Wikipedia:Reference desk/Archives/Science/2007 April 1

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April 1

What will happen if you break a magnet

What will happen if you break a magnet into two pieces? I did a lot of research on this, but it seems every source state that "there will be a new north and south pole created at the point it break. No monopole magnet has been discovered." But, how do you explain the fact that the two pieces repel at the point it breaks? I break quite a few bar magnets and circular magnets, they all repel at the point they break. How do you explain that? If one of the two pieces switch pole (which it seems to be), how do you determine which piece switched pole? Rockvee 00:46, 1 April 2007 (UTC)

It depends on which way you break it, I think -- parallel or perpendicular to the N-S axis.

If you have a bar magnet, like this:

+-----------------+

|NNNNnnnn ssssSSSS|

|NNNNnnnn ssssSSSS|

+-----------------+

and if you break it in half, I believe it develops new south and north poles, like this:

+-------+ +--------+

|NNNnsSSS> >NNnsSSS|

|NNNnsSS< <NNNnsSSS|

+--------+ +-------+

and I believe that the two pieces will attract each other and stick together.

However, if you have a flat magnet, like this:

+-----------------+

|NNNNNNNNNNNNNNNNN|

|SSSSSSSSSSSSSSSSS|

+-----------------+

and you break it in half parallel to its N-S axis, like this:

+-------+     +--------+

|NNNNNNNN>     >NNNNNNN|

|SSSSSSS<     <SSSSSSSS|

+--------+     +-------+

then if you try to put it back together, its N face will be next to its N face, and its S to its S, and they'll repel each other, and it'll be as hard to put the pieces back together as it would be to put two of those flat magnets next to each other. —Steve Summit (talk) 01:04, 1 April 2007 (UTC)

wow, thanks for your clear answer! However if I remembered correctly, I break a bar magnet perpendicular to it's pole (1st case in ASCII diagram), it still repel. I used quite long and thin bar magnet with poles at the thin ends so I don't think I break it parallel to its pole.Rockvee 01:18, 1 April 2007 (UTC)

Yeah, that's what it sounded like you meant. All I can say is, next time you have the chance, try the experiment again. —Steve Summit (talk) 01:40, 1 April 2007 (UTC)

hmm, did you check the specifications of your magnet? sometimes the really long, thin ones are magetised on the long thin sides, not the long wide sides or the short thin sides. Coolotter88 01:53, 1 April 2007 (UTC)

And then there are those very flat, flexible sheet magnets, used for refrigerator business cards and dress-up toys and the like, which have alternating stripes of N lines and S lines. —Steve Summit (talk) 14:02, 1 April 2007 (UTC)

The magnets are labeled S and N so I am sure poles are on the thin sides Rockvee 02:50, 1 April 2007 (UTC)

Huh. (I suppose it's possible they're mislabeled...) —Steve Summit (talk) 14:02, 1 April 2007 (UTC)

It's worth remembering that the magnetic field of a bar magnet is simply due to the overlapping magnetic fields of all of its atoms, which are mostly aligned. Whether a magnet is in one piece or in two pieces being held together, the alignment of the atoms' fields is the same, and the resulting external magnetic field is the same. -- Beland 03:15, 1 April 2007 (UTC)

If it is possible for anyone, could you actually break a magnet into two and tell me what happened? Thanks. I t will be really intereting if you find out that they attract.....Rockvee 14:56, 1 April 2007 (UTC)

coral and sea level changes

--Nodman69 au 01:22, 1 April 2007 (UTC) my question is if sea levels a couple of thousand years ago were much lower than today how can coral reefs be millions of years old seems they grow a lot faster than people are saying if sea levels have been have been increasing at such a dramatic rate sorry it just dosent make sense to me if someone could explain in simple terms for a simpilton like me i would appreciate it--Nodman69 au 01:22, 1 April 2007 (UTC)

