Wikipedia:Reference desk/Archives/Science/2010 January 8

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January 8

californium

The section Californium#Characteristics says: "One microgram spontaneously emits 2,314 million neutrons per second"

Is that 2.314 million per second, or 2.314 billion (Short scale) per second? (Comma is such a strange symbol to use for a decimal point.) And incidentally the ref it points to does not say. Ariel. (talk) 00:37, 8 January 2010 (UTC)

It should be 2.314 million per the ref on the top of page 3. Fixed in the article. Dragons flight (talk) 00:42, 8 January 2010 (UTC)

Chewing medicine capsules

Bottles of medicine capsules always say not to chew the capsules, but to swallow them whole. What would happen if one were chewed: would it be useless? Don't take this as a request for medical advice; I can't imagine why I wouldn't follow the directions and swallow them, even if everyone here says that it would help to chew them. Nyttend (talk) 00:56, 8 January 2010 (UTC)

I think the main problem is that you would get the medicine into your bloodstream too quickly. The capsules are designed to release the drug at a certain rate. If you increase that rate, you may be risk of overdose, but you'll also be at risk of the drug level in your blood dropping too low - when you take a pill every 4 hours that should maintain the level in your system within certain bounds, if you chew it you'll get a big spike when you take it and then it will drop really low until you take the next one. --Tango (talk) 01:04, 8 January 2010 (UTC)

Because of the Enteric coating. Ariel. (talk) 01:16, 8 January 2010 (UTC)

They may also release the drug too early, which could render it useless (eg. a drug that is inactivated by hydrochloric acid needs to be protected as it passes through the stomach). --Carnildo (talk)

Ah, yeah; at one time I was taking two medicines, and the doctor told me that I could take one (which came in capsule form) at virtually any time in a day because it released slowly, while I had to take the other one (a tablet) at specific times to ensure that I had proper levels. Nyttend (talk) 02:10, 8 January 2010 (UTC)

When you say you could take it at any time, did it need to be the same time every day? If you take it significantly less than 24 hours after the last one (assuming it was one a day) you would still have too much in your system even if it was releasing slowly, and vice versa if it significantly more than 24 hours after the last one. Issues with when you a take a drug are usually to do with whether or not you need food in your stomach when you take it. --Tango (talk) 03:24, 8 January 2010 (UTC)

I am sure most capsules will have bad taste. You tend to throw up weird testing substances before you can chew and swallow completely. manya (talk) 04:18, 8 January 2010 (UTC)

(OR) I once chewed a Tylenol Extra Strength Geltab and my mouth went numb with a horrible taste for about an hour and a half. It seemed as though the gel from the capsule couldn't be washed from the skin in my mouth. —Preceding unsigned comment added by 99.226.164.154 (talk) 14:59, 8 January 2010 (UTC)

Bacteria and Human feces

Does human feces have bacteria in it when push-out? Or is it still fresh when going to the sewage? And could you die/get sick if you ate it? —Preceding unsigned comment added by RadioActive697 (talk • contribs) 05:00, 8 January 2010 (UTC)

See coprophagia. Dismas|^(talk) 05:29, 8 January 2010 (UTC)

And as for the bacteria... see gut flora. Feces is nearly 60% bacteria. Eww. And it's of note that even if the bacteria weren't dangerous to eat (which it is), feces is a major vector for a number of diseases, like hepatitis, cholera, etc. Generally speaking, you don't want to be consuming feces.--Mr.98 (talk) 14:59, 8 January 2010 (UTC)

Although a couple of times I've suggested doing so to somebody. Looie496 (talk) 17:07, 8 January 2010 (UTC)

MythBusters did a test on the idea that flushing the toilet causes fecal coliform bacteria to disperse and land as droplets on your toothbrush. When they smeared both the used toothbrushes and the ones kept in a chamber away from use then smeared the samples with agar, all the toothbrushes had the bacteria...the myth was confirmed. ~AH1^(TCU) 19:56, 9 January 2010 (UTC)

Just a thought... did they think to sterilize them before the experiment? – ClockworkSoul 07:58, 10 January 2010 (UTC)

Water/Hydroxylic acid

Why water is also called hydroxylic acid? Is water acid? --Qoklp (talk) 06:46, 8 January 2010 (UTC)

