Wikipedia:Reference desk/Archives/Science/2008 October 3

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Science desk
< October 2 << Sep | October | Nov >> October 4 >
Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.


October 3[edit]

Prolonging orgasm[edit]

Is there any safe way of prolonging orgasm in men up to, say 10 mins (I think that would be enough). I know that boars (male pigs) can do it for about 20 mins (even with a dummy sow). Lucky boars!--79.74.251.204 (talk) 00:17, 3 October 2008 (UTC)

Umm, you know that? Really? hydnjo talk 00:45, 3 October 2008 (UTC)
[1]
Do you mean delaying orgasm or making it last longer? Some drugs and herbal supplements are availible which claim to increase both semen volume and number of contractions, however I can't imagine that continuous ejaculation for 10 minutes would be all that enjoyable. After a short while, it would probably become more like dry heaving from the penis, which isn't my idea of a good time. --Jayron32.talk.contribs 03:38, 3 October 2008 (UTC)
That may be the ticket for some folks. -hydnjo talk 04:44, 3 October 2008 (UTC)
Some years ago there was experimentation with electrical or chemical stimulation of so-called "pleasure centers" in the brain [2] [3] [4] [5] of rats and humans. Edison (talk) 05:18, 3 October 2008 (UTC)
Yes: ESO: How You and Your Lover Can Give Each Other Hours of Extended Sexual Orgasm. An interesting footnote is that this book was originally co-authored by Pulitzer Prize-winning author Richard Rhodes, though for some reason he's been dropped from the author list in subsequent revisions. I "hear" that the method works. --Sean 14:06, 3 October 2008 (UTC)
To prolong orgasm, you need to be familiar with the sensation prior to ejaculation. As soon as you feel that you're reaching the peak, you need to stop. Otherwise, there's no turning back. Once you're at the peak, orgasm and ejaculation will proceed with or without further stimulation. Once you're done, you'll need a few minutes to recover. The concept is probably the same with females: just take them near the peak and stop when you're almost there; repeat as necessary. Simoncpu (talk)

Who invented the floor buffer?[edit]

Question as topic. I'd like to add the info to the article I've been working on. I don't seem to be able to find anything useful using Google. --Kurt Shaped Box (talk) 02:27, 3 October 2008 (UTC)

The first reference to an electric floor buffer I found at Newspaper archive was a classified ad in The Hayward Daily Review, (Newspaper) - April 6, 1942, Hayward California, Classifieds, page 2. It was a floor sanding machine from Montgomery Wards which included tampico scrubbing/polishing brushes, a buffing and polishing wheel and a steel wool floor buffer for $32. Google Books has no view but lists patent 1,468,080, from 1876, for a "floor buffer." No idea how it compares to modern ones, but it would clearly not have an electric motor. Once central station electric power was available in the 1880's the application of connecting an electric motor to a pair of counterrotating brushes would be very obvious and the device should have been commercially available by the 1890's to reduce the labor of polishing floors. Edison (talk) 03:44, 3 October 2008 (UTC)
Did we really not have an article on floor buffers until today? That would make a great DYK. Plasticup T/C 15:45, 3 October 2008 (UTC)
What, the article I started - or the fact that WP didn't have an article on floor buffers until yesterday? ;) Yeah, I was surprised to see that was still the case too - I actually mentioned the fact a few months ago (I think when we were discussing floor buffer/MRI interaction). For some reason (don't ask why), I thought about it yesterday. --Kurt Shaped Box (talk) 23:43, 3 October 2008 (UTC)
Thanks - but I'm not quite sure how I'd be able to cite that in the article (if you know better, feel free). Yaknow, I was quite surprised that no-one (apparently) has a website dedicated to floor buffers and the history thereof - considering that lawn mowers and vacuum cleaners seem to have a fair number of fanboys on the net. --Kurt Shaped Box (talk) 23:43, 3 October 2008 (UTC)
US672930 (filed 1901-09-01) is the first one I find for a powered buffer device (appears to rely on external/unspecified rotation power source). It's fixed in place and moves a buffing wheel against a flat surface placed against it (shop machine) rather than being moved against a flat surface (i.e., "the floor"). US871450 (filed 1906-02-24) is the earliest floor buffer, but it's just a block with a a fixed buffer/sander surface (not powered motion). Putting everything together (a electric-motor-powered floor-oriented machine) looks like it starts with US915752 (filed 1906-12-22). Who said Rhode Island was too small to matter or that bowling never led to anything useful? US1468080 was actually filed 1921-03-24...not sure why/where is would be noted as from 1876. DMacks (talk) 14:07, 5 October 2008 (UTC)
So, how would I go about properly citing a patent in an article? I've never done it before... --Kurt Shaped Box (talk) 23:06, 6 October 2008 (UTC)
We have a template for that: {{Cite patent}} Plasticup T/C 23:18, 6 October 2008 (UTC)
Note that for research purposes, Google Patents beats the pants off of esp@cenet and USPTO in terms of both the search and display interfaces. DMacks (talk) 01:55, 7 October 2008 (UTC)

Anatomy / behaviour of bullocks etc[edit]

Okay, so I hope this isn't too stupid a question (or set of questions). Don't feel you have to answer every single question below in order for your reply to be useful, as any helpful pointers would be great.

I've read that bullocks are castrated bulls, and according to the Ramblers Association in the UK they are exempted from the laws which restrict the keeping of bulls in fields crossed by public rights of way -- they write:

"Although there are specific legislative restrictions on the keeping of bulls, these do not apply to cows and bullocks, which can also be very aggressive." [6]

So presumably then they are less aggressive than "normal" bulls. But just how likely is a bullock to be aggressive? About the same as a cow? Or more so?

How common practice is it to castrate bulls, e.g. would a beef farmer typically castrate most of the bulls and just leave a few for mating? At what age would this normally be done, and for sake of comparison what age is puberty?

Also how do you distinguish bulls from bullocks? Does it require a clear view of the area where the testicles should be (from an angle where this is not obscured by hind legs), or are there other obvious differences which are evident e.g. from the overall build of the animal? I am really after simple guidelines so that when encountering one in a field I make a quick and reasonable decision on how likely it is to be aggressive.

