Wikipedia:Reference desk/Archives/Science/2012 July 15

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July 15

CIELAB color coordinates

In the CIE Lab color space colors are represented by three parameters - lightness (L*) and a* and b* channels (the * is there to prevent confusion with the related Hunter Lab color space). L* is restricted to between 0 and 100 but the a* and b* channels, which may be positive or negative, are more complicated. Some references state they don't have a theoretically defined minimum or maximum value but note that certain combinations do not produce reaalizable colors. Others state that the minimum and maximum values depend on the color space being worked in - for instance this really gorgeous pdf explains that in the a* and b* channels are restricted to -100 to +100 if working in the CMYK space, but states that larger values can be attained in other spaces. On the other hand, this online color converter - if you inspect the javascript "under the hood" - restricts the a* and b* channels to -128 to +127. What I've not found anywhere is an explanation of how the limits on a* and b* vary, why it's exactly ±100 for the CMYK space ("by definition" is the obvious answer, but I've not seen it stated explicitly elsewhere and it isn't in the wiki article), or in general what magnitude of value is certain to be unrealizable (it's not obvious to me why that javascript only uses about ±128, but I can understand it's intuitively pointless stretching to ±500). Where could this information be found? ManyQuestionsFewAnswers (talk) 02:28, 15 July 2012 (UTC)

The article claims that its 2nd external link has "explanations" for the parameters. I think the first page of [1] may do a better job for you. You probably know that an 8-bit byte representing a signed integer has the range [-128, 127] while humans are more likely to use [-100, 100] for familiarity reasons. 71.212.249.178 (talk) 05:13, 15 July 2012 (UTC)

Thanks that's a nice link. Yes, the -100 and +100 (or -128 and +127) are obviously not completely arbitrary. But while that document has a very clear explanation of the conversion process, better than the Wiki article, I can't see an answer to my original question about what are the a* and b* co-ordinates' theoretical and practical limits (if such a distinction is meaningful!). It is clear that the human gamut extends substantially beyond a* or b* = ±100 (you can see that on this document on the diagrams from page 27 onwards) even if the CMYK space doesn't, and there are imperceptible "colors" beyond that gamut. From the diagrams it looks like b* can go above 130 and still lie in the human gamut so long as a* is approximately -30, and I can't discern where the lower boundary for b* or the boundaries for a* would lie. ManyQuestionsFewAnswers (talk) 13:35, 15 July 2012 (UTC)

There's no contradiction here. The first document says "The range of a* and b* never exceeds −100 to 100 in the cmyk color space." That doesn't mean that CMYK covers exactly that range, just that the CMYK gamut is nested in that range, as you can see in some of the images in that document. It's not considered especially important to be able to work with highly saturated colors (the colors at the edge of the human gamut). Various tools limit the gamut in various ways for various reasons—because they only care about limited-gamut output devices or because they want to store a* and b* as integers in one byte each, for example. -- BenRG (talk) 23:23, 15 July 2012 (UTC)

Yes, that all makes a lot of sense thanks, I presume the human gamut is limited by biological features that have to be measured, rather than being capable of theoretical calculation, and that explains the highly irregular shape? And yes I meant to say that the -100 to +100 was just upper and lower bounds for the a* and b* channels under CMYK, but additional restrictions apply (as you say not every pair of a* and b* values can be realized). It was the nature of the upper and lower bounds that I was particularly interested in rather the extra level of complexity about how they interact! From what you are saying, ±100 or ±127 is normally "good enough" because colors outside that range are so highly saturated that humans are not visually sensitive to them? ManyQuestionsFewAnswers (talk) 00:48, 16 July 2012 (UTC)

Humans are not visually sensitive to their differences, because incremental value changes in those outside ranges become vanishingly smaller changes in light's spectral envelope shape. 71.212.249.178 (talk) 02:06, 16 July 2012 (UTC)

Blood agents

According to page 72 of A Laboratory History of Chemical Warfare Agents, blood agents like hydrogen cyanide have a similar toxic mechanism to carbon monoxide. In this previous question, StuRat and Ratbone agreed that carbon monoxide poisoning is essentially painless; it just causes drowsiness, unconsiousness and then death. Yet the wikipedia article on blood agents cites "Blood Agents" by C. J. Walsh to claim that cyanide causes "...violent convulsions and a painful death that can take several minutes." So if they both work by the same mechanism, why is one painful and the other painless? 203.27.72.5 (talk) 05:43, 15 July 2012 (UTC)

This is outside my field, but I note that carbon monoxide posioning works by cripling the function of haemoglobin in the red cells of the blood (see http://en.wikipedia.org/wiki/Carbon_monoxide_poisoning), whereas cyanide posioning works by interfering with tissue cell mitochondria, and this would immediately affect brain cells (see http://en.wikipedia.org/wiki/Hydrogen_cyanide). So the mechanisms are not similar - they are completely different. This does directly contradict what Ledgard says on pages 72, 73. So I googled. See authoritative reference: http://emedicine.medscape.com/article/832840-overview#a0104 - this agrees with Wikipedia that hydrogen cynanide stuffs up mitochondria and gives details of how it does so. It is very well known, even amongst lay people, that CO affects red cells. Ratbone121.215.146.212 (talk) 10:36, 15 July 2012 (UTC)

Outside your field, but hit the spot none the less. Thanks very much Ratbone! 203.27.72.5 (talk) 11:01, 15 July 2012 (UTC)

Resolved

Yet another Higgs question

How many percent of physicists believed, prior to the recent discovery, that the Higgs boson would not be found by the LHC? How many percent believed that it didn't exist at all? It seems to me that although testing the claims of existing theories is important in science, the Standard Model's prediction of the Higgs is kind of like me predicting that the Sun will rise tomorrow. If it doesn't rise, that will be an earth-shattering discovery, but few people seriously expect it to not rise. Is this a valid characterization of the Higgs boson, or am I way off? --140.180.5.169 (talk) 06:40, 15 July 2012 (UTC)

