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December 16

What is a Hill sphere of Sun?

What is a Hill sphere of Sun? Basically at what distance from Sun object will orbit Galaxy center rather then Sun? If you can, please use AU when answering. 70.52.184.140 (talk) 02:47, 16 December 2010 (UTC)

I thought the article on comets might help and indeed under the heading of "single period comets" was the answer The Sun's Hill sphere has an unstable maximum boundary of 230,000 AU (1.1 parsecs (3.6 light-years)).. Vespine (talk) 04:41, 16 December 2010 (UTC)

I'm not sure that's accurate. The comet article cites a 1964 Paper by Chebotarev as the source for that figure - that paper is reproduced in English here - the relevant section is section 6 "solar gravitational sphere", pp621-622 of the original journal. There Chebotarev says "For the mass of the galaxy we assume the value M=1.3 × 10¹¹ solar masses." And indeed if one runs that through the formula given for a simple (non-eccentric) system given at Hill sphere, one gets a value for r of 225837 AU (with the value for the semimajor axis Chebotarev cites); that's consistent with the 230,000 value he gives.

But that paper is 46 years old, and it looks like the current estimates of the galaxy's mass are quite different. Looking first at Wikipedia's numbers - Milky Way says its mass is roughly 1.4×10⁴² kg, and the Sun article says its mass is 1.9891×10³⁰. Going by those figures, the mass of the galaxy is 7.038×10¹¹ solar masses, making the galaxy 6 times more massive than Chebotarev's numbers. Running that through the equation (with a slightly refined value for a, again from Sun) gives us a Hill radius of 130,261 AU (down from Chebotarev's 230,000).

But there's more. If you ask Wolfram Alpha for "mass of the galaxy" it says 6×10⁴² kg which it says is "based on 2009 velocity data from Mark Reid using the Very Long Baseline Array (VLBA)" (I guess that's the finding discussed here). That gives us a mass ratio of 30.2×10¹¹, making the Hill radius about 80,000 AU - that's about a quarter of Chebotarev's number.

I've done the math on this in a hurry, so I'd be grateful if someone could check my numbers. But it does look like Chebotarev's calculation is based on a very wrong estimate of galactic mass. -- Finlay McWalter ☻ Talk 19:41, 16 December 2010 (UTC)

Moreover, ask Wolfram Alpha "distance from the sun to the centre of the galaxy" and it says 2.349×10²⁰ m (it cites a bunch of astronomical sources). That's quite a bit lower than the values given by Wikipedia or Chebotarev; plugging that into the equation and we get an estimated Hill radius of 75,350. It's noteworthy that the estimated radius of the Oort cloud is around 50,000 AU. -- Finlay McWalter ☻ Talk 19:59, 16 December 2010 (UTC)

Wow, I'm going to bookmark you if I ever have any astronomy questions, great answer. Vespine (talk) 04:35, 17 December 2010 (UTC)

A poem and its related biological/neurological functions:

I just wrote this poem and am curious for someone to shed light on the biological function breakdown of the things I exclaim in it...

Entry004:

The tier on which love operates at its prime; a prime that has seemingly lasted forever, and has no plans of changing anytime soon: (In no particular order of importance..)

Getting to actually know her, her secrets, what makes her tick,, the like; and loving every part about them.

Evolving my golden standard in perfect sexual chemistry, and furthermore the best sex ever even beyond what I once deemed fathomable.

She is the absolute definition of beauty, be it both in pure hotness, cutest, or most gorgeous (Jewish accent)i. And is such a good fuck, yet also the mistress of making love all with a synergistically perfect” key-lock combo”

And all of these things intersect in spacetime…

A-A-W. Cuddlyable3 (talk) 10:51, 16 December 2010 (UTC)

Current electricity

Even though current is scalar why the directions are assigned? —Preceding unsigned comment added by 180.215.52.172 (talk) 10:56, 16 December 2010 (UTC)

One of the properties of a direct electric current is that it is accompanied by a magnetic field. The magnetic field is described by vectors and the orientation of these vectors is dependent on the direction of flow of the electric current. Therefore it is possible to identify the direction in which the electric current is flowing. Dolphin (t) 11:32, 16 December 2010 (UTC)

Scalars can be signed. Ginger Conspiracy (talk) 07:04, 17 December 2010 (UTC)

To say that perhaps a bit more clearly, current is not actually a scalar, it is a vector. In many applications it is possible to simplify things by working only with the magnitude of current and ignoring its direction, but even so it does have a direction. Looie496 (talk) 00:10, 18 December 2010 (UTC)

Current is certainly a vector. Consider applying an electric potential across an anisotropic conductor such as a piece of graphite: the direction of the current will depend on both the direction of the field and the orientation of the graphite (and in general will not be parallel with the field. --ColinFine (talk) 23:51, 19 December 2010 (UTC)

Prison Riot

in a Prison Riot do the guards get raped —Preceding unsigned comment added by 66.66.92.152 (talk) 13:39, 16 December 2010 (UTC)

I don't know. Which particular prison riot did you have in mind? I'd imagine that in some cases, guards get assaulted. No idea on the nature of the assault. --Jayron32 14:27, 16 December 2010 (UTC)

The Wikipedia article on Etiquette does not address the issue but such an action would conform less than favourably with the Manners that are due to a kindly person who tucks one in at night. Cuddlyable3 (talk) 16:19, 16 December 2010 (UTC)

A simple search for 'prison guards raped riot' finds [1] which suggests it's a common fear among guards that it may happen in a riot (it also mentions one riot where it happened among hostages which I guess includes guards), our article New Mexico State Penitentiary riot which mentions some some guards were treated for beatings and rapes (it also mentions several prisoners were tortured, burned and killed in the riot) and [2] on the 25 (or 26 if you include the fun one) worse riots which includes the New Mexico State Penitentiary riot (the only other prison related item in that list is the 1981 Irish hunger strike, it's perhaps not the best source considering it says the Kosovo is Serbia protest 2008#Protest in Montenegro was about Serbia recognising Kosovo). As Jayron said it obviously happens, whether it happened in any particularly riot, you'd need to look in to that riot. Nil Einne (talk) 17:01, 16 December 2010 (UTC)

Whip scorpion

What do whip scorpions do with their tails? The Wikipedia article says nothing about this, which is odd, since it is a pretty distinguishing physical characteristic of the creature in question and the origin of its popular name.

This site says they use them in self-defense. (How?) This one says it is a sensory organ. (What kind?) In general there seems to be a lot less discussion of this on the web than I'd expect.

What's the truth? Can someone find a solid reference and update the article with it? --Mr.98 (talk) 14:42, 16 December 2010 (UTC)

Interesting question. All the scholarly articles I can find on defensive behavior focus on the composition and effects of the chemicals released from the glands at the base of the tail. Seems like the defensive use of the whip is a bit of a red herring, although it may help them mimic regular scorpions to scare away predators. This article is probably a good source, but I can't easily find it online; Biologie der Geißelskorpiones (Uropygi Thelyphonida) J Haupt - Memorie della Società Entomologica Italiana, 2000 SemanticMantis (talk) 16:26, 16 December 2010 (UTC)

Just because its tail has a different shape than other scorpions' doesn't mean it won't have a stinger. The smaller tail likely allows greater agility for dual use as a feeler. Ginger Conspiracy (talk) 07:01, 17 December 2010 (UTC)

Whip scorpions do not have stingers on their tails. Cursory googling will give you plenty of references. SemanticMantis (talk) 16:49, 17 December 2010 (UTC)

Boat movement problem

If a boat is moving in upstream with velocity of 14 km/hr and goes downstream with a velocity of 40 km/hr, then what is the speed of the stream ?

I assume that this is a homework problem and you meant to say that the stream is flowing at the rate of 40 km/hr (although that's mighty fast, so maybe that's the boat and the stream is flowing at 14 km/hr). We won't do your homework for you but can help with how to solve it:

1) If both the boat and stream are moving in the same direction (downstream), then you just add the numbers together and that's how fast they are moving downstream.

2) If they are going in opposite directions then you subtract the smaller number from the larger, and that's how fast it's going, and whichever original direction number was larger, that's the direction it's going. So, if the upstream speed is bigger, then subtract the downstream speed from it and that gives you how fast it's going upstream. But, if the downstream speed is bigger, subtract the upstream speed from it and that gives you how fast it's going downstream. (This problem can also be done by adding two numbers, one of which is negative, but that's more complicated). StuRat (talk) 15:07, 16 December 2010 (UTC)

x-y=14
x+y=40
x= boat speed
y= stream

although i guess you could switch the variables —Preceding unsigned comment added by 173.166.164.91 (talk) 15:41, 16 December 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.

Just to clarify: if motion upstream is positive and motion downstream is negative, and x and y are as you define them above, so that x+y=14 km/hr relative to a stationary observer on the bank of the river, what would x-y be then? Is that what you are talking about, or is it something else? WikiDao ☯ (talk) 20:55, 16 December 2010 (UTC)

Paul Dirac Equations??

I was watching a BBC4 program last night regarding equations and was drawn in by the enthusiasm of, I assume, a Dirac fan.

He wrote down an equation that I believe represented some explanation to the overall understanding of matter/anti-matter but cannot find this equation listed in the Wikipedia page on Paul Dirac.

The equation is as follows:

i,gamma,p,spinner = m,spinner

Please advise where I have mis-understood what was being relayed and if this equation exists? —Preceding unsigned comment added by 86.10.74.128 (talk) 14:51, 16 December 2010 (UTC)

The equation you're looking for is the Dirac equation, which in natural units such that $\hbar$ and c are 1 can be expressed as

$i\gamma ^{\mu }\partial _{\mu }\psi =m\psi$ .

See also Dirac spinor. Red Act (talk) 16:48, 16 December 2010 (UTC)

A bomb’s flash, Why would it happen?

From the NYT: "the scientists found that a bomb’s flash would blind many drivers, causing accidents and complicating evacuation. " However, wouldn't the glass block the UV, therefore, not blinding drivers? 80.58.205.34 (talk) 17:18, 16 December 2010 (UTC)

It is more than just UV that burns, it is virtually the whole spectrum. The flash can melt the retina -even if your wearing shades..Effects of nuclear explosions--Aspro (talk) 17:34, 16 December 2010 (UTC)

Also, you're only considering permanent damage, but for someone driving, even momentary/short-term vision impairment is a problem. A bright visual flash can do that (consider your visual ability right after staring directly at a flashbulb, or a Flashbang grenade). DMacks (talk) 17:38, 16 December 2010 (UTC)

According to one of his memoirs, Richard Feynman shared your reasoning and watched the Trinity test through a windshield with no goggles. --Sean 19:52, 16 December 2010 (UTC)

About 40 years ago I read that AND he also described his observation point being about 20 miles from the initiation site. Considering the intensity of light falls off as the .... of the distance... etc. A windscreen (laminated with PVA as opposed to triplex as common in 1940 auto mobiles) provides little if any protection to flash blindness emanating from a bucketful of sunshine.

According to flash blindness, a 1-megaton bomb can cause temporary blindness at a distance of up to 13 miles. The Trinity nuclear test was only 20 kilotons, so it seems plausible that Feynman would be fine observing it directly at a distance 20 miles. Of course, it was certainly a non-trivial risk to decide to look at the very first detonation since he couldn't really be sure what the effects would be. Dragons flight (talk) 21:35, 16 December 2010 (UTC)

Or what the yield would be, for that matter. But it should be remembered that 20 kt was actually a very high yield for the bomb. It was expected that it would be far less efficient than that — most scientists involved had guessed it would be only a kiloton or two at most. --Mr.98 (talk) 21:50, 16 December 2010 (UTC)

It's of note that Feynman himself reported an impressive afterimage at 20 miles. If he was driving said car, and had no idea that a bomb was about to go off, would he have kept it together or would he have crashed it? We can't know, obviously, but it's worth noting that even in the Feynman scenario (ideal from a number of standpoints), it was still a pretty potent visual effect. --Mr.98 (talk) 21:48, 16 December 2010 (UTC)

Indeed. In Surely You're Joking, Mr. Feynman!, he recounts

"Time comes, and this tremendous flash out there is so bright that I duck, and I see this purple splotch on the floor of the truck."

While he wasn't completely blinded, he saw one heck of an afterimage. Even though Feynman was expecting the blast he still reflexively turned away from it; consider the effect on a motorist moving at speed and caught by surprise. 04:48, 17 December 2010 (UTC)

Does the volume of cylinder affects Pressure

Let consider I have a cylinder filled with compressed gas (let air), if half of gas is taken of would the pressure of remaining gas reduce. Here I mean that when the half of cylinder will be empty then the remaining gas will have some volume to expand inside the cylinder so will the pressure decrese..? —Preceding unsigned comment added by 220.225.96.217 (talk) 20:32, 16 December 2010 (UTC)

Yes. This is an example of Boyle's law, which is a special case of the ideal gas law that applies when the temperature is constant. Red Act (talk) 20:44, 16 December 2010 (UTC)

However if the gas is partially liquified due the high pressure than some of the liquid will evaporate filling the space and keeping the pressure constant, as long as there is enough liquid inside. 71.101.41.73 (talk) 03:08, 17 December 2010 (UTC)

Why fog is mostly seen in morning ?

Why fog is mostly seen in morning ?. and disappear as the sun shines.... does it because we can't see them in darkness of night... or is there some science behind that...? —Preceding unsigned comment added by 220.225.96.217 (talk) 20:37, 16 December 2010 (UTC)

The sun heats up the earth, which allows the air to hold more moisture, so the fog (floating water droplets) evaporate. --Sean 20:44, 16 December 2010 (UTC)--Sean 20:44, 16 December 2010 (UTC)

Fog happens when the ground is warm and moist and the air is cold. That situation is more common in the morning, but can also happen at other times of day if a mass of cold air moves into an area where the ground retains heat. Looie496 (talk) 21:12, 16 December 2010 (UTC)

See Fog#Types. The type of fog that develops overnight (and you can see in the morning) is called "radiation fog" and the one that's made by moving air masses such as a Warm front is called "advection fog". Alansplodge (talk) 09:30, 17 December 2010 (UTC)

@Sean - Air does not "hold" moisture. For a full explanation (and, for the OP, a clear and very accurate description of how fog is created) see here and here for a more in-depth background. Matt Deres (talk) 23:44, 17 December 2010 (UTC)

Fog is essentially a cloud on the ground. The Sun increases the temperature of the near-surface air in the last morning so as to decrease the relative humidity of the air so the fog droplets no longer form. Ice fog also often occurs in the morning as does black ice. ~AH1^(TCU) 02:33, 18 December 2010 (UTC)

Why on every Wathc they write Quartz ?

I have seen many watch from hand watch to wall clock and seen that all of them having written Quartz on them.. why so ... is there any component which is made of Quartz. or it is some kind of patent...? —Preceding unsigned comment added by 220.225.96.217 (talk) 20:39, 16 December 2010 (UTC)

See quartz clock. --Sean 20:44, 16 December 2010 (UTC)

Thanks to cheap quartz watch brands such as Swatch, having a quartz crystal is not the novelty it used to be, so the "quartz" labelling is not always shown. Cuddlyable3 (talk) 01:12, 17 December 2010 (UTC)

Though labeling tells you that it doesn't need to be wound in any way. The counterpart on older (wound) watches was a listing of how many jewels it contained. --Mr.98 (talk) 03:22, 17 December 2010 (UTC)

Yea, it's a bit like finding a radio that boasts "stereophonic sound !" ... you know you have an antique. StuRat (talk) 05:05, 17 December 2010 (UTC)

This is an excellent little video that describes how a quartz watch functions. --Mr.98 (talk) 13:47, 17 December 2010 (UTC)

It's a pretty video but gives no idea of the circuit needed to make the crystal oscillate, just connecting a battery won't do. It would also have helped to explain why 32768 Hz is chosen, it is 2¹⁵ cycles per second. Cuddlyable3 (talk) 20:54, 17 December 2010 (UTC)

Quartz watches are practically normal and have nothing to do with quality. I have a watch that cost 1 US dollar and it says "quartz" on it. --Chemicalinterest (talk) 14:34, 18 December 2010 (UTC)

Thallium(I) oxide production

Can it be made by burning thallium powder in air or would that also make the sesquioxide? --Chemicalinterest (talk) 22:04, 16 December 2010 (UTC)

I'm not a chemist but isn't it unlikely that simply combusting it in air will result in a significant amount of the (I) oxide? I would guess there will be a lot of other oxides, including nitrogen oxides. Vespine (talk) 23:27, 16 December 2010 (UTC)

I can't find the exact answer, but the reaction of thallium with moist air produces TlOH. The standard method for production the anhydrous oxide is by decomposition of the carbonate at 700 °C. To produce the sesquioxide, you seem to need an oxidizing agent that is stronger than air (e.g. Br₂), but I'm going on fairly sparse data there. Physchim62 (talk) 23:49, 16 December 2010 (UTC)

From doi:10.1006/jcht.1993.1128 Tl₂O made by Tl₂O₃ volatilized at around 1000 K in a stream of water-vapor/oxygen, which equilibrates with TlOH under those conditions. DMacks (talk) 10:30, 17 December 2010 (UTC)

Thallium(I) carbonate, I presume, is made by reacting thallium(I) oxide with carbon dioxide... --Chemicalinterest (talk) 12:09, 17 December 2010 (UTC)

December 17

Pterodactyls

Could someone explain for me in layman's terms, what the difference between a pterodactyl, pteranodon and a psterosaur is? I've seen all three terms used interchangably in writing in the past. Thanks. —Preceding unsigned comment added by 95.148.109.104 (talk) 00:09, 17 December 2010 (UTC)

Pterosaurs were the whole order of flying reptiles. Pterodactyloidea was a suborder of pterosaurs. Pteranodon was a genus of large flying reptiles. --T H F S W (T · C · E) 00:29, 17 December 2010 (UTC)

And I really wanted to answer that question! :) But yeah, he covered it. Crimsonraptor (talk) 00:37, 17 December 2010 (UTC)

In even more layman's terms... Pterosaurs is a term which includes a lot of different species of dinosaurs. Pteranodon is a sub-group of species within that group. Pteranodon is a sub-group within that group, which contains two species, which are usually the specific birds you think of when you refer to Pteranodons. --Mr.98 (talk) 14:38, 17 December 2010 (UTC)

"Birds", maybe, but not birds! --Sean 17:24, 17 December 2010 (UTC)

That's not layman's terms, it's just completely incorrect. THFSW had it right - none of the terms listed have ANYTHING to do with dinosaurs or birds. Please be more careful before you try correcting someone who knows what they're talking about. 64.235.97.146 (talk) 18:11, 17 December 2010 (UTC)

Untreated ringworm does... what?

Ringworm is apparently quite common in both humans and other animals. When humans get it (assuming a certain level of medical care is available) they can resolve the problem quite quickly with modern antifungals and such. But what happens if the dermatophytosis is left untreated, as one would expect for a stray dog or cat? Does the fungus just happily reside on the surface of the skin indefinitely? Does it eat deeper and deeper into the tissues? The ringworm article kind of sucks. The Masked Booby (talk) 01:35, 17 December 2010 (UTC)

I would imagine that ringworm may itself not be harmful in the long term, but it greatly increases the risk of secondary infections, due mostly to the fact that you are scratching it all the time. Those secondary infections could be a major problem, and could perhaps be too numerous and varied to list here. --Jayron32 02:25, 17 December 2010 (UTC)

There's an old story that claims that a ringworm around the abdomen will kill you when it completes a full circle. Not sure of that statement's validity. ~AH1^(TCU) 02:28, 18 December 2010 (UTC)

The same myth exists with shingles. Complete balderdash of course! Caesar's Daddy (talk) 08:25, 18 December 2010 (UTC)

Side Issue: Does the ban on medical advice extend to veterinary medicine? Sfan00 IMG (talk) 12:01, 20 December 2010 (UTC)

Tiger cheese

Are there any carnivores whose milk is consumed by humans? LANTZY^TALK 03:36, 17 December 2010 (UTC)

Historically and prehistorically, it seems rather unlikely. You'd have to feed them meat edible to humans, whereas cows and such eat things we can't. Plus they'd be liable to be a whole lot less docile and prone to evil thoughts of eating their keepers. But hey, you may have hit upon a novelty product. Clarityfiend (talk) 04:55, 17 December 2010 (UTC)

But lots of carnivores eat things we wouldn't want to eat, like cats eating mice and dogs eating skunks (which might just curdle their milk :-) ). StuRat (talk) 05:02, 17 December 2010 (UTC)

Ugh! Finish all yummy mice, Tumak. Are Neanderthals in cave somewhere starving! Clarityfiend (talk) 05:24, 17 December 2010 (UTC)

People do drink dogs milk sometimes, here's a vid of a kid, but adults probably do it too (although maybe not directly). There is also pig cheese and presumably milk too. Ariel. (talk) 06:25, 17 December 2010 (UTC)

(Edit Conflict) Romulus and Remus legendarily fed on a wolf's milk, and I vaguely recall accounts (not necessarily verified) of more recent feral children similarly surviving temporarily on an adoptive canid or other wild animal's milk. 87.81.230.195 (talk) 06:37, 17 December 2010 (UTC)

Didn't the King James Bible have a verse in Genesis saying something like "Seven sons did milk a bear?" Edison (talk) 00:59, 18 December 2010 (UTC)

If you're going to call a bear a carnivore (hint, they're not, except Polar bears), then we should also consider Human milk, which many people consume as an infant, and occasionally later in life. Buddy431 (talk) 02:48, 18 December 2010 (UTC)

A couple more thoughts. The cost of keeping meat-eating critters is much higher than what you could possibly get back in the form of milk. On a more practical note, who're you going to get to milk a tiger? Clarityfiend (talk) 02:53, 18 December 2010 (UTC)

Is this whole thread somehow inspired by Tiger's Milk? --Trovatore (talk) 03:19, 18 December 2010 (UTC)

Crazy kid again... with more subjective thoughts that y'all will hopefully objectify

So through a little bit of work with a pencil and a sheet of paper, i wrote out an arbitrary word problem requiring simple algebra to solve. It was then I realized that if i were to translate this word problem into an equation that each kind of word in the english language (i.e. noun, verb, adjective etc.) would have a parallel mathematical meaning. In algebra class in middle school I was told that the word "of" just meant times. and that makes perfect sense. If was wondering... If I was to ask myself simply "What do I see in my room?" could I answer it in an equation form like ... I see a blanket then assign a variable to the blanket lts say (B) and a mattress then label that mattress L.. to answer my question I would now be able to say What I see = B + M... what I am curious about is going further. Let say I wanted to describe M in more detail by maybe.. saying that whatever function (mattress manufacturing and shipping and whatever else it took to get to my room) lead to the mattress being in my room and being part of my answer for what I see in my room...how would I combine certain aspects of my overall equation

Given

What I see in my room = B + M

M exists because of the function of why it's in my room M(x), x being whatever variables account for why the mattress is in my room.

So now I have

What I see in my room = B + M= B + M(x)

Is any of this correct at all?

Where can I find instructions on how to translate words into pure equations? — Preceding unsigned comment added by BloodWasPassion (talk • contribs) 04:39, 17 December 2010 (UTC)

What you're trying to do looks like the branch of artificial intelligence called knowledge representation and reasoning, which typically represents real-world information in semantic networks. It also touches on computational linguistics, in particular computational semantics. And all of this is a part of natural language processing. Red Act (talk) 05:15, 17 December 2010 (UTC)

How did the mattress get from L to M? You might enjoy Word problem (mathematics education) or Internet Relay Chat (e.g. [3]) more than the reference desk. Ginger Conspiracy (talk) 05:34, 17 December 2010 (UTC)

About Styrofan (construction Chemical from BASF )

Hi, This is Vinay from Bangalore India. can some one give me answers to the following: a) What are the chemical compositions of Styrofan b)Why & how Styrofan should be used in READY MIX CONCRETE what are the proportion c)How many types of styrofan is there & how many of them are for ready mix concrete PLZ SOMEBODY HELP ME ITS VERY URGENT TRIED LOOKING THE WHOLE INTERNET BUT COULD NOT FIND MUCH PLZ PLZ IF IT IS POSSIBLE TO MAIL THE ANS here is my id [removed]. looking forward for the ans

with regards Vinay —Preceding unsigned comment added by 59.97.26.3 (talk) 09:59, 17 December 2010 (UTC)

A) It's water-based styrene butadiene

B) It's a protective coating or binder used for fibre bonding or as an adhesive.

C) There seem to be 19 types

Zzubnik (talk) 10:15, 17 December 2010 (UTC)

I removed the poster's email address, per refdesk standard (ask-here, answer-here; avoid spam-harvesters, etc.) DMacks (talk) 10:22, 17 December 2010 (UTC)

This appears to be the internet resource you're looking for... Physchim62 (talk) 11:06, 17 December 2010 (UTC)

Maxwell's demon (MADE IN JAPAN)

A radioisotope thermoelectric generator

• http://neocoat.jp/neo/english/comparison.html

It seems like this revolutionary paint does not decompose under the sun (chemical heat absorption). Its high-tech molecules just vibrate and keep heat from entering your house.

Are they selling Maxwell's demon by the bucket in Japan? -- Toytoy (talk) 10:42, 17 December 2010 (UTC)

This is the sort of question where things can get very complicated. So, forget about this paint advert which attempts to baffle with science and read this simplified explanation of reflectance/ low emissivity. Low emissivity for use at high temperatures Wikipedia does have an article about low emissivity but it is not easy to take in at a single reading. Note also that high performance heat sinks, such as those found in top class sound systems and on radioisotope thermoelectric generators etc., are nearly always matt black.--Aspro (talk) 14:58, 17 December 2010 (UTC)

Maybe the best WP article is Radiant barrier--Aspro (talk) 15:31, 17 December 2010 (UTC)

I think there shall be a way to make a not-so-Maxwellian-demon heat shield:

• You have to have a material that is capable of phase or chemical change at about 25 deg C.
• The location must have very hot days (e.g., 35 deg C) and very cold nights (e.g., 15 deg C).
• The target room temperature is about 25 deg C.
• You have a great scientist to make this material a commercially successful paint.

