either you have to have very monochromatic video - or you have to strongly avoid putting bright red or cyan color into the image. If you draw a bright red bouncing ball against a black background and view it with Red/Cyan glasses, the left eye sees the ball OK - but the right eye sees nothing and the 3D effect is destroyed. Worse still, if there is (say) a flashing red light in the scene - it can make things alternately pop into and out of 3D which is enough to make you want to puke! The solution is to desaturate the video so that red becomes pink...that reduces the 3D artifacts - but makes for a less vibrant image. Red/Cyan is a gimmick - it's not a proper solution to the problem. SteveBaker (talk) 14:50, 22 May 2009 (UTC)[reply]
Well, this is depressing. :P I was really hoping the answer was going to be different. With regards to the red/cyan "solution", I wonder if the foresight of that eventuality influenced the colour-palette used in the film. There aren't very many bright colours used at all; a lot of the film is set in the dark, or the fog, and has fairly neutral colours overall. Matt Deres (talk) 14:02, 24 May 2009 (UTC)[reply]
Velocity profile of typical 12V DC electric motor
Hi,
I'm wondering what the velocity profile is of a typical 12V electric motor? I've noticed (just empirically) that relatively low speed electric motors get up to speed pretty much straight away but I'd like a slightly more quantified estimate if possible. I think this question is best expressed in an example. So lets say I buy this motor and use it to run a little car. Approx how long would it take to get to its maximum speed of ~500 RPM? For arguments sake the load is approx 2kg.
Also on a related note, how do you convert the torque specification of 5 kg-cm to Nm?
Consider the moment of angular momentum versus the torque. This should answer your question. If a motor were trying to spin up a rotor of large moment, it would take longer than if the motor were spinning free of any load. More torque would get the system up to a given rotational velocity quicker. Edison (talk) 04:55, 21 May 2009 (UTC)[reply]
Would the load make that much difference? Wouldn't the load just make it run slower? At any rate I'm not sure on how you relate the moment of angular momentum to the torque of the motor to work out the time it would take to get to the maximum speed. Because say the output shaft of the motor was attached to a solid cylinder with a moment of inertia of 1 kgm^2, wouldn't that give a constant angular acceleration: T_motor = I_cyl*alpha_cyl => alpha_cyl = T_motor/I_cyl. And since the alpha is constant wouldn't that mean it would keep on spinning at ever increasing angular velocity? When surely it has to peak out at 500RPM? And it wouldn't really make sense to say it accelerates according to alpha_cyl until it reaches 500RPM and then suddenly stops because then what is balancing out the torque of the motor? Thanks, --118.138.152.143 (talk) 07:27, 21 May 2009 (UTC)[reply]
The motor isn't lifting the weight of the vehicle vertically. Assuming you're on level ground: You need to know the frictional forces (both static and dynamic) and the air resistance (if it's significant at the speeds you expect to travel). Once you know how much force the motor has to apply to overcome those things - you can take the torque and the wheel diameter and figure out how much force there is left over to accelerate the vehicle. You know the mass of the vehicle and the force available from the motor - so you can calculate that acceleration. Then you can turn linear acceleration back into rotational acceleration (again, knowing the wheel diameter) and you'll know the rate of rpm increase. SteveBaker (talk) 12:38, 21 May 2009 (UTC)[reply]
Was the ice age cold enough?
According to Quaternary_glaciation, The earth was 8 degrees (C) cooler at the peak of the last ice age. This sent glaciers all the way down into in Upper Midwest. But such a temperature change doesn't seem to me to be enough to cause such glacial expansion. Consider Minneapolis, for instance, whose geology is influenced by past glaciation. According to Minneapolis#Geography_and_climate the average high in July is 29 C. If it were 8 degrees cooler it would still be a warm 21 C, more than enough for the snow to melt through the year. The average year-round temperature would fall to -1 C. Seems cold enough, but Fairbanks, Alaska is colder at -3C [6] and is not currently covered by glaciers. What am I missing?
The temperature changes more at the poles than at the equator so currently the poles are melting whereas the temperature has only changed a little at mid to equitorial latitudes. In an ice age the poles get much colder and the effect spreads down but the equator isn't all that much colder. The big expanse of ice causes a feedback effect cooling the area that is iced up. Dmcq (talk) 07:50, 21 May 2009 (UTC)[reply]
(edit conflict) Temperature change is not uniform. The number you reference, presumably from the plot, was for Central Antarctica. The global average change during the ice age was ~3 C, with the tropic changing much less than the poles. Central Greenland, by way of contrast saw a temperature change of ~30 C. Ice sheets grow by starting at places that are very cold and spreading outward. As they spread, the effect of covering more areas with ice and snow for more of the year often causes further cooling by reflecting sunlight into space (an albedo feedback). In addition, ice sheet growth also requires an available supply of moisture to allow for regular snowfall. Fairbanks, to use your example, is far enough North that the prevailing winds are polar easterlies. This means most of its weather comes from dry Canadian air rather than from the Pacific. As a result it is harder to form glacier there than on the East coast of North America at similar latitude, where one will get snow from Atlantic moisture. Hence ice sheet in North America start in the far northeast and grow out and down as temperatures fall. Dragons flight (talk) 07:52, 21 May 2009 (UTC)[reply]
When birds sleep...
Why do they usually turn their heads through 180 and tuck their beaks into their back feathers? Is it just to keep their faces warm, or is there a physiological reason for it? —Preceding unsigned comment added by 81.77.140.54 (talk) 08:42, 21 May 2009 (UTC)[reply]
Perhaps, it acts as a natural and ready to use pillow for them, which provides comfort (in the sense of softness) and warmth both. - DSachan (talk) 09:23, 21 May 2009 (UTC)[reply]
In Britain, for example, during the winter a large proportion of birds are killed during the nights from the cold, particularly when they are short of food and hence the energy to keep them warm. Anything that reduces their surface area will help them survive. (I remember hearing or reading that the dawn chorus intensity is in proportion to the left-over energy budget from the night). Plus, I imagine that they save energy by being able to relax the neck muscles which are no longer working to hold up the head. And like humans, when they sleep their head would droop if not supported. 78.146.67.27 (talk) 10:53, 21 May 2009 (UTC)[reply]
I suspect that it helps keep the biting insects at bay. If you've ever seen a bird on the nest being swarmed by mosquitoes and black fly. You would understand. 67.193.179.241 (talk) 20:44, 21 May 2009 (UTC) Rana sylvatica[reply]
On the topic of thunderstorms and humans
I am personally very fond of thunderstorms. They bring about a certain "charged" smell in the air, a heated and moist atmosphere and indeed, the rumbling from afar is tad soothing. I know a dozen more of my friends share this with me, and while lightning striking nearby does affect us all in similar way, I was keen on asking a question more related to thunderstorms from afar: Shouldn't I feel less enthusiastic when I know a thunderstorm is about to come? Most animals seek shelter, I can't imagine too many of them enjoy the ordeal, but while some humans retain the fright of thunderstorms, many (most, according to my original research) don't. The precautionary signs come off in a comfortable way. What is to be attributed for my experiences? Simply that I've never experienced anything to teach me otherwise, or that a more built-in switch has been dulled over generations of having shelter? Thank you in advance. 90.149.144.55 (talk) 10:34, 21 May 2009 (UTC)[reply]
I'm just speculating here, but it seems to me that if you're a human-sized animal, you really don't worry about thunderstorms too much. The chance of encountering a lightning strike in our natural habitat (the savannahs) is very small, and there isn't much shelter to speak of around. It's probably even a good time to hunt for certain animals. Dcoetzee10:39, 21 May 2009 (UTC)[reply]
Well, one of the cool (and really comparatively advanced) things about us humans is that we are capable of ignoring or overriding our instincts based on the circumstances and rational thinking. Animals aren't very good at that. I mean, when we get angry, horny or scared, we can still function properly -- we don't start fighting, screwing or running away at the drop of a hat as soon as the urge strikes us. (Well, some people do, but people with that poor impulse control are generally trouble, and in trouble.) I was a little scared of thunderstorms when I was a kid; these days, like you, I love 'em. A part of it is probably the fact that I know I'm safe, and while I haven't examined my feelings very closely, I wouldn't be surprised to find that I'm still a little scared somewhere deep inside, but knowing that I'm safe, I can enjoy the thrill -- not unlike going on a roller coaster ride at an amusement park. -- Captain Disdain (talk) 11:17, 21 May 2009 (UTC)[reply]
Captain, i respectfully disagree with "animals aren't very good at that". Any plant or animal can be aclimatized, habituated or get used to, any stimulus within thier physiological limits. Again, HUMANS ain't so special. 67.193.179.241 (talk) 20:51, 21 May 2009 (UTC)Rana sylvatica[reply]
Sure, animals can get used to all kinds of things, but there's a great conceptual -- and cognitive -- difference between becoming acclimatized to something and making an actual case-by-case decision to disobey the instinct. The latter tends to require abstract reasoning skills. -- Captain Disdain (talk) 23:32, 21 May 2009 (UTC)[reply]
I suspect (without evidence) that we're 'wired' to seek shelter in the case of storms - which means that something in our brains makes us feel uncomfortable out in bad weather and comfortable when we reach shelter. If our emotional systems "reward" us for achieving an instinctual goal, that would be no surprise. We feel similarly comfortable after eating, sex and other such activities. It seems reasonable then that when we hear a storm and are sheltered - that we feel good about that. SteveBaker (talk) 12:31, 21 May 2009 (UTC)[reply]
I think all the answers above are very good. I would only add that thunderstorms may engage our higher brain functions as well. We live in an age that allows us unprecedented communications abilities; we can vicariously experience almost anything we care to imagine, but there's something to be said for the first hand, totally immersive experience of being within a powerful thunderstorm. For an old atheist like myself, it's probably as close as I'll ever come to experiencing something of that kind of terrible power. The kind of awe that power can elicit is probably not too far from an old-time fire-n-brimstone religious experience. Matt Deres (talk) 13:38, 21 May 2009 (UTC)[reply]
The fear factor is partly situational, I think. I ordinarily don't have any fear of thunderstorms, but I've been caught in exposed positions a couple of times -- once on a mountain pass with lightning striking all around and numerous lightning-blasted trees beside the trail -- and it definitely got my adrenaline going. Regarding the smell, I think it comes more from rain on dry ground than from ozone. Looie496 (talk) 16:31, 21 May 2009 (UTC)[reply]
Rain on dry ground happens in any sudden downpour. If the smell is unique to thunderstorms then it is more likely from the ozone. That would require lightning to be nearby, though, you wouldn't get any ozone from a thunderstorm several miles away. --Tango (talk) 23:25, 21 May 2009 (UTC)[reply]
There is some element of instinct going on here. When the weather outside is utterly diabolical - storm, rain, etc. I feel very good about curling up on the sofa with a good book or vegging out watching TV. When it's gorgeous weather outside, I find it very difficult to do those things - even though I have no intention of going outside. That's not the rational part of my mind doing that - because if you're indoors anyway, what the heck does it matter what's going on outside? SteveBaker (talk) 14:36, 22 May 2009 (UTC)[reply]
Avoiding sexual arousal
I'm not sure if this is science or not. I took a guess. Anyway, my friend has two problems. One, she gets aroused very easily by vibrating buses - something which she finds intensely uncomfortable, especially as she has to take a bus to university every day. Secondly, she has wet dreams, which again, she doesn't enjoy. Is there any way to control or prevent either of these? Vimescarrot (talk) 10:28, 21 May 2009 (UTC)[reply]
Some people just happen to be very easily sexually stimulated by certain stimuli. I'm not aware of any treatment for this, although she can talk to her doctor about it if she feels comfortable doing so (I do know that there are some drugs that decrease libido - this is generally listed as a negative side effect - but I don't know if she'd want it to be impeded all the time). Generally, we can't give medical advice here. The only suggestion I can think of is to bring along a book or a music player or something to help divert her attention, and if possible to seek a more comfortable alternative to the bus. Dcoetzee10:35, 21 May 2009 (UTC)[reply]
Maybe she just needs more sex, duo or solo? Or does she have religious reasons for abstaining? If you are a male friend, are you sure this is genuine and isnt just a come-on? 78.146.67.27 (talk) 10:56, 21 May 2009 (UTC)[reply]
Generally, if someone is abstaining from sex for reasons they aren't willing or able to disclose and gets very disturbed by arousal or wet dreams, I would consider that a kind of a warning sign. I could speculate, but what with the information available to us being second-hand and especially that whole medical advice thing, I'm gonna pass. Instead, I would recommend that she talk to a good therapist. -- Captain Disdain (talk) 11:23, 21 May 2009 (UTC)[reply]
True enough, but when the body and mind are at odds, it's an indication that one side or the other needs to be brought into alignment. The one requires a therapist, the other requires a physician; neither would benefit particularly from strangers on the internet making guesses based on second-hand information. The anon's comment was a little insensitive, but speaks to the general truth that the mind is often confused while the body seldom is. Matt Deres (talk) 13:43, 21 May 2009 (UTC)[reply]
I have heard two advices given to celibate monks troubled by sexual desire: A) Imagine that everyone is your brother or sister, and B) Picture everyone without their skin. Cuddlyable3 (talk) 13:42, 21 May 2009 (UTC)[reply]
The OP's friend isn't being aroused by specific people, though. Avoiding being sexually stimulated by the bus could be as simple as sitting it a different position. Cross or uncross your legs, maybe. Being made uncomfortable by wet dreams isn't something we can help with, though, that needs a therapist. --Tango (talk) 14:29, 21 May 2009 (UTC)[reply]
Check to see if she's figiting with her legs; bouncing one leg up and down is a common indication that someone is sexually aroused. It's considered by some to be an almost unconscious form of masturbation. If she's moving her legs all the time then she's likely sexually aroused more often than just on her way to school, and it's not just the bus (although that would indicate that the bus does a better job at pleasing her than her own legs). -Pete5x5 (talk) 16:07, 21 May 2009 (UTC)[reply]
Check to see if she's figiting with her legs; bouncing one leg up and down is a common indication that someone is sexually aroused[citation needed]. It's considered by some to be an almost unconscious form of masturbation[citation needed].
Actually, I don't know why I responded to that. I don't need to know when she's sexually aroused (she tells me anyway), and we already know why. I was just after how to stop it. Thanks for trying, though. Vimescarrot (talk) 17:02, 21 May 2009 (UTC)[reply]
Becoming physically aroused without being mentally aroused or "interested" is not a bother to me, nor is it something I prefer. Perhaps she should be a bit more comfortable with herself. If she dislikes the dreams because they are sexual, not because the interfere in her normal life or they are scary dreams, then she should also be comfortable with her own mind. Also see lucid dreaming. Mac Davis (talk) 18:42, 23 May 2009 (UTC)[reply]
The rules of thumb I know are that if its got four petals, its a member of the mustard/cabbage family, and if its got five petals then its a member of the Mallow family. Are these two rules of thumb reliable, and are there any more? I am in the UK, but such rules of thumb might apply worldwide. 78.146.67.27 (talk) 11:01, 21 May 2009 (UTC)[reply]
Those are not reliable rules and to each rule there are exceptions, BUT if the flower consists of many "florets" it is generally in the composite family. If the stem of the plant is roughly squared, then it is usually in the mint family. Can't think of exceptions to either rule but learning to use botanical keys quickly, is learning to cheat. That is, if you recognize that a plant is in family "X" then you can go to the index and find where that family is in the key. Good luck and have fun. 67.193.179.241 (talk) 21:19, 21 May 2009 (UTC) Rana sylvatica.[reply]
In cold countries such as Alaska, the surface of the sea freezes first or becomes solid ice, while the bottom of the surface still remains in liquid state. Why? —Preceding unsigned comment added by 60.53.212.205 (talk) 11:12, 21 May 2009 (UTC)[reply]
Exactly. Ice has a density of only approximately 9/10th of water, and hence when water freezes, ice being lighter rises to the top. This is of vital importance to the survival of fish and other aquatic animals. If ice had frozen from the bottom, they would have been pushed to the top, an a more dangerous environment. Now since ice freezes from the top, they can swim underneath the ice sheet. Also, don't forget to sign your posts by typing 4 '~' signs at the end :) Rkr1991 (talk) 13:04, 21 May 2009 (UTC)[reply]
Also, the sheet of ice on the top tends to insulate the water underneath and prevents total freezing. If it froze from the bottom up you would end up with the whole thing frozen. This peculiar feature of water (most substances constantly contract as they cool, water has a little bump in the graph near its freezing point) is one of the things that makes it so good for life. They have been theories about life on the moons of the outer planets based on ammonia, but ammonia doesn't have this advantage (it also lacks certain other advantages). --Tango (talk) 14:33, 21 May 2009 (UTC)[reply]
A crucial point is that (for fresh water) the maximum density of water occurs at 3.98 °C (39.16 °F), that is, several degrees above freezing. This means that the deep water is never colder than that, because colder water will rise. The same thing holds for sea water, except that the temperatures are different. Looie496 (talk) 16:40, 21 May 2009 (UTC)[reply]
Here is a graph of water density vs. temperature and pressure and based on the maximums, the point of greatest density does indeed depend on pressure. Regarding ice density, there are some other forms of ice made using varied temperatures and pressures which have higher densities than liquid water like Ice III (1.16g/cm3 (at 350 MPa)). I'm not sure if Ice III is more dense than water at 350 MPa though. Sifakatalk00:35, 22 May 2009 (UTC)[reply]
No, the same thing does not hold for sea water. For sea water, due to its salt content, the maximum density of the liquid is at the freezing point. Dragons flight (talk) 17:31, 21 May 2009 (UTC)[reply]
Interesting. I didn't know that. I wonder what's the minimum amount of salt necessary in order to make the point of maximun density coincide with the freezing point. Dauto (talk) 23:01, 21 May 2009 (UTC)[reply]
If what you are saying is true D.F., I'm not sure that implies that saltwater ice is equally or more dense than the saltwater it's in. To rule out the brine effect (the tendency for ice to exclude solutes as it freezes), I'm making a solid icecube of 125mM NaCl and I'm going to see if it floats or sinks in the same liquid solution it is made from. I'll report the results once the cube freezes entirely solid. (Later Edit:) I went and spilled my liquid solution and was too lazy to make some more so I tested my salty ice cube in tap water and it still floated, just barely. Sifakatalk00:35, 22 May 2009 (UTC)[reply]
The solid is still less dense than liquid. It is just that the point of maximum density of the liquid shifts to the freezing point of the liquid rather than several degrees above the freezing point as is seen for pure water. It is also worth noting that the solid-to-liquid density shift is very large in all cases. By contrast the temperature dependence of density within the liquid state is relatively quite small. Dragons flight (talk) 00:51, 22 May 2009 (UTC)[reply]
DF, are you saying tha the maximum density of saltwater is precisely at the freezing point, or just much nearer the freezing point than freshwater? Is there a graph for the salinity/density/freezing point relationship? I'm asking because of my fascination with the very weird properties of water in all its phases. Franamax (talk) 09:34, 22 May 2009 (UTC)[reply]
AFAIK Freezing also changes the concentration of salt because it gets squeezed into channels and oozes out. You then get water with less salt in it which again floats. Drift ice. 71.236.24.129 (talk) 09:49, 22 May 2009 (UTC)[reply]
Self-suggestibility - link to confabulation?
I'm sure I'm not the first person to say the suggestibility article reads poorly and looks to be mostly about hypnotic suggestibility. (Or, maybe the editors are just very suggestible and have been told it's god like it is. :-) )
I was wondering how it was that some - especially children - are able to think that things they imagine are actually real. Is this self-suggestibility due to confabulation? Do their minds naturally envision that, "Since I thought/envisioned it, it must be true?" What about adults? I'm not talking necessarily about the criminal who - desipte all the evidence they did it - convinces him or herself they didn't, though that may be part of it.
I would even be tempted to try to edit the article to include mention of confabulation, but I wouldn't have real sources. But, there has to be more to suggestibility than hypnotic states, doesn't there? 209.244.30.221 (talk) 13:29, 21 May 2009 (UTC)[reply]
I'll give this a shot. First off, when you say above that editors have been "told it's god" - have you been staring at any rotating coins lately? ;)
The confabulation article seems to be about manifestations of neurological impairment. This is not the case with children, rather there is an ongoing process of distinguishing imagination from reality. Recall that for the first several months of a human life, the baby is not able to even recognize the difference between itself and its environment. For many years, one depends on one's parents to explain that your dreams were only that, that the scary movie you watched was all made up, and that it's OK to walk down the stairs into a dark basement. It takes a long time for a brain to settle down and get on with the boring process of plain old living a life. Even then, many people are still compelled by their imagination and they imagine crazy realities like light bulbs and microprocessors. That's just normal neural development,
Looking at the Suggestibility article, I'm struck by the section discussing the differences between suggestible, susceptible and gullible. Confabulation may play a part there too as a pathological manifestation, but yes, you would need to assemble some sources. If you do find them, please be bold and edit away! Franamax (talk) 08:54, 22 May 2009 (UTC)[reply]
Carbon Monoxide Poisoning
Hi, I've always been curious about some of the specific points relating to carbon monoxide poisoning and have been unable to find answers elsewhere, I have five questions, any help or answers would be greatly appreciated:
Many of the long term effects of co poisoning(CoP) can take several weeks to show up, I've read that this is due to the long term effects being caused by CO debinding from hemoglobin, then becoming toxic. Is it true that this is the cause of longterm effects, and if so would being treated with hyperbaric oxygen after 48 hours, but prior to several weeks, have any benefit?(HBO has a large benefit if administered within 48 hours)
CoP can have permenant/long term effects of cognition and memory formation; in the event that these effects occur, how often are they permenant?
Related to the above, I've read that some cases of CoP present mild symptoms so that the victim is unaware that have been poisoned; supposing that such a case did cause cognitive/memory problems, would the victim be aware that they had such problems? In other words, would the person be able to tell that they something was wrong, or would they be oblivous to such things, perhaps thinking that they have become somewhat absented minded...in short, how obvious are the brain based effects of CoP?
Again relating to the above; I've read that CoP causes demylination to occur in the white matter of the brain, and I've also read that their are medicines for other disorders that can reverse the effects of demylination; given that this medicine was developed for other disorders, would it be effective in reversing the effects of CoP also?
My final question, again related to the above; in the event of long term cognitive impairments would a CT/MRI be able to detect such damage? Are there any means to estimate the ammount of damage, the possiblity of recovery, or the chance of further degradation? I've read that in the first few weeks after exposure that small pockets of atrophy can be detected in the brain, though I would imagine that in time these atrophied cells would be removed by the body; is this accurate?
Thank you for any help.