It isn't. It's called water. Sometimes you see bullshit/joke references to water as either "dihydrogen monoxide" (it's proper systematic name, but no one ever uses this name seriously) or hydroxylic acid. If named under the standard rules of acid nonmenclature, the name "oxylic acid" or possibly "hydroxylic acid" may apply as well, but no one seriously ever uses these names. Under acid nomenclature, the acid is named based on the anion in the acid; the cation of all acids is H⁺. So, if you consider water to H⁺ and OH^- (hydroxide ion), you could kinda-sorta consider it as "hydroxylic acid". Except that nobody, ever, not even the most pedantic of chemists, would ever call it anything except water. --Jayron32 06:51, 8 January 2010 (UTC)

Besides everyone knows dihydrogen monoxide and hydroxylic acid is simply greenie scare mongering and the proper name should be Hydrogen hydroxide] Nil Einne (talk) 12:32, 8 January 2010 (UTC)

Actually, Qoklp is right. Water is amphoteric (can act as both a base and an acid), and the auto-ionization of water is a very important concept in acid-base chemistry. Hydroxylic acid is technically a correct name, as is hydrogen hydroxide. ~ Amory (u • t • c) 15:40, 8 January 2010 (UTC)

Oh, they are all "technically correct" names for Water. It doesn't mean anyone at all actually uses those names. --Jayron32 19:10, 8 January 2010 (UTC)

Except in a joking context: see Dihydrogen monoxide hoax. Nyttend (talk) 00:33, 9 January 2010 (UTC)

Rainwater, for example, usually has a pH number slightly higher than 5, where 7 is neutral. ~AH1^(TCU) 19:52, 9 January 2010 (UTC)

On the other hand, water is a good quench and convenient way to stop many chemical reactions when you feel you're through (just throw water on it). Water can both donate a lone pair or a proton -- and that is usually the important part. Water can break apart molecules aka hydrolysis. Evolution of water from a reaction can drive a condensation reaction forward. John Riemann Soong (talk) 12:50, 12 January 2010 (UTC)

Question related to Carbon-Capture and Sequestration

Resolved

The following question occurs to me as being one that could be used as an illustration. It probably has appeared before.

What would the entire atmosphere's thickness be if all of its component molecules were liquified?

Perhaps more difficult is to ask for the thickness if the atoms were rearranged ideally in solids, but maybe someone wants to take a shot at that as well.Julzes (talk) 08:17, 8 January 2010 (UTC)

About 10 meters. Dragons flight (talk) 08:21, 8 January 2010 (UTC)

(ec) The questions are actually easy. As you probably know, atmospheric pressure at sea level is approximately equivalent to the pressure of a 10-meter layer of water. If you could liquefy the atmosphere, the entire atmosphere thickness would therefore be 10 meters if the density of the liquid is 1 g/cm3. I don't remember what the liquid air density is, but I'll look it up now. The general result is: thickness = 10 m * 1 g/cm3 / rho [g/cm3] where rho is the density of liquid or solid air. --Dr Dima (talk) 08:22, 8 January 2010 (UTC)

OK, density of liquid air at 1 atm pressure is about 0.87 g/cm3, so the thickness of the atmosphere would then be 10 m * 1/0.87 = 11.5 m . --Dr Dima (talk) 08:25, 8 January 2010 (UTC)

(Edit conflict) Well, Earth's atmosphere weighs 5x10¹⁸ kg[1]. It's mainly 78% nitrogen and 21% oxygen. Liquid oxygen has a density of 1146 kg/m^3 [2], liquid nitrogen has a density of 811.6 kg/m^3 [3] put that together and you get: ((5x10^18 kg) * 0.78)/(811.6 kg/m^3)+((5x10^18 kg) * 0.21)/(1146 kg/m^3) = 5.722x10^15 m^3 [4]. Now you have a volume, and you need to convert it to a height above the earth.

