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March 19

What is the scientific consensus or emerging consensus about whether homosexuals and bisexuals were born that way?

Like the science behind man-driven climate change, the science of same sex attraction is a controversial one. With the issue of gay rights heating up more and more in the U.S and around the world, I've started searching on the subject of homosexuality as most people now are. It still seems that the science of it is all over the place on that with some scientists saying that there's no conclusive evidence yet that homosexuals and bisexuals were born that way or not and other scientists saying that there's conclusive evidence homosexuals were born that way or not. Some scientists even question whether there are really homosexual non-human animals at all, if it is based upon instincts or if it is actual homosexual activity. Also, some people who go to one gender jails seem to get into same sex relations, appearing to show that at least some LGB weren't born that way, which confuses me. I don't know if some of the MSNBC Lockup episodes are accurate, but that's what they show. Willminator (talk) 04:35, 19 March 2014 (UTC)

See Homosexuality#Cause, Biology and sexual orientation, Environment and sexual orientation and Homosexual behavior in animals. Also, you can't conclude that a straight person who starts having a same-sex relationship for the first time in prison has changed their sexual preference. They may still have a strong preference for an opposite-sex relationship, but that's completely unavailable, so they're just resorting to a same-sex relationship as something that's at least somewhat preferable to no sex at all. A lot of MSM in prison aren't even willing participants; see Prison rape and Prison sexuality. Red Act (talk) 06:02, 19 March 2014 (UTC)

In some cultures other than the current Western conception, there's a notable difference in that while Two-Spirits and hijras/kothis take on a more or less homosexual identity, there are also a large number of ordinary "heterosexual" men who have sex with them - to the point where it seems like sex within the homosexual group may be the rarer relation! (I wonder if part of this cultural difference has to do with the oppression of homosexuals in Western cultures until after birth control had become available, which freed heterosexual women to have casual sex?) Wnt (talk) 11:32, 19 March 2014 (UTC)

From the second paragraph of our article on Homosexuality: "There is no consensus among scientists about why a person develops a particular sexual orientation...". The entire article is well worth reading. In practical terms, human sexual behaviour is so complex that a full explanation is probably not yet within our grasp. RomanSpa (talk) 14:41, 19 March 2014 (UTC)

But is there a scientific consensus or emerging scientific consensus on whether or not homosexuality and bisexuality is an inborn trait some people have? What does it mean by "develop?" The second paragraph makes it sound, but not clear enough, as if the scientific consensus is that homosexuality is something people are not born with, but that is developed some time in life. The emerging consensus in the non-scientific world is that homosexuality is an inborn trait according to the polls. Willminator (talk) 02:41, 20 March 2014 (UTC)

No, the word "develop" does not at all necessarily imply that the trait isn't inborn. Many human traits develop before birth, i.e., develop during prenatal development. And the second half of the sentence that RomanSpa half quoted is important: "... however, biologically-based theories for the cause of sexual orientation are favored by experts, which point to genetic factors, the early uterine environment, or both in combination." I.e., although there isn't a consensus on the matter yet, experts on the subject currently favor the idea of homosexuality being caused by one's genes (which are determined at the time of conception, which occurs before you're born) and/or early uterine environment (which is something that you're only exposed to before you're born). I.e., the emerging consensus in the non-scientific world that homosexuality is an inborn trait is consistent with current scientific understanding. Red Act (talk) 05:18, 20 March 2014 (UTC)

• They knew something was up with me when I made a pass at both the the doctor and the nurse. μηδείς (talk) 23:22, 19 March 2014 (UTC)

Uh oh, serious gender stereotyping there. Richard Avery (talk) 08:22, 20 March 2014 (UTC)

Yes, I was born back in the day when people took their gender stereotypes seriously. μηδείς (talk) 16:55, 20 March 2014 (UTC)

Richard is being sexist if he associates doctor with a man, and nurse with a female. Imagine the plot twist: the doctor was a woman, the nurse a man, Medeis' comment still makes sense. — Preceding unsigned comment added by 185.13.202.241 (talk) 20:29, 20 March 2014 (UTC)

Supongo que puedo creer por su orígen que tu comentario fue acto de vandalismo?

• • Did you likewise call on the lady with the alligator purse? If you don't know that reference, then just skip it. Or even if you do. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:53, 20 March 2014 (UTC)

Age of search engines. Wnt (talk) 02:34, 20 March 2014 (UTC)

I take it this is to the same tune as Miss Susie? But it's a much less interesting song. --Trovatore (talk) 08:05, 21 March 2014 (UTC)

Smoking alcohol - how does this work (if it does)?

As demonstrated by YouTube's famous LA Beast. The pump is somehow making the alcohol come out of the drink and into vapour form? How does this work - assuming that the Beast isn't messing with us for the lulz. I should probably say that I have no intention of trying this - and neither should any of you. --Kurt Shaped Box (talk) 14:50, 19 March 2014 (UTC)

We have an article about Alcohol_inhalation. I recall seeing novelty shops selling vapor by the minute out of a kiosk in a few US airports, back in the aughts. SemanticMantis (talk) 14:57, 19 March 2014 (UTC)

Alcohol vaporizes at a lower temperature than water, so heating it is one method to draw off the alcohol vapors (think cherries jubilee or bananas foster). I believe lowering the pressure might work, too, but somebody else will need to confirm that. StuRat (talk) 20:09, 19 March 2014 (UTC)

Besides the question of, "What do you expect it to do when you light it?" there's the issue that ethanol is a noxious, dessicating, toxin. We drink it in very diluted fashion, and still it kills the strongest of humans. Spiking an IV drip sounds better than inhaling alcohol fumes. Even a vodka enema. μηδείς (talk) 23:20, 19 March 2014 (UTC)

Those alcohol fumes are probably quite dilute, too (a low partial pressure in air). StuRat (talk) 05:12, 20 March 2014 (UTC)

A vodka enema, now that could kill you in short order. 24.5.122.13 (talk) 05:48, 20 March 2014 (UTC)

I suppose I didn't mean the volume that implies. More like a suppository vokda shooter. μηδείς (talk) 16:53, 20 March 2014 (UTC)

Yeah, but Beast has bigger arms than Christopher Hitchens. How does the bike pump thing he's doing specifically work though - anyone know? --Kurt Shaped Box (talk) 11:06, 20 March 2014 (UTC)

Sure sounds like it's lowering the pressure to draw the alcohol fumes out. StuRat (talk) 01:37, 22 March 2014 (UTC)

Secondary alkyl halides do not undergo SN1/ E1 reactions?

According to the latest edition of Bruice's organic chemistry textbook, recent research has found that "Secondary alkyl halides do not undergo SN1/ E1 reactions" (source: see here and click on "new to this edition"). Is this true? Can someone find me a peer-reviewed paper about this? How come scientists didn't notice this before?--FutureTrillionaire (talk) 18:17, 19 March 2014 (UTC)

I have that actual Bruice book, and the SN1 section on p417 cites this claim to

Murphy, T.J. (2009). "Absence of S_N1 Involvement in the Solvolysis of Secondary Alkyl Compounds". J. Chem. Ed. 86: 519–524. doi:10.1021/ed086p519.

The current (and previous) McMurry organic chemistry text gives relative SN1 reactivity of 1,000,000:1 2-methyl-2-bromopropane:2-bromopropane, and only mention 3° (and allylic/benzylic) but not simple 2° alkyl halides as common SN1 substrates in the SN1/SN2/E1/E2 reaction comparison summary, so I'm not sure this is really strictly "recent research", so much as making explicit a blanket "not 2°" rather than "2° possible but so very much slower than 3° that may or may not be viable" that may have been commonly taught. I don't have a previous edition of Bruice handy to see what they do/don't claim for possibilities or rates. The current McMurry (copyright 2012) gives specific example of E1 of a menthyl chloride, a 2° halide, using its product distribution to verify that mechanism vs E2, whereas the current Bruice only discusses the E2 possibility of it (in keeping with its basic claim that 2° C+ are too unstable to be a viable intermediate). DMacks (talk) 19:03, 19 March 2014 (UTC)

That Murphy paper makes a strong case for "no SN1 at 2° alkyl halide", including explaining the apparent racemization during substitution of these substrates (the typical observation used to support SN1 rather than SN2 as the mechanism) based on an alternate pathway involving (possibly repeated) successive SN2 steps. The article does not mention elimination. , and a quick glance at the elimination chapter only refers back to the substitution chapter as the basis for ruling out E1 of 2° halides based on the "relatively unstable carbocations" that would be required (p456–457). DMacks (talk) 19:19, 19 March 2014 (UTC)

Thank you for the explanation! I have the 6th edition of the Bruice textbook, and it says in a chart that 2° alkyl halides undergo both SN1 and SN2. Also it has a chart that looks something like this:

alkyl bromide	class	relative rate
tert-butyl bromide	3°	1,200,000
sec-propyl bromide	2°	11.6
ethyl bromide	1°	1.00

I think you're right that in the 7th edition, Bruice decided that the rate of 2° is negligible compared with 3°. However, does this mean that we can't perform a SN1 reaction using a 2° alkyl halide in real life?--FutureTrillionaire (talk) 20:44, 19 March 2014 (UTC)

The problem with that is, for secondary alkyl halides the SN2 (or E2) reactions are so much more favorable that you'd have a hard time forcing the stuff to undergo an SN1 reaction instead. 24.5.122.13 (talk) 23:18, 19 March 2014 (UTC)

It is also very important to remember that these are not either/or propositions. It's better to think about the SN1/SN2/E1/E2 as a "continuum" rather than a set of choices. You're likely to get actual products from all 4 mechanisms in just about every nucleophilic reaction (at least a few molecules!) the question is how a set of reaction conditions (including the structure of the nucleophile, the structure of the electrophile, the nature of the solvent, the temperature, the relative concentrations, etc. etc. etc.) will result in a particular distribution of mechanisms. It isn't correct to think "Tertiary bromides don't undergo SN2/E2 reactions ever" It's better to say "unimolecular mechanisms dominate the reaction of tertiary alkyl halides" for various reasons (stability of carbocation; steric interference at the attack site, planar attach site in the carbocation, etc. etc.) The problem always comes at the edge cases; how much better does an SN1 mechanism have to dominate a reaction for it to be the dominant reaction type? Is a 51/49 ratio enough? 80/20? 95/5? 99/1? How much does one mechanism have to dominate the reaction for us to say that the other mechanisms aren't happening to a significant extent. The problem may likely come from different chemists looking at the same set of data and arriving at different definitions of "enough". --Jayron32 02:55, 20 March 2014 (UTC)

How to refer to an antibiotic which is used to select against eukaryotic cells?