P.S. I do realize that this question could be considered "medical" in nature, to avoid giving the wrong impression; I am asking out of curiousity, not because I think I may have CoP or any other such thing:)
Phoenix1177 (talk) 14:43, 21 May 2009 (UTC)[reply]
To answer question 1: Carbon monoxide washout follows a biphasic pattern due to myoglobin binding. From this article, half times while breathing air are 236 minutes and 302 minutes; breathing 100% oxygen they are 87 minutes and 160 minutes. The CO level will be back to baseline within a couple of days. Our article "Carbon monoxide poisoning" describes the mechanisms of toxicity. The main effect is binding to haemoglobin, which reduces the oxygen-carrying capacity of blood, leading to tissue hypoxia. The other mechanisms are (probably) less important. Release of CO bound to myoglobin does indeed slow the rate at which CO in the blood falls. However this is not enough to actually raise the blood CO level. I am unconvinced that hyperbaric oxygen has "a large benefit". This study did not demonstrate superiority over high flow oxygen (FiO2 100%) at normal barometric pressure. Axl ¤ [Talk]21:42, 21 May 2009 (UTC)[reply]
Scanning western blots randomises results...
Is there an advantage to using built-for purpose gel/blot scanners from biotech companies over a regular scanner for the purpose of scanning in western blots stained with AEC stain?
We've been using an ordinary scanner, and then quantifying the bands but I notice that the same band from two different scans of the same blot divided by the first band in the blot (for normalisation purposes) can differ by as much as two-fold. It depends on the contrast settings used. Default settings don't always result in fair representations of the actual blot. How does one overcome this? ----SeansPotato Business15:03, 21 May 2009 (UTC)[reply]
If you mean an ordinary scanner in the sense of an off-the-shelf document scanner, I think that's a remarkably bad idea. Their nonlinearities are hideous. Looie496 (talk) 16:47, 21 May 2009 (UTC)[reply]
You shouldn't need anything fancy to scan in your gels and quantitate the bands. The commercial scanners are usually bundled with software that facilitates the analysis process and they come with other bells and whistles that make it worthwhile for some people to buy them. You can test for nonlinearity by just scanning the same gel a few different times and checking to make sure that you're getting similar results. Granted, if you're doing ultrasensitive measurements, Looie has a good point.
However, I think you already have a clue about why you're getting disparate results -- it sounds to me that the software you're using to adjust contrast is actually changing the information content of the image instead of just representing it differently on your display. This can be a huge problem because you're basically saturating the darkest bands to be able to see the lightest ones. If your image software is doing this, you need to either perform the quantitation on the unmodified image (you may not be able to see the band very well but the computer will be able to count up the gray levels for each pixel without a problem), or get new software!
If you just want to contrast the blot for the purpose of presentation or publication, you can do so but you should be honest and report that the image was contrasted using such-and-such program. Image manipulation can be very misleading and is pretty rampant in the scientific literature! --- Medical geneticist (talk) 16:57, 21 May 2009 (UTC)[reply]
Energy from walking feet
I read somewhere that now-a-days, many scientists have developed methods to produce and use energy in many forms, from walking human steps! Can anyone tell me how is this done? many thanks. 59.103.63.74 (talk) 23:08, 21 May 2009 (UTC)[reply]
I'm not sure what you are talking about, but I know that some wrist-watches use energy from a person's movement to self wind. This is not a new technology. Dauto (talk) 23:17, 21 May 2009 (UTC)[reply]
There are two technologies you could be describing. There are some devices that are powered by being shaken as a person moves. I also recall a design for a floor that uses the vibrations caused by people walking over it to generate power (possibly the floor of a subway station...). Which one are you interested in? --Tango (talk) 23:21, 21 May 2009 (UTC)[reply]
I think he is thinking of piezoelectrics which generate a tiny amount of electricity when mechanically compressed. Placed in everyday areas subject to compression, such as the sole of your shoe, and rectified in the right way this can be used to do small amounts so work. The available energy is usually quite small though. See also: Energy harvesting. Dragons flight (talk) 00:58, 22 May 2009 (UTC)[reply]
The anon I replied to gave a link to a description of what they were talking about, it is clearly talking about piezoelectrics. --Tango (talk) 18:23, 22 May 2009 (UTC)[reply]
May 22
does THC cause weed's smell?
I'm curious. If it doesn't, I imagine there's some future genetic engineering in the works that will be the delight of young people everywhere, and I imagine it could be very lucrative for street hustlers with biotech qualifications. John Riemann Soong (talk) 02:55, 22 May 2009 (UTC)[reply]
The large leaves have little THC content but still have the herb smell, so I'd say no, the smell is due to other chemical compounds. Of course, that's only what I've heard through my church group, I never touch the stuff. :) One of the attractions of cannabis is that it is a natural plant product that springs from the earth all by itself and delivers a gift of nature - I'm not so sure there is a big market for GMO's in that space. There are already lots of synthetic chemical products to whack your head with if you're so inclined. (I'm not) Franamax (talk) 08:19, 22 May 2009 (UTC)[reply]
If you're thinking of sniffing dogs, I would imagine expect they could be trained to smell THC if they're not already. In any case, removing every single compound likely to be detected by humans is an extremely difficult task. In other words, you could change the smell but it would likely still have a fairly unique smell. Indeed, I would expect the current smell is a combination of a large number of compounds not one single one although some may be more important then others. Most importantly perhaps, removing most of the compounds giving it a smell is likely to result I would expect in a product that doesn't 'taste' as good when the marijuana is smoked or whatever Nil Einne (talk) 08:52, 22 May 2009 (UTC)[reply]
As an analogous scenario, think about decaffeinated coffee. While some enthusiasts insist it's as tasty as regular coffee, I can tell the difference. However, removing the caffeine does not create a colorless, odorless liquid. Many other constituent chemicals contribute to the total flavor and aroma. Nimur (talk) 09:54, 22 May 2009 (UTC)[reply]
Actually I was thinking of splicing the gene complex for THC into other plants. Like say, dandelion. Because THC isn't a protein I imagine there's a slight bit of more complication than say, splicing in a fluorescent protein. Have we identified the genes that are responsible for negative feedback or regulatory genes that would inhibit the production of "too much" THC in a plant? (Like say, hemp?) John Riemann Soong (talk) 02:31, 24 May 2009 (UTC)[reply]
Hypermetropia
How to find power of corretive lens? why do we consider normal near point as object distance and the defective near point as image distance while calculating the power of convex corrective lens for Hypermetropic eye? —Preceding unsigned comment added by 61.2.178.70 (talk) 03:10, 22 May 2009 (UTC)[reply]
I assume you are asking this question with some knowledge of lenses and optics. Now consider a hypermetropic eye. The problem is that things too close are not focused on the retina. The objective is to give normal vision, where the least distance of distinct vision (D) is about 25cm. That is, if an object is placed in front of the eye as close as D, even then the eye must be able to see it. That is the limiting case, so if we satisfy for the limiting, we (theoretically at least) satisfy for all cases. So now the object is at D. But the eye can see only its own least distance of distinct vision (d) which is greater than D. Therefore, the image must be formed there. So now applying the lens formula, as you correctly suggested, we consider normal near point as object distance and the defective near point as image distance. Also don't forget to sign your posts by typing four '~'s at the end. Rkr1991 (talk) 05:07, 22 May 2009 (UTC)[reply]
Lilac bushes
I have a few lilac bushes in my front yard. I'd like to have more. Is there an easy way for me to take a cutting from one of the bushes and get another bush out of it? Dismas|(talk)05:15, 22 May 2009 (UTC)[reply]
I have no answer for you (other than talking about all my different-coloured lilac bushes) but I will say that if you're in the northern hemisphere, this is probably the time to clip off some green shoots and test directly. You could also try using a rooting hormone in the water, and while you're at the garden centre buying it, ask one of those helpful people. Franamax (talk) 09:42, 22 May 2009 (UTC)[reply]
Buddleia seeds can be easily bought, where I am at least, and grow into shrubs that look very similar to lilac bushes in my opinion. Perhaps you could harvest some lilac seeds from your bushes and grow those in pots of compost before planted them out. Other shrubs with lots of blossom also exist - I sometimes see for example a shrub that is completely covered in blue, no idea what its name is. Edit: I have looked at The Tree And Shrub Expert by D. G. Hessayon, published in the UK. Buddleia - propagate by sowing seeds in spring or sowing cuttings outdoors in autumn. The blue bush seems to be Ceanothus or 'Californian Lilac' - propagate by planting cuttings in a cold frame in summer. Syringa or 'Lilac' - also propagate by planting cuttings in a cold frame in summer. But as the UK is mostly in hardiness zone 8 or 9, and where the OP comes from is in zone 4 I think, then that advice may not apply. 78.146.162.232 (talk) 11:50, 22 May 2009 (UTC)[reply]
Lilacs grow most successfully from suckers. At the base of every lilac bush you will see shoots emerging. Get a mattack and detach the shoot from the rootstock below the soil level, then put it in a plastic bag until you are able to plant it (don't wait too long though). Then it's easy enough to just plant it and it should grow. And then you will find that, before too long, you want to get rid of said lilac bush because it's about to take over your garden! --TammyMoet (talk) 13:04, 22 May 2009 (UTC)[reply]
BTU'S produced by a conventional 4 or 6 cylinder engine
Can anybody advise how much heat is produced on the exhaust system of a conventioal 4 -6 cylinder engine at the exhaust pipe near the catalytic convertor? —Preceding unsigned comment added by Sustain6996 (talk • contribs) 07:36, 22 May 2009 (UTC)[reply]
Since the heat produced in the catalytic converter comes from reactions involving incomplete combustion products, unburnt hydrocarbons, and nitrogen oxides, I would say it depends heavily on the operation conditions of the engine and the particular fuel/air mixture. Under certain conditions (overly rich fuel/air mix and severe incomplete combustion) it could reach levels comparable to the power output of the engine, but is usually much less. This risk of producing huge amounts of heat is why car manuals have the whole "Do not drive, park, or idle the vehicle over dry grass" warning... 69.140.12.180 (talk) 15:51, 23 May 2009 (UTC)Nightvid[reply]
When you get to the smaller rivers - you start running into the "How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension" problem. When precisely does the river start? Maybe water trickles over some fields before it starts to look like a river? If the river is very crinkly, then issues of fractal dimension start to become a problem. So I doubt very much that you can say with any authority which of those 123 rivers are longer than which others...except for the biggest and most obvious ones - which we've already covered. SteveBaker (talk) 14:27, 22 May 2009 (UTC)[reply]
Eating too little fats
What would be the long term physiological or medical effects of an adult eating say only 10% of their calories as fat, instead of the 25 to 35% that is recommended? I understand that fat-deficiency was a problem in Victorian times, before margarine was invented. 78.146.162.232 (talk) 13:11, 22 May 2009 (UTC)[reply]
See rabbit starvation. It does not discuss the American West in the article, but apparently this was a condition suffered by some pioneers, even though they had a high calorie intake and the native Americans around them on the same diet were not suffering. The difference - the pioneers were discarding the fat from the meat. SpinningSpark13:25, 22 May 2009 (UTC)[reply]
From the lede paragraph of the article: Symptoms include diarrhea, headache, lassitude, a vague discomfort and hunger that can only be satisfied by consumption of fat or carbohydrates, and low blood pressure and heart rate. Are those not physiological effects? SpinningSpark14:49, 22 May 2009 (UTC)[reply]
Thanks again, but those are the symptoms. I'm wondering what physiological pathways are involved, how it might for example affect the nerves or the brain which I understand include a lot of fat, or if something like ketosis or its opposite is involved. 89.242.85.248 (talk) 19:03, 22 May 2009 (UTC)[reply]
See Essential fatty acid. There may also be some links you can track down in the articles on Omega-3 and Omega-6 fatty acids. I'm not convinced that someone taking in only 10% of their calories in fat would have any adverse physiological effects unless the fat source was completely deficient in Omega-3 and Omega-6 fatty acids. The body can otherwise make other lipid molecules it needs. Do you have any references for fat-deficiency in Victorian times? Also, the issue of "rabbit starvation" applies to a special condition of a diet largely composed of "lean meat coupled with a lack of other sources of nutrients" (i.e. presumably also lacking in carbohydrates and certain vitamins) which isn't really directly related to what the OP is asking. --- Medical geneticist (talk) 13:36, 23 May 2009 (UTC)[reply]
Consuming less than twenty percent of calories from fat will almost invariably cause the carbohydrate intake to be too high. Very high carbohydrate diets (such as those obtaining more than two-thirds of calories from carbohydrates) can adversely impact lipid profiles, increasing triglycerides and suppresses HDL cholesterol. The Institutes of Medicine said this in 2005:
The AMDR for fat and carbohydrate is estimated to be 20 to 35 and 45 to 65 percent of energy for adults, respectively. These AMDRs are estimated based on evidence indicating a risk for coronary heart disease (CHD) at low intakes of fat and high intakes of carbohydrate and on evidence for increased risk for obesity and its complications (including CHD) at high intakes of fat. Because the evidence is less clear on whether low or high fat intakes during childhood can lead to increased risk of chronic diseases later in life, the estimated AMDRs for fat for children are primarily based on a transition from the high fat intakes that occur during infancy to the lower adult AMDR. The AMDR for fat is 30 to 40 percent of energy for children 1 to 3 years of age and 25 to 35 percent of energy for children 4 to 18 years of age. The AMDR for carbohydrate for children is the same as that for adults—45 to 65 percent of energy. The AMDR for protein is 10 to 35 percent of energy for adults and 5 to 20 percent and 10 to 30 percent for children 1 to 3 years of age and 4 to 18 years of age, respectively.
(http://books.nap.edu/openbook.php?record_id=10490&page=769)
The Institutes of Medicine talk about the harmful effects of both fats and carbohydrates (see the lengthy chapters beginning here and here).
The USDA says:
A low intake of fats and oils(less than 20 percent of calories) increases the risk of inadequate intakes of vitamin E and of essential fatty acids and may contribute to unfavorable changes in high-density lipoprotein (HDL) blood cholesterol and triglycerides.
"The AHA notes that in the absence of weight loss, diets high in total carbohydrate (e.g., >60% of energy) can lead to elevated triglycerides and reduced HDL cholesterol. These effects do not occur with substitution of monounsaturated or polyunsaturated fats for saturated fat. NCEP suggests that monounsaturated fat
can be up to 20% of total energy and polyunsaturated fat up to 10% of total energy."
(http://www.diabetes.org/uedocuments/ADACardioReview4.pdf)
In reducing fat, it would be better to compensate with calories from protein than carbohydrate. In conclusion, Atkins might not have been right about fats and proteins, but he was right about carbohydrates. There is no doubt that they are bad for you. The only question is whether increasing fat or protein might be worse. They might come with useful nutrients (e.g., minerals or antioxidants), but carbohydrates themselves have no benefit except to meet calorie needs. This list of effects was the best that the FAO could come up with (most of the effects apply to the digestion of fiber, a beneficial carbohydrate that provides few if any calories).
What would happen if a man with a double-barreled name married? What would the woman be named? If they had a child, what would the child be named? 143.238.237.25 (talk) 13:39, 22 May 2009 (UTC)[reply]
It's up to the couple. There may be legal restrictions on what they can choose, though. A German court has recently upheld a ban on triple-barrelled names [8]. --Tango (talk) 13:50, 22 May 2009 (UTC)[reply]
The world population is still increasing, even though not quite as fast as previously forecast. How long will it be using current population projections before the earth can no longer produce enough food for its inhabitants? I heard David Attenborough say on tv that the worlds population was only about 2 billion when he was born rather than the 6 or approaching 7 billion now. A world packed with the maximum number of people would be like hell. 78.146.162.232 (talk) 14:35, 22 May 2009 (UTC)[reply]
You may want to read Malthusian catastrophe. People have been predicting that the Earth won't be able to sustain the growing population for years and we've haven't had a problem so far. Improved agricultural technologies allow increase yields that will probably keep up with population growth until the population levels out. There are plenty of people going hungry in the world but that isn't due to lack of food, it is due to food not getting where it is needed (generally due to politics). --Tango (talk) 14:57, 22 May 2009 (UTC)[reply]
With enough technology applied to the problem I guess we could have many times the current population of the earth fed so if things go on as they are the earth will be utterly and totally devastated and all other non-food species above microbes extinct except as some genes saved in a bank. The earth won't run out of food but there is some very high limit on the ultimate carrying capacity of the earth, certainly 30 billion and possibly much more than a hundred billion. Most food will be grown in vats or in trays and a few cows will be kept to feed the very rich. If the population could be reduced to less than a billion, maybe 500 million, then they would be able to have good lives without constantly worrying about destroying everything. Dmcq (talk) 17:39, 22 May 2009 (UTC)[reply]
"With enough technology applied to the problem" - if that includes artificial fertilizer or fossil fuel products, then they will run out at some time. 89.242.85.248 (talk) 19:18, 22 May 2009 (UTC)[reply]
The crisis is likely to come not from the earth as a whole running out of food, but specific regions. The two greatest danger points, in my opinion, are India and sub-Saharan Africa. In India, the population continues to increase rapidly while the Green Revolution yields diminishing results and the supply of usable land has been pretty much exhausted. In Africa, the population is projected to more than double before stabilizing, and already there are continual flare-ups of famine. Looie496 (talk) 17:41, 22 May 2009 (UTC)[reply]
But a large percentage of people in S-SA are HIV positive as well, which should mitigate a lot of famine potential in the 10-20 year range right? 65.121.141.34 (talk) 19:21, 22 May 2009 (UTC)[reply]
Not necessarily. Plenty of people have children despite being HIV+, so there might not be a significant long term reduction in population. --Tango (talk) 19:57, 22 May 2009 (UTC)[reply]
(EC) With access to certain drugs the chance is greatly reduced. See [9]. Of course for a variety of reasons many pregnancies in sub-saharan Africa don't get such drugs [10]Nil Einne (talk) 21:04, 22 May 2009 (UTC)[reply]
(EC) Another big concern in a number of places including IIRC China, India and sub-Saharan Africa is the diminishing availability of fresh water caused by a variety of reasons including ground water that's being overused (deeper and deeper wheels need to be dug, contamination of water supplies, diminishing reservoir (lakes, rivers etc) levels, climate change. We may be able to partly or completely solve this by engineering crops able to grow in sea water. We may not. Only time will tell. Nil Einne (talk) 21:04, 22 May 2009 (UTC)[reply]
There are other high-tech ways to get fresh water - if you have power, a desalinization plant will work - if you are close to the sea, you could tow a gigantic iceberg into a convenient harbor and 'mine' it for water. If you have enough energy, there isn't much you can't do. SteveBaker (talk) 23:16, 22 May 2009 (UTC)[reply]
I think the 'enough energy' is a big if. I suspect if we really had unlimited energy, terraforming Mars, the moon, or a few other places would be a piece of cake. We could even build giant stations to grow food. In other words, we don't have to restrict ourselves to earth if we don't consider practicalities. While these may be several orders of magnitude more difficult then having sufficient energy to desalinise sufficient water for 7 billion people, the basic issue is the same IMHO. It's pointless talking about possibilities which even if we devote all our current efforts to them we probably couldn't achieve in 50-100 years. Nil Einne (talk) 08:49, 23 May 2009 (UTC)[reply]
By sufficient technology I mean sustainably the world could probably support many many times its current population using solar panels and wave power plus using some fast breeder reactors as backup. Fertilizer can be generated from power and of course suitably treated waste from people would also be used. I wonder what the earth would look like from space with every last spot covered with farm or power machinery of one sort or another Dmcq (talk) 20:55, 22 May 2009 (UTC)[reply]
On the subject of climate change, the area of arable land is forecast to decrease within the century. Although CO2 fertilization may have the effect of temporarily increasing crop productivity, as well as more arable land being produced in Northern Canada and Siberia, major "breadbaskets" today are forecast to decline. For example, the American Midwest is predicted to suffer major desertification with a further warming of just 1C (2F), Southern Mediterranean Europe is forecast to become much drier and hotter, the Kalahari desert is expected to expand south, the Gobi desert to expand east, and the water supplies from the Himalayan glaciers, which support farming in otherwise dry areas, are expected to nearly dissapear before the end of the century. In addition, crop and insect diseases could increase, and major staple grains, especially rice, suffer a dramatic drop in yields above a certain threshold temperature. Population load, once it increases past global supply, reaches the "final point of sustainability". After such, both supply and load must start to decrease, until load decreases sharply below the level of supply, although not everyone predicts this. Clean drinking water supplies could decrease as well, which would hinder farming. ~AH1(TCU)23:13, 22 May 2009 (UTC)[reply]
The answer has a political as well as a scientific component. Many things that are scientifically possible won't be done. Someone would have to allocate the resources. (e.g. money, energy, water, raw materials, medication). In an ideal scenario humans would all be altruistic and distribute those to benefit all. That is unrealistic, though. Despite the fact that there are mass die-offs due to war, pandemics, starvation and drought the human population in general seems to keep multiplying. There is no free lunch, though. Scientific scenarios to feed and water ever increasing numbers come at a cost. Either environmentally or in loss of life or reduced lifespans or quality of life of some populations. The more artificial components the system gets the more fragile it becomes. If you feed your entire population with food grown in vats, one good bug could wipe our a significant portion or them. BTW. Last I checked Egypt had a higher birth rate than sub-Saharan Africa. Just because s.o. is e.g. in the U.S. they should not develop the attitude "It can't happen here." Example: Atlanta, which is in an area with lots of rainfall, has grown so much that in years that have less rainfall there's water rationing. Cases of people dying because they can't pay their water bill are rare, but not unheard of. People in industrialized nations have a higher chance of having their food supply ensured, but there's no guarantee. There is also an inverse relationship between wealth and population increase. 71.236.24.129 (talk) 10:28, 23 May 2009 (UTC)[reply]
I think if we use nuclear energy, it will last a ridiculously long amount of time. Even more so if we use fusion. I'm not sure about the former, but I think with the latter we could keep growing the population until we physically run out of space, which won't be for a very long time. — DanielLC15:59, 23 May 2009 (UTC)[reply]
If the current growth trend (population doubling every 40 years) continues, each person on Earth will have thier own square meter plot of land by 2270. Livewireo (talk) 16:13, 26 May 2009 (UTC)[reply]
The current growth trend is not population doubling every 40 years - we've been sup-exponential for a while now. If growth were exponential, this graph would be completely level (give or take some minor fluctuations). --Tango (talk) 16:39, 26 May 2009 (UTC)[reply]
They are a good way of understanding how an ecosystem fits together. Such understanding is important whenever you have to consider the environmental impact of something, which we have to do quite often. --Tango (talk) 16:36, 22 May 2009 (UTC)[reply]
So you don't grow up like one of the dumb people some on the Internet laugh about, like ones who think food just comes from the supermarket, and who don't understand how the stuff grows and has to be shipped. So you understand the importance of farmers and don't grow up to build huge subdivisions with homes that cost a lot of money, but which deplete the available land to grow food.Somebody or his brother (talk) 18:13, 22 May 2009 (UTC)[reply]
Food web / pyramid does not mean food distribution or even growing, so learning them would have little or no impact on ignorance on such topics. It is a schematic representation of ecological interactions, like cats eat fish eat flies plant eggs in cat corpses/faeces, which can be useful in practical application such as ecological planning (eg, releasing ladyirds to control aphids may simply cause an increase in ladybird predators, if understanding of the food-web is insufficent) and in understandig various food scandals and recomendations (like why heavy metals appear in fish, or why DDT is banned). As with most school sciences, it is essential for anyone undertaking further scientific education, and is the sort of thing that any typically educated person should know.YobMod09:03, 23 May 2009 (UTC)[reply]
All the food that we eat is either the body of a living organism (plant or animal) or the product of a living organism (sugar, milk, honey). The plants and animals in our world must remain healthy so that we may have healthful, nutritious food. Pollutants in the ocean have reduced the quality of seafood. What we eat is affected by food chains and food webs. As a simple example, the livestock eat the grass, and then we eat the livestock. We have to know where our food comes from to ensure that it is safe.71.31.105.41 (talk) 23:29, 24 May 2009 (UTC)[reply]
Phlegm and vocal range
This morning I woke up with a laryngitis, and was able to sing a loud and clear (mf) B♭1, a note I had only been able to sing ppp in Mahler's Eight and the All-Night Vigil. I even could sing down to F1, although that was very hoarse and open to interpretation. Now that I've been up for a while, my lower range has moved up, too, but my electronic tuner still recognizes my A1. Is this because the phlegm acts as a weight on the vocal chords? — Sebastian15:28, 22 May 2009 (UTC)[reply]
Just speculation, but since I'd think that phlegm would be rather mobile when you start singing... It may be the swelling of the mucosae that adds weight to the vocal chords, and causes the frequency to drop. --NorwegianBluetalk18:10, 22 May 2009 (UTC)[reply]
Would swelling of the mucosae be the reason that, the morning after drinking heavily, some people speak in a lower tone of voice and are able to reach lower notes? Tempshill (talk) 21:14, 22 May 2009 (UTC)[reply]
I'm curious how could one most easily calculate the surface area of a person's body? Would men or women have more than the other and would tall, thin people have less than a short, fat person?TheFutureAwaits (talk) 16:30, 22 May 2009 (UTC)[reply]
The easiest way, which should be exact enough for what you need, would be to measure length and average circumference of your body parts - torso, arms, legs, and head - and add them up (neglecting the areas of your feet and the top of your head). Roughly speaking, you can think of your surface as your height times your average circumference. Since girth can easily vary by a factor of 2, while length only varies within a much narrower range, it is easy to see that a short, fat person has more surface than the tall, thin one. — Sebastian16:45, 22 May 2009 (UTC)[reply]
If you have access to a corpse, you could try peeling off a small section of skin, weighing it and measuring its surface area, then weighing the whole skin and scaling up the previous surface area accordingly. Vimescarrot (talk) 19:43, 22 May 2009 (UTC)[reply]
Bottom of feet is much thicker skin then the rest of you. Might be pretty uneven in other places too. Could throw off the calculation. Might be a decent approximation on someone who does not walk, though. I would think that perhaps you could cut up a wetsuit and measure the area of that? Also include some socks with toes and gloves made of a material that is not very stetchy. No cadavers involved. 65.121.141.34 (talk) 20:02, 22 May 2009 (UTC)[reply]
Just as a general principle, the more "spherical" the body shape, the less surface area in proportion to mass. In other words, of two people who weigh the same, the "rounder" one will generally have less skin surface. Looie496 (talk) 21:01, 22 May 2009 (UTC)[reply]
Take a vat of molten chocolate of known volume. Dip subject in vat and remove. Measure the volume lost from vat and the thickness of chocolate adhering to subject - bit of arithmetic and Hilda's your auntie. SpinningSpark00:29, 24 May 2009 (UTC)[reply]
This paper from 1952 used a formula developed by du Bois:-
weight0.425 x height0.725 x 71.84
[Weight in kg, height in m] The original reference is from 1916: DuBois D, DuBois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Medicine. 1916; 17:863-71.