Actually another maybe really stupid question. I'd sort of assumed that the centrally located bulge (i.e. about half way between front and rear legs) is where the penis is -- it would certainly make sense as regards the mating position for it to be further "forward" than in a human -- but it also seems that cows sometimes have a bit of a bulge in this area too. So what am I actually looking at in that case? Do I actually need to see the udders to be confident that it's "only" a cow?

Of course there is also the whole issue of breeds of bull, and if anyone has any good pointers on that, then that would be very useful as well. In principle a dairy bull would be more aggressive by all accounts, but it seems to me that there are so many different breeds that you'd have to be something of an expert to know which is which.

Thanks. Are a wiki (talk) 09:17, 3 October 2008 (UTC)

I can't speak to bullocks, but in capons (castrated roosters), the animal is not only less aggressive, but also has more hen-like physical characteristics (more body fat, etc.). --Sean 14:09, 3 October 2008 (UTC)
See also oxen, which are castrated bulls used in situations where docility is required. There are no "breeds of bulls" but see List of breeds of cattle. Rmhermen (talk) 15:17, 3 October 2008 (UTC)
Castrated male cattle are sometimes also called steers. -- 128.104.112.147 (talk) 15:36, 3 October 2008 (UTC)
Nevermind... --Jayron32.talk.contribs 20:41, 3 October 2008 (UTC)

Bullocks are roughly as aggressive as cows, i.e. not very. If walk through a field with bullocks in, they can be curious and start following you. Not really dangerous; just walk on briskly. The situation that would be most likely to lead to a serious accident is if you were at the bottom of a steep bank and one or more stumbled down on top of you. A beef farmer would typically castrate all the male animals and use artificial insemination for breeding. It's only in traditional farming - for example organic - that bulls are still kept outdoors. I've hardly ever seen a bull when out walking in England, but I've seen them often in parts of France. If the bull is with cows in theory it is docile but I wouldn't risk it. If it is in a field on its own, take the long way round. The males are castrated when they are cute little calves. A bull is quite easy to distinguish: it is massively built and has sizable tackle in the middle of its belly. You'll also learn to distinguish dairy and beef cattle. All cows is a dairy herd, in England usually black and white Friesians. All bullocks is beef cattle. Cows with calves could be either. Advice is to avoid walking between a cow and her calf, which is actually not difficult. Happy rambling!Itsmejudith (talk) 17:23, 5 October 2008 (UTC)

Google Image Search gives an anatomy poster here. BrainyBabe (talk) 17:33, 5 October 2008 (UTC)

Generally per Judith except: AI can be problematic and it is expensive, so it's not that uncommon to select a promising AI-inseminated male calf from your best cow, and use it to naturally inseminate the (non-related) rest of your herd. For high-performance dairy cows, you might want to go AI-only, for beef cows, maybe a different approach - you want a cow that gives good milk but not too much (avoid mastitis), and has a good temperament. You will only want one mature bull, otherwise you will end up with fights and just the smell of the other bull will make the one you're in the pen with impossible to control. Remember that bulls and farmers work on a consensus basis - if the bull is happy, everything is good.
I would not personally recommend walking through any field where a bull is present, unless you are closer to the fence than the herd is to you. Remember too that cows are naturally curious and will come closer to check you out - the bull will eventually notice that and exercise his prerogative to walk out in front of all the girls to check out the new centre of attention - and they're not all that smart.
And I've never known a cow separated from her calf to be aggressive, though she might moo enough to get the calf running. Waving your hands is usually enough in any case. OTOH I usually carried a cane walking through our herd, and I was respectful of the Scottish longhorns - but I've never been charged by a cow, nor a steer. Never been charged by a bull either, but as I said, that was a consensus happy-time decision - I always made sure not to upset the bull, what with the 1000-pound weight differential.
As far as the original anatomy question, all cattle have that distinctive shape on the abdomen, but males have extra longish hair at the pendant point (and pee from that spot), and uncastrated males are distinctively more bulky in general and "well-equipped" at that point. If a significantly larger animal of the herd is approaching you, it's best to rapidly retreat. Threats and appeals to reason are unlikely to help the situation. Franamax (talk) 00:19, 7 October 2008 (UTC)
1)But if you decide that discretion is the better part of valour and retreat, what might trigger it to run after you? 2) Why do females have that shape on the abdomen if it isn't a penis? Is it like the hyena? BrainyBabe (talk) 20:41, 7 October 2008 (UTC)

Misshapen head treatment[edit]

What is that treatment called where a baby has a slightly misshapen head and is "corrected" by having the baby wear this head device for several years so that the skull can be shaped to a "normal" form? I read that some native american tribles had done this in reverse decades ago for aesthetic reasons, meaning they deliberately tried to flattened the baby's head....--Anilmanohar (talk) 12:55, 3 October 2008 (UTC)

The Native American tribe you are likely referring to are the Flatheads. Of note, they did not flatten the baby's head. That is folklore. The truth is that a neighboring tribe used head binding to produce pointy heads. So, the normal people were called "flathead." In modern times, a device that it used to change the shape or position of bones (even the skull) is called a brace. There is no specific term for it. It is often termed by the usage, such as dental braces or orthopaedic braces. -- kainaw 13:02, 3 October 2008 (UTC)
The technical term for what you are referring to is plagiocephaly (though this entry is pretty much a stub). There is also an entry called positional plagiocephaly which has a tiny bit more discussion of the etiology and treatment. Medical geneticist (talk) 13:27, 3 October 2008 (UTC)
Craniosynostosis. Plasticup T/C 14:40, 3 October 2008 (UTC)
It is correct that craniosynostosis is one cause of plagiocephaly (which is simply a technical term for "misshapen head"). The distinction is that craniosynostosis usually requires surgical correction because it involves abnormal premature fusion of the skull bones, while positional plagiocephaly is a deformity that can be corrected by putting a fancy helmet on an infant, which gradually reshapes the bones of the skull while they are still pliable. Medical geneticist (talk) 16:10, 3 October 2008 (UTC)
Someone asked a similar question a couple days ago. -- MacAddct1984 (talk &#149; contribs) 14:59, 3 October 2008 (UTC)
You may be thinking of the Inca practise of cranial deformation. I haven't studied the topic myself and our article basically just repeats the essence of the blurb here. IOW, yes they did it, but the reasons why are still somewhat unclear. Matt Deres (talk) 16:32, 3 October 2008 (UTC)

Urinary Tract Infection Cause?[edit]

From the CNN article: http://www.cnn.com/2008/HEALTH/10/03/bathroom.hygiene/index.html

"It's fine for a woman to hover over the toilet seat if she doesn't want to sit down, but if she doesn't empty her bladder completely, she's at risk for a urinary infection, Bernstein said."