The Higgs is necessary if the Standard Model is correct. But we already know it's at best flawed, so there is no general theoretical requirement for the Higgs tto exist. — kwami (talk) 07:30, 15 July 2012 (UTC)

Apparently the discovery of the Higgs boson cost Stephen Hawking a $100 bet. 203.27.72.5 (talk) 07:21, 15 July 2012 (UTC)

I don't get it. The particle has not been confirmed to have the behaviour expected of the Higgs, so why has Hawking admitted defeat? — kwami (talk) 07:26, 15 July 2012 (UTC)

Because he's noble in defeat. And because he's reasonably sure that if it turns out later they've discovered some unpredicted particle and the Higgs is still at large, then he will still be able to get his money back from the other guy. 203.27.72.5 (talk) 07:43, 15 July 2012 (UTC)

It has to do with Hawking's old idea about information loss due to Hawking radiation, see here. It leads to the conclusion that you can never detect any fundamental scalar particle. Count Iblis (talk) 15:34, 15 July 2012 (UTC)

We don't really have any model of the world in which the sun doesn't rise tomorrow. There are several Higgsless models. Dauto (talk) 18:41, 15 July 2012 (UTC)

Some people do. W203.27.72.5 (talk) 22:29, 15 July 2012 (UTC)

At least some of these "Higgsless" models have a spin-0 particle that behaves like the Higgs. It's just not a fundamental particle, but some kind of composite or weird non-particle state. The article claims "All of the alternative mechanisms use strongly interacting dynamics to produce a vacuum expectation value that breaks electroweak symmetry", which (if it's true) means that they all have a field like the Higgs field. Given that, I'd think it would be hard to prevent perturbations in that field behaving like a Higgs boson, though it might be easier to make the mass of the quasi-Higgs high enough that it couldn't be found at the LHC.

As for Hawking, even if he was confident in the correctness of that paper (which I doubt) it only applies to a fundamental Higgs, so he could still lose to a composite Higgs. I think he probably bet against the Higgs because it's the more interesting outcome, and didn't really expect to win. -- BenRG (talk) 23:47, 15 July 2012 (UTC)

Preserving body part for future genetic sequencing

How do I preserve a part of myself as of today so that it can be genetically sequenced when technologies become cheaper, more available, and more reliable? Also, is it possible to sequence the skeletal remains of a person? Many thanks. 180.254.88.42 (talk) 08:00, 15 July 2012 (UTC)

The bone marrow could be sequenced, until decayed, which, depending on conditions, could be under a year or up to several thousand years. The easiest way to preserve your DNA would be to pull a hair, with the root, seal it in a sterile container, and freeze it. Be sure to label it. StuRat (talk) 08:46, 15 July 2012 (UTC)

A researcher in my lab stores stuff in an ethanol water mixture on the field and in the lab for Later DNA sequencing. Don't know the ratio though.Staticd (talk) 11:02, 15 July 2012 (UTC)

Collecting a sample with a buccal swab (basically rubbing the inside of your cheek with a Q-tip) is another non-invasive technique, that according to this page, at least, is generally considered preferable to collecting a hair sample. If you're willing to spend a little bit of money, there are companies that are set up to help you preserve a DNA sample. Some will do things like save your sample for you at -80° C, which will presumably make the sample last longer than in a home freezer, and some companies sell chemicals for preserving the DNA sample at room temperature. To find those companies, the link above is a good place to start, or just google "DNA sample preservation". Red Act (talk) 19:01, 15 July 2012 (UTC)

The simplest way, as StuRat says, is a few strands of hair. But let me point out that your DNA sequence as of today is the same as your DNA was when you were born and will be when you die. It could in principle be used to clone you, but it does not contain any information about who you have become since you were born. Looie496 (talk) 04:07, 16 July 2012 (UTC)

Actually, that's not true for all your cells, some of which undergo permanent gene recombination. The memory B cells of the adaptive immune system actually undergo V(D)J recombination to permanently alter the cell's DNA. Memory T cells and certain NK cells also undergo various forms of permanent genetic recombination. Smallman12q (talk) 13:20, 16 July 2012 (UTC)

The problem with hair is that it can be unreliable. If you do go with hair samples, you have to be careful to collect hairs that still have the root attached, i.e., the hairs have to have been plucked out of the scalp. Hair shafts alone will not do, so the hair found in your hairbrush will probably not be adequate, unless there happen to have been a few hairs that have been plucked out from aggressive brushing. About 40% of hair samples submitted for DNA paternity testing, for example, fail to be adequate for that purpose.[2] Rubbing a Q-tip on the inside of your cheek is also quite simple, it doesn't hurt like plucking a hair out of your head does, and it's a more reliable way of collecting a usable DNA sample. Red Act (talk) 18:41, 16 July 2012 (UTC)

I considered suggestion that, but was concerned that the bacteria also collected in that manner would lead to decomposition of the DNA over the years. Freezing would help, but, between crappy frost-free refrigerators that thaw the food frequently, and power failures, significant decomp could still occur. This seems less likely with a dry, freshly plucked hair, with the root intact. StuRat (talk) 21:01, 16 July 2012 (UTC)

Sticky robots

My son has got a bathtub toy which consists of robot shaped parts that stick to the tiles when wet. The parts are very lightweight and made of some foamy material. I was wondering about the physics behind it. Explanations can be as technical as necessary. Thanks. bamse (talk) 08:03, 15 July 2012 (UTC)

Can you provide more details? Maybe the brand so we can google it and see what you're refering to? I'm just having a hard time imagining it looks like, not having any kids (or their toys) myself. 203.27.72.5 (talk) 08:23, 15 July 2012 (UTC)

Could it contain tiny suction cups ? They tend to work much better when wet. StuRat (talk) 08:42, 15 July 2012 (UTC)

I guess these are robot-shaped versions of the more common foam bathtub letters (sample ad). The adhesion mechanism is probably a mixture of static cling (as used in vinyl decals) and soap residue. Unfortunately our article on static cling is poor, and doesn't even attempt to explain how static cling decals work. --Heron (talk) 09:39, 15 July 2012 (UTC)