During the day, the material absorbs solar energy and undergoes phase or chemical change. The change keeps the external surface from getting very hot. As a result, the house does not get too hot during the day. The paint layer has to be very very thick to act as a heat sink.

Then during the night, the external temperature drops very quickly. The paint releases heat and its phase or chemical change is reversed. Since the inside of the house is warmer than outdoors, the paint releases most of its heat to the cold outside air.

During winter days, this dark-colored material absorbs heat and heats up your home.

Then the paint releases heat to the outside during winter nights. You must have a good heater and a cheap source of fuel otherwise you will be very sorry ...

This certainly is not a solution for everyone of us. -- Toytoy (talk) 16:36, 17 December 2010 (UTC)

That has nothing to do with the paint, which was the subject of your question. Your prediction is now too far into the realms of a crystal ball to warrant further discussion. You have now shown you are just asking lots of questions here on the reference desks because you have nothing better to do. --Aspro (talk) 18:43, 17 December 2010 (UTC)

Is that not allowed? 81.131.62.210 (talk) 19:21, 17 December 2010 (UTC)

??? It's not a crystal ball to ask if something is scientifically feasible. He's not asking about the future. If you don't have anything to say about it... then just don't say anything! Don't be so arrogant as to proclaim that nobody can have anything to say about it. --Mr.98 (talk) 13:24, 18 December 2010 (UTC)

Cryogenic revitalization

Is it possible to revive someone many many years into the future after they have been cryogenically frozen?

We do not presently have the ability to do this, and it is unknown if we will ever be able to do that. Some people do freeze themselves (typically shortly after death), with the hope that future doctors will one day learn how to revive frozen people. See: Cryonics. Dragons flight (talk) 18:12, 17 December 2010 (UTC)

Also note that the freezing process causes ice crystals to grow inside the cells, which destroys them. Unless they find a way to completely prevent this, the chances of ever reviving someone so damaged are very low. StuRat (talk) 19:04, 17 December 2010 (UTC)

There are a few types of animals that are capable of freezing and then reviving -- their cells make a sort of antifreeze that prevents the formation of ice crystals. My sense is that if animals can do it, then sooner or later there will be a technology that allows it to be done to humans, but of course we're in the crystal-ball realm here. Looie496 (talk) 20:34, 17 December 2010 (UTC)

Freezer burn is a major problem in this process, and surgeon nanorobots could be one solution. ~AH1^(TCU) 02:22, 18 December 2010 (UTC)

Vitrification freezers are another. It's a freezer and a microwave; two appliances in one! The Japanese have the best, in the food processing (edamame/soybean preservation) industry, since ice crystals change the texture of frozen vegetables, too, by destroying cell walls. Ginger Conspiracy (talk) 13:44, 18 December 2010 (UTC)

I've always thought one of the biggest problem with cryogenics is that you'll be trying to revive someone who is not only frozen but who is already dead. We need to find a cure for death before we need to worry about defrosting. DuncanHill (talk) 13:48, 18 December 2010 (UTC)

Reviving a mammal who died because of hypothermia and has been preserved since (i.e. by cold) is possible. It takes an electric shock such as from a defibrillator, an artificial respirator, and a way to evenly warm them back up. If there has been severe ice damage, they won't revive. With moderate ice damage they will revive and die a horrible, really disgusting and painful death in less than a day. Light ice damage is survivable with a decreased expected lifespan and infertility in females (the ova are the largest cells, and thus most susceptible to ice crystal damage.) There seems to be a general agreement among researchers to discontinue cryonics research on mammals over a kilogram until vitrification technology improves such that ice crystals aren't expected to be a serious issue. Improvements have been slow and steady, but vitrification freezers are nowhere near human mass range yet. Ginger Conspiracy (talk) 08:14, 19 December 2010 (UTC)

RationalWiki's Cryonics article is much better than ours. Ginger Conspiracy (talk) 01:58, 19 December 2010 (UTC)

It's generally believed that their memories and personality are stored in the structure of the brain, so it's not theoretically impossible. Whether or not our current cryonics technology is sufficent and whether or not technology will be sufficient to repair the damage or replace it outright are open questions. There's not much we can do to find out if it's possible. We may be able to work out how much damage is being done to the neurons, and find out if it's too much for the person to live normally, but there's no reason to believe most of that damage couldn't be fixed. There's a big difference between a neuron being gone, and being replaced by one with a best guess of where it's supposed to attach. Theoretically, they only need enough information to be able to distinguish you from the average person. They don't need your body to find out how humans in general work. — DanielLC 19:29, 20 December 2010 (UTC)

There is no reason to believe that long term survivability is not directly proportional to the mass of body tissue which can be frozen and thawed without ice crystals, which is a physics appliance engineering optimization problem. I am confident that the colonization ships are on schedule. Ginger Conspiracy (talk) 20:46, 20 December 2010 (UTC)

Error in Image

In the image File:Decay chain(4n+1,Neptunium series).PNG it says Uranium-223 inside the octagon it should say Uranium-233. 174.112.211.143 (talk) 21:01, 17 December 2010 (UTC)

Fixed it, thanks. --Sean 21:26, 17 December 2010 (UTC)

What percentage of the air expelled rearward from a jet engine actually thrusts an aircraft forward?

Seems like a pretty basic question, which would have the pretty basic answer of "all of it". But I've been looking around our articles and widely through google and can't seem to get the answer. What I am trying to determine is how much of the thrust comes from the exhaust from the jet engine pushing against the atmosphere behind the aircraft, and how much comes from the thrust pushing forward against the engine itself. How is it that in a vacuum a rocket/jet engine pushes itself forward even tho there is nothing behind it to push on? Anyone? —Preceding unsigned comment added by 222.152.15.198 (talk) 21:29, 17 December 2010 (UTC)

You don't need the mass you expel out the rear of the rocket to "push" against anything. The mere fact that you are expelling that mass is what propels you. Googlemeister (talk) 21:35, 17 December 2010 (UTC)

Do you mean that the mass is pushing against the engine to make it (and the aircraft) go forward? I'm not trying to be cute here Googlemeister. If I blow up a kid's balloon and then let it go it will fly around like crazy. Will it behave the exactly same in a vacuum as in my house? If yes, then I guess the answer to my question is that zero % of the air expelled rearward from a jet engine actually thrusts an aircraft forward.—Preceding unsigned comment added by 222.152.15.198 (talk) 22:30, 17 December 2010

Yes, it will behave much the same in a vacuum. That means 100% of the gas expelled from a rocket pushes it forward, but it's all done by Newtonian reaction, not by pushing against some external medium. You get the same effect by firing a gun (the reaction pushes you backward) or a firehose. The little maneuvering jets that astronauts use to fly around when they're outside a space station are quite like a can of hairspray, and indeed an astronaut could take a (big) can of hairspray with them and use it to move them - they just point it in the opposite direction to where they want to go and push the button. -- Finlay McWalter ☻ Talk 23:08, 17 December 2010 (UTC)

Let's say you're kneeling on a skateboard and you're holding a brick. You throw it forwards as hard as you can. What happens to you? You go in the opposite direction, and it's not because the brick is pushing against the air. See Newton's Third Law. --Sean 22:13, 17 December 2010 (UTC)--Sean 22:13, 17 December 2010 (UTC)

I think the answer to this question might not be simply 100% or 0%. Let's compare walking, flying in a jet, and flying in a rocket. In all three cases, some fuel is consumed, to get the energy to move something, to obtain an reaction in the opposite direction. In the case of walking, we burn food and move the earth very slightly. The jet burns fuel and moves the air. The rocket burns fuel and moves the fuel. Question is, can't the jet also be said to be expelling its fuel to some extent? It needs air in order to burn the fuel, but if the air was carried onboard, it would be a rocket, and its fuel would be part of what it was expelling. So, now I'm just confused by what the question means, sorry. 81.131.15.161 (talk) 06:49, 18 December 2010 (UTC)

Ahhhhh, wonderful wikipedia. Thanks for your input, but I'm sorry my clumsy question wasn't clear. What I was trying to find is whether the stuff coming out of the back of a jet engine propels the aircraft forward by pushing against the air behind it or does it propel the aircraft forward by by pushing against the engine? Finlay McWalter has cleared this up admirably, but I can tell you that reading wiki's relevant articles does not truly spell out the answer for people not au fait with the science terminology. Like me. —Preceding unsigned comment added by 222.152.15.198 (talk) 07:10, 18 December 2010 (UTC)

And Finlay explained that it is not by anything "pushing against" anything. I'm guessing you're thinking of newtonian reaction as a sort of 'pushing against', but I don't think that's very helpful: in Sean's example, is the brick pushing against you? --ColinFine (talk) 00:14, 20 December 2010 (UTC)

I don't see why you don't think it's helpful. The answer is, yes, the jet engine is pushing against the exhaust, and the exhaust is pushing back. The original question seems to ask for a breakdown of how much of the thrust comes from each; that part is based on a misunderstanding. The answer is that the engine pushing on the exhaust, and the exhaust pushing back, are actually the same phenomenon.

So 100% of the thrust comes from the engine pushing on the exhaust, and also 100% comes from the exhaust pushing back. And that doesn't make 200%; it's just two ways of saying the same thing. --Trovatore (talk) 00:19, 20 December 2010 (UTC)

Huh! I thought I had it sorted and then, whammy! Surely that would create zero effect? The engine pushes aft at X and the exhaust pushes forward with the same X force? —Preceding unsigned comment added by 222.152.15.198 (talk) 00:32, 20 December 2010 (UTC)

Get a sack of bricks. Hold them while standing on a skateboard. Throw the bricks very fast one by one behind you. Use this analogy to answer all your questions. 92.24.188.27 (talk) 16:02, 21 December 2010 (UTC)

Sure, but you didn't explain why! If I let my balloon go in a vacuum it will fly around madly. Doesn't that mean that 100 % of the pressurised air released from the balloon drives it forward by pressing against the inside of the balloon, and zero % of the expelling air drives the balloon forward by pressing on something outside the balloon (because there is nothing to act against)? Ah, the answer was there all the time, in Finlay McWalter's post above. As you were.

Here's the famous 1920 New York Times editorial that says rockets can't fly in space. 81.131.15.161 (talk) 08:29, 18 December 2010 (UTC)

But let's be fair. They did apologize for that... during Project Apollo. --Anonymous, 18:00 UTC, December 18, 2010.

Does gravity slow down time?

Someone said that clocks are faster in space than they are here on Earth. Supposedly standing next to a pyramid will slow down time by a fraction of a second. Is this true? ScienceApe (talk) 21:45, 17 December 2010 (UTC)

Yes, that is correct. Under Einstein's general relativity, time flows more slowly in a gravitational field. See also our article on gravitational time dilation. TenOfAllTrades(talk) 21:54, 17 December 2010 (UTC)

There are two different effects at work for the most famous clocks in space, the GPS system. 1) Being further from the Earth makes them run faster, gaining 45 microseconds each day. 2) Moving really fast in their orbits makes them run slower, losing 7 microseconds each day. Combined, they would gain 45 - 7 = 38 microseconds each day. Luckily, some smart people thought about this and made the necessary corrections. Details. --Sean 22:31, 17 December 2010 (UTC)

Gravitational time dilation is also the more important effect for satellites in geosynchronous orbit. But for something in a very low orbit, such as a space shuttle, relative velocity time dilation is the more important effect, so clocks on the space shuttle run slower than they do here on Earth. To the right is a graph of how the two effects vary with orbital radius. Red Act (talk) 22:47, 17 December 2010 (UTC)

The pyramids are no different than any other big chunk of rock in this respect. You might as well have mentioned Mount Rushmore. Even so, they're pretty much meaningless. Even our entire planet only changes time by a handful of microseconds per day. The pyramids are minuscule in comparison. APL (talk) 03:06, 18 December 2010 (UTC)

I just plugged in some numbers into the equation for gravitational time dilation. Compared to a stationary clock far from anything, a clock at the surface of the sun runs slow by about 0.18 seconds per day. So being next to the sun slows a clock so much that it's measurable with a cheap stopwatch. Compared to a clock far from anything, a clock at the surface of the Earth runs 60 microseconds slower per day. So being next to the Earth slows a clock by too little to measure with a stopwatch, but very easily enough to be measured with an atomic clock, which is accurate to about 10^-9 seconds per day. But a clock that's about 150 meters from the center of the Great Pyramid, which has a mass of about 5.9x10⁹ kg, will only run about 2.4x10^-15 seconds slower per day due to being next to the pyramid. So being next to the Great Pyramid slows a clock by vastly too little to be measurable by even an atomic clock. Red Act (talk) 08:28, 18 December 2010 (UTC)

My fuzzy potatoes

I bought a bag of sweet potatoes a couple weeks ago, and now they are moldy. I kept them in a cool place (around 60°F), so I was surprised by this. I frequently treat regular potatoes this way, and they don't rot nearly so quickly, but they do occasionally grow sprouts:

1) So, am I right in thinking that the regular potatoes stay alive after they are harvested, and that their immune systems stop decay, while sweet potatoes die and decay immediately thereafter ?

2) If so, what is it about normal potatoes that allows them to survive in my cupboard while sweet potatoes can't ?

3) I wanted to switch to sweet potatoes because they are more nutritious, but does this also make them more hospitable to mold ? StuRat (talk) 22:33, 17 December 2010 (UTC)

Moldy sweet potatoes and months-old "perpetual stew"? You won't need a pension. Re stew, see Bacillus_cereus#Pathogenesis 92.15.4.135 (talk) 14:08, 18 December 2010 (UTC)

Drench them in the same amount of anti-fungal treatment, ensure the RH is low and you probable wont notice any difference.--Aspro (talk) 23:28, 17 December 2010 (UTC)

RH ? Do you mean pH ? And do they really treat normal potatoes with an anti-fungal agent ? If so, why don't they use it on sweet potatoes, too ? StuRat (talk) 23:35, 17 December 2010 (UTC)

Relative Humidity. Roots store well if they are in a dry environment. It is pretty basic stuff they teach school girls in domestic science.--Aspro (talk) 00:16, 18 December 2010 (UTC)

Wikipedia even as an article -as it always does- on Domestic science. Wikipedia is an amazing resource, one should use it more often--Aspro (talk) 00:47, 18 December 2010 (UTC)

Mycotoxins are very harmful, You should throw them away and not eat them. Even the parts that look OK will have the toxins in them. 92.28.242.98 (talk) 23:57, 17 December 2010 (UTC)

Meh. Mold is everywhere, even if you can't see it. Unless things turn soft and yucky, the usual solution is to just cut away the moldy parts. Looie496 (talk) 00:03, 18 December 2010 (UTC)

Professor Sir John Berry would disagree with you. Read the section "Benefits as ephemera" in his article here http://www.spiked-online.com/Articles/00000002D29C.htm Risk, science and society. Unfortunately the diagram seems to be missing. "...Derived from data reported by Mongeau et al (12) on the production of carcinogens (furocoumarins) in infected parsnips {but also applies to other moldy food}. Healthy roots produce little of these toxins, but when infected they are found in greatly increased amounts throughout the parsnip, not simply in the visually altered areas....Cutting out the damaged bits of spoiled vegetables is not sensible". I've noticed that people I assume to be North Americans have such an uncritical attitude to food; yet a large proportion of cancers, heart disease, strokes etc are the result of food choices made in previous decades. 92.15.4.135 (talk) 13:56, 18 December 2010 (UTC)

(EC with 92 and Looie4961) I'm not aware of that practise and I'm not sure what the heck is meant by RH. But to start at the beginning... our concepts of "dead" and "alive" are much blurrier for plants than they are for animals (which can also be tricky) and become downright irrelevant when you start talking about bits and pieces of plants. However, there is usually a period of continued metabolism (usually the transformation of starch into sugars) followed by either an extended period of dormancy or a breakdown of the plant material by outside action (i.e. mold, bugs, potato chip manufacturers, etc.) So, when you harvest a tuber, there are already a number of things going on: there are all manner of microorganisms that have set up shop, but which haven't yet taken hold, there is internal metabolism changing the more complex carbohydrates into sugars, and there is a small release of water vapour, etc. What the mold wants is a warm, dark, damp environment in which to get on with its business. Between the ground and your pantry, it doesn't get as many of things as it would like: the spuds spend time out in the dry air, there isn't that much sugar available, and the skin is relatively dry. But time goes on: sugars increase, there is a buildup of moisture, you've stuck the spuds in a dark drawer, and the metabolism within the tuber is warming it slightly. The longer the potato sits, the more optimum the conditions get for the mold to grow until the inevitable happens. So, why would your sweet potatoes get moldy faster? The same reason you call them sweet: five times the sugar content! And not only odes that give mold a leg up on a normal spud, sweet potatoes also come from further away, meaning they've been out of the ground longer, been in the dark of a ship's hold for longer, and so on. Matt Deres (talk) 00:07, 18 December 2010 (UTC)

PS - my reference for the "five times the sugar content" thing ended up getting blacklisted; Google sugar content potato versus sweet potato and you'll find it. Matt Deres (talk) 00:09, 18 December 2010 (UTC)

My sweet potatoes and yams store very well for months in the kitchen. Perhaps you kept them in a plastic bag or other container which retained moisture. In the rural US, historically they were very easy to keep all winter, longer than regular Irish potatoes or apples. They are hard and relatively dry and stay that way. Your post is very puzzling. Exactly how did you store them? Edison (talk) 00:51, 18 December 2010 (UTC)

You're right, I left them in the plastic bag I got from the store, but I've now removed the survivors and they are now in 20% humidity. Hopefully that will solve this prob. StuRat (talk) 05:14, 18 December 2010 (UTC)

My thoughts too! So, I reiterate what I posted above: Relative Humidity. Roots store well if they are in a dry environment. I reiterate: It is pretty basic stuff they teach school girls in domestic science.---Aspro (talk) 01:04, 18 December 2010 (UTC)

There was no need to reiterate and there would have been no need to explain yourself at all if you had simply been more helpful from the outset. Your snide condescension is also out of place. Matt Deres (talk) 01:31, 18 December 2010 (UTC)

Agreed. StuRat (talk) 05:11, 18 December 2010 (UTC)

One of the issues which has not been discussed is where the OP gought the sweet potatoes from? Unless you know the provenance of the potatoes, they could have been MONTHS old by the time you bought them. A sweet potato which is a few hours out of the ground will likely be indistinguishable from one which is a few months out of the ground; there's no way to tell whether the sweet potato you bought at the SuperMegaMart has months of shelf-life left, or is just about to go off... --Jayron32 00:59, 18 December 2010 (UTC)

In a related Q, do sweet potatoes get worms ? Because some of them have a circular hole about a millimeter in diameter in them. At the store there were some small flying insects buzzing around them, so do the worms grow wings when they mature ? StuRat (talk) 05:22, 18 December 2010 (UTC)

I don't see why not. There are literally too many possible flys and their associated maggots to name which may infest sweet potatoes. Maybe some type of Drosophilidae? --Jayron32 06:55, 18 December 2010 (UTC)

Note that potatoes are an Andean crop which survives the winter underground. In regions subject to the depredations of war or oppressing armies (such as Ireland) they were often harvested throughout the winter so that a military force couldn't effectively seize them from the populace. And of course seed potatoes can be chopped up and replanted. So the life of the potato, under normal circumstances, really isn't in doubt. Wnt (talk) 05:17, 19 December 2010 (UTC)

The conversation is not about potatoes, it's about sweet potatoes. Sweet potatoes (Ipomoea batatassometimes, sometimes called yams, but unrelated to yams) are more closely related to morning glories than they are to "regular" potatoes (Solanum tuberosum, which are closely related to tomatoes and other members of the nightshade family). Their only shared similarity (versus non-"potato" plants) is that they both have starchy underground tubers that humans dig up and eat. Even then they're not really all that similar, as a a sweet potato is a root tuber, while a regular potato is a stem tuber/stolon. -- 174.24.216.113 (talk) 18:16, 19 December 2010 (UTC)

December 18

Maize recycling...

How to present the recycling method of maize — Preceding unsigned comment added by Raunakstha (talk • contribs) 03:20, 18 December 2010 (UTC)

I'm not sure I follow. One doesn't usually recycle food. One usually eats it. Unless you mean composting food waste?!? I am thoroughly confused. Could you elaborate. --Jayron32 04:26, 18 December 2010 (UTC)

Never seen a corn field Jayron? The OP is almost certainly referring to the ~80% of the plant that's not edible - the stalk, leaves, etc. In rural China people collect it by hand and use it for heating fuel. That's not really what I'd call recycling, though. The Masked Booby (talk) 04:57, 18 December 2010 (UTC)

Then there's the silk, cobs, and leaves from the corn left after you eat it. StuRat (talk) 05:00, 18 December 2010 (UTC)

Roughly one-quarter of the world's food is wasted or uneaten. Perhaps the OP is referring to "recycling" and redistributing this food? ~AH1^(TCU) 15:48, 18 December 2010 (UTC)

It is not an uncommon practice for farmers to put cattle in the harvested field to eat the remaining vegetable material. Googlemeister (talk) 14:29, 20 December 2010 (UTC)

MCAT en Français

Hello. Are there any plans of a French equivalent of the MCAT to be recognized by Canadian medical schools underway? Thanks in advance. --Mayfare (talk) 03:25, 18 December 2010 (UTC)

There are three francophone medical schools in Quebec, at the Université de Montréal, the Université Laval and the Université de Sherbrooke. Sherbrooke appears to run its own equivalent of the MCAT, the TAAMUS (Test d’Aptitude à l’Apprentissage de la Médecine à l’Université de Sherbrooke) [4], while Montréal [5] and Laval [6] don't mention anything about a specific aptitude test in their publicity. Physchim62 (talk) 12:52, 18 December 2010 (UTC)

Why does warm air hold more moisture than cold air

I've heard two explanations: that the warm air transfers more energy to the water, preventing it from forming water droplets; and that there is more space between air molecules in warm air, and droplets tend to form in the spaces between air molecules. Which is right, and could anyone knowledgeable elaborate on the explanations? Thanks a lot!74.15.138.27 (talk) 08:02, 18 December 2010 (UTC)

It has nothing to do with "holding". You are thinking about it wrong. There's always PLENTY of space in air (or any gas) to hold more molecules of anything. Indeed, gases at earth atmospheric conditions are on the order of 1/1000 as dense as solids or liquids, meaning that there is generally about 1000 molecular volumes of empty space around each molecule of a gas. So there's plenty of "room" in the air. The reason that warm air has a higher absolute humidity has to do with the competing forces which determine the phase of a substance:

• Intermolecular forces are the forces of attraction between the molecules of a substance. These forces are why solids and liquids exist at all.
• Heat is the energy of molecular motion. The faster molecules move, the greater the forces needed to slow them down.