Puromycin is an antibiotic. It is effective against microbes and can also kill and be used for selection against unprotected eukaryotic cells. When it's activity against microbes is immaterial how can I refer to it? A "selective agent" or still as an antibiotic? --129.215.47.59 (talk) 18:35, 19 March 2014 (UTC)

When in doubt, specify, especially if this is for research or academic writing. E.g. "We used Puromycin, an antibiotic which was chosen for this purpose because of its selective properties when applied to eukaryotic cells. In this application Puryomycin acts to ...[kill some and leave others, based on some property]([citation])" Once you've specified, you can even set up a shorter term for later use, E.g "...(henceforth, 'selctive agent')." SemanticMantis (talk) 19:25, 19 March 2014 (UTC)

The term biocide also applies, but I think the solution above is more plausible to read in a real paper. Wnt (talk) 22:27, 19 March 2014 (UTC)

Given the terse style often used in papers (often the result of publishers' word limits), I would expect something very brief like "Puromycin was used for selection of [whatever] under [some conditions] ([citation],[citation])" in the materials and methods, and selection agent or just plain puromycin elsewhere (the latter having the twin advantages of being both more specific and shorter). The expert reader will already know that puromycin is widely used as a selection agent, and will pretty much assume that is its role if it shows up in eukaryotic culture. (Pull the full text of some papers mentioning puromycin to see lots of examples.) TenOfAllTrades(talk) 22:59, 19 March 2014 (UTC)

Alright, sociology experiment: Free hits for puromycin selection pull up: "podocyte toxin" [1] "widely used drug/selection marker/protein synthesis inhibitor" [2] only "puromycin selection" [3] only "puromycin selection" [4] and "antibiotic used as a selectable marker" [5]. Bottom line is that biology isn't a very regular kind of pursuit. :) Wnt (talk) 02:44, 20 March 2014 (UTC)

Research project ideas for civil engineering

What would be a good research project to write a thesis, for college final year majoring in Civil Engineering which incorporates looking at all parts of an airport rather than just specialised parts of it such as impact loading on runways, materials used on taxiways, geometric design, fire engineering on the terminal structure, materials used for the terminal structure etc. These examples only look at small parts of the airport. Is there anything suitable for civil engineering majors that would involve looking at the entire airport? 82.40.46.182 (talk) 18:46, 19 March 2014 (UTC)

If you're interested in the ergonomics of airport design, some airports seem to almost totally ignore the impact on passengers. My local airport, for example (DTW), is an absolute disaster. Some of the problems:

1) Long-term parking requires taking a bus to the terminals, which involves delays waiting for the bus, waiting for it to let people off at other terminals, etc. (LAX is even worse in this respect, where I got on the bus, then had to wait for the driver to take a dinner break.) There is often closer short-term parking, but that's absurdly expensive if you need to leave your car there while on vacation.

2) You then often have a long line to check in, then a long line to get through security (which involves removing every bit of metal, and God help you if there's a metal zipper on your pants), then a long walk to the gate, then a long line to get your gate pass. It seems like at least some of those steps could be combined.

3) For some reason, the long walk to the gates at DTW involves going up and down, as the walkway has several dips in it. This can be exhausting, if carrying heavy carry-on luggage.

So, I'd redesign the airport from the POV of how to get long-term passengers to their gates in the shortest time. One design might involve a massive underground parking structure in the center for all cars (short-term and long-term) connected by underground tunnels with automated conveyor belts to passenger terminals surrounding it on all sides, and runways around those on all sides, and a ring of cargo terminals beyond those, with fuel depots, warehouses, hangars, and maintenance facilities at the very outside.

If you need to take a bus to get from parking to the terminal, that design is a failure, IMHO. You also shouldn't need to go outside from the parking area to get to the terminals. Rental cars should be picked up and dropped off in the central underground parking area, too.

With the current poor airport design, I've found I can drive to Toronto from Detroit in less time (about 4 hours), less expensively, and with less hassle, than I can fly there (although the actual flight takes only 40 minutes). And if you happen to be in a wheelchair, airports are even more of a disaster, so look at wheelchair accessibility, too (keeping everything on the same level helps there). StuRat (talk) 19:14, 19 March 2014 (UTC)

How about examining the management of a project to construct a new airport from scratch? Such a project will require a full understanding of all the things you mention, along with the sequencing of their construction, the management of resource delivery, infrastructure, testing procedure, and many others. A particular challenge would be to consider this for a military airfield, where there are very specific requirements that must be met as quickly as possible. Here are a few links you might start with: Military airfield, FAA on Airport Construction, Ledcor construction. Good luck! RomanSpa (talk) 19:30, 19 March 2014 (UTC)

For a whole-system approach, I'd think of something involving logistics. Many things need to go in/out of an airport to support a successful flight: e.g baggage, food, fuel, maintenance staff, flight crews, passengers, etc. SemanticMantis (talk) 19:31, 19 March 2014 (UTC)

Things like ergonomics and logistics sound interesting but are they suitable for civil engineering majors? They sound more like something for an architecture major or maybe a management major. 82.40.46.182 (talk) 19:36, 19 March 2014 (UTC)

Well, in my design, you could put the control tower directly over the underground parking, and would need to reinforce the parking areas to withstand a terrorist bombing without taking out the control tower. This could involve using arches instead of just cantilever supports, for example. A redundant external frame design for the control tower is particularly hard to take out. Does that qualify as civil engineering ? StuRat (talk) 19:45, 19 March 2014 (UTC)

I'd argue that a civil engineering student project on airports as whole systems should consider how the infrastructure will support logistics flights. Otherwise, what is the point of all that concrete and steel? SemanticMantis (talk) 13:44, 20 March 2014 (UTC)

The Small Shrink

Given relativity, couldn't we say that we (and all matter in the universe) are shrinking in relation to the observable universe? Just as the observable universe is in theory a "white hole" from the perspective of a black hole.165.212.189.187 (talk) 20:11, 19 March 2014 (UTC)

If the universe were shrinking instead of expanding, would distant galaxies still be red-shifted? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:09, 19 March 2014 (UTC)

This was making the rounds last year. [6] I won't try to estimate its plausibility, but maybe someone else will. Of course, in reality, "there is no spoon" :) Wnt (talk) 22:25, 19 March 2014 (UTC)

All kinds of weird stuff makes it onto the arxiv. Physicists have ignored this paper, and probably for good reason.

There is cosmological and geological evidence that the microscopic laws of physics that set the size of physical objects haven't changed since the very early universe. I don't have a good source for this but here's one paper that mentions various sources of evidence. It's much easier and seems much more sensible to base length standards on those laws than on a cosmological scale factor. From a philosophical-relativist perspective (heh) I suppose you can go either way, but that doesn't mean that "we're shrinking" is a viable alternative to the standard cosmology—the point of relativism is that it's not a new idea at all, but the same idea described in different words. Special and general relativity have nothing useful to say about this since they're not related to philosophical relativism in anything but name.

I don't think the observable universe is a white hole from the perspective of a black hole, either (i.e. I don't think the term "white hole" is normally used that way). -- BenRG (talk) 23:05, 19 March 2014 (UTC)

• We are used to things flying apart under continued momentum due to an explosion. What is the cause of the shrinking, and why does it continue? Over short distances we notice that bodies do move together, as well as fly apart. Why don't we notice that bodies grow and shrink in relation to each other? The space between non-gravitationally bound objects is expanding. The distance between the sun and the earth is not expanding. Are the sun and the earth stable in regard to each other, growing in regard to the approaching Andromeda Galaxy, and shrinking in regard to the rest of the universe? Were the chemical properties of carbon atoms different a billion years ago when they would have been significantly bigger than they are now? Ockham's Razor μηδείς (talk) 23:04, 19 March 2014 (UTC)

I was thinking of a scenario where two distant objects' center points are stationary relative to each other but because they are "shrinking" they only "appear" to be moving apart.165.212.189.187 (talk) 14:23, 20 March 2014 (UTC)

There's nothing wrong with playing with such models if you can do the math right. You might want to ask this question again (just copy and paste the whole discussion) at the math desk.μηδείς (talk) 16:50, 20 March 2014 (UTC)

Toothpaste on burns: reality and myth

Does or did it work in some case? Different toothpastes have different ingredients, so, maybe some old toothpastes were good for it, and hence the belief that toothpaste (in general) is good for burns. What if some toothpaste manufacturer decides to change the formula to include something that's really good for the teeth, but really bad for a burn injury? Should they cover this off-label use, even if it's nonsense? OsmanRF34 (talk) 20:51, 19 March 2014 (UTC)

There actually could be some beneficial effect. First, it could act as a sort of heat sink (cooling effect) and if it contains actual mint extract (see: menthol) or peppermint (see: WebMD), it would have an analgesic effect. As to the 2nd part of your question, I checked my toothpaste and there is nothing in that regard (but it did list an 800-number for "questions or comments"). Note: this is not medical advice; just suggestions for finding sources for answers to your query.  ~:71.20.250.51 (talk) 21:24, 19 March 2014 (UTC) [added note:71.20.250.51 (talk) 21:40, 19 March 2014 (UTC)]

Almost anything you put on a burn that isn't quantities of cool water, or as close as you can get, is going to be worse than using quantities of cold water, and they'll have to wash it off the damaged skin before they can treat the burn when you get to the hospital. Toothpaste is an abrasive polish: do you really want to be applying an abrasive to an injury? And any cooling effect will quickly be lost when the toothpaste warms to body temperature, which won't take long: that's why you try to run burns under cold running water, if possible: the water would warm up, otherwise.