Does static cling work on wet objects ? StuRat (talk) 09:41, 15 July 2012 (UTC)

Cling wrap certainly does work with wet food products, so I guess it might. 203.27.72.5 (talk) 09:50, 15 July 2012 (UTC)

Be careful not to confuse cling wrap with static cling. Cling wrap sticks by means of adhesive additives (see madsci.org [3] and [4]), while static cling is a purely electrostatic effect. --Heron (talk) 11:17, 15 July 2012 (UTC)

Hmmm...my physics lecturer said once that cling wrap was the only example of a useful purpose of static electricity in everyday life. Looks like he was confused. 203.27.72.5 (talk) 11:24, 15 July 2012 (UTC)

• Pretty sure it's just adhesion due to the thin film of water, which is highly cohesive with itself, and also adheres to the foam (due to high surface area), as well as the tile. Water is actually a good adhesive, if the right material properties are met (high surface area, small forces). Here's the same phenomenon: put a toothpick on a surface, put three small drops of water on the toothpick, then another toothpick on top. If you are careful, you should be able to pick up the top toothpick, and the bottom one will stick to it via water adhesion. Further links on water adhesion here: [5] and here [6]. (I would not personally use "static cling" to refer to this effect, even though the adhesive/cohesive forces in water have to do with electrostatic forces on the molecular level...) SemanticMantis (talk) 15:48, 15 July 2012 (UTC)

Thanks for all the replies. Indeed these seem to be like the bathtub letter mentioned by Heron. No suction cups (unless they are microscopic), they stick both on the bathroom tiles and on the bathtub and work with plain water and soapy water. If they get dry, they fall off the wall, but can be reused if made wet. The adhesion/cohesion explanation sounds very plausible to me. bamse (talk) 19:01, 15 July 2012 (UTC)

Lightning captured in nuclear explosion photograph

I came across this popular image shown in many topics related to nuclear weapons. I have noticed there is wierd lightning on the center of the picture, connecting ground and skies, and I can't manage to find out what caused it. What is that lightning ?

http://en.wikipedia.org/wiki/File:Upshot-Knothole_GRABLE.jpg

95.105.133.125 (talk) 08:57, 15 July 2012 (UTC)

vertical smoke flares which are used to observe the shock wave --Digrpat (talk) 09:07, 15 July 2012 (UTC)

Thanks, I tought it's lighning :D — Preceding unsigned comment added by 95.105.133.125 (talk) 09:41, 15 July 2012 (UTC)

Name the Lamp - please!

Yeah, that's a ... humh ? A Gooseneck lamp !

What is the English word for this office lamp with a "swan neck" backbone (you can move it in any direction - and it stays). Grey Geezer 09:30, 15 July 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)

The bendy bit is called a gooseneck, so the lamp is called a gooseneck lamp. --Heron (talk) 09:34, 15 July 2012 (UTC)

I have a floor lamp like that, and just call it the "adjustable lamp". StuRat (talk) 09:35, 15 July 2012 (UTC)

I'd call it a gooseneck lamp as well. Though I'm not sure what this has to do with science. Dismas|^(talk) 09:45, 15 July 2012 (UTC)

Gooseneck - sure! Thanks! Case closed. Grey Geezer 10:39, 15 July 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)

follow-up question from someone else What is the most common manufacturing technique used to make a lamp like this possible? What's in the shaft? 69.243.220.115 (talk) 13:38, 15 July 2012 (UTC)

The stem of the lamp consists of a series of rings that act as little joints which allow each ring to articulate and move a small amount, say a millimeter. With lots of little joints on lots of little rings, the whole thing bends and twists. --Jayron32 19:39, 15 July 2012 (UTC)

(edit conflict) One common construction is to have a spiral of metal (or sometimes plastic) in which each winding overlaps and links (but is not rigidly attached) to the adjacent ones. The whole thing can flex because the amount of overlap can change a little at each winding. DMacks (talk) 19:40, 15 July 2012 (UTC)

Looking at mine, it seems to use rings, not a spiral. There must be some type of catch on the inside of each ring to keep it from sliding completely off the adjacent ring. StuRat (talk) 20:55, 15 July 2012 (UTC)

Mine appears to use double rings, one set on the outside, and one on the inside, like so:

 ______
 \    / 
          OUTER RING CROSS SECTION
 /____\

 /____\
 ______   INNER RING CROSS SECTION
 \    /

 ______
 \   //___\
     ______   ASSEMBLY CROSS SECTION
 /___\\   /

Or maybe the outer rings and inner rings are combined into one, like so:

 ______
 \    /____\
      ______    CROSS SECTION
 /____\    /

I do find myself wondering how they assemble such a thing, though (must involve folding down some flaps, forcing rings together, then folding the flaps back up, like in a molly bolt):

 ______
 \    /___/\ <- Fold down flaps
      ______    
 /____\   \/ <- Fold down flaps

StuRat (talk) 21:12, 15 July 2012 (UTC)

The patent literature suggests that "interlock gooseneck" is produced by crimping, as are variants. 71.212.249.178 (talk) 05:32, 16 July 2012 (UTC)

Strength training

What are the advantages and disadvantages of classic weights/resistance training with cardio vs circuit training? 176.27.222.99 (talk) 13:03, 15 July 2012 (UTC)

We can't give medical advice, and this is a perfect example why. The answer depends strictly on several separate results of a physical examination. Ask a professional trainer certified in exercise planning. 71.212.249.178 (talk) 19:41, 15 July 2012 (UTC)

Im not asking for medical advice. Im asking for a scientific answer to my question which is purely academic. Its up to the person answering to give an academic answer rather than medical advice, which cant be hard since im asking a very generic question. A question asking for medical advice would be alot more specific. 176.27.222.99 (talk) 20:16, 15 July 2012 (UTC)

This is hardly a medical advice question... although the usual caveats about checking with your doctor before starting an exercise regimen... There's a lot of discussion and debate about cardio versus strength training. Generally strength training is going to help build fast twitch muscle and from an aesthetic standpoint, create more definition and possibly (depending on a lot of things) size. Cardio will improve other aspects of your fitness.