Why is this so? --Anilmanohar (talk) 14:01, 3 October 2008 (UTC)

Because urine acts as a culture medium for bacteria; if the bladder is completely emptied, the urine isn't there to be infected. If the bladder is incompletely emptied, it contains urine that can become infected. The risk is greater for women than men (because women have shorter urethras), but incomplete emptying of the bladder in men (often as a result of protate enlargement) also predisposes to infection. An empty bladder is protected from infection by urothelial surface mucoproteins, but urine has no such defense. - Nunh-huh 21:03, 3 October 2008 (UTC)
"urine acts as a culture medium for bacteria" ??!? Whaaaat? That's not right - Urine (as our article points out) is an antibacterial agent. "Urine has also been historically used as an antiseptic. In times of war, when other antiseptics were unavailable, urine, the darker the better, was utilized on open wounds as an antibacterial.". SteveBaker (talk) 12:38, 6 October 2008 (UTC)
My completely unreferenced understanding of this is that urine remaining in the urinary tract is a source for bacterial accumulation. In other words, for males drinking their own pee (don't laugh, it's both a survival and religious tactic), the first few inches of discharge are un-good, the rest is fine. In the context of the question above, I would interpret this factoid as meaning that premature termination of urination would leave urine in the GU tract, where bacterial proliferation could occur. Franamax (talk) 23:33, 6 October 2008 (UTC)
The reason certain bacteria cause urinary tract infections is precisely because they resist the antibacterial properties of urine. If these antibacterial properties were stronger and controlled all strains of microorganisms, we wouldn't get urinary tract infections. But they're not, they don't, and we do. And all urine is not alike. Any antibacterial effect depends primarily on osmolality, urea concentration, ammonium concentration and pH. And of course urease-producing organisms like Proteus mirabilis love urine. - Nunh-huh 12:01, 7 October 2008 (UTC)

Baby Powder scent?[edit]

What's the origin of the "baby powder" scent? What is it supposed to smell like? Why has that scent become associated with all things baby? --70.167.58.6 (talk) 16:54, 3 October 2008 (UTC)

Baby powder (Johnson and Johnson)?--GreenSpigot (talk) 17:28, 3 October 2008 (UTC)
How are these links relevant? --70.167.58.6 (talk) 18:53, 3 October 2008 (UTC)
Most baby powder is made by Johnson and Johnson. So you could ask them--GreenSpigot (talk) 19:52, 3 October 2008 (UTC)
Baby powder is classically made of talcum powder, and I would assume that the particular mineral composition is responsible for the smell. As to why that smell is associated with "all things baby", it probably has to do with the millions of baby bottoms that have had talcum powder applied to them. Medical geneticist (talk) 22:16, 3 October 2008 (UTC)
Poor little buggers. Talcum powder has been the cause of more nappie rashes than babies have had poos. When they wet themselves, the powder turns to a fine grinding agent. Far better to use a little baby oil, and no powder. -- JackofOz (talk) 23:57, 3 October 2008 (UTC)
I don't buy that. Talc is one of the softest substances out there. Check out Mohs scale of mineral hardness - talc is a 1 on Moh's scale - which makes it the least hard substance on the scale. SteveBaker (talk) 12:33, 6 October 2008 (UTC)
I'm sure that's right, Steve. However I was told this when son #2 came along, by senior babycare educator nurses at the hospital, who all agreed that the traditional talcum powder treatment is not only less effective than oil, but causes or at least contributes to nappie rash, so it's actively discouraged these days, certainly in Australia. If the reason for the powder is just make the baby smell nice, that's unnecessary - they smell good naturally. Until the inevitable happens, that is, but talc certainly doesn't mask that smell, and shouldn't be used with purpose in mind. -- JackofOz (talk) 23:57, 6 October 2008 (UTC)
I don't doubt that there are better alternatives to talc. My complaint is only the claim that the stuff is acting as an abrasive - when in fact it's a pretty good lubricant. (Talc is a excellent lubricant for wooden surfaces. If you have a cabinet drawer that's sticking - dust it down with some talc. Our question about sticking piano pedals a couple of weeks ago was answered with "Use talc" for example.) My wife was once a Nurse - and indeed taught nursing for many years (although not in pediatrics). It's clear to me that Nurses become very good at knowing WHAT to do in a vast range of situations - but they don't seem to pass on the knowledge of WHY they do it with any degree of precision. So it would come as no surprise to me to find that talc is bad for some other reason. I could imagine (without evidence) that perhaps talc causes the urine that it absorbs to be retained in contact with the skin where oil (being strongly hydrophobic) repels it. As urine evaporates, the urea concentration rises - and concentrated urine is a skin irritant. But it's really not reasonable for a material that's renowned PARTICULARLY for it's softness to suddenly become an abrasive like that. SteveBaker (talk) 03:08, 9 October 2008 (UTC)
Well they make unscented baby powder, so natural talc doesn't have a smell. It's an added fragrance. --70.167.58.6 (talk) 15:29, 4 October 2008 (UTC)
It doesn't necessarily follow that natural talc doesn't have a smell, just because a version which hasn't had scent added exists. I tend to think of the natural smell of talc as 'chalky', where smell should probably be clarified as the sensation when some of it gets in your nose after a cloud of the stuff has been puffed around you. Whether this is the same smell as you were asking about, I don't know. Maybe you're asking about the smell of the typical added fragrance? 79.66.9.134 (talk) 18:21, 4 October 2008 (UTC)
The talc powder that you scratch off a rock definitely don't have that baby powder smell... --antilivedT | C | G 21:56, 4 October 2008 (UTC)
The fragrance is added. Check the ingredients. --Russoc4 (talk) 23:58, 4 October 2008 (UTC)
So back to the original question: what is it supposed to smell like? Is there anything in the world that smells like Baby Powder? --70.167.58.6 (talk) 15:39, 5 October 2008 (UTC)
It seems that Johnson & Johnson created a scent for their talcum powder that they thought help market it to parents, who would have been used to fragrances added to soaps, shampoos, cleaning products etc. Now people associate this scent with babyhood and the company is unlikely to change it. Isn't it the same scent in their baby oil? Itsmejudith (talk) 16:17, 5 October 2008 (UTC)
The J&J babypowder is indeed a perfume, in fact the marketing of this product has been so successful that its perfume scent accord is associated with a baby-hood. As such, any other company in North America producing baby products have to scent their products with similar accords or risk being shut-out. I've heard that associations of baby products with the J&J scent is limited mainly to North America; European baby products are scented primarily with lavender. Demeter fragrance has a pretty similar baby powder perfume. Sjschen (talk) 21:54, 5 October 2008 (UTC)

