Wikipedia:Reference desk/Archives/Science/2011 July 13

= July 13 =

Cultural or instinctive - revulsion at homosexuality
I recently read comments on a forum where a large number of people used the argument "I find the idea of homosexual acts disgusting, therefore homosexuality must be absolutely wrong (or evil)" in one form or other. This is obviously a flawed argument; I could use it to say that celery soup is absolutely wrong or evil! I found it interesting that so many people find the idea of homosexual acts disgusting though. Especially since though I support gay rights and equal treatment for homosexuals at a deep level I feel revulsion at the thought of homosexual acts.

Is this revulsion some deep instinct, maybe something to do with a persons sexuality? I have heard some homosexuals say that they find the idea of sex with someone of the opposite sex disgusting, which would support this. On the other hand it is clearly not universal as there are bisexuals. It seems there is some evidence that it is instinctive and some that it is learned or cultural. Has any research been done on this. -- Q Chris (talk) 12:35, 13 July 2011 (UTC)


 * Dont Know of any studies, but my my analysis(guess): Feeling disturbed with homosexual interactions may help choose the a partner of the right sex, (i.e. on the straight and narrow path) especially as a strong attraction for both sexes must be coded in the same genome. As most people judge "what's disgusting for me to do is disgusting even if you do it" instinctively this may explain homophobia.


 * fMRI data indicates that homosexual's brains respond in almost exactly the same way as members of the opposite sex will to smelling estrogen/testosterone. May be in homosexuals the instinctive dislike also is reversed.Staticd (talk) 13:12, 13 July 2011 (UTC)


 * My instinct is that disgust towards homosexuality is almost certainly a learned trait. Within human culture, it is not universal at all; many cultures have no problems with it at all (see Ancient Greece) and some practices, which in some cultures are viewed as homosexual, are commonplace in others (Cheek kissing among males in say France, or hand holding among Arabic males).  Among non-humans, behavior that would be described as "homosexual" is commonplace; male dogs will copulate with each other (heck, a male dog will copulate with a lampost) and such behavior is common among the Bonobos, which are genetically among the closest relatives of humans.  Negative reactions towards homosexuality are likely strongly corrolated towards cultural reactions towards non-procreative or extramarital sex in general.  -- Jayron  32  14:50, 13 July 2011 (UTC)
 * That's a very good point about other cultures. At first I was surprised at how such a culturally learned feeling could seem so instinctive and natural - but then it feels just as natural and instinctive to feel revulsion at people eating Witchetty grubs, or locusts -- Q Chris (talk) 21:15, 13 July 2011 (UTC)
 * Well bearing in mind that the acitivity is ABNORMAL, its not surprising that many people are nauseated by it. — Preceding unsigned comment added by 78.148.128.45 (talk) 15:09, 13 July 2011 (UTC)
 * You may wish to read the messages to which you are responding...you may learn something. DMacks (talk) 15:23, 13 July 2011 (UTC)
 * Define abnormal. Dauto (talk) 15:37, 13 July 2011 (UTC)
 * Abnormal means most people dont do it. — Preceding unsigned comment added by 78.148.128.45 (talk) 16:29, 13 July 2011 (UTC)
 * Most people don't ride unicycles. Do you find unicycle-riders disgusting? AndyTheGrump (talk) 16:32, 13 July 2011 (UTC)
 * Of course they are disgusting: sticking a wheel with a pole attached up thier backsides: what could be more abnormal?


 * Most people don't get college education, most people don't run marathons, most people don't play the piano, most people don't work for the navy, most people don't sing at church choirs, most people don't travel abroad, most people don't ... you get the point. Do you find any of those activities nauseating? Obviously you haven't given that topic too much thought. Why should anybody care about what you think then? Dauto (talk) 19:08, 13 July 2011 (UTC)


 * I believe the bad attitude tends to be stronger in men than in women, and a major part of it is a dislike of the idea of being "hit on" by another man, because it places one in a feminine role and can easily be seen as a challenge to one's own masculinity. Looie496 (talk) 16:37, 13 July 2011 (UTC)


 * Many men get rather turned on by the sight of two women making out, and will pay good money for pornos portraying such activity, so for them, homosexuality per se is no bad thing. But when it's two guys - "oh, that's different, it's unnatural, it's filthy".  Yeah, right.  --   Jack of Oz   [your turn]  19:46, 13 July 2011 (UTC)

Maybe studies have been done on the more general question of whether any particular attitude is "instinctive" or "cultural".