There's a lot of dogma around exercise and nutrition and so you may hear people who are absolutist about their particular position. Ultimately you have to decide for yourself. Shadowjams (talk) 20:33, 15 July 2012 (UTC)

Moved discussion on whether or not this is a request to medical advice to somewhere more appropriate. W203.27.72.5 (talk) 02:30, 16 July 2012 (UTC)

Alcohol absorbition from mouthwash

What amount of the alcohol in mouthwash is absorbed by the mucosal membranes etc in your mouth? Assume the mouthwash is 20% a.b.v. and that the mouthwash is swirled around your mouth for 30 seconds (or show that these are unreasonable assumptions)— Preceding unsigned comment added by Egg Centric (talk • contribs)

I'll assume this is not a medical question and not a homework question. I found no useful links at Google search. Wikipedia's info in the buccal membrane inside the mouth seems very sketchy, with only a passing reference in Oral mucosa, which is a very short and uninformative article. Someone studying dentistry or oral surgery could perform a real service by improving our coverage of the buccal membrane and oral mucosa in general. Caffeine gets readily absorbed through the oral mucosa, and sugar is also absorbed slowly. As for alcohol, all I found on the web was that drinking alcohol regularly for a long time can lead to cancer of the oral mucosa, as can using a high alcohol mouthwash, even without swallowing alcohol. Edison (talk) 17:43, 15 July 2012 (UTC)

A source found at Google books says that "small amounts of alcohol may be absorbed through the buccal mucosa" without giving a formula for calculating the precise quantitative answer to your question. Edison (talk) 17:50, 15 July 2012 (UTC)

It depends on the proportion swallowed. 71.212.249.178 (talk) 19:47, 15 July 2012 (UTC)

• At least in the United States where I live, any mass-produced mouthwash uses denatured alcohol, so you can't get drunk off of it without poisoning yourself. --M@rēino 21:09, 16 July 2012 (UTC)

Is aging slowing as life expectancy increases?

Life expectancy has increased greatly over the last century. However, has aging slowed down at all? I know in the middle ages for example people were considered grown and ready for marraige at around 15 years of age. Were these 15 years olds more developed than modern 15 year olds? Has puberty and growth slowed down at all?

Has menpopause got any later? What are the reasons for this? Is people in developed countries having children later an evolutionary pressure, and how do you expect this will affect evolution of H. sapiens in the near future?--178.167.159.126 (talk) 16:51, 15 July 2012 (UTC)

This is based on hearsay, but people are apparently reaching puberty faster now than before. 109.97.146.146 (talk) 17:39, 15 July 2012 (UTC)

There is evidence that women reach menarche (age of first period) earlier by 2 - 3 months per decade. This page has some interesting cross-cultural graphs. As to why this should be, I would speculate that it is a combination of factors: improved nutrition and healthcare being a large factor, and possibly oestrogenic chemical environmental residues, whose impact is still unknown. --TammyMoet (talk) 17:55, 15 July 2012 (UTC)

I can't access your article: do they control for quality of nutrition? I came across a study a while back that showed that, among upper-class girls (ie. those who can be assumed to have reliable access to quality food), the age of menarche hasn't changed in the past 400 years. --Carnildo (talk) 01:28, 18 July 2012 (UTC)

(ec) Yes, puberty is getting earlier. The biggest factor causing this is apparently less starvation, as one of our starvation responses is to delay the onset of puberty. StuRat (talk) 17:56, 15 July 2012 (UTC)

One of the things about life expectancy that is a bit of a fallacy is that people used to die in their 40s and 50s, and only recently began living into their 80s and 90s. This is true to a point, that is people do live longer, a bit more than they used to, but it isn't as simple as that. Much of the increase in life expectency in modern developed nations actually comes from two situations:

a) Children living to maturity

b) Women surving childbirth

In his book A Little Commonwealth, John Putnam Demos did a detailed demographic study of Plymouth Colony. Now, this was a 17th century colony of people, mostly first generation imigrants, living in a society without modern medicine and modern nutrition and the like. What he found was that males who reached their teens lived nearly as long in the 1600s as they do today, as did women who made it to their 50s. That is, if a man could make it out of childhood, or a woman could make it to menopause, their was not a dramatic difference in lifespan 400 years ago than today. It turns out the risks to long life are mostly childhood disease and pregnancy complications. If you made it through those landmark events, you stood as good of a chance of living just as long then as now. So when you see lifespan figures from the past, understand that the numbers are skewed a lot by those issues. Seeing that, at some point in history the average lifespan was, say, 50 years old doesn't mean that lots of people died in their 40s. What it means is that lots of people died as young children and it dragged the average down a lot. Now, there is a big caveat in Demos's study and that is that the situation is very different in cities, where sanitation really lowered lifespans of people. Plymouth was a small, agrarian society where the problems of urban sanitation don't create the close proximity necessary to spread epidemic disease like black plague, cholera, typhus, and the like. If there are three things which have raised life expetency more than any other in the modern world it has probably been, in order a) vaccinations against childhood disease b) prenatal care and c) urban sanitation. Everything else has made small, incremental advances, but those are the three biggies. As far as directly answering the question regarding age of maturity at both ends of life (puberty and old age); a lot of that is cultural as much as anything else. As others have noted, for health reasons it seems people are reaching puberty earlier than before, but for nearly all of history 15 years old has been an age when a person has reached biological sexual maturity. That does not mean that a person is emotionally or culturally considered ready for adulthood, parenthood, or sexual activity. Many of those things are determined by one's culture: in one place and time, 15 year olds are considered full adults, while in other places and times the age may be younger or older. --Jayron32 18:43, 15 July 2012 (UTC)

Specifically, water treatment and sewage treatment seemed to be absolutely critical to increasing the average lifespan, by stopping the spread of water-borne diseases.