You don't get out much, do you? When was the last time you had a girlfriend or a female of some sort? Are you gonna write more paragraphs now?--Anilmanohar (talk) 13:21, 7 October 2008 (UTC)

What? Zain Ebrahim (talk) 13:38, 7 October 2008 (UTC)

magnetism[edit]

hi .... i have a question that why a magnet only attracts a magnet??? ... why not any other thing??? —Preceding unsigned comment added by 116.71.246.18 (talk) 18:13, 3 October 2008 (UTC)

On a macro scale, magnets do attract things that aren't magnets; see Paramagnetism. On a micro scale, magnetic fields also affect moving electric charges in addition to magnetic dipoles. As for why the electromagnetic force behaves the way it does, check that article, but I think whether an answer exists probably depends on how deep a "why" you're looking for. --Allen (talk) 18:37, 3 October 2008 (UTC)
Huh? --ColinFine (talk) 19:00, 4 October 2008 (UTC)
This is clearly not true! A magnet attracts all sorts of non-magnetic objects. Admittedly, only a few metals respond to magnetism (you can't pick up a chunk of aluminium with a magnet, for example) - but those that do (iron, for example) can be attracted to a magnet even if they are not, themselves magnetized. To convince yourself of this - get a refrigerator magnet. It sticks to the metal of your refrigerator - right? But remember that magnets only attract each other if the north pole of one magnet is close to the south pole of the other - north-to-north or south-to-south, they repel. If the refrigerator door was magnetized then it would have to be exhibiting (say) a south pole on the surface to attract the north pole of the fridge magnet. If you flip the fridge magnet over so the south pole is now facing the door - then it should be repelled...but it's not - it still sticks. Since the refrigerator door can't be presenting both a north pole and a south pole at the same place - you know that it ISN'T magnetized. SteveBaker (talk) 12:26, 6 October 2008 (UTC)
Umm, Steve, the fridge door is an induced magnet isn't it? It is a ferromagnetic material, when another magnet is brought close the unpaired electron spins align (I could be wrong here - is it the atomic spins?) (ferromagnetic domains are coerced into alignment) and it becomes a magnet. Based on my experience with training screwdrivers to pick up metal stuff (like screws), some residual magnetism could be measured in the fridge door after the encounter. In my book, that makes it a magnet. Franamax (talk) 23:20, 6 October 2008 (UTC)

Mules[edit]

Mules are F1 hybrids between horse and donkey. Both belong to the genus Equidae in the Biological classification.

There is 94% identical DNA between human beings and chimpanzees. What % of identical DNA does horses and donkeys have? If it is equal or more to humans and chimps, why are there no F1 hybrids (or whatever) between humans and chimps? --Anilmanohar (talk) 19:39, 3 October 2008 (UTC)

See Humanzee for the details. As to why there are none even if it was possible, it's because of the ENOURMOUS social taboo against it. No scientist smart enough to do it would even dare attempt it. 83.250.202.36 (talk) 19:57, 3 October 2008 (UTC)
Sure, but no scientist has to be involved to make a mule. --Sean 11:57, 4 October 2008 (UTC)
Yeah, but I don't think it's likely that any human would naturally have sexual intercourse with a chimpanzee due to the same social taboos. --Tango (talk) 16:59, 4 October 2008 (UTC)
Hmm. --Sean 14:26, 6 October 2008 (UTC)
Actually Equidae is a family, though Equus does appear to be its only surviving genus. But while the question is worth asking, do be cautious about that sort of numerological argument: there is no reason to suppose that there is some particular percentage of common DNA which is the threshold for the possibility of viable offspring.

Note also that all surviving equids are classified as the same genus, whereas no surviving apes are in the same genus (homo) as humans. This is not conclusive - levels of taxonomy are not always self-evident - but it is indicative. --ColinFine (talk) 19:14, 4 October 2008 (UTC)

I'm surprised no one has bothered to read my questions and try to answer them. --Anilmanohar (talk) 13:37, 6 October 2008 (UTC)

That's more than a little unfair. I think we all read your question...but it's probably impossible to answer it. Nobody (as far as I could discover) has yet sequenced Donkey DNA. It's likely that racehorses have been sequenced - there is a lot of money in breeding them - but the people involved do not appear to wish to advertise the results. Hence it's almost certain that the first part of your question is unanswerable - so nobody HAS answered it. User:ColinFine did point out that knowing the percentage of DNA in common doesn't necessarily lead to an explanation of why two different kinds of animal can interbreed - which kinda makes your question moot. And several of us did answer the part about Human/Chimp hybrids - both by explaining why nobody has tried to produce such a hybrid (as if it wasn't bloody obvious already!)...and by pointing you to our article on the subject.
But you can't tell by reading the answers whether anyone tried to find an answer or whether we read the question carefully - and it's quite rude (for someone who is asking for a HUGE favor) to just assume that we didn't. In fact, when we try to find an answer and fail - we don't generally bother to discuss that. But it's quite rude to claim that we didn't read your questions. I certainly did, and I'm sure that at least a dozen other regular contributors did too. Yesterday morning, I searched online for about 15 minutes to try to find out whether Donkey/Horse DNA had yet been sequenced and didn't come up with an answer to that piece of your question - I'd planned to search some likely journal indices at the UTA library today or tomorrow - but since you've been so rude, I don't think I'll bother.
SteveBaker (talk) 14:29, 6 October 2008 (UTC)