Googling "identical twin social attitudes -wikipedia" gets some possible results which will take some reading through. Pages 64 to 67 of http://www.vipbg.vcu.edu/vipbg/HGEN619/eaves99tr.pdf covers the attempted measurement of the "conservatism scale" and social attitudes of identical and non-identical twins. Table 9 "Summary correlations between relatives (pooled across sexes) for social attitude measures" summarises the results. To this non-expert it appears that identical twins correlate more strongly than non-identical twins in their attitudes to sexual permissiveness, politics, religion and so forth (implying attitudes are partly inherited?) but it would be interesting to see other studies, and conclusions by Reference Desk experts. 84user (talk) 23:38, 15 July 2011 (UTC)

Metamorphosis in humans
The metamorphosis of amphibians is well known, triggered by thyroid hormone, and involves such characteristics as the development of a new stratified layer in the skin, the differentiation of the cerebellum, and various skeletal alterations (see anuran for a more complete list). In humans, these alterations are less apparent, as they occur during fetal development - the same changes in the skin, for example, occur between weeks 9 and 24 of gestation (see - the tadpole-like epithelium is periderm, beneath which a thick stratified epithelium forms, followed by apoptosis of the periderm). At least in mice, responsiveness to thyroid hormone is important for cerebellar maturation. Also, a transient opercular flap (expanded second pharyngeal arch) seems to be characteristic of higher vertebrate embryology.undefined

Some questions...


 * The situation with thyroid hormone in human embryos is complex: the placenta develops to be fully supplied with maternal blood by 12 weeks or so, bringing in a supply of thyroid hormone; but the embryo also supplies its own hormone by 20-22 weeks. There are multiple receptors.  What is the closest we can come to seeing a "paedomorphic human"? (i.e. one not undergoing "metamorphosis", though human paedomorphism is more typically used to refer to heterochrony later in development)


 * Regeneration of limbs is famously lost in frogs after metamorphosis. Looking at the development of human embryos, it is apparent that they have well developed limbs long before the apparent metamorphosis as defined by the skin transformation.  Do these limbs regenerate if severed?  (Admittedly, I doubt experimental evidence is available, but you never know what kinds of accidents will happen...)


 * Am I reinventing the wheel here - has someone published a comprehensive list of similarities between human fetal developmental events and metamorphosis? Wnt (talk) 14:23, 13 July 2011 (UTC)


 * Not a biologist, but I remember the notion from high school bio "Ontogeny recapitulates phylogeny". Edison (talk) 14:44, 13 July 2011 (UTC)

Annihilating a human


Sort of a silly question. If you were to turn the mass of an average human (say, 170 pounds) into energy, how big would the resulting explosion be? --Goodbye Galaxy (talk) 15:21, 13 July 2011 (UTC)


 * The Tsar Bomba, the largest nuclear bomb ever detonated (1,400 the size of Little Boy and Fat Man combined), had a yield of 50 megatons of TNT. By E = mc2, this equates to ca. 2.3 kg of mass converted to energy. A 170 kg mass completely converted to energy would result in about 1.5 × 1019 joules of energy (about 7600 megatons of TNT). According to Orders of magnitude (energy), this is about the same as the yearly electricity production in the U.S. as of 2005. -- 174.31.204.164 (talk) 15:42, 13 July 2011 (UTC)
 * Niiiice (you switched pounds for kilos, but I get the picture). Thanks. --Goodbye Galaxy (talk) 15:51, 13 July 2011 (UTC)


 * Also, if you are annihilating the human with an equal sized mass of antimatter, it would be 2x as big because the antimatter mass would count as well. Googlemeister (talk) 15:51, 13 July 2011 (UTC)