And this paper uses a direct measurement technique it calls "coating and planimetry" (which seems to be surprisingly similar to my "dip in chocolate" scheme above) and makes the claim that this shows all the "formula" methods are wildly innacurate, at least for persons of African descent. SpinningSpark14:03, 25 May 2009 (UTC)[reply]
Hip anatomy
Hi is there any way in which the ilium on either side of the pelvis is referred to differently in a clinical setting? My question is how would you know what side of the ilium someone was talking about if it is only one bone? If there was for example a fracture on one side of the ilium but not the other would doctors talk about the left/right ilium? Hope this makes sense. Is there a similar way of differentiating which side of pubis or ischium someone was talking about? Thanks in advance to anyone who can help! —Preceding unsigned comment added by 139.222.240.161 (talk) 16:53, 22 May 2009 (UTC)[reply]
Take a look at Anatomical terms of location. There is a precise term for each orientation or position (e.g. the anterior distal portion of the ilium). These terms avoid the use of terminology which would be vague based on how somebody is standing/moving the limb, etc. Nimur (talk) 16:57, 22 May 2009 (UTC)[reply]
When did fruit bearing plants first evolve and what was the first fruits?
Evolution of plants doesn't cover this terribly well, but as far as I can tell, the Gingko is a good candidate. According to our articles, the first gingkos evolved around 270 million years ago, and were among the first seed-bearing plants. And having lived next to a female Gingko tree for a few years, I can tell you from unpleasant experience that they do bear fruit. Looie496 (talk) 19:43, 22 May 2009 (UTC)[reply]
According to our article: "The apricot-like structures produced by female ginkgo trees are technically not fruits, but are seeds that have a shell that consists of a soft and fleshy section (the sarcotesta), and a hard section (the sclerotesta)." --Tango (talk) 19:50, 22 May 2009 (UTC)[reply]
The Wikipedia article on dendritic cells says that these phagocytes are unique to the mammalian immune system. However, things like this and this seem to suggest other groups of animals have DCs as well. Which is right? If other groups of animals have DCs, which have them: all amniotes? all tetrapods? all jawed vertebrates? Thanks a lot. --Leptictidium (mt) 20:12, 22 May 2009 (UTC)[reply]
The adaptive immune response goes back to jawed vertebrates as you suggest, and it seems likely that would be true for dendritic cells. I don't know for how many of the more "primitive" jawed vertebrates they've been demonstrated, though. Your reference for Langerhans cells in reptiles is a good one, though. --Scray (talk) 00:15, 23 May 2009 (UTC)[reply]
Can anyone tell me the amount of pushing power a man who weighs 90 kgs and has 7 inch by 7 inch hands in psi (pounds per square inch) ? my brother says its something like 20psi but that doesnt seem right to me. Is there a way to roughly work this out?
It depends on what they are pushing...the world record for weight-lifting is around 260 kg - and that's over a length of cylindrical bar the width of the guy's hands (let's say 20cm) by maybe 4cm wide...so 260kg over 80cm2 - which is about 46 psi. Obviously that's the world record - I'd say that less than half that is perhaps reasonable. SteveBaker (talk) 23:11, 22 May 2009 (UTC)[reply]
(Edit conflict)Yes, if you first define what "amount of pushing power" really means. Since you've mentioned psi you (or the teachers who set this poorly worded homework question?) are presumably thinking of how much pressure the man can exert through his hands (since psi is pounds per square inch, a measure of pressure).
An accurate figure will depend on how well muscled he is, how he applies the pressure, and in what direction, but let's assume he's moderately strong and can push with flat hands with a total force equal to his own weight - does that sound reasonable? Think of a wrestler holding his opponent above his own head preparatory to a body slam, not an unlikely scenario, and certainly below world-class weightlifting standards.
Now, you know the linear measurements of his (two) hands, so you should be able to work out their area in square inches - you should find that the answer comes close to a round figure useful for approximate calculations. you know how much he weighs in kilos, which we've assumed is about the same as the maximum force he can exert (weight being a force). You need to convert this force to pounds, which I'm sure you can manage. You should find this comes close to another convenient round figure.
Now you need to work out how how that total force is distributed over the total area he's using to push with, how many pounds he's exerting on each square inch. The answer may surprise you, and should show that your brother has made a minor error in his working. 87.81.230.195 (talk) 23:24, 22 May 2009 (UTC)[reply]
If a 200 pound man does a hand stand then he is supporting his whole weight on the area of his two hands, which I reckon is a pressure of about 4 psi. However, as pointed out above, a weighlifter can support the same weight on a much smaller area, so they are exerting a higher pressure. And a 100 pound ballet dancer en pointe is supporting her weight on probably 2 square inches, so she is exerting a pressure of around 50 psi. So pressure is not a useful measure of "pushing power". Gandalf61 (talk) 09:45, 23 May 2009 (UTC)[reply]
Actually, since the original question was actually for pushing power, the correct answer is "power", e.g. force times velocity, or rate of energy expended per second. I think the original questioner may want to review some basic physics terminology like force, energy, power, and pressure, to decide which quantity is actually the one he/she is trying to inquire about. Nimur (talk) 12:06, 23 May 2009 (UTC)[reply]
If the questioner doesn't know whether pressure, force, power, work or energy is the thing that is to be measured - then perhaps we need to ask why the question is being asked? To what use is the answer being put? Very often, these questions are just idle curiosity - but since the numbers don't mean much, it's all rather arbitary. SteveBaker (talk) 15:33, 23 May 2009 (UTC)[reply]
Well, strictly, yes. I was interpreting "power" to just mean "ability", rather than its technical definition in physics. --Tango (talk) 17:15, 23 May 2009 (UTC)[reply]
Fancy Guppy Reproduction
I have a femal fancy guppy and a male gold swordtail, among other things. It appeared that my guppy was pregenant, and seeing no other possible candidate, assumed the swordtail was the father. I took the neccessary steps to prepare, and even moved her to a seperate breeder when I assumed she was close (before it would be to dangerous to move her though). There she sat, for nearly a month. Then one day she was skinny again! There was no evidence of a miscarriage, and there were no babies in the other compartment. The only change is that I was better able to control how much she ate, so she probably cut back on some calories, but if this were the cause, I assume she would have lost weight over time, instead of so suddenly. What happened? And now she's starting to show pregnancy signs again. This is very troubling.DrewSmithWhat I've done23:59, 22 May 2009 (UTC)[reply]
Do fish get phantom pregnancies? I know other mammals (than Humans) do, so could be. I also read that Guppies can store sperm, so can have multiple pregnancies from one mating - but this doesn't explain the spontaenous loss by itself, uness followed by multiple miscarriages.YobMod08:35, 23 May 2009 (UTC)[reply]
Could a low-cost photovoltaic cell mounted to the top or side of an electronic vending machine provide enough power to run it reliably? The machine would be indoors, but in a vestibule with glass double doors and overhead lighting during the evening (at least during the hours when it would need to run). NeonMerlin02:25, 23 May 2009 (UTC)[reply]
One important question is whether this vending machine needs to have a refrigerator in it, as it would if it's vending cold soft drinks. Tempshill (talk) 03:33, 23 May 2009 (UTC)[reply]
There are Mechanical vending machines, condom machines are often just a place to put cash, pull a handle and get your prize. Zero electricity - the room that it is in is already lit up so no need for electricity. Similarly there are apparently 'eco' vending machines but not sure how good they are (from a brief read - not entirely free of grid-electricity use - the link from google is 'blacklisted' but search for 'eco vending machine'). ny156uk (talk) 10:02, 23 May 2009 (UTC)[reply]
If the panels are directly driving the machine - then I'd say no. But if they are charging a battery that operates the machine - then perhaps if the machine is used sufficiently infrequently, it'll have time to recharge fully between 'vends' - in which case you'd be OK. But if you had a whole bunch of kids arrive at once - all wanting to buy trading cards - then you'd run the risk that the battery would go dead. I agree with Ny156uk - there have been plenty of purely mechanical vending machines where the weight of the coin against a spring releases the ratchet on of a wheel - allowing it to rotate. The purchaser drops in the coin - then turns a knob to rotate that wheel and thereby to release the product. When the wheel rotates past a certain point, it reveals a slot through which the coin drops - allowing the ratchet to re-engage against the wheel and prevent it from rotating again until another coin is dropped in. This approach is much more practical than messing around with solar panels and rechargeable batteries. SteveBaker (talk) 15:21, 23 May 2009 (UTC)[reply]
Insect identification
This tree in Bavarian countryside was entirely covered in a kind of web and had caterpillars crawling all over it, yellow to light brown with two dotted black stripes down their backs, thin, about 1.5 - 2 cm long (I think, I didn't measure them). Can anyone tell me what the caterpillars are? N p holmes (talk) 08:25, 23 May 2009 (UTC)[reply]
Thankyou. I looked at some pictures: the Small Tortoiseshell caterpillars look fatter and hairier than these (and the web was only a little thing on a couple of nettle leaves). So I'm slightly doubtful. Any other suggestion? N p holmes (talk) 10:13, 23 May 2009 (UTC)[reply]
If an air vortex has enough force to move a 150lb object 1 foot from 30 foot distance from the launcher. Is there any way to estimate how far it will be able to move the same object from 5 foot? Or is the degredation of force within a vortex unique for each vortex depending on the speed of the spin of the vortex, and the speed which it is traveling?
Some information that may help is that the starting pressure within the vortex is 14,7 psi and the speed is mach 1 and the size of the vortex is 2ft (24 inches) in diametre —Preceding unsigned comment added by 79.68.229.253 (talk) 11:43, 23 May 2009 (UTC)[reply]
Well - the air vortex is going to dissipate sideways - so the pressure will decrease as you get further away at a rate that's proportional to the increase in cross-sectional area. Probably a good estimate would be an inverse-square-law kind of thing - as you double the distance from the source, the pressure decreases by a factor of four. However, it's going to depend critically on the size of the object being moved. For an object who's cross-sectional area is small compared to the diameter of the air vortex, the area over which that pressure is exerted doesn't change as the air flow diameter increases - so the inverse-square drop in pressure equates to an inverse-square decrease in force applied. But for an object that's much larger than the airflow, as the pressure drops off, the area it's exerted onto increases at the same rate - so the force is about the same no matter how far away you are. But in truth, this is a very rough estimate. The details matter a lot. SteveBaker (talk) 15:11, 23 May 2009 (UTC)[reply]
Hmmm that helps a little but wont the slowing down of the air due to the distance decrease the impact as well? If the vortex grows at a very small rate the area effected would not change much, but the air speed would slow due to drag. how much does drag decrease air flow?
The air can really only slow down by spreading out. Think about it...if the air leaving the nozzle is moving at speed X meters per second with a cross-section of Y square meters - then the volume of air coming out of the nozzle is X.Y cubic meters per second. If it then slows down to X/2 - then the air is only moving out of the way at X.Y/2 cubic meters per second...so where does all the extra air go? As the air slows down, it's cross-sectional area has to increase at the same rate - so if the speed drops to X/2 then the cross-sectional area has to go up to 2.Y...unless the pressure is steadily increasing somehow. But if the pressure is bigger than ambient - then the air in the jet can push the ambient air out of the way - so it'll spread out. There is really no avoiding it. SteveBaker (talk) 03:50, 24 May 2009 (UTC)[reply]
Fancy swordcraft and damaged clothing...
I'm guessing not, BUT...
is it actually possible to damage clothing but not the wearer in a controlled manner ala Zorro (or many other films & shows)?
It is possible, but unlikely - especially at the speeds Zorro slashes at. Fine motor skill is handled by small muscles, while quick slashing motions is gross motor skill. The two processes are handled by different parts of the brain and executed by anatomically different muscle and tendon groups. Nimur (talk) 12:13, 23 May 2009 (UTC)[reply]
Ala zorro, very unlikely. Zorro carved complex patterns into another persons clothing; a Z. As stated above, this would take a combination of fine motor and gross motor skills. However, the kind of swordplay often seen in humorous disney films, i.e. peter pan, where peter slashs the belt off of captain hook, and his pants drop, would be a very simple maneuver. The only real difference is that in the animation it shows a slash across, while in real life it would have to be a downward slash, to cut the belt. It is unlikely this would make the pants drop though, unless the target was wearing extremely loose pants.
Calculating oversteer/drift in a car
Hi all. I'm trying to calculate the amount of oversteer of a car, based on one main variable, the centre of mass, and forward velocity.
The main result I want to achieve is to be able to calculate, for a set numbers of degrees of drifting, how the center of mass affects the forward speed and stability of the drift, so the car doesn't slide out.
I've tried to solve it in terms of opposite torques. For the front tires, I've assumed they aren't slipping, so have used the force into the drift as (coeffient of static friction)(normal force of tires)(center of rotation), and taking the centre of rotation as the intersection of the normals of the inside tires (think that's right, haven't derived it.)
The rear tires are where I'm having the most trouble. Assuming they are slipping, the only force I can think to use is mv^2/R, but I don't think that's right because there should be a force straight on, since the car is angled? And I'm not sure what figures to use for R, the center of rotation, and r, the length of the lever arm for the torque equation.
The end result I think I want it (coeffient of static friction)(normal force of tires)(center of rotation) > (mv^2/R(?))(r) so the car doesn't slide out.
On second thoughts, mv^2/R may be not a valid equation for this, instead using the kinetic friction force. But then velocity doesn't come into it at all, and it should... I think I need to use both, on thinking that sounds better.203.206.34.183 (talk) 14:07, 23 May 2009 (UTC)[reply]
I think you are dramatically underestimating the complexity of the system you're trying to analyse. In real cars, the weight is not evenly distributed over the wheels - and as the car accelerates or turns, that weight shifts as the suspension takes up the strain and the car leans or pitches. In some cars, one wheel may actually lift off the road altogether. Chassis flex and the effect of anti-sway bars change this weight shift in complicated ways. Front wheel drive versus rear wheel drive makes a difference. Static versus dynamic friction and side-wall flex in the tires complicates the answer too. This is an insanely complex thing to try to analyse mathematically. SteveBaker (talk) 14:52, 23 May 2009 (UTC)[reply]
Yeah, I know it's a heavy bit of analysis. I was planning on simplifying it by assuming the front and rear wheels are both on live axles, so they can be looked at together. It is viable for me to ignore suspension and roll affects for my problem. Rear wheel drive. Sidewall flex would be insignificant as well. I'm not looking to include every possible force, just the most significant ones. 124.169.20.149 (talk) 00:29, 24 May 2009 (UTC)[reply]
But my point is that these other things are FAR from insignificant. There are 'approximations' that are reasonable - and there is ignoring major features of the system...and you are well into realms of the latter!
I've competed in many Autocross events in my bone stock MINI Cooper'S - and videos taken by spectators clearly showed that in hard cornering (long before 'drift' set in), the inside rear wheel would lift completely off the ground. Just think about that - with that wheel off the ground, the frictional forces on the rear end of the car are halved! Later, I added a stiffer rear antisway bar (going from a 20mm torsion bar to 25mm) - that keeps that inside wheel glued to the road and that added close to a third of a g to my lateral cornering force! That's a SPECTACULAR improvement...not by any means a negligable effect and it's an extremely subtle suspension tweak. Ignoring all of these kinds of effects makes your results all but meaningless. You might just as well save yourself the effort of doing the math and just guess! SteveBaker (talk) 01:57, 24 May 2009 (UTC)[reply]
Today's featured pic
Hi, in todays (23) featured pic, it shows a volcano erupting. There's a curious thing; the smoke from the volcano is drifting to one side, while the clouds around the volcano seem to be drifting to another side. What is the explanation for this? What is happening here? 202.129.232.137 (talk) 13:56, 23 May 2009 (UTC)[reply]
My guess is that the clouds are actually flowing in the same direction as the smoke - and are being constrained by the other two islands. But as the cloud reaches the volcano, the air temperature rises steeply. Since the amount of water that the air can hold increases with temperature, the water vapor in the clouds simply evaporates.
Alternatively - if your theory as to the direction the clouds are travelling is true - then perhaps it's merely that the smoke is at much higher altitude than the clouds - and that perhaps the wind at those altitudes are blowing in a different direction from the winds at lower altitudes.
No - that's not possible. Look at Mount_Cleveland_(Alaska) and you'll see that this is a very steep-sloping stratovolcano. Now, look again at the photo - notice that the mountain isn't casting a shadow - the sun is sufficiently high in the sky that there is no shadow being cast. Next, look at the shadow of the brown stuff - you can see it cast clearly onto the mountainside beneath. With the sun being as steep as it is - that means that there much be considerable vertical distance between the smoke plume and the mountain. Look (for comparison) at the shadows of the clouds - notice that the shadow is MUCH shorter - meaning that the clouds are much closer to the ground than the smoke plume is. It's not close to the ground. SteveBaker (talk) 18:37, 23 May 2009 (UTC)[reply]
But a pyroclastic flow hugs the ground. Look at the picutre at Pyroclastic flow. You see the flow going opposite from the wind plume. Flow is determind by slope and in independent of wind. Also follow the link to pyroclastic surge and read about 'base surge. I do not think the "clouds are an active surge: I think they are the aftermatch of such a surge, basiclaly dust left in the air by teh surge that has not yet fallen out. -Arch dude (talk) 18:48, 23 May 2009 (UTC)[reply]
This image (taken at roughly the same time as the one our OP is asking about) makes it much clearer. Firstly, you can see more clearly how the low altitude clouds are being channeled by the nearby mountains (as I suggested) - which indicates much more clearly how they are moving in the same direction as the dust plume. Secondly, this photo makes it easier to see how high the dust plume is above the terrain. This photo (taken by a satellite one day later) shows that the dust plume is drifting away from the actual volcano (something that would absolutely not be possible with the 'pyroclastic flow' hypothesis...and the photo has that plume clearly labelled "Ash Plume". This video of an eruption about a year later - under very similar-looking cloud conditions makes it even more obvious. QED. SteveBaker (talk) 22:47, 23 May 2009 (UTC)[reply]
Thanks, Steve. I never thought the plume to the SW was a pyroclastic flow or surge. I thought the crescent-shaped billow to the NE might be the aftermath of such a flow or surge. However, thanks to your excellet work we now know that it is merely the leading edge of a very large area of low-lying clouds. -Arch dude (talk) 05:20, 24 May 2009 (UTC)[reply]
Oh! I see what you're saying. Yeah - now I understand where you're coming from, it seems more plausible - but then you'd still have had to explain why it's drifting in the opposite direction to the other plume...but those other photos prove it's just clouds behaving oddly because they are close to the ocean and are being funnelled around these tall mountain/islands. It's a very cool photo though. SteveBaker (talk) 14:24, 24 May 2009 (UTC)[reply]
At some point in the past few weeks I have read a quote by Taiichi Ohno that Lean Production should not be separated and codified as tools, but should be adopted by organisations as a whole system. Now that I'm writing my dissertation I can't find it, and it's driving me bonkers. Can anyone who has read any of Ohno's books identify the quote, and give me a citation for it please? Otherwise I'm going to have to re-write my dissertation in order to not miss the deadline. -- roleplayer13:59, 23 May 2009 (UTC)[reply]
Breaking stength of an extension cord.