You know, wolfram alpha has all these constants, but I can't quite get it to do the math for me without copy/pasting the numbers into a new formula. Ariel. (talk) 08:35, 8 January 2010 (UTC)

I see it's a bit simple. How about the question of changing all excess (anthropogenic) Carbon to diamond. How thick would that be?Julzes (talk) 09:38, 8 January 2010 (UTC) I'll ask the question I was about to ask at the mathematics desk.Julzes (talk) 09:47, 8 January 2010 (UTC)

Distributed globally? A layer 4 microns thick per year. Concentrated in one place that's 2 cubic km per year, that would be far more diamonds than have been collected in the entire history of the human race. (Of course it takes even more energy to convert the carbon into diamond, so no one would actually want to use diamond as a storage medium.) Dragons flight (talk) 10:07, 8 January 2010 (UTC)

There is no excess carbon. It's carbon dioxide. They are not the same thing, despite media and others being lazy and calling it carbon. It's not carbon offsets, it's carbon dioxide offsets, etc. Carbon dioxide can not be turned into diamond, although carbon can be. And BTW, there is a very very small amount of it in the air - about four hundredths of a percent, and the excess carbon dioxide amounts to 8 or 9 thousandths of a percent. Ariel. (talk) 10:25, 8 January 2010 (UTC)

Essentially less than a millimeter thick for the whole history? I see the math on localising it looks correct. It helps to actually do the math. Ariel, I think I and Dragons Flight understand what you're saying.Julzes (talk) 10:35, 8 January 2010 (UTC)

And, strictly speaking, it is excess Carbon I was thinking of. Since it accumulated due to the burning of hydrocarbons, that entailed some (I know) small decline in Oxygen in not only relative but also absolute terms. Dragons flight is almost certainly correct that the ideal method of precipitating out the Carbon from the atmosphere does not entail separating the Carbon and Oxygen atoms from each other (or Carbon and Hydrogen, concerning methane) and turning the Carbon into diamond, but it's a thought if clean energy were sufficiently cheap at the point in time at which geoengineering were to take place (probably a bad thought, but this was just an abstract curiosity exercise).Julzes (talk) 11:06, 8 January 2010 (UTC)

Actually we already have very cheap and plentiful devices that can remove CO2, there is no need for geoengineering. They are called plants :) And clean energy already exists too - it's called nuclear power (especially a thorium cycle, or a cycle using nuclear reprocessing, both methods leave almost no waste behind). The only reason we use hydrocarbon fuel is that it's cheaper. Ariel. (talk) 11:22, 8 January 2010 (UTC)

You don't sound like you understand the whole situation, but I don't feel like arguing. I got the answer to the question I was asking.Julzes (talk) 11:47, 8 January 2010 (UTC)

Whether it reflects understanding of the whole situation or not, I think that summary by Ariel was pretty much nail-on-the-head. As I've mentioned numerous times, the only obstacle we face with regard to climate change is socio-economic, not technological. There's a big bubble brewing around these parts with every upstart kid trying to sell some kind of new clean technology... but we already have industrial-scale, extremely clean alternatives to hydrocarbon. They are simply undesirable for economic and social reasons. There's no requirement to develop new technologies. Nimur (talk) 15:36, 8 January 2010 (UTC)

There is truth in that, and I think I understand your standpoint and what you're saying. Basically, I agree with the idea that we could probably get along quite well without developing fusion and some of the less ambitious energy technologies that are basically now in their adolescence. 'Could probably' is a key part of the last sentence, though. Global warming catastrophism is a perspective that shouldn't be taken as extreme, but rather as being within reasonable risk assessments. My own personal belief is that we should set the Carbon balance of the atmosphere precisely where it was when the industrial revolution took off. Since we can, and it probably would not really be that expensive relative to what we absolutely need to do; it would be a nice legacy to leave the future. Obviously, that's the future one step removed (the future of the future, one could say).Julzes (talk) 23:49, 8 January 2010 (UTC)

That's interesting optimism - but sadly, shows a deep misunderstanding of the problem. The half-life of CO2 in our atmosphere is something like 10,000 years. Since we already have around twice as much CO2 in the atmosphere today than we had at the start of the industrial revolution - we can't possibly restore the atmosphere to the way it was back then for another five thousand years at least - and that assumes that we don't produce another gram of CO2 in all of that time. The very best would could possibly do - even in theory - would to keep CO2 levels as they are today. But we know THAT isn't going to happen either. So sadly, your belief is totally untrue. SteveBaker (talk) 06:44, 10 January 2010 (UTC)

What are you talking about?! And why can't you edit in line?! You don't know the first thing about the use of Carbon-capture technology. This was computed in another section below as a 1500-year problem at around the energy of 2 km^2 of solar radiation in space.Julzes (talk) 17:27, 12 January 2010 (UTC)

When I'm talking about risk assessment, I would consider not acting like a catastrophe could happen as being analogous to betting one's life for a million pounds on 2:1 odds in one's favor.Julzes (talk) 00:00, 9 January 2010 (UTC)

powering a stepper motor

Hello, I've disassembled an old DVD drive and have removed the motor that rotates the disc. It has three wires. I've figured out (with the help of an elementary cell) that they need to get pulses that are each out of phase by 120° (this is but a guess). In other words, each of the three wires must be pulsed one after the other, while the other two are connected to the ground.