 * (EC x 2) The question was about 170 pounds, i.e. about 77 kilograms, which is equivalent to about 7 exajoules. However, I don't see how you could easily convert nearly all of the human into, say, photons without annihilating it with 77 kg of antimatter, in which case the total mass involved would be about 154 kg, which is equivalent to about 14 exajoules, which is close to your answer by coincidence.  Red Act (talk) 15:59, 13 July 2011 (UTC)
 * Yeah, I should have clarified in my question that the annihilation was due to magic. --Goodbye Galaxy (talk) 16:03, 13 July 2011 (UTC)

DNA question
What % of the weight of a human would their DNA be? Is it a significant amount or something like 1/1,000,000th of a percent? Googlemeister (talk) 15:37, 13 July 2011 (UTC)
 * According to this page there are about 6 x 10-12 grams of DNA per human cell. There are probably a few trillion cells in the human body (not counting red blood cells, which lack nuclear DNA); estimates are imprecise.  If those numbers are correct, you get several grams of DNA, a significant amount, although well under 1% of the total. Looie496 (talk) 16:28, 13 July 2011 (UTC)

(ec)It's easier to figure this out than look it up (I said before starting ;)) ... though someone ought to chase down a number so we can cite it in the article. To begin with,

TMP = 320.1926 g/mol; dAMP = 331.222 g/mol; dCMP = 307.197 g/mol; dGMP = 347.2243. A molecule of water (18.01528 g/mol) is lost from each of these on polymerization, and we always find A with T, G with C. That gives us 615.384 g/mol for a T-A base pair and 618.391 for a G-C base pair. The precise mass of one genome will thus depend on the GC-content very slightly, and of course will be proportional to the genome size. The first of many confounding biological factors creeps in when we realize that "the" genome size doesn't exist; NCBI listed 3,101,788,170 bases in a very nearly complete reference sequence, but individuals vary, and apparently there are still a few hard-to-sequence repetitive regions missing small bits of information. Still, to boldly take that number and plunge ahead, and using 41% for the G+C content (I can't find a more precise number - due to the repeat problem, and the fact that repeats have very unusual G+C contents, there may not be a better number even from all that sequence data) we get:

3101788170 * (0.41 * 618.391 g/mol + 0.59 * 615.384 g/mol) / 6.0221415 × 1023 /mol = 3.17 × 10-12 grams

This is the mass of a haploid genome per cell (such as sperm); most cells carry 2n (in G1 arrest) or 4n (G2 arrest, while preparing for mitosis, etc.); some carry vastly more (trophoblasts, etc.). But on average the cells get bigger in proportion to the number of genomes they have, so it's more the type of cell that matters.

For example, a sperm head is roughly 4-5 micrometers long; from a drawing of the typical sperm it appears 25/40 as wide and 13/40 as thick (but with a hollow spot in front, so let's call it, oh, 10/40); this gets us 4.5*(5/8*4.5)*(1/4*4.5)*(4/3)*(3.14) = 59.6 cubic micrometers = 59.6 x 10-12 cubic centimeters (=ml). (error corrected, sorry!) So one genome per sperm head works out to about 3.17 x 10-12 / 59.6 x 10-12 = 0.0532 g / ml = 53.2 g/l = 5.32% w/v. But as you see from this work, I could be off by quite a bit!

Now the "typical mammalian cell", according to cell nucleus, has a 6 micron round nucleus which is 10% of the volume. 6 * 6 * 6 * (4/3) * (3.14) = 904 cubic micrometers. Twice the DNA in such a space is still only 6.28/904 = 6.94 grams per liter, or 0.694 % (w/v). And in the cell as a whole it is one-tenth of that - 0.694 grams per liter or 0.0694%. Of course, that's not counting the extracellular space, which in some tissues is quite substantial... Wnt (talk) 16:52, 13 July 2011 (UTC)