Someone at my car club spotted a pickup truck towing an Accura using a yellow extension cord!! I was wondering whether this was really as foolhardy as it sounds. Does anyone have any idea of the breaking strain on one of those things? Some way to get a rough estimate? SteveBaker (talk) 14:23, 23 May 2009 (UTC)[reply]
Human perception has weird effects. When on the road things have a tendency to look smaller than they really are or would look in, for instance, a small room. I suspect the cord could have been far more heavy-duty than it looked, and thus able to hold vehicles together... 69.140.12.180 (talk) 15:59, 23 May 2009 (UTC)Nightvid[reply]
Well, clearly it was able to hold vehicles together, since that's what it was doing. I don't think that's in any doubt. The question is whether it can do so reliably, which isn't really a question of perception... -- Captain Disdain (talk) 16:26, 23 May 2009 (UTC)[reply]
If nothing else there's the danger that there will be damage to the cord that you can't see because it's covered by the outer insulator. APL (talk) 16:37, 23 May 2009 (UTC)[reply]
You can estimate it, but you have to make tons of assumptions. So, lets assume that it is a twisted copper wire. Copper has about 1/3 the tensil strength of steel (from memory - please verify). So, if you assume that it is safe for a 1/4" twisted steel cable to pull a car, then it should be safe for a 3/4" twisted copper cable to pull the car. You can make different assumptions and estimate away. -- kainaw™17:25, 23 May 2009 (UTC)[reply]
You mean sqrt(3)×1/4 = less than 1/2 inch. But anyway, if you've ever cut into an an extension cord you know that most of the material is not solid copper -- most of the cross-sectional area is insulation. --Anonymous, 17:55 UTC, May 23, 2009.
ALthough it is a really stupid thing to do except in a dire emervency, it is possible, using extreme care, to tow a vehicle without placing a lot of strain on the tow rope. Don't go up hill, use extremely low acceleration, and the guy in the towed vehicle must not use the brakes unless the rope is slack. Therefore, your friend may have seen someone actually do this, but it's really dumb. -Arch dude (talk) 19:00, 23 May 2009 (UTC)[reply]
Yes. It gives a tensile strength of 10.9MPa and a breaking strain of 224%. I'm not sure how to turn those into the answer we need, but I imagine someone here can. --Tango (talk) 22:31, 23 May 2009 (UTC)[reply]
Seems like it's "safe", then (this is not hauling advice). A one-ton car accelerated at no more than, say, g/4 (0-60 in 10.9 s), would be 2.45 kN, so a cylinder of radius 8.5 mm of the plastic should be able to support it. --Tardis (talk) 22:44, 26 May 2009 (UTC)[reply]
Hmm — I suppose the real issues are whether the stress is evenly distributed (it isn't, especially where the cord is bent!) and whether several lengths of cord were being used in parallel (as by looping the cord around both attachment points a few times). --Tardis (talk) 22:46, 26 May 2009 (UTC)[reply]
I've looked hard to try to find this - but without luck. The only references to it online are in other places hosting that same video. It's possible that "flying turkey" isn't the name of the creature - just a description this guy gave it in his narration - and it's also quite possible that this is the first and only time it's ever been seen. People who do these kinds of crazy deep dives often report that they see species that are new to science every time they go down. Perhaps someone else will have more luck. SteveBaker (talk) 01:43, 24 May 2009 (UTC)[reply]
I've looked at pictures in the book The Deep and found a plausible match: a sea cucumber called the "deep-sea Spanish dancer"(scientific name Enypniastes eximia). Here's a video of it in action: http://www.youtube.com/watch?v=5PdRt31FqDc 15:43, 24 May 2009 (UTC) —Preceding unsigned comment added by 69.224.113.202 (talk)
I've just read this article about a 'new' DVD technology that could allow up to 300 DVDs to be recorded on a single disk. I've had a look at the article on 5D, but as a layman I cannot understand head nor tail of it. How does this work. What is the 5th dimension and more to the point, why don't we just invent a 700D DVD that could store every movie ever made? russ (talk) 21:18, 23 May 2009 (UTC)[reply]
OK - they call it "five dimensional" but that's not what's really going on. They are saying that they are recording data using five parameters:
How far from the center of the disk are you?
How far around the circumference of this 'track' are you?
What layer are you on (they claim 10 layers)?
What color of light is reflected at this point?
How does this point polarize light if it is reflected by it?
These five numbers are what they are calling dimensions - but that's just marketing-speak. They haven't invented five-dimensional space-time (which is what Fifth dimension is talking about).
Let's examine their claims carefully:
Existing DVD's can be 'multilayer' (two layers on each of two sides - four layers in total) - so they have (1),(2) and (3) above. At each point in that three-dimensional space, there can be something that absorbs laser light or reflects it - representing either a 'one' or a 'zero' - a binary code. So all these guys are proposing is to use polarization plus color to allow each point in that 3D space to represent more than just a 1 or a 0. Contrary to what the article says, a standard 4 layer DVD can already store 17Gbytes (they said 5Gbyte?!?) - the new technology claims 1.6Tbytes - which is actually less than 100 times more than a "standard" DVD - and only 30 times more than a BluRay disk (which can only have 2 layers). So they are getting 5x more than the BluRay disk by having 10 layers instead of 2 - and that leaves only a factor of 6 gain from their fancy color and polarization tricks. So if they could distinguish 2 different colors and 3 different polarization planes (or vice-versa) - then they can reach their claimed capacity. There is no magic going on here - it's just a logical extension of what we already do.
These kinds of fancy high-capacity storage systems are claimed by researchers all the time - but 99% of them fail because they are often unable to actually deliver that in a form that's cheap to manufacture (DVD's cost about 50 cents each to make - and that includes the case, the printed inlays and shrink-wrapping!) - and which withstand the rigor of the mishandling they'll get in daily life. There are also issues of the cost of the players and whether such players will be able to play existing CD's, DVD's and BluRays as well as their new format.
So don't hold your breath waiting for these things!
By "standard DVD" I guess they mean single-layer. That also fits with them saying DVDs are 2D. The article says there are 2 polarisation angles, so I guess there must be 3 colours. While calling it 5D is, in a sense, correct, it is a little misleading since 3 of the dimensions are discrete (have only a finite number of positions). In topology discrete spaces aren't usually counted as dimensions. The article says the "material cost" would be less than 5 cents, I don't know what it would actually cost to make. I think the main flaw in this new design isn't cost, though, it's speed. There is no point having lots of data if you can't access it. Lots of storage space would be great for really high definition movies, but if you can't read 1 second's worth of data per second, it doesn't work and the article suggests data access is pretty slow. I can't think of a real purpose for this technology. I know better than to say no-one will ever find a purpose, but I'm drawing a blank. --Tango (talk) 22:41, 23 May 2009 (UTC)[reply]
Yes - I suppose you could stick 300 movies on it so you could store your entire movie collection on a handful of disks - then when you want to watch a particular movie - you tell the machine to copy the movie (S-L-O-W-L-Y) onto a conventional hard drive so you can watch it later. If the replay mechanism was (say) 10x slower than required - then you'd have to request the movie you wanted the day before you wanted to watch it...which is kinda inconvenient.
Personally, I think we're more likely to be downloading movies in the future - and the storage issue goes away...you need enough space locally to store whatever new movies you want to watch over the next few weeks - the software slowly downloads new ones on demand so you always have enough material to keep you happy. I simply don't see the value of a 1.6Tb non-recordable media. What could you possibly want to buy in one chunk that consumes that much storage space?
But bear in mind that storage capacity isn't really the limiting factor here - the cost of buying a movie is what kills you. They could already sell movies on DVD at $1 each and make a decent profit if the cost of making the movie was low enough. But we pay $20 for a DVD - that's $19.50 for the movie and $0.50 for the disk/box. Even if these things were $0 to make - the cost of the 300 movies that it would hold would still be something like $6,000. NOBODY is going to spend $6,000 on a movie disk - and the movie companies can't afford to drop the price of the actual content to the $0.10 per movie it would take to pack 300 movies onto a $30 disk. You can't even argue form the point of view of convenience. You can already buy 1Tbyte hard drives - 1.7Tbyte are presumably only about a year away. So your hard drive is by far the best place to keep movies...now it's just a matter of how to distribute them - and the Apple iTunes mechanism is by far the more likely way for this to happen. That's possible with today's tech. Take a 1Tbyte drive - with a $50 computer - pack it into a shiney white $200 box with an Internet socket and a TV video output and a little remote controller and you're done. Apple could make a product like that tomorrow if they wanted to - the only issue is pursuading the movie companies to sell their movies that way.
If such a disk format were to have a use, it would be in computer games - in the games business, we're always bumping into the limits of what we can pack onto a DVD. But lack of speed would kill us in that application. SteveBaker (talk) 23:12, 23 May 2009 (UTC)[reply]
You can already get 2TB hard drives. CD style storage media are good for transferring data, not for storing it. I'm not sure if these things are intended to be writeable to on a desktop, but if they aren't then they'll only be useful for when you want to buy a terabyte of data all at once, which no-one is likely to want to do. Games is a possibility, I suppose - you would have to fully install it to a hard drive to play, though, and at those sizes it might be easier just to sell it on a hard drive! --Tango (talk) 23:34, 23 May 2009 (UTC)[reply]
Ah - I wasn't aware that we'd hit the 2Tbyte level with hard drives - but it doesn't surprise me. Anyway - from the way I read that article, it doesn't sound like a writable version is likely...quite how you'd change the orientation of these nanoparticles in order to change the plane of polarisation seems tricky - and changing the chemistry of the particles on the fly to change the color just using a laser seems impossible. Installing a couple of Terabytes onto your hard drive would take HOURS - possibly days if this drive is as slow as we suspect. SteveBaker (talk) 01:40, 24 May 2009 (UTC)[reply]
I've had a quick read through of the actual letter in Nature ([13] subscription probably needed, I'm on a uni network). The only number they offer for speed is the recording speed of up to 1 Gbit/s (and they have an idea for dramatically increasing that), so it seems production is reasonable. They don't say how quickly it can be read, but it sounds like it could actually be quite fast (if I'm reading it right, they have a way of reading all the polarisations and colours at the same time, although I didn't fully understand that). It's a little difficult to understand - it's a scientific paper, not a technical specification, and concentrates more on how they do it rather than what it can actually do. --Tango (talk) 14:36, 24 May 2009 (UTC)[reply]
Well, they've got to be writeable to at some point! I don't know if they could be written to by a desktop drive or if you would need an expensive thing only big manufacturers could afford. It seems they are written to using a single laser, though, so they probably are writeable to at home (how reasonable the cost would be, I don't know). --Tango (talk) 16:22, 24 May 2009 (UTC)[reply]
Not in that sense. Pre-recorded CD's and DVD's are pressed out of plastic just like the old vinyl records were - I suppose that technically that is "writing to them" - but if so, then the entire content of the disk is written in a tiny fraction of a second as the plastic is pressed...it would be meaningless to talk about the "recording speed" in that case. SteveBaker (talk) 22:02, 24 May 2009 (UTC)[reply]
I have read and re-read this article. Assuming (for sake of arguement) that both an irreststible force and an immovable object did exist (perfectly, of course)and they were to meet or collide, wouldn't they just cancel each other out and the end result would be nil? —Preceding unsigned comment added by 216.154.17.116 (talk) 21:27, 23 May 2009 (UTC)[reply]
Just because you say that such things can exist doesn't mean that they can. Neither irresistable forces nor immovable objects can actually exist - so it's truly meaningless to ask what would happen. Saying "for the sake of argument" doesn't allow you to logically debate illogical impossibilities. There simply is no argument, no paradox, just some meaningless words on a page. SteveBaker (talk) 22:06, 23 May 2009 (UTC)[reply]
The paradox is proof that such concepts are nonsense. That's what paradoxes always are - proof that your assumptions are flawed. --Tango (talk) 22:28, 23 May 2009 (UTC)[reply]
The real point is that, even if both these things could exist (which they can't), they could not exist simultaneously. The existence of an irresistible force means that there's no such thing as an immovable object, because if there were, no force would be irrestistible. That's a logical contradiction. And vice-versa. So they could never exist simultaneously, not even theoretically. -- JackofOz (talk) 02:34, 24 May 2009 (UTC)[reply]
Hmmm - I suppose they could both exist if they were the same thing. An immovable object would require infinite mass (F=ma) - and an irresistable force would require infinite energy - but since E=mc2, our infinite force provider will conveniently have infinite mass...which means it's also an immovable object! Since it can't be moved - there is no paradox. SteveBaker (talk) 03:41, 24 May 2009 (UTC)[reply]
Mathematically speaking, the answer to your question is everything. For example, if an irresistible force is exerted on an immoveable object, Elvis is alive. See the Paradox of entailment for details. — DanielLC05:50, 24 May 2009 (UTC)[reply]
Thanks everyone. I think I'll just stick with "they would cancel each other out leaving nil" cause that is easier for my wee brain to handle! —Preceding unsigned comment added by 216.154.23.87 (talk) 17:56, 24 May 2009 (UTC)[reply]
I answered this question at school when I was five years old. If there were such things as an irresistible force and an immovable object, the source of the irresistible force would end up moving toward the immovable object, attracted by its own force. Totally logical answer to a seemingly impossible question. --KageTora - (영호 (影虎)) (talk) 18:06, 24 May 2009 (UTC)[reply]
A similar paradox is this: a man in Ancient China advertises the most superior weponary; his sword, which will cut down all walls, and his shield, which will defend against attacks of the strongest arrows. A customer then asks him, "what if you put your own sword to your own shield, what will happen?" The answer is that the man advertising this items has to walk away, because if the sword breaks the shield, then the shield is inferior, and if the sword does not penetrate the shield, then the sword is inferior. ~AH1(TCU)20:36, 24 May 2009 (UTC)[reply]
You are not "hit" by them . They pass through the mostly empty space that you inhabit. Sorry. That's a fact, not a personal attack.Julzes (talk) 15:18, 26 May 2009 (UTC)[reply]
The anecdotal "counterexample" (not really the right word) I was given many years ago was: You can no more imagine the I.F. meeting the I.O. than you can imagine two men, each of whom is taller than the other. Hope that helps! --DaHorsesMouth (talk) 02:35, 25 May 2009 (UTC)[reply]
If i was to put a bottle of ice in front of a fan, would the fan blow air over the bottle which would cool, and would then cool down the surroundings? Would the air about a foot in front of the fan be colder with the bottle there than without the bottle? Would it make much difference to the temperature of the air around the fan, or would it be negligible? Thanks.—Preceding unsigned comment added by 86.177.122.34 (talk) 02:47, 24 May 2009 (UTC)[reply]
If the ambient air temperature is above the temperature of the ice (I presume it is) - then the fan will gradually warm up the bottle - eventually melting the ice - and the air blown over the bottle will be cooler than ambient. Heat is moved from the air into the bottle - so the bottle warms up and the air cools down.
Important Note: Fans don't make things colder.
They stir up the air and they make lightly clothed humans feel cooler - but they don't reduce the air temperature at all. The reason that standing in front of a fan makes you feel cooler is because your body produces heat which warms up the air next to your skin. That layer of warm air insulates you somewhat from feeling the ambient air temperature directly. The fan moves that layer of warm air away so that you can feel the cooler air that's all around you - which (because the ambient air temperature is lower than body heat) makes you feel cooler. This is what meteorologists mean when they talk about "wind chill factor".
But when the ambient air temperature is above body temperature - fans don't make you feel cooler - they make you feel hotter! It's like opening an oven door! (I speak from experience - it gets HOT in Texas!) SteveBaker (talk) 03:18, 24 May 2009 (UTC)[reply]
This is all true, except that Steve forgets that air circulation also cools human skin by helping sweat evaporates faster. However, most of it has nothing to do with the question, which is about cooling of the air due to ice as affected by the fan.
The bottle of ice will absorb heat and thus cool the air around it, at a rate which depends on the difference in temperature between the bottle's surface and the air nearby. The surroundings will be cooled as the cooled air in turn cools the air around it. If a fan is mixing the air, it will bring warmer air into contact with the bottle. This increases the difference in temperature and therefore the bottle will absorb heat, and cool the air, faster. So, yes, the fan will promote cooling of the surroundings (until all the ice is gone, which will also happen faster). However, I think the difference would be negligible, perhaps not even enough to make up for the heat added by the fan motor. --Anonymous, edited 04:31 UTC and again 07:27 UTC, May 24, 2009.
"But when the ambient air temperature is above body temperature - fans don't make you feel cooler - they make you feel hotter! It's like opening an oven door! (I speak from experience - it gets HOT in Texas!) "
Are you sure that this is true as a general statement? I would only expect it to be true at near 100% humidity. APL (talk) 07:43, 24 May 2009 (UTC)[reply]
Well, I see where you're coming from - removing the humid air from around the body theoretically gives sweat a better chance to evaporate into drier ambient air...but in the height of summer, it's rarely more than 30% humidity where I live - and fans definitely seem to make matters worse when the temperature hits 100F. Fortunately, we have air conditioned houses, cars, offices and shopping malls...so it's rarely a practical problem! SteveBaker (talk) 14:18, 24 May 2009 (UTC)[reply]
Thanks for the answer. The air conditioning point raises another question. Are most houses in the USA built with air conditioning pre-installed, or do most people have to have it installed afterwards? Are there many places in America where it isnt hot enough to warrant air conditioning in the summer months. Here in the UK we can have summers that have high enough temperatures, but those summers are an exceptional rather than the rule. As it is im sure the vast majority of houses are built without air conditioning because it usually isnt hot enough. My question is how much warmer would the average summer have to be in order for most houses to have air conditioning built-in,as a general rule?
In my personal experience, the existence of central air conditioning depends on several factors:
The age of the house. Back in the day, only large buildings had central air, with most having window-mounted air conditioners. Nowadays the technology's gotten a bit cheaper.
The price of the house. Let's face it: if you're rich, and it gets hot sometimes, you're going to buy a house with central air. If you're not rich, installing the window-mounted units, though a hassle, is worth the cut in cost. From my personal experience, the richer my friend's parents, the more likely they were to have central air.
The size of the house. This is slightly related to factor #3, but important: the bigger the house/building, the harder it would be to cool it with window/wall-mounted air conditioners.
In Texas, all houses less than maybe 20 years old will have central air conditioning. Older - low-budget houses might only have one or two window-mounted units - but very, very few people would have none. We get temperatures over 100F every year - 110F is not all that unusual. I doubt you could sell a car here that didn't have A/C. However, it wasn't always this way. Quite a few people who were born here recall living in houses with "swamp coolers" which is basically a fan blowing over a wet surface - the evaporation of the water cools the air - however it also increases the humidity and promotes unhealthy mold growth in the house - so people wouldn't turn them on unless they absolutely had to. Most of the deaths from high temperatures are amongst the poor and elderly who either don't turn on their A/C because of the cost - or can't afford to get their A/C repaired when it breaks. SteveBaker (talk) 16:13, 24 May 2009 (UTC)[reply]
Cartophilia
Is there an actual cartoneurosis called "cartophilia", or is it some sort of injoke? Ottre 03:52, 24 May 2009 (UTC)
Cooler to wear long sleeves in the sun?
Is it cooler to wear a long sleeved cotton shirt or a short sleeved cotton shirt when it's say 80 or 90 deg F outside in the sun? —Preceding unsigned comment added by 76.25.202.33 (talk) 06:02, 24 May 2009 (UTC)[reply]
Arabs traditionally wear long flowing robes in the desert. Loose long baggy sleeves may keep the heat off the skin, as an umbrella would, and circulating air would remove the heat from the underside of the fabric. 89.243.84.208 (talk) 10:05, 24 May 2009 (UTC)[reply]
I believe that the 'long flowing robes' thing only really works when the air temperature exceeds body temperature - which is not the case at 80 to 90F - so I'd go with short sleeves. However, if you have light colored skin - it may be wise to cover up in strong sunlight order to avoid the risks of skin cancer. SteveBaker (talk) 14:13, 24 May 2009 (UTC)[reply]
I think you are correct, but have your numbers wrong. You don't want core body temperature, you want skin temperature. I think that's about 33C (91F), so at the upper end of the OP's range it might be helpful. Also, if you are in direct sunlight you are being heated by radiation as well as conduction from the air, so being covered from the sun helps you keep cool. Wearing baggy clothes in the shade when the ambient temperature is below skin temperature is probably not a good plan, but either sunlight or high ambient temperature can change that. --Tango (talk) 14:45, 24 May 2009 (UTC)[reply]
AIR, skin temperature depends on the distance from the heart/body core, and at room temperature the extremities are around 25 °C (77 °F). Then again talking about the temperature of a non-equilibrium system is always dicey, with molecular sublayers and the such. I suppose the skin temperature would be highly dependent on the external temperature, which then leads us back to the original question (I swear I intended this as a helpful answer initially :-D).-RunningOnBrains(talk page)15:32, 24 May 2009 (UTC)[reply]
Indeed. I think the 33 degrees value I have stored away in my head from somewhere (possibly that question not long ago about radiating heat in space) was an average. For this question, we actually want the temperature of the arms, which I don't know (does anyone have one of those forehead strip thermometers? Put one of them on your arm and let us know what is says (and give us a rough idea of the ambient temperature where you are, and what you are wearing on your arms)!). --Tango (talk) 16:14, 24 May 2009 (UTC)[reply]
Thirty three degrees appears to be in the right range. According to one study, "the epidermis layer is uniformly effected by the environmental conditions irrespective of its thickness while the subcutaneous part is more influenced by the body core temperature. Also, the skin and subcutaneous tissues thickness play an important role in the temperature regulation under different environmental conditions."152.16.16.75 (talk) 00:16, 25 May 2009 (UTC)[reply]
Remember that sunlight heats up the surface of the skin, possibly causing it to exceed 90F if exposed, and in addition it heats up the air, usually to several degrees warmer than in the shade, which is where temperature readings taken for weather condition reports are usually located. ~AH1(TCU)20:31, 24 May 2009 (UTC)[reply]
Strange blue sea creature on NSW coastline
Today I found many strange, shiny blue, frond like sea creatures at the beach. I live on the Central Coast, NSW, Australia. I've attached a picture I took of the creature (it was taken by me, on my iPhone, so sorry if it isn't the best quality). Here is a link to the image: http://img.skitch.com/20090524-874rj2bfh41pb9fn4tq3mhcdph.png
I was wondering if anyone could identify it for me,
Thanks,
Sam. —Preceding unsigned comment added by 58.107.134.227 (talk) 06:39, 24 May 2009 (UTC)[reply]
A link in the article on the G. atlanticus says that they can be "up to 6 cm", whereas the G.marginata is shown as being barely a quarter of that size. It's not clear, but I think that the IP above was probably right, some of the atlanticus specimens in google images are clearly of the size that you mention. Mikenorton (talk) 12:11, 25 May 2009 (UTC)[reply]
Theoretical lower bound of maximum member load in a truss?
We're building a bridge out of popsicle sticks as part of the Undergrad programme and in the design of the trusses I've found that different designs lead to quite different results. In some cases for a 100N load the maximum member load goes up to 200N while others only at 70N. Which led me asking, what is the theoretical lower bound of maximum member load for a given criteria? --antilivedT | C | G09:22, 24 May 2009 (UTC)[reply]
Swimming pigs
A friend of mine was relating the following factoid: pigs can't swim because their front trotters slash across their throats, opening the jugular and killing them. Is there even the slightest bit of truth to this?
That's hilarious, thanks Vimescarrot - I'm sitting here with him now, and just remembered that I myself have seen pigs swimming at the Royal Melbourne Show with little or no evidence of throat-self-slashing. Adambrowne666 (talk) 09:50, 24 May 2009 (UTC)[reply]
When watching a normal "live" broadcast, how long after an event happens before it shows up on my tv screen"?