Is there a simple circuit I could build in order to have the motor rotate? I'd rather build a circuit from discrete elements (individual transistors) than take an IC. I presume the circuit will be similar to that of a runnning light or something like that.

On a second thought, could I also use inductors?

—Preceding unsigned comment added by 88.70.81.101 (talk) 11:21, 8 January 2010 (UTC)

A three phase system is likely a servo motor not a stepper motor. In industry, such things are generally driven with three out-of-phase alternating currents with the phase velocity determining the rate of rotation. For hobby applications it probably is possible to drive it with a sequence of pulses (which would mimic the way stepper motors generally work). Analog circuit design is not really my forte, but hopefully someone else will be along to help. Dragons flight (talk) 13:36, 8 January 2010 (UTC)

PS. This page [5] gives a somewhat clearer idea of difference than our article does. Dragons flight (talk) 13:39, 8 January 2010 (UTC)

I basically need three "outputs" out of which, at any given moment, one is at a high potential and the other two have are at a low one, and they, like, take turns as to who's got to be "high" in this instant (like I said, running lights.) My question basically was, how to accomplish this... 92.226.94.41 (talk) —Preceding undated comment added 15:47, 8 January 2010 (UTC).

88.xx was me, btw. 92.226.94.41 (talk) 15:58, 8 January 2010 (UTC) The waveform doesn't matter, I think whether it's square or contiguous sine waves, both will do.

I think my two options are either a transistor circuit (which, for simplicity, would be effectively digital), kind of like a multivibrator with three, rather than two, cascades (stages) (is there even such a thing?), or something analog that uses inductors to make the the two other phases from one-phase AC. —Preceding unsigned comment added by 92.226.94.41 (talk) 16:16, 8 January 2010 (UTC)

Hi, it's me again. This is what I had had in mind: [6] Thanks anyone anyway. —Preceding unsigned comment added by 92.226.95.35 (talk) 19:26, 9 January 2010 (UTC)

I don't think people here know. Try the forum on makezine. Ariel. (talk) 20:53, 10 January 2010 (UTC)

Well water smell

What are some possible causes for a house's well water smelling like rotten eggs when it comes out of just one faucet in the house? Dismas|^(talk) 13:15, 8 January 2010 (UTC)

That whatever functional molecular group emits the smell of rotten eggs has been produced by bacteria that exist in the well water. DRosenbach ^{(Talk | Contribs)} 13:21, 8 January 2010 (UTC)

Rotten eggs is usually sulfur, in this case sulfur/sulfites are reduced to hydrogen sulfide. ~ Amory (u • t • c)

If the smell is really isolated to a single faucet, you can track the plumbing back to see where that plumbing line diverges from the rest of the supply. Presumably, the source of the contamination should be somewhere along that branch. I'd use caution if this is your potable water supply, as contamination could spread, with or without the smell, to other parts of your water supply. Nimur (talk) 15:31, 8 January 2010 (UTC)

According to your user page, you reside in Vermont. I believe the state health department offices located around the state offer very reasonably priced water testing. --Jc3s5h (talk) 17:33, 8 January 2010 (UTC)

On a tangent, the hot water in Iceland all smells of eggs due to geothermal heating. Fences&Windows 18:11, 8 January 2010 (UTC)

This link may be very relevent here. Many water softeners have sulfates in them, and often water systems have "sulfur-reducing bacteria" in the water, which turn the sulfates into sulfides, which stink like rotten eggs. Perhaps your softening system or pipes need some sort of treatment to get rid of these bacteria? --Jayron32 19:07, 8 January 2010 (UTC)

Here is the rest of the google search I used to find the above. There are dozens of links which say about the same thing. --Jayron32 19:09, 8 January 2010 (UTC)

Thanks, all! Dismas|^(talk) 03:29, 9 January 2010 (UTC)

Spectrophotometer operating manual?