Now, in a gas, there will always be a range of speeds of molecules. The higher the temperature, the greater number of molecules will be moving at faster speeds. Molecules which don't move fast "enough" to overcome the intermolecular forces will condense out of the gas phase. So the deal with warmer air is, warmer air has a higher percentage of water molecules which will be moving fast enough to avoid sticking to each other than colder air, which is why warmer air has a higher "carrying capacity" for water vapor. So, the first explanation you have is "closer" to the truth. The second one, about having more space between air molecules, is pretty much bullshit. If that were true, then there would be LESS impetus to form water droplets, because the molecules of water would be farther apart on average, and so the intermolecular forces trying to make them condense would be less effective. --Jayron32 13:18, 18 December 2010 (UTC)

Thanks. 74.15.138.27 (talk) 02:38, 20 December 2010 (UTC)

ACMA blacklist

whats it — Preceding unsigned comment added by Kj650 (talk • contribs) 14:19, 18 December 2010 (UTC)

Information_published_by_WikiLeaks#Internet_censorship_lists explains it. SmartSE (talk) 14:50, 18 December 2010 (UTC)

The lists leaked by Wikileaks can be still be found at their website (or one of its mirrors): AMCA blacklist. Buddy431 (talk) 23:46, 18 December 2010 (UTC)

A lead on leads

Were leads ever made from lead? Reason for asking: I have some ancient resistors and they are corroded similar to lead. --Chemicalinterest (talk) 14:32, 18 December 2010 (UTC)

Electronic "leads" (pronounced LEEDS) are so named because they are the point of contact between a device and other devices, and thus "lead" (LEED) the connection between the two devices. This has nothing to do with the element "lead" (LED) per se. --Jayron32 14:36, 18 December 2010 (UTC)

From my reading of the question, the OP never suggested such a connection. Dismas|^(talk) 18:13, 18 December 2010 (UTC)

According to its article, it's soft and has poor conductivity, so it would have been an odd choice. Clarityfiend (talk) 21:31, 18 December 2010 (UTC)

The resistors are most likely carbon, not lead. -- kainaw™ 21:52, 18 December 2010 (UTC)

Although I appreciate learning extra facts and tidbits of scientific information, I don't think my question was answered. Did leads originally contain lead? --Chemicalinterest (talk) 22:30, 18 December 2010 (UTC)

I have seen them made from iron, copper and silver. I am sure that somebody tried lead, but the low melting point of lead makes the use very problematic if you solder. resistance is no problem when you only have 5mm length with 0.5mm diameter.--Stone (talk) 22:53, 18 December 2010 (UTC)

The answer is No. "Leads" on electrical components are named from O.E. lædan "cause to go with one, lead"[7]. The name of the metal "lead" has a different root W.Gmc. loudhom. Electrical leads (LEEDS) have nothing to do with the metal (LED), though one can quip that the terminals on a Lead–acid battery are stubby leads of lead. Cuddlyable3 (talk) 23:00, 18 December 2010 (UTC)

The solder used to join leads to components is likely to contain lead. DuncanHill (talk) 00:10, 19 December 2010 (UTC)

Well, yes. The leads (ledes) on electronic components are likely to be tinned with solder, which contains lead (led, or perhaps Pb). But the led is there to melt and make soldering easy, and the lede (most often copper, or Cu) is there to provide conductance and physical strength. Led would be useless as a lede because it melts easily and doesn't conduct well at all. PhGustaf (talk) 00:36, 19 December 2010 (UTC)

The coating or "tinning" of tin-lead solder on the copper wires coming out of the resistor make it much easier to solder them into a device. Bare copper would oxidize and have to be scraped clean immediately before it was soldered. The Pb metal would make a lousy conductor to use in attaching a component, because it is more prone to break than copper, has higher resistivity, and would be prone to melt and separate during soldering. Old time fuse wire, dating back to 1880 or earlier, contained lead, I believe, like solder. A short link of it would melt and interrupt the current when there was a short or a sever overload, before the copper conductors could overheat and start a fire. Edison (talk) 04:18, 19 December 2010 (UTC)

The Degradation of the Human Race by Doctors

Susceptibility to certain bacterial or viral diseases is inheritable in some persons. (A doctor will sometimes ask a patient what his father died of.) If these susceptible people get the disease to which they are prone, medical science will often be able to keep them alive longer than would have been the case in the pre-medical era. The disease-prone people will therefore live longer and will be able to have children or more children. As a result, the proportion of disease-prone people in the population will continually increase. As medical science advances, the problem will accelerate. The burden of supporting and treating the unwell will eventually become intolerable on those who are healthy. Can anything be done about this? How about mandatory sterilization of these persons? This would be one more of the Draconian measures that will be needed if human life is to continue on this planet.-- Diatom. 173.189.136.110 (talk) 15:07, 18 December 2010 (UTC)

This article speaks to your concern, but is focused on domestic dogs [8]. On the other hand, the fact that our medical practices may be decreasing negative selective pressure on deleterious human alleles could also result in broadening the evolutionary search space, allowing our descendants the possibility to develop beneficial mutations that would not be available without negative intermediate forms. Also, since you speak of human sterilization programs, you may enjoy reading up on ethics. SemanticMantis (talk) 15:36, 18 December 2010 (UTC)

I do not like the idea of enforced sterilization. But it may become a necessity as the lesser of two evils. And after all, there is always the possibility of adopting a child. As for waiting for mutations to counteract disease susceptability, the burden of supporting and treating a great many unwell persons may become intolerable. I am talking about a very long term effect - Long term versus shortt term is a known problem in ethics. Diatom. 173.189.136.110 (talk) 17:00, 18 December 2010 (UTC)

The fears about dysgenics have generally been considered over-exaggerated in modern medical contexts, and societies generally will not tolerate compulsory sterilizations anymore done in the name of eugenics. Consider whether you yourself would be happily compulsory sterilized if tomorrow DNA testing told you that there are a statistically higher chance that your offspring would be susceptible to some common virus or bacteria. The social medicine seems worse than the disease in most such cases. --Mr.98 (talk) 15:50, 18 December 2010 (UTC)

Mr.98, you refer to the Wikipedia article on compulsory sterilization. However that article does not deal with the increasing influence of medical science on prolonging life of disease-susceptible persons. That can be expected to continue, with more and more of these persons living longer and longer, and producing more children.

Compulsory sterilization has three aspects:

1. The sterilization of persons of a certain race. The Nazis did some of that.

2. The sterilization of persons who have an inheritable disease, without considering the affect medical science may have in continually increasing the proportion of such persons in the population.

3. The same as item 2, but taking into consideration how medical science allows such persons to continually increase in proportion to the population.

As for society usually being opposed to compulsory sterilization, society takes only a short term view of it. Diatom173.189.136.110 (talk) 17:47, 18 December 2010 (UTC)

Diatom, are you soapboxing? It is a very complicated issue with many factors and implications and a tragic history. I think the answers you have been given so far (above and below this post) have been quite good treatments of this difficult subject, and you should consider them more carefully before trying push further your point that "society" is taking a "limited" view of it. WikiDao ☯ (talk) 18:57, 18 December 2010 (UTC)

This process has, of course, gone on for a long time. Just blame the people who started using fires, enabling individuals with weaker teeth and stomachs to survive and beget children. Or those pesky weavers, who allowed people with insufficient body hair to survive the cold! Humans have always adapted their environment to their benefit, and then evolved to better utilise this environment. Doctors are part of our new environment. Immunity to a disease does not come for free - it comes at a biological cost. If this ability is not needed, it will vanish, and free resources that may allow us to evolve new features useful in our modern environment. Of course, sometimes changes in human lifestyle are slower than evolution. As a result, we still get fat on Big Macs, although for most of us there is little likelihood of ever experiencing life-threatening starvation. --Stephan Schulz (talk) 16:00, 18 December 2010 (UTC)

As for fire and weaving, a similar, partly successful, solution has been developed for disease susceptability. It is medical treatment. But that is often expensive, time consuming, and sometimes requires repeated treatment. There are somtimes serious side effects or infection. It would be muich better to eliminate the susceptability.

Regarding mutations, they are rare. I don't think there has been one in all of human history. Diatom.173.189.136.110 (talk) 20:11, 18 December 2010 (UTC)

Chances that you are not a mutant are negligible. According to this paper, there are 175 mutations per generation. Most of them are neutral, of course. Very few indeed give you superpowers ;-). --Stephan Schulz (talk) 20:24, 18 December 2010 (UTC)

(e/c) Right, but we can afford the expense of health-care (in an overall sense), the modern medical infrastructure has become a part of our environment to which we are adapting short-term (epigenetically, culturally, etc.) and long-term (genetically). Technology will improve those processes, at least eventually in ways that are acceptable to us and don't have unexpected bad consequences. I don't know what you mean by there having been no human mutations, though, you should go read an article or something. ;) WikiDao ☯ (talk) 20:27, 18 December 2010 (UTC)

(edit conflict) They are not rare. There are about 175 mutations per human genome per generation. [9]. Since ~98% of the human genome is not directly associated with protein coding, most of the mutations fall into innocuous regions that have no effect. Some fall on critical genes and the resulting embryo in not viable, leading to spontaneous abortion. But on average, you can expect every baby has around 1 gene (out of 23000) that has been mutated to be different from both their parents. In some cases the effects are profound and deleterious, but in many cases the effects are subtle and not obvious. Dragons flight (talk) 20:29, 18 December 2010 (UTC)

Well, it depends what you mean by "mutation". Every human being is different. They have a different face, for instance. Even identical twins are different - they have different fingerprints, for instance. So it could be said that every person is a mutant. But still, I think there will be a long, long wait for disease susceptability to disapear or turn into something beneficial from that cause. And it will only happen to one person at a time. Diatom.173.189.136.110 (talk) 20:42, 18 December 2010 (UTC)

Mutation has a very well-defined meaning, so we don't really get to choose. Some fairly well-known mutations are the development of Lactose tolerance and the Sickle cell trait. --Stephan Schulz (talk) 20:54, 18 December 2010 (UTC)

The most important thing to bear in mind when thinking about issues like this is that unless selection is extremely rigorous, its effects take dozens of generations (at minimum) to become significant. So in principle it may be correct that if current practices are continued for thousands of years, human vulnerability to disease might increase. But given the vast number of more pressing problems we face, it's hard for me to feel terribly stressed about this. Looie496 (talk) 18:52, 18 December 2010 (UTC)

And it is certainly not the case that people in places with better medical care and longer lifespans produce more children! In fact it is usually exactly the opposite: the more exposure to education, medicine, and wealth a population has, the more their reproduction rate declines. --Mr.98 (talk) 19:50, 18 December 2010 (UTC)

I don't like to ask - but are the Germans healthier than people in other countries, or is there no difference? Did their killing/murdering of disabled people have the effect on the German gene pool that they expected? 92.15.1.13 (talk) 20:01, 18 December 2010 (UTC)

Well, those unfortunate victims of the Nazis certainly did not pass along susceptibility to disease unless sthey had children earlier. Diatom.173.189.136.110 (talk) 20:26, 18 December 2010 (UTC)

This would not be measurable against the noise background, much less separable from other differences due to health system and living circumstances. Also note that eugenics was not limited to Germany, even if the Nazis were particularly ugly at it. --Stephan Schulz (talk) 20:17, 18 December 2010 (UTC)

We are just now entering the era when genetic modification is possible. I wouldn't be surprised to see medical treatments during the next century that routinely eliminate disease causing alleles. That seems a far more likely outcome than any form of forced sterilization. Dragons flight (talk) 20:09, 18 December 2010 (UTC)

The real genetic answer to why eugenics doesn't work is pretty simple. The kind of "weeding" you are talking about only works if there are no recessive traits. If there are recessive traits, then you have to "weed" out people who don't express the given condition as well, which is a vastly greater number than the "sick" population. The Hardy–Weinberg principle essentially makes it clear that if you only sterilize those who express a trait, it will never appreciably affect the total amount of expression in the total gene pool.

Now, what you can do is prevent expression in the form of aborting fetuses with expressed conditions. That is what is done on Cyprus in the instance of thalassemia — the number of carriers in the population remains constant, but the number of those born with the full disease zeroed out in a single generation, because of the use of amniocentesis and selective abortion. It's a controversial case, one that only seems to have gone over on Cyprus because the effects of expressing thalassemia are so violent were becoming such a drain on families and the health care system that people were basically not having kids. I doubt you could do that with the much more minor things you are describing above. The ethics are problematic, in any case, and you aren't actually affecting the "healthiness" of the gene pool — just the "healthiness" of those who get to be born.

Genetics is in any case far more complicated in most instances. There are relatively few conditions that are caused by strict Mendelian heredity. If you start adding in more complicated risk factors (e.g. genetic factors which put one at high risk for breast cancer), you start getting a much wider net of whom would have to be sterilized in order to achieve your "healthier" society. The sweep of eugenics would have to be much more radical than even the Nazis were able to accomplish under a fascist state. It's not feasible. It's not ethical. It's not really very sound science, either. --Mr.98 (talk) 21:43, 18 December 2010 (UTC)

Doesn't that mean that genetic diseases ought to be increasing over time, in all populations of animals? 213.122.10.39 (talk) 01:29, 20 December 2010 (UTC)

I agree with most of the responses above, and would like to add that eugenics (or breeding, in the case of animals) also fails because what we choose as "healthy" genes may not be what is best for society. For example, eliminating the gene for sickle-cell anemia may cause malaria to spread. And some mental "diseases", like manic-depressive disorder, seem to lead to astonishing periods of creativity. And there may be many other hidden benefits to some of those mutations you dislike, that we haven't yet figured out. StuRat (talk) 00:08, 19 December 2010 (UTC)

I agree that the degeneration of the human genome in response to poor selection should take a very long time, though it is not infinite. The success of feral pigs in many regions should attest to the potential of humanity to shake off the legacy of domestication. In the very long term however we might need to consider the effects of increased background radiation from uranium which has been cracked into shorter-lived isotopes, which will almost inevitably tend to spread throughout the world over time. But it is fair to say that genetic modification should be able to reverse such effects.

I would also contend that genetic medicine can be differentiated from eugenics. The reason is that with the broad population data that is being gathered, it becomes possible to tell how long ago a mutant allele arose in the population. Sometimes it can be determined that it started fresh in the patient, parent, or grandparent; other times a longer estimate will be needed. By drawing a line between recently arisen mutations and longstanding alleles, it is possible to undo the damage from "disease alleles" whose fate, most likely, was to be expunged from the gene pool in any case, while recognizing the intrinsic value of alleles that have survived many thousands and often millions of years through having some special use. However, I'm not aware of this being a published or accepted sentiment. Wnt (talk) 05:12, 19 December 2010 (UTC)

Night vision of seagulls and other birds

I've often seen seagulls flying around after dark this winter. They may be confused by the very bright street lighting. 1) Do seagulls and other birds have good or any night vision? 2) I once heard it would probably kill a bird to disturb them from their roost after dark, as they would be unable to find another in the dark. Is this true? Thanks 92.15.1.13 (talk) 20:07, 18 December 2010 (UTC)

As a rule, most diurnal birds have middling-poor night vision. they are not night-blind, but probably don't have the visual acuity needed to fly through woodlands or underbrush safely. This may not be of too much concern for gulls, since they tend to frequent 'open sky' regions without too many obstacles to run into. And no, it won't kill a bird to disturb it from its roost at night, but it might harm itself if it smacks into a branch in the dark. --Ludwigs2 20:57, 18 December 2010 (UTC)

Some other birds to indeed have excellent night vision (see Bird_vision#Nocturnal_birds). Some gull species are highly adaptable. Nocturnal Scavenging by Gulls in the Southern North Sea is one study that mentions nocturnal activity (following trawlers and their discard) among Larus argentatus, Larus marinus, and Larus fuscus. The abstract concludes with "they should be regarded as neither nocturnal or diurnal by preference in this area". Perhaps it applies to other civilized areas with yet more tasty scraps too. ---Sluzzelin talk 21:16, 18 December 2010 (UTC)

Hi. I was summoned... :) According to this 1914 article by R. M. Strong (page 24) "It has been my experience that the Herring Gull has nearly as good darkness vision as man at least". Just so happens that I was reading that the other day, heh. Personally, I have seen Herring Gulls happily feeding in the streets in the middle of the night and heard their contact calls as they fly overhead before sunrise. They seem to see just fine. I also read an article recently where it was mentioned that GBB Gulls will raid tern nests at night.

As for other birds, I can tell you that Budgerigars have *very* poor dark vision. If they fall off their perches in the night, they struggle to find them again and will flap around their cages in a panic until the light is turned on. I've heard accounts of it being a similar situation with Cockatiels. --Kurt Shaped Box (talk) 23:59, 18 December 2010 (UTC)

"Hi. I was summoned..." From the vasty deep? 87.81.230.195 (talk) 12:39, 19 December 2010 (UTC)

December 19

Properties of liquid diamond

In recent news articles there's been mention of the possibility of diamond oceans at the centre of ice-giant planets like Neptune. What would it be like to travel as a submariner in such an ocean, assuming I had a magically strong bathysphere? What properties does liquid diamond have that would make the journey unique?

Sober discussion and wild speculation are both welcome.

Thanks Adambrowne666 (talk) 00:08, 19 December 2010 (UTC)

phase diagram of carbon. The liquid phase isn't really "diamond"

"Liquid diamond" cannot exist, given the type of bonding that exists in a diamond. Diamond is a "network solid" consisting of a single massive covalently bonded network of carbon atoms. In order to liquify, one would need to have discrete molecules of some sort, diamond just isn't organized that way. There could be liquid carbon, but it exists only at very high pressures and temperatures; under pressures less than 10 megapascals, (about 100x the pressure of Earth's atmosphere) it sublimes. Speaking of "liquid diamonds" is the fanciful sort of stuff you read in the science sections of newspapers, but such things don't really exist. --Jayron32 00:49, 19 December 2010 (UTC)

Yeah, good point; I didn't think of that. I suppose it's like calling water 'liquid ice'. I see here - carbon physics - that it's referred to as liquid carbon, as you say. Can we continue the discussion even so? Adambrowne666 (talk) 01:24, 19 December 2010 (UTC)

What do you want to discuss? The paper you just linked has a rather exhaustive and complete discussion of the properties of various phases of carbon. I am unclear what else you wish to learn... --Jayron32 01:29, 19 December 2010 (UTC)

Well, I think he was fairly clear the first time. He wants to know what it would be like to travel through it in a "magically strong bathysphere", and whether the answer would have to do with the medium's properties. I don't have any answer for that, but I don't see that it lacks sufficient specificity to be answered. --Trovatore (talk) 01:47, 19 December 2010 (UTC)

Jayron32: Not true, liquid diamond can exist - nanodiamonds. Consider dehydroadamantane, technically, the smalest molecular structure which can be called a diamond; an unsaturated carbon structure with delocalized lone electrons which, can have liquid properties under the right conditions. Think about it, a rock does not flow from a bucket, but crush it into fine silt, it flows freely from the bucket. It is not a true liquid, but it has similiar properties. I can't give you any properties of liquid dehydroadamantane, as no one has actually studied it, but I can tell you that it should behave as a highly reducing metallic liquid. Liquid diamond is a metastable substance, as it should irreversably polymerise into a hydrocarbon glass at STP. --Plasmic Physics (talk) 01:54, 19 December 2010 (UTC)

I don't see how you can call something diamond if it has (any significant amount of) hydrogen in it. Our article says dehydroadamantane is C₁₀H₁₄. --Trovatore (talk) 02:01, 19 December 2010 (UTC)

There are several degrees of unsaturation, C₁₀H₁₄ is not the most unsaturated adamanane frame. All diamonds have a "dirty" surface, covered by non-carbon groups. There is no formal cut-off ratio of carbon to other elements for molecule to be differenciated from a diamond, how many grains of sand makes a heap. The ratio can be simplified to a surface area to volume ratio. --Plasmic Physics (talk) 05:09, 19 December 2010 (UTC)

So, the question is now what it would be like to travel submerged through an ocean of liquid carbon. Anyone know if liquid carbon is opaque? It might just be very, very dark down there... WikiDao ☯ (talk) 18:12, 19 December 2010 (UTC)

I would guess that it would resemble graphite in its opacity. And at the high temperature it is at, it would be glowing white hot. Graeme Bartlett (talk) 03:23, 20 December 2010 (UTC)

Unlike movies, and cartoon representations, you can't see through magma or liquid diamond. Unlike magma, it would have a low viscocity and you should be able to move through it quite freely, given you have an undestructable bathysphere. --Plasmic Physics (talk) 08:40, 20 December 2010 (UTC)

Thanks everyone. I'm guessing you guys are right about the opacity etc of molten carbon. But I'd like to be sure. According to this paper carbon melt, the optical properties of molten carbon can be "calculated based on the Drude theory [9]. Using the standard relations for the dependence of the optical constants on the complex dielectric function, the reflectivity R(~o) normal to the surface and the absorption coefficient, c~(o~), can be calculated. See Table I for the values of ~(o) and R(o) for frequencies o3 of the pulsed lasers used to melt graphite. [1 ]" This is too technical for me. Is anyone here interested enough to look at the article and see if they can translate it for me? Also - if it is opaque, how would one navigate in it? Infrared? Sonar?

Halophiles

http://books.google.com/books?id=o8lOge_6TpsC&pg=PA101&dq=halophile+possibilities+for+industrial+process&hl=en&ei=NmYNTbaZG8L6lwfW16WeDA&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCYQ6AEwAA#v=onepage&q&f=false

(Under the header Extracellular Enzymes)

1. What does the term "Washing" mean?

2. How would halophilic enzymes be used in food processing?

3. (Page 103)

These compounds have industrial applications as stabilizers of enzymes, nucleic acids, membranes...

What would applications be that require for stabilizers of enzymes, membranes, etc.?

4. Reliable reference?

Thanks, Albacore (talk) 02:12, 19 December 2010 (UTC)

Your #1 and #2 seem straightforward to learn more detail, since the sentence gives you a citation for it:) Page 114 of your ref has a full bibliographic reference for the 2005 work by Ventosa. That author appears to have published extensively in the scientific journal world, so he's probably a reliable reference (but cf. #4, I don't know about the work you are reading that cites him). Also, the cites in the paragraph preceding the one you mention (main §5.4 intro) points to several other references that are described as in-depth reviews of these applications/fields (including an older one by the same Ventosa author). DMacks (talk) 04:37, 19 December 2010 (UTC)

Jet stream time lapse?

To understand how long-term changes in weather work, it would be very desirable to have some video showing the entire jet stream over the Northern Hemisphere, updated once a day, going on for at least a year, and preferably colorized as well with perhaps daytime high or average temperatures. Is anything like that in circulation? Can it exist, or is the jet stream too abstract to actually be placed on a map consistently in this way using data from multiple authorities? Wnt (talk) 05:23, 19 December 2010 (UTC)

Here are animated northern hemisphere jet stream maps with data available back to 2006. Red Act (talk) 06:17, 19 December 2010 (UTC)

networking

concept of bridge,switch and router plz help me some one....... sand mass. — Preceding unsigned comment added by Satraj2010 (talk • contribs) 07:53, 19 December 2010 (UTC)

Please see Routing, Bridging (networking), Network switch, and Router. Further questions might be better suited to the Computing Desk. Ginger Conspiracy (talk) 08:00, 19 December 2010 (UTC)

I've redacted the e-mail address per policy. shoy (reactions) 17:42, 20 December 2010 (UTC)

physics

in a structure of an atom protons are positively charged then why dont they repel each other as every positive charge repel positive charge? —Preceding unsigned comment added by 218.248.64.182 (talk) 12:25, 19 December 2010 (UTC)

According to Atomic nucleus#Forces, The nuclear force is highly attractive at very small distances, and this overwhelms the repulsion between protons which is due to the electromagnetic force, thus allowing nuclei to exist. 90.195.179.14 (talk) 12:34, 19 December 2010 (UTC)

The nuclear force is actually repulsive at very close range, but becomes attractive at typical distances between particles in the nucleus. The comparison with electrostatic repulsion is shown here. If a proton ever gains enough energy to separate from its neighbours by three times its normal distance, then the charge repulsion will take over and the proton will leave the nucleus. Dbfirs 12:56, 19 December 2010 (UTC)

There are two forces at work at the size of the atom. One is the electromagnetic force you are talking about, where like-repels-like. But at shorter ranges, the nuclear force is strong, where nucleon-attracts-nucleon. So protons are attracted to protons and neutrons. Note that you had too many protons in a nucleus without neutrons, you could overwhelm the nuclear force — the electromagnetic force would be too powerful. This is why nuclei require large numbers of neutrons (which are electromagnetically neutral) to balance it out and be more stable. You can get an idea of how much "balancing" is required when you look at uranium. With 92 protons and 146 neutrons, U-238 has a half-life of 4.468×10⁹ years — a very long time! Remove just six of those neutrons and you have U-232, which has a half-life of only 68.9 years — much less stable. So you can think of the inside of a nucleus as a battle between two contradictory forces. This helps to explain why nuclear fission requires big, not-very-stable nuclei, and why nuclear fusion, even of atoms with very minimal positive charges, is very hard to accomplish. Fission is an example of when the electromagnetic force overwhelms the nuclear force (because of being jostled by an extra neutron, usually); fusion is an example of the nuclear force overcoming the repulsion of the electromagnetic force. --Mr.98 (talk) 20:46, 19 December 2010 (UTC)

But removing protons or adding neutrons will also destabilize a stable nucleus. And nuclei with an even number of protons and neutrons are generally much more stable than otherwise similar nuclei with an odd number of protons and neutrons. And 68.9 years is an incredibly long time compared to the time scale of typical nuclear or chemical reactions (nanoseconds or less). Electromagnetic repulsion has some role in stability, but it's a lot more complicated than that. -- BenRG (talk) 09:03, 20 December 2010 (UTC)

A strong counter-example to Mr.98's idea of "enough neutrons to keep the protons from getting too repulsive, but an extra few would destabilize" is elements that do not have a "stability plateau" at a certain number of nucleons. Chlorine, for example, ³⁵
₁₇Cl and ³⁷
₁₇Cl are stable, whereas ³⁶
₁₇Cl decays. Now, Cl-36 is still fairly stable as far as nuclei go (half-life is 308000 years), but it seems contradictory from the simple pattern that if you take a stable and add (or remove, depending whether you start with Cl-35 or Cl-37) you get unstable and then if you do more of that same destabilizing change, you become...stable again. And the unstable isotope decays

³⁶
₁₇Cl→³⁶
₁₈Ar so taking unstable and adding even more charge but not more particles (net fraction of neutrons decreases!) gives you...stable argon. The idea of parity solves a lot of these (looks like "even number of neutrons" is the key?), but then sulfur is stable as ³²
₁₆S, ³³
₁₆S, ³⁴
₁₆S, ³⁶
₁₆S. Nuclei really only obey "the whole set of rules" (and we're only describing reality with rules that are based on it, we can't tell Nature what to do:), not any one in isolation. DMacks (talk) 14:45, 20 December 2010 (UTC)

Science and God

Has science absolutely proven that God cannot exist? I know for a fact that the big bang theory does not, since no one can say where the material for it came from. But what about life? The Primordial soup could have resulted in forming organic molecules, but could they combine or react to form living cells? Thanks. --119.155.7.74 (talk) 13:59, 19 December 2010 (UTC)

Absolutely not. Relationship between religion and science appears to give an overview of the issues. Clarityfiend (talk) 14:25, 19 December 2010 (UTC)

Your question betrays a logical error. You ask whether the primordial soup could have produced living cells. Suppose we knew of no way in which this could happen: I suppose you could use this as some kind of evidence for the existence of God. In fact we do know of ways in which this may happen. But this is not evidence for the non-existence of God at all; rather it's a lack of one potential piece of evidence. It's certainly not having "absolutely proven that God cannot exist". (But then of course you have Occam's razor to think about.) May I recommend our article on the conflict thesis? Marnanel (talk) 14:39, 19 December 2010 (UTC)

Science doesn't absolutely prove anything. Science is all about trying to find the simplest theory that accurately explains our observations. Theorising the existence of a supreme being doesn't explain any observations that can't be explained without a supreme being (at least, not enough to make up for the fact that you now need to explain the existence of the supreme being - it's one step forward and two steps backwards). Just because theories without supreme beings are simpler than theories with and explain our observations just as well doesn't mean they are right, but it tends to work well to assume the simpler theory is the correct one (this is Occam's razor).