I don't understand what you're asking - note that, although sea levels have been rising due to the melting of ice caps, even 1 million years ago, there were oceans - the only reason oceans are rising is ice cap melting and icebergs falling into the ocean, and that's blamed on global warming, and that's not been going on for the whole million years. ST47Talk 01:38, 1 April 2007 (UTC)

I'm really not sure that the ice caps are melting? The sea ice is pretty much cyclic and Antarctica and Greenland I've found that there is getting to be more ice. [Mαc Δαvιs] (How's my driving?) ❖ 17:24, 1 April 2007 (UTC)

The earth has been warming since the last ice age. Glaciers have been retreating since the last ice age. That's pretty much the definition of ice age. I don't think the current global warming has seen actual measurable rises in see levels in the last 100 years. It's just too small a time scale. Ice ages are defined by whether glaciers are expanding or retreating. And lets look at the scale as well, the rise in sea levels is relatively smal compared to the overall depth of the ocean. I think the ocean average 2 miles deep. Sea level rises are measured in feet over millenium and millimeters over the last 100 years. The daily tide change is significantly more than any of globale warming changes. --Tbeatty 02:20, 1 April 2007 (UTC)

While coral species have been around for millions of years, living coral reefs exists no deeper than 50-100m. The above-posted chart (from sea level rise) shows that sea level has risen this much in the past 20 thousand years or so. Our article on the Great Barrier Reef points out the difference between fossilized coral in the area, which is indeed millions of years old, and the current living reef, which it says is about 20,000 years old. Perhaps there is some confusing about dead vs. living coral in the information you were looking at. Global warming is not the only threat; see Coral reef#Threats_to_reefs. -- Beland 03:06, 1 April 2007 (UTC)

ST47, you should really read up on the issues of global warming. There's still a lot of confusion about this, despite the immense importance of the problem. For the latest info check out the 2007 IPCC report. The rise of the sea level is so far caused mainly by the expansion of water. Water is at its most dense at around 4 C. Ocean water (even deep down) is warmer than that, so any rise in temperature will cause an expansion. It's minute in relative terms, but given the fact that the oceans are several km deep, 1 m is nothing - less than 1 promille (if we ignore for a moment that the base is narrower than the surface). However, the melting of icecaps (on land, so not the arctic ice sea) can cause a sea level rise of up to 60 m. Nows most of that water is locked up in the Antarctic and it would take very long indeed for that to melt. But the Greenland ice cap can melt a lot faster (possibly in a matter of decades) and that would cause a rise of up to 6 m. And even faster would be the collapse of the West Antarctic Ice Sheet, which would cause a similar sea level rise. Without warning, probably, or at least too fast to react to properly. But I diverge. DirkvdM 18:49, 1 April 2007 (UTC)

I suppose the reason is corals move with the sea level. The same coral reef would in the past, when the sea level was lower, heve been deeper down. Provided the sea level doesn't rise too fast, the new coral growth will be able to keep up. I wonder, though, what will happen to an atol that can not rise as fast as the sea level. If at some point it can't keep up it will die and have to wait until the sea level comes down again and spores from elsewhere will repopulate it. DirkvdM 18:49, 1 April 2007 (UTC)

Earth resources - oxygen production

I know that the ocean is suppose to produce most of Earth's oxygen but how much oxygen is produced by a square mile of sugar cane plants versus a square mile of rain forest? (same location) Nebraska bob 02:31, 1 April 2007 (UTC)

Er, just so we're clear here, did you say that the ocean produce's oxygen. I didn't know that Rfwoolf 11:17, 1 April 2007 (UTC)

The questioner is referring to oxygen production by phytoplankton. From that article: Through photosynthesis, phytoplankton (and terrestrial plants) are responsible for much of the oxygen present in the Earth's atmosphere. --NorwegianBlue ^talk 12:21, 1 April 2007 (UTC)

Great Apes

I have looked up almost everything on great apes and I've read that The United States Academy of Science has made a purposal to change chimpanzees scientific genus from Pan to Homo; which was made just last December. So I went to change the two chimpazee species on wikipedia to Pan or Homo, and it was re-edited and called me a vandlest. bibliography: www.greatapeproject.org —The preceding unsigned comment was added by 76.101.9.145 (talk) 04:06, 1 April 2007 (UTC).