Does anyone know where I can find an operating manual for a Varian AA-1275 atomic absorption spectrophotometer? I've already tried the manufacturer. The book's called “Atomic Absorption Spectrophotometers AA-1275 & AA-1475 Installation Instructions & Operation Manual”, but amazon doesn't have it. Nikkimaria (talk) 14:28, 8 January 2010 (UTC)

You may try posting your question over here. Have you tried ebay.com or craigslist.com? Perhaps there's a similar site for other physics-related devices and books, too? ···日本穣^? · 投稿 · Talk to Nihonjoe 06:29, 9 January 2010 (UTC)

Books about the creation of new breeds

Hi all, I would like to know if you could suggest me a book about the creation of new breeds; specific texts about breeding of dogs and fishes, and about interspecific hybridization procedures in general, are welcome, althought not strictly required. Thanks. --87.3.120.61 (talk) 14:48, 8 January 2010 (UTC)

Trabant automobiles and Umweltzonen

Why are Trabant automobiles not allowed in Umweltzonen? --84.61.151.145 (talk) 17:23, 8 January 2010 (UTC)

Likely because of their emissions by the looks of things. This site (http://www.motorhomefacts.com/ftopic-43830.html) has some info that might be of interest. I suspect the Trabant is in the red/yellow category and thus restricted in some zones. ny156uk (talk) 17:26, 8 January 2010 (UTC)

"Smoky two-stroke engine" according to our Trabant article. To my understanding that's an understatement. Looie496 (talk) 17:31, 8 January 2010 (UTC)

What is a "tail bridge"?

I just finished an article on Slauerhoffbrug ‘Flying’ Drawbridge which is described as being a tail bridge. I suspect that means that it is a drawbridge that only lifts from one side of the river or that it is a bridge that rests on only one side of the river. I've gone through countless Yahoo and Google links and checked several online dictionaries. In the whole scheme of things, this is not important, except for the challenge. Thanks for any help! GloverEpp (talk) 17:43, 8 January 2010 (UTC)

There is a type of swing bridge, known as a 'bob-tail' that is hinged off-centre, see [7]. The bob-tail refers to the concrete counter-balance weight that's required on the shorter end. Mikenorton (talk) 18:19, 8 January 2010 (UTC)

This link suggests that drawbridges with a counterbalanced tail (a 'tail bridge') are a relatively new development, taking up less space than more traditional designs. Mikenorton (talk) 18:28, 8 January 2010 (UTC)

Tris(pentafluorophenyl)boron + reducing silanes

AFAIK this mixture will reduce aliphatic alcohols into alkanes. Will it reduce phenols or catechols? John Riemann Soong (talk) 21:20, 8 January 2010 (UTC)

Ohm's Law

I was looking at the article on the drude model for the derivation of Ohm's Law, and I was a little confused about something. In the article, it says that the change in the average momentum = qEt, where t is the average time between collisions. But I would have thought that the change in momentum = qEt, and therefore the change in average momentum is half that, but apparently this is wrong. Can someone explain why? —Preceding unsigned comment added by 76.68.246.210 (talk) 21:26, 8 January 2010 (UTC)

The average in question is over electrons (really over "instances of electron acceleration between collisions"), not time, so there is no halving. --Tardis (talk) 21:46, 8 January 2010 (UTC)

If that's the case, then p represents the electron's momentum just before a collision, correct? In the article, the current density is expressed as J=qnv, where v is the electron's drift (ie average) velocity. Then it says that p=mv, but if p isn't the average (time-wise) momentum of the electron, then why should this relationship hold?

Sorry, I was quite a bit unclear, and saying "instances" was flat-out wrong. First, a general point: the average over time for one electron is the same as the average over all electrons at any one time (because the electrons are equivalent and so we can suppose the various electrons in a snapshot to be representative of the life experience of any one of them), and thus is also the same as the average over all electrons and all time. The average we are talking about is this common value (so it is fair, albeit unnecessary, to call it an average over time), and is perversely also the average of the momenta of electrons that are just about to collide. This last equivalence is not a universal truth but arises from the dispersion in intercollision times: if each electron always traveled for exactly τ time and then lost its momentum, it would have qEτ momentum at the end of each arc (and so the average would be that!) and the average over all electrons at any moment would be half that. But, at the moment you look, some electrons are in the middle of short arcs between collisions (so their non-noise momenta are very small) and others are in the middle of long arcs (so their momenta are large, possibly even larger than qEτ — even though, on average, you are seeing them mid-arc and so are only seeing half their "final" momenta). If we follow one electron around, the lengths of these arcs average to τ, but the electron spends more of its time in the long arcs (because they're longer!) and so skews the average in time/etc. upwards.