I believe many measures of life expectancy also exclude infant mortality. StuRat (talk) 20:37, 15 July 2012 (UTC)

They do. But that only removes people who die before their first birthday. 5 year-olds are not infants, and many of them died of things like measles and scarlet fever and polio, diseases that in the modern developed world have been essentially eradicated by vaccines. --Jayron32 03:07, 16 July 2012 (UTC)

This is certainly the argument of e.g. Ivan Illich, who felt that improvements in sanitation were a larger factor in improved human life expectancy and wellbeing than the medical profession had provided. (Not saying I agree with him, am curious why he didn't rate progress in things like vaccination so highly, but that what StuRat and Jayron say is sensible.) ManyQuestionsFewAnswers (talk) 00:38, 16 July 2012 (UTC)

There are some specific aspects of aging which now seem to happen more slowly:

1) Skin aging. Due to spending less time in the sun, wearing more clothes, using sunscreen, moisturizers, etc.

2) Dental wear (distinct from other dental problems). Food used to contain bits of sand and such, which wore down the teeth, but with modern processing, our food doesn't contain this. Also, people formerly used their teeth as general tools, for cutting materials and such, but now we use external tools (although I have to admit to occasionally biting open a blister pack/clamshell, like the one containing the scissors needed to open blister packs/clamshells :-) ). StuRat (talk) 20:46, 15 July 2012 (UTC)

I'm pretty skeptical of number 2 — do you have a source for that?

To add my own speculation on top of speculation, I think a lot of people show less "visible signs of aging" than you see in movies of people of the same age in, say, 1940 or 1950, in large part because most people now don't smoke. But I don't have a source for that (would be interested to know if someone does). --Trovatore (talk) 22:18, 15 July 2012 (UTC)

"Foragers tend to have a lot of wear at a young age, while later agriculturalists have less wear." [7]. StuRat (talk) 01:29, 16 July 2012 (UTC)

"This type of wear may have resulted from using the teeth to soften cedar bark fibres for the weaving of blankets." [8]. StuRat (talk) 01:32, 16 July 2012 (UTC)

The question was about trends "over the last century". There weren't many foragers left by then, at least in the developed world. --Trovatore (talk) 01:31, 16 July 2012 (UTC)

The OP didn't ask us to limit our responses to the developed world (they did mention it in one question, but I took that to mean they are only asking about the developed world with respect to age at childbirth). StuRat (talk) 01:34, 16 July 2012 (UTC)

I think there were very few foragers left anywhere in the world, at least percentage-wise. The hunter-gatherer lifestyle does not support large populations. --Trovatore (talk) 01:37, 16 July 2012 (UTC)

Chimmney-like thing in boats

How is called this chimmney-like thing that are found in many boats?--90.165.112.194 (talk) 18:12, 15 July 2012 (UTC)

I think it is normally called a 'ventilation cowl' - see here for some information on how they are used: http://www.generalcargoship.com/ventilation-of-cargo.html

It's called a "Dorade box", and it's for allowing air in below deck while making sure no water gets in. Dominus Vobisdu (talk) 18:27, 15 July 2012 (UTC)

Why is it such a boat cliche to have the tube bend over to protect from rain when chimneys on land often a little hat over it? (though Essex House does do the flue turned over thing) Do they ever put a jog in the flue so the rain lands in a sump? I thought of that when I was ~13. Sagittarian Milky Way (talk) 23:57, 16 July 2012 (UTC)

The 90-degree bend is so that the forward motion of the ship will force air into the intake, not to keep rain out. --Carnildo (talk) 01:36, 18 July 2012 (UTC)

How long does it take for wind turbines to pay for themselves?

The House of Lords says 1.1 years but that doesn't include profit, taxes, shipping, or salaries. Can anyone get this NREL spreadsheet to say? It has Excel macros so it's not working for me at the moment. 71.212.249.178 (talk) 19:52, 15 July 2012 (UTC)

That first link also doesn't seem to include the land purchase price, which can be significant for a large wind farm (especially if they need a buffer zone, as neighbors probably don't want massive windmills right on their fence). StuRat (talk) 20:32, 15 July 2012 (UTC)

I hope only the footprints of the turbines take land area economically, e.g. from agriculture. 71.212.249.178 (talk) 22:27, 15 July 2012 (UTC)

Your question doesn't make sense to me. Don't they pay for themselves by generating profits? W203.27.72.5 (talk) 22:19, 15 July 2012 (UTC)

Yes, but in how much time? Can you get the spreadsheet to work? I better fire up windoze. 71.212.249.178 (talk) 22:27, 15 July 2012 (UTC)

The House of Lords document is not about dollar terms. Building anything requires energy, energy for melting aluminum, mining the metals, shipping parts, etc. The document tells the reader how much energy is required to build each type of plant, and how long the then built plant would have to operate to create the amount of energy required to have built it in the first place. Unique Ubiquitous (talk) 22:39, 15 July 2012 (UTC)

That document is looking at it in a really useless way. For a start, you get that energy back in the future, so it's worth less to someone now than the energy that's all going into it. W203.27.72.5 (talk) 01:06, 16 July 2012 (UTC)

Also, if that's the case, then taxes, salaries and profits don't cost any energy (though they may be used to spend on things that do). W203.27.72.5 (talk) 01:08, 16 July 2012 (UTC)

Agreed, the given statistics would only be of importance where energy was very scarce and needed to be direly mananged. And to Sturat, wind turbine land is available for dual purposes, though even if it weren't a wind farm would only consume as much land as an equally productive coal plant - and thats excluding the land required for the mining. Unique Ubiquitous (talk) 01:21, 16 July 2012 (UTC)

I've been to a wind farm and they told me each turbine lasts about 20 years, and the first 10 years are spent paying for itself.--92.251.194.63 (talk) 02:01, 16 July 2012 (UTC)

Hm, I got two years for a $1,000,000 2MW turbine from the NREL spreadsheet above, but this windustry.org spreadsheet suggests that a pair of GE-financed 1.5 MW turbines costing $6,300,000 pay for themselves as soon as the contracts are signed.