Using fractionally distilled oil products to fractionally distill crude oil
It takes heat energy to bring a barrel of crude oil to the temperature required to fractionally distill it obviously, and the products of the fractional distillation have the ability to be used as energy. But how much crude oil can you fractionally distill from the energy you get out of whichever hydrocarbon is used as fuel after fractionally distilling one barrel of crude? In other words, you start with one barrel of crude, you use unknown energy given to you to fractionally distill it, you get products, including whatever X amount of product that can be used for fractionally distilling crude oil. How much crude can you distill with X? 20.137.18.50 (talk) 20:29, 13 July 2011 (UTC)
 * A lot more complex  especially since some of the products from the crude are, indeed, used as fuel in the process. And they do not use one single hydrocarbon for the purpose. Cheers. Collect (talk) 20:33, 13 July 2011 (UTC)
 * That is a complex question, and you aren't likely to get a solid answer in just a single number or quick sentenece of explanation. It depends a LOT on which distillation product you are using (propane, butane, kerosene, gasoline, etc.) as your heating source, and what the particular make-up of the crude is (different crude from different parts of the world have WILDLY different compositions).  I'm sure that, if given a specific formulation of crude, and a specific product of that crude, you could work it out trivially, but there's no guarantee that your answer will be widely applicable.  For example, if you know that your crude is 10% propane, and you know that propane generates 50 megajoules per kilogram, and you know how many joules of energy you need to fully distill the crude to its final products, you can work out if the system is self-sustaining or not.  However, such calculations would be purely pedagogical in the sense that the exact same set of calculations would need to be done for each application.  There's no universal number that you could apply to all crude.  -- Jayron  32  20:39, 13 July 2011 (UTC)
 * Yes, I didn't say it in so many words, but the question in my head as I was forming the question was about how self-sustaining or efficient the average refinery's average blend is, in terms of how much energy product is left after they use energy to make their products. It seems like when you add up all the energy that really goes in, not only considering the refining (which is the only thing I considered in my question), but also all the energy that goes into getting it out of the earth and transporting the crude from the drilling site to the refinery and from the refinery to the points of consumption for each type of product, the whole process must be very negative.20.137.18.50 (talk) 20:44, 13 July 2011 (UTC)
 * Non-negative net value of energy from petroleum prodution by a long shot. Elsewise, the industry would cease to exist. Collect (talk) 20:53, 13 July 2011 (UTC)
 * Energy returned on energy invested is an article on the topic. DMacks (talk) 21:41, 13 July 2011 (UTC)


 * If it was negative, it would not be a source of energy. Dauto (talk) 21:48, 13 July 2011 (UTC)


 * Waste heat recycling is an essential component of any production chemical engineering process, but the most efficient refinery processes are usually closely held trade secrets which depend on the detailed geometric configuration of the particular refinery. 99.24.223.58 (talk) 00:43, 14 July 2011 (UTC)

Practical Applications of Room-Temperature Superconductors
I'm writing a science fiction story in which a society with similar technological development to ours has developed a superconducting material that retains this property up to temperatures of 300-400 celsius. I'd like to add some color around the effects of such an invention, but not being an engineer, I'm at a loss. The article on technological applications of superconductors has some ideas (like more efficient tokamaks, the main point of the story) but it seems like superconductors operating at true room temperature (and, as a premise, reasonably cheap to make) would have more applications than the power grid and maglev. For instance, couldn't you use them as part of a telecom network by adding phase variances to the power without disrupting the transformers on either side? It's my understanding that in a superconductor although the electrons themselves wouldn't necessarily move particularly fast the electric current would move at almost the speed of light so the power grid would double as a fiber-optic network. Just an idea, might be wrong; any other thoughts? 24.215.229.69 (talk) 22:59, 13 July 2011 (UTC)
 * Superfast computing? -- Jayron  32  23:06, 13 July 2011 (UTC)
 * Just don't repeat the sort-of error of Larry Niven's Known Space series: a superconductor is not necessarily a perfect heat conductor. Or so I've heard... Wnt (talk) 23:16, 13 July 2011 (UTC)
 * Of course, the idea behind fiction is "to make stuff up for entertainment purposes". Thus, the idea behind science-fiction is "to make stuff up about science for entertainment purposes".  Also see Clarke's third law, which is intended to apply to science fiction.  Science fiction generally fails when it gets too technical, since it invariably gets more wrong the more it tries to make itself sound like "real science".  That's why Arthur Clarke wrote his third law; the idea is that you should just leave your advanced technologies somewhat "magical".  Let the reader know enough about it to know that it does work, without trying to make the reader know how it works, since the how is almost always wrong.  -- Jayron  32  23:24, 13 July 2011 (UTC)
 * Resistance is heat production, so presumably a room temperature superconductor could be cooled to slightly under room temperature and still be used to draw heat away from other components? I'm not sure what the point is either, to be honest.  I'd rather have more efficient electrolysis anodes, if we're going to be searching the space of alloys. 99.24.223.58 (talk) 05:08, 14 July 2011 (UTC)
 * Electric signals move at a good fraction of the speed of light in ordinary wires. If I recall correctly, the speed is 2/3 c in coaxial cable (like for cable TV). We don't use optical fibers due to the speed of propagation, but rather due to the fact that light can travel a long distance in a fiber without the signal degrading.--Srleffler (talk) 01:30, 16 July 2011 (UTC)