It just so happens that, with an exponential distribution of arc lengths (which is implied in the article, and should perhaps be stated explicitly), this effect doubles the average length of arc when you average over time/etc. (rather than collisions), and precisly cancels the (still-true!) fact that the average momentum we observe is only half of that that every electron will achieve at the end of the arc in which we observe it. This peculiar result is known as the inspection paradox or bus paradox. It lets us (for exponential distributions only!) say convenient things like "the average momentum is equal to the average time multiplied by the force" (which is where I drew the point that it wasn't an average over time, exactly). Put another way, and relying on the exponential distribution's famous memoryless property, we can look backward in time and say that the electrons in a snapshot have been flying free for an average of τ time, and so have on average the (unhalved)amount of momentum acquired during such a flight. --Tardis (talk) 23:09, 8 January 2010 (UTC)

Ahhh, okay I think I understand. Just a few things to clarify:

1) Is it easy to prove this property of exponential functions?

2) In the last sentence, what did you mean by "looking backward in time"...and why can we say that the electrons have been flying freely for an average of τ time? Is this because of the aforementioned property of the exponential function?

And by property, I'm refering to the arc length business. Thanks! —Preceding unsigned comment added by 173.179.59.66 (talk) 01:15, 9 January 2010 (UTC)

(Careful: while the PDF (and CDF) for the exponential distribution does involve the exponential function (not a surprise), people will not understand you're talking about the distribution if you just say "exponential function".)

1. If you're talking about the doubling, which I think you are, that's pretty easy: since arcs of length x will be seen in proportion to their probability of occurrence (per electron) and to x, the distribution is proportional to $x\lambda e^{-\lambda x}$; normalizing yields $x\lambda ^{2}e^{-\lambda x}$. The expected value of that distribution is 2/λ, which is twice that of the original. Another way to look at it is from the memoryless property (also easy to prove; ask if you want that): when I look at a stream of exponential processes at a random time, my offset into whichever one is active can't mean anything, so my expected time to wait is still 1/λ. But I should on average look in at the middle, so the total expected time (averaged in this way) must be twice that, as you have said.
2. If we simply consider the process as evolving backward in time, very little changes; in particular, it's still an exponential distribution for the amount of time until the "next" collision (which is really the previous collision). (This makes sense; time reversal reverses all the velocities of the electrons, but they're traveling in the same environment so they suffer collisions at the same rate.) Since that distribution is memoryless, we can immediately conclude that the average time among electrons to the previous collision is τ, and so the average momentum over all the electrons is qEτ. --Tardis (talk) 20:26, 11 January 2010 (UTC)

name of a littoral creature - nasty looking phallic thing

Hi - trying to remember the name of a creature that I think people dig up from the sand in the US/Canada? Maybe a foot long, or longer - looks like a brownish penis or tentacle - squirts sea water from one end - I think brave people eat them...

Thanks Adambrowne666 (talk) 22:08, 8 January 2010 (UTC)

Geoduck, kinda like a clam on steroids. It's pronounced "goo-ee-duck". --Jayron32 22:14, 8 January 2010 (UTC)

I love you guys. Adambrowne666 (talk) 02:36, 9 January 2010 (UTC)

Color preference vs. gender

Is there any particular reason why females like pink while males like blue or green more? Why is pink a feminine color? Every female in my family's favorite color is pink while the males are blue. 198.188.150.134 (talk) 22:43, 8 January 2010 (UTC)

It's genetic. Or it's cultural. -- Finlay McWalter • Talk 22:59, 8 January 2010 (UTC)

The evidence for it being "genetic" given in that article is either very poorly articulated, or extremely unconvincing. The sample sizes are blindingly small for such giant conclusions (37 people born in China get to stand in for "everybody who is not British"?). --Mr.98 (talk) 23:05, 8 January 2010 (UTC)