It's a little different if you ask about a specific God. Science can disprove (beyond all reasonable doubt, at least) all sorts of claims made in the Bible, for example. It just can't disprove the existence of supreme beings in general. --Tango (talk) 14:47, 19 December 2010 (UTC)

So science doesn't deny the existence of God, but sidelines it as an unlikely explanation of the universe? Am I right? --119.155.7.74 (talk) 15:35, 19 December 2010 (UTC)

Science makes no claims about the existence or lack thereof of god/gods. Like Tango said it does contradict many parts of various holy books, Genesis being an obvious example. The modern conception of divinity is that it operates supernaturally and thus cannot be quantified. Science by definition deals with the natural world and cannot determine things about the (supposed) supernatural. The origin of the universe (pre big bang) and of life is something that science has yet to produce firm answers for but that does little to prove or disprove the existence of god. On the other hand the "supernatural" is often used to explain things we don't understand. People used to think gods controlled many natural processes (like the weather) and as our understanding of the world expanded they were forced into ever smaller gaps in understanding. See God of the gaps. --Leivick (talk) 16:00, 19 December 2010 (UTC)

You could say that science "sidelines" the existence of God as "Unevidenced". Which is the same category alien abductions and ghost stories wind up in, but also some reasonably scientific theories like Panspermia. APL (talk) 19:16, 19 December 2010 (UTC)

I do understand the concept of God of the gaps. But can science go beyond the big bang? From Stephen Hawking's book 'A brief history of time', and from being a physics student myself, I perfectly understand the aim of almost all physicists in deriving the one single unified theory, but that too would only explain events after the big bang, since all laws break down at the big bang itself. So how can science try to understand events before that? I am not trying to imply that God did indeed make the universe, but just asking if science will be able to explain events before the big bang. --119.155.7.74 (talk) 17:26, 19 December 2010 (UTC)

I think every honest scientist will acknowledge that an omnipotent God could in principle have faked all the evidence we see, of evolution and everything else. Even creationists, for some reason, are not eager to back that idea, but there is certainly no way to rule it out scientifically. Looie496 (talk) 17:36, 19 December 2010 (UTC)

(ec) So science doesn't deny the existence of God, but sidelines it as an unlikely explanation of the universe? Am I right? - As stated above, science could never either prove or disprove the existence of God, so, no, science does not deny the existence of God, nor does it sideline it as an unlikely explanation of the universe. But certain scientists are more than happy to do these things. They trumpet their personal opinions as "the truth" and "science". It's a very human thing to do; after all, even scientists have egos. -- Jack of Oz ... speak! ... 17:38, 19 December 2010 (UTC)

For interest, just in case you missed it, there was this recently ( ...and this) along with numerous media reports.....and a wiki article, Conformal Cyclic Cosmology. Sean.hoyland - talk 17:58, 19 December 2010 (UTC)

The information provided in the first link exceeds my understanding of physics :P. However, after reading the first few lines of the Wikipedia article on CCC, I gather that a universe apparently 'dies' and gives birth to a new one. That still doesn't explain where the matter for the first one of this kind of universe could have come from. --119.155.7.74 (talk) 18:15, 19 December 2010 (UTC)

Note that even if science can't go beyond the Big Bang (which is not clear, in any case), it doesn't make "God did it" a very good answer from a scientific perspective. There may be epistemological limits to science. Putting God into those blank spaces is not a logical conclusion. I do not know what my mother is doing this very moment. That doesn't make it logical for me to assume she is eating a cake, or dancing ballet, or trying on hats, even if a very respected book asserts with the deepest solemnity that this is most certainly what she is doing. Hitting a limit on knowledge does not logically authorize an appeal to divine inspiration. --Mr.98 (talk) 18:16, 19 December 2010 (UTC)

I guess the matter for the first one came from the same place that produced the first god. :) Sean.hoyland - talk 18:25, 19 December 2010 (UTC)

Right, OP, saying "God" is not a very robust explanation of anything, even if it were to be in some sense ultimately "correct". Science is interested in understanding better how things actually work, in detail and in the actual world. Just shrugging and saying "God did it" isn't very useful to Science, but nothing about Science itself prevents individual scientists from saying that, or something similar, from time-to-time, if they want. ;) WikiDao ☯ (talk) 18:23, 19 December 2010 (UTC)

I know that saying 'God did it' is just plain arrogant, but will somewhere down the line science eventually come to a halt, when it can no longer explain some event or events, when saying 'God did it' might not be so arrogant? --119.155.7.74 (talk) 18:57, 19 December 2010 (UTC)

Science comes to a halt on a regular basis, see eg. List of unsolved problems in physics. But the whole purpose of Science is to persist in trying to understand the workings of the actual world as well as possible. Vaguely invoking "God" as an explanation for how things work is never useful for that purpose. But note again that that is not the same as saying conclusively "God does not exist." Science does not say that, it just ignores that question altogether as irrelevant. WikiDao ☯ (talk) 19:11, 19 December 2010 (UTC)

Which god? You mean Odin, right? Or Zeus? Quetzalcoatl, perhaps? Or simply a god beyond all current human knowledge? Without evidence for one over the other a scientist should not name (or imply) a specific god.

Anyway, it's "arrogant" because without evidence you're just guessing. You don't need to be a scientist to guess. Any scientist that said "I personally can't think of an answer, so it must be unknowable, and therefore must be The Flying Spaghetti Monster." would be more than arrogant, he'd be missing the point. Better for him to say "I can't figure this out, maybe someone else can." APL (talk) 19:14, 19 December 2010 (UTC)

Well, i can honestly say that after this discussion my faith in God and my love for science has only increased. Thanks to everyone for contributing. And on that note, what books would you suggest which are similar to 'A Brief History of Time', not too complex and which can slowly introduce me to higher level of this study. Note that I study this alone in my spare time, as a hobby. Thanks. --119.155.7.74 (talk) 20:16, 19 December 2010 (UTC)

You might be interested in "God: The Failed Hypothesis" by Victor J. Stenger. The author argues that science can indeed have a say in the question of whether God exists. One of the first things he does is to make a distinction between the god (little g) of Deism and Pantheism and the Judeo-Christian-Islamic God (capital G). The former is what people probably think of when they say science ignores the question of "God". This is essentially the idea of Non-overlapping magisteria. But Victor argues that the latter assumes a God which actually plays an important part in the universe and therefore should be detectable by the methods of science. We can't prove "quarks" we can however test the model of the universe which their existence implies, we should in the same way be able to test the model of the universe which the existence of God (capital G) implies. In the same way that science can not disprove the existence of unicorns or dragons, we can after careful investigation, with a certain level of certainty give an opinion on their likelihood. Vespine (talk) 22:28, 19 December 2010 (UTC)

I agree, and well-stated. I don't mean to be saying above that "the existence of God", carefully defined, should not be an object of scientific investigation. And that existence or not, carefully defined, might have some relevance to other areas of scientific investigation at some point. At this point, though, and again see eg. List of unsolved problems in physics, the whole question seems mostly irrelevant to the other questions science is asking. WikiDao ☯ (talk) 22:46, 19 December 2010 (UTC)

Science as a whole must remain strictly agnostic on subjects such as omniscient, omnipotent beings like God who choose not to reveal themselves in a verifiable manner. Their existence is not a testable hypothesis by definition. However, many scientists choose to identify as atheists, because of the damage religious mythology (such as the 6,000 year age of the Earth implied by Judeo-Christian-Islamic doctrine) do to the fields of biochemistry, radiochemistry, astronomy, geology, paleontology, archeology and other fields in which empirical evidence implies a very much older Earth. This damage manifests as anti-vaccination and similar movements skeptical of medical science, for example. Similarly, many ethicists are skeptical of basing systems of morality on the threat of eternal torture in hell as punishment for wrongdoing, or the idea that an ethnically superior people have been chosen by God to deserve advantages such as the right to rule over others. Many are revolted by the endorsement of slavery which occurs in almost all the ancient religious texts of the world. On the other hand, anthropologists can explain why the many diverse cultures of the world might have come to embrace religions; for example to reinforce social hierarchies, hygiene, and social order in the absence of secular institutions to do so. Ginger Conspiracy (talk) 03:54, 20 December 2010 (UTC)

I sometimes wonder about an innocent child, given a scientific explanation for everything from birth, or at least the time of verbal awareness, and never exposed to religious views. Would such a child invent religion for themselves? HiLo48 (talk) 04:08, 20 December 2010 (UTC)

It's possible. "There are no atheists in foxholes" as the saying goes, meaning that belief in the supernatural is associated with imminent danger. Religious faith is defined in terms of doubt, after all. But in my estimation, the agnostics have a far more consistent position than athiests. For example, a loving creator of hominids may not want to reveal itself for the same reason that loving parents want their children to be able to support themselves independently. Ginger Conspiracy (talk) 04:12, 20 December 2010 (UTC)

Yeah, but that hypothetical, loving creator of hominids has consequently created a heck of a lot of confusion along the way. HiLo48 (talk) 04:27, 20 December 2010 (UTC)

Well, I'm not a perfect example (as I was attending mass at least once a week at the time), but my parents apparently neglected to mention or explain to me anything about our religion for the first few years of my life, and I distinctly remember believing in reincarnation (not using that word, because nobody had ever mentioned it to me), and even discussing it with my playgroup friends, all before I started school. My parents had encouraged logical thinking, investigation, and a love of knowledge of the world: I'd done experiments with growing beans, and so on, so certainly they had worked to instill a certain amount of scientific reasoning. Once people started actually explaining my religion to me, I got terribly confused and somehow thought girls became angels and boys became devils, when they died. I would definitely say, from my own experience, that the absence of religious indoctrination in many people does not lead to an absence of religious belief. 86.163.0.221 (talk) 15:43, 20 December 2010 (UTC)

No, I'm hypothesising a far more extreme situation. One where religion doesn't exist in the world of the child as it grows up. While you may not have been indoctrinated, you were surrounded by stories of mystical beings that other people took seriously as creators and destroyers, etc. If the child could be totally removed from that environment, but given everything science has to offer, would they need to invent religion? HiLo48 (talk) 00:16, 21 December 2010 (UTC)

I dont know about Christianity or Judaism, but Islam does not state the age of Earth as 6000 years. It doesn't imply any specific date for the creation of the Earth. I understand that science will not benefit from keeping God as a possible explanation for any events that it cannot explain as yet. What I meant by my original question was if or not so far the discoveries made by science have in any way removed, beyond all doubt, the idea of God. The answer to that is clearly no, since science is not trying to prove anything, rather just studying and understanding more of how the universe works. What conclusions people draw from those studies regarding God is up to them. --119.155.31.74 (talk) 05:08, 20 December 2010 (UTC)

Sadly, Islamic scholars are endorsing Young Earth creationism myths more often these days, especially in Turkey, although Muslims were early proponents of evolution. See Tawrat and Islamic creationism. Ginger Conspiracy (talk) 11:47, 20 December 2010 (UTC)

I generally disagree with the conclusion: What conclusions people draw from those studies regarding God is up to them.. Substitute God for "gravity", or "heliocentricity", or "evolution". I also disagree with Science as a whole must remain strictly agnostic …… not to reveal themselves in a verifiable manner . "The God" of the main theisms isn't a God of "the background" who never reveals himself, that's mutually exclusive, and Science can have an opinion on that. Vespine (talk) 22:09, 20 December 2010 (UTC)

It's been said that science is questions that may never be answered, and religion answers that may never be questioned. There are some things in every religion that the vast majority of adherents will never dare to question honestly. 66.108.223.179 (talk) 02:01, 21 December 2010 (UTC)

If science as a whole doesn't try to understand God as it is something supernatural and not beneficial to it, how can it have an opinion on God? It is scientists that individually have their own opinions. Ive never read or heard anywhere science coming to a conclusion regarding the existence of God. --119.155.112.106 (talk) 05:09, 21 December 2010 (UTC)

"If science as a whole doesn't try to understand God" Since when?, there are lots and lots of scientists that challenge claims made about God in the bible and other holy books. Richard Dawkins is one that comes instantly to mind. It is a fallacy to assume that science is somehow "prohibited" from observing or explaining something supernatural. Yes we always look for a natural explanation, but that's only because in the course of all human history, nothing supernatural has ever been empirically observed. If we did legitimately observe supernatural phenomena, then science would accept it and study it in as great a detail as possible. This would lead to whole new fields of study and no doubt lead to big public research grants, it would be a massive boon to scientists, most scientists would welcome it not fear it. I've never read or heard anywhere science coming to a conclusion regarding the existence of God. Well then I can only assume you haven't looked in the right places. I already linked God: The Failed Hypothesis above, and The God Delusion is Dawkins' contribution, two books fairly recently written about God from a scientific perspective. No these aren't "peer reviewed articles in scientific journals", but then you won't find peer reviewed scientific articles about the evidence for the non existence of unicorns either. Doesn't mean you can't come to a scientific conclusion about the likelihood of unicorns. Vespine (talk) 23:18, 21 December 2010 (UTC)

The article on 'God: The Failed Hypothesis' says that the author concludes that the existence of God is not impossible, only improbable. Those scientists usually challenge the claims of holy books after being masters of their profession, when they feel they have enough knowledge to scientifically challenge the question of God's existence and have scientific proof to back it. In the end, all that I can conclude is that science so far has only enough data to label it improbable. --116.71.62.183 (talk) 05:13, 22 December 2010 (UTC)

sigh Yes, because that's what science does. As stated above more then once, science does not absolutely prove, nor disprove ANYTHING, it just gives varying degrees of probability which asymptote towards certainty, but never actually reach it. NOTHING in science is beyond question, that's what makes it different from religion. Vespine (talk) 05:45, 22 December 2010 (UTC)

Degeneration Redux

Because of medical treatment in prolonging life, inheritable susceptibility to disease will expand at an increasing rate. This increasing growth rate would be exacerbated by the following medical advances:

1. Medical science would further prolong the life of these patients, permitting them to have more children.

2 Medical science might find that more diseases can have inheritable susceptibility.

Perhaps the growth rate of the number of these patients could become very steep, perhaps something like an exponential curve. That would eventually make the burden of supporting and treating these patients intolerable, and force action about the birth of such persons.

The great loss of life of native Americans due to “European” diseases shows how susceptibility to disease can be widespread. Modern medicine was not available to save the native Americans. But now susceptible people can live on and beget children who are also susceptible. - Diatom. 173.189.136.110 (talk) 15:27, 19 December 2010 (UTC)

You just repeat the assertions that were already discussed and refuted above. Do you have a question? --Stephan Schulz (talk) 16:11, 19 December 2010 (UTC)

I have been repetitive because people are not responding directly to what I say. For instance, there is the question of how long it would take for the problem to become serious. So I expanded on that point in my last post. Also, I don't think I have been refuted. Diatom. 173.189.136.110 (talk) 16:36, 19 December 2010 (UTC)

No one can say 'how long it would take for the problem to become serious' because 1) None of us has a crystal ball, or if anyone does, they've never shared it with us (I'm not aware any of us are billionares which you would expect if we had access to one) 2) Given the major changes in social structure and major advances in biotechnology trying to predict what will happen in 50 years is problematic in itself let alone 300 years. 3) The problem and 'become serious' aren't really defined in a way that any meaningful predictions can be made even if we tried. (In particular, it's question whether there is any problem that will become serious.) Nil Einne (talk) 17:44, 19 December 2010 (UTC)

We can say that the statistics of globally increasing lifespans, decreasing infant mortality, and leveling population growth rates after decades of mass intercontinental air travel seem to imply that most of what were only decades ago thought to be the most difficult hurdles have been cleared. In the 1960s, for example, there were few reasons not to believe that the human population would dangerously exceed the planet's carrying capacity by now. What has actually happened, however, is astonishingly optimistic in comparison. There is still a lot of suffering, but as a proportion of human experience it is decreasing more rapidly than ever. The character of diseases which have been emerging don't rule out the possibility of another substantial human plague, but the probability does seem to be decreasing. I recommend Doctors without Borders epidemiologist Hans Rosling's interactive Gapminder statistics browser and his TED lectures using it.[10][11][12][13][14] Ginger Conspiracy (talk) 04:35, 20 December 2010 (UTC)

Ginger, thanks for the interesting and informative leads. There's lots and lots of goo information there. Diatom.173.189.136.110 (talk) 14:39, 20 December 2010 (UTC)

It has been suggested that gene modification could be a solution to the problem of inherited susceptibility to disease in human beings. However, I don’t think GM people are a good idea. First of all, In view of the opposition to GM crops, there would be very great public opposition to creating GM people. There might be prejudice against GM people if they were created. Perhaps they would be jeered at as "Frankensteins". Their children would be taunted at school as "The Son of Frankenstein".

Secondly, it would start off with a beneficial purpose – the elimination of disease susceptibility. Then people would want their offspring to be gene-modified in other ways, such as to be super-intelligent boys or super sports figures, or very beautiful girls. There would undoubtedly be doctors prepared to do that for a price. It would also take a more sinister turn. Some would want their son to be very greedy and hence a great moneymaker (very “successful”). Dictators would want to create super soldiers who would be very aggressive, ruthless, and fearless. Another suggestion was to use amniocyntesis to detect disease prone fetuses. That is a much better idea if the procedure can be done early enough to permit legal abortion. It is being done now to detect fetuses that will be born with serious birth defects. It could be extended to fetuses that would apparently be normal at birth, but that would be susceptible to a certain disease later in life. – Diatom. 173.189.136.110 (talk) 16:15, 19 December 2010 (UTC)

What's the question there? Note that your personal dislike of genetic modification or using amniocentesis is somewhat besides the point. If it happens it happens whether you personally like it or not and it majorly screws up any predictions you try to make of the future. Nil Einne (talk) 17:30, 19 December 2010 (UTC)

I think in general the main difficulty with your line of argument here is that you seem to treat genetic susceptibility as some kind of rigid determination. It's generally not. If I had your DNA in hand today, I could tell you that you had some markers which gave you a certain risk factor of being susceptible to tuberculosis, breast cancer, prostate cancer, and Alzheimer's. I could probably not tell you for certain whether any of those things would develop. (In some rare cases, where the single mutation is the cause of the disease, I could do that. But those are the exception.) So should I let you reproduce? You tell me. What's the cutoff point? 50%? 60%? 80%? Does it matter if all of those things become easily treatable in the future? None of these issues are simple from either a medical or a social view.

The other major difficulty is that you vastly overestimate the importance of these kinds of things on the health expenditure of the world. Exotic diseases make up a very small part of our world's woes. Banal things related to public health and socio-economic conditions consume the vast majority of our resources. Sterilization programs will not have any impact on these matters. You would save more money by banning fast food and cigarettes than you would through any kind of eugenics program, and with a significant decrease in the ethical, legal, and social quandaries. (This is just an aside, but I find it odd how most of those who I have met these days who are in favor of heavy-handed state measures like eugenics are usually not inclined to take heavy-handed state measures in other realms of public health or the economy. This was, of course, not the case with the Germans, who were heavy-handed all around.) --Mr.98 (talk) 18:33, 19 December 2010 (UTC)

The measures I am suggesting would be taken only when the burden of supporting and treating susceptible patients becomes intolerable. When that point is reached, there will be no point discussing whether it will be done. Public opinion will insist on it. Some members of the public will not want to take action, so there will need to be at least a majority in favor of it. With the situation getting worse all the time, the no-action people will gradually shift to the other camp.

The situation would be taken on a disease by disease basis. Diseases which are not yet a serious problem would need no action.

Also, if personal susceptibility varies for a particular disease, and that can be measured, that would be taken into consideration. The cutoff point for each individual would have to be decided on somewhere of necessity and would be based on his percentage of susceptibility

If an easy, low cost treatment or cure for a disease is developed after a person has been sterilized, he will simply be out of luck. The sterilization program cannot be delayed in the hope that low cost treatment or a cure will be found. Necessity will not allow delay.

Growing disease susceptibility is one of a number of dire situations that can be seen ahead for the human race, and that will need heavy-handed government action if the human race is to survive. Diatom173.189.136.110 (talk) 21:52, 19 December 2010 (UTC)

Diatom. You need to re-read Mr.98's post, which is spot-on. Your understanding of the genetic underpinnings of disease is incomplete and simplistic, which is causing you to make assertions that are false. Your predictions about the need for (and inevitability of) governmental sterilization programs are naive and misplaced... the human race has far greater problems to face in the near future, global warming among them. --- Medical geneticist (talk) 23:21, 19 December 2010 (UTC)

If a person has no children, he will not pass on a harmful inheritable genetic trait. It does not take a geneticist to see that. Diatom. 173.189.136.110 (talk) 05:42, 20 December 2010 (UTC)

Stephen Hawking's condition is a genetic one. He has benefited a lot from medical help. Screening his parents or even him as a foetus could probably these days prevent people like him being born and the subsequent load on society. But then we wouldn't have had Stephen Hawking. HiLo48 (talk) 00:04, 20 December 2010 (UTC)

I will have to say again that I am talking about a situation that has reached an extreme state. Conditions will have to be like the great plagues that swept Europe in the Middle Ages. As I have said, the growth of disease susceptibility may be somewhat like a geometric progression, bringing dire conditions sooner than might be expected. Yes, geniuses will not be born if their parent is made sterile. But the same can be said about present legal abortion. In order that a parent will not have the bother and expense of raising a child, millions of fetuses have been destroyed. That undoubtedly included many geniuses. The same can be said about potential parents who die in war. Diatom.173.189.136.110 (talk) ~ —Preceding unsigned comment added by 173.189.136.110 (talk) 05:20, 20 December 2010 (UTC)

Well, if we're going to keep on with this speculation, I might as well voice my own crank opinion - which is that genetic degradation doesn't matter, not just for the conventional reason that people can fix the damage with genetic manipulation, nor the more macabre expectation that humanity may not survive long enough for it to matter, but because of a third factor, relating back to how our human race came to be. Homo sapiens burst forth in a wave from Africa, supplanting its predecessor almost entirely, as has happened, it would appear, for wave after wave of human races before it. The cradle of mankind, sensu lato, where its genetic diversity is maintained in full in the context of its native environment, remains the only place where this diversity remains, and thus remains the most likely place for any fresh wave of newly adapted humans to emerge. Thus races of men like the Twa, combining the full power of the human mind with a more efficient body, expressing the full range of human genetic diversity, and already displaying a great deal of reproductive isolation, await only the implementation of interstellar travel to evolve and emerge as Homo apotelesmatis, as I would dub them, and to begin an inevitable, exponential growth beyond all the humans that have ever come before them. Wnt (talk) 06:18, 20 December 2010 (UTC)

The point you are missing is that it will never reach an extreme state. In a large, well-mixed population, genes that are neither selected for nor selected against tend to maintain a roughly constant frequency over time. They do not proliferate. This is not like a geometric progression at all. In a natural setting, negative genes are selected against and a human population would be expected to get "healthier" over time (though the history of any particular gene is strongly influenced by random fluctuations and founder effects in small subpopulations). Medical intervention can plausibly remove the negative pressure in many cases. This prevents evolutionary pressure from making us "healthier" over time, but it doesn't inherently provide any selective advantage to the negative traits. Hence the "healthiness" of the human population would stop evolving and remain roughly constant. Dragons flight (talk) 06:35, 20 December 2010 (UTC)

I will have to repeat what I have already said 3 or 4 times. Medical treatment can often extend the life span of persons with inheritable susceptibility to disease. As a result, these persons beget more children who will also have the problem. Thus, the proportion of these people in the population continually increases. That sort of thing is a geometric progression. Also, advances in medical science can be expected to give these people even longer life, exacerbating the problem.

Thus, because of medical intervention the positive and negative factors do not remain in balance. Diatom.173.189.136.110 (talk) 13:54, 20 December 2010 (UTC)

Your understanding of the nature of genetic conditions is pre-Mendelian, much less post-Mendelian. You don't seem to get that screening out the phenotype does not screen out the genotype, and that trying to screen out the genotype means screening out people who are phenotypically healthy. You don't seem to get that most genetic conditions are not simple Mendelian traits anyway and can't be determined with anything more than a probabilistic assessment. You don't seem to get that the catastrophes you fear are probably not going to happen, ever, and that the present and future medical problems of the human race are quite different from them. You don't seem to understand the Hardy-Weinberg principle, which is key to understanding how genes proliferate in a population.