Since most radio is local, I assume that the delay is very minor. But for a US Cable tv customer watching a "live broadcast from Rome", it might be quite a sizable delay.
I suppose I should clarify-- I'm looking for the actual answer, based on knowing about the electronics involved; I know the time it would take a truly instant broadcast at the speed of light.
The actual answer involves how long does it takes light to enter a camera, be digitized, be broadcast via satellite to New York, be received and altered, and then rebroadcast via satellite to the cable company which travels on wires to my digital cable box to my television which then re-emits the light.
I can only say that it varies by several seconds. My personal experience from switching between two television channels showing the same live events is a difference of up to around 4 seconds between the two channels. This is without a deliberate broadcast delay as far as I know (on European channels with less sensitivity than you Americans). I don't know how big the actual delay on the fastest of the two channels is. PrimeHunter (talk) 11:27, 24 May 2009 (UTC)[reply]
In some situations they actually insert several seconds of deliberate delay in live events in order to give themselves a chance to spot something going horribly wrong in the live feed and be able to cut it before it reaches viewer screens. Radio shows with live phone-ins are particularly careful about this - using up to 10 seconds of delay. SteveBaker (talk) 14:08, 24 May 2009 (UTC)[reply]
Communications satellites are typically 1.334 light-milliseconds (low earth orbit) to 0.1194 light-seconds (geostationary orbit) from the surface of the Earth. Hence there will always be a delay of at least 0.24 s in a communication via geostationary satellite: this delay is just perceptible in a transoceanic telephone conversation routed by satellite.
One satellite broadcasting system sends two carrier signals with 4-second delay between them. This enables the receiver to maintain a large buffer of the audio stream, which, along with forward error correction, helps keep the audio playing in the event that the signal is temporarily lost, such as when driving under an overpass or otherwise losing line-of-sight of any of the satellites or ground repeater stations. Cuddlyable3 (talk) 14:27, 24 May 2009 (UTC)[reply]
From the point of view of the speed of the recording and displaying electronics, you wouldn't notice the delay. If you go to a shop with a video camera display and you step into the view of a camera displayed on a TV ahead of you you'll see a very, very, very short between you moving and the image of you doing the same. Of course cable TV may well be encrypted and be decrypted by cheap hardware in your set top box which can add seconds to the delay. --203.202.43.53 (talk) 06:45, 26 May 2009 (UTC)[reply]
I have to wonder, how long of a delay could they insert before the show is no longer "live" and their claims to the contrary become legally-prosecutable false advertising? I suppose that's very much a subjective judgement call. Dcoetzee06:59, 26 May 2009 (UTC)[reply]
I'm sure the FCC (or whatever governmental broadcasting body you wish) has some sort of regulation about what can and cannot be considered "live." Livewireo (talk) 15:46, 26 May 2009 (UTC)[reply]
Why do humans need fat in their diet?
It is commonplace that humans get fat when they overeat. In other words, they can synthesise fat. Why then do humans need fat in their diet? 89.243.84.208 (talk) 10:28, 24 May 2009 (UTC)[reply]
Also, quite a few of the vitamins we need are 'fat soluable' - they are dissolved into fats that we eat - so if you have a totally fat-free diet, you can suffer rabbit starvation. 14:04, 24 May 2009 (UTC)
Fat is an important energy source. It has nine calories per gram, 2.25 times more than carbohydrates and proteins. Fat is necessary to displace carbohydrates as an energy source, and consuming less than twenty percent of calories from fat will almost invariably cause the carbohydrate intake to be too high. Very high carbohydrate diets (such as those obtaining more than two-thirds of calories from carbohydrates) can adversely impact lipid profiles, increasing triglycerides and suppresses HDL cholesterol.
The AMDR for fat and carbohydrate is estimated to be 20 to 35 and 45 to 65 percent of energy for adults, respectively. These AMDRs are estimated based on evidence indicating a risk for coronary heart disease (CHD) at low intakes of fat and high intakes of carbohydrate and on evidence for increased risk for obesity and its complications (including CHD) at high intakes of fat. Because the evidence is less clear on whether low or high fat intakes during childhood can lead to increased risk of chronic diseases later in life, the estimated AMDRs for fat for children are primarily based on a transition from the high fat intakes that occur during infancy to the lower adult AMDR. The AMDR for fat is 30 to 40 percent of energy for children 1 to 3 years of age and 25 to 35 percent of energy for children 4 to 18 years of age. The AMDR for carbohydrate for children is the same as that for adults—45 to 65 percent of energy. The AMDR for protein is 10 to 35 percent of energy for adults and 5 to 20 percent and 10 to 30 percent for children 1 to 3 years of age and 4 to 18 years of age, respectively.(http://books.nap.edu/openbook.php?record_id=10490&page=769) The Institutes of Medicine talk about the harmful effects of both fats and carbohydrates (see the lengthy chapters beginning here and here).
The USDA says:
A low intake of fats and oils(less than 20 percent of calories) increases the risk of inadequate intakes of vitamin E and of essential fatty acids and may contribute to unfavorable changes in high-density lipoprotein (HDL) blood cholesterol and triglycerides.
"The AHA notes that in the absence of weight loss, diets high in total carbohydrate (e.g., >60% of energy) can lead to elevated triglycerides and reduced HDL cholesterol. These effects do not occur with substitution of monounsaturated or polyunsaturated fats for saturated fat. NCEP suggests that monounsaturated fat can be up to 20% of total energy and polyunsaturated fat up to 10% of total energy."(http://www.diabetes.org/uedocuments/ADACardioReview4.pdf)
Foods that are high in fat tend to be palatable (they taste good) and high in calories per ounce. There are very few foods (with the exception of whole milk) that obtain a huge percentage of their calories from fat and are also high in water. This is why high intakes of fat may be associated with obesity, but studies comparing high-carbohydrate diets have produced conflicting results. Some studies, of course, show that carbohydrates are more likely to cause obesity than fats.75.89.27.94 (talk) 23:13, 24 May 2009 (UTC)—Preceding unsigned comment added by 71.31.105.41 (talk) [reply]
Thank you very much for all that, I shall try to study and comprehend that very carefully. I'm still surprised that its beneficial to eat what seems to me quite a lot of fat - I thought it was sinful in dietry terms. 89.241.155.179 (talk) 18:16, 25 May 2009 (UTC)[reply]
What has changed about agricultural practices to make the dust bowl of the 1930s something that does not seem to happen since then? Years ago the UK fens had the same problem with soil erosion, but that is never reported in the news or media now either. The fens farmers went through a phase of using very deep plowing with powerful double-engined articulated tractors in an unsuccesful attempt to stop the wind erosion, but I do not think such plows are used anymore. 89.243.84.208 (talk) 10:49, 24 May 2009 (UTC)[reply]
If I recall one of the main ecological reasons behind the dust bowl was poor agricultural practices like a lack of crop rotation. I suspect that changing back to more traditional practices will have gone a long way towards that end. I suspect the dust bowl phenomena is one of these exponential tipping-point type things, where once it gets bad it gets worse and worse and worse, but if you keep it from getting bad in the first place then it's not a problem. --98.217.14.211 (talk) 18:31, 24 May 2009 (UTC)[reply]
I'm thinking that the dust bowl occured in the first place due to overfarming; natural vegetation was removed (which holds the soil together) and new crops planted during a period of intense drought. The lore back then was that the "rain follows the plow", but that obviously did not occur, leading to the loose, dry soil blowing away. Today, there are a number of reforestation programs, which have helped to hold the soil together, so that a repeat of the dust bowl does not occur. There is one threat, however, that could cause prolonged dust bowl-like conditions in the near future. One degree Celcius (roughly 2F) of further global warming could turn much of the US Midwest into a semi-desert, meaning that the soil may blow away more easily once again, unless massive irrigation and plantation projects are farther exploited. ~AH1(TCU)20:28, 24 May 2009 (UTC)[reply]
While not quite as bad as the dust bowl, I do recall dust storms in South Dakota about 10 years ago that filled in the roadside ditches with dirt and reduced visibility to about 1/4 mile for 2-3 days. So these storms can still happen on smaller scales. 65.121.141.34 (talk) 13:53, 26 May 2009 (UTC)[reply]
Research indicates that the Raw Egg Eating Meme (REEM) originated circa 1890 with Bernarr Macfadden, the index case. The highly influential Charles Atlas became infected by 1920 and is reguarded by many historians as patient 0. In 1976 REEM went pandemic with the release of Rocky. It is now endemic within bodybuilding community. --Digrpat (talk) 20:33, 24 May 2009 (UTC)[reply]
what are the various aspects of this field instrumentation ? what are the research prospects ? Is instrumentation related to robotics ? if so how? —Preceding unsigned comment added by Srini279 (talk • contribs) 13:00, 24 May 2009 (UTC)[reply]
Instrumentation is a broad term - it can mean anything from TV cameras to little switches that turn on when a robot bumps into something...robotics are heavily dependent on good instrumentation (they'd be more likely to call them "sensors") because the computer inside is blind and deaf without them. With the rise in the applicability of robots, there is considerable research into the sensors they use. Finding novel sensors, making cheaper/lighter/lower-power-consumption/more-robust sensors and finding better ways to interface the sensors to the computer software - these are all hot research topics. SteveBaker (talk) 14:30, 24 May 2009 (UTC)[reply]
Powering a Phobos Colony
I read in this article that Phobos, with its orbit only 3000 miles from Mars and synchronized to always face the planet, is a "natural staging area for manned excursions to Mars." My question is: wouldn't it be difficult for a Phobos colony to be powered by solar energy if Mars completely encompasses the sky? Sappysap (talk) 15:02, 24 May 2009 (UTC)[reply]
One side of the moon always faces Mars - so there are several possibilities:
If you set up camp on the side of Phobos that's nearest Mars - then during your "mid-day", Mars is between you and the Sun and appears as a black disk that's blocking out the sun. During the night - the Sun isn't in your sky. However, there will be times around dawn and dusk when the Sun is low in your sky between the horizon and Mars. However, even during the day - Mars only takes up a quarter of the sky - so you'd get a few hours of sunlight in each 7.5 hour "day". However, even at midnight - Mars would be 2500 times brighter than our moon and 6400 times larger...that's quite a lot of reflected sunlight - so you'd probably get reasonable amounts of power from "marslight"...especially if you made solar panels that were most sensitive to red light.
If you set up camp on the side of Phobos that's furthest from Mars - then Mars is permenantly below the horizon and you get plenty of sunlight during the day (but no marslight at night).
You could also build tall, vertical, rotating solar panels on the North or South poles of Phobos then they would benefit from sunlight for all but maybe an hour a day when Mars gets in the way. Phobos has zero degrees of axial tilt - so unlike here on earth, the sun would never set below the horizon at the poles - the only darkness is when Mars gets in the way.
So - either put fixed solar panels on the equator as far as possible from Mars. You'll get full sunlight for almost 4 hours in every 7.5 hour "day"...or...put them on the poles and make them rotate one revolution every 7.5 hours. That's attractive because you only need to have enough battery storage to cover that one hour of darkness - and keeping the panels at 90 degrees to the incoming sunlight maximises their power production. SteveBaker (talk) 15:59, 24 May 2009 (UTC)[reply]
I believe Phobos' axial tilt it zero with respect to its orbit around Mars, not the Sun. Phobos' orbit is inclined 1 degree to Mars' equator which has an axial tilt of 25 degrees. So, if I'm visualising this correctly, that's equivalent to an axial tilt that varies between 24 and 26 degrees. I don't see how Mars would ever get in the way of the poles, though. Yes, I do! --Tango (talk) 16:09, 24 May 2009 (UTC)[reply]
Being so close to Mars, presumably there is a lot of tidal strain. Could that be used for power? I'm not entirely sure how - there is no ocean or atmosphere, so you would have to use tidal movement in the rock itself, which isn't particularly convenient. --Tango (talk) 16:03, 24 May 2009 (UTC)[reply]
That tidal strain will stress and release the rock, causing it to warm (the way a paperclip warms when you bend it back and forward). The insulated centre of the moon should be warmer than the outside, so that sets up a thermal gradient. You could, in theory, use that to run a heat engine (like an OTEC) but surely the thermal gradient will be so shallow that you wouldn't, in practice, break even. 87.114.167.162 (talk) 19:00, 24 May 2009 (UTC)[reply]
I doubt there is enough tidal strain in Phobos to be of any use given that
a) Mars gravity isn't very strong,
b) Phobos always shows the same face to Mars,
c) Phobos' orbit isn't very eccentric,
d) There isn't any large moon around Mars that could periodically tug on Phobos and steadily transfer energy to Phobos libration which would than be dissipated through tidal friction.
You probably have two lighting loops. It may be that one of those loops is being exposed to rainwater, causing a short circuit. That's a dangerous condition, and you should have an electrician look at it. 87.114.167.162 (talk) 18:46, 24 May 2009 (UTC)[reply]
I'm surprised it hasn't blown a fuze or tripped a circuit breaker - but yeah - this is very dangerous. Somewhere there could be a puddle that'll electrocute you when you step in it...also, as it dries out, there is a good chance of arcing and all sorts of other things that could cause an electrical fire. Definitely get it fixed ASAP. SteveBaker (talk) 21:55, 24 May 2009 (UTC)[reply]
Whoa, don't go overboard here! I mean, yeah, if there's an actual rainwater leak, it's dangerous and needs fixing. But it's common for fluorescent lights to malfunction in rainy weather if they're starting to fail -- my house is full of fluorescents and I see this all the time. Presumably the explanation is increased current leakage through the air when it's humid. Bill probably just needs to do the usual things for non-working fluorescents: check if they're properly in the sockets, change the tubes, check the wiring connections, replace the ballast. The latter two things are the sort of work where some people would say an electrician is necessary and others would say "learn how, then do it yourself"; I'll leave it at that. --Anonymous, 21:07 UT, May 25, 2009.
The intermittent problem could be a leak causing a short in the mains supply, but the lamps would robably keep going until the fuse or breaker interrupted the current. Do you find the fuse/breaker open? They do not, in general, reclose on their own. Absent that, we are left with the ballast, the starter, the socket, or a temporary open in the switching circuit. I doubt it is the lamp itself which is somehow sensitive to humidity or precipitation. If water is leaking into a connection such as a wire nut, insulating crud could build up. A screw terminal or push-in terminal could be loose producing intermittent operation only coincidentally related to rain. There could be an intermittent open in an underground cable, if the feed to the shop is underground, but that would likely affect all the lights. A qualified electrician could check for loose or corroded connections. The circuit should be turned off at the breaker while inspections or repairs are attempted. Edison (talk) 00:53, 26 May 2009 (UTC) Edison (talk) 00:53, 26 May 2009 (UTC)[reply]
prognostic markers
Hi I have been given the task of researching the 'prognostic markers' used in the management of breast cancer. I have no idea what the term 'prognostic markers' even means. Can anyone give me a definition please? Theres no article on them and Wiktionary doesn't seem to have heard of them either. Also if you know of any websites which may be of use for my research I would be grateful to hear about them! Cheers RichYPE (talk) 18:50, 24 May 2009 (UTC)[reply]
We should maintain a distinction between "prognosis" and "prediction" here... Prognosis assumes that a person has a disease, and that we are trying to use "prognostic markers" to tell how well or poorly they are likely to do, or whether they are likely to respond to a particular treatment. Prediction assumes that a person does NOT have a disease and we are trying to use "predictive markers" to tell whether or not they are likely to have the disease at some time in the future. While it is true that prognostication and prediction sometimes use similar assays, these are two VERY different things. --- Medical geneticist (talk) 23:36, 24 May 2009 (UTC)[reply]
Excellent point! I missed that in the prior answers, was focused on the OP. Thanks for pointing that out. --Scray (talk) 02:13, 25 May 2009 (UTC)[reply]
When I was younger, I recall reading a children's book that stated that the planet Saturn was composed of very light elements, and therefore could actually float on a hypothetical ocean that was large enough. I just did a google search, and I actually turned up this http://coolcosmos.ipac.caltech.edu/cosmic_kids/AskKids/saturnfloat.shtml
I guess I'm just looking for confirmation to this claim, because I figure that the dense core might create problems for this hypothetical scenario. ScienceApe (talk) 20:00, 24 May 2009 (UTC)[reply]
It's true. The average density of Saturn, according to Saturn, is 0.687 g/cm³, compared to 1 g/cm³ for water. There is a slight question regarding how you define the edge of a gas giant, but there is enough margin of error there that any reasonable definition will still give it a density less than that of water. --Tango (talk) 20:38, 24 May 2009 (UTC)[reply]
Saturn is mostly hydrogen so it is not surprising that its density is less than water. Jupiter is also mostly hydrogen but has a density greater than 1, but this is because of the great pressure in Jupiter. I expect that water at the same pressure would still have a greater density. As for floating, well no it would not. It is light enough to float, but any body of water large enough to float Saturn in would be larger than the planet. Saturn would lose its separate identity and be gravitationally melded into a new water+hydrogen planet, the combined body possibly being now large enough to ignite nuclear fusion and create a second sun in the solar system. In any case it would be spectacular, not at all like rubber ducks in the bath. SpinningSpark21:23, 24 May 2009 (UTC)[reply]
These kinds of comparisons are always very tortured, approximate and flawed. The problem with a gas giants is that they are kinda soft fuzzy things - and saying how big they are is a bit like asking how big a ball of cotton wool is. So you can come up with all sorts of density numbers depending on where you draw that line. Whether it would actually float is a really silly question - when you consider the gravitational pull of all of that water and of the planet itself - plus the fact that while the outer layers are really light - the core is pretty heavy and would obviously sink...but please - let's not go there! Suffice to say that most authorities say that it's mean density is less than that of water and quietly forget about floating. SteveBaker (talk) 21:52, 24 May 2009 (UTC)[reply]
Well, yes, obviously you can't actually float it in water. That would require the water and Saturn to be inside a gravitational field, which, in order for the whole thing to make sense, would have to be much greater than that generated by Saturn itself (just as when you float at apple at Halloween the apple is far smaller than the Earth). If you put Saturn in that gravitational field it would fall apart since it is only held together by its own gravity. "Would float" in this context just means "has a density less than that of water", it shouldn't be interpreted literally. --Tango (talk) 22:22, 24 May 2009 (UTC)[reply]
As an aside, I always wondered if that figure for density factored in the rings-- which I assume would be included in that bag with the rest of Saturn, even if the planet was in a rather misshapen form as the result of being in the massive gravitational field necessary for this thought experiment. 69.224.113.202 (talk) 04:24, 26 May 2009 (UTC)[reply]
For the past couple of years I've seen this insect right around springtime, It's fuzzy, fairly large, has a black head and black legs, and the fuzz is mostly a dull yellow with a black stripe running width-wise through the center of his back.
No, a bumblebee does not "walk around" before it grows wings :) . Bumblebees have a complete metamorphosis, so their larvae look nothing like the familiar adult (winged) stage. Now, there are distant relatives of bumblebees called "velvet ants" (Mutillidae). Mutillidae females really do resemble wingless bees, or big fuzzy ants, in their adult stage; males, OTOH, have wings. Is that what you've seen? --Dr Dima (talk) 00:44, 25 May 2009 (UTC)[reply]
Jet fighters sometimes practice following the terrain at an altitude of just a few feet, called 'hedge hopping'. I'm wondering what would happen if such a jet misjudged things and found itself sliding along on its belly on a flat area of wet grass, like a sledge. If it had no significant damage, would it be able to get into the air again?. That suggests another question - why do aircraft have their wheels on poles? 78.146.52.86 (talk) 23:19, 24 May 2009 (UTC)[reply]
To answer your second question first, airplane wheels are setup to hold the airplane some distance (at least a couple feet) from the ground to keep the engines as far as possible from the ground. Propeller planes obviously need this distance to keep from smashing up their propellers. Jets also need this distance to avoid sucking in debris from the ground.
For your first question, you might check out Belly landing. Most planes would not be able to recover from even the softest belly landings under their own power. I'm not sure if a fighter plane could do it, they're supposed to be more rugged and definitely have very powerful engines. I doubt the pilot would attempt it, he would have no way of knowing how bad the damage was. APL (talk) 01:39, 25 May 2009 (UTC)[reply]
You've got to read it carefully - the wings didn't scrape along the ground as the OP is asking - the undercarriage support apparatus evidently worked like skids - protecting the underside of the wings from damage. Still - a pretty amazing happening! SteveBaker (talk) 01:43, 26 May 2009 (UTC)[reply]
What about an aircraft where the wings and underneath of the body formed a flat surface - can a wing lift if it has no air underneath it, but is just sliding along a flat surface? 78.146.108.137 (talk) 13:35, 25 May 2009 (UTC)[reply]
Well, when the wings get within about half their length of the ground, you get a build-up of pressure under the wing (it's called "ground-effect") that actually increases the amount of lift - but if the wings actually hit the ground, there is so much friction that the plane's speed would rapidly drop to the point where flight is impossible...and the damage that's inevitable means it's going nowhere afterwards. SteveBaker (talk) 13:46, 25 May 2009 (UTC)[reply]
(EC) It's called 'nap-of-the-earth' (NOE) flight. In peacetime, they are limited to something like 500 feet above the terrain - but in wartime, they can go much lower - 50 to 200 feet depending on the nature of the terrain and the aircraft type. Most fighters that do this have terrain-following radar - the pilot hands control of the height of the plane over to the computer because human reactions simply aren't good enough to do this at hundreds of miles per hour (and because you often want to do it at night!). Some aircraft avoid using active radar by having accurate digital maps of the terrain instead (I know the Royal Dutch Airforce F16's do this because I worked on that subsystem in a flight simulator we built for them). As for 'belly landings' - if the ground is very smooth - with no large rocks - trees, etc - then it's possible to do a controlled 'wheels-up' landing and not die in the process - but the plane is going to be a write-off. Most fighter pilots would rather eject. SteveBaker (talk) 13:44, 25 May 2009 (UTC)[reply]
May 25
Casino Royal Poisoning Scene
In Casino Royal, 007 is poisoned by digitalis and develops V-TACH. That would not occur, as digitalis SLOWS the heart rate. Why don't the movie producers take a few minutes to verify the medical scenes in their movies?
P.S. the poison was probably modeled off atropine, as victims of atropine poisoning exhibit the same symptoms as in the movie.