People do terribly stupid things to burns. They think that they should apply butter: butter manufacturers do not require a disclaimer for this, because they have never claimed that this terrible idea was sensible. The disclaimers all end up on first aid materials, telling you that no really, don't do that, just run it under cool water. 86.157.148.65 (talk) 18:35, 20 March 2014 (UTC)

Butter's disclaimer: do not use on burns, do not consume too much due to risk of obesity, do not use for anal sex. — Preceding unsigned comment added by 185.13.202.241 (talk) 20:16, 20 March 2014 (UTC)

Beans should have disclaimer: "Do not put beans up your nose."  — Preceding non-sequitur added by 71.20.250.51 (talk) 20:34, 20 March 2014 (UTC)

Behavioral epigenics

How does changing our behavior alter the expression of a gene that could affect future generations? Maybe before conception? I'm confused as to the effect of our actions shaping the lives of our children, or grandchildren. When should the change occur to make a difference? — Preceding unsigned comment added by 96.24.184.152 (talk) 21:30, 19 March 2014 (UTC)

Well, since we are talking about inherited characteristics, it would have to happen before conception, in the case of the father. The mother's behavior might also have an epigenetic impact on the baby during pregnancy. Starving oneself almost to death would be one behavior that might have an impact. Of course, you could also starve the child after birth, and thus your behavior could affect the epigenetics that those children then pass down to their children. StuRat (talk) 21:42, 19 March 2014 (UTC)

I was very impressed by [7][8][9]. Note however that humans have a much reduced sense of smell and a much less elaborate brain structure to process it, so it is not guaranteed to work the same way there. Also see [10]. Those are the two that popped first to mind - for more see behavioral epigenetics. Wnt (talk) 22:21, 19 March 2014 (UTC)

Sounds like Lysenkoism to me. --DHeyward (talk) 05:37, 20 March 2014 (UTC)

There are elements of lysenkoism in these current theories. What we're homing in on is a system in which the resulting organism is mostly determined by classical Mendelian inheritance laws - have some relatively tiny influence comes from these effects that look a lot like lysenkoism. It's not a large effect - but it does seem to be there. SteveBaker (talk) 19:19, 21 March 2014 (UTC)

Cutting dead leaves off plants

Should I cut them off while still "juicy" or wait until they are all dried out ? StuRat (talk) 22:23, 19 March 2014 (UTC)

If the leaves dry and drop spontaneously from base of the the petiole (botany), you avoid risking damaging the plant by plucking them and taking stem tissue with them or breaking the stem accidentally. If the leaves do not drop by themselves, or if they are diseased cut them off as close t the petiole without damaging the stem as possible. So yes, let them dry, unless there's some good reason otherwise. μηδείς (talk) 22:50, 19 March 2014 (UTC)

Here's a better image of the base of a leaf. If you must cut, avoid cutting the stipule or the axillary bud. But the best way is to wait until the leaf falls of its own accord with a slight breeze or touch. μηδείς (talk) 22:58, 19 March 2014 (UTC)

If I wait until it's dried out, then I can cut off all of dried part, right? StuRat (talk) 23:15, 19 March 2014 (UTC)

(EC, basically agreeing with Medeis above) This can vary by plant. In general, wait until they are dried out. nitrogen translocation or retranslocation come into play, and let the plant 'recycle' nutrients by moving nitrogen and other useful compounds into storage organs, that can later be used to make new leaves. (both of those are surprising redlinks, best I can find on WP is a terse statement at the disambig for translocation... see e.g. [11] for the idea). A classic example of people doing it wrong: when people plant bulbs like narcissus or hyacinth, they often cut off the greens before they are brown, because they are considered inaesthetic. However, that's the worst thing to do, and deprives the plants of resources, and will result it poor plant performance the next year.

There are also considerations as to why leaves are dying. If it's seasonal die-off, then absolutely leave them. Entering seasonal dormancy for an outdoor plant is unlikely in the USA this time of year. If it's a disease of some sort (indicated by patterned or spotted browning on leaves), then remove leaves as soon as possible, to prevent further sources of infectious agents. If you want more specific advice, I could do much better with at least the family_(biology) of the plant, a photo, or even a description (e.g. indoor or outdoor, woody or herbaceous, in pot or in ground, etc.) SemanticMantis (talk) 22:59, 19 March 2014 (UTC)

Agreed it's strange the redlinks we have on plant biology. I can't even find a good image of the parts of a leaf. Stu should understand the importance of nutrient reabsorption in general, but also be reassured that once the leaf is full dry there will be no more transport.

The lower leaves on this particular plant seem to naturally die off as it grows taller. StuRat (talk) 23:11, 19 March 2014 (UTC)

• A picture really would be best, can you upload one? If it is just old leaves and not actual stem that is dying you should avoid cutting. If the main stem is dying, let us know. In most plants, old senesced leaves will simply fall by themselves when ready will simply pop off at the pulvinus (the little bulb like you find at the end of elm and oak petioles) if you touch them lightly or blow on them. You should never have to apply enough force to pluck them, as this may cause green stem to snap and tear away tissue below the stipule (see the picture I linked to).

An exception will be monocots like grasses and lilies where the leaf often wraps around the base of the stem. These too should always be let stand unless they are dying of a pest or fungus (in which case, you have to amputate). Once they are dry remove gently at the base with knife or scissors as necessary always avoiding damaging the stem. The big hint is "do no harm". μηδείς (talk) 23:54, 19 March 2014 (UTC)

I guess this is some type of a vine, as it keeps growing upwards yet can't support it's own weight. (I've transplanted a part that broke off, and am now supporting the 2 stalks as best I can.) StuRat (talk) 00:00, 20 March 2014 (UTC)

"Vine" is a shape, like tree or herb, not a family of closely related plants. It could be anything from Spanish Moss to English Ivy to various jade plant relatives. Ivies generally have one long, week growing axis, with leaves on one side, and adventitious roots at the basis of the leaves. You may simply have a sun-loving plant that needs direct sun and pruning to encourage it to branch out, rather than keep growing in one direction as if searching for the One Ring. μηδείς (talk) 00:20, 20 March 2014 (UTC)

March 20

Mass in Planck Density

The article on Planck density states that "At one unit of Planck time after the Big Bang, the mass density of the universe is thought to have been approximately one unit of Planck density." What type of matter did this "mass density" consist of? Star Lord - 星王 (talk) 10:27, 20 March 2014 (UTC)

That period of time is the Planck epoch. It occurred so early, and its duration is so short, that it's difficult to describe in non-mathematical terms. Essentially, the time-period is so short and the energy density is so large that it is non-sensical to describe interaction between entities. Everything we know about interactions between entities is summed up in the four fundamental interactions; during the Planck epoch, these activities are indistinguishable from each other. Physicists who describe this era tend to stick to discussions about symmetry and symmetry-breaking - of the entire universe - instead of attempting to discuss individual elements within the universe. Every object was so "smushed" together - and, simultaneously, spread out to fill the entire universe - that it doesn't make sense to describe anything as a particle with a position or a volume or a means of interaction among other particles.

So, the "mass density" in that era is best thought of as just a property of the whole universe. Nimur (talk) 13:56, 20 March 2014 (UTC)

Thank you, @Nimur: . You mention that it is difficult to describe in non-mathematical terms. Please do describe it in mathematical terms if you think it will clarify matters. I am comfortable with the maths in Quantum Mechanics. Star Lord - 星王 (talk) 16:26, 20 March 2014 (UTC)

I'm not the best person to present this stuff mathematically - I'm not a practicing cosmologist! But I think I can safely say that nobody has yet provided a satisfying mathematical description that answers all the questions: there is no model that is both consistent with our present knowledge (about the standard model and the fundamental interactions) and that convincingly evolves a Planck-epoch universe through the various symmetry breaks necessary to yield a universe like our own.