Your ignorance of even the fundamental concepts of genetics is going to impede you from actually having informed discussion on this topic. I think everyone in this thread and the previous has tried to point out exactly where you ignorance lies, but you've stubbornly resisted assimilating new information. I'm not sure the Reference Desk is going to be able to help you with your inquiries if you aren't actually going to take the time to really understand our responses. I'd like to help, but you don't seem eager to listen, and the Reference Desk is neither a debate society nor a place to arbitrarily air your views. --Mr.98 (talk) 14:47, 20 December 2010 (UTC)

(EC with below) This is probably a bit futile but I'm not sure if anyone has mentioned this yet. "Also, advances in medical science can be expected to give these people even longer life, exacerbating the problem." - this is a confusing statement. Once someone is no longer able to breed (have children) 'exacerbating this problem' is far from clear cut. (Of course the concept of unable to have children can be somewhat fussy nowadays even for females. However I mention this for a reason in that most people even with some susceptibility to various cancers, degenerative brain disorders etc tend to only tend to get cancer after they've had all their kids.) Humans do have a long adolescence and even in adulthood there is an advantage to having living parents as well as even living grandparents. But with the increasing level of social care etc there's likely to be less of an advantage, furthermore there are things like the cost of medical care etc for the living longer, particularly in societies where there is strong expectations of children helping their parents when they are elderly which complicate any advantage of this living longer to the children. Also you may next criticise the trend of delaying reproduction but note that AFAIK there is a fair amount of evidence that in other animals delaying reproduction tends to increase the average lifespan (of course this is unlikely to be very clear cut in humans given my earlier point about fussy reproductive ages as well as all the points me and others have made earlier)... Nil Einne (talk) 16:39, 20 December 2010 (UTC)

Medical advances that allow someone with a negative genetic condition to live a normal life span (and procreate normally) will mean that the genes are no longer selected against. It does not however mean that these genes will magically proliferate. You've repeated the same fallacy several times, but repetition does not magically make your point true. Consider the case of a simple recessive genetic condition caused by a single gene. Let's label the healthy, dominant gene as type "X" and disease causing recessive gene as type "x". Further, let's arbitrarily say that at an initial time 10% of genes are type "x", and 90% are the healthy type "X". A simple Mendelian cross tells us that of all babies born 81% will be type "XX" (completely healthy), 18% will be type "Xx" (disease carriers), and 1% will be type "xx" (disease victims). If all the disease victims are eliminated, then the gene pool in the next generation becomes 90.91% type "X" and 9.09% type "x". This is the natural effect of a deleterious gene being selected against. On the other hand, if medical intervention saves all of the "xx" people and allows them to live and procreate normally, then the next generation of the gene pool becomes... 90% type "X" and 10% type "x", exactly the same as it was before medical intervention. Your assertions to the contrary are simply wrong. If healthy and sickly people are given an equal opportunity to procreate, then their genes will maintain a constant relative abundance in the gene pool. Under ordinary processes, evolution works to eliminate deleterious genes. Medical interventions can arrest that process, and prevent negative genes from being eliminated, but it takes more than that for a gene to proliferate in the gene pool. In order for type "x" to become more common, there must be some reason that people having it are even more likely to procreate than people with type "X" genes. Giving them an equal shot at life simply isn't enough to do anything other than maintain the genetic status quo. Dragons flight (talk) 16:17, 20 December 2010 (UTC)

This is a zero-order approximation, but an overly optimistic picture, since random mutations accumulate in the genome. In the past, a 20-year generation cycle of humans, with occasional deaths from genetic factors, was sufficient to remove these mutations at the same rate as they occurred. The point that other participants made is that without this cycle, they will accumulate. I should note that the delay in the age at reproduction itself is sufficient to increase the mutation burden (especially in men, since oocytes undergo a dictyate arrest that prevents nucleic acid changes; conditions like Down syndrome associated with old eggs involve such large chunks of misplaced chromosome that modern medicine doesn't really keep them in the gene pool). And let's not even start on the extra problems that come up when representatives of the international idiot community decide to repeatedly nuke their own country or shut off all a reactor's safety precautions to see if they're truly necessary... As a side issue, certain genes subject to triplet repeat expansion (causing trinucleotide repeat disorders) actually become more vulnerable to severe mutations when milder mutations persist. More importantly (I think) there are proteins such as helicases which when mutated can lead to increased overall mutation rates. I am not advocating some kind of eugenic solution here - among other good reasons, "turning up natural selection and making it twice as effective" really is not an easy thing to do, no matter how smart the selector thinks he is - but recognize that the problem is a real one. Wnt (talk) 16:30, 21 December 2010 (UTC)

OK everybody. Thanks for all the input. There's more to it than I thought. My education in science ended at the age of 13, except for electronics training in the Air Force. But at least give me credit for the original thought about medical intervention in the situation. Diatom. 173.189.136.110 (talk) 22:50, 21 December 2010 (UTC)

Megapnosaurus name meaning

It's me again. Except with a theropod question this time, which is actually quite simple:

Why the heck does Megapnosaurus mean "big dead lizard?" It's not especially big, and they're all dead (except for the birds of course :D)...Crimsonraptor (talk) 15:30, 19 December 2010 (UTC)

Well, it means that because that's how the Greek translates. But I suspect you don't want to know that, but rather know why that name was chosen. All I can say is that Palaeontologists have a weird sense of humor... --Stephan Schulz (talk) 16:18, 19 December 2010 (UTC)

They have weird senses of humor alright. Take Colepiocephale. I looked it up one day and it said the genus name (from Greek) meant "knuckle head." What makes it more funny is that it actually makes sense: it's a pachycephalosaur. Crimsonraptor (talk) 18:05, 19 December 2010 (UTC)

Unusual Vision?

This is a medical question, but not a question for medical advice. Whenever I look through my right eye only, everything appears slightly reddish. When I look through my left eye only, everything appears slightly bluish. With both eyes open, everything appears to be its normal color. What explains the differences in my vision?24.88.86.197 (talk) 18:02, 19 December 2010 (UTC)

I assume it's not these. Sean.hoyland - talk 18:33, 19 December 2010 (UTC)

I have the same situation as the OP. My eyes see slightly different colors. My right eye sees a little redder and my left a little bluer. I had always assumed this wasn't a pathogenic problem, merely a result of subtle variation between the distribution of Cone cells in each eye. It's a situation I have always been curious about, but have never asked about myself... --Jayron32 18:50, 19 December 2010 (UTC)

I have something similar and came to a similar conclusion as Jayron. I've looked in to it briefly before but never really found anything useful. Also asked an optometrist once (during an eye examination although this was a student optometrist at the University of Auckland optometry clinic) but they didn't seem to be sure what I was asking about and it didn't bother me (I was simply asking out of curiosity) and I suspected they wouldn't know so didn't really try to explain. Nil Einne (talk) 19:06, 19 December 2010 (UTC)

Yes, I've noticed a similar effect, but only very slight, and it seems to vary. I've put it down to a difference in blood flow, but perhaps someone somewhere has done some research, or maybe an expert might have an informed opinion. The condition seems to be common, so it wouldn't be medical advice. I have also wondered whether it might be just a difference in the way the brain processes the two sets of three signals, rather like two identical photographic films, exposed identically, but being processed side-by-side with slightly different chemicals (pre-digital). There would be nothing wrong with either film or its exposure, just a matter of opinion about which colour development looked best, so perhaps there is nothing "wrong" with either eye. Apologies for the speculation, but it is well-known that colour is "seen" in the brain, and the eye doesn't combine signals. Dbfirs 20:56, 19 December 2010 (UTC)

Cerebral achromatopsia "is a type of color-blindness that is caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye's retina".

Color blindness, or color vision deficiency, "is the decreased ability to perceive differences between some of the colors that others can distinguish. It is most often of genetic nature, but may also occur because of some eye, nerve, or brain damage, or exposure to certain chemicals."

I'm not sure what is going on with differences between the color vision of one eye and the other, but would recommend getting a professional vision test for those that have it. WikiDao ☯ (talk) 21:20, 19 December 2010 (UTC)

Except that it isn't color blindness, which is an inability to distinguish different colors, such as being presented with two pictures, one red and the other green, and being unable to tell which is red and which is green. This is not that at all. It's just a slight difference in color perception between each eye. None of us has any trouble identifying colors. --Jayron32 21:25, 19 December 2010 (UTC)

After reading a bit about colour perception, I think my analogy of chemical processing might be closer to the truth than I realised. The cones use a chemical pigment that is sensitive to a narrowish wavelength range (a normal distribution with mean at the wavelengths of red, green and blue for the respective cones). If one eye happens to be renewing the pigment for a particular colour, then the concentration of the pigment in the cones of that eye might be slightly different, so the signal will be weaker or stronger accordingly. If the effect is permanent and always the same difference between eyes, then there must be a permanent difference between the pigment concentrations (rather like some people have different iris pigmentations). A temporary effect would occur if one eye was renewing pigment when the other wasn't, or after stronger exposure of one eye to a strong colour when sensitivity is reduced so the opposite colour is seen more strongly. Medical advice would be recommended if there is a large permanent difference that happens suddenly, otherwise most of us are happy to accept that our colour vision is slightly imperfect, but not as imperfect as the one in twelve males who have one of the many forms of colour blindness (usually caused by the wrong pigment in the cones). Dbfirs 22:06, 19 December 2010 (UTC)

I noticed in childhood that I saw things slightly differently coloured with my two eyes. I have never worried about it. It's not clear to me that it is even necessarily a physical or organic difference in my eyes. Since seeing is something that the brain actually learns to do, it seems to me that there is no need for the pathways from the two eyes to learn identical processing of colour: the brain learns to cope with the fact that the field of view from the two eyes is different, so there is no prima facie reason why it should have to identify the "colour signals" from the two eyes at that level. --ColinFine (talk) 00:40, 20 December 2010 (UTC)

Yes, it seems that different people (and possibly different eyes in the same person) detect colour very differently, with some eyes having forty times as many cones as others (though not this big difference in the same person). The brain does all of the compensation work (like a good digital image processor), and we only notice the effect when we confuse it by rapidly switching eyes. What is surprising, given the difference in physiology, is that most people seem to have roughly the same final perception of colour, and agree on shades, etc. This seems to be because we subconsciously learn to adjust our perception to match that of the majority. Dbfirs 08:46, 20 December 2010 (UTC)

I have done this before. Close one eye and open the other in a bright room for 1 minute. Then open the closed eye. Each eye sees somewhat different. --Chemicalinterest (talk) 12:32, 20 December 2010 (UTC)

I have sometimes observed this effect being caused by the *position* of my eyes. For some reason much warmer light was being reflected into one eye than the other, and moving my head shifted that light to the other eye. --Sean 17:25, 20 December 2010 (UTC)

[For Concentration] ADD meds (stimulants) vs. benzodiazepines/anxiolytic meds (depressants)

I am looking for some research articles/papers (Google Scholar etc.) but I am not exactly sure what search terms to use. (Edit: General (knowledgeable) response to the questions posed below is okay. I will try to find citations, to confirm later. Thanks.)

Specifically, I am looking at users who have Benzodiazepine dependence i.e. addicted to Benzodiazepines like Clonazepam; and, these same users are also addicted to stimulants like Ritalin.

Now my assumption is this, that if the user takes both of them together, for example Ritalin with Clonazepam, the net effect to the user will be the same as taking a placebo. As one is a stimulant and the other is a depressant. Is it as simple as this?

Currently Medical Professionals diagnose patients with ADD and Anxiety Disorders i.e. co-morbid disorders.

So then if treatment for ADD is Stimulants, and treatment for Anxiety Disorders is Benzodiazepines, is there any research done on what would be more effective for concentration?

As an example, say they decide to withhold benzodiapines to the test subjects, and only give stimulants. Or the other way around, they withhold stimulants from the test subjects, and only give benzodiapines?

--Vicgarin (talk) 18:16, 19 December 2010 (UTC)

I don't have any papers to cite right now, but as a quick preliminary response: no, it is not as simple as that. WikiDao ☯ (talk) 18:32, 19 December 2010 (UTC)

PS. I edited my original question i.e. General (knowledgeable) response to the questions posed below is okay. I will try to find citations, to confirm later. So if you would please elaborate, I would appreciate. Thanks. --Vicgarin (talk) 19:01, 19 December 2010 (UTC)

I'm just saying that the two varieties of drug do not "cancel each other out" as if the net effect of taking both were equivalent to taking neither. Taking both is different than taking either alone and is different than taking neither, in terms of a wide range of psychopharmacological effects, as far as I know, and I'd be interested too in any studies that have looked into that. WikiDao ☯ (talk) 19:28, 19 December 2010 (UTC)

It would help if you explained exactly why you need this. These drugs just mimic natural Neurotransmitter, of which - there is a lot and therefore, there is no simple stimulant/depressant pairing. Naloxone is used as a treatment for heroin overdose. Does that run parallel with your query?--Aspro (talk) 20:30, 19 December 2010 (UTC)

Start with PMID 17338593, find it in a library and/or online, read it carefully, read the citations relevant to your questions, do a citation search on those specific references trying to find other secondary literature reviews (ask a reference librarian in a medical library to help if possible) and then email your specific questions to the corresponding author, Dr. Kenna, whose email address is given in that citation. This is a very specific medical question and you shouldn't be asking the Reference Desk, you need to ask an expert. You probably also want PMID 18384709, PMID 9680053, PMID 20667290, PMID 20861593, PMID 17915180, PMID 15491232, and PMID 19476419, among others. Please remember to stick with the secondary literature ("reviews" in PubMed) instead of the ordinary journal articles which are much less accurate. Ginger Conspiracy (talk) 05:20, 20 December 2010 (UTC)

Alternatively, consider the analogous and well-known Speedball (drug) effect: "Cocaine acts as a stimulant, whereas heroin acts as a depressant. Coadministration provides an intense rush of euphoria with a high that combines both effects of the drugs, while excluding the negative effects, such as anxiety and sedation." WikiDao ☯ (talk) 11:23, 20 December 2010 (UTC)

Excluding the negative effects... until one or both of the drugs starts to wear off? Ginger Conspiracy (talk) 15:18, 20 December 2010 (UTC)

The reason I brought up addiction/dependence in my original question, was based on the assumption, that those treated for Anxiety disorders (Panic attacks, Socialized anxiety, Generalized anxiety etc.) will have developed a tolerance to benzodiazepines (clonazepam).

And similarly those treated for ADD or ADHD will have developed a tolerance to stimulants (Ritalin, Dexedrine, Adderall)

Not specifically substance abuse.

I was looking for research articles on how they treated those with co-morbid disorders: Anxiety Disorders & ADD. I can't find an article that deals with these two disorders only.

There is Atomoxetine (not a stimulant) for use in ADD and/or SSRIs for use in Anxiety disorders. But no research has been done on the efficacy of Stimulants & Benzodiazapienes, like I mentioned in my original question? --Vicgarin (talk) 21:06, 22 December 2010 (UTC)

Please address your question to medical experts; especially the corresponding authors whose email addresses are given in the PMID review links above, and let us know what they tell you. Thank you. Ginger Conspiracy (talk) 01:29, 23 December 2010 (UTC)

Birds' ability to map the night sky

Hi,

In a TV programme shown recently in the UK ("The Zoo"), it was said that corncrakes map the stars in the sky to enable them to return home after migration. For that reason, the chicks in a captive breeding programme were prevented from seeing the night sky at the breeding site because that would not be their eventual home.

Although the pattern of the stars obviously varies with latitude, the difference in latitude between the breeding site and the eventual release site appears to be only about one degree, which basically this means that the stars are shifted in the sky by about one degree. Is it really possible that corncrakes can reliably detect differences that small? I find it very hard to believe. 21:54, 19 December 2010 (UTC) —Preceding unsigned comment added by 81.159.79.39 (talk)

I don't have an answer for you, but wanted to note that the sky also appears to rotate overnight, so the star locations, relative to the nest, change. I wonder how they deal with that. StuRat (talk) 02:51, 20 December 2010 (UTC)

Maybe they can locate the Pole Star? 81.159.79.39 (talk) 02:55, 20 December 2010 (UTC)

The ability of animals to find the migratory homes is still one of the great mysteries of science. It is unknown what mechanisms MANY animals use to find their homes, and it is likely that different animals use different methods, or combinations of methods, to help them. --Jayron32 02:59, 20 December 2010 (UTC)

Bird migration#Orientation and navigation might be interesting if not exactly helpful for this particular question. I would suggest that olfactory (smell) and magnetic field effects might be more useful for the birds than celestial navigation. Most birds don't prefer to fly in the dark, for reasons you might expect. Ginger Conspiracy (talk) 05:40, 20 December 2010 (UTC)

Taking high dose vitamin D supplements every 5 days

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

If you have questions about adjusting the dosages or timings of supplements, you should consult a qualified medical professional — your physician or pharmacist should be able to advise you. TenOfAllTrades(talk) 23:29, 19 December 2010 (UTC)

Our article on Plateau principle says:" Once hydroxylated, the vitamin has a half-life of about 2 months", but we cannot give medical advice except to warn that a daily dosage 50,000 IU would probably be toxic. As advised above, please consult a professional rather than relying on Wikipedia articles, however well-written. Dbfirs 23:35, 19 December 2010 (UTC)

Thanks. B.t.w., this is not a medical question at all, as the supplements I'm taking are available without prescription. I don't plan to go to a doctor, as I've read that the science on vitamin D is controversial and many doctors still stick to the guideline that 200 IU per day is the recommended dose. So, the likely "medical advice" I would get is to stop taking the supplements; medical advice on this issue would thus be irrelevant. Count Iblis (talk) 01:06, 20 December 2010 (UTC)

Please don't restore reqeusts for medical advice to this page, Count Iblis. It it still medical advice you're requesting, even if it deals with medications or supplements taken off-prescription. Please consult your pharmacist for information about supplements; don't ask Wikipedians to give you their advice. TenOfAllTrades(talk) 02:09, 20 December 2010 (UTC)

The advice your doctor would give is in fact relevant because it is based on Science. Just because you choose to ignore it, doesn't make it irrelevant. If you want advice on megadosing or some other unscientific modality, then this isn't the place to ask. Vespine (talk) 03:09, 20 December 2010 (UTC)

Counting on medical doctors to base their advice on science is a bit naive. --Trovatore (talk) 08:51, 20 December 2010 (UTC)

Indeed, doctors are not scientists and they stick to guidelines (which they legally have to do). In case of Vitamin D, the official guidelines are (according to the science on vitamin D), hopelessly outdated. According to the science, 10,000 IU per day is a normal dose, it is not a megadose at all. You only have to be careful if you also get a large amount of vitamin D from the sun (you can get 10,000 IU per day from the Sun). In fact, it is likely that the official guidelines that 200 IU per day is enough, is dangerous advice that is best ignored. Count Iblis (talk) 13:11, 20 December 2010 (UTC)

THe VitD from the sun is not the same as ingested Vit D, neither is the physiology involved the same. 92.15.26.185 (talk) 16:26, 22 December 2010 (UTC)

Or just read today's newspaper.

or read this Count Iblis (talk) 14:06, 20 December 2010 (UTC)

Hypervitaminosis D and Vitamin_d#Overdose_by_ingestion says that overdosing on Vitamin D causes premature aging and heart disease. Do not make the mistake of thinking that because small doses are good, bigger doses must be even better - it does not work like that. There is only a narrow range between benefit and harm. Taking megadoses of vitamins is foolish and does you harm. Taking five days doses or more every five days is really crazy. 92.15.13.152 (talk) 15:28, 20 December 2010 (UTC)

Oh my goodness. A newspaper is NOT a peer-reviewed journal. The popular press has a major problem being able to distinguish between good science and total bullshit. If you want to be able to prove your point, you're going to have to find better sources than the Montreal Gazette and The Globe and Mail. I am sure they are fine papers, but they are not a source for scrupulously reliable scientific information. --Jayron32 15:27, 20 December 2010 (UTC)

I know that about newspapers, but all I'm saying is that we can read what the experts themselves are saying. The point being that what they are saying is totally incompatible with the official recommendation regarding vitamin D. The facts regarding vitamin D are that toxicity likely starts at 40,000 IU per day taken over a period of many weeks. There are no known cases of vitamin D overdose caused by consuming 10,000 IU per day or less. Recently, the maximum safe dose was increased from 2,000 IU to 4,000 IU for people older than 9 in the US. But note that this means that everyone in the US can count on taking 4,000 IU per day without that doing harm, regardless of other factors like getting a lot of vitamin D from the Sun. What is clear is that as long as you make sure that your total intake is less than 10,000 IU per day, you cannot get ill effects, unless you suffer from certain rare diseases (in which case you can't spend a lot of time in the Sun either). Count Iblis (talk) 16:18, 20 December 2010 (UTC)

What experts? Papers are well known to spin stories, I have no idea if the majority of 'experts' on vitamin D are arguing for megadoses but I damn well wouldn't be trusting a random paper to tell me particularly not Globe & Mail which from memory doesn't have a good track record with science stories (at least re: climate change). The paper itself quotes on 'cautionary' scientist, this seems common in spin stories, if you come across an article on a car that runs on water (and I did actually in somewhat respectable media sources once although I can't recall if they quoted a 'cautionary' scientist), they may sometimes also quote a sole 'cautionary' scientist. Also define 'ill effects'. 10k IU may not kill you or cause such obviously harmful effects, but if you are taking it to ward off various cancers or whatever else you need to be sure such (difficult to detect and complicated) negative effects aren't being missed. I would guess there's a very good chance 10k IU does have some harmful effects in far more people you describe even if it's likely to be a net positive for most people (I'm not saying it is, as should be clear I have no idea). Nil Einne (talk) 17:09, 20 December 2010 (UTC)

Count Iblis is correct in claiming that some experts are investigating the benefits of high dosages of vitamin D, there was a BBC programme about this recently, but I don't think they have ruled out the possibility of harm at levels this close to toxicity. Best advice would be to wait for further research before risking very high dosages. Dbfirs 22:12, 20 December 2010 (UTC)

The harm is likely to be insidious - it silently accumulates and then suddenly you have something seriously wrong. The was a Scientific American article about this, in the November 2009 or 2008 issue I think. 92.29.124.17 (talk) 22:39, 20 December 2010 (UTC)

From what I´ve read (and I don't want to push my view here, so I won't give my sources, everyone can search out the sources he/she trusts bests and agree/disagree with me), I have formed the following conclusion about 2 years ago. Until a few centuries ago, the normal vitamin D intake was of the order of 10,000 IU per day, mainly from exposure to UV radiation. This should i.m.o. be considered to be the normal physiological vitamin D intake for humans. However, what has happened gradually during the last few centuries and more dramatically in the last few decades, is that we spend so much time indoors that we get extremely low doses of vitamin D. That then leads to problems with the bones. Then, to not get those problems with the bones, you need a small dose of vitamin D every day, of the order of a few hundred IU per day.

Now, there is reasonably strong evidence that vitamin D does a lot more than promote bone health. This evidence comes from various independent research groups and from different types of investigations (epidemiological studies, studies looking at the way immune cells work etc. etc.). Then, my thinking is that while this is not rigorously proven, the burden of the evidence should be on the hypothesis that extremely low doses that are just enough to maintain healthy bones are good enough for overall health. Compare with humans stopping to eat fruits and vegetables and then having to get some small dose of vitamin C to prevent getting scurvy. If everyone does this for a few centuries and it becomes accepted practice, you can imagine that a grapefruit would be considered to contain a "megadose" of vitamin C. People could then consider eating fruits and vegetables potentially unsafe and would only recommend it is there was rigorous proof that it reduces the risk of cancer and if adverse health risks were ruled out. Thing is that despite not having such proof (not just w.r.t. vitamin C, we don't even know all the compounds that are contained in, say, a cauliflower), we do eat fruits and vegetables.

About the dose at which toxicity starts, I have read that you need to take something of the order of 100,000 IU per day for a few weeks to get ill. But for some people toxicity may start at a lower dose, and some experts have estimated that toxicity like starts in some individuals at 40,000 IU per day. It is not likely that this toxicity dose can be near to 10,000 IU because that is considered to be normal dose that you can get from the Sun. There is a dispute about a study in which volunteers were given 20,000 IU per day on whether the results there show a small elevated calcium level. Now, I don't think 10,0000 IU/day should be considered close to a dangerous dose. Compare e.g. to the recommended calcium dose and the dose at which you get toxicicity. These two doses are also apart by a factor of 3 to 4. Or compare the recomended dose for H2O and the toxic H2O dose.

I take 10,000 IU per day during winter when I know for sure that I'm not getting any vitamin d from the Sun at all. In the summer I take 5,000 IU per day. That way I stay an order of magnitude below the treshold at which toxicity may begin to start in some individuals. The reason why I do this is not per se to reduce the chance of getting cancer. I don't think cancer is all that relevant, it wasn't the main cause of death for our pre-historic ancestors. If vitamin D at, say, 2000 IU per day does reduce the risk of getting cancer, it is likely just a side effect of the lack of its main function. Presumably, the optimal dose is around 10,000 IU per day which one should compare to an F1 car that is fully tuned for optimal performance. If you move a bit away from the optimal settings, the car won't fall apart. But move away from this by a signifact amount, and then you may see it malfunctioning.

Anyway, all this is my personal opinion on this matter... Count Iblis (talk) 00:24, 21 December 2010 (UTC)

If you bother to read the articles, you will see that the body has its own mechanisms to prevent overdose from skin-created Vitamin D. But it does not have overdose-prevention mechanism for ingested Vitamin D. You say "Now, I don't think 10,0000 IU/day should be considered close to a dangerous dose." So your opinion is going to alter physiology? You must be a god. Its like saying "Now, I don't think driving down Main Street at 10000 miles per hour should be considered close to a dangerous speed". I do believe you are going to do yourself pernament irreversible damage. 92.24.188.27 (talk) 15:28, 21 December 2010 (UTC)

I think most experts would say something like: "10,000(0) IU/day is probably safe for most people", but perhaps Count Iblis will let us know in a few years whether he has suffered benefit or harm from this dosage. Personally, I would prefer to err on the lower side in the absence of regular medical monitoring. If I had some 50,000(0) IU tablets, and wanted to use myself as a guinea pig, I would cut them in half and take half every three days, but please don't take this as medical advice because I have no medical expertise. Dbfirs 21:26, 21 December 2010 (UTC)

He won't be able to let us know as he will be dead or diabled. 92.15.26.185 (talk) 16:26, 22 December 2010 (UTC)

400IU is the current RDA. 100000/400 is two hundred and fifty times the RDA. Its almost like taking a years worth in a day. 92.15.15.127 (talk) 22:07, 21 December 2010 (UTC)

... later note: sorry, I meant 10,000 which is 25 times the RDA. Dbfirs 21:30, 22 December 2010 (UTC)

True, but the current recommendation is considered by some experts to be unreasonably low compared with the normal production in human skin exposed to summer sunlight. Dbfirs 22:30, 21 December 2010 (UTC)

You put an unusual number of zeroes after the comma, which 92.15 may have taken literally. --Trovatore (talk) 22:38, 21 December 2010 (UTC)

... oops! I must have been too tired to count zeros both in my post (where I have now striken the accidental zero), and in 92.15's reply. I foolishly copied from an earlier error. Apologies for causing confusion, but this just goes to illustrate the danger of taking advice from unqualified people who give replies here! Dbfirs 21:13, 22 December 2010 (UTC)

Even 25 times the normal dose would do you serious harm if you took other vitamins at that rate. I don't see why Vitamin D should be an exception, especially bearing in mind that the body limits skin production. But its the OPs serious medical problems, disability, slow death, and funeral. 92.29.126.195 (talk) 11:48, 22 December 2010 (UTC)

What you seemed to have missed is that the body limits skin production to somewhere between 10,000 IU to 20,000 IU per day; toxicity is believed to start at a factor 2 to 4 above this. So, in this respect, it actually is very much like other vitamins/minerals. You seem to take the RDA very serious, but the logic behind the RDA for vitamin D is totally flawed. If you apply that same logic to vitamin C, you would take the RDA to be just enough to prevent scurvy. If I were to argue that eating grapefruits is healthy, you would object to my statement on the grounds that a grapfruit contains an order of magnitude more vitamin C than the RDA. Count Iblis (talk) 14:08, 22 December 2010 (UTC)

You might benefit from reading Ben Goldacre's book, Bad Science, where he talks about the crazy thing nutritionists say about vast overdoses of vitamins. It's a very approachable work that doesn't require a lot of time to read. He discusses several of the objections above in more detail, and includes references. -- JSBillings 14:30, 22 December 2010 (UTC)

I don't think that would apply here, because we are not talking about taking large doses here. Count Iblis (talk) 15:51, 22 December 2010 (UTC)

I'd certainly call a dose 25 times more than the recommended a large dose; I'd call it an extremely large dose. Many years ago I went through the same thing with Vitamin C: everyone was saying how megadoses were the new wonder pill. So I took a megadose tablet every day. I got bad pains in my kidneys, although I dont think I made the connection at the time. It wasnt until some years later that I found out that megadoses of VitC damaged your kidneys. More recently I stopped taking a multivitimin pill every day as I read a scientific paper that people who overdosed on vitamins had higher mortality that those who didnt. In other words, high doese of vitamins are toxic. 92.15.26.185 (talk) 16:21, 22 December 2010 (UTC)

The point being made is that the recommended dose is under review and is considered by some to be unreasonably low. I agree that self-administered experimentation without medical monitoring is not to be advised. Dbfirs 21:30, 22 December 2010 (UTC)

December 20

Add salt to hot water bottle?