Interesting. Our page on ventricular tachycardia in popular culture does assert that this was a mistake in the movie. However, that statement is incorrect as far as I know, so I checked the source and found it much less reliable than our usual standard. Here is a reliable source, and here is another, to show that digitalis at high levels can cause ventricular tachycardia. So, I will correct our page. --Scray (talk) 02:05, 25 May 2009 (UTC)[reply]
A movie where the hero saves the world with a lucky draw to an inside straight is probably not one with a whole lot of reality checks. -- Tcncv (talk) 06:39, 25 May 2009 (UTC)[reply]
No, see, Bond was so skilled that he got great cards! Ghh. That whole poker thing was the low point of an otherwise fine movie. Could you perhaps explain this "tell" thing one more time? It's such a complex concept! -- Captain Disdain (talk) 11:53, 25 May 2009 (UTC)[reply]
Are you asking whether someone can get an STD without having sex? The answer is yes—some are spread through alternative means (e.g. HIV in blood transfusions) that may or may not be very likely, but can occur. Are you asking if being celibate by itself will give you diseases? No. --98.217.14.211 (talk) 00:33, 25 May 2009 (UTC)[reply]
I have read (I can't remember where) that because males do not stop making sperm, that a persons testicles could become overful causing a very painful, but if treated harmless, disease.DrewSmithWhat I've done04:27, 25 May 2009 (UTC)[reply]
That's just ridiculous. The idea that all of the sperm just stay alive indefinitely and keep swimming around in the testicles is silly to begin with; no other cells in our body manage to keep from dying, so why would sperm be exempt from this? The body will reabsorb any excess semen. It's not a problem. -- Captain Disdain (talk) 08:56, 25 May 2009 (UTC)[reply]
This is persistent myth, e.g. for the cause of nocturnal emissions. I'm not going to boldly assert that people who never ejaculate have no long-term health differences from those who do so regularly; for all I know it may affect hormone production, with consequent auxiliary effects. But I may assert that there have been no serious experiments one way or the other. Dcoetzee06:54, 26 May 2009 (UTC)[reply]
But that does not imply that not having regular ejaculations causes prostate cancer. Sperm that is not ejaculated is reabsorbed into the body. The idea of huge testicles indicating complete celibacy is a nice idea but untrue. There are cases of enlarged testicles [19](work safe) but the causes are well documented. 86.4.190.83 (talk) 07:36, 25 May 2009 (UTC)[reply]
Nuns and other women who never give birth are more prone to breast cancer, per [20]. It seems to be the giving birth rather than the sexual intercourse that makes the difference. This was documented back in 1713 and confirmed since. Edison (talk) 18:36, 26 May 2009 (UTC)[reply]
Strange aircraft wing
I've recently seem some very strange aircraft, and this article (http://englishrussia.com/?p=2331) says it has huge advantages compared to more classical designs. Obviously, it should have it's flaws, because else nearly every aircraft would be designed lika that. Does anyone have any ideas about this? Besides, it's strange that it has no article here, as Elliptical wing means something completely different. --131.188.3.21 (talk) 09:57, 25 May 2009 (UTC)[reply]
My guess is that this would behave much like a biplane and have the same advantages and disadvatages. Aircraft were originally built as biplanes mainly for structural reasons - a single canvas wing is very difficult to tension - but once aluminium started to be used strong monoplane wings could be built. A biplane has greater lift than a similar sized monoplane but it is not twice as much because the vortex of the two wings tend to cancel in the space in-between the wings. Monoplanes are therefore more efficient in terms of lift per unit area of wing. This elliptical design gets a good separation between the top and bottom aerofoil surfaces so the negative effects may be somewhat lessened. Like a biplane, it is likely to have good manoeuvarability and short takeoff and landing characteristics, but I have not been invited to fly one, so as I say, I am only guessing. SpinningSpark10:55, 25 May 2009 (UTC)[reply]
I have no idea whether that's real or not, but this being the internet, the picture could simply be fake. I suspect it is; the design seems pretty senseless, and I can't find a single YouTube video featuring such a plane, at least not with the words "elliptical wing". In fact, even fairly rigorous Googling only reveals those very same pictures all over the net...
In any case, even if it was real, your logic is a little iffy: saying that the design must be faulty, because otherwise every aircraft would be designed like that presupposes that people instantly arrive to the best solution. I mean, why didn't the Wright brothers build a stable aircraft right from the beginning instead of the flawed contraption they had? Well... you gotta start somewhere, and if you hit upon a design that works (not that the Wright brothers really did, but anyway), it can remain essentially unchanged for a long time simply because it's good enough. (The M1911 pistol is a great example of this: it's still being used by some armed forces, even though the basic design is over a hundred years old. There are far more advanced sidearms out there, but it's a popular classic.) It can take a long time for a genuine innovation to arrive and really make an impact. -- Captain Disdain (talk) 10:57, 25 May 2009 (UTC)[reply]
Oh, I think the photos are real: at least the ones at the top of the page, the bottom two are obvious fakes. What I don't believe is that it has ever got off the ground, and you would be quite foolhardy to take off in something you had bolted together in your back yard and has a side panel that looks like it's been in a car crash. There are no (unfaked) pictures of it actually in the air, although the engine and prop are clearly working. SpinningSpark17:30, 25 May 2009 (UTC)[reply]
For a small aircraft that needs high manouverability, I could imagine this thing being interesting. However, it loses the benefits of 'dihedral' (which imparts inherent stability) - it will be hard to fly (although computerized fly by wire controls could fix that). Who knows what construction difficulties and structural strength this design might impart? The claim for high efficiency comes about because with conventional wings the higher pressure air under the wing tends to 'leak' around the wing-tips into the low pressure air that's on top of the wing. That wastes lift and causes tip-vortices which increase drag. This wing has no tips - but the high pressures under the lower section of the ellipse can still move around to the low pressure over the top section - but that's a much larger vortex. But then the high pressure under the top section will push around into the low pressure over the bottom section - creating a counter-vortex. It's really hard to predict the results of these two counter-acting effects. The 747-400 (see picture at right) has little wing-tip fins that attempt to 'dam' that air. I dunno - it's hard to imagine someone like NASA wouldn't already have tried this if it had widespread benefits...they've tried some pretty weird designs in the past so it's not like there is a lack of effort in innovating wing shapes. SteveBaker (talk) 13:26, 25 May 2009 (UTC)[reply]
Although that particular aircraft has no dihedral, there is no essential reason that wings in that format could not be given dihedral so I don't think that dihedral is an essential drawback to the ellipse-wing. Besides which, stability is not always a good thing. Stability and manoeuvarability are exchangeable and are a compromise on all aircraft; for military fighter aircraft manoeuvarability has overriding importance and for this reason, amongst others, stability is often low. Likewise aerobatic aircraft want manoeuvarability over stability. The Cessna 152, for instance, is so stable that you can put it into a stall, let it start dropping like a stone and then let get of all the controls. The aircraft is so stable that it will pick up speed, start flying again and then level out into straight and level flight all by itself (warning: don't try this at home) as if it had an autopilot. On the other hand, it is no fun to fly, equivalent to exchanging a sports car for a minibus. Likewise with the winglets, there is no essential reason they (or some other wingtip device) could not be fitted to an ellipse-wing, although I am unconvinced that there is a need for them. The smooth shape of the ellipse-wing at the "tip" will encourage laminar flow, removing one of the reasons for them. SpinningSpark15:50, 25 May 2009 (UTC)[reply]
Occasionally there is a reference to "Steam II" as if there are two phases of steam. However even this rather complicated phase diagram of water, which identifies a grand total of eleven different phases of ice, does not mention steam II. Would it be steam in the supercritical region? SpinningSpark11:14, 25 May 2009 (UTC)[reply]
The title of the article that you linked doesn't say quite what it seems to, it's the second part of a two-part article, this is the first [22]. Mikenorton (talk) 13:13, 25 May 2009 (UTC)[reply]
I have asked this question three times before. Each time, there is no answer because the topic is quickly derailed by discussions of artificially colored hair. Therefore, I want to make this clear: I am not in any way interested in any discussion of artificially colored hair.
When hair turns gray, I have always seen a hair that is gray from root to end. My hair is dark brown and my gray hair is actually white. I have no hairs that are brown on the end and white at the root. This makes me wonder... Do hairs turn from natural color to gray? If so, how does the entire hair change color? Do the gray hairs come from a different follicle than the natural colored hair? I'm just wondering why I never see a hair that is brown on one end and white on the other. -- kainaw™15:32, 25 May 2009 (UTC)[reply]
From personal experience, I have come across hairs that are coloured near the end and grey/white at the root, but very few. In those hairs there is a short (~1 cm) transition zone of decreased pigmentation rather than an abrupt loss of pigmentation. I suspect the reason that they are hard to find is that there are so many hairs on your head. Those that are in the midst of losing their pigmentation are hidden among the other hairs. They only become noticeable when you get your hair cut, and cut hairs likely would have removed the coloured bit. -- Flyguy649talk15:52, 25 May 2009 (UTC)[reply]
I am in agreement with Flyguy649, with the additional note that white hairs are often thinner and more brittle than coloured hairs. It could be that the bi-coloured hairs are more likely to break off and be lost due to the tip being to heavy for the white base. Matt Deres (talk) 15:56, 25 May 2009 (UTC)[reply]
Each individual hair is produced by a single folicle. Each folicle loses its ability to produce color at a different age. So, hair produced by a folicle before the loss is colored, and after the loss the new hair is gray. Therefore, the timr it takes for particular hair to becoem completely gray is the time it takes to grow from root to tip, which in turn depends on the length of the hair. Most hairs are eithr all colored aro all gray because the time is relatively short in comparison to the time span over which all your folicles lose their coloring ability. -Arch dude (talk) 20:59, 25 May 2009 (UTC)[reply]
There was a recent article on sciencedaily.com about grey hair here. The gist is that hair goes white because our bodies naturally produce bleach, and as we age we are less able to remove that bleach. The article also says that hair goes white from the inside out. Quietmarc (talk) 22:03, 25 May 2009 (UTC)[reply]
Each hair follicle does not keep producing hair constantly. Instead, there is a cycle of growth, quiescence, hair loss, and then renewed growth. While I don't have anything to show this is the case, I imagine that the color loss may occur during the quiescent to renewed growth phases. In this way each individual hair shaft is either entirely colored or entirely gray. -- 128.104.112.37 (talk) 00:32, 26 May 2009 (UTC)[reply]
I believe 89.242.ip is referring to gorrilas, not guerillas. Often what happens is that individual hairs become white, and as the proportion of that increases, the mas of hair appears more "gray". ~AH1(TCU)01:14, 26 May 2009 (UTC)[reply]
It occurs to me that if you can't get a satisfactory answer from reliable sources, it would be a good idea to ask or look into the situation for a traditionalist/adherent Sikh, Rastafarian or someone else who never cuts their hair Nil Einne (talk) 22:00, 26 May 2009 (UTC)[reply]
Racism and science.
Why is racism a scientifically wrong belief? The article on racism doesn't explain it clearly enough.
Thanks in advance,
― Ann ( user | talk )15:49, 25 May 2009 (UTC)[reply]
Because there are no scientifically reliable methods of discriminating races from each other. The methods that can be used (such as using haplo-groups) often have little to do with the conventional races at all. Also, you would need to specify which brand of racism you want to talk about. Most racism has nothing to do with rational thinking in any case. Since science attempts to be rational, the two have little to say to one another. Matt Deres (talk) 16:03, 25 May 2009 (UTC)[reply]
(edit conflict) There is no scientific evidence that can't be explained by differences in culture. It also hasn't been proven that the cause is differences in culture rather than being of different intelligence, so it isn't so much scientifically wrong as just not scientific. If there is a difference, it's not that big, so anything more than mild racism is scientifically debunked. It should be noted that if there is a small difference in the intelligence of different races, that doesn't mean that it's in the direction a lot of people seem to think it is. Also, even if there was a difference, it couldn't easily be said which was better. For example, there is a clear difference in how men and women think, but there's no agreement as to who is more intelligent. — DanielLC16:10, 25 May 2009 (UTC)[reply]
It's also of note that any racial differences are probabilistic over the aggregate of a population. So what you're saying is, "in a given population (defined in some sort of useful way), the average IQ is X." But that doesn't tell you anything about individuals within the population, which is how racism is always practically expressed—you don't get the job not because you don't have the ability, but because you are a member of a population that on the aggregate has different abilities than others. You can illustrate how silly this is by doing the reverse (boosterism)—imagine being asked if someone is a good basketball player on the basis of their race alone. The idea is completely silly—any individual member of a race could be a good or bad basketball player, even if on the whole for a variety of reasons some races might on average produce better basketball players than others.
The definition of "race" is itself scientifically problematic—there are no "pure races" and never have been. The most rigorous scientific definitions are still very probabilistic—people who live in a given area have a certain higher percentage of having certain combinations of genes than people who come from other areas. In reality there is a graduate spectrum of relatedness among the human species.
Lastly, the question can never be is "racism" scientific—racism is a form of social judgment that sits on top of questions of racial difference. Are there racial differences? Obviously some (on average)—some of which are easy to measure (skin tone variations) some of which are hard (intelligence, which is hard to measure even under ideal circumstances). Whether one thinks that justifies discrimination is an entirely non-scientific question (it is a philosophical or political question). --140.247.241.193 (talk) 19:42, 25 May 2009 (UTC)[reply]
One of the problems is the meaning of the word itself. Scientifically, racism means the view that people from different origins have different characteristics besides their look. So, saying that someone from African descent and with dark skin tolerates a hot climate and sunburn better than a Caucasian, and the later tolerates cold and a lack of sunbathing better - which is obviously true - would still be considered racism? The problem with this is that the word "racism" means today just "something very evil" and nearly nothing else, and actually used to discredit some other party even if they didn't mean to discriminate people based only on "racial" descendence. I think this discussion would more likely fit the humanities desk, as the world racism has mostly propagandistic uses. Besides, with this current usage, no one even dares to study or write about racial differences, and writing "racism is scientifically wrong just because it's wrong" is a must, if you do not want to be labeled as someone very evil.
Of course, racism in it's current usage is wrong, as the behavioral differences seen in statistics are caused by cultural, educational or other social heritage, and not by biological makeup.
The interesting, and sad thing is, that forcefully denying the above mentioned behavioral differences (and calling everyone a racist who mentions them) actually leads to increase racism, rather than solve the problem. Of course, saying that these behavioral differences are cause by the genetic profile of that specific group is equally wrong. I prefer referring as racism only to this last example, and not how most politicians tend to use it. --131.188.3.20 (talk) 20:46, 25 May 2009 (UTC)[reply]
Racism is like claiming that within a species, there are breeds that are better at some activity than other breeds. Aren't all horses equally able to run a race or pull a plow? Aren't all dogs equally able to track, pull a sleigh or herd ruminants? Don't all pigeons have the same homing ability? Edison (talk) 00:47, 26 May 2009 (UTC)[reply]
Was the answer to those questions supposed to be no? A Chihuahua can't pull a sleigh nearly as well as a Great Dane. In any case, that's not very scientific. You have to actually check, you can't just say what it should be. — DanielLC05:11, 26 May 2009 (UTC)[reply]
Racism might be more like assuming that dogs of some particular color are more likely to bite you than others. But Temple Grandin, animal scientist, claims that the selective breeding which led to chickens which lay white eggs has left the hens more prone to stress. White lab rats have behavioral differences from wild rats of various fur colors. Minor physical or coloration differences between subgroups of an animal species may correlate to varying extents with behavioral differences. I have heard intelligent and well educated people assert that there simply cannot be any differences in intelligence, aptitudes or physical abilities between races, on the same principle that there should not be discrimination between different races. Edison (talk) 18:30, 26 May 2009 (UTC)[reply]
Yes, clearly there are the possibilities of differences on average between population groups, and anyone who disagrees with that on the face of it is probably doing so for primarily political reasons. But dogs are a very poor comparison—dog breeds are very carefully developed exercises in inbreeding over tens of thousands of generations with relatively small population sizes for specific characteristics that often are at the expense of others. There is nothing comparable in humans, and the differences between human races are really quite slight when compared to differences between dog breeds. (Temple Grandin is careful to point out that what she says about domesticated breeds does not apply to human races, if I recall.) --140.247.251.62 (talk) 18:49, 26 May 2009 (UTC)[reply]
There are two entirely separate things going on here. It is entirely scientific to say that there are races - and that they are different in many ways. We know (for example) that people of African descent are more prone to sickle-cell anaemia...it's a fact - there is no point in denying it. There are LOTS of differences between people of different races. It's scientifically valid (but not entirely politically correct) investigate those differences.
HOWEVER, what is entirely UN-scientific is to discriminate between individuals on the basis of race. The variations between individuals of one race are generally far greater than the differences between races - so to pick one individual and to treat him/her differently because of the color of his/her skin is entirely illogical and unscientific.
Actually, I think that is inaccurate. First, of course, we are all "People of African descent". But secondly, people with a a long ancestry from malaria-prone areas are more prone to sickle-cell anemia. Many Africans are, but then, many are not. By lumping them all together, you are artificially creating a "race" that, quite by accident, shares this property, while the actual cause only applies to a sub-population. "Races" are social constructs with fairly limited predictive power about the non-obvious criteria - in Brazil, for example, your income and life style influence your perceived skin colour... --Stephan Schulz (talk) 07:26, 26 May 2009 (UTC)[reply]
I'm surprised this hasn't already come up but I think this is highly relevant to the discussion race and genetics. A key part IMHO "The 0.1% genetic difference that differentiates any two random humans is still the subject of much debate. The discovery that only 8% of this difference separates the major races led some scientists to proclaim that race is biologically meaningless. They argue that since genetic distance increases in a continuous manner any threshold or definitions would be arbitrary. Any two neighboring villages or towns will show some genetic differentiation from each other and thus could be defined as a race. Thus any attempt to classify races would be imposing an artificial discontinuity on what is otherwise a naturally occurring continuous phenomenon.". While not everyone agrees "However, other scientists disagree by claiming that the assertion that race is biologically meaningless is politically motivated and that genetic differences are significant. Neil Risch states that numerous studies over past decades have documented biological differences among the races with regard to susceptibility and natural history of a chronic disease. Effectively Neil Risch is attempting to redefine "race" for human populations to represent that small proportion of variation that is known to vary between continental populations." I don't think it is fair, or logical to dismiss all scientists who argue that race is biologically meaningless as just letting their political beliefs get in the way. I would say that both sides are likely influenced by their political beliefs but regardless, it doesn't mean there aren't valid scientific reasons to argue both ways about whether race is a meangingful scientific concept. This doesn't mean people dispute that certain genes are more strongly associated with certain groups if you choose to define such a group in some way Nil Einne (talk) 21:53, 26 May 2009 (UTC)[reply]
This is a pretty complicated question. One might reasonably say that, given no other evidence about two people other than their races, you may prefer one over another for a certain job or task, since race conveys limited statistical information about a person. Irrational decisions arise in situations where the statistical information supplied by race is given disproportionate emphasis over the direct information supplied by examining the individual; or over information about the individual that could be easily obtained. Irrational decisions also arise in cases where the statistical information supposed to arise from race has no basis in experiment, or those experiments are procedurally faulty (as in the case of most scientific racism). To give a ludicrous example, young males tend to break bones more often young females; therefore, given a random young male, you'd be more likely to conclude that their leg is broken than when given a random young female. On the other hand, a much better way of determining this is to actually examine their leg. Dcoetzee06:39, 26 May 2009 (UTC)[reply]
casimir effect pressure anomalies
Hello
Alot of talk about zero point or vacuum energy has been passed around lately and its been used to explain everything from telepathy to gravity. Loads of it is complete hocum some is not. I was wondering if you guys could help clear something up for me. I recently read an article that proposes that changes in the state of this vacuum energy either on its own or to cause upsets in air pressure etc could mave objects. Is this possible if not yet proven and what is the view of the general scientific community on this idea. I read it was considered as a means for space propulsion. Note I am not talking about psychic connections, healing, living universe etc, just wether the changes in the vacuum could conceivably move objects.
Do you have a link to the article? Generally speaking it's deeply unclear what ought to count as "vacuum" in modern physics. If there are vacuum disturbances that can exert forces on objects then we're likely to decide to give them some other name than "vacuum", making the vacuum inert by definition. That's pretty much what the known particles and forces are, fluctuations of the vacuum that we've decided to call by different names. Note this includes the Casimir force, which is no more or less an effect of vacuum fluctuations than anything else. -- BenRG (talk) 19:02, 25 May 2009 (UTC)[reply]
The article was on the new scientist and suggested a vacuum energy sail, ill try find a link. Think it suggested a polerization of the vacuum so one side vibrates more and thus exerts more pressure on one side, thus moving it. Like the casimir effect except instead of pushing the two mirrors together only pushing one side.
I haven't had a chance to dig up this particular New Scientist article yet, but I would urge its readers to be particularly cautious when new inventions which (apparently) violate conservation of momentum laws appear. The most recent major screwup – of which I am aware, at least – was in 2006, when they published a very credulous cover story on the EmDrive. TenOfAllTrades(talk) 12:52, 26 May 2009 (UTC)[reply]
Thanks for the link. This doesn't look like reactionless propulsion, it looks like a very roundabout description of a photon drive, i.e. a rocket that emits light for propulsion. In other words, it's a Rube Goldberg flashlight. The whole vacuum-fluctuation angle doesn't make it a better source of photons. For that matter I could probably figure out a way of attributing the operation of an ordinary battery-powered flashlight to vacuum fluctuations. That New Scientist reported on this doesn't mean anything. I think it was once a good physics magazine, but it's pretty cringeworthy these days. They seem to have no knowledgeable physicists on staff and a lot of their articles are basically press releases for kooks. This looks like it's in that category. -- BenRG (talk) 21:20, 26 May 2009 (UTC)[reply]
the color of protons/nutrons
There are so many different elements and many of them are different colors. Though they are all made of the same things protons nutrons and electrons? How can somthing made from the same things have so many different colors? how can a material be a different collor just because it has a dirrerent amount of nutrons electonrs or protons? So if we could look at a seperat nutron of sepret proton what color would it be?
--76.236.178.7 (talk) 16:27, 25 May 2009 (UTC)[reply]
Your understanding of colour seems to be wrong. I'm not an expert in the area, but the A-level chemistry explanation is that photons from a light source (e.g. the sun) are absorbed by the electrons of an object, which causes excitation of the electrons, so the jump up to a higher "energy state". When the electron falls back to its ground state, an electromagnetic wave is emitted. In chemicals that we see as coloured, this wave is in the "visible light" area of the EM spectrum (between ultraviolet and infrared). Protons and neutrons individually won't have a colour, I believe. --Mark PEA (talk) 16:55, 25 May 2009 (UTC)[reply]
...so many different elements..., actually, most elements are metals, and most of those are some shade of grey/white (with the exception of gold and copper) not many different colours. Or did you mean chemicals rather than element? SpinningSpark17:10, 25 May 2009 (UTC)[reply]
Mark's explanation is a pretty good one - in the case of 'diffuse' reflection (which gives objects their color) - the light is absorbed - kicking an electron up to a new energy level - and re-radiated at a different frequency when the electron gives up that energy. But shiney surfaces use a much more complicated mechanism - requiring 'quantum electrodynamics' to explain how they reflect light (typically without changing it's color). It's a complicated matter - and it's WAY more complicated when you stray from pure elements to chemical compounds where the interaction of lots of different atoms causes the phenomenon of color.