I don't believe such a change would be accepted by the majority of the scientific community. Splintercellguy 04:35, 1 April 2007 (UTC)

The article bonobo already mentions such a proposal: "But there is still controversy. Scientists such as Morris Goodman[4] of Wayne State University in Detroit argue that the Bonobo and Common Chimpanzee are so closely related to humans, their genus name should also be classified with the Human genus Homo: Homo paniscus, Homo sylvestris, or Homo arboreus. An alternative philosophy suggests that the term Homo sapiens is actually the misnomer, and that humanity should be reclassified as Pan sapiens. In either case, a name change of the genus is problematic because it complicates the taxonomy of other species closely related to humans, including Australopithecus." The first part seems plausible, but the part about "alternative philosophy sounds like bullshit. --JianLi 04:37, 1 April 2007 (UTC)

I don't think you should be changing the these article based only on a proposal to moven them into the homo genus. If the proposal is accepted - then yes. If you have a solid reference to this proposal (ie something in a scientific publication or a book) - then you could add to the article the information that a name change has been proposed. I wouldn't describe your change as vandalism though - it was well intentioned. SteveBaker 04:12, 2 April 2007 (UTC)

Agreed. StuRat 23:19, 2 April 2007 (UTC)

This raises an issue that's always troubled me. Who or what decides when such a proposal becomes accepted by the scientific community? Is there a body that speaks for the entire scientific community? What if many scientists agree with the change, but there's a significant number who disagree? JackofOz 02:49, 3 April 2007 (UTC)

In the general sense, this is why it takes so long for new ideas to take hold. A few of the sciences have widely reputable, widely recognized "organizations" such as IUPAC (chemistry) and IEEE (electronics engineering). (I'm not a biologist, so I can't begin to say which organization carries the most clout in Great Ape taxonomy, but the journals Nature and Science are widely considered. When most of the publications of such organizations tout an idea, it can generally be considered "state of the art." There will always be various interpretations of the same facts and theories; these ideas form a spectrum spanning from mainstream to "quirky" to quack science. Nimur 06:23, 3 April 2007 (UTC)

Is this stuff for real?

It seems so much like a hoax, but it's on BBC. [1] [2] --Gujarat10 04:11, 1 April 2007 (UTC)

Depends of what do you mean by "real". Is there any magic force\energy that permeates the universe and all living things, that we can use to achieve super-human strength? Not really. This is just good ol' exercise and training. Martial artists develop strengthened muscles, tendons and skin, denser bones, control over pain, discipline, self-confidence and will power. That's all it takes to bend metal bars or pull a truck full of people with your penis. It just takes good training and patience. The qi stuff about it is just junk mysticism that really just distracts people from how amazing our bodies truly are. — Kieff | Talk 04:54, 1 April 2007 (UTC)

Well arguably, there's nothing to say that qi doesn't exist or that it's nonsense - it seems to work - but does of course doesn't mean it's scientifically sound either. So if it's not scientific and it's not mystical nonsense, then what can you say it is? A philosophy. Psychology for example is another series of philosophies over human behaviour - yet you can't really prove or disprove psychology because it's mostly intangible. Think of it this way, if psychology is "proven" by statistics and demographics, then qi is "proven" by the feats these people perform - and so we can try to establish a causal relationship; psychology is intangible and so is qi, but the results are usually real - the trouble comes in *not* proving the results, but in proving the causes. Since we can't scientifically explain/prove the cause, or scientifically disprove the cause, we can just call it a philosophy or discipline

Disclaimer: I mean absolutely no disrepect to pysychology, and if I've somehow miscommunicated then I apologise, this is what I was getting at: you cannot prove a psychological theory by looking at maps of the brain, yet you can put forth an idea for a cause of something and you will only be able to prove its effect. I could put forward a different cause and prove the same effect. If we have two different theories/causes, but the same results, who is right? Only in a philosophy can we both be right. Rfwoolf 11:46, 1 April 2007 (UTC)