In lieu of a mathematical presentation from me, here's a pretty good technical talk by George F. Smoot, who has a unit of length named in his honor. As you will no doubt see, real physicists address the problem by looking for the observable effects of the early universe, using tools like the COBE satellite and the WMAP to constrain mathematical models of mass and momentum during the Planck era. This approach is a lot more productive than trying to simulate the Planck-era conditions and forward-project their time evolution; but it means there's no "equation" to plug and chug; it's not exactly like modeling the hydrogen atom using quantum-mechanical equations. Nimur (talk) 04:34, 21 March 2014 (UTC)

A short side-question. Since it is called "mass density", would it be fair to say that there was "mass" in the Planch Epoch? Star Lord - 星王 (talk) 16:56, 20 March 2014 (UTC)

I think you need to use an incredibly broad definition of mass; something along the lines of "mass is a scalar property subject to certain conservation laws that are governed by fundamental symmetries of the universe." Even if we consider a broader "mass-energy" quantity, you still need to be cognizant that gravitation is a fundamental interaction for which the time- and length-scales of mediation might have been larger than the size and age of the universe during the Planck epoch. That's what defines this stage of the early universe as its own "epoch" : it is that time period during which definitionally the time- and length-scales were smaller than those which govern fundamental interactions as we know them today. Nimur (talk) 04:34, 21 March 2014 (UTC)

Hmmm, to put this into perspective, as I recall a black hole containing a Planck mass has a Schwartzschild radius of the Planck length. It's the smallest a black hole can be because the Compton radius of the entire mass of the hole would be larger than the Planck length, i.e. everything inside the hole smooshed together. But what I don't get is that while a Planck mass is a somewhat impressive explosion, it sure as hell isn't the mass-energy of the universe! And an evaporating black hole doesn't start a new universe, right? Wnt (talk) 14:19, 20 March 2014 (UTC)

The binary encoding of the Holographic universe needs one unit of Planck area to mark with a "1" for each unit of Planck mass within it. When the Universe was at Planck density, it had a cube root of the needed area. Hence explosive Cosmic inflation to correct for this, followed by the current Quintessence to give us room to breathe in. Hcobb (talk) 14:20, 20 March 2014 (UTC)

Can you explain that? How would the universe be at the wrong density...? Never heard of anything like this! Wnt (talk) 14:46, 20 March 2014 (UTC)

I think Hcobb made it up. Anyway, it's not true. -- BenRG (talk) 18:30, 20 March 2014 (UTC)

In quantum gravity, Planck-scale black holes, if they're possible at all, probably are not well described by general relativity. In classical general relativity, a Planck-mass black hole would have a Schwarzschild radius of twice the Planck length, because r_s = 2GM/c² and in these units G = c = 1. I don't think this is particularly interesting. Anything involving Planck units and the constants G, c, ħ is going to give you a result that's small in Planck units because they're defined that way. -- BenRG (talk) 18:40, 20 March 2014 (UTC)

I should emphasize that Micro black hole currently says exactly what I did, that indeed the Planck mass is as small as a black hole can get. If the universe passed through a time when it had about the size and about the mass of one of these smallest black holes, this seems more than a little interesting. Wnt (talk) 20:10, 20 March 2014 (UTC)

That paragraph of the article is unsourced. I don't know why having a Compton wavelength larger than the Schwarzschild radius would be a problem. Pions have a diameter of ~1 fm and a Compton wavelength of ~9 fm. Electrons have a Compton wavelength of ~2000 fm and no detectable size at all.

This page quotes Leonard Susskind saying "there is no fundamental difference between elementary particles and black holes" (and that 't Hooft agrees), and here's a random arXiv paper that talks about black holes with sub-Planckian masses in loop quantum gravity. I'm not saying that they're right, but if there's a simple no-go argument against sub-Planck-mass black holes, they haven't heard of it.

I certainly agree that the physics of black holes and the early universe is interesting, but statements like "an object with the Planck mass has a Compton wavelength of the Planck length and light will take the Planck time to cross that distance and..." are tautologies with no physical content, and arguments like "no black hole can have a mass larger than the Planck mass because then its Compton wavelength would be smaller than the Planck length and the Planck length is the smallest possible length" are unjustified given our current near total lack of understanding of Planck-scale physics. -- BenRG (talk) 04:13, 21 March 2014 (UTC)

That paper makes for interesting reading. I'm not a competent judge of its significance/reliability and I didn't find a journal publication by that name with a simple search or I'd have added it to the article I mentioned, but I welcome you to update it if it is appropriate. Wnt (talk) 01:13, 22 March 2014 (UTC)

I removed the sentence from the article because in inflationary cosmology (for which there is brand new experimental evidence!) the early universe was never that dense. Also, no one understands Planck-scale physics and I think it would be better to avoid Planck-unit numerology in Wikipedia articles in general. -- BenRG (talk) 18:30, 20 March 2014 (UTC)

For what it's worth, in the inflationary epoch of inflationary cosmology (which is also the densest epoch) the universe is empty except for an inflaton [sic] field that is similar to dark energy but with a much higher energy density. There are almost no particles; it's a vacuum. -- BenRG (talk) 18:40, 20 March 2014 (UTC)

How can you have a universe full of energy and not have it full of particles? (hmmm, come to think of it, was there just not time for pair production?) Wnt (talk) 19:20, 20 March 2014 (UTC)

It's similar to the situation now, where most of the energy density is in the dark energy/quintessence. -- BenRG (talk) 04:13, 21 March 2014 (UTC)

Well, the current ratio isn't really that far off from 1:1 - I don't have the knowledge to say whether some kind of equipartition theorem applies when all degrees of freedom are considered, but I wouldn't call our universe a vacuum. Was there anything near that much ratio of ordinary matter in the inflationary period? Wnt (talk) 01:13, 22 March 2014 (UTC)

Yes, it's more like the situation in the far future (according to ΛCDM) where the accelerating expansion continues and the density of ordinary matter asymptotically approaches zero. In order to explain the observed homogeneity of the universe, inflation has to last long enough that any relics of whatever preceded it are diluted to undetectable levels. Actually, I was wrong when I said there were no particles, because there is Hawking/Unruh radiation from the de Sitter horizon (both during inflation and in the future of ΛCDM cosmology). But that's random quantum noise that's uncorrelated with whatever matter you started out with. -- BenRG (talk) 08:06, 22 March 2014 (UTC)

Since the inflationary field decayed to our current false vacuum, when will that decay to a true vacuum and clean everything up? Hcobb (talk) 19:38, 20 March 2014 (UTC)

The quintessence may be the true vacuum, in which case it will never decay, or it could be a false vacuum, in which case it will randomly decay with some half-life that we have no way of determining, or it could be on a slow roll like the inflaton in which case it won't decay as such but will turn into particles at a time that's predictable in principle but totally unknown in practice, except that I think it would have to be in the very far future. Or it could do something else entirely. -- BenRG (talk) 04:13, 21 March 2014 (UTC)

I take it then that you're not a great believer in the heat death of the universe either :) Wnt (talk) 10:58, 21 March 2014 (UTC)

What do you mean? -- BenRG (talk) 08:06, 22 March 2014 (UTC)

Thank you for your interesting answers, Nimur and BenRG. When I read the sentence "At one unit of Planck time after the Big Bang..." I interpreted that time as being just at border between then Planck Epoch and the beginning of the Grand unification epoch. I had already come to the conclusion that I would not be able to get many answers about the Planck Epoch, and I was really wondering about whether mass could have been said to exist in the beginning of the next era according to the standard theory, which I assume to be the Grand unification epoch. Star Lord - 星王 (talk) 17:05, 21 March 2014 (UTC)

The thing I still wonder about the inflationary period is what the "subjective time" would have been like for its inhabitants. Because it was expanding at an absolutely mind-boggling rate, the entropy would have been increasing at a similarly incredible rate. Entropy is information, so... does this mean that a sentient structure during that era would perceive it as lasting for an extremely long time? Wnt (talk) 01:13, 22 March 2014 (UTC)

From the perspective of someone living in it, de Sitter space is actually static and time-symmetric. It's similar to a black hole turned inside out: you're surrounded by a spherical event horizon which is gravitationally attractive and sucks up everything around you. (A similar horizon can be defined for any other object, so they're no worse off than you; you can't fall through your horizon by construction, but you can fall through theirs.) According to ΛCDM we'll end up in that situation eventually, with everything but the local supercluster falling through a horizon with a radius of about 18 billion light years. The inflationary epoch is similar except that the radius is only a few orders of magnitude larger than the Planck length. But aside from scale, these eras are similar enough that Roger Penrose actually proposed that they're the same. (I don't mean to endorse that idea, which is probably wrong; I just think it's cute.) -- BenRG (talk) 08:06, 22 March 2014 (UTC)

I think that at the GUT scale you would have something like a quark-gluon plasma, but with the GUT fields, whatever they are, instead of quarks and gluons. The phase transition between the GUT scale and the "quantum gravity scale" would be somewhere in the GUT-to-Planck energy range, but it wouldn't be right smack up against the Planck end of that range. The range is fuzzy anyway since the Planck scale is just the general sort of order-of-magnitude scale at which quantum gravity is expected to matter. To get a better estimate of the right scale you need a theory of quantum gravity. The Planck units are off by a factor of ${\sqrt {8\pi }}$ from the get-go because they were defined using Newton's G instead of Einstein's 8πG as the gravitational constant, and there are certainly other correction factors from quantum gravity. So even if there is a special time/mass/whatever, it's unlikely to be exactly one Planck unit. -- BenRG (talk) 08:06, 22 March 2014 (UTC)

Thank you again, BenRG. My question is really only "linguistically" based. How can one have "mass density" without mass? Star Lord - 星王 (talk) 08:23, 22 March 2014 (UTC)

Mass density is just energy density divided by c². If by mass you mean the rest masses of the fundamental particles, even in ordinary matter that's only a tiny part of the total mass/energy—compare the bare up and down quark masses of 2 and 5 MeV with the proton mass of 900 MeV. Most of your mass comes from a complicated configuration of color-charged fields and not from particles as such. -- BenRG (talk) 18:03, 22 March 2014 (UTC)

Thank you BenRG and Nimur.Star Lord - 星王 (talk) 18:47, 22 March 2014 (UTC)

Resolved

Bridge columns

Why are bridge columns normally round? 194.66.246.45 (talk) 11:59, 20 March 2014 (UTC)

When you say "columns" do you mean piers? Alansplodge (talk) 14:21, 20 March 2014 (UTC)

An example of the early archaic Doric order- Temple of Poseidon in Paestum, Italy.