Steve, the correct response would be: "The % of identical DNA horses and donkeys have is not known. Thus, your second question is unanswerable." Stop taking things so personal. My original response was not a rude one. It was a true one. Thus my original response still stands as is. --Anilmanohar (talk) 18:21, 6 October 2008 (UTC)

Excuse me? You said that "no one has bothered to read my questions" - which is (a) an accusation of laxity on behalf of those of us who contribute time here for no recompense (b) utterly untrue - at the very least I read every single question that shows up here (and I'm pretty sure most of the other regular contributors did too) and (c) this something you could not possibly know. Hence your accusation is utterly inappropriate. You went on to say that nobody had answered your question - when in fact we had gone a considerable way towards doing so. Now you suggest that we should have said that the "% of identical DNA horses and donkeys is not known" - but I for one won't know that until I've researched it a little further - which is why I didn't answer this before. If you note the Reference Desk guidelines (at the very top of this page) you'll see that it specifically states: "Be patient. Your question probably will not be answered right away (...) A complete answer to your question may be developed over a period of up to four days.". For someone who appears to contribute NOTHING to Wikipedia (yes, I looked at your "Contributions" section - all I see there are RefDesk questions) - I think your gratitude and humility levels could use a little adjustment. SteveBaker (talk) 18:43, 6 October 2008 (UTC)

Helpdesk - It is preferred that SteveBaker not respond to any questions today. Please take the necessary steps to remove him. His responses are accusatory and borderline abusive. --Anilmanohar (talk) 18:49, 6 October 2008 (UTC)

This is not the "helpdesk" it is the Science Reference Desk. People who request answers and then make unfounded accusations about how volunteers are reading and responding really don't get to pick who gets to play. Perhaps Yahoo Answers would be more to your liking. --LarryMac | Talk 20:19, 6 October 2008 (UTC)

Being as said, your "volunteers" need a brush up on reading comprehension... FYI - questions I never asked were answered. Not the orginal question..--Anilmanohar (talk) 20:34, 6 October 2008 (UTC)

Now - you really are doing your very best to make everyone love you aren't you? OK - let's see about this alleged "lack of reading comprehension" were now accused of. Please feel free to award my terribly lame reading comprehension with points out of ten - oh great master of the English language:
You said:
  • Mules are F1 hybrids between horse and donkey. - this is a statement, not a question.
  • Both belong to the genus Equidae in the Biological classification. - another statement. (It was pointed out that you are in fact incorrect in stating this - but fortunately, that doesn't affect what follows.)
  • There is 94% identical DNA between human beings and chimpanzees. - another assertion. (Actually - I believe that if you only count active genes, this number is a little low - between a human and a chimpanzee of the same sex - the number is more like 97% - between human and chimpanzee of different sexes, it's way less than 94%. If you count ALL DNA then 94% is way high - even two non-identical-twin sibling humans of the same sex don't share that much total DNA. But again, this doesn't really affect what follows.)
  • What % of identical DNA does horses and donkeys have? - Ah! A question at last. I doubt anyone misunderstood, misread or failed to read this (despite it being a grammatical mess). We simply do not have an answer for you (at least not yet). I have explained why it may not be possible to answer that - and I explained that I intended to look for a better answer - but then you insulted me, so I don't think I'll bother. But at any rate, it's hard to prove a negative, so a good answer might well take longer. It appears likely that the answer is not known.
  • If it is equal or more to humans and chimps, why are there no F1 hybrids (or whatever) between humans and chimps? - Since you predicated this with an "if" and the answer to the "if" is unknown, then we must either treat this as a hypothetical or remain silent. So IF humans and chimps (hypothetically) shared more DNA than horses and donkeys do - then what reason might there be for there being no hybrids? Now - if you read the THREE very germane answers we provided - you'll see that we said:
    1. We have an article about this (Humanzee) that you should read.
    2. Your presumption that the amount of shared DNA is a measure of how likely hybridization is possible is incorrect (obviously, IMHO).
    3. That moral and legal constraints make the formation of human/chimp hybrids exceedingly unlikely - biology notwithstanding.
So - every part of your question was read, understood and (as far as can be) comprehensively answered. If you were hoping for lots of exciting details of unusual sexual practices that would help you in your personal life in some way - you're out of luck.
However, you still persist in demanding answers (like it's some kind of legal right or something) from a volunteer-supported service...you do that DESPITE our FAQ at the top of this page clearly telling you that you should be patient and not to expect a full answer for FOUR days. You do it rudely by proclaiming that we somehow aren't reading your question. Now you conclude that our reading comprehension is flawed. I don't know why you put "volunteers" in quotes - they really are volunteers - not one of us is paid or gets recompense in any other form. None of us are under some kind of external compulsion to answer questions...yep - we are actually volunteers.
Anyway - I can prove that I'm a volunteer. I believe that you are exhibiting unacceptable behavior - and since I'm just a volunteer - I have decided that I will not knowingly answer any more of your questions until you apologize to the volunteers who worked hard to help you out here. If I am not in fact a volunteer, my boss will probably tell me to get back to work and answer your questions...let's see what happens shall we?
SteveBaker (talk) 23:22, 6 October 2008 (UTC)

<Redacted personal attack --Stephan Schulz (talk) 15:28, 7 October 2008 (UTC)> --Anilmanohar (talk) 15:05, 7 October 2008 (UTC)

Nobody "erased your response," although anybody would have been right to do so; you put it in wrong section. Your continued uncivil posts can and most likely will result in at least a temporary block from Wikipedia. --LarryMac | Talk 15:30, 7 October 2008 (UTC)
Indeed - I did not erase anything (as is easily demonstrated by checking the "history" tab). As for obtaining an additional female companion (per Anilmanohar's recommendation) - I suggested this to my wife - but sadly, she was not keen on the idea. SteveBaker (talk) 02:50, 9 October 2008 (UTC)

Hi, after reading the above content, in Anil's defense, it seems that the volunteer did hastily respond back with negative undertones. I understand that Anil has not contributed to Wikipedia, but that shouldn't be an excuse to verbally attack him in this forum. Not to say that English is a second language to him but it is possible, and to send a response that Steve sent is not only discouraging to Anil, but to the rest of the population (like me) who use Wikipedia.org. I have worked as an ESL tutor for quite some time and in many cases, my students have been misjudged or misterpreted for their lack of understanding certain nuances in the English language. That is just my personal opinion.....--Emyn ned (talk) 14:47, 9 October 2008 (UTC)

How exactly would you construct an "unfair" coin?[edit]

When you're learning about probablity theory, there's always discussions of "unfair" coins (i.e. "How many coin-flips do you have to do to find out if a coin is fair" or "What's the probability distribution for a certain unfair coin"). The idea is of course a supposed coin that when you flip it, it comes up with one side more often than the other.