It's just what they've been acculturated to. Go into a store that sells clothing for babies — all of the boy stuff is blue and about dogs and trucks and all of the girl stuff is pink and about princesses. From day one—literally—kids in the U.S. (and probably elsewhere) are taught that pink is girls and blue is boys. Even if they don't get it at home, they will get it in their toys, their commercials, their friends. It has not been like this forever—our article on pink points out that the current practice dates only from the 1940s—which is a sure sign that it is not actually related to anything physical, any more than green means "go" and red means "stop". --Mr.98 (talk) 23:02, 8 January 2010 (UTC)

Up until the first bit of the 1900s, it was the other way around. Blue was seen as dainty, and associated with the Virgin Mary, while pink was a strong color, reminiscent of the very powerful red and hence appropriate for boys. ~ Amory (u • t • c) 04:13, 9 January 2010 (UTC)

Yes I'm pretty sure that's discussed in one or more of our articles, seems to be mentioned in one of the links above and has also been discussed here before and I would say that throws a spanner in the claim it's genetic. I haven't looked for a scientific article which the above researchers may have published but I too am dubious, particular about the part which attempts to use some people in China to represent different cultures which is problematic since the current cultural phenomon has AFAIK spread rather widely. For example, I know it's quite common in Malaysia. I doubt it would be very different in China. This could indicate some genetic basis or it could just indicate are very strong and wide ranging cultural phenomen. As with many things attempt to tell cultural phenomen from genetic, I would be much more interested in tests using people who have lived in some African or whatever tribe with little or no outside contact all their lives sadly such people by their nature are difficult come by and extensive testing on them likely raises many ethically issues. Nil Einne (talk) 06:49, 9 January 2010 (UTC)

Unfortunately I can't remember where, but I remember I read that pink became associated with girls because it resembled menstruations; so it's just a cultural issue. --82.61.166.182 (talk) 18:17, 9 January 2010 (UTC)

I think I read somewhere that blue (clothing? bibs? bedsheets?) was chosen for boys because it was a protective colour, and girls were thought to require less protection so a non-blue colour was chosen, therefore pink (but if this is a cultural thing then there would likely be variations). I also read somewhere years ago that pink in a room is a colour suited for sleep, and blue promotes more activity, but I'm not sure if that information is reliable. ~AH1^(TCU) 18:35, 9 January 2010 (UTC)

Hmm, those are all very interesting! Thanks for the replies. However when I was a child, I loved the color blue because I thought it was beautiful, and my sister loved pink for the same reason. Neither of us were thinking about which was appropriate nor socially accceptable. Therefore I'm not convinced that this is a cultural trend. 198.188.150.134 (talk) 03:58, 10 January 2010 (UTC)

Then you aren't listening to the replies here. The fact is that the association of pink for girls and blue for boys was the other way around as recently as 1940. So it can't possibly be genetic because pretty much the entire population would have had to undergone a genetic change in just one generation - and that's completely impossible. It CAN only be culturally linked because only culture can effect changes to human society on those kinds of time-scales. The fact that you and your sister happened to feel this way can easily be attributed to being bombarded with objects of that color as a child - and even if not, it would still only be a single sample with a one-in-four probability - which we cannot regard as evidence either way. SteveBaker (talk) 06:34, 10 January 2010 (UTC)

Usually reliable Newspaper Columnist Cecil Adams claims that the great pink/blue reversal is mostly a myth. There was never a consensus that pink was a "boys color" the way that there is currently a consensus that it is a "girls color". APL (talk) 23:15, 10 January 2010 (UTC)

I think you should actually read the article you linked to a little more carefully. He says that in the 1800's there was no particular gender-specific color - fair enough - there were no decent pink dyes back then anyway (the first really good pink-ish dye was 'mauve' and that was invented in 1856 - so dressing either boys or girls in pink before then would have been almost impossible anyway. In any case, our pink article says that the word "pink" actually referred to a greenish yellow back in the 17th century(!) - so any actual gender preferences dating back that far would likely be confusing at best. Please note that we are saying that the "reversal" happened sometime early in the 1940's. Your "usually reliable" article by Adams clearly states: "For years one camp claimed pink was the boys' color and blue the girls'. A 1905 Times article said so, and Parents magazine was still saying it as late as 1939." - so he has solid references to back up the claim that I and others are making here! He then goes on to say that he doubts this is true (?!?) - but offers no explanation as to why he so casually discounts the very references he just quoted! Our "pink" article has several links to places where it says that there was a reversal in the gender assignments of pink and blue sometime in the 1940's - I don't see why we should take the confused words of some random blogger over some serious evidence. All he REALLY says is that in his opinion this never happened - and his evidence in support of that opinion starts with one sketchy reference to the royal family in 1948 and his first TRUE reference for pink-for-girls is in 1959. Nobody here is claiming that pink-is-for-boys was true much after 1940 - and 8 years is more than enough for a fashion trend to flip. SteveBaker (talk) 03:53, 11 January 2010 (UTC)