Yeeeah, you've got science wrong. See Science, Scientific method, etc., for a decent overview. Psychology is a science (aside from far fetched hypotheses and some clinical psychology, etc.). Qi is, errr, not. -- Consumed Crustacean (run away) 11:49, 1 April 2007 (UTC)

That's why far-fetched hypotheses and certain clinical psychology techniques are discredited and frowned upon by scientific psychologists. Nimur 06:26, 3 April 2007 (UTC)

Sunblock and tanning

Does using a sunblock with SPF of lets say 70 get you less tanned than using spf30 or no sunblock? Or does it just block out the bad sun rays?

The bad sun rays are ultraviolet rays, which are also what make you tanned. So sunblock does slow the tanning process dramatically. --Bowlhover 15:30, 1 April 2007 (UTC)

Sunscreen. -Arch dude 16:14, 1 April 2007 (UTC)

BTW, there are two categories of UV rays (actually, the ultraviolet article says 3). Please note different sunblocks protect against different light frequency ranges. Root⁴(one) 19:40, 1 April 2007 (UTC)

cable modem

Male F Connector

i am thinking of getting comcast high speed internet with a cable modem. in order to use the service can i use a telephone jack to connect the modem or do i have to have a cable connector outlet nearby. the cable silver or gold thingy that sticks out.--logger 07:39, 1 April 2007 (UTC)

Typically one hooks up the cable modem to the coaxial cable jack that can also carry cable TV. Splintercellguy 08:11, 1 April 2007 (UTC)

Why not consider Google TiSP (Beta) ? —The preceding unsigned comment was added by Rfwoolf (talk • contribs) 11:48, 1 April 2007 (UTC).

You must connect the cable modem directly to the cable -- That's why it s called a cable modem. However, If you computer in not near a cable outlet, you can run an ethernet cable from the computer to the cable modem, or you can buy a WIFI modem (usually arouter/firewall/wifi) and connect it to the cable modem and then use a WIFI card at your computer. Be sure to read and heed the instructions for securing the WIFI. Also, buy and use a firewall/router even if you do not use WIFI. -Arch dude 16:06, 1 April 2007 (UTC)

If you are connecting it to a phone line, it's probably a DSL modem - not a cable modem. Cable modems hook up to cable-TV cables and have nothing whatever to do with telephone lines. If you are talking to Comcast - then you are indeed talking about a cable modem - so forget about phone lines - you need for the modem to be situated somewhere where there is a coaxial cable outlet...someplace you could plug in your TV. To get from there to your PC, you could use either a long ethernet cable (ethernet cables can be very long indeed without problems) - or you could get a Wifi box, connect that up to the cable modem - and then have a Wifi card in your PC and put it anywhere you like in your home. SteveBaker 04:08, 2 April 2007 (UTC)

The "thingy" is an F connector.

Atlant 12:23, 2 April 2007 (UTC)

Nothing about benefits of seawater

I've looked at sea, ocean, Sea_water and Saline (medicine) and they don't say anything about the benefits of sea water - and even googling it I don't get much.
I'm trying to ascertain if sea water is good for my eyes (if I immerse them) or my nose (if I sniff some) -- because I have a dry nose, nose allergies, dry eyes, and blepharitis (eyelid inflamation possibly caused by bacteria, dryness, chemicals, etc).
But I mean, in South Africa I know a lot of the Africans like to boil it and drink a cup - it apparently helps their bowel. I've even bought a nasal spray that deems itself "Microbiological sea water" - so how come there's nothing on Wikipedia about it?
Rfwoolf 13:25, 1 April 2007 (UTC)

I've managed to find Thalassotherapy - but this doesn't say much at all - and I wonder if it's meant to broadly refer to therapies from sea water, or, is it specifically talking about sea water's benefits on the skin. Rfwoolf 13:32, 1 April 2007 (UTC)