Well, I don't think they mean one of these; as you can see, it's not round at all. --50.100.193.30 (talk) 01:59, 22 March 2014 (UTC)

Few modern bridges have round columns, see Bridge; they more often have rectangular uprights called piers. When a Column is required to support a weight, a round cross-section is easy to construct by casting or assembling cylindrical sections, it has minimum surface area for a given strength and has no critical directions for buckling or wind loading. Vitruvius writes that ancient Greeks derived their Doric columns by emulating a smoothed tree trunk with stone. 84.209.89.214 (talk) 14:41, 20 March 2014 (UTC)

Unless 194.66 happens to mean starlings or cutwaters which are sometimes more round than angular, though not circular. ---Sluzzelin talk 16:46, 20 March 2014 (UTC)

Another advantage is that paint will tend to chip off at the corners of a rectangular cross section, and that paint is important in preventing corrosion of metal columns. On the other hand, rectangular cross sections (or I-beams) are often easier to manufacture, say with a continuous process that cuts them into pieces. StuRat (talk) 16:54, 20 March 2014 (UTC)

Yeast and air

I make sourdough bread as well as yeast bread, and want to start making yogurt as well. Do the yeasts used in these processes need air? I have generally covered a bowl containing yeast dough or sourdough with a cloth pr paper towel to allow air exchange, but lots of websites with recipes for bread or yogurt say to cover the container tightly with plastic wrap. Do the yeasts need oxygen, or are they anerobic? Edison (talk) 19:08, 20 March 2014 (UTC)

Of course, we have articles that might be useful: yeast , Bread , and Proofing (baking technique) (each have potentially useful sources). We also have helpful and friendly volunteers here at the Reference desk who will provide even more information (see below, soon?). ~:71.20.250.51 (talk) 19:37, 20 March 2014 (UTC)

According to [12], yeast can grow both ways. For baking and brewing, you want to minimize the oxygen because in anaerobic conditions they will mainly produce CO2 and alcohol. In aerobic conditions, they will multiply more, but won't produce as much CO2, which is what you need for bread. It would be an interesting, and easy, experiment to see whether the covering really makes much of a difference. Yogurt is a slightly different process. Bakers' yeast is in the fungi kingdom; yogurt cultures are bacteria. But it is still anaerobic. Mr.Z-man 22:07, 20 March 2014 (UTC)

I'd also be worried about other nasties growing in an anaerobic environment.

BTW, are you aware that yogurt cultures lose their potency after a few reuses ? Apparently they mix of cultures changes over time, and the new mix isn't as good. StuRat (talk) 05:19, 21 March 2014 (UTC)

Light (wave) Interference. Where does energy goes ?

Hi, I'm starting to study interference in light / waves and a big question came to me. If two waves meet at a point and from there we have a completely destructive interference, what happen with original energy that was transported (contained) by each wave ?

I would apreciate some help to clarify this matter to me.

futurengineer, 20/03

Futurengineer (talk) 19:29, 20 March 2014 (UTC)

It gets bunched up elsewhere. Hcobb (talk) 19:55, 20 March 2014 (UTC)

Useful demonstrations of light wave interference are explained at Newton's rings and (for an exciting post-classical idea that light is not just wave like) Young's Double-slit experiment. Energy carried by a wave is not destroyed at a place where there is destructive interference, it is just not detectable at that particular place. 84.209.89.214 (talk) 20:46, 20 March 2014 (UTC)

It goes to the places where we have constructive interference. --64.134.44.147 (talk) 21:15, 20 March 2014 (UTC)

Think of two waves of water crossing, so the crest of one wave fills in the trough of another. No energy is destroyed. StuRat (talk) 05:26, 21 March 2014 (UTC)

In some places there is no energy, and in other places there is twice the amount of energy. This is sometimes visible to the naked eye as alternate bands of light and dark where the light bands are twice as bright as the illumination prior to interference. Dolphin (t) 05:50, 21 March 2014 (UTC)

Almost. Actually the energy density goes as the square of the amplitude, so in the spots where you have full constructive interference, there's actually four times the energy density. But it all comes out in the wash. --Trovatore (talk) 00:54, 22 March 2014 (UTC)

March 21

Hyperinsulimenia-like conditions

Could someone please reference me to articles who deals with Hyperinsulinemia-like conditions?, for example: a case when a person has a normal level of Insulin but still produces much more energy from glucose\cellular-sugars compared to to Muscle, fat, and other intra-cellular components (also, correct me If I'm wrong, but some amino acids, for example, play a role in such processes).

Sorry for my ignorance. I haven't chose to write this in a simplistic way you know. I just want some reference to know what to read about. I ask here for references because I want to lower the chance that I'm missing anything. Thank you so much guys! 79.179.100.213 (talk) 01:49, 21 March 2014 (UTC)

Wikipedia has an article titled Hyperinsulinemia and also has links from there to external references. That may give you a start. --Jayron32 02:30, 21 March 2014 (UTC)

Our article is surprisingly okay. Here is another article: [13] Note, from linked site: "Information provided on this site is for informational purposes only; it is not intended as a substitute for advice from your own medical team. The information on this site is not to be used for diagnosing or treating any health concerns you may have - please contact your physician or health care professional for all your medical needs."  —71.20.250.51 (talk) 02:52, 21 March 2014 (UTC)

Oh, I mean to Wiki-articles that deals with Pathologies\syndromes which are not Hyperinsulinemia, but also relates to too high utilization of sugars, instead of Muscle\Fat\other sources. these are the references I look for (I have already read in the article Hyperinsulinemia itself and only looking for names of the described conditions). thanks again! 109.64.137.68 (talk) 03:08, 21 March 2014 (UTC)

You might try Symptom Checker from WebMD, then check for articles based on results (if that's what you have in mind).  —71.20.250.51 (talk) 03:15, 21 March 2014 (UTC)

What is the difference between the terms allergy & anaphylaxis?

149.78.22.156 (talk) 07:54, 21 March 2014 (UTC)

Have you looked at allergy and anaphylaxis? Richard Avery (talk) 08:41, 21 March 2014 (UTC)

Yes, I have. But so far I've not got the real difference.149.78.22.156 (talk) 08:53, 21 March 2014 (UTC)

Anaphylaxis is only one type of allergic reaction. All anaphylactic reactions are allergic, but not all allergic reactions are anaphylactic. Allergy is a more or less non-medical term for a hypersensitivity reaction. Hypersensitivity reactions all involve the immune system, but sometimes when a person uses the non-medical term "allergy" they mean something else, which is why it's best avoided in a medical context. Hypersensitivity reactions can be divided into four types, called type I, II, III, and IV. Anaphylaxis is a type I hypersensitivity reaction, mediated by IgE. Type II hypersensitivity or cytotoxic hypersensitivity is mediated by IgM or IgG and complement, and various immune cells. Type III hypersensitivity is caused by deposition of immune complexes. And finally, Type IV hypersensitivity is cell-mediated. - Nunh-huh 09:30, 21 March 2014 (UTC)

The symptoms of an allergic reaction can range from something that is is just an annoyance, such as itching or sneezing, to more severe symptoms, such as swelling, difficulty with breathing etc. Anaphylaxis is the most severe form of allergic reaction which can often lead to death fairly rapidly if not treated. Richerman (talk) 22:37, 21 March 2014 (UTC)

Cuteness

Do humans generally have a tendency to select mates that look cute so that childlike faces on grownups seem to be very abundant in the human populations? 140.254.227.92 (talk) 19:45, 21 March 2014 (UTC)

I doubt it. We're wired to like round faces and big eyes in babies - but "like" isn't the same thing as "tendency to select as a mate". This love of cute is more likely to engender protective instincts than mating desire. We are evolved creatures - our brains have come to be the way they are because that's the way evolution drove us. So we are hard-wired to want to protect babies (which means we also tend to want pets with round heads and big eyes) - but we're also hard-wired such that men want women with child-bearing abilities (hence the obsession with big boobs and larger hips) and women want men with physical strength and endurance for hunting (or whatever) - hence broader shoulders, etc. It follows that what we're hard-wired to prefer depends on the situation. It cuts both ways - if we really did prefer mates with big eyes and round heads, then by now, we'd have evolved to look like a cross between Charley Brown and a Bush Baby! Since that would (presumably) be a bad thing for survival in other ways, instead our brains evolve to prefer the mates who are most likely to be able to help us reproduce. SteveBaker (talk) 20:00, 21 March 2014 (UTC)

Not endorsing this, just throwing it out there. It claims things. Relevant things. InedibleHulk (talk) 20:07, March 21, 2014 (UTC)

The article on neoteny 140.254 piped to does mention some specific traits that have been discussed and theorized over, though some is quite controversial and the section on neoteny and evolution closes with: "On the balance, an all or nothing approach could be regarded as pointless, with a combination of heterochronic processes being more likely and more reasonable (Vrba, 1996)". I guess we could search for more studies on certain traits or possibly meta-studies, but I don't think we can answer your question definitely and generally. ---Sluzzelin talk 20:10, 21 March 2014 (UTC)

So, that means "That guy/girl looks cute," has no connotation in courtship, right? 140.254.227.92 (talk) 20:14, 21 March 2014 (UTC)

I don't see at all how that follows. Your question was on humans' general tendency of selecting mates, not on attributes used when discussing potential mates with close friends in the English speaking world. And of course it can mean many things. A 25-year old man can be cute without having a baby-face. You linked to neoteny (not to cuteness), so I assumed your question was about neoteny, not some ambiguous shifting concept of cuteness. ---Sluzzelin talk 20:23, 21 March 2014 (UTC)