Things as small as electrons, neutrons and protons are far too small to reflect light. A 'wave' of visible light is between about 400 and 700 nanometers - an atom of (say) carbon is around 70 picometers - that's around 10,000 times smaller than the wavelength of light. That's why you can't see individual atoms in a normal microscope. Protons, neutrons and electrons don't have a 'size' at all - they are just infinitely small dots. So when you get into the physics of how light is reflected or refracted, absorbed or radiated, it all gets very complicated. It's wrong to think of things as small as atoms as having a 'color'. SteveBaker (talk) 01:21, 26 May 2009 (UTC)[reply]
Of course, not to confuse the living shit out of the OP, but while protons, neutrons, and electrons do not have a color, quarks do. Well, not really, but they have a property which is not a color, but we call"color" just to confuse the living shit out of people. See Quantum chromodynamics for more living-shit-level confusion of quark color... --Jayron32.talk.contribs00:54, 27 May 2009 (UTC)[reply]
They are sometimes found in caves. Are there caves in Missouri with snakes which have over generations lost the use of their eyes? Edison (talk) 00:43, 26 May 2009 (UTC)[reply]
The question is not so much the number of eyes but the way the brain puts the information together. I think it's going to be hard to make sense of that through human understandings of such things (one big coherent image is sort of what we are used to—imagining it as eight different images is probably not actually how the spider sees it and says more about our understanding of vision than theirs). --140.247.241.193 (talk) 19:58, 25 May 2009 (UTC)[reply]
Yeah - it's really not possible to know. For example - human eyes have a blind spot in each eye - literally, a place in the middle of the retina where you are totally blind. Are you aware of this spot? No! In fact you have to go to considerable trickery to fool yourself into actually noticing it! Are you aware of the continuous vibration of the eyeball that's used to improve spatial resolution...do you notice that? No! Are you aware of not being completely unable to see color in your peripheral vision? Nope? I thought not! Our brains are very good indeed at hiding the deficiencies of the system from our conscious minds. I assume the spider's brain is doing something similar - but perhaps it isn't - we really have no way to know from simply looking at the geometry of the spiders' ocular geometry. Hence we have no clue how the world looks to it. SteveBaker (talk) 01:07, 26 May 2009 (UTC)[reply]
Is it even possible for the human mind to comprehend what a 3D view constructed from eight separate images (making a huge assumption here in suggesting that this is how a spider's visual system actually works) would look like? I guess that a computer might be able to knock one out (in the same way as you can get them to draw multidimensional shapes that make your head hurt if you try to visualise them as meatspace objects)...
(1) On the poor color sensitivity in human peripheral vision - it is true, and well known. AFAIR, it is related both to the low number of cone receptors in the peripheral retina and to how the ganglion cells in the peripheral retina are "wired". Actually, it is also very easy to test. Pick up one color pencil from a set, without looking, and hold it in the outstretched hand at eye level, starting as far back as your hand would go. Now move it very slowly forward. At some stage you will be able to see the pencil out of the corner of your eye. Now ask yourself what color it is. You'll be surprized... (2) On the spider vision - we can not possibly imagine what spider "sees" as it possesses a brain architecture very different from ours. However, if we imagine that all the processing that occurs in the retina and beyond is similar in spider and in human (which is not true), then having additional eyes is not much different from having a rear view mirror in a car, or having several graphic application windows opened at once on your computer monitor. My point is, simply having more eyes is not the main difference between the spider and a human :). Spider visual system is truly unique and truly exquisite, especially in Salticidae, Lycosidae, and some other active hunters. Unfortunately, it is far less well studied than rodent, cat, or primate visual system. Still, googling for "spider vision" returns plenty of fascinating stuff. --Dr Dima (talk) 07:17, 26 May 2009 (UTC)[reply]
"You can lead a cow up a flight of stairs but not down a flight of stairs - because of the design of their legs..."
There is anecdotal evidence (and even videos on youtube) that claim it to be false. There is even a popular book that uses this very question as a title. Most of the people who say that cows can walk down stairs say that the animal has to either be led or otherwise enthused to do it and will not approach a downward set of stairs of its own volition. The same can be said of other animals with similar hind legs such as dogs, horses, donkeys, goats and sheep - all need encouragement or leading but will eventually do it. Nanonic (talk) 17:22, 25 May 2009 (UTC)[reply]
Try going up a flight of stairs on all fours, and you'll find it easy. Try going down a flight of stairs on all fours, and you'll be hesitant at the very least. It can be done, but you have to adjust the way you would 'normally' crawl on all fours. Try it and see. --KageTora - (영호 (影虎)) (talk) 21:06, 25 May 2009 (UTC)[reply]
KageTora, That experiment is faulty. Cow knees bend the opposite way from our knees and elbows. Many four-legged creatures are like that, including dogs and cats. APL (talk) 01:00, 26 May 2009 (UTC)[reply]
I believe that those are not knees, but rather the animal's ankles. The knees are usually located way up the thigh. Look at the flamingo, for example, where the ankles are actually midway between the end of the legs and the torso. ~AH1(TCU)01:03, 26 May 2009 (UTC)[reply]
Fair enough. My point was only that the creature's legs were different than ours, with potentially different capabilities. APL (talk) 01:27, 26 May 2009 (UTC)[reply]
I was actually aware of the difference, but without breaking the OP's legs and arms, there is no practical way to remedy it. In some scientific experiments, you just have to make do with the tools you've got. --KageTora - (영호 (影虎)) (talk) 06:23, 26 May 2009 (UTC)[reply]
The truth is that it's not much fun for cows/horses, but most animals can go down stairs with a bit of coaxing. They much prefer ramps and elevators, however. Some animals, such as mountain goats, are probably even better suited to going down stairs than humans. Dcoetzee06:28, 26 May 2009 (UTC)[reply]
Distance That Whale Song Is Audible
According to our article on Whale song, it says that research by Cornell University showed that whale noises travelled 3,000,000 km. Now, how many times around the planet would that be? Considering it would be almost ten times the distance to the moon, I find this hard to believe (I am not saying the sound would get to the moon, for obvious reasons, I am saying the distance cited is ludicrous). Should this be changed? --KageTora - (영호 (影虎)) (talk) 20:52, 25 May 2009 (UTC)[reply]
You're right, it is clearly nonsense. It was vandalism (here), I've reverted it. It should be 3,000km (at least, that's what it was before that edit, I don't have the source to check it is correct). --Tango (talk) 21:06, 25 May 2009 (UTC)[reply]
scientific method and evolution
In reading the article on the scientific method the following is noted:
"Scientific method refers to bodies of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning.[1] A scientific method consists of the collection of data through observation and experimentation, and the formulation and testing of hypotheses.[2]"
So, my question is: to what extent does the science of the Theory of Evolution adhere to the scientific method? If it does not, then in what way is the exploration/investigation of the Theory of Evolution "scientifically" utilized or based? Are there other legitimate "scientific methods" other than the traditional one? —Preceding unsigned comment added by 69.77.185.91 (talk) 21:04, 25 May 2009 (UTC)[reply]
The scientific method is rather difficult to define. It is applied very differently in different fields. Evolution is certainly scientific, though. It is a theory supported by empirical evidence (from the fossil record, analysis of DNA, etc.). Evolutionary biologists hypothesise about how a certain animal or group of animals evolved and then they go out and find more fossils and see if they match the intermediary stages their hypothesis predicts, refine their hypothesis and then go and find some more fossils and repeat ad infinitum. --Tango (talk) 21:11, 25 May 2009 (UTC)[reply]
The Scientific method is the practical side of the philosophy of science. It is all about formulating and testing hypotheses. The term "Theory" is used of a hypothesis that is of major importance and that has whthstood many tests. (The term has other meansing, but please do not confuse them.) To be useful, a hypothesis must be "falsifiable." That is, a scientist must be able to us the hypothesis to predict the (initially unknow) outcome of an observation or an experiment. If the outcome is not as predicted by the hypothesis (theory,) then the hypothesis (theory) has been shown to be false. The theory of Evolution has been tested in this manner many, many times,and has not been falsified.This is in stark contrast ot (for example) the "theory" tha God created teh earth in seven days: this is not falsifiable, because this theory postulates an omnipotent God, and an omnipotent God can produce anything that we can obaseve. sucn a "theory" has no predictive power, and is therefore not within the purview of science. -Arch dude (talk) 00:57, 26 May 2009 (UTC)[reply]
There is no great mystery about "The Scientific Method" - you have an idea (a 'hypothesis'), you figure out an experiment that would test that hypothesis. If the experiment comes out right - you publish your hypothesis and your experimental technique and the results you got. Other people try the same experiment - and if they agree that you're right - then you have a theory...otherwise you start again with a new hypothesis. Evolution was a hypothesis since the time of the ancient Greeks - but evidence had not been methodically gathered...so it remained a hypothesis. Darwin found his finches and other unusual groupings of animals and that constitutes experimental evidence. Since then, we have countless cases where we have shown either the results of evolution - or in the case of species with very short generations, we've even been able to show it in the lab. The consequences of evolution show up in the need to continually come up with new antibiotics as bacteria evolve immunity to the ones we've been using successfully for years. We can even show evolution in humans by looking at how junk DNA has accumulated in separated populations of humans. Things like adult lactose tolerance can be shown to have evolved in humans over just the last 5000 years or so. So there is plenty of experimental evidence - gathered independantly by people from widely separated disciplines. Evolution frequently stands up to contrary hypothesis - the commonly stated case of the bacterial flagellum, for example...but these challenges have always been successfully and comprehensively deflected. That makes evolution one of the most solidly based scientific laws we have. SteveBaker (talk) 00:45, 26 May 2009 (UTC)[reply]
Well, its not as law, which is to say that it is not a consise description of a single phenomenon, but rather a theory, which is a comprehensive explanitory framework. The terms "law" and "theory" are frequently misunderstood outside of people who study the philosophy of science.
But back to the OP. The most basic understanding of the scientific method is the basic framework of "hypothesis - observation - conclusion" cycle. The basic idea is that an idea is proposed; observations are made which could either confirm or refute the idea, and then determinations are made as to veracity of the original hypothesis. Its not more complicated than that. Its almost a self-evident method of understanding the world around us; indeed though the basics of it were codified by Roger Bacon and Francis Bacon (no relation to each other) and others over the bast few centuries, the basic process has been carried out since people first started getting ideas and testing them out. Even something as simple as "I think my arm is broken. It hurts when I move it this way. Therefore it is probably broken" is basicly using the scientific method.
The deal with evolution is that it is pretty solidly backed by huge amounts of data; and its not just that people have specifically sought out and shown that evolution works; its that we operate on a day-to-day basis assuming that it does, and absolutly nothing that happens refutes that it does. As Steve has mentioned, concepts such as antibiotic resistance or even such basic ideas as dog breeding show that we work within evolution all the time, and it always works. People seeking to refute evolution mistakenly believe that the entire system is built on a few easily refuted ideas, and that if they somehow could come up with an as-to-yet unanswered question, it would come down like a house of cards. The problem with that is a) not every question which could be answered has even been asked yet and b) the occasional unanswered question that does come up is rather quickly answered once anyone bothers to take the time to answer it. The classic case of the flagellum was basically worked out a decade ago, and it started because some anti-evolution types said "Hey, look, evolution can't explain the flagellum! So it must all be wrong". Then someone said... "Hmmph. never noticed that" then they quickly showed how evolution could neatly explain the flaggelum, which sent the anti-evolution types seeking out some other esoteric idea which could not be explained, which would then be quickly explained. The same cycle continues, and only adds to the data that fully supports the theory. It's not just that its a proven theory, in that people have worked out the experiments to specifically back it up sometime in the past; its that its a working theory which we use all the time, and continues to work well. Are the minutae of evolution being tweaked all the time? Yes they are. There are always things which are being changed regarding our understanding of evolution; things we assumed to be true turn out to be false, but these are mostly the small details (for one example, read this month's Scientific American article on synonymous DNA mutations). The basic concept is perfectly sound and works perfectly well as a theory. --Jayron32.talk.contribs04:13, 26 May 2009 (UTC)[reply]
Essays about scientific method seem to assume that there is a ready supply of new hypotheses and therefore that the work of scientists is to test which of these hypotheses wins over the others. That hardly considers real situations where only one hypothesis is proposed and open to analysis. While that is the case, the scientist cannot conclude that the single hypothesis is relatively "good" or "bad" since there is no basis for comparison. (S)he finds that it must be (for now) the overiding theory. However there can be scope for alternative hypotheses within the overiding theory, and these are subject to the scientific method. Cuddlyable3 (talk) 09:38, 26 May 2009 (UTC)[reply]
We have done quite a lot of science now, so we have a pretty good idea of how most things work. That means most new hypotheses are just refinements of existing ones. Major paradigm shifts are few and far between. --Tango (talk) 11:04, 26 May 2009 (UTC)[reply]
Steve, you've been spending too much time with creationists! A law is not a theory that has been proven to a high level of certainty. A law is a simple result, often a simple formula (Ohm's law, Kepler's laws, etc.), that is generally derived empirically. A theory is a framework that attempts to explain why that formula holds and predicts new laws that can be tested. Evolution is a theory, not a law, and will always be a theory. --Tango (talk) 11:04, 26 May 2009 (UTC)[reply]
Of course, it was Stephen J. Gould himself that argued that evolution was both a law and a theory—that the change of species was clearly observable (a law), whereas natural selection is the theory by which it happened (theory). --140.247.251.62 (talk) 17:13, 26 May 2009 (UTC)[reply]
I would disagree. Observing that organisms change gradually over many millennia doesn't allow you to make predictions (at least, not very precise ones). A law needs to have predictive power. Natural selection allows you to make predictions. You know the gradual changes need to have some reproductive benefit so you can work out, for example, what order certain changes are likely to happen in so you can predict what the missing link in the particular evoluntionary sequence would look like (and then you can go fossil hunting and try and test that prediction). --Tango (talk) 17:19, 26 May 2009 (UTC)[reply]
[citation needed] for the claim that Stephen J. Gould has called evolution both a law and a theory. A quick Google on my part doesn't show any evidence of Stephen J. Gould having said that. He has said evolution is both a fact and a theory [24], as does several of our articles (e.g. evolution as theory and fact). This is quite a different thing, because as we have established in this discussion and elsewhere, a 'law' is a poorly defined word in science and is usually avoided in most modern scientific contexts except where it can't be for historic reasons. A good example is Newton's law of universal gravitation which although still called a law, is arguably not entirely correct. The fact of gravitation or evolution though are there even if the theories of them are not entirely correct. And calling them the fact, conveys entirely IMHO the appropriate sense in the modern world without the confusion of calling them by such a poorly defined and poorly used word in science as law. Indeed I've never heard someone call anything in biology a law, it's thankfully IMHO something that never caught on Nil Einne (talk) 21:21, 26 May 2009 (UTC)[reply]
Lest we focus too much on the "test a hypothesis" part of science, we should remember that an important part of the "scientific method" is that someone first needs to make an initial observation, and then have enough curiosity to ask "why?" or "how?". Only then can she/he come up with a plausible explanation (hypothesis) and test it using whatever techniques are available and applicable to the question. Much of what we do in science is actually not "hypothesis driven" (see human genome project, for example) but this doesn't mean that it isn't science just because it doesn't directly test a hypothesis. Rather, it is the new "observation" that now generates new hypotheses or enables other hypotheses to be examined in a different light. --- Medical geneticist (talk) 16:49, 26 May 2009 (UTC)[reply]
Allow me to clarify that - an individual research project can start at any point. Science as a whole has to start with an observation. Forming a hypothesis with no reason behind it is a good way to waste time, but that reason can come from somebody else's work. --Tango (talk) 17:22, 26 May 2009 (UTC)[reply]
If science required observations before it could create hypotheses, much of our current canon of theoretical physics would never have gotten anywhere. (Einstein didn't observe anything when he was re-thinking space and time. Both SR and GR were undertaken primarily for internal theoretical reasons and not in response to specific experiments or observational problems—though in the case of SR it's worth noting there is some historical dispute over whether he paid any attention to experimental data or not. There are many other theories that have started out as purely "what-if?" questions that may or may not be compelling/likely enough to go through actual testing on.) Most scientists and philosophers agree that it really, really, really doesn't matter HOW someone comes to START thinking about something in science. The question is whether you can then confirm it, falsify it, etc. (In the Einstein example, what mattered not is that he was thinking about space and time disconnected from experiment, but that his theories did have testable predictions that could then later be explored.) Trying to put a "method" on to the investigation side of things does not work nor does it matter — what matters is that the follow-up is done correctly. --140.247.251.62 (talk) 18:38, 26 May 2009 (UTC)[reply]
If you trace it back far enough, you get to observations. The "internal theoretical reasons" you mention were issues with previous theories, which had been developed from observations. So someone made an observation, then someone made a theory, Einstein then looked at that theory and found some problems (even though they didn't, at the time, result in testable false predictions) and fixed them. The process started with observations. --Tango (talk) 20:02, 26 May 2009 (UTC)[reply]
Oh jeez - Karl Popper! He's a philosopher...and a philosopher who works in a school of Economics at that. <sigh> Philosophers are a waste of quarks. SteveBaker (talk) 19:57, 26 May 2009 (UTC)[reply]
Predicting Rainstorms
In London today we had a quick rainstorm. I was speaking to someone on the bus who was telling me they always know that it's going to thunder because insects burrow up from beneath the paving slabs on the pavement. I've noticed this is generally true, and when I got off the bus, there were piles of sand all over the place and ants scurrying round, with a lot of flying insects about. Why is this? Can they sense air pressure? Are they worried about being drowned? Is this just anecdotal evidence or is there a scientific basis for this phenomenon? -russ (talk) 21:19, 25 May 2009 (UTC)[reply]
With regard to thunder, there is a possibility that the insects are detecting voltage changes in the earth, which are an indication that lightning is about to strike? Or perhaps they are truly psychic, not unlike Tyrone Slothrop, and are able to predict where the lighting will strike? Actually, our article on Lightning contains a pretty thorough explanation of how it works; and one could easily propose a reasonably hypothesis about how ants are able to predict thunderstorms based on the information there. --Jayron32.talk.contribs03:52, 26 May 2009 (UTC)[reply]
We assume the insects flying around were swarming ants seeking mates and new nest sites. I have always understood that ants use a simpler method of predicting thunderstorms. It is akin to the method that humans use - increased temperature, increased humidity and a change in atmospheric pressure. The ants I believe are not seeking to save themselves from death by drowning (you won't see this behaviour in autumn or winter)but attempting to use the properties of the thermals generated by thunderstorms to assist their dispersal. Of course the thermals in London at street level are likely to be limited but these creatures are not aware of that and valiantly strive to spread far and wide. Regarding voltage changes in the earth I wonder how all the electrical cabling that threads through London affects the local readings. Richard Avery (talk) 07:36, 26 May 2009 (UTC)[reply]
May 26
Understanding the Michelson-Morley Experiment
From what I Michelson did the experiment thinking that the speed of light was relative to the aether wind, like the speed of sound was relative to the air. But what does it mean the speed of sound is relative to the speed of the air? Does it work like the headwind-tailwind on a plane? If the sound is in an area with a 10 kph wind does that change the speed of the sound?
—Preceding unsigned comment added by 24.171.145.63 (talk) 01:46, 26 May 2009 (UTC)[reply]
As far as what people thought at the time of the Michelson Morley experiment, all speeds (velocities)change with respect to reference frames. For example, on the road, say you move in a car at 20kmph. You see another car moving towards you. By common sense you can tell that the car approaches you faster than if you were not moving, that is the velocities add up. Similarly, it is easily understood that if a car races past you in the same direction as your car, its not moving away from you as fast as it would have if you were standing on the road. This is the Principle of Galilean relativity. This also applies to the speed of sound, cars, and everything which moves at speeds sufficiently lower than that of light. But the Michelson Morley experiment found the speed of light to be same in all directions, even against the hypothetical ether. This violates the Galilean theory. This was resolved when Einstein proposed his Special theory of Relativity, which assumes the speed of light to be constant everywhere in all inertial reference frames. Rkr1991 (talk) 08:30, 26 May 2009 (UTC)[reply]
An alternative interpretation of the null result of the MM experiment that had to be considered is that the speed of light does change for a moving observer but that the universe contracts or expands in the direction of movement so that the light speed (i.e. apparent distance divided by time to traverse it) seems constant. Such a hypothetical contraction or expansion would include the observer so would not be observable. Cuddlyable3 (talk) 10:30, 26 May 2009 (UTC)[reply]
There are Newtonian models of light that are consistent with Michelson–Morley and distinguishable from each other and special relativity, like draggable aether and emission theories. Also, Lorentz–Fitzgerald contraction of the apparatus is enough to make Michelson–Morley produce a null result, you don't also need time dilation. This experiment didn't singlehandedly overthrow Galileo—it needs to be considered together with other experiments that ruled out the other possibilities. -- BenRG (talk) 20:11, 26 May 2009 (UTC)[reply]
Is it to make it more stable/support the weight of the engine or do fat tyres improve acceleration (do they typically increase the coefficient of friction between the tyres and the surface)?