Cloud rays
Is there any name for the phenomenon when the corpuscular-like sun rays get the cloud's color (like the pink ones on the photo)?-- Brand meister t   23:17, 13 July 2011 (UTC)
 * Virga. -- Jayron  32  23:19, 13 July 2011 (UTC)
 * Thanx, updated the file info. Brand meister  t   23:29, 13 July 2011 (UTC)
 * Wait. That might not be right. Virga is rain that does't reach the surface. If it reaches the surface than it is called rain. Dauto (talk) 23:53, 13 July 2011 (UTC)
 * Dauto is correct. The image in question appears to feature two areas where precipitation is reaching all the way to the ground; these are called rain shafts (no article??). - Running On Brains (talk) 00:12, 14 July 2011 (UTC)
 * Right, that's rain backlit by the sun. Note also that the premise of the question isn't right:  sun rays don't get their color from clouds, rather the reverse. Looie496 (talk) 00:16, 14 July 2011 (UTC)
 * Strange, I thought they were rays, reverted. Apparently a file mover is needed then. Brand meister  t   00:37, 14 July 2011 (UTC)
 * I'm a filemover on Commons. What do you need it named to, "Backlit rain shafts"? --  T H F S W  (T · C · E) 17:32, 14 July 2011 (UTC)
 * Yep. Or something like that. Brand meister  t   11:07, 15 July 2011 (UTC)
 * I just made an article for rain shafts titled Precipitation shaft. Please feel free to contribute! BearGlyph (talk) 17:41, 22 April 2016 (UTC)

Antimatter bomb
How big would the explosion be from annihilating 1 kg of antimatter with 1 kg of normal matter? --134.10.116.13 (talk) 23:45, 13 July 2011 (UTC)


 * See Mass–energy equivalence. Remember that mass is mass, regardless of whether it is matter or antimatter.  Plug 2 kilograms into the equation for the mass, the speed of light for c, and you will get out the amount of energy.  For explosive energy, the standard is to convert the joules of energy into a TNT equivalent.  You can do that math pretty easily as well.  -- Jayron  32  23:54, 13 July 2011 (UTC)


 * As for how big the explosion would be, that's a bit more complicated than finding the yeild. In space the size of the fireball would roughly vary with the cube root of the yeild.  In a plane it would vary with the square root.  So, you get something between those two with a surface explosion. StuRat (talk) 02:33, 14 July 2011 (UTC)


 * The size, in terms of volume, of the exlposion itself will also be highly dependent on the local atmospheric conditions; for example the density of the air, which is itself dependent on things like temperature, humidity, and barometric pressure, and may not be uniform over the course of the explosion, complicating matters. That's why it is much easier to speak of the "size" of an explosion in terms of energy content (which is how the strength of explosive materials is usually quoted, in TNT equivalents which I cited above) rather than in terms of volume.  -- Jayron  32  04:28, 14 July 2011 (UTC)