My question is this: is it even physically possible to construct such a coin? Or is this a completely fictional concept? I mean, it's easy constructing an unfair die, if you just weight the "1" side a little heavier than the others, it will more often come up "6". But that wouldn't work on a coin, would it? I mean, if you weighted the "heads" side heavier, it would come up "tails" more often if you just threw the thing up in the air, but that's not what you're doing. When you flip a coin, you spin it in the air. For the tails-side to come up more often, the coin would have to spend more time with the heads-side down while it is flying through the air. That means, if it is spinning, the coin would have to decelerate while the heads side is down, and accelerate when the tails-side is down. But that's not what it's doing, even if it is weighted, it's just spinning the at the same angular velocity all the time. The time it spends with the heads-side up is exactly the same as the time it spends with the tails-side up.

I'm willing to concede that if you let the coin bounce on the floor once, then it could have an effect (as the coin then is just basically flying randomly through the air). But if you cought it in your hand, this wouldn't happen. So, is it possible to construct an unfair coin, and how would you do it (without putting teeny-tiny engines on the thing, that is :)? 83.250.202.36 (talk) 19:52, 3 October 2008 (UTC)

You could cast the coin to have two faces. You could use a coin where one side was notably distinct from the other, perhaps to the point where a keen-eyed "flipper" could know when to grab it in flight. You could have a noticeably different texture on one side, so the flipper knew to either slap the coin onto his other hand "honestly" (reversing it) or attempt to manipulate the coin while it is still unseen so the other side comes up. Matt Deres (talk) 20:03, 3 October 2008 (UTC)
These are all true, but it's not exactly what I'm looking for. I'm thinking of something analougous to an unfair die, where it really looks like a regular coin, but when you flip it, one side comes up more often. So someone could give it to you and say "Find out (with X percent probability) if this is an unfair coin by flipping it as many times as you need" 83.250.202.36 (talk) 20:06, 3 October 2008 (UTC)
Its not hard. You construct the coin so that the one side is made of a denser metal than the other, for example make the tails half lead and the heads half aluminum. Then clad the whole thing in whatever a coin of that type is clad in (for example, if a penny you'd clad the off-balance coin in copper). The result is that, over many flips, the tails side will be favored to land down, being denser... It wouldn't work every time, but even loaded dice don't work everytime... --Jayron32.talk.contribs 20:19, 3 October 2008 (UTC)
The original poster is specifically asking about a coin that is unfair when it is spun and caught while in the air, so all that matters is its position when you grab it while it's rotating at a constant speed. I suppose an uneven weighting or a beveled edge might have some tiny effect by introducing a slight asymmetry in the situation where its position is right on the cusp between coming out heads and tails, but it sure won't be much. Of course you could make a coin with both sides the same and have 100% chance of it coming out the way you expect, but people might notice that!
For coins spun to land on a table, I have heard that with some ordinary coins there can be noticeable "unfairness" due to the image on one side having higher relief than the other. But I don't have a cite for that. --Anonymous, 04:48 UTC, October 4, 2008.

Actually it's even easier. You take a fair coin and hit it with a hammer. It will then be slightly u-shaped and thus be heavier on one side. This also solves the problem of spinning while being in the air. The hollow side will be more unstable in flight thus will end on top. - Dammit (talk) 20:29, 3 October 2008 (UTC)

A coin badly dented with a hammer would have visible damage and be suspect.
It would be easier to take a normal coin and bevel the edges slightly. Normally a coin can stand on its edge. Beveling the edge, even a small amount, would bias the coin to falling over on one side when bouncing or spinning on a hard surface. This wouldn't guarantee the same result every time, but the coin would be biased to one result. ~Amatulić (talk) 20:56, 3 October 2008 (UTC)
Actually, all coins are unfair. 51% of the time—not 50%—a coin will land on the same face it started out on. zafiroblue05 | Talk 22:40, 3 October 2008 (UTC)
If you want to be technical, it isn't the coins that are unfair, it is the "flip". Much of the time, the "flip" doesn't cause the coins to flip at all. They wobble in the air and come down without turning over at all. -- kainaw 23:42, 3 October 2008 (UTC)
I read somewhere that the American penny is an unfair coin. I don't remember which side shows up more often, but it's only like 1 more in every 1000 or so. --M1ss1ontomars2k4 (talk) 21:15, 5 October 2008 (UTC)
You don't need to construct one - get yourself a Belgian 1-Euro coin. There was a significant study into the fairness of the various 1 Euro coins out there (every country got to put it's own design onto their version of the coin) - the differences were pretty dramatic: This New Scientist article says that the Belgian 1 Euro coin (for example) comes up heads 56% of the time! So I would imagine that lots of other coins in common circulation would be unfair too. SteveBaker (talk) 12:13, 6 October 2008 (UTC)

A very tiny effect would be caused by the fact that the density of air decreases with height. The lower edge experiences larger air resistance, having a similar (but of course smaller) effect as the edge hitting the ground. Another small effect of this kind occurs if the coin comes close to a stationary surface: The viscosity of air will decelerate the edge closer to the surface. Icek (talk) 20:50, 8 October 2008 (UTC)

"Simplicity" of scientific/mathematical problems[edit]

It strikes me that something like Fermat's Last Theorem or e=mc^2 is relatively easy to understand, the former (not the solution by the hypothesis) to anyone that's taken middle-school algebra, and the latter to anyone who knows that c is the speed of light. But when I look at something like Millennium Prize Problems, all the problems listed are little more than nonsense to someone without the requisite mathematical knowledge, and physics questions such as string theory or higgs bosons are based on complex mathematics that can't really be explained to the average person without bastardizing them. I'm wondering if there's anything to this - that science and math have advanced beyond the understanding (not just understanding the recognizability, really) of the average person, and why this would be, and also if there are any standing problems in either area that appear as basic as, say, Fermat's last theorem. zafiroblue05 | Talk 20:30, 3 October 2008 (UTC)