"a standard two-megawatt turbine costs about 2.75 million euros to build and earns about 275,000 euros a year for the sale of electricity at the market rate. But that revenue can rise to about 500,000 euros with special state-mandated incentives paid by utilities as a premium for renewable energies. In many countries, wind producers are receiving feed-in tariffs -- premiums above the market rate as a bonus for renewable energy." (NYT, 2009)

"A turbine with a feed-in tariff contract receives 13.5 cents a kilowatt hour, or $135 a megawatt hour for its output. (One megawatt is 1,000 kilowatts.) A two-megawatt turbine running at full speed, 24 hours a day for a year, would therefore produce 17,520 megawatt hours of power. Assuming it operates at 35 per cent capacity, in the real world it will produce about 6,132 megawatt hours. At $135 a megawatt hour, that means revenue of $827,820 annually. Assuming a more conservative capacity of 27 per cent, it would generate revenue of $638,604. Offsetting the revenue are very high capital costs. The cost of purchasing, erecting, financing and connecting a turbine runs at about $2,500 a kilowatt of capacity, although prices are declining and in some cases are now below $2,000 a kilowatt, according to CanWEA. That means a two-megawatt turbine costs $4 million to $5 million to install. Included in the cost is rent of more than $19,000 a megawatt — paid to the landowner where the turbine is erected. That works out to about $38,000 annually for a two-megawatt turbine." (Toronto Star, 2011)

http://bloomberg.com/energy suggests $135/megawatt-hour is way too high even in Canadian dollars. I haven't seen electricity over 35 USD/megawatt-hour all summer, even in Houston. Perhaps the much more expensive Canadian turbines produce high grade electricity. 71.212.249.178 (talk) 04:48, 16 July 2012 (UTC)

Not sure what those Bloomberg numbers mean as the average residential price of electricity in the US is $119.50/mWh [9]. Unique Ubiquitous (talk) 05:35, 16 July 2012 (UTC)

Ah, that's the difference between wholesale and retail, and explains the Canadian figures. Thank you. The mark-up supposedly pays for grid transmission, local distribution, maintenance, and customer service. The Canadians probably pass the retail along as a subsidy after taxing the heck out of the turbines. I'm guessing there could be quite a bit more competition in the turbine marketplace, but they are being installed as fast as manufacturers can make them. 71.212.249.178 (talk) 05:57, 16 July 2012 (UTC)

The House of Lords report is based on energy return on energy invested: ie. it takes 1.1 years for the average windmill to generate as much energy as went into producing it. --Carnildo (talk) 01:42, 18 July 2012 (UTC)

Hydrogen critique?

Even liquid hydrogen has less than a third the energy density of gasoline.

So, I've been really interested in hydrogen vehicles recently, and if one day in the future I can afford one, I hope to buy one (which might be a challenge living in Canada, but one step at a time). One thing I've noticed though, in the criticism section of our Wikipedia article is that critics claim that "hydrogen vehicles will emit more carbon than gasoline vehicles (in their lifetime)". How is this so? Is it because the number one way that companies produce hydrogen is through using fossil fuels? Electric cars face the same thing, except worse, considering the source of their electricity mainly comes from fossil fuels too. But wouldn't a simple solution to harnessing hydrogen be electrolysis, perhaps using solar electricity (which can even easily be done at home)? And what other problems (besides cost) could the hydrogen car face? Thanks, 64.229.5.242 (talk) 19:59, 15 July 2012 (UTC)

Storage for hydrogen is remarkably difficult. It embrittles metals in which it is stored or pressurized. There are some ceramics virtually impervious to damage from this, and systems to compensate for it, but they are fragile, heavy, and bulky and thus unsuitable for transportation. Hydrogen also has a colorless flame which is often considered a safety hazard. You may be interested in http://windfuels.com, http://airfuelsynthesis.com, page 28 here and the conclusions of this paper. 71.212.249.178 (talk) 20:24, 15 July 2012 (UTC)

As far as creating hydrogen at home using solar power, this wouldn't be practical. A huge array of solar panels would be needed, since solar cells are rather inefficient. StuRat (talk) 20:18, 15 July 2012 (UTC)

Solar is expected to be competitive with wind after 2020, depending on how well Makani Power does. 71.212.249.178 (talk) 20:24, 15 July 2012 (UTC)

One man a few years ago had an array of solar panels on his roof, and it could easily power his house. I doubt that a "large array" would be needed to split water, which only needs at least 1.23V. 64.229.5.242 (talk) 20:54, 15 July 2012 (UTC)

Voltage has nothing to do with it. You can get any voltage you want out of an arbitrarily small array of solar panels, but then the current is so low that won't generate hydrogen at a sufficient rate to do anything with it. There's also the problem of liquifing the hydrogen once you generate it. If you're burning the hydrogen as the BMW Hydrogen 7 does, you will only get something like 30% of the generated solar power back as kinetic energy in the movment of your car. If it uses hydrogen fuel cells, then it should be about the same efficency as an electric car (since you're basically just using the generated hydrogen as a battery. The solar panels themselves take huge amounts of energy to create (due to the zone refining required to get pure silicon), which is almost always sourced from fossil fuels. Electric cars that use batteries also have the advantage of storing the waste energy from braking, which even your hydrogen fuel cell car won't do. W203.27.72.5 (talk) 22:13, 15 July 2012 (UTC)

A house uses less electrical energy than a car in use, unless it has electrical A/C or electrical heating on, in which case solar panels on the roof aren't likely to get the job done. (The fact that everybody doesn't already power their houses entirely with roof solar panels is evidence enough that this isn't practical.) StuRat (talk) 21:24, 15 July 2012 (UTC)

Spot on. I wish greenies would understand that. Wickwack121.221.217.187 (talk) 11:04, 16 July 2012 (UTC)