To my ears, this is "cute", and this is "mating cute". InedibleHulk (talk) 20:28, March 21, 2014 (UTC)

Look, this is the nature-nurture problem all over again. When we say that something is evolutionary or that it is genetic or something like that, some people want to say that it falls outside of the realm of free-will or outside of the influence of context and environment. Human behavior is a hopelessly complex melange of environmental influence, genetic influence, social context, and personal choice, and to say "Well, that settles it. We only are attracted to people with X traits because that's what our genes/evolution/whatever forces us to be attracted to" fails to be a workable theory because it doesn't explain the fullness of the human sexual response and human mating behavior with any reliability. A good theory should adequately explain phenomena. The theory that "you are only what you have evolved to do, and thus you must behave X" but fails to account for all of the people with behaviors Y, Z, and P and C as well, isn't a useful theory at all. "Why do people choose the mates they do" has components that are genetic, socially constructed, environmental, and probably some bit of chaos/randomness as well. --Jayron32 21:14, 21 March 2014 (UTC)

Blaming genetics for everything we do, particularly things we do wrong, is kind of the high-tech equivalent of "the devil made me do it" - hence letting them off the hook for any blame (or so they think). ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:08, 22 March 2014 (UTC)

If humans are indeed become neotenous relative even to Neanderthals, which is quite a short span of time in evolutionary terms, it does seem possible that there is selective pressure favoring it. One well known hypothesis might be that neoteny has some advantage in developing intelligence, but sexual selection supplies another potential explanation. Differentiating between the two can't be easy, and I don't see anything in PubMed about "neoteny" "sexual selection" in a quick search. Even in the grossest cases in our own time, it is hard to be sure that the driving force (as opposed to the outcome) is really genetic - the explanation for pedophilia seems elusive, and certainly there is no genetic screen for it. I can readily imagine (but there is no evidence for this example!) that a virus infecting the nervous system such as from the herpes family could interfere with age updating of the optimal sexual target, thereby inducing anything from pedophilia to a mild preference for neotenous characteristics in those affected - in this way the virus, should it persist for a few tens of thousands of years in the human population, might markedly change its appearance, despite the lack of any evolutionary benefit at all! Wnt (talk) 22:27, 21 March 2014 (UTC)

It does seem like in the US, at least, the "ideal woman" has lots of neotenous characteristics:

1) Lack of facial and body hair.

2) Lack of body odor.

3) Slight build.

4) No wrinkles.

5) No gray hair.

6) No menstruation.

7) Big eyes with (relatively) long eyelashes.

8) Red lips.

9) Rosy cheeks.

Of course, some will disagree with this list, and there are also a few adult features which remain popular in women, like big breasts and butts. StuRat (talk) 00:58, 22 March 2014 (UTC)

With the possible exception of item 3, you're describing a Barbie Doll. Maybe cute to look at, but I wonder what sane man would actually want to marry a Barbie Doll. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:10, 22 March 2014 (UTC)

Judging from the models in ads going for sex appeal, I'd say quite a few. StuRat (talk) 14:57, 22 March 2014 (UTC)

What makes you think those ads are directed at men? ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:20, 22 March 2014 (UTC)

If Standards and Practices were easier on advertising, you'd see a fundamental difference. A real-life Barbie is a monkey's paw wish. Or this. InedibleHulk (talk) 17:50, March 22, 2014 (UTC)

• You are conflating signs of fertility common to both males and females, such as full flushed lips, lack of wrinkles and grey hair; signs of femininity; and signs of immaturity, such as relatively larger heads and extremities, which are not themselves signs of femininity. There is some confusion because, except for secondary sex characteristics like wider hips and prominent breasts, females tend to be more similar to paedomorphic humans than do mature males with broad shoulders, prominent chins, etc. There are at least three issues here, age, fertility and sex. Young boys don't need to look like young girls to be cute, any more than chicks and baby bunnies need to look like playboy bunnies to be cute. μηδείς (talk) 03:35, 22 March 2014 (UTC)

• There's a difference that men remain fertile longer, and also tend to be richer and more powerful, say, in their 50's than 20's. So, age markers like a bit of grey hair can actually be attractive in men, hence products like Touch of Grey hair dye for men. StuRat (talk) 15:02, 22 March 2014 (UTC)

I think that trying to infer beauty standards from ads is a common and harmful mistake. Advertisers need to sell products. So they need to push a model of women shaving hair from all sorts of places that look nicer with it, just as barbers used to lobby so heavily to keep men under their thumb on a practically daily basis even though they look nicer hairy. (And while it doesn't have to do with paedomorphic form, the pressure on women to paint their eyes is a veritable crime against humanity, when you consider their natural beautiful expressiveness) I bet that what people want is very much different from the ads. Wnt (talk) 23:43, 22 March 2014 (UTC)

While advertisers may be pushing that image, they have largely succeeded in setting the standard. The number of men who prefer fat, hairy, smelly, menstruating, gray-haired, gray-skinned, thin-lipped, wrinkly, short eyelash, women with no breasts or butts is vanishingly small. StuRat (talk) 03:28, 23 March 2014 (UTC)

March 22

Capsaicin half-life?

Thanks. Regards. 95.35.51.89 (talk) 00:21, 22 March 2014 (UTC)

Approximately 24 hours, elimination half-life is 1.64 hours. [14] --Canley (talk) 00:31, 22 March 2014 (UTC)

If you're asking about the burning feeling it causes humans, that might be a bit more difficult to figure out, as we also become accustomed to it over time. StuRat (talk) 00:45, 22 March 2014 (UTC)

Referencing to the first answer: What is the difference between the 24 period to the 1.64 period of biological half-life? 109.64.137.68 (talk) 04:04, 22 March 2014 (UTC)

They are actually both elimination half lives. The 24 hour figure is the half life of capsaicin on human skin, whereas the 1.64 hour figure is the half life of capsaicin in human blood plasma. Neither is the half life of say, capsaicin in a pepper, or a bottle of hot sauce, or prepared food. Someguy1221 (talk) 04:15, 22 March 2014 (UTC)

Is it true that all human embryos are initially female?

Someone told me that all human embryos start out with just the X chromosome, and then develop for a period of time, and then hormones and another Y chromosome are added at a later stage of development to make it male. Is this true? ScienceApe (talk) 00:48, 22 March 2014 (UTC)

No. You start out with your full set of chromosomes right from conception. However, it is true that the embryo looks female at the beginning, as the penis doesn't develop until later, and the testicles don't descend until much later, sometimes even after birth. StuRat (talk) 01:01, 22 March 2014 (UTC)

I got carried away with details below, but I should say first: the human egg starts out with an X chromosome, and indeed, it is undeniably female, being part of the female body and being the female gamete. But the sperm carries either X or Y, which quite rapidly fuse during fertilization.

See, oh, Sex determination and differentiation (human), Sexual differentiation, genital ridge, Mullerian ducts, Wolffian ducts. Embryos are sort of female, but then again ... so are men. The only meaningful way to define male and female is by the essence of the embryo, i.e. its future programmed sexual development. That said, the chromosomal type isn't always XX or XY, nor a perfect prediction (see Turner syndrome, testicular feminization, freemartin, SRY. So in order to truly determine the sex of an embryo with perfect reliability... you have to watch it grow up. And even then maybe it's transsexual and it and you still can't make up your mind. :) Bottom line: the sex of an embryo is an abstraction, an imperfect model. You have to simply cite the evidence you have, such as the karyotype or other genetic test, and more than 99% of the time that will be perfectly convincing. Wnt (talk) 01:20, 22 March 2014 (UTC)

Below? In the skyhook thread? Gametes don't have sex, only zygotes do. Otherwise you are of the absurd opinion that all sperm are male, which is obviously false. μηδείς (talk) 03:26, 22 March 2014 (UTC)

Hmmmm... now that's an amusing philosophical question. Clearly sperm can be "female" in that they carry an X chromosome and have a wild aspiration to give rise to baby girls. But even more clearly they are male because they are part of a man's body - I mean, if sperm isn't male, what is? Biology really doesn't have a lot of respect for semantics. :) Wnt (talk) 11:08, 22 March 2014 (UTC)

To say that eggs are female because females produce eggs is like saying cakes are bakers because bakers make cakes. It just doesn't follow. μηδείς (talk) 18:04, 22 March 2014 (UTC)

The SRY gene on the Y-chromosome makes a mammalian embryo develop as a male; without it the embryo will develop as a female. However, before the SRY gene is expressed, there is no difference between a genetically male or female embryo. CS Miller (talk) 11:59, 22 March 2014 (UTC)

To be picky, SRY is a lot, but it's not absolutely everything. XX male syndrome isn't the same as being XY - so far as I know, they're always infertile due to the lack of some important details (especially for sperm-making) on other parts of the Y chromosome. Even in young embryos there may be important unknown differences, and there are technically distinctive known differences such as the X-inactivation in females (though come to think of it, Klinefelter syndrome males also have that...) and well, the presence of the Y chromosome itself. But yes, in the visible aspects known the early genital ridge looks undifferentiated due to lack of SRY expression as you say. Wnt (talk) 13:05, 22 March 2014 (UTC)

Moon winch

How about installing a winch on the moon and hoisting stuff up into space that way? Is that any less feasible than a space elevator? --78.148.110.69 (talk) 02:39, 22 March 2014 (UTC)

If you've got 400,000 kilometers of cable lying around, then go for it. --Jayron32 02:45, 22 March 2014 (UTC)