Actually, e=mc^2 is so simple that dozens of people observed it before Einstein. It's not really that big of a deal. Einsteins real genius, mathematically speaking, comes from his explanations of General Relativity, vis-a-vis such phenomena as the effect of gravitation on light, and on his calculations tied to quantum theory. The math in those is WELL beyond most laypeople. Quite honestly, most fields are beyond the average person who does not have adequate training. Anyone could probably be taught to handle the math required to "get" advanced physics, its just that most people aren't interested. The inner workings of my car are a complete mystery to me, and that's why I pay someone to take care of it. Other people have expertise where I don't. This is just as true for auto mechanics as for mathematicians... --Jayron32.talk.contribs 20:38, 3 October 2008 (UTC)
That's no excuse for failing to write articles in layman's terms. United States jury trials do similar things all the time. I get depressed when I see a once-decent article such as linear regression, which once contained practical and useful information that a layman with some college math could put to use, turned into a jargon-filled theoretical treatise (at least that article now contains a practical example to clarify things). That isn't encyclopedic, that's merely obfuscation. Experts in the field don't need to go to Wikipedia for this sort of thing, so the articles don't need to be written for experts only. ~Amatulić (talk) 20:51, 3 October 2008 (UTC)
Um, you'll get no arguement from me. I don't think that answers the question from the original OP or even comments on it... It's merely diatribe... If you don't like an article, take care of it. --Jayron32.talk.contribs 20:58, 3 October 2008 (UTC)
I thought I did address the OP's comment, which seemed to comment on the level of expertise needed to understand the meaning of millenium prize problems. As for articles like linear regression that got converted to jargon, I have tried to "take care of it" as you suggest, but after a point I got tired of my attempts being reverted, and moved on. ~Amatulić (talk) 23:40, 3 October 2008 (UTC)
If the article is too technical, perhaps you could dumb down a version for the Simple English Wikipedia? Isn't that what the project is for? Plasticup T/C 01:38, 4 October 2008 (UTC)
No it's not, we are supposed to be building an encyclopedia here not a technical reference book. Equendil Talk 07:28, 4 October 2008 (UTC)
We should be doing both here. Articles should explain the concepts or have links to simplified explanations; and they should lay out the whole difficult field in all its technical glory. Our problem is simply to properly explain. When a user searches for quantum mechanics, do they want an overview, a basic understanding, a confusing in-depth glimpse, or the specific underlying equations? Wikipedia is big enough to do all of these. Franamax (talk) 05:57, 5 October 2008 (UTC)
I agree with what Jayron wrote above, but with a small addendum that, media portrayals of what life, the universe, and everything should be like aside, the real world has no obligation to be either simple and beautiful or complex and murky; it just is. Some parts will be explained neatly, some parts will not. Some parts can be summarized into very basic steps (evolution by natural selection), yet are still wonderfully complicated and nuanced when you try to understand how the theory applies mechanically. How complicated something appears to be can depend greatly on how in-depth you want your knowledge to be and also what aspect you want to understand. Cars seem to have changed a great deal over the last century, but you can still get a great deal of insight in how they work by understanding such basic concepts as the four-stroke engine, the carburetor, and differential gearing - the same concepts you'd have needed 100 years ago. Seen that way, they're still pretty simple, but seen from the POV of the computer systems designed to regulate all that simple stuff they seem horribly complex. Matt Deres (talk) 13:28, 4 October 2008 (UTC)
In answer to the OP's actual question, yes there are still some simple problems left. The twin prime conjecture springs to mind. However, modern mathematics has been being built up for thousands of years so a lot of problems have already been solved. Everything builds on what went before so you generally need a good understanding of what went before in order to understand the new stuff. It's not quite so bad in science since sometimes theories are proved to be complete nonsense and you can just forget about them, but in maths everything that's been proven once is still true now and always will be. Every now and then mathematicians will find a new branch of mathematics or a new approach to an existing branch that hasn't been done before and they get to find out new maths which can actually be understood without knowing lots of existing maths, but it doesn't happen very often. --Tango (talk) 15:55, 4 October 2008 (UTC)
In terms of problems that are very simple to understand, but as of yet unproven, I'd think Goldbach's conjecture would top the list (that is, "every even integer greater than 2 can be written as the sum of two primes"). There are a bunch of other ones, though, like the existance of an odd perfect number or whether there are an infinite number of Fibonacci primes. And if you have a nice person explaining it to you, P vs. NP isn't all that hard to understand, at least not conceptually. 83.250.202.36 (talk) 20:10, 5 October 2008 (UTC)
Yes - P vs. NP is pretty simple. The question is this: If you have some problem to solve and you have some easy way to determine whether the answer you get is correct or not - then is there always an easy way to find that answer in the first place? Are there any problems where finding the answer can be amazingly difficult - but checking it is amazingly easy? Suppose, for example, that you have a list of a million random numbers, each between 1 and 1,000,000 - and someone asks you whether there is an '84' anywhere in the list. If I asked you to find that out, you might have to look through all million numbers. But if you tell me that the answer is "Yes" then I can verify that this answer is true merely by having you show me the '84' that you found...which is very easy to do. Of course if the answer is "No" then it's just as hard to prove that your answer is correct as it was to find the answer in the first place because to convince myself that you were right - I'd also have to look through all million numbers. So in this (very simple) case, it is certainly true that we have a easy check that a "yes" answer is correct for a problem that requires hard work to solve.
In P vs. NP, the definition of 'easy' and 'hard' is rather more formal than that and the example problem I just gave doesn't count as "hard"...but that's essentially the issue here. The commonest example of a 'hard' problem (in this context) is the travelling salesman problem. Given a list of cities and the distances between them, what is the shortest route that will allow someone to visit each of the cities at least once? For a large number of cities, the answer is very hard to find - and proving that it is indeed the shortest route is also hard to do...so this example doesn't help us to answer P vs NP. SteveBaker (talk) 14:04, 6 October 2008 (UTC)
Everything about P vs NP is easy to understand except the definition of "easy" (although even that isn't too hard). I think the whole thing needs to be easy to understand to qualify, personally, but that's just me. --Tango (talk) 15:32, 6 October 2008 (UTC)