Wider tires produce more contact with the road surface which decreases slippage, and thus improves the ability of the car's engine to push the car forward. If you take it to extremes, imagine trying to drive a car forward using tires as thin as a razor. You'd get almost nowhere. So you want as large of tires as practical, keeping in mind that really large tires also take a lot of power to get moving in-and-of themselves, so there is a tradeoff between being large enough not to slip too much to being too large to move efficiently. --Jayron32.talk.contribs03:46, 26 May 2009 (UTC)[reply]
And to preempt the objections, this is one of many places where the simplified classroom model (surface area doesn't affect friction) is not representative of reality. — Lomn03:55, 26 May 2009 (UTC)[reply]
Both answers above are incorrect. Lomn, the simplified classroom model is actually an excellent model ove a vast range of surface areas and materials. The dragsters tyres are no exception. The real reason the tyres are as big as they are is to keep them from overheating. Jayron is right about one thing, though. There is a tradeoff here and the tyres should be just large enough to avoid overheating but no larger, to minimize drag and inertia. Dauto (talk) 14:11, 26 May 2009 (UTC)[reply]
What?! Where did you get this information? They want the tires to be hot, not cold, for better traction. This is why they do a burnout. And the extra width does indeed improve traction. Friday(talk)18:38, 26 May 2009 (UTC)[reply]
The "high-school theory" is quite good for friction between rigid surfaces. Large tires apply little force to each part of the ground and therefore move it (horizontally) only a little. Thus, the larger the tires and/or the more solid the road, the better the rigid-ground model ought to be. On the other hand, thin tires may at any instant well happen to lie entirely on top of a round pebble and consequently roll whereever. Also, they tend to make deeper grooves into the soil (we're talking about off-road here, right?), during that moving in quite unwanted directions in a quite unpredictable way, not even talking about the energy wasted in digging.—Pt(T)19:41, 26 May 2009 (UTC)[reply]
In fairness to highschool (and college) teachers I recall being specifically taught that this model for friction only applied to theoretical perfectly rigid objects. APL (talk) 19:49, 26 May 2009 (UTC)[reply]
Oh dear - this silly argument again. Dauto is 100% wrong (just like last time - and the time before). The simplified frictional model completely falls apart when it comes to car tyres...as anyone who has ever actually driven a car both before and after putting big fat tyres on it will tell you. Cooling doesn't come into it at all. As Friday says, you really want your dragster to have hot tyres because the hotter they get, the stickier they become. That's why they always do a 'burn out' before they race - it's to get the tyres hot. On Formula 1 tracks, the pit crews actually keep the spare tyres in specially heated jackets specifically to avoid them being cold when the driver comes in to get a new set. I actually race cars for fun (Autocross) - my Mini Cooper has two sets of front tyres (it's a front wheel drive car) one fat pair for track days and one skinny pair for street driving. The 0-60 time is about 2.5 seconds faster on the wide tyres than on the narrow ones. Inertia is certainly an issue - but it's far outweighed by the additional grip. Heating is an issue - but it's the opposite to the way Dauto implies. You actually WANT your tyres to get hot. It's interesting to see the complicated dance Dauto has to go through to explain how come slick tyres (with no tread pattern) have better grip than all-weather tyres that have a tread pattern. The actual reason is because the slicks have more contact area - but the classical/high-school friction equations say that doesn't matter. Pah! SteveBaker (talk) 19:44, 26 May 2009 (UTC)[reply]
The 'd' probably comes from the word "difference" (or its equivalent in whatever language Leibniz liked to work in). --Tango (talk) 10:49, 26 May 2009 (UTC)[reply]
While the sectiondoes try to explain the notation, it seems to do this while going to great lengths not to ever mention the word derivative or link to further reading on the subject; instead the reader is presumed to understand what an "infinitesimally small displacement" is, what an "infinitesimally small length of time" is, and how the one can be divided by the other. I'm not sure this is really productive. —JAO • T • C11:29, 26 May 2009 (UTC)[reply]
Well, I'm not an expert, but i believe the answer comes from gravity. Most planets are very huge(otherwise they aren't called planets) so they have huge mass. Now we all know that because of gravity all masses attract each other, so all the little itsy bitsy particles which make up the planet end up attracting each other, which leads to the planet being under a compressive force, something which pushes itself in from all sides. This results in a spherical shape, as the body then comes under least strain, where all the particles are as close to each other as possible. So, the planets are almost perfect spheres, as other factors also have to be taken into consideration.(I'm guessing the other factors are things like the velocity of the body, the gravity of other bodies, various internal forces, etc.) However, we must note that this does not apply to smaller bodies, like asteroids, which can be seen of almost any shape. This is because the mas is too small for gravity to play a significant role in shaping them, so they are just like chunks of rocks floating around in space.. Also don't forget to sign your posts by placing four '~'s in the end...Rkr1991 (talk) 12:13, 26 May 2009 (UTC)[reply]
Not a very helpful answer, but strictly speaking the correct one: All planets are round because being (roughly) round is part of the definition of a planet! Asteroids are generally not round, because (roughly speaking) they aren't big enough. --Tango (talk) 14:12, 26 May 2009 (UTC)[reply]
Why would you call my answer not very helpful ? If there is any specific flaw i can correct it in all my future posts... Rkr1991 (talk) 14:32, 26 May 2009 (UTC)[reply]
You misunderstand me. My answer wasn't very helpful. If I were replying to your answer I would have indented my response further. --Tango (talk) 14:35, 26 May 2009 (UTC)[reply]
Ceres, the largest of our Solar System's asteroids is also now designated as a dwarf planet because it and only it meets the degree standard for roundness. See List of notable asteroids, and also note that because of rotation and the interaction of other gravitating bodies, the self-gravitation of an astronomical body will generally not result in sphericity, with flattening at the poles and the varying to one degree or another in shape being the total result.Julzes (talk) 15:49, 26 May 2009 (UTC)[reply]
A slap implies a firm strike with an open hand. I cannot envisage any normal circumstances where this needs to happen. A light slap of the face may possibly be used to rouse a person in danger of slipping into an undesired state of unconsciousness. There are procedures available within the UK healthcare system to express concern about such an occurrence. If a child, elderly person or a person with some other form of vulnerability is involved then an urgent explanation of the circumstances is required. If, on the other hand, this it research for a book the answer is still no. Richard Avery (talk) 14:51, 26 May 2009 (UTC)[reply]
No, I only meant in general, for keeping someone awake or wake up someone. I can imagine some situations when it would be useful. Imagine that you find an unconscious person with signs of poisoning. You might try to wake the person up to ask what kind of poison he took.--Mr.K.(talk)15:08, 26 May 2009 (UTC)[reply]
You would generally shake them, rather than slap them, I think. If you want to test someone's response to pain (for example, the work out their score on the Glasgow Coma Scale) the standard way is pressure to the fingernail bed. --Tango (talk) 15:18, 26 May 2009 (UTC)[reply]
I've got an auntie who used to be a nurse. As you may or may not be aware, overworked A+E doctors tend to have a *very* dim view of patients who fake unconsciousness. Apparently, it was not unknown for unnecessary 'needle biopsies' of the fingernail bed to be taken in order to test the malingerer's pain response... --Kurt Shaped Box (talk) 20:33, 26 May 2009 (UTC)[reply]
I've gotten the impression that it used to be customary for doctors to gently slap a baby immediately after its birth to see that it responded properly, i.e. by crying. Was this ever correct and, if so, is it still done? I have no personal experience in the matter. --Anonymous, 16:45 UTC, May 26, 2009.
It is certainly done on TV, and I think it did used to be done in real life as well. As far as I'm aware, it isn't recommended any more. --Tango (talk) 17:04, 26 May 2009 (UTC)[reply]
Yes, but the ends of babies are closer together; and, anyway, if you could be got to let out a loud wail by a potch on your tuchis, while inverted, I'll bet it would clear your airway. Deor (talk) 21:09, 26 May 2009 (UTC)[reply]
How do feathers contribute to bird's ability to fly? I have a general idea, but I am not finding anything about it in the articles. My general idea will send me to fluid mechanics next, but I am thinking it should be prioritized to get this into an article that is obvious to someone less knowledgeable than myself.Julzes (talk) 18:07, 26 May 2009 (UTC)[reply]
The critical thing about feathers is that when you push a feather upwards, it kinda unzips and lets air pass through fairly easily - but when you push them down, the little strips lock together to form a fairly airtight seal. This is a really useful thing because it allows a fairly simple vertical cyclic movement to generate lift. Bird flight is very different from aircraft, bat and insect flight. SteveBaker (talk) 19:31, 26 May 2009 (UTC)[reply]
These are large plates that (as far as I can tell from pictures) stick out sideways from the front of the engine. The purpose is to keep the smoke from obscuring the driver's view. Efficient engine design made them necessary, because it extracted more heat from the smoke as it passed through the boiler, making the smoke heavier. I have very little interest in steam trains, but certain things about smoke deflectors bother me:
Wouldn't they cause serious air resistance, perhaps enough to counteract the efficiency savings that make the smoke heavier?
Wouldn't the plates themselves block the driver's view?
Why not just connect the engine the other way round, so the chimney is at the back?
It would certainly improve the view if the engineer and fireman (for Brits, the driver and ??) were in front of the boiler. But wherre would the fuel and water be stored? The tender was behind the steam engine, and a short path from the coal supply to the boiler was essential. In an oil fired engine, it would have been possible to have the engineer at the front of the locomotive, as on modern diesels. As for efficient engine design eliminating smoke, there was still steam. Steam locomotives at the end in the 1960's still put up a very impressive cloud of smoke and steam. How much was the increase in ari resistance due to the steam deflectors in addition to that of the locomotive, its cab, and the vertical projections of the steam dome and other features? Steam or smpoke deflectors are not mentioned in the Steam locomotive article.
Do you have a reference to a book which discusses them? Pictures of locomotives show the smokestack way above the cab windows. Why would the smoke go down instead of up where it would be out of the way? There was a blower which gave it extra upward velocity on locomotives. Edison (talk) 22:56, 26 May 2009 (UTC)[reply]
Found the Smoke deflector article. Also Google book search has [25]. The smoke did sometimes drop and obscure the crew's view. Letting the engineer and fireman keep their heads inside the engine and be able to see signals and the track ahead seems a small price to pay for any slight increased drag. Edison (talk) 23:03, 26 May 2009 (UTC)[reply]
Smoke deflectors were placed parallel to the air stream - it's hard to imagine them making the vertical-front of the engine much worse than it already was. The front-view from the engine was never that great...but evidently they felt it was worth the small sacrifice in order to keep the smoke out of the way. I also get the impression that most of these were retro-fitted. SteveBaker (talk) 23:04, 26 May 2009 (UTC)[reply]
Oh, do they go edge-on to the airflow, rather than flat-on? That makes much more sense. It's kind of hard to judge perspective in the various pictures I've seen (which all look pretty much like the ones in our smoke deflector article), I got the impression they stuck out like ears. Well, if your ears stick out like that. Um. Edison's link took me to a copy of Popular Science with a picture of a highly streamlined locomotive with unique highly streamlined smoke deflectors. I feel generally happier about the whole concept now, thank you. 81.131.57.202 (talk) 23:22, 26 May 2009 (UTC)[reply]
Three points. First, the smoke deflectors were typically far enough
ahead of the cab that they didn't block much more of the forward view
than the boiler itself.
Second, while I've never seen actual numbers on this, it makes sense that
it's more efficient to lift the smoke by setting up a diagonal updraft
(using smoke deflectors) than by blasting it up vertically (as the older,
less efficient engines that did not use smoke deflectors did).
Third, there was one important example
of a steam locomotive design with the cab in front of the boiler instead
of behind; this was used on the California-based Southern Pacific Railroad.
As suggested above, these engines were oil-fired, and as the article
indicates, there were some problems with the design, including crew safety
in case of a collision and the effect of fuel leaks on traction. However,
I think the reason most railways kept the cab at the rear even with
oil-fired engines was probably that they wanted them easily convertible
in case they later switched to coal, and perhaps a measure of "that's
the way it's always been done".
There were also a few railways that tried locomotives with
the driving cab in the middle,
part way along the boiler. The man driving then had to work in a
cramped and hot space, and while he had better visibility on one
site, it was even worse on the other side; and he also couldn't
communicate with the fireman. Not a successful idea.
--Anonymous, 23:48 UTC, May 26, 2009.
Taken from the cat article: "Cats are classified as obligate carnivores, because their physiology is geared toward efficient processing of meat, and lacks efficient processes for digesting plant matter". Any cat would prefer meat in some form much more than cheese and bread. --131.188.3.20 (talk) 21:20, 26 May 2009 (UTC)[reply]
Though it is worth noting that cats can be pretty picky. I've had cats turn down human food that was obviously something that it theoretically would enjoy. (Dogs seem less finicky in this respect.) I'm not sure my old cat would have gone for burger. --98.217.14.211 (talk) 22:14, 26 May 2009 (UTC)[reply]
Most cats I've known have liked cheese, though. It is, as BenRG points out below, bad for them, though - adult cats, like most adult mammals, are lactose intolerant. --Tango (talk) 22:30, 26 May 2009 (UTC)[reply]
Please don't put this to the test; most cats are lactose intolerant and onion is toxic to cats, and who knows what else goes into a McDonald's hamburger that isn't tested on felines. -- BenRG (talk) 21:38, 26 May 2009 (UTC)[reply]
I think cheese doesn't contain much lactose, because the lactose is in the whey, which is removed. Also there is no mention of their alleged lactose intolerance in the cat article (although there is something about fatty acids), and there is a picture of "a very young cat being fed on milk"; and cats are famously portrayed as drinking milk - have they been given diarrhea all throughout history? - and of course they are mammals - does cat milk not contain lactose? Basically I don't believe you, except the bit about the onion, which I am going to accept unquestioningly and tell to other people. 81.131.57.202 (talk) 22:55, 26 May 2009 (UTC)[reply]
Adult cats are lactose intolerant. Most mammals lose the ability to digest milk after infancy, so there is no need to mention it specifically in the cat article. Humans are the exception to the usual rule, although even we only evolved to keep the ability very recently in evolutionary terms and there are plenty of people that don't have that mutation. --Tango (talk) 23:12, 26 May 2009 (UTC)[reply]
Oh yes, that rings a bell actually, you're right. Lactose intolerant people are not weird, it's those of us who can digest it who are the mutants, supposedly. Bit odd to lose an ability in adulthood, though, for no reason. I can only assume it's a side-effect of gaining some other advantage. 81.131.57.202 (talk) 23:27, 26 May 2009 (UTC)[reply]
The reason mammals lose the ability to digest milk is to ensure that one litter of offspring are properly weaned before the next litter comes along. The mother can only produce so much milk and if older offspring were competing against the newborns, that would be highly detrimental to the younger animals. Hence, all mammals have developed a system that makes them unable to digest milk past a certain age - and to have major discomfort should they try to do so. It is thought that humans were just like all of the others in that regard until perhaps 5000 years ago when we started to farm dairy animals such as sheep, goats and cows. Since we have language and education and societal pressures to ensure that babies are weaned off of their mother's milk soon enough - we no longer need the genetic shutting off of the lactose pathway. To the contrary - if you imagine a family who farm a few goats and who are lactose intolerant - then in times of famine - they'll be tempted to slaughter the goats for meat...and then they are in deep trouble. The family who happen to be lactose tolerant into adulthood can get their nutrition from milk, butter and cheese and keep the goats alive through to the next time of plenty. Guess who does better in the long term? It seems that 5000 years ago, we started to evolve the ability to drink milk in adulthood - but increasing civilisation means that very few people indeed survive preferentially because they can drink milk - so the evolutionary pressure to become lactose-tolerant has gone away - and here we hover, partly evolved, partly not.
The first five of those references might just be echoing a myth, since they just seem to blankly say, in gentler terms, "CATS ARE LACTOSE INTOLERANT ALRIGHT SO STFU", but I like the last one, it looks science-y. I like the term "vetinary technician". Also it confirms that "cow milk has higher levels of lactose than does cat milk", and explains about lactase. Still, none of them mention cheese. I think cheese is OK for cats, by reason of being low in lactose.81.131.57.202 (talk) 23:46, 26 May 2009 (UTC)[reply]
I tried to provide a variety, to suit whatever your doubts were that cats are like all other mammals. The third link, for example, links to advice from the RSPCA. Cheese is lower in lactose than milk; do you have a particular reason for thinking that the levels are low enough not to cause a problem for cats? Like most things, it will vary from cat to cat and by amount of cheese. 80.41.39.25 (talk) 01:06, 27 May 2009 (UTC)[reply]
I would assume that his particular reason for thinking that the levels are low enough to not bother a cat is that because you can get cheeses with zero lactose. It's not even a specialty item. Aged cheddar and sharp swiss are both commonly recommended to people who can't eat lactose, and both would be excellent on a cheeseburger.
Personally, I'd be more concerned about the roll. Does it still count as a cheeseburger if it's not served on a bun? Normally you could depend on a cat to simply eat around a bun, but if it soaked up the grease from a freshly cooked cheeseburger, I wouldn't bet on it. APL (talk) 01:32, 27 May 2009 (UTC)[reply]
You can get cheeses which are zero lactose, so those would probably be fine, but that isn't all cheese. Most cheeseburgers I've seen have come with those processed cheese slices; what are the lactose levels in those? Does it vary depending on the manufacturer and variety? I'm not saying you couldn't carefully construct something that would count as a cheeseburger and which a cat could safely eat, but I'm not convinced a random generic cheeseburger would be a good idea. 80.41.39.25 (talk) 01:43, 27 May 2009 (UTC)[reply]
You're right that American Cheese is probably the most common cheesebuger cheese thanks to McDonalds, Burger King, etc. But most sit-down restaurants (nothing fancy, your local diner will do) that serve cheeseburgers will offer one with cheddar or swiss. You couldn't trust the cheddar, though unless it specifically says "aged cheddar", and I can't seem to find any sources that say whether or not "mild swiss" has any lactose in it, so you'd really have to ask the chef.
But who are we kidding? What kind of diner is going to let your bring a cat? If your heart was set on giving your cat a cheeseburger you'd want to set up the old barbecue grill and do it yourself. Aged cheddar or sharp swiss are perfectly legitimate burger toppings, so I don't feel that's a cheat at all. I don't know what sort of other toppings are safe for cats, but they're purely optional and the cat probably wouldn't appreciate them anyway.
Here is a vet who says that, like with all other mammals, most cats do not retain the ability to digest lactase into adulthood, therefore giving an adult cat milk may lead to diarrhoea. Here is another vet who says the same, with less science. Or how about this? —Preceding unsigned comment added by 80.41.39.25 (talk) 01:16, 27 May 2009 (UTC)[reply]
The humour in "I CAN HAZ CHEEZBURGER" originates from its implication that the depicted cat desires a food that normally humans and not cats desire, in the same way that "INVISIBLE BIKE" is funny because people ride bikes, not cats. Dcoetzee21:46, 26 May 2009 (UTC)[reply]
I wonder how many generations of people cluelessly feeding cats saucers of milk or cream will cause them to gain the ability to digest milk. I have no idea how reliable it is, but I've heard anecdotal evidence that some adult cats are fine with it. I suggest that cat breeders start selecting for those cats so as to bring reality more in line with Tom&Jerry cartoons. APL (talk) 01:21, 27 May 2009 (UTC)[reply]
Unless the cats who do not drink the provided milk die off or breed less, that scenario will never produce a selection pressure. If a statistically significant number of cat owners fed only milk to their cats, only those who adapted would survive and reproduce; and lactose tolerance would evolve into the gene pool. Because most owners only provide milk as a "supplement," this will not happen. When cats choose not to drink milk, it does not impact their capability to breed. Nimur (talk) 01:45, 27 May 2009 (UTC)[reply]
I was imagining the people, in books and cartoons, who leave a saucer outside their back door for the neighborhood stray. But I don't suppose that's anywhere near common enough in real life to be a useful food source powerful enough to cause a selection pressure towards cats that can take advantage. Once again cartoons and books are more interesting than real life. APL (talk) 02:51, 27 May 2009 (UTC)[reply]
It is best to feed pets standard pet food. The standards set up (by?) are light-years better than the way the FDA is geared to handle human food.Julzes (talk) 03:25, 27 May 2009 (UTC)[reply]
Do you mean to ask which radio frequencies have wavelengths close to the 60 meter band? That would be HF radio or Shortwave. If you want a specific broadcaster, you will need to give a more precise wavelength and/or frequency, and probably a region as well (although shortwave does propagate almost globally). Nimur (talk) 00:13, 27 May 2009 (UTC)[reply]
And if you're hamming, take a look at this FAQ. The NTIA has granted five 2.8 kHz channels, (5332, 5348, 5368, 5373, and 5405 kHz center frequencies), for amateur use in the United States. Regulations may vary in your region. Are these the channels you were asking for? Nimur (talk) 00:17, 27 May 2009 (UTC)[reply]
Adding R-values for bulk ceiling insulation not allowed
I'm having a problem with this. I'm told that laying 2 layers of R 2.0 (S.I units) ceiling insulation wont give R 4.0. I understand this would be the case if the insulation (uncoated polyester) became compressed, or if the batts were not uniform in composition. The reflective value is not an issue as the standard the work is done to in this case is concerned only with heat transfer from the rooms to the roof (i.e winter insulation). The proposed technique is laying the first layer (10 cm thick) between the joists in the ceiling, and the second layer at right angles on the top completely covering the first layer and the joists as well. The joists themselves are rated R 0.6-0.8. The standard (AS 3999 - dont bother looking it up as you have to pay for it) allows R 4.0 (20cm)laid between the joists (not covering them) which I feel certain would give a lesser effective insulation than the cross-laid technique. R 4.0 insulation costs slightly more than two layers of R 2.0 This is a heavily relevant question as the Aust. Government has a massive rebate for ceiling insulation and many people are getting their ceilings done for the first time. I will check for answers here for several months, so late replies very welcome. Polypipe Wrangler (talk) 23:57, 26 May 2009 (UTC)[reply]
As I understood R-value, putting two layers of R 2.0 would yield an equivalent R value of 4.0. Of course, R-values are approximate anyway, within a very wide tolerance of the manufacturing and installation procedure. Nimur (talk) 01:29, 27 May 2009 (UTC)[reply]
May 27
Amalgam
Hi, I stumbled upon the article, electrolysis, some of questions were answered but one of them were not.
How is it possible for metals to be solved in mercury? Do metals actually become solved in mercury or do they just form an alloy? How does mercury absorb these metals? -Funper (talk) 01:10, 27 May 2009 (UTC)[reply]
Technically, they form an amalgam. Mercury is a liquid under standard laboratory conditions ("room temperature, atmospheric pressure"). When other metals, like gold or lead are added to it, the result is often a "soft" metal solid. For example, take a look at sodium amalgam. This compound ranges from a liquid to a "spongy gray mass" depending on the amount of mercury present. Nimur (talk) 01:32, 27 May 2009 (UTC)[reply]
MM Experiment
Michelson Morley Experiment- Sorry about this I'm the same guy who asked the earlier question. Anyway, the theory of the aether was that the aether was stationary right? The "wind" was generated by the earth moving through the field of aether, not the aether moving across earth right? Because from what I understand the results they were seeking were made with the assumption the aether speed was 30 km/s (the speed the earth orbits around the sun).
Secondly: (Sorry for this crappy drawing but w/e) Distance from Mirror A to half slivered mirror = Distance from Mirror B to half slivered mirror. BTW these drawing look weird so to better understand what I meant could you go to "Edit Summary" and look at them because I didn't mean for this formatting boxes.
MIRROR A
.
.
Light source----- /---- MIRROR B
.
.
.
Detector
This whole problem is assuming there is an aether wind. I'm trying to understand how Michelson constructed his apparatus, given he thought a wind existed.
Suppose the aether wind is coming down parallel to mirror A (suppose mirror A is the north, imagine the wind is blowing from North to South). Given that there is a wind, shouldn't the beam of light be deflected downward a little coming from the light source to the half slivered mirror (the / in the center)? As it won't strike the center of the mirror but rather a point a little below the center at a different incident angle then 45 degrees. In this case both beams would also be deflected and the light beam would not be split equally.
If this was compensated by angling the light source a little, so that the light went in a straight line from the light source to the half slivered mirror, then the beam of light going from the half slivered mirror to mirror B would be deflected downward a little.
MIRROR A
.
.
.
Light source----- /-
- DEFLECTED LIGHT BEAM
-
- MIRROR B
.
.
Detector
Sorry for asking questions that seem kinda dumb but ever place I looked it up only has a diagram similar to the first one I drew but I can't understand how that would compensate for a wind blowing. —Preceding unsigned comment added by 24.171.145.63 (talk) 02:09, 27 May 2009 (UTC)[reply]
Root growth in cut roses
About two weeks ago, I brought home some cut roses, which were placed in a vase containing tap water and the preservative that came with them. The roses withered slightly as one would expect, but they also seemed to develop small roots below the waterline. Does this happen often, and what might have caused it? Can these cut roses be re-rooted? 69.224.113.202 (talk) 02:25, 27 May 2009 (UTC)[reply]
Cutting (plant) does not specifically mention roses, but this is a common way to breed plants. I have heard it described as a special form of asexual reproduction as it can generate an entirely new organism without going through the standard pollination process. If conditions are right, the plant can survive and be replanted. Nimur (talk) 03:07, 27 May 2009 (UTC)[reply]
Pyrgus (species uncertain)
Hamearis lucina?
The caterpillars.
The tree.
Another view.
![[19]](http://members.lycos.co.uk/scaryduck/blog2/bustergonad.gif){kind=link}