Can I make the heat in my hot water bottle last longer (I mean increase the heat capacity of the water) by adding salt? How much salt? How much difference would it make? I can reuse the water by pouring it from the bottle into a pan and pouring it back with a funnel. Of course I don't want the initial temperature to be increased (that would perish the rubber) but I do want more heat in there. —Preceding unsigned comment added by 78.148.143.201 (talk) 00:39, 20 December 2010 (UTC)

Boiling point elevation is a real effect, but too small to make much of a difference here. Yes, you can marginally raise the maximum temperature of hot water by adding salt to it before heating it, but ultimately we're talking about a difference of about 1-2% here, and that 1-2% difference might mean adding maybe 30 seconds or so to the effective usable time of your hot water bottle. In other words, not enough to bother. --Jayron32 01:17, 20 December 2010 (UTC)

Adding salt to water lowers the specific heat capacity, i'm not sure exactly how this is related to Boiling point elevation, or cooling time, but I agree with the above, getting a few minutes of an extra few degrees is not going to make any noticeable difference. Hot water bottles have been around for a long time, if it was worth filling them with brine, i'm sure it would be common practice. Get an extra blanket. Vespine (talk) 01:23, 20 December 2010 (UTC)

You could try to experiment with molten salts, these are also used for thermal storage. Count Iblis (talk) 01:30, 20 December 2010 (UTC)

Also consider that wattle bottles often leak, and salt-water is a worse spill to clean up, especially if it gets into electronics (like the alarm clock you pushed onto the floor when it went off :-) ). StuRat (talk) 02:47, 20 December 2010 (UTC)

You specifically mentioned that you didn't want to increase the initial temperature, so adding salt would actually reduce the thermal capacity from the same starting temperature (Fresh Water: 4186 compared with Sea Water: 3993 J kg⁻¹ K⁻¹; mainly offset by the fact that sea water is about less than 3.5% heavier). Buy a bigger bottle! Dbfirs 08:35, 20 December 2010 (UTC)

Since seawater is denser then freshwater, you might not need to get a bigger bottle. Googlemeister (talk) 19:14, 20 December 2010 (UTC)

Yes, I realised that fact and checked that it is always less than 3.5% denser (typically 2% heavier for a fixed volume), so you would need a bigger bottle whatever concentration of salt you used. I must admit that I don't know why salty water stores less heat per unit volume. Perhaps someone can explain the fact? I have a theory, but this is not an area where I have any expertise, so I don't know whether my guess is correct. Dbfirs 22:00, 20 December 2010 (UTC)

You could try a brick heated in the oven and wrapped in a towel - probably a wastful way to heat it. I didnt think people needed hot water bottles anymore. 92.29.124.17 (talk) 22:34, 20 December 2010 (UTC)

Well now you know how the other half live. It's more cost-effective to heat the person(s) directly than to heat every nook of a house. Such economy may never cease to be necessary for many people. --129.215.4.98 (talk) 23:53, 20 December 2010 (UTC)

I've heard of them being used for someone who is sick, and having chills, so you don't have to overheat everyone else in the house to make the sick person comfortable. It could also be used if one person in the bed likes it warmer than the other(s). StuRat (talk) 01:15, 21 December 2010 (UTC)

Why not use an electric blanket instead, if you can still buy them, although they seemed scarily dangerous to me. With central heating now being universal in the UK, nobody uses them anymore. I'm not sure they'd work with the lower North American voltages. Or buy an additional high tog duvet - probably safer. 92.24.188.27 (talk) 15:34, 21 December 2010 (UTC)

You seem to have answered your own Q; an electric blanket is inherently dangerous, that's why people would prefer to use a hot water bottle. And yes, they do work in North America. StuRat (talk) 17:56, 21 December 2010 (UTC)

Central heating now universal? We don't all have such luxurious houses! Also, overblankets, the most effective type of electric blanket, doesn't seem to be made any more in the UK, though the cheap and less-effective underblanket, with extra safety cut-out circuitry that often goes wrong, is still sold. Dbfirs 19:12, 21 December 2010 (UTC)

What place are you in where central heating is not the norm? In the UK houses are only without central heating where there isnt a gas supply and the owners don't want to go to the expense of oil heating at it is almost as expensive as electricity. I understand that in snowy Scandinavia, electric heating is most common, perhaps due to having lots of hydroelectric and heavily insulated homes. 92.15.5.196 (talk) 19:38, 21 December 2010 (UTC)

A place exactly as you describe. The nearest gas supply is five miles away, and older houses here have little insulation. In the house where I was born, I can remember when a glass of water by the bedside was frozen by morning, though the house where I now live is not quite as cold as that. Dbfirs 21:32, 21 December 2010 (UTC)

And did the house also lack plumbing ? Otherwise, I'd expect the pipes to freeze. StuRat (talk) 21:34, 21 December 2010 (UTC)

Strange you should ask that, because I've just thawed out some frozen pipes here. The house where I was born had very limited plumbing. Dbfirs 22:26, 21 December 2010 (UTC)

Not so strange, really, since the one is an inevitable result of the other. And, since water damage from burst pipes can cost far more, it doesn't make sense to keep it so cold that this becomes a possibility. StuRat (talk) 15:49, 22 December 2010 (UTC)

Well the house and plumbing have survived for over a hundred years without central heating, but this frozen bit was a later addition very near to an outside wall. It is more than 25 years since it was last frozen. Dbfirs 21:37, 22 December 2010 (UTC)

There's a big difference between being "the norm" and "universal". StuRat (talk) 21:32, 21 December 2010 (UTC)

Put 165 grams of Caesium-137 in your hot water bottle and it will generate about 100 Watts of heat for many years. Count Iblis (talk) 23:06, 22 December 2010 (UTC)

Drinks when sick

I have heard various advice over the years that clear liquids are better for you when you are sick than colored liquids, usually under the pretense of "needing to stay hydrated". However, my mom has always seemed to press on me something like 7-up (which is decisively clear), which raises to me the question what could be the benefits of a clear soft drink versus cola or some other colored soft drink? Why are clear fluids better for you than non-clear fluids (or are they)? Ks0stm ^(T•C•G) 00:49, 20 December 2010 (UTC)

I think the idea is to not drink stuff which is going to be heavy on your stomach; so something like milk or orange juice is probably too much for a sick stomach to take. Water or dilute tea or something like that. Functionally, it probably doesn't make much difference which brand of carbonated sugar water you drink, if you are drinking carbonated sugar water. Not sure whether that puts the whole class of drinks under "clear" or "not-clear", but I can't imagine being able to cut the line that finely. --Jayron32 01:15, 20 December 2010 (UTC)

I was always told it had to do with the caramel coloring being heavier on the stomach. Dismas|^(talk) 01:37, 20 December 2010 (UTC)

Maybe the caregiver is thinking ahead, and thinks clear vomit will cause fewer stains ? StuRat (talk) 02:44, 20 December 2010 (UTC)

Do you have personal experience of that? 92.15.13.152 (talk) 12:30, 20 December 2010 (UTC)

this is probably closer to the truth than it appears at first glance. --Jayron32 02:47, 20 December 2010 (UTC)

While it may be easier on the stomach, for some reason it seems to have been extended to all illness, anything from strep throat to stomach flu. Is there any particular advantages it would confer in a situation where the stomach was not a part of the illness? Ks0stm ^(T•C•G) 02:52, 20 December 2010 (UTC)

I believe "clear liquid" is meant to rule out milk or coffee. My mother would give me stirred (de-fizzed) Coke when I was sick as a child, and it was just fine. I suspect that was an old Southern remedy. Ginger ale is a mild anti-nauseant (as are all ginger products). Acroterion _(talk) 04:26, 20 December 2010 (UTC)

Perhaps Adam's Ale is what is preferred. 92.15.13.152 (talk) 12:32, 20 December 2010 (UTC)

Found a source that appears to be related (but I can't access it), titled "Soft Drinks, electrolytes and sick children", from the Lancet 1983 Jun25;1(8339):1450 - Although, there are far more sources that point to problems associated with soft drinks in areas such as obesity, diabeties etc... (Thats a bit of a non-answer though isn't it). I was often given flat 7-up as a child if I had been quite ill and vomited. I was always under the impression that it helped to re-hydrate, and that the sugars and salts in the drink helped to replenish what I had lost while vomiting Darigan (talk) 15:38, 20 December 2010 (UTC)

That's actually a response to a formal comment to an earlier report on the treatment of diarrhea in infants. The gist of the response is to compare and contrast the electrolyte content of certain soft drinks and juices with the standard medical intervention. The standard treatment is very high in sodium and low in potassium but the comment article notes this may be undesirable in some cases. Juices provide high potassium and low sodium, while soda provides medium sodium and low potassium. It isn't really about judging what is best, but merely showing alternatives that may be more appropriate depending on a patient's condition. Dragons flight (talk) 16:40, 20 December 2010 (UTC)

The history of the popular UK soft drink Lucozade may be of interest, as it was originally produced specifically for the mildly ill. Although our article contains no images, the original version at any rate (I haven't drunk any for some years) was clear, very pale orange in colour and carbonated. This may have been made in deliberate accordance with the OP's recalled proscriptions, or may have helped to form them. Common wisdom has it that (strength-for-strength and volume-for-volume) lighter-coloured alcoholic drinks cause less hangover than darker ones, because the colour is caused by congeners that may contribute to the ill effects: this might also apply to the substances responsible for darker colorations in soft drinks. 87.81.230.195 (talk) 01:22, 22 December 2010 (UTC)

I expect just plain water is best for you when ill, as it puts less strain on your body to digest it. Things like Lucozade or Seven-Up are just sugary water with fizz and colouring. If you are suffering from severe dehydration, which is unlikely in the West, then this advice may not apply. 92.29.126.195 (talk) 12:00, 22 December 2010 (UTC)

Augmented Nasal Passages?

When your nasal passages are congested, perhaps because of a cold, the linings become a bit inflamed and the amount of mucus increases, thereby making it difficult or impossible to breathe through your nose, correct? What if you threaded a bit of piping through the entire passage? Suppose it started at the nostrils and terminated, I dunno, above the throat? Would that provide you with guaranteed clear breathing? I realize it completely defeats the sanitation/filtration aspect of breathing through one's nose, but I'm just curious about the idea in general. I can't recall ever hearing of someone doing this, but it doesn't seem impossible... The Masked Booby (talk) 01:26, 20 December 2010 (UTC)

There is the Nasal cannula which serves that purpose, but is a bit extreme. The inventor of "Breath Right" nasal strips said he tried the straws; and the strips apparently worked better for him. You should, of course, consult a doctor for medical problems, but you may want to research those nasal strips. --Jayron32 01:36, 20 December 2010 (UTC)

Sure, it's possible, but why do it ? Are you thinking of a case where the mouth is wired shut or otherwise unavailable for breathing ? StuRat (talk) 02:42, 20 December 2010 (UTC)

The mouth being wired shut would not interfere with breathing -- can't you breath through your mouth when you're in sustained maximum intercuspation? DRosenbach ^{(Talk | Contribs)} 04:19, 20 December 2010 (UTC)

Not if you read mouth to mean lips not jaw. But I would tend to disagree that there is NO benefit to this, I sleep on my front and find it much harder to sleep with a blocked nose and I'm pretty sure a blocked nose can also significantly contribute to snoring. Vespine (talk) 04:25, 20 December 2010 (UTC) Vespine (talk) 04:25, 20 December 2010 (UTC)

Nasal spray is available in small squeeze bottles. It clears the nasal passages. It can be obtained as over-the-counter medication at drug stores.173.189.136.110 (talk) 04:34, 20 December 2010 (UTC)

Alternatively, in case of persistent problems, you can also remove part of the nasal concha via surgery. Count Iblis (talk) 12:58, 20 December 2010 (UTC)

How does quantum entanglement / quantum mechanics "know" that you know the positions of their particles?

Apparently you're not allowed to know the positions of particles when it comes to the quantum realm. But how does the quantum realm "know" whether you know this? I've been having a hard time wrapping my head around that notion, but hopefully you can change this situation. --70.179.178.5 (talk) 07:31, 20 December 2010 (UTC)

It's not if you know it, but if you measured it. Measuring a particle changes its state (because in order to measure it you have to interact with it). But see Quantum eraser. Ariel. (talk) 08:14, 20 December 2010 (UTC)

What happens mathematically is that, to find the probability of a given final state in quantum mechanics, you compute a sum over possible intermediate states then square the result. The "given final state" is the state of the system and environment. The environment includes the experimental apparatus, the experimenter, and everything else in the world. If you learn something about the system, say whether a particle went through slit A or B, then the final environment where you know it was slit A differs from the final environment where you know it was slit B (by slightly different electrical activity in your brain, for example). Since the final states are different, you have to compute two different sums and square them separately to get the probabilities of each outcome. On the other hand, if there's no unambiguous information in the final state of the system+environment regarding which slit the particle went through, you add up histories for both slits and square the result, which gives you a different answer. So it is, effectively, a matter of what you know (or, more precisely, what information is retained anywhere in the universe). Why the universe works that way is not really understood. -- BenRG (talk) 09:14, 20 December 2010 (UTC)

To clarify, it is incorrect to say that quantum measurement requires interaction. See interaction-free measurement. Looking for a particle and failing to find it tells you something about the particle's location (it's not there), even though no interaction took place. -- BenRG (talk) 09:19, 20 December 2010 (UTC)

Expect to keep having trouble wrapping your head around it. The two major revolutions of the early 20th century were relativity and quantum mechanics. Both were, at first, highly counterintuitive.

But there's a huge qualitative difference between the two. Relativity is counterintuitive at first, but you can retrain your intuitions to accommodate it. QM, not so much. That's because QM is virtually impossible to square with realism, and we are hard-wired realists.

The usual solution on the part of working physicists is to stop thinking about these things. I think it was Richard Feynman who said "shut up and calculate". John von Neumann claimed that "in mathematics, you don't understand things; you just get used to them" — that would be much more appropriate applied to QM. --Trovatore (talk) 08:38, 20 December 2010 (UTC)

The Many-Worlds interpretation is by far the simplest explanation. You simply get entangled with the particle when you measure it. It's no different than how one particle gets entangled with another. I suggest reading the Less Wrong Quantum Physics Sequence. If that's too long for you, just read Classical Configuration Spaces and Decoherence. — DanielLC 18:13, 20 December 2010 (UTC)

"Simplest" is subjective. Personally, I subjectively feel the many-worlds interpretation is pretty close to bat-shit insane, even though I know it is not provably any more right or wrong than any of the other mainstream interpretations of quantum mechanics. Of course, on the other hand, lots of things that are provably correct in quantum mechanics also feel insane, so maybe there is no accounting for subjective taste.  ;-) Dragons flight (talk) 18:37, 20 December 2010 (UTC)

Normally it's somewhat subjective. In this case, it's just the Copenhagen interpretation with wave-form collapse missing. Entanglement has been experimentally proven on small scales, and it's really all the Many Worlds Interpretation uses. Adding a law couldn't possibly make things simpler, especially when it's the only nonlinear, non-unitary, non-differential, discontinuous, non-local, CPT-asymmetric, Liouville's Theorem violating, or indeterministic law in all of quantum mechanics. It does require more universes, for a certain definition of more, but given that there's about 10^80 particles in the visible universe, and all the known laws of physics can fit on an index card, complexity of laws is clearly what matters. Also, it's theoretically possible to prove right, just obscenely difficult. If you want to actually test it, you can't prove it, but if you're wondering if there's a difference philosophically speaking, there is. — DanielLC 00:54, 21 December 2010 (UTC)

I like the MWI because the first time somebody explained it to me was the first time I understood the mathematical structure of quantum mechanics. I think it's helpful in understanding how the QM rules lead to the universe "knowing what you know", as the OP asked. It's not necessary to believe in it to get that benefit. I don't personally believe it, or disbelieve it, I suppose. I trust the well-tested quantum rules more than I trust untested rules added with the apparent purpose of avoiding MWI, but that's not at all the same as believing in MWI. -- BenRG (talk) 08:25, 21 December 2010 (UTC)

there a movement back and forth in time so the two partical are conected and afected . thanks —Preceding unsigned comment added by 212.117.145.118 (talk) 06:52, 21 December 2010 (UTC)

No, not at all. -- BenRG (talk) 08:25, 21 December 2010 (UTC)

That sounds like the Transactional interpretation.

Think of it if you like as what you might see if you were running a 4D simulation in a computer of a kind of minimum principle, with some of the boundary condition information specified at the end-time of the simulation, rather than the start time. So you start by propagating a 'best guess' forward from your incompletely specified initial conditions till you get to the end-time of the simulation, at which point you discover there's a mismatch, which you can patch up by propagating a 'correction' back towards the start-time of the simulation. You can see, at least for a simulation in a computer, how that might make some sense.

If I remember correctly, TI doesn't make any predictions that are different from the Copenhagen Interpretation (there was a paper, I think about 1990 in Foundations of Physics, that showed this in some detail). Rather, it's a way of creating a consistent possible intermediate picture for what Copenhagen says you're not allowed to picture. For those of a more realist disposition, it's a way of coping with non-local information and constraints in a way that is at least instantaneously local, albeit one that's build-up includes these back-in-time correction waves.

Perhaps best not to take it too seriously; but to see it as a way to develop intermediate-time pictures in a consistent way that develop smoothly, which can be a useful additional perspective to be able to add, when trying to think about some of the odder thought experiments, that are trying to push you into giving a realistic picture for "What was happening there?" Jheald (talk) 09:46, 21 December 2010 (UTC)

If QM applies to observers, then the MWI is correct. A simple argument by David Deutsch can be invoked in which a measurement is performed by an observer such that observer plus measured system is a closed system. Then, there always exists a unitary map that will erase the memory of the measurement result and restore the original state of the measured system, but such that the observer remembers having performed the measurement (but of course, unable to remember the result). But if the CI is true, this won't work; the wavefunction of the measured sytem won't be restored, because after the measurement, the unitary map that would restore it, would only act on the "real sector" of the state, the other sector where a different result is found, supposedly does not exist according to the CI so it cannot contribute to the final state. It is easy to verify that the state is always restored to the original state by repeatedly performing this procedure and performing a new measurements on the final states.

So, MWI can actually be experimentally distinguished from CI, but in practice that would require implementing observers within large scale quantum computing simulations. That's a bit far fetched as we can't even implement observers using ordinary computer simulations. But being able to actually implement a thought experiment is irrelvant in physics, all that matters is that there are no theoretical obstacles to be able to implement it. So, what is relevant here is that all unitary mappings can be implemented using quantum computers, as they can all be reduced to sequences of CNOT and Hadamard transforms. So, there is nothing in theory that would prevent one from actually performing Deutsch's thought experiment. I.m.o. this proves that if the MWI is not correct then QM itself is not correct. Count Iblis (talk) 14:27, 21 December 2010 (UTC)

First of all, Deutsch does not strike me as a very smart guy. He got famous by accident, by proposing a model of quantum computation that became popular, but his creation was not all that interesting. It's like Larry Wall and Perl, to take a completely random example. I think that some of what Deutsch writes about QM is correct, and some of it is wrong, but none of it is very interesting.

Second, this experiment can't be performed in practice, and to argue that it's performable in principle you have to make philosophical assumptions that effectively imply the MWI already. For starters, you have to assume that measurements of the sort that invoke the Born rule can be thermodynamically reversible. But Copenhagen supporters can always say that thermodynamics has an essential role in the collapse process, and how are you going to respond to that? It might even be true. The fact is we have no idea what happens to the quantum rules when they're extrapolated that far from the regime where they've been tested. We know something happens to them because we see general relativity in the classical regime, and we don't understand how that works. It's not even clear what unitary evolution means in a GR universe. The MWI starts with an equation (the Schrödinger equation) describing unitary evolution in terms of an a priori time coordinate. That equation makes accurate predictions in the lab so far, but the philosophy behind it is seriously at odds with the philosophy behind GR. The path-integral formulation of QM seems a bit closer to GR, and MWI doesn't seem so natural there. The path-integral formulation suggests that it's just as natural to constrain the end of the universe as to constrain the beginning. So much for all the worlds that don't meet the constraint. It's just ridiculous to pretend that we understand physics at this level well enough to say anything about the MWI. -- BenRG (talk) 00:34, 22 December 2010 (UTC)

Hmmm, I thought that in case of quantum gravity you have the Wheeler-deWitt equation H|psi> = 0. Count Iblis (talk) 22:44, 22 December 2010 (UTC)

Parallel RLC network

Can someone please tell me why the impedance of a parallel RLC network is at maximum in resonance ? With the aid of mathematical equations. — Preceding unsigned comment added by Randeep d (talk • contribs) 07:43, 20 December 2010 (UTC)

See RLC circuit#Parallel RLC circuit and that whole article. Since the impedance of a parallel RLC circuit is the reciprocal of the corresponding series RLC circuit, and the "resonance frequency [for series RLC and most other circuits] is defined as the frequency at which the impedance of the circuit is at a minimum," it follows that the impedance of a parallel RLC network at the resonance frequency will be its maximum. Ginger Conspiracy (talk) 12:05, 20 December 2010 (UTC)

embryology

if left umbilical vein is obliterated and remains as ligamentum teres in adults then why it is on the right side of the body instead of left side? — Preceding unsigned comment added by Afsawal1 (talk • contribs) 11:22, 20 December 2010 (UTC)

Because it went all the way across before the left side was obliterated. See Umbilical vein. Ginger Conspiracy (talk) 12:13, 20 December 2010 (UTC)

Lots of things start on one side of the body, then cross over to the other side. I'm not sure why, though, as this implies a longer route. StuRat (talk) 17:35, 20 December 2010 (UTC)

Evolution isn't perfect. ;) --71.240.162.87 (talk) 06:06, 22 December 2010 (UTC)

Propsopagnosia and specific face parts

My understanding after reading the article is that people with propsopagnosia have problems putting all the pieces together to recognize a face, but if they focus on or are only shown parts, can they perceive basic traits such as size and shape? For instance, if a person with this disorder were shown two pictures, one of Karl Malden's nose and one of Michael Jackson's nose near the end of his life and then asked which nose is thinner and which is more bulbous, could most propsopagnosics tell that? 20.137.18.50 (talk) 14:15, 20 December 2010 (UTC)

That would depend on the extent of the disorder and is likely to vary on a case-by-case basis. Anyone living with an agnosia might have practice overcoming it with concentration and effort, so I would guess yes, over time. If [15] (from page 79; call around to find a library that carries that) has prognosis information, you might consider please adding a Prognosis section to our article. Ginger Conspiracy (talk) 15:12, 20 December 2010 (UTC)

The question that really puzzles me here is why the OP used [[Prosopagnosia|propsopagnosia]] as a wikilink, linking to the correct article prosopagnosia but deliberately misspelling it as propsopagnosia. I don't understand why anybody would do that. Looie496 (talk) 18:00, 20 December 2010 (UTC)

I'd like to say I did it just to screw with you but the truth is that I looked at the word too quickly and saw three 'p's where there were only two in the word and typed it out for the word and copied and pasted the URL for the link using the link tool. 20.137.18.50 (talk) 18:37, 20 December 2010 (UTC)

Aha, thanks for the explanation. It didn't seem like the kind of thing anybody would do out of malice, but I just couldn't figure out a chain of events that would get there. Looie496 (talk) 18:50, 20 December 2010 (UTC)

I think the answer is that even a severely face-blind person could tell those noses apart, unless they have something more severe than mere face blindness. Even Oliver Sacks's Dr. P (the man who mistook his wife for a hat) could recognize such simple differences of shape, and he was much more than just face blind. The difficulty for prosopagnosiacs is recognizing people who have no unusual facial feature. -- BenRG (talk) 08:13, 21 December 2010 (UTC)

I think the Subtypes section of the article linked to by the OP answers the question: Associative prosopagnosiacs probably could tell the difference, still without being able to identify anyone by face; Apperceptive prosopagnosiacs probably could not.