Drinking small or medium amounts of seawater, boiled, might be beneficial, as it contains useful salts and minerals (in larger amounts it could cause dehydration). I would think using it on sensitive parts of the body like eyes and nose would not be beneficial. When water is applied to skin, as it evaporates it dries the skin out. Also the salt crystals which would be left after evaporation can be abrasive and act as an irritant. On the eye itself, it would probably act like contact lens fluid and not be harmful, but would probably not be beneficial either. "Microbiological" sea water is sea water which contains microbes, such as ordinary, unboiled sea water. While I strogly doubt use of seawater will have any effect either way, please note the Wikipedia:Medical disclaimer. --h2g2bob 14:04, 1 April 2007 (UTC)

I would strongly discourage you from splashing seawater on your eyes or drinking it, as it's saltier than tears and also contains potentially harmful microbes. Use sterile saline solution or wetting solution instead, for the eyes. StuRat 23:01, 2 April 2007 (UTC)

If you feel the nead to clean or moisten your eyes or nose, then using salty water might feel less irritating as pure water because pure water pulls salts out of your cells (see osmosis). However, sea water is much saltier than the fluids in your body and in your body's cell, hence it will cause the same problem in reverse. What you should do, is just dissolve a little bit of salt, precisely so much that it tastes as salty as your tears. And, use pure, fresh, very clean water, and boild it before if in doubt. And I am not a doctor, only somebody with a friend, who has quite irritable, dry eyes due to blepharitis and feels eased by cleaning them with water, provided, it contains just the right amount of salt. Ask your pharmacist, by the way, for one of these little plastic cups shaped to match the eye socket to get the water to your eyes. There is also a thing shaped like s miniature watering pot to pour water through your nose. I saw one product that comes with "special Himalaya salt", but this nonsense, of course. Salt is salt, at least for this purpose. Simon A. 15:56, 3 April 2007 (UTC)

Sterile saline solution for contacts lenses is sold in 16 oz containers (about 1 L) at quite a reasonable price, so there's no need to risk creating your own. StuRat 01:50, 4 April 2007 (UTC)

process to manufacture Magaldrate

59.95.222.135 13:38, 1 April 2007 (UTC)Dear Sirs, Kindly provide us a process to manufacture Magaldrate ( an Antacids)

Thanks

yours faithfully Vasantbhai

I guess our Magaldrate article isn't much of a help, is it? —Steve Summit (talk) 17:02, 1 April 2007 (UTC)

The article does not explain the manufacturing process, although it does give a formlua. So the question is not answered yet! GB 13:20, 2 April 2007 (UTC)

radar displays

please help me about the types of radar displays??thank you —The preceding unsigned comment was added by Ambuj0542 (talk • contribs) 14:22, 1 April 2007 (UTC).

See Radar

To briefly summarize, the old type was an oscilloscope, usually a circular display with a green radial line rotating around the screen and green blips of various sizes appearing as the line passed, and then slowly fading. Newer displays tend to be completely computerized, with radar info going into the computer and the computer generating info on the screen with not only the position of the object, but also altitude, vector, and identifying info. Different geometric shapes and colors are now used to identify different types of radar contacts. StuRat 22:45, 2 April 2007 (UTC)

Optics: dispersion

If we pass light through a cuboidal glass slab, does the light disperse? If not, why not?

[I have read in my textbook that a cuboidal glass slab can be divided into two triangular based prisms kept adjacently and inversely to each other. So the light disperses and again recombines. But to recombine, the light must be refracted at the beginning of second prism and end of first prism(the border between the 2 prisms). But at this point there is no change of medium. So there cannot be any refraction.] 59.92.245.30 17:00, 1 April 2007 (UTC)

Angle of incidence could be useful

A little thought would allow you to answer this for yourself. A window is a cuboidal glass slab - what happens when you look out of the window? Is everything magnified? Fuzzy? Smaller? ...Nope - I guess not. SteveBaker 17:00, 1 April 2007 (UTC)