(edit conflict)One big problem I see is that the Moon isn't in geosynchronous orbit. So the hook at the end of the cable would be moving along the face of the Earth at thousands of miles per hour. Dismas|^(talk) 02:46, 22 March 2014 (UTC)

While you've got a strong point in general, is that calculation really correct? What is the actual "ground speed" of the moon relative to the earth? It takes about 12 hours for it to get from one horizon to the other, so I would think its ground speed would be in the neighborhood of 1,000 miles per hour. Not exactly slow, but maybe could be used as a space-age equivalent of the old railroad system of a train grabbing a mailbag on the fly. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:59, 22 March 2014 (UTC)

(edit conflict)It's considerably less feasible. A space elevator has two big advantages over a moon winch: 1) the cable doesn't need to be as long, and 2) the base of the elevator isn't moving relative to the Earth's surface. --Carnildo (talk) 02:47, 22 March 2014 (UTC)

And the reason why long cables don't work is that the weight of the cable is vastly more than the cargo, to the point where the cable can't even support it's own weight and breaks. Even with a long kite string the weight of the string starts to have a drag on the kite, and this is like a million times longer. The space elevator cable may one day be possible, but not the much longer cable to the Moon. StuRat (talk) 14:50, 22 March 2014 (UTC)

Hmmmmmm.... it's possible to make a sort of "cable" by, say, having a steel ball bounce between two steel plates in vacuum, or more realistically, having a rail gun that shoots objects out, which are caught, decelerated to store free energy, and reaccelerated back with that energy by another rail gun at the far end. Such a cable can't mediate an attractive force by any means I know of, but it certainly can induce repulsion. I can kind of picture the Moon being used to "levitate" an object on the far side of Earth by such a stream of exchanged bullets with inspired trajectories, with (hypothetically) relatively low input of fresh energy once it is established. Now if only I had Wile E. Coyote to manage the project! Wnt (talk) 15:04, 22 March 2014 (UTC)

But then it technically won't be a "moon winch", but a "moon gun" or "moon catapult". 24.5.122.13 (talk) 19:50, 22 March 2014 (UTC)

Also, it won't be capable of actually hoisting stuff into space from Earth's surface -- the most it will be able to do is shuttle stuff between low Earth orbit and the Moon. 24.5.122.13 (talk) 19:53, 22 March 2014 (UTC)

True. I think... unless there's some even more lunatic scheme I can devise. :) I suppose that you can boost yourself in something like a sounding rocket or space tourism vehicle to the mesosphere, and then the Captain orders (drumroll) ... "Engage the meteor drive!" The lumps of lunar rock, worked into ceramic heat shields with some robust electronics to control steering fins, pass through the atmosphere almost horizontally, steering to the tiny ship's position and slamming into its momentum receptacle! With blast after blast at incredible speed, the ship gains the crucial momentum to put it into orbit. Except, that is, alas, that it takes quite a bit of energy to redirect a rock from lunar to Earth-grazing orbit, and the energy in this model doesn't plausibly get recycled, so it requires having so much energy on the Moon that it's cheaper than energy taken (with considerable inefficiency) from Earth. Pity. Wnt (talk) 23:29, 22 March 2014 (UTC)

It'll be difficult to devise something even more lunatic than what is already out there – like in one SF novel where a stream of metallic projectiles was catapulted towards the earth, and used for reaction mass to "climb into space" by the reaction force of electromagnetically accelerating them faster downwards. —Quondum 04:47, 23 March 2014 (UTC)

The "moon catapult" concept was explored in some detail in the Robert Heinlein book The Moon Is a Harsh Mistress. It's a form of Mass driver. --Jayron32 04:55, 23 March 2014 (UTC)

The Moon's orbit isn't perfectly circular, so the distance between the Earth and Moon isn't constant. I suppose, if all the other problems were magically fixed, this could actually be an advantage, as you could snag cargo at the low point and release it at the high point, some 42 thousand km up. StuRat (talk) 15:20, 22 March 2014 (UTC)

Abiogenesis mark 1

A few weeks ago I read an article about traces of multi-celled “organisms” which had been discovered around 2004. The article (from a nonscientific, but otherwise reliable source) implied that these “blobs” were the only “survivors” from abiogenesis mark 1 and significantly older than any of the primitive life forms discovered in Australia and elsewhere.
It seems, that these “blobs” became extinct and life disappeared from our planet for a few hundred million years (?) until abiogenesis mark 2 kicked in some 3.5 billion years ago.
I remember looking up the term used in the en:WP and found no article. Does anybody know what I might be talking about? Unfortunately, I recorded no bookmark, can´t remember more details and Googling gets me nowhere.
Thank you.--Cookatoo.ergo.ZooM (talk) 06:34, 22 March 2014 (UTC)

I assume you've checked out our abiogenesis article — there's plenty of blob-like stuff there. Your description almost sounds like Thermotoga maritima, except they're not extinct. ~:71.20.250.51 (talk) 06:49, 22 March 2014 (UTC)

It's been suggested that life may have arisen during the Hadean era prior to the giant impact hypothesis that created the moon. Such an impact would have wiped out all evidence of prior life, so there is no way to prove it. Someguy1221 (talk) 07:17, 22 March 2014 (UTC)

OP here: I managed to locate the report (in German). The blobs are called Gabonionta (discovered in Gabon). They are about 2.1 bio years old and measure about 35mm). Still, there is no article in the en:WP, indeed, all references I can find are either in German (but a red link in the de:WP) or in French (no article either). Thank you for your help.

--Cookatoo.ergo.ZooM (talk) 08:11, 22 March 2014 (UTC)

PS: Some additional data can be checked here. --Cookatoo.ergo.ZooM (talk) 08:18, 22 March 2014 (UTC)

citric acid Extracellular/Intracellular?

citric acid is a extracellular product or intracellular? --84.108.213.48 (talk) 10:45, 22 March 2014 (UTC)

It's produced in the Krebs cycle, which occurs in the mitochondria -- any guesses as to whether the mitochondria are inside or outside the cell? 24.5.122.13 (talk) 19:48, 22 March 2014 (UTC)

X chromosome inactivation in male mammals

In female mammals, one of her X chromosomes is deactivated at random in each cell. This is because in XY males, the Y chromosome has most (but not all) of the genes missing, and expressing genes from both chromosomes in females, and not in males can cause problems, due the doubled expression. My questions are

1. For the genes that are shared between the X&Y chromosomes, are both sets of genes expressed in males?
2. In females, is the deactivated X chromosome completely deactivated, or is the area conserved on the Y-chromosome still expressed?
3. If both sets of genes are expressed in males, and not in females, does this cause any problems?

CS Miller (talk) 12:14, 22 March 2014 (UTC)

The article you linked and pseudoautosomal region both talk about it a little. By and large, any statement in biology is at least a bit true and at least a bit false, and this is no exception. Gene by gene there are known exceptions to both X-inactivation and to the lack of inactivation on the pseudoautosomal region. When you start looking at it closely, there are structural boundaries [15] but these boundaries are not that simple and not that easy to study. By and large, I think it's fairly reasonable to say that "there is no X-inactivation in males" and "the pseudoautosomal region is spared from X-inactivation". Wnt (talk) 14:31, 22 March 2014 (UTC)

Claudius Ptolemaeus on the year

What did Ptolemy believe to be the origin of the year: different amounts of sunlight in different seasons, or Persephone, or something else? Nyttend (talk) 15:22, 22 March 2014 (UTC)

It seems to me that the different amount of sunlight in the different seasons is absolutely obvious, as is the fact that sunlight warms the Earth. Both can be determined by direct observation. Now why the Earth gets more sunlight at times than others is a bit trickier, being mostly due to the Earth's tilt with a minor component due to the Earth's elliptical orbit. StuRat (talk) 16:03, 22 March 2014 (UTC)

Ancient astronomers, including Ptolemy, were well aware that a year was the time taken by the sun to complete one circuit of the ecliptic and that the tilt of the ecliptic with respect to the celestial equator was responsible for the varying amounts of daylight at different times of year. It never ceases to amaze me that modern folk assume that the ancients were oblivious to easily observable phenomena. Ptolemy may have been mistaken about which body was stationary with respect to the other, but he was no fool. Deor (talk) 18:06, 22 March 2014 (UTC)

The problem is that I wasn't paying attention when I wrote the question, and shouldn't have included the different amounts of sunlight. I meant to ask about the astronomical background: why is a year related to the changing amounts of sunlight? Why does the sun go through the ecliptic once per year? I'm looking for a theoretical basis for the observations, analogous to the theory of epicycles necessary to explain the retrograde motion of some of the planets. Nyttend (talk) 03:01, 23 March 2014 (UTC)

Bowel cleaning

How does a human organism clean the bowels from feces' internal traces and residue after defecation?--93.174.25.12 (talk) 16:20, 22 March 2014 (UTC)

It doesn't, feces is produced by the body, it's not purely a waste product. It contains bacteria that help the body digest foods and keep harmful bacteria away. Some people who have certain types of intestinal infections can be cured by putting feces of healthy people in their bowels. Count Iblis (talk) 16:35, 22 March 2014 (UTC)

Note that for certain medical procedures, like a colonoscopy, it is important to clean the bowels. In that case, a clear fluid is ingested which also causes defecation to occur, and the patient refrains from consuming anything but clear fluids for a day or so. This largely cleans the bowels. StuRat (talk) 17:44, 22 March 2014 (UTC)