I guess solar is already technically competitive with wind in the middle of the day peak during the summer, but not enough to make investing in solar a better idea than investing in wind for probably at least a decade. 71.212.249.178 (talk) 21:31, 15 July 2012 (UTC)

Also, any new technology could be responsible for lots of carbon emissions, if it results in us dumping our current fleet of vehicles in junkyards. We should wait until each vehicle is due for replacement, before switching to a new technology, or, where possible, modify our current vehicles now, to use more efficient technology. StuRat (talk) 20:22, 15 July 2012 (UTC)

Well, no - carbon in fuel used until scrapping has already been emitted, carbon emitted during manufacture (eg in powewr stations powering the factories) has already been emitted. However it is right to keep them in use until worn out, as making new stuff causes more emissions, as others have said. Wickwack121.221.217.187 (talk) 11:02, 16 July 2012 (UTC)

That's exactly what I meant. I didn't think it necessary to explain it all explicitly. StuRat (talk) 20:51, 16 July 2012 (UTC)

Curently, the vast majority of hydrogen is produced by steam reforming of methane, a process that emits carbon dioxide: to be precise, exactly as much carbon dioxide as if you'd burned the methane. Since the hydrogen produced has a lower energy content than the source methane, a hydrogen-burning car consumes more methane to go a given distance than an equivalent methane-burning car. A car powered by a hydrogen fuel cell may be different, as the increased efficiency of the fuel cell may offset the energy lost in producing the hydrogen. --Carnildo (talk) 01:52, 18 July 2012 (UTC)

The efficiency of hydrogen electrolysis from water has increased from about 35% to almost 80% in the past decade, due mostly to an iron-ruthenium catalytic anode plating developed by Schrodinger equation-based simulations of catalytic properties. Since, several additional improvements have occurred. 75.166.200.250 (talk) 19:57, 18 July 2012 (UTC)

Science disciplines

Are Biology and Chemistry subsets of Physics or are they completely different but have overlaps?176.27.222.99 (talk) 20:13, 15 July 2012 (UTC)

I'd call them separate, and biologists and chemists would likely agree, but a physicist might disagree. StuRat (talk) 20:16, 15 July 2012 (UTC)

Biology is a separate subject. Chemistry really is a branch of physics. Dauto (talk) 20:22, 15 July 2012 (UTC)

But it can be argued that biology overlaps with organic chemistry. StuRat (talk) 20:25, 15 July 2012 (UTC)

Or biochemistry. W203.27.72.5 (talk) 23:12, 15 July 2012 (UTC)

http://xkcd.com/435 71.212.249.178 (talk) 20:28, 15 July 2012 (UTC)

Yes, they overlap. The difference is that chemistry not only overlaps with physics, it is pretty much completely covered by the definition of physics (which studies the basic property of matter including its chemical properties). Dauto (talk) 20:37, 15 July 2012 (UTC)

Biology cannot be derived from the laws of physics. The genetic code is arbitrary. There is nothing in the makeup of DNA that requires that any three base pairs be physically determined to code for a certain amino acid. For example, UGG does code for tryptophan, but that is merely historical accident--there is no physical or chemical reason it had to do so. In This is Biology, Ernst Mayr gives an off-the-cuff list of two dozen concepts like ecological niche, sympatric speciation, and sexual selection which are emergent and cannot be reduced to any chemical description or physical laws. μηδείς (talk) 21:19, 15 July 2012 (UTC)

The gas cloud that collapsed to give rise to our Sun, the Earth and the othe planets also gave rise to you and me. One can, in principle, formulate any biological question in terms of only the fundamental laws of physics, as a summation over the initial conditions of that gas cloud. Count Iblis (talk) 22:52, 15 July 2012 (UTC)

• You won't have to go that far to defend the point that biology is chemistry constrained by existing living beings. You can rest assured that everything that's within a living being is explained by chemistry/physical/mathematical concepts. What else could someone expect? OsmanRF34 (talk) 23:47, 15 July 2012 (UTC)

Then do it or show where it has been done. "What can be asserted without proof can be dismissed without proof" - Hitchens. μηδείς (talk) 23:21, 15 July 2012 (UTC)

I don't know if the question is whether or not one can be derived from the other so much as whether they are considered separate sciences. When I studied chemistry, it was taught by the School of Physical and Chemical Sciences. It's since become the School of Physics, Chemistry and Technolgy, and includes IT subjects. Biology was always taught by the School of Life Sciences. W203.27.72.5 (talk) 23:12, 15 July 2012 (UTC)

The Nobel Prize in Chemistry has often been awarded to biologists such as Max Perutz, Luis Federico Leloir, Walter Gilbert, Aaron Klug, Sidney Altman, Peter Agre, Roderick MacKinnon, Aaron Ciechanover, Irwin Rose, Roger D. Kornberg, Osamu Shimomura, Martin Chalfie and Venkatraman Ramakrishnan. W203.27.72.5 (talk) 02:04, 16 July 2012 (UTC)

@OsmanRF34: Assuming I understand your comment, can you please explain to me the meaning of sexual selection using only chemical terms? (Forgive me if I misunderstand you.) The issue here is not that nothing in biology contradicts chemistry. The issue is that the concepts of chemistry are insufficient to express the truths of biology. Again, I refer to supervenience. μηδείς (talk) 04:04, 16 July 2012 (UTC)

Well, when one collection of genetic molecules loves another collection of genetic molecules very much, and the enzymes are right and they have been to a sanctuary to witness to their friends and families that they sincerely believe they might belong to organisms in at least the same genera, then they may react in such a way as to replicate in disjoint pairwise parts, and if they are lucky, the replica might be pH-balanced and otherwise viable within the host organism's cytoplasm.... 71.212.249.178 (talk) 04:55, 16 July 2012 (UTC)