I suppose the reason he's "not convinced" is that it's such a short time period. He does mention a 1905 source recommending pink for boys, but some of his secondary sources say that there was no distinct cultural preferences until around 1920. Supposedly, previous to 1920 There are very few known written references to baby color schemes, (And even some of those go the other way! Including "Little Women"(1868) where the characters use the modern color scheme, apparently expecting everyone to recognize and understand it.) and then after 1940 people started using the modern scheme.

In any case, I also find it hard to believe that the "reverse" baby colors were anywhere near as agreed upon or as consistent as the modern color scheme. It's easy to just look at photographs of vintage dolls. Dolls of girls, for girls are often dressed in pink. (Even being careful to only consider ones stated as wearing their original manufactured clothing.) Granted there are also blues and whites, etc, but how many male dolls today would be pink? In fact, looking at photographs of vintage 1930s toys, it's difficult to find a truly pink toy that isn't intended for girls.

So if there was a pink-for-boys rule, it was short lived, and did not seem to strongly manifest in children's toys. APL (talk) 18:00, 11 January 2010 (UTC)

Approaching this from a different angle, there are several problems with your anecdotal evidence. Firstly, a sample size of one is useless in a statistical sense. I'm sure it won't be that hard to find a reverse case, or a case where a brother liked purple and his sister liked green. Neither of these show anything meaningful. (I just noticed SB already said that.) More to the point, cultural indoctrination (for lack of a better word) doesn't require people to actively think of what is culturally acceptable. In fact, if it's particularly effective that's clearly not necessary particularly at a young age. Can you say with any certainty that your parents were not more likely to give your sister pink clothes, items, decorate her room pink etc? And less likely to give her blue clothes, items, etc? And give you blue clothes, items, decorate your room blue etc? And in particularly, less likely to give you pink clothes items etc (since it tends to be the case that people are more likely to avoid associating pink with boys then anything else)? Even if you can say that about your parents, can you say that about everyone else? It's not clear to me what ages we're referring to, but how about in kindergarten or school? And what about your friends? Are you sure the males weren't more likely to be dressed in, like, have toys, have rooms etc that were blue and the females pink and that none of this influence you? And what about indirect actions and talk? Can you be certainty, that your parents and other people you had experience with in your early life didn't via their talk and actions influence your preference of colours? For example, are you sure your parents didn't unconcisously or concisiously discourage you from choosing pink items, clothes etc? I doubt you can be certain for any of this. The thing is, the colour preference is so pervasive that unless you live in an isolated igloo with no exposure to the outside world, it's very difficult to shield your child from it and in fact most parents are not going to (and I'm not saying they should) and many in fact embrace it. Many will be exposed to it from the day they are born, e.g. I believe many hospitals use pink for girls and blue for boys. Even if you do live in an isolated igloo, unless your parents really have no preference of their own then it may be difficult for them to avoid inadvertedly rubbing that off on their kids (there's a reason why double blind trials are greatly preferred). This reminds me of a comment I once read from some controversial Harvard? dean or something who said there was inate difference in the male and female maths or science ability. While I don't agree with the way people responded to that, and am not suggesting he was wrong, one of his comments, that he gave his daughter trucks but she still preferred playing with dolls which shows there's probably a difference (well my rough memory of what it's like) struck me as particularly silly for the same reason. It's extremely unlikely his daughter was no exposed from a variety of sources to the idea that dolls are for girls and trucks are for boys even presuming that he himself and his partner didn't inadvertedly do the same thing. Note that in all cases, it's not necessary for the children themselves to be conciously thinking that that X is for girls and Y is for boys, they could easily be thinking it because of the exposure and influence without consciously thinking of a male-female seperation. Nil Einne (talk) 05:52, 11 January 2010 (UTC)