See also the The Man Who Mistook His Wife for a Hat and the Visual agnosia articles. WikiDao ☯ (talk) 15:46, 21 December 2010 (UTC)

Except in a very severe form, I don't think there's any need for a flaw in basic recognition of visual features. The thing about facial recognition is that so many people are ridiculously, almost supernaturally, good at it. I mean, they can look at a snapshot of somebody on a TV broadcast and recognize that someone in their part of the country is the exact same person 25 years later and be so confident that they're actually willing to call the police about it. By comparison, you can hardly program a mechanical face recognition system so that it won't spot Osama bin Laden on an average day at the football stadium. Wnt (talk) 19:29, 21 December 2010 (UTC)

best thing for teeth after vomiting

I overheard a "debate" recently regarding whether, after vomiting, it was better to brush your teeth, rinse with baking soda, or rinse with mouthwash. I've done a little looking around and apparently the bad thing about brushing your teeth afterwards is that it helps the acid scratch away teeth enamel. Would toothpaste not satisfactorily neutralise? How valid is the "scratching away by brushing" theory? And baking soda seems most recommended, because it neutralises the acid, preventing it from damaging your teeth—does science verify this? I couldn't find any reasoning on the 'net for the mouthwash suggestion though . . . some are pro, some are anti, but no one says why. Any ideas? I have no personal need to know, really, I haven't vomited in years, but I'm interested in hearing what some science heads have to say on the topic. Thanks. 92.17.190.111 (talk) 16:21, 20 December 2010 (UTC)

Rinse well with water, then brush, and then mouthwash if available. (Do not swallow mouthwash unless the manufacturer has given you permission to do so. This is not medical advice.) Then figure out why you vomited? Then floss. Ginger Conspiracy (talk) 18:56, 20 December 2010 (UTC)

It depends on how much vomiting a person is doing. If this is an issue of vomiting daily, they should see a doctor ASAP. If its once every few years, as the OP states, then your teeth are perfectly resilliant enough to avoid any damage from such a rare occurance. --Jayron32 17:14, 20 December 2010 (UTC)

Vomit is normally quite acidic, and baking soda is alkaline, so, yes, they should neutralize each other (you would get bubbling when this happens). However, just getting the vomit out of your mouth quickly, by rinsing with water, is probably the quickest way to get rid of the acidity. If you want to brush with baking soda after, that's fine. StuRat (talk) 17:32, 20 December 2010 (UTC)

Chewing an antacid tablet would also help in the same way. WikiDao ☯ (talk) 18:23, 20 December 2010 (UTC)

Drink some milk, it acts as a chemical buffer that neutralises acids or alkalis. 92.15.27.229 (talk) 18:50, 20 December 2010 (UTC)

When I asked my dentist about something similar (brushing after drinking acidic, but sugar-free drinks), he said that it was better to brush before drinking than after, because the acid did effect the enamel, and it was possible to "brush it off". Acid erosion#Prevention and management says, "No brushing immediately after consuming acidic food and drink as teeth will be softened. Leave at least half an hour of time space. Rinsing with water is better than brushing after consuming acidic foods and drinks." (sources provided)--Kateshortforbob _talk 10:33, 22 December 2010 (UTC)

If you decide to drink milk, homogenized milk may not be quite the best thing. This is anecdotal but it twice made me vomit. ~AH1^(TCU) 17:32, 22 December 2010 (UTC)

Metallic vs. nonmetal antimony

The antimony in question

In the article antimony, it states that this picture is the nonmetal black form of antimony. The description of the picture states that it is metallic antimony. Which one is it?Chemicalinterest (talk) 16:47, 20 December 2010 (UTC)

Browsing around http://www.google.com/images?q=antimony makes me think it's the nonmetalic form in the vial. Ginger Conspiracy (talk) 17:12, 20 December 2010 (UTC)

FWIW the caption in the article was added here I'm guessing by looking at the image, the description in the image was added here by the same person I think as a translation of the Czech text added by the uploader (from wiktionary:kovový it does mean metal. Nil Einne (talk) 17:18, 20 December 2010 (UTC)

I see some shiny bits in the picture which look somewhat like a metal. It could be the light reflecting, though. --Chemicalinterest (talk) 17:24, 20 December 2010 (UTC)

I'd say it's impossible to tell from the photo. You really need a big solid crystalline lump of antimony for it to look like a "metal" as you'd normally think of a metal. Physchim62 (talk) 20:39, 20 December 2010 (UTC)

Tobacco

do tobacco companies wash off tobacco before putting it in cigarettes — Preceding unsigned comment added by Kj650 (talk • contribs) 18:08, 20 December 2010 (UTC)

Start at Tobacco#Production and follow links from there to get the full story of how Tobacco gets from the ground into cigarettes. It is a bit more complex than just stuffing it into cigarettes. --Jayron32 18:11, 20 December 2010 (UTC)

While it is being grown, I suppose it is washed by the occasional rain. It is dried in various ways to "cure" it, after which the tobacco companies buy it at auction. If it were washed after curing, the curing process would have to be repeated in some fashion, with some nicotine lost in the re-washing, so, no. Edison (talk) 02:27, 21 December 2010 (UTC)

Dawn chorus (birds)

Do birds raised in captivity sing a dawn chorus (suggesting it is cultural rather than genetic)? Does it happen wherever in the world there are birds, or not? Have scientists discovered any reasons for it yet? Thanks 92.15.27.229 (talk) 19:06, 20 December 2010 (UTC)

Birds of many species sing. Our article explains how there are many reasons: attracting mates, defending territory, etc. Many species start singing at dawn simply because they are diurnal and sleep at night. Singing in captivity would not suggest that the vocalization is cultural. In fact, the opposite: if a bird can be raised in captivity, isolated from others of the species, and still sing, this would indicate a genetic component, because the bird cannot have learned the song from other birds. SemanticMantis (talk) 19:20, 20 December 2010 (UTC)

I guess you have never heard a dawn chorus, because the point is that all the birds sing at once, so there is a thousand times or more intensity of birdsong in the dawn chorus than at any other time throughout the day. 92.29.124.17 (talk) 22:29, 20 December 2010 (UTC)

A quick look at the literature, I can see several theories as to why birds sing at dawn (honest signals, optimal atmospheric conditions for song, dawn is not a good time to forage, for example) but I don't see any studies to suggest it was learned behaviour, although it appears that many songbirds learn their song from parents or other of their own species. -- JSBillings 20:02, 20 December 2010 (UTC)

Lunar eclipse on Winter solstice

Is it a coincidence that the the pending lunar eclipse is on the solstice or does it happen more often then? Ariel. (talk) 23:21, 20 December 2010 (UTC)

A coincidence. The last time it happened was in 1638, apparently [16]. Physchim62 (talk) 23:38, 20 December 2010 (UTC)

(e/c) According to December 2010 lunar eclipse "it will be the first total lunar eclipse to occur on the day of the Winter Solstice since 1638, and only the second in the Common Era." WikiDao ☯ (talk) 23:41, 20 December 2010 (UTC)

Figures that just after I asked this every news headline emphasizes how rare it is. Thanks for the replies. Ariel. (talk) 02:51, 21 December 2010 (UTC)

It's not the winter solstice around here anyway. It's the height of summer! I do wish that people would take a global view of these things. Believe it or not, we can see the moon here in the souther hemisphere too. HiLo48 (talk) 00:08, 21 December 2010 (UTC)

Hu! I thought it was called that there too despite it not being winter, it's still Dec 21 over there. (Or did you guys shift your calendar months too? :) Anyway the article on it says that's not the case, and I didn't know that. Ariel. (talk) 00:48, 21 December 2010 (UTC)

The winter solstice is still called the winter solstice of course. But that's not for another 6 months... Nil Einne (talk) 14:56, 22 December 2010 (UTC)

Yup. 372 years. I'm staying up to see it :) Crimsonraptor (talk) 01:02, 21 December 2010 (UTC)

I guess our article should mention the fact that it isn't winter in one half of the world, and it shouldn't really be called winter solstice, but December solstice, rather. --Lgriot (talk) 11:16, 21 December 2010 (UTC)

It doesn't call it the winter solstice. It says "Northern Winter Solstice (Southern Summer Solstice)". -- Jack of Oz [your turn] 11:22, 21 December 2010 (UTC)

In any case, the solstice is at 2338 UTC, by which time it'll be the 22nd in much of the world. The eclipse is only on the same day as the solstice in timezones west of Greenwich. Algebraist 11:37, 21 December 2010 (UTC)

Antimony trifluoride

Won't the reaction of the elements make the pentafluoride? --Chemicalinterest (talk) 23:47, 20 December 2010 (UTC)

Not according to the Wikipedia articles. It would appear that in the case of excess Antimony, you get the trifluoride. In the case of excess fluoride, you can generate the pentafluoride. That's how I read it. There are references in those articles, if you have questions you could consult those. --Jayron32 01:03, 21 December 2010 (UTC)

December 21

Does an Alpha emitter also emit Beta?

Does an Alpha emitter also by necessity emit Beta radiation? Because over time the source will become highly charged and it seems to me it has to release some electrons (although possibly at low energy). I'm thinking especially of an RTG in a spacecraft (i.e. vacuum). Ariel. (talk) 00:51, 21 December 2010 (UTC)

Not really. Beta emission is a different process than just losing electrons from the electron cloud. Excess electrons in the electron cloud after alpha emission will just drift off; while beta decay is basically just an electron, IT involves formation of that electron from the conversion of a neutron into a proton. Different processes. --Jayron32 01:25, 21 December 2010 (UTC)

I know the process is different - I was wondering about the end result. (I guess it's not called beta emission if the process is different.). My question is: Would an alpha emitter spark occasionally? I can only imagine the ionization of air would allow it to neutralize, and in a vacuum I assume they ground the RTG? Or, does the alpha particle grab an electron on the way out? Ariel. (talk) 02:00, 21 December 2010 (UTC)

At the bulk level, it is hard to track individual electrons with any meaning. Alpha particles end up, eventually, as neutral helium. Whether they grab an electron "on the way out" from the parent atom, or whether they grab electrons from some other bit of matter, and then that bit grabs from something else, down the line, is probably undeterminable. Uranium-238 decays into Thorium-234 and Helium. The electrons just all kinda work out. --Jayron32 02:51, 21 December 2010 (UTC)

Yep, air ionization is definitely one way of balancing charges. Odds are the smoke detector in your home contains a very tiny piece of americium-241, which is used to continuously ionize a small amount of air inside the detector. A small amount of current flows between electrodes on opposite sides of the ionized region; the presence of smoke particles reduces the ionization of air, triggering an alarm when the corresponding reduction in current is detected.

On the other hand, this effect is only important for very small pieces (or least, very thin pieces) of radioisotope. While alphas emitted from the surface atoms may travel a few inches in air, the mean free path of 1 MeV alpha particles in most solid matter is down between 20 and 50 microns [17]. In other words, the vast bulk of alpha particles generated within a fuel rod (for example) come to rest less than a millimeter from where they were created. If this occurs in a metallic alloy, then there are plenty of electrons sloshing about to sort out any local accumulations of charge.

Note that you can get some pretty interesting effects if you work in nonconducting systems. While I'm not aware of anyone using alpha particles this way, one can spray intense beta rays (high-energy electrons) at a block of plastic; at reasonable energies (a few MeV to a few tens of MeV) electrons will penetrate a few centimeters. Charges build up inside the plastic until an edge of the block is grounded. This triggers breakdown of the plastic's resistance, and all the accumulated charge drains out at once. This abrupt current damages the plastic, leaving a Lichtenberg figure. TenOfAllTrades(talk) 04:00, 21 December 2010 (UTC)

In space, (i.e., an RTG on a spacecraft), there will be an interaction called the Debye sheath or plasma sheath. Because space is not a complete vacuum, but is actually a very sparse plasma, the buildup of charge will cause an electrostatic response in the surrounding plasma. The characteristic scale-length and the magnitude of this response is determined by the amount of charge and the parameters of the (not-totally-empty) region of space. The average distance between particles, the percentage of ionized to neutral particles, and the energy of the ions, all determine the "thickness" of this sheath region, where bulk electrostatic effects are detectable. This will include accumulation of electrons to form a layer around the positively-charged object. Beyond the edge of the sheath, (the far field, so to speak), the alpha-emitter appears totally neutral, because charge has been conserved and has shielded any electrostatic interactions. Nimur (talk) 17:34, 21 December 2010 (UTC)

Poison mushroom

I've been a long time collector and eater of wild mushrooms. I definitely know how to identify the small variety of edible mushrooms I eat (Chanterelles and Porcini mostly) as well as a large number of poisonous or just undesirable varieties. So here is the question, why would mushrooms evolve toxicity? Some mushrooms have strong bitter taste/peppery or a foul smell despite being nominally edible, this I can understand as it definitely keeps me away The most deadly species like Amanita phalloides take many hours even days before causing symptoms so I don't imagine this would be an effective deterrent against being eaten, at least by large animals. Some mushrooms like the Fly Agaric are brightly colored and attractive like fruit but are also poisonous or at least unpleasantly hallucinogenic, why evolve this combo? The only things I can come up with are that these toxins are not evolved as a deterrent but are the byproduct of some other process or that they evolved as they culled the populations of animals who eat them and thus left only the phenotype who avoids their variety. --Leivick (talk) 09:13, 21 December 2010 (UTC)

The bright red Fly Agaric may be an example of warning coloration. Bright colors can serve to attract, as in flowers, or to repel, as in poison dart frogs. There is something to be said for the `by product' theory. For example, defensive compounds in mushrooms may be selected for because they decrease invertebrate predation (a large source of selective pressure). Mammals may not exert much selective pressure on a given species, but still experience deleterious effects from ingestion. SemanticMantis (talk) 15:08, 21 December 2010 (UTC)

The mushrooms an animal eats are just the "tip of the iceberg" and eating them does not normally kill the whole organism. Killing you in a few days is a completely adequate way of keeping you from being too much of a nuisance to the organism, and is an excellent way of stopping you from passing on any "ooh that looks tasty" genes to descendants. --Sean 15:19, 21 December 2010 (UTC)

It may also be worth bearing in mind that the toxic quality of any given fungus (or plant) may be coincidental. Not everything about fungi, plants and animals has evolved for protection. Richard Avery (talk) 16:02, 21 December 2010 (UTC)

The effective inhibition of RNA polymerase is something that will kill just about any living organism. Is it possible that these mushrooms (like Amanita) secreting amatoxins are actually doing so primarily as a means to compete with other fungi for their cool, damp, dark ecological niche? Remember that another genus of fungus – Penicillium – secretes antibiotics to ward off competition from bacteria. Does anyone know if the amatoxins are broadly toxic to other fungi (Amanita has presumably evolved to be resistant to its own toxins, but what about other mushrooms?) or to prokaryotes? If that's the case, then the effect on vertebrates (or even on invertebrate animals) may be a minor, almost coincidental one. TenOfAllTrades(talk) 16:04, 21 December 2010 (UTC)

This is OR. The distinctive colour and texture of the fly agaric is broadly similar to carnivorous plants that purposefully attract insects for the purpose of devouring them. Given the reason for its name, I wonder if the poison was developed in part to draw flies in, kill them, and so enrich the soil the mushroom was growing in. Just a guess on my part, so take that with a grain of salt. Despite being a featured article, our article doesn't seem to touch upon any theories regarding why these mushrooms are so toxic. Our article on mushroom poisoning also doesn't seem to touch on why mushrooms have evolved this defense, though it does say that relatively few mushrooms are poisonous, let alone deadly (though when they are...) Matt Deres (talk) 00:58, 23 December 2010 (UTC)

wet dreams

Are nocturnal emissions the male body's way of getting rid of stale sperm? If that isn't the case then how come women get wet during sexy dreams? —Preceding unsigned comment added by 188.186.237.190 (talk) 10:33, 21 December 2010 (UTC)

Wikipedia has an article about Nocturnal emissions. Their reported incidence is not often enough to match the continual production of sperm and so they cannot be called the male body's only way of disposal. Human sperm has a finite lifecycle estimated[18] as 42 days and if not ejaculated they are absorbed into the body at the vas deferens. After a vasectomy, the testes still produce sperm which are blocked and die in the vas deferens but this site warns that sperm beyond the blockage may survive up to seven months. The logic of the 2nd question is unclear because a women's vulva when sexually stimulated is lubricated by secretions from the Bartholin's glands, which has nothing to do with sperm production. Cuddlyable3 (talk) 15:14, 21 December 2010 (UTC)

Bear in mind that sperm constitute only a small proportion of semen, which is what is actually expelled; the bulk of the seminal fluids is produced outside the testes, primarily in the prostate gland (25-30%) and seminal vesicles (60%). Since the production of these fluids is independent of the testicles and does not turn on and off like a tap according to how much is already "loaded in the chamber", so to speak, periodic flushing of any excess unused by procreative or autostimulatory activities occurs in the form of nocturnal emissions, and I am fairly sure (though cannot find an immediate Wikipedia reference) that seminal fluid production and nocturnal emissions continue following the cessation of the sperm supply through vasectomy or even testicular castration.

Although women do not, obviously, produce seminal fluid, they do produce homologous fluids for lubricatory and perhaps other reasons, and the article on nocturnal emissions explicitly states, "women are also capable of having them." Similar considerations of excess production disposal presumably apply.

It is widely assumed (he weaselled) that during nocturnal emissions, it is the sensation of ejaculation/secretion that give rise to the "sexy dreams" rather than the reverse. 87.81.230.195 (talk) 01:15, 22 December 2010 (UTC)

It can also be widely assumed on the basis of diligent and exhaustingive empirical bio-studies employing the relevant gender-specific appendage activated manually in a turgid modality that the referred emission is obtainable with comparatively equal facility throughout the diurnal cycle and is therefore not necessarily correlated exclusively with the crepuscule or nocturnal phase of solar illumination absence so I have heard. Cuddlyable3 (talk) 10:35, 22 December 2010 (UTC)

You don't say. Do go on. -- Jack of Oz [your turn] 08:19, 23 December 2010 (UTC)

Straight back, diaphragm

If I sit with my back straight, does it make the diaphragm to be less restrained? It is a common explanation in meditation lessons, and it also makes intuitively sense (however, laying on the side also seems to be good for unrestrained breathing). Quest09 (talk) 14:32, 21 December 2010 (UTC)

Yes. When sitting straight up, gravity acts on the contents of the abdomen to pull them downwards. This makes the work of the diaphragm easier. When lying down on the back (supine), the abdominal contents press against the diaphragm, so the diaphragm needs to work harder. The diagnosis of "diaphragmatic paralysis" can be shown by measuring the spirometry ("lung capacity") when sitting up and lying down. In people with diaphragmatic paralysis, there is a big difference. Here is a report that remarks on this: "Paralysis of the diaphragm may be suspected in a patient ... in whom the vital capacity falls appreciably in the supine position." Axl ¤ [Talk] 10:44, 23 December 2010 (UTC)

c

Is it true that most oncologists (about 80%) when polled said they would not use chemo on their families or themselves? — Preceding unsigned comment added by Kj650 (talk • contribs) 16:23, 21 December 2010 (UTC)

I have not heard of it before but it seams reasonable given that most of them does not need it be curse they do not have cancer. --Gr8xoz (talk) 16:54, 21 December 2010 (UTC)

Presumably the OP means "as a treatment for cancer," durrr. --Mr.98 (talk) 17:11, 21 December 2010 (UTC)

I assume this is the origin of whatever statistic you are thinking of. The sample sizes are not huge, and the specifics of what kind of cancer are rather specific, and even then the number is not nearly as large as 80%. Additionally, the original "very high" (~75%) poll was over 20 years ago; even this one, which is well over 10 years ago, 64% said they would use chemo. I don't know what it would be today — medicine of this sort changes rather rapidly, and 10 years can make a big difference. --Mr.98 (talk) 17:14, 21 December 2010 (UTC)

It sounds like the typical position of some doctors like Matthias_Rath (a real doctor in Germany) who advocate to treat many diseases (including AIDS, diabetes, cancer) with vitamin supplements (that can be bought from them for a reasonable fee) rather than with the 'poisonous' mainstream treatment. Quest09 (talk) 17:31, 21 December 2010 (UTC)

I think that's a little extreme. There are significant numbers of oncologists who think that chemo is not the best treatment. That doesn't make them all quacks who believe in the miraculous powers of vitamin supplements. Chemo is an intense and possible detrimental form of treatment, and not the only one, and not necessarily the best one. Just because you aren't in favor of it doesn't mean you're in favor of quackery. Just because you're skeptical of a supposedly mainstream response doesn't mean you're necessarily in favor of the fringe response. --Mr.98 (talk) 19:43, 21 December 2010 (UTC)

I expressed myself wrongly. I don't mean that oncologist against chemotherapy are quacks. Chemotherapy might not be the best choice for some treatments. I wanted to say that quacks use phony statistics (like 80% of oncologist are against chemo), taken out of context to bash chemotherapy, and to offer you an 'alternative' like a high dosage of a vitamin supplement (which you have to buy from them, overpriced). Quest09 (talk) 20:30, 21 December 2010 (UTC)

It is important to recall that 'cancer' isn't one disease but many, and 'chemotherapy' isn't one particular treatment but a regimen tailored to the given patient and disease. It's extremely misleading to talk about 'chemo' as a single monolithic process or treatment. Different chemotherapeutic agents have very different side effects and different (often disease-specific) efficacies. Different patients will respond in different ways, and may find antinauseants and other supportive treatments more or less effective.

I would be very surprised if you were to find a practicing oncologist anywhere in an industrialized, first-world country who would flatly refuse chemotherapy for themselves or family members. Instead, what I am certain of is that you will find are oncologists who under some circumstances – of disease progression, life expectancy, and predicted marginal benefit – would opt not to undergo chemotherapy themselves, while still offering their patients a choice in similar circumstances. Consider a hypothetical (and grossly oversimplified) case involving a patient with advanced metastatic disease and a median expected survival time of one year. Suppose that an aggressive chemotherapeutic regimen will probably make the patient miserable for a month; the statistics say that on average his expected survival will be extended by two months and his chance at five-year survival will increase by some trifling amount. Good tradeoff, or not? There isn't a 'right' answer in some situations. TenOfAllTrades(talk) 01:38, 22 December 2010 (UTC)

I did a little bit of research into this a while ago and I think the critical statistic which is left out of the opponents of chemo therapy is "quality of life". Yes the pure "survivability" statistics for a lot of cancers treated with chemo seem far from stellar, and the chemo does make you feel miserable for a few months, but after that you might have a few years of relatively decent life. Without the chemo or radio therapy, the cancer will just grow unchecked and the pain and suffering it causes to those who didn't opt for therapy is what's NOT discussed by people who oppose chemo. Vespine (talk) 02:17, 22 December 2010 (UTC)

Chemotherapy has had some really amazing strides in the past few years. I'm going to go out on a limb and say if the hominid toxicity of 3-BrPA is anything like its toxicity in other mammals, the retiring baby boomers might not end up a net health care negative. Ginger Conspiracy (talk) 06:55, 22 December 2010 (UTC)

The colour of this morning's lunar eclipse

File:12 21 2010 lunar eclipse Orlando FL.jpg

Hi. Compare the two images, one from the latest eclipse (right) and the other taken during the eclipse of February 2008 (left). Both have a reddish hue, but the most recent one is darker. Is this due to the recent volcanic activity? Thanks. ~AH1^(TCU) 17:25, 21 December 2010 (UTC)

Before anyone jumps to conclusions, note that the February 2008 image is a digital composite of 1180 frames captured over a three-hour period. The amount of digital postprocessing required to synthesize and perform superresolution from more than 1,000 images is huge - so use caution before jumping to any conclusions about any characteristic of these images. (I was tipped off that something was a little "weird" when that image appeared to resolve lunar features that even I have a hard time shooting through my 200mm Newtonian reflector). The color and light intensity should be considered false color, and unless you have detailed information about the compositing method, avoid making inferences about true light intensity from it. Nimur (talk) 17:43, 21 December 2010 (UTC)

It's not totally unreasonable to say volcanic ash might affect how the moon looks from earth, but i don't see why you would only notice the effect during a lunar eclipse. Also, i don't think the rate of volcano eruptions is any different then in 2008 except maybe for maybe Eyjafjallajökull, that article shows the spread of the ash cloud so you should be able to tell if it's at least plausible that's what caused it. Hint: if you are in america: no; if you are Europe: maybe. Also relevant from the Volcanic ash article it states Volcanic ash particles have a maximum residence time in the troposphere of a few weeks. The finest tephra particles remain in the stratosphere for only a few months, they have only minor climatic effects, and they can be spread around the world by high-altitude winds. This suspended material contributes to spectacular sunsets. This confirms it's possible for the view of the moon to be affected for months after an eruption, but again I don't see why you'd only notice it during a lunar eclipse. Vespine (talk) 02:08, 22 December 2010 (UTC)

I have to say I don't know the answer, but I want to clarify some things. First, it's true that the recent eclipse is darker. Sky and Telescope gives a Danjon estimate of 2.5-3 for the 2008 eclipse and 2 for the 2010 eclipse (see http://www.skyandtelescope.com/community/skyblog/observingblog/15838502.html and http://www.skyandtelescope.com/observing/home/112248339.html), although these numbers are early estimates, and it's frustratingly difficult to find accurate brightness data on past eclipses.