David Goodstein referred to biology, chemistry and physics as being "decoupled" from one another (this idea is probably not original to him). Point is, there is plenty that can be done in biology without any knowledge of chemistry, and plenty that can be done in chemistry without any knowledge of physics. The three basic, hard sciences absolutely overlap, but parts of them can be separated. With regard to what Medeis mentioned about the genetic code, I think the more important lesson about it is that biologists were able to do a tremendous amount of new science once the genetic code was deciphered, but most of the new discoveries required no understanding of the chemical nature of Watson-Crick base pairing. It's the same way a programmer can write software for your computer without knowing why a transistor works, or how a mechanic can tell that you need a new car battery even though he couldn't build one from scratch. Although I guess these are all just more advanced versions of "how does a pencil know to fall if it doesn't understand gravity?" Regardless, I'm still waiting for the complete formulation of biological laws starting from the standard model of quantum physics. Someguy1221 (talk) 05:17, 16 July 2012 (UTC)

I agree with Someguy1221 and disagree with μηδείς. Fundamental laws can give rise to effective laws in some regime and it is then possible that some phenomena are fully described by these effective laws. What then happens is that in a counterfactual situation where the fundamental laws would have been slightly diffent, the old effective laws still exist but it is located at a slightly different scale. So, in the programmer example of Someguy1221, if the fine structure constant were slightly different, electrodynamics would have been affected, but you could still have slightly different people writing the same computer programs on slightly different computers. The program would still be the same, so to understand the properties of the program, why it did get written etc. etc., it seems that the fundamental laws don't play any role at all.

But, of course, the existence of the effective laws and is properties can in principle be derived from the fundamental laws. Within physics itself one frequently encounters this, e.g. a lot of thermodynamics is independent of statistical physics in the sense that the laws of thermodynamics don't depend on the underlying miscoscopic model of the substance. Also, while the value of thermodynamical variables obviously do depend on the microscopic model, at the critical point they can behave in a singular way, and that singular behaviour is to leading order the same for many different materials (e.g. the heat capacity of water at its critical temperature diverges in exactly the same way as nitrogen near its critical temperature). The explanation for this universal behavior is that the different materals at their different critical temperatures are described by the exactly same effective model. Count Iblis (talk) 16:05, 16 July 2012 (UTC)

Perhaps you are confusing the history of the universe itself regardless of our knowledge of it with science as a body of knowledge. No one is claiming that something that is not chemical or physical occurs in biology. The OP's question, however, was whether biology is a separate science from physics. It is. It is a separate set of concepts which cannot be derived a priori from physics. I see you have studiously ignored that point entirely, making unsupported assertions about biology while speaking of thermodynamics. Again, I challenge anyone to show where any concept like ecological niche or sexual selection has been defined in the terms of chemistry or physics, or contradict the fundamental and striking fact that the genetic code is chemically arbitrary. μηδείς (talk) 19:13, 16 July 2012 (UTC)

"Randomness in quantum theory not only here to stay, it is apparently the way to go. 'Its appeal is its fundamental nature and broad range of implications: knowing the precise configuration of the universe at the big bang would not be sufficient to predict its entire evolution, for example, in contrast to classical theory,' says Tittel."

Terence E. Stuart, Joshua A. Slater, Roger Colbeck, Renato Renner and Wolfgang Tittel, 'Experimental Bound on the Maximum Predictive Power of Physical Theories', Phys. Rev. Lett. Volume 109 Issue 2 DOI:10.1103/PhysRevLett.109.020402 cited in Does Play Dice With The Universe μηδείς (talk) 17:53, 17 July 2012 (UTC)

Mathematical Formulation of the Standard Model

From a mathematical point of view(I am a mathematician). Looking at the description of the Standard Model (mathematical formulation), it looks quite ugly. Compared to lets say the Maxwell equations or Einstein's field equations which look mathematically aesthetic, the formulation of the standard model seems to be a huge mess. Is there a simpler formulation than in the article available or has there been any research related to simplifying the formulation (lets say by basing the theory on the fewest possible "simple" axioms)? I noticed that physicist do most calculations and derivations much more sloppy (eg. Renormalization) than it is done in mathematics (this is also mentioned in the article Yang–Mills existence and mass gap). Is there any research on a mathematical rigorous formulation of a theory (standard model or something different)? --helohe (talk) 23:57, 15 July 2012 (UTC)

Yes, but none of them come anywhere near the predictive power of the Standard Model, especially now. See unified field theory. You might be more interested in studying electroweak interactions, where there is still a rich opportunity for theory being tested by experiment. 71.212.249.178 (talk) 01:15, 16 July 2012 (UTC)

Isn't the OP just talking about if you had the same theory but just formulated it in a neater, more rigourous way? I can't see how that would make it less predictive. W203.27.72.5 (talk) 01:41, 16 July 2012 (UTC)

The Standard Model (with neutrino mass) consists of relativistic quantum field theory plus:

• Some "extra dimensions" (perhaps not literally) that are curled up into a shape whose symmetry group is the group of (3×3, 2×2) block-diagonal unitary 5×5 matrices, called the SM gauge group.
• A fermionic field that is chiral (only one of the two circular polarization directions exists) and transforms in the 16-component representation of SO(10), considered as a supergroup of the gauge group in the obvious way (i.e., it occupies those "orbitals" in the "extra dimensions"). Also, two more copies of the same field, and the CPT duals of all three.
• A scalar field in a particular two-component rep of the gauge group, and its CPT dual.
• All possible renormalizable symmetry-respecting interactions between those components, with seemingly random strengths.

From that, after a fair amount of manipulation, you get all the usual particles with their weird charges and interactions.

Although the strengths looks kind of random, they aren't totally random. The particle masses vary over a much wider range than you'd expect (the masslessness of the photon and gluons is a prediction, though). The strong force CP-violating angle is consistent with zero, for no apparent reason. It's not clear why the gauge symmetry is what it is, or why there are three copies of the fermions, or why they seem to only exist in those orbitals. And that scalar field seems kind of out of place.

No rigorous axiomatic formulation of the Standard Model has been found, and it's not for lack of trying. That's probably because it genuinely doesn't have one. -- BenRG (talk) 02:02, 16 July 2012 (UTC)