To take another example from the Millenium Prize Problems, there are equivalent formulations of the Riemann hypothesis which are easier to understand. In response to a comment by Tango on the certainty of mathematical proofs, in the 19th century there was a proof of the four color theorem which was shown to contain errors only 11 years after publication! Icek (talk) 21:12, 8 October 2008 (UTC)

"Hologram" mirrors illusion??[edit]

Hi all, sorry if this question sounds a little bit silly. During a guided tour of a jewelry factory, we came up to a hexagon(I think)-shaped 'table', with a hexagon-shaped hollow space on its center which seemed to be covered in mirrors. Over the hole was a 'hologram' of a watch, but the thing is that the "hologram" had real colors, not those silly greenish-reddish colors holograms usually have! It genuinely looked like a real watch floating in place. We were able to see the watch from all around as if the watch was actually standing right there! They even allowed us to pass our hand through it (which made your eyes a little woozy somehow, focus-wise I guess). I'm sure the table itself wasn't a 'machine' of any sort, and that it must have been some weird illusion with mirrors (a real watch probably being inside the table thing), but I haven't seen that sort of thing anywhere else. My question is, how is that done? That's pretty much what I remember, and I'm still amazed at what I saw back then. I would love to know how they did that! Thanks in advance, Kreachure (talk) 21:33, 3 October 2008 (UTC)

This is an example of a real image. What you saw sounds like the "Mirage" toy mentioned/advertised in the article, though I don't know where to find a diagram of this particular case. You can buy them at places like museum gift shops. --Allen (talk) 22:54, 3 October 2008 (UTC)
Here, this website seems to have a good explanation. --Allen (talk) 22:57, 3 October 2008 (UTC)
(Edit Conflict) I'm not sure what these things are called, they seem to sell under the name "3d mirascope". (Google Search) There doesn't seem to be an article. Essentially there was a real watch inside the table, and through a clever arrangement of curved mirrors the reflection actually appears to be hovering above the hole in the mirrors. I've got one of these right here. The illusion is quite convincing. APL (talk) 23:01, 3 October 2008 (UTC)

Yeah, it's definitely that one, thanks, all! What I'm wondering now is why aren't they popular, because the illusion seems incredibly cool to me, even if it's (as I suspected) such a simple trick... I want one of those right now!!! :) Kreachure (talk) 23:13, 3 October 2008 (UTC)

They were popular as a novelty item, but they've been around for several decades. I remember seeing them advertised in the back of comic books in the 1960s and 1970s. ~Amatulić (talk) 23:36, 3 October 2008 (UTC)
There was even a very bad video game based on them back in the 80s. I don't remember what the purpose of the game was. It was the first 3-quarter game I ever saw, so I just watched a couple other kids waste some time on it and went to play other games. -- kainaw 23:38, 3 October 2008 (UTC)
Found the game - and it was 1991, not the 80s. Man, I am getting senile. -- kainaw 01:29, 4 October 2008 (UTC)
Reminds me of a gadget I saw in 1981 which used an oscillating mirror to build 3d images – wireframe only. —Tamfang (talk) 07:51, 4 October 2008 (UTC)
They sooo need to bring that style of game display back. :) ---J.S (T/C/WRE) 01:38, 6 October 2008 (UTC)

Mirage Mirror Musings[edit]

If you're able to create this kind of image with curved mirrors, is it possible to alter the image of the original to change its size? Maybe make it bigger? Maybe displaying the image a little higher instead of on the edge of the hole? Cause that would be even cooler! Kreachure (talk) 00:00, 4 October 2008 (UTC)

Science museums I've visited have had vertical versions set up that you can put your hand in to 'shake hands with yourself'. The image of your hand was flipped, if I recall, and the size depended on where you positioned your real hand - like with a normal mirror. So I imagine you could create a convincing larger image just by playing with distances. 79.66.115.246 (talk) 01:11, 4 October 2008 (UTC)
I have one of the toy ones. It makes the items inside of it appear noticeably larger. Also, telescopes have long used curved mirrors to make objects look larger. I suspect using mirrors to make objects look both larger and closer would be simple, though I'm not certain. — DanielLC 15:22, 5 October 2008 (UTC)

Water on Mars[edit]

Do Mars still have liquid water lye anywherr on crust? From what I learnt is Mars is a very cold planet. Do Mars even get to 25 Celsuis over summer equator. If it gets this warm then Mars might have some pink-orange oceans flown on it's surface. Usually tropical avg. on Mars surface is like below 0 Celsius, and the mid-lattitude on Mars surface si -53 Celsius, this is colder than Alaska over summer. Since Mars atmosp is alot thinner than Earth would it's 25 Celsius feel like 0 Celsius. The simple study is Mars is a very cold planet.--SCFReeways 22:26, 3 October 2008 (UTC)

There is no standing liquid water on Mars' surface due to the low atmospheric pressure, as discussed at Mars#Hydrology. Lower atmospheric pressure wouldn't cause Mars to feel "colder" so much as it would feel "less". There's less opportunity for conductive or convective heat transfer. — Lomn 23:14, 3 October 2008 (UTC)
  • This site say mars low is -125 F and high is 23 F, and rf#4 on Mars say the vg. surface temp. is -81 F. I thought Mars have greater surface range. The ext low I thought is like -180 F, and what about the extr high? Is the extr high like +50 F? The short answer is Mars is a very cold planet.--SCFReeways 23:57, 3 October 2008 (UTC)
Certainly small amounts of liquid water couldn't hang around for very long on the surface. Between the cold causing it to freeze and the low pressure causing it to boil - it's really not able to stay liquid for long. However, there have been discussions of underground liquid water possibly still existing - and there are suggestions that periodically, a large volume of liquid water may appear - flow for a while and then either boil away - or freeze and then sublimate. The Phoenix lander has observed ice sublimating into water vapor without ever becoming a liquid along the way. There is ample evidence that there HAS been liquid water there in the past - but the martian atmosphere may have been very different back then. SteveBaker (talk) 13:36, 6 October 2008 (UTC)