Second, to answer Vespine, notice how the Moon appears red during totality, even though it's completely inside Earth's umbra. The only light that reaches the Moon during totality has to refract around the Earth, which means it has to travel thousands of kilometers through Earth's atmosphere. This light is red for the same reason sunrises/sunsets are red, and it's heavily affected by volcanic dust for the same reason volcanic eruptions cause brilliant sunrises/sunsets. Another way of looking at it is that some light from every sunrise and sunset on Earth is leaving the atmosphere, hitting the Moon, and reflecting back. So if you watched the recent eclipse from North America, part of the light that reached the Moon during totality would have passed through European skies, because the Sun was rising in Europe around that time. --99.237.234.245 (talk) 03:40, 22 December 2010 (UTC)

I admit I actually didn't consider the light passing through the atmosphere on the way to the moon, only passing from the moon back to earth. I thought since the atmosphere is only a tiny part of the diameter of the earth it would only have a very small impact on the light behind the earth, but refraction around the earth makes perfect sense when you explain it like that. Thanks. Vespine (talk) 05:38, 22 December 2010 (UTC)

I was not referring to the Icelandic eruption, but rather the more recent volcanic eruptions such as those at Mount Merapi, Mount Bromo and Mount Bulusan. ~AH1^(TCU) 17:26, 22 December 2010 (UTC)

Does sleep deprivation do permanent damage to the brain?

In the Wikipedia article it is mentioned that sleep deprivation has temporary effects. However, it is not mentioned if prolonged lack of sleep has any permanent effects on the brain.
So does it have permanent effects on the brain, or are they limited to them time spent under sleep deprivation? --87.68.248.194 (talk) 17:40, 21 December 2010 (UTC)

It might be difficult to study this, since clinical studies would be unethical, leaving us with only apocryphal cases. An even if a case is verified, would it be clear whether sleep deprivation caused the brain damage or the brain damage led to insomnia, and hence sleep deprivation ? StuRat (talk) 21:29, 21 December 2010 (UTC)

When you say prolonged lack of sleep do you mean staying awake for multiple days straight? Or do you mean not enough sleep each night? Ariel. (talk) 21:34, 21 December 2010 (UTC)

Sorry for not making it clear. When I say "lack of sleep" I mean staying awake for multiple days, not having little sleep at night. I would also like to know after what period of time the damage starts.--The Dimak (talk) 16:25, 22 December 2010 (UTC)

What about Stress (biology), which may accompany the sleep deprivation, causing effects on the organism which indirectly affect the brain. If the subject is under extreme internal or external pressure to finish writing some work, to finish a construction project, is in combat, is fleeing a menace, or is deliberately being kept awake by a captor, researcher or interrogator, would the prolonged release of cortisol or adrenalin directly affect the brain? The stress article mentions "ulcers, depression, diabetes, trouble with the digestive system or even cardiovascular problems, along with other mental illnesses." Some heart rhythm disturbances can cause blood clot formation leading to stroke. Digestive disturbances or diabetes can affect the blood chemistry, thus affecting the brain. Edison (talk) 17:20, 22 December 2010 (UTC)

The complete absence of sleep will eventually cause death. Brain damage could occur somewhere in this range. ~AH1^(TCU) 17:21, 22 December 2010 (UTC)

See: Fatal familial insomnia. Count Iblis (talk) 22:38, 22 December 2010 (UTC)

radio-metry and its uses in optical instrumentation

what is radiometry and its types uses in optical instrumentation — Preceding unsigned comment added by Mahi09 (talk • contribs) 17:58, 21 December 2010 (UTC)

Have you read our article on radiometry? Photometry_(optics) and Photometry_(astronomy) may be of interest, they refer to similar fields of study, but restricted to visible light. SemanticMantis (talk) 18:45, 21 December 2010 (UTC)

why does skin on your face get wrinkled and how does cream help?

why does skin on your face get wrinkled and how does cream help? 82.234.207.120 (talk) 20:44, 21 December 2010 (UTC)

The Wrinkle page might help explain why skin wrinkles. Most skin creams are just emulsions of oil and water and just provide a temporary moisturizing effect, making your skin appear less wrinkled. Most of the other compounds advertised in skin creams (Like vitamin A, E or other antioxidants) are not proven to do anything at the level of the amounts in the cream. -- JSBillings 21:12, 21 December 2010 (UTC)

The main effect is from ultraviolet exposure from sunlight. That's why you hardly ever see a wrinkled vampire. :-) StuRat (talk) 21:24, 21 December 2010 (UTC)

(...nor any other kind of vampire.) Botulinum toxin type A is BION an approved cosmetic for temporarily fixing skin wrinkles, see Botox#Cosmetic. Cuddlyable3 (talk) 21:44, 21 December 2010 (UTC)

Wrinkle cream helps those who sell it to make money through the vanity of others. HiLo48 (talk) 22:12, 21 December 2010 (UTC)

Basement temperatures

If an unheated basement or pit ten feet deep had a well-insulated roof, what sort of temperature would it have during the year in northern europe? I have been unable to find this kind of information. Thanks 92.15.15.127 (talk) 22:53, 21 December 2010 (UTC)

There are too many variables to give a definitive answer. Temperatures vary considerably throughout northern Europe. Deep pits tend to remain at a fairly constant temperature if there is no strong airflow to the atmosphere and there is good insulation, but there would still be some variation according to air temperature. The temperature would tend to follow that of the ground at a similar level if the walls and floor are uninsulated. There may be some areas where the pit would be below the freezing-point of water all winter, and others where it would become uncomfortably hot in summer. Dbfirs 23:29, 21 December 2010 (UTC)

My grandparents had a basement used as a pantry, just dug into the ground under their house, in a small town north of Warsaw in Poland. It's not northern Europe but I believe this was not uncommon practice all around Europe. The fact it had a house on it that was kept warm in winter would have played a big part in it never freezing. I don't think insulation, no matter how "good" without any source of heat would do something similar. Insulation just makes the escape of heat slower, but without a source, the heat would eventually escape. Earth it self is a very good insulator, in seasonally frozen ground I believe you wouldn't expect the ground to freeze more then a few to several feet deep so insulation might work, (it would probably help if was black to capture as much sunlight as possible, however in places of permanent frost like areas of Siberia and Alaska the ground can be frozen to hundreds of feet where I doubt any insulation would do very much. Vespine (talk) 01:51, 22 December 2010 (UTC)

Yes, it does very. For instance, at Cheddar Gorge, the caves stay at a steady 52°F -which is just right for maturing traditional cheddar.[19] The article about the Geothermal gradient explains more.--Aspro (talk) 10:36, 22 December 2010 (UTC)

It depends very strongly on how deep you are. Near the surface (like a basement) it's going to vary winter/summer - but once you go deeper it starts to vary less and less, basically the earth both insulates it and acts as a heat sink/source. Ariel. (talk) 11:22, 22 December 2010 (UTC)

A basic pit with a sealed roof will act like a "fruit cellar" and stay substantially above the outside temp in the northern winter. The dimensions and insulation level of the roof would be important factors in the actual air temperature. In the Northern US winter temps drop to perhaps -30F (-34C) and the frost line drops fairly deep. The basement footings or house foundation must be below this frost line to prevent "heaving" or movement due to soil freezing below the footings. This may be 5 feet (1.52 meters) in Minnesota. In northern Canada or Alaska there is permafrost. The pitwall would approximate the soil temperature, with the deeper portion at a more constant temperature, but in Minnesota, the soil down to 5 feet would be below freezing. Convection currents inside would circulate warmer air from the bottom up along the walls, so the soil or wall temp would be a bit warmer near the surface than in undisturbed soil of the same depth. In an abandoned house, especially if it is not sealed against air circulation and infiltration, and without the benefits of heating or the retention of solar heating, it is common for the frozen ground to break the basement walls and force them inward, near the ground. I have also seen basement wall broken where rainwater of snowmelt from the roof is allowed to dump next to the foundation, so pooled water next to the cellar wall freezes and expands and causes it the wall to break and tilt inward. I have seen the air temp in an unheated basement of a heated house in the northern US stay near freezing for days when the outside temp is many degrees below freezing. Edison (talk) 17:04, 22 December 2010 (UTC)

December 22

glowing embers on the road

For the past few months, whenever I drive home on the highway during the evening, I see the same strange thing on that little bit of road between the median and the fast lane: There, on the ground, is a small pile of what appears to be glowing coal embers - a pile of about ten roundish egg-sized things (in a small cluster the size of a bird's nest) emanating orange light. The first time I saw them, I thought they were actually coal embers. But because I've seen them in the same spot night after night, that can't be the case. Anybody have any idea? --Vectorflux (talk) 02:19, 22 December 2010 (UTC)

Where in the world? HiLo48 (talk) 02:49, 22 December 2010 (UTC)

Simplest explanation is a broken orange corner reflector. An idea: Make a careful note of where it is, then drive it during the day with a passenger with a camera. Have them try to take a high speed picture of the spot (make sure to set the exposure very low/fast to avoid blurriness, and physically pan the camera as well). Ariel. (talk) 05:29, 22 December 2010 (UTC)

Edit: Even more likely: Cat's eye reflector. Maybe a construction crew dumped some they didn't need? Or lost them? Ariel. (talk) 05:34, 22 December 2010 (UTC)

Due to the location on the road I suspect the objects are something that fell from a vehicle. The article Automotive lighting provides candidates such as turn indicators, brake lamps, sidemarker lights or reflectors, emergency lights and others. Someone might have lost their Christmas lights or possibly fluorerscent strip lights that served the 90's fad for under-car lighting. But could not the OP just go back and look? Cuddlyable3 (talk) 10:11, 22 December 2010 (UTC)

I, too, would venture to say it's a cat's eye reflector. There are varying designs; some are just one chunk of mirror whilst others have several small, circular reflectors and that sounds like what the OP saw. The best way to tell is to go back in daytime. Regards, --—Cyclonenim | Chat  18:36, 22 December 2010 (UTC)

Normal human body surface area = 1.73 m^2

How was 1.73 m^2 chosen as the "normal" human body surface area? If women typically have a BSA of 1.6 m^2 and men 1.9 m^2, 1.75 m^2 would seem a more likely choice unless there was a reason for choosing a less "round" number. Note that this normal BSA enters into the choice of units for renal function where the BSA corrected glomerular filtration rate (GFR) is given in mL/min/1.73 m^2. -- 119.31.126.66 (talk) 03:03, 22 December 2010 (UTC)

The origin of the 1·73-m² body surface area normalization: problems and implications by James G. Heaf in Clinical Physiology and Functional Imaging, Volume 27, Issue 3, pages 135–137, May 2007, sounds like it would tell me what I want to know. Now if only I can get access somewhere. -- 119.31.126.66 (talk) 03:27, 22 December 2010 (UTC)

Here's a relevant excerpt from Heaf: "In these evidence-based times, it is perhaps surprising to read how little documentation was required for the derivation of this figure, which first appeared in a study by McIntosh et al. (1928) (Fig. 2). On the basis of clearance studies of eight children and seven adults, the paper states: ‘Our experience confirms that of Addis and his colleagues. More constant normal values are obtained if one substitutes A (= surface area) in place of W (= weight) in the clearance formulae. We have found it convenient to use as a unit the surface area 1·73 square meters which is the mean of the areas of men and women of 25, estimated from the adjusted medico-actuarial tables of Baldwin and Wood published by Fiske and Crawford’. The Du Bois formula was used. The tables described young US citizens applying for life insurance. They were not referenced directly, but an adjusted version was published by Fisk & Crawford (1927). While these individuals had been examined fully clothed, every effort was made to reach as accurate an estimate as possible: the figures for men were ‘adjusted from the Medico-Actuarial Tables by subtracting 1 inch from height in shoes, and 5 pounds from weight in clothes’, and for women by subtracting 1·5 inches and 4 pounds, respectively, thereby giving us an insight into American clothing standards in the 1920s. There seems to be a minor error in the calculation: the correct figure is 1·72 m2."

References are McIntosh: PMID 16693840; Fisk: Fisk EL, Crawford JR. How to Make the Periodic Health Examination (1927) p. 345. Macmillan, New York.; Dubois: Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med (1916); 17: 863–871.

Interestingly, here's a description (from Heaf) of the method of Dubois: "The most commonly used formula for determining BSA is the Du Bois formula from 1916 (Du Bois & Du Bois, 1916). BSA was determined by tightly covering the patients with manila paper moulds. The moulds were then removed, opened and placed flat on photographic film. The film was subsequently exposed to light. Finally, the unexposed film was cut out and weighed. The BSA was derived from the weight by dividing by the average density of the photographic area." Hope this helps. -- Scray (talk) 05:09, 22 December 2010 (UTC)

Thank you! I am surprised that the original figure was actually expressed in square meters as opposed to square feet or square inches since the tables mentioned were apparently of US citizens described in pounds and inches. I had not realized that the medical / physiological community in the US had adopted the metric system so early. -- 119.31.121.84 (talk) 05:32, 22 December 2010 (UTC)

Based on the description of the gross approximations in the determination, it is hard to justify more than 2 significant figures. Edison (talk) 16:49, 22 December 2010 (UTC)

Arsenite color

Are they colorless? --Chemicalinterest (talk) 16:30, 22 December 2010 (UTC)

Yes, as long as the cation isn't coloured. So sodium arsenite is colourless, while copper arsenite is a well-known green pigment. The colour isn't the normal blue colour of copper(II), but the principle is the same. Physchim62 (talk) 16:34, 22 December 2010 (UTC)

Thanks. I needed the information for my work. --Chemicalinterest (talk) 17:24, 22 December 2010 (UTC)

Arsenite solubility

Are arsenites soluble? Sodium and potassium vs. copper arsenite. --Chemicalinterest (talk) 17:26, 22 December 2010 (UTC)Never mind. --Chemicalinterest (talk) 19:23, 22 December 2010 (UTC)

hear sine wave vs square wave

Is there an easy way that I can hear the difference in a sine wave and a square wave? For instance, is there a website or sound files that demonstrate the two, so I can listen to them? Bubba73 ^{You talkin' to me?} 16:41, 22 December 2010 (UTC)

A sine, square, and sawtooth wave at 440 Hz

Our article on waveforms actually has an example sound file; I've copied the link here. The addition of harmonics to the square wave gives it a much 'harsher' sound that the pure, single-frequency sine wave tone. TenOfAllTrades(talk) 16:54, 22 December 2010 (UTC)

Thank you, that was pretty much what I was looking for. It is a bit short and the square wave starts while the sine wave is still going on. Bubba73 ^{You talkin' to me?} 18:19, 22 December 2010 (UTC)

Puts on professor hat The square and the sawtooth waves are made by adding harmonics to the sine wave, which means the sine wave is actually present through the entire sequence. If one filters away their harmonics, the square and sawtooth waves turn into sine waves. ("Harmonics" means other sinewaves with frequencies that are whole multiples of the fundamental sinewave.) A proper mathematical sinewave keeps on going forever so any demonstration has to be cut short to be practical. Cuddlyable3 (talk) 21:34, 22 December 2010 (UTC)

For a more mathematically rigorous take on the matter, you can read the article Fourier series. It turns out that any periodic function can be treated as a superposition of multiple (perhaps infinite) sine and cosine functions. Buddy431 (talk) 21:50, 22 December 2010 (UTC)

OK, I understand that. To me, though, it sounds like two things - the sine plus something else, rather than one tone. Bubba73 ^{You talkin' to me?} 21:54, 22 December 2010 (UTC)

A square wave is $y=\sin x+{\frac {\sin 3x}{3}}+{\frac {\sin 5x}{5}}+{\frac {\sin 7x}{7}}+\cdots$

Power-of-2 harmonics step up the octaves and thus sound pleasant. Other harmonics can sound, well, unharmonic. Wolfram-Alpha square wave graph. CS Miller (talk) 23:07, 22 December 2010 (UTC)

And the triangular wave is $y=\sin x-{\frac {\sin 3x}{3^{2}}}+{\frac {\sin 5x}{5^{2}}}\cdots$    CS Miller (talk) 23:21, 22 December 2010 (UTC)

I guess it is those non-power-of-2 harmonics that makes it sound like two things. Musical instruments have a lot of harmonics, but not like the square wave. Musical instruments still sound like one thing whereas the square wave sounds like two. Bubba73 ^{You talkin' to me?} 00:41, 23 December 2010 (UTC)

Try this (lets you do sine and square at the same time) and this from [20] Ariel. (talk) 00:46, 23 December 2010 (UTC)

That is even more interesting. I started wondering about this because of my memory of the sound on my old Apple II. I thought it was probably a square wave. My memory is that it sounded like these square waves. Bubba73 ^{You talkin' to me?} 01:12, 23 December 2010 (UTC)

The cochlea has a profoundly different frequency response to waveforms with infinite first derivatives. Ginger Conspiracy (talk) 03:32, 23 December 2010 (UTC)

I imported the sound file of 1 second of sine, 1 second of square, and 1 second of sawtooth into a sound editor - and it is what it says (although there are some squiggles on the square wave). Bubba73 ^{You talkin' to me?} 04:12, 23 December 2010 (UTC)

The "squiggles" might be due to the Gibbs phenomenon. —Bkell (talk) 05:10, 23 December 2010 (UTC)

Looks like they are. Bubba73 ^{You talkin' to me?} 06:26, 23 December 2010 (UTC)

Space between particles

Considering the amount of space between subatomic and all other particles, what percent of the human body is empty space? — Preceding unsigned comment added by Daselter (talk • contribs) 19:30, 22 December 2010 (UTC)

If you only consider the gaps between atoms as empty space, you will get one figure, if you add the gaps between the nuclei and electrons, you will get a much higher percentage of empty space, and if you add in the space between quarks, you will get a higher figure still. It may well be that the answer is 100%, as no fundamental particle exists which is completely solid. (I don't believe the strings in string theory have a volume, although they do have a length.) StuRat (talk) 19:47, 22 December 2010 (UTC)

It should come up to 100% empty space. This is fundamentally the same as measuring infinite distance along a shoreline by using a smaller and smaller unit of measurement. -- kainaw™ 19:52, 22 December 2010 (UTC)

Or if you consider everywhere that a molecular orbital has non-zero probability as "occupied", then you get approximately 0% empty space (not counting the actual open spaces in the lungs and bowel, etc.). The question hinges as much on the semantic meaning of "empty space" as it does on the physical properties of the body. Dragons flight (talk) 20:07, 22 December 2010 (UTC)

Alas, we mortals live from Cantor dust to Cantor dust, the peculiar states of being nowhere dense. Cuddlyable3 (talk) 21:39, 22 December 2010 (UTC)

Let me explain why we can be 100% empty space, and yet still physically interact. When you touch an object with your finger, the atoms of your finger don't actually touch the atoms in the object. Instead the electromagnetic force of the atoms in your finger repels the corresponding electromagnetic force of the atoms in the object. It's just like two magnets that repel, and yet have empty space in between them. This is true when two atoms interact, it's true for an electron around a nucleus (it's all empty space, yet they interact), it's true for the nucleons in the atoms (except they also use the strong force), and it's true for the quarks inside each nucleon (but they use a different force). As far as anyone can tell electrons and quarks have no physical size (although they do have a wavelength). So where do you want to stop the line? If you draw a box around an atom it certainly has a size - and you can talk about the space between atoms. You can instead draw your box around the nucleons, or you can go larger and draw your box around molecules (like Dragons flight suggested). Ariel. (talk) 21:55, 22 December 2010 (UTC)

Isn't it something like 99.999999%? I forget how many nines. 100% is absurdly wrong, but very close. Ginger Conspiracy (talk) 23:05, 22 December 2010 (UTC)

From Point-like particle: "There is no experimental evidence for any of the elementary particles having spatial extent, and so they are usually considered to be point particles in the more general sense too...." Ariel. (talk) 00:35, 23 December 2010 (UTC)

That seems inconsistent with Planck length and the general idea of surface area corresponding to the force activity regions involved. Ginger Conspiracy (talk) 01:20, 23 December 2010 (UTC)

We don't have the ability to experimentally probe down to the planck length, and that sentence specifies experimental. One day we may find that electrons have internal structure (maybe by probing with neutrinos?) But, right now as far as we know they are point-like. I don't understand the second part of what you wrote. Ariel. (talk) 02:50, 23 December 2010 (UTC)

One analogy I've read, I'm not sure how accurate it is, if the nucleus of an atom was the size of a pea and you put it in the middle of a football field, the electrons would be orbiting around the boundary of the field. But as the above states, even the nucleus isn't really a solid. Vespine (talk) 23:26, 22 December 2010 (UTC)

I agree with Ariel that 100% "empty space" is a valid answer. There is no "solid matter" even at deepest level. It is all "energy". Of course, various other answers are possible, depending (as others have said), on where you draw the "boxes". Dbfirs 00:03, 23 December 2010 (UTC)

It will depend on our definition of solid. We have a variable volume dependent on pressure. In Human experience it means that the material resists human force. In that respect the human body is solid enough, but if the force becomes extreme enough you can make degenerate matter or neutron star matter. If pressure is reduced, then the body will evaporate and fill a much larger volume with water vapour and carbon dioxide! Graeme Bartlett (talk) 00:37, 23 December 2010 (UTC)

This was asked recently. The answer depends 100% on what you mean by "empty space". This term has no definition in modern physics, unless you define it as the absence of any field, in which case 0% of your body is empty space. It's not true that the fundamental particles are Planck-sized. Planck units are obtained by dimensional analysis and their physical significance, if any, isn't clear. -- BenRG (talk) 07:39, 23 December 2010 (UTC)

Arsenic trisulfide's NFPA health rating

Why does arsenic trisulfide, one of the less toxic arsenic compounds, have "4" for its NFPA health rating while arsenic trioxide, an extremely toxic arsenic compound, has "3"? --Chemicalinterest (talk) 21:40, 22 December 2010 (UTC)

This may be a MSDS error. Thank you for bringing it to our attention. Please forgive the research delay necessary to answer. Ginger Conspiracy (talk) 23:10, 22 December 2010 (UTC)

One of my purposes here is to find and report errors in chemistry articles. I hope you all don't get annoyed at my often posting here. In the course of my work at Simple English Wikipedia (using this Wikipedia as a source) I come across errors that I fix or ask clarification. --Chemicalinterest (talk) 23:50, 22 December 2010 (UTC)

One of the difficulties of the NFPA system appears to be that for many compounds the classification is left up to individual suppliers or users, and may vary somewhat depending on quantities in use or other application-specific conditions.

• Stanford synchrotron: Health: 3, Fire: 1, Reactivity: 0
• Temarry Recycling of Mexico: Health: 2, Fire: 0, Reactivity: 0
• HazMat data: for first response, transportation, storage, and security by R.P. Pohanish: Health: 3, Fire: 0, Reactivity: 0
• NOAA Cameo Chemicals database: Health: 3, Fire: 0, Reactivity: 0
• Fisher Scientific: Health: 3, Fire: 1, Reactivity: 0
• our own article (needs citation?): Health: 4, Fire: 0, Reactivity: 2

I suspect that our article is overstating the hazard. Ideally, someone should check the relevant NFPA guideline (NFPA 704) and report back to us. TenOfAllTrades(talk) 01:24, 23 December 2010 (UTC)

If there is a conflict in reliable sources, my opinion is that wikipedia should list the most stringent (and link to it), but also include links to sources with lower numbers, perhaps with a footnote mentioning the discrepancy. Deciding on a number ourself is reasonable to avoid sources that are probably errors, but would otherwise be a violation of wikipedia policy. We should only do that if we can't find any good sources. Ariel. (talk) 02:55, 23 December 2010 (UTC)

3-0-0 is a reasonable mid-point of the values listed above. 4-0-2 is ridiculous for this compound, and is clearly an outlier when compared with other sources. Physchim62 (talk) 09:51, 23 December 2010 (UTC)

December 23

ASB THE POLYMATH- opc question

What is the chemical composition of OPC drum coating solution i.e. CTL liquid? what can I use to coat OPC drums at home? —Preceding unsigned comment added by 117.242.112.81 (talk) 09:28, 23 December 2010 (UTC)

Two questions about lightning

1. Several years ago, I was in my apartment sitting in front of my computer. To my left was my stereo and to my right was my electric guitar and amp. Everything was plugged in. There was a sort of thunderstorm outside, nothing too heavy, but suddenly, there was a massive explosion of sound, but I never saw any light. As I sat there, time seemed to slow down, and in an extremely slow fashion, my entire body felt like it was expanding. I later described it to people as if every cell in my body had become a balloon and was being filled with a bit of air. I didn't move, either because I couldn't or because I wouldn't, and I honestly thought I was going to explode. But there was absolutely no pain. Just that uncomfortable feeling that lasted a few moments, and then my body "deflated" just as slowly. By the time I realized the situation was over, my computer was shut off. Everything was dead, and only the electric guitar still worked (half of the amp was destroyed, but it still worked on one insert). I've looked at the articles on positive lightning and lightning EMPs, and I've since done some research on Google, but I haven't been able to find any human recounts of physically witnessing an EMP. So my question is, was what I went through a lightning EMP of sorts? What was it doing to my body?
2. Back in the early 90s, I was backpacking through the US southwest during a storm. On the horizon, a strange bolt of lightning appeared. I cannot find an image of what it looked like (I've looked online for years), but imagine a straight bolt of lightning from sky to ground, but every few yards (massive estimation), the bolt expanded into a huge ball. There were three or four balls of light, like Christmas lights on a string, or popcorn on a necklace, within this bolt (or on this bolt), thus: ---O---O---O---O---. I keep running into ball lightning, but this wasn't a single ball of light moving around strangely. This was merely a bolt with a few glowing globs built in. The bolt acted like any bolt would: it appeared quickly, then faded quickly.

Any ideas on what it could be? Thanks for any help on this! Reflectionsinglass (talk) 09:28, 23 December 2010 (UTC)

Something like this: Transcranial magnetic stimulation may be related to what happened to you. This is interesting too: Ball lightning#Transcranial magnetic stimulation (and a nice synchrony with your next question). Regarding #2 the first thought that came to mind was birds :( - the bolt may have traveled from bird to bird before hitting the ground, and each bird burst into flame (I hope they died quickly :( Was the storm very sudden? I assume birds normally take cover during a storm. Another idea: Cosmic rays are hypothesized to stimulate lightning[21] strikes, maybe it was a meteor? It's possible that could do it too (but I've never actually heard or read anything to suggest that, so it's speculation only). Ariel. (talk) 09:47, 23 December 2010 (UTC)