The fluid in this case is Polyethylene glycol and the procedure is called Whole bowel irrigation. The procedure is done solely so that the physician performing the colonoscopy can see everything clearly; i.e. there's no feces obscuring the view of the colon. Otherwise, for a healthy person, there's usually no reason to "clean" ones bowel after defecation. External cleaning is done often with toilet paper and/or a bidet. But there's no need to clean one's insides out after defecation. There's a bit of quackery that is sold to the uneducated public as Colon cleansing or sometimes "colonic irrigation", which is mostly hoakum, so don't believe what you hear from people trying to sell you on such stuff. But no, you don't have to clean feces out of your colon after defecation. --Jayron32 23:39, 22 March 2014 (UTC)

I doubt Jayron means to be offering a medical opinion, but I would suggest looking at articles like constipation, diverticulosis, and irritable bowel and so forth before assuming all such issues are bunkum. I do agree healthy people shouldn't be going to non-medical clinics for what sounds like medical treatment, and that people who think they are sick should phone their doctor. μηδείς (talk) 01:28, 23 March 2014 (UTC)

What is the SI definition of 1 litre?

litre says " 1 cubic decimetre (dm³), 1,000 cubic centimetres (cm³) or 1/1,000 cubic metre ", which are of course all the same. But what is the SI definition. My guess is 1/1,000 cubic metre, but I haven't found a definitive statement. -- SGBailey (talk) 16:55, 22 March 2014 (UTC)

Our article on the International System of Units don't mention the litre, and the article on SI derived units states that "Some other units such as the hour, litre, tonne, and electron volt are not SI units, but are widely used in conjunction with SI units." So the straight up answer is that there is no SI definition of 1 litre, but a litre is defined in relationship to an SI unit - something which is also explained in the second paragraph in the article on the [litre]]. WegianWarrior (talk) 17:06, 22 March 2014 (UTC)

See also Volume#Units. The nontrivial thing here is the SI definition of the metre, which is defined in terms of the second (by defining the speed of light). The second is by definition the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. This ultimately how the SI unit of length and derived quantities like the litre is defined in terms of physical quantities. Count Iblis (talk) 17:08, 22 March 2014 (UTC)

The Official brochure for the International System of Units, on page 141 of the English version, states that the 12th General Conference on Weights and Measures (CGPM) abrogated the former definition of the litre, the volume of 1 kg of water under specified conditions, and "declare[d] that the word 'litre' may be employed as a special name for the cubic decimetre". The CGPM has jurisdiction over all metric units, including those that are part of SI, and those, like the litre, that are not. Jc3s5h (talk) 17:28, 22 March 2014 (UTC)

I think we've progressed far enough to where we can say "the amount needed to fill a one-litre bottle to the point such bottles are typically filled". That's what I'm going with, anyway. InedibleHulk (talk) 17:37, March 22, 2014 (UTC)

I think Jcs has given the answer I was seeking: 1L = 1 cubic dm. Thanks -- SGBailey (talk) 23:24, 22 March 2014 (UTC)

Or in proper SI notation: 1 L = 1 dm³ (put a space after the number and don't mix words and symbols). ("1 l" instead of "1 L" is also correct, but harder to read.) See the "official brochure" already cited above; specifically, sections 5.1, 5.2, and 5.3.3. --50.100.193.30 (talk) 04:06, 23 March 2014 (UTC)

Do any kind of vitamin/mineral/nutrient overdoses cause tics/muscle spasms ?

If so, at what level ? And the same Q for deficiencies. StuRat (talk) 18:03, 22 March 2014 (UTC)

Eating too much Hypericum perforatum will lead to Serotonin syndrome. Count Iblis (talk) 18:44, 22 March 2014 (UTC)

"...supplementing too much of the wrong nutritional remedies ... have a lowering effect on calcium levels ..." [Calcium related to Muscle Spasms or Cramps] — [16] See also: Electrolyte ~:71.20.250.51 (talk) 19:28, 22 March 2014 (UTC)

Another gravity "related" question

When Sandra is spinning in space: would she eventually get used to it. And observe the universe as spinning around her, the way we observe the sun "go around" the earth. — Preceding unsigned comment added by 2601:C:3600:4AC:4DAA:466F:9A53:2D46 (talk) 19:34, 22 March 2014 (UTC)

Well, she'd feel the blood rushing to the far points, such as her arms if spinning about her spine, or her head and feet if spinning about her hips. If rotating slowly enough, this might not be noticeable. StuRat (talk) 19:46, 22 March 2014 (UTC)

The Semicircular canals would still detect rotational movement due to centrifugal force acting on the fluid in them, so she would always be aware that she was spinning. However, it is hard to know how your brain would interpret which was moving - you or the rest of the universe. And of course, the answer to that really depends on your frame of reference.Richerman (talk) 19:55, 22 March 2014 (UTC)

Yes, but the semicircular canal article also tells us Sandra would "eventually" become habituated to the feeling. I guess from the context that the habituation only takes a few seconds. If so, then I expect she would then see the stars as spinning round although she would obviously know this was wrong. As for the physics rather than the physiology, I found the article Mach's principle not so easy to grasp and Absolute rotation gives a gentler ride. Thincat (talk) 20:46, 22 March 2014 (UTC)

Re: habituation:  There is a (somewhat tangential) experiment regarding Perceptual adaptation — Uhmm... This might be a better link:[17].  —:71.20.250.51 (talk) 21:55, 22 March 2014 (UTC)

As with many optical illusions such as "old woman, young woman" here it's possible the brain would constantly flip from one model to another so sometimes she would feel she was turning and other times she would feel the stars were moving. Richerman (talk) 22:16, 22 March 2014 (UTC)

Does the Friedmann–Lemaître–Robertson–Walker metric figure into anything here? InedibleHulk (talk) 23:18, March 22, 2014 (UTC)

March 23

The Universe

1. The universe had a beginning as a tiny point which expanded in the Big Bang. This would seem to suggest to me that there the universe has a size, and therefor an edge. But the Universe article states that the "size of the Universe is unknown; it may be infinite." How could it have expanded from a dot the size of an atom to infinite?
2. If there is an edge to the universe, what would happen if you were in a spaceship traveling toward it?

46.7.249.24 (talk) 00:05, 23 March 2014 (UTC)

If it is infinite, then it would have always been infinite, that dot would have been the bit that expanded to the visible universe we now know. If you were in a space ship then the universe would include you and the spaceship too, so you would not be past the edge. To be beyond the edge, there should be no light or radiation of any form, so no cosmic microwave background, or any cosmic rays or gravitational waves. You would not be able to detect gravity from the part beyond the horizon. Graeme Bartlett (talk) 00:55, 23 March 2014 (UTC)

• No, the universe has no edge, just like you don't fall off the edge of the finite surface of the earth, just in higher dimensions. The Big Bang is posited to have begun with a singularity, not at a point. Our article shouldn't be making silly claims like that the universe may be infinite. That would mean no matter how big it actually is, it's actually bigger. μηδείς (talk) 00:57, 23 March 2014 (UTC)

Our reference desk editors shouldn't be making claims like that the universe definitely can not be infinite. 88.112.50.121 (talk) 01:38, 23 March 2014 (UTC)

And here I thought there were an infinite number of IP 54 troll addresses available? Perhaps You've not heard of Einstein? The Possibility of a “Finite” and Yet “Unbounded” Universe μηδείς (talk) 03:11, 23 March 2014 (UTC)

Maybe this is where the Friedmann–Lemaître–Robertson–Walker metric comes in. InedibleHulk (talk) 01:04, March 23, 2014 (UTC)

Even if we ignore the metric expansion of space, you still could never get to the edge of the universe, as it's expanding at the speed of light, and you'd have to go faster than that to catch up, which is impossible. However, with the model of multiple big bangs each spawning their own "universe", it's possible another universe's edge could move past us. Depending on the age of that universe, the edge might be very dilute, so we might not even notice it passing. StuRat (talk) 03:14, 23 March 2014 (UTC)

Erm, this seems to contain or risk inducing misconceptions. There is no "universe's edge", however you look at it, only what is called a cosmological horizon, which is another concept entirely. Unfortunately, "universe" is sometimes used to mean "observable universe", which may lead to this misconception. —Quondum 04:26, 23 March 2014 (UTC)

Coherent radar

Various articles use this term in describing particular equipment, but I don't see it defined or its uses or benefits listed. See Journal article about photonics-based coherent radar Jim.henderson (talk) 01:59, 23 March 2014 (UTC)

Wave radar has some information: "Coherent radars measure Doppler-modulation as well as amplitude modulation, while non-coherent radars only measure amplitude modulation. Consequently, a non-coherent radar echo contains less information about the sea surface properties." — A basic understanding of wave phase coherence would be helpful; but a simple analogy would be a laser which utilizes phase-coherent light.  —71.20.250.51 (talk) 04:11, 23 March 2014 (UTC)

You may be interested in the use of the term as it applies to radio demodulation, as it is the same concept. Coherent demodulation allows more detail and information to be extracted from a signal than noncoherent demodulation does, and hence allows transmitted waveforms to be used that require far less power to be used for the same effective received signal. Noncoherent demodulation was used originally, for example, with amplitude modulation receivers, which requires the transmission of a strong carrier for the same demodulated signal quality compared with say double sideband or single sideband that requires coherent demodulation. The advantage of noncoherent demodulation is that the receiver circuitry can be considerably simpler, something that is less of a consideration with modern electronics and techniques. —Quondum 04:18, 23 March 2014 (UTC)

How much greater is gravity on the dark side (away from earth) of the moon than on the light side (facing earth)?

How much greater is gravity on the dark side (away from earth) of the moon than on the light side (facing earth)?68.36.148.100 (talk) 05:06, 23 March 2014 (UTC)