The downside of quitting smoking

I stopped smoking just over two weeks ago (apart from a cig or two in the evening), and ever since I can't think straight. Whenever I start reading something it just doesn't stick in my head (or how do you say that?), no matter how often I read it. (Which, btw, is the reason I decided to have another look at the ref desk, to have some light reading.) Is this a common phenomenon? A few threads back, Kurt Shaped Box suggested one gets a cold more easily when one stops smoking, but it's not a cold. It's a lethargic feeling. I can do physical work, though - I do even more walking than normal, just to have something to do. But I have no 'lust for life', no willpower, the drive is gone. I should add that I've halved my alcohol consumption as well. And all this started when I had a flu. So I didn't smoke or drink for several days and then decided to make use of that and quit (almost) entirely. Damn, I can't even tell this story in a coherent way. Any explanations anyone? DirkvdM 18:04, 1 April 2007 (UTC)

Withdrawal symptoms? 8-) —The preceding unsigned comment was added by 88.110.49.118 (talk) 18:06, 1 April 2007 (UTC).

Yes, that's the obvious answer, but I don't see any mention of my problem there. I was expecting to feel clearer in the head, at least after a while, but to have the opposite effect, and for two weeks unabated, is not what I bargained for, so to say. DirkvdM 19:07, 1 April 2007 (UTC)

Yeah, I get like that for a couple of weeks whenever I stop smoking. When accompanied by the standard "quitter's cough", it doesn't make for much of a fun time. Then, when I've got that out of the way, I start with the "Why don't I just smoke a couple a day? It couldn't hurt" thoughts (which swiftly go out of the window after the "first cigarette of the month" and the associated "every nerve in the body lighting up like a Christmas tree" feeling reminds me of why I started smoking in the first place... :) --Kurt Shaped Box 23:12, 1 April 2007 (UTC)

Depression?

• Depending on how well your body can adjust, withdrawal symptoms may take longer to disappear if you have been smoking longer. 0_ Mgm|^(talk) 12:25, 2 April 2007 (UTC)

Yes, I've been thinking about that too. The fact that I have smoked for about 30 years would make the shock to the body rather severe. Btw, I have also once heard that for the lungs to clear takes about as long as one has smoked. In which case I've got the nice prospect of having clean lungs by the time I die. :) Luckily, I've also recently read that it takes about a year, irrespective of how long one has smoked. These conflicting stories have made it so difficult to convince myself to stop smoking - I have heard so much nonsense that I tend not to believe anything I hear anymore. It's sort of like with the environmentalists having aggravated the problem of climate change. They were so fanatic that half of mankind refused to believe anything they said. So only now that the problem has become so obvious that even the most hardened critic has to believe it, that politicians are considering actually doing something about it. Hopefully this time they will do what they say. Yeah, right.... DirkvdM 17:10, 2 April 2007 (UTC)

Human breast milk

Just how much volume of milk can each human female breast produce per day and how is this enought to feed a baby?

You may wish to check out breast feeding which addresses these questions, at least a little bit. Friday (talk) 18:27, 1 April 2007 (UTC)

are vets doctors?

If I write a letter to my vet do I have to call him Mr Vet or Dr Vet? —The preceding unsigned comment was added by Humps (talk • contribs) 18:28, 1 April 2007 (UTC).

Totally off-topic, but my butcher is called 'brothers Vet', named after the owners. In Dutch this works out well because 'vet' means 'fat'. In English, it sounds a bit more awkward - where do they get their meat from? :) DirkvdM 19:00, 1 April 2007 (UTC)

In the U.S., veterinarians are addressed as "Doctor". (Or at least, I always have.) —Steve Summit (talk) 19:03, 1 April 2007 (UTC)

Anyone with a doctorate degree (such as Ph.D., M.D., O.D..etc) in any field is addressed Dr. In the U.S. and Canada, all vets have doctorate degrees. —The preceding unsigned comment was added by 209.53.181.75 (talk) 19:15, 1 April 2007 (UTC).

Well, there is at least one exception, Juris Doctor. Lawyers are rarely addressed Dr. in the U.S. --Allen 19:20, 1 April 2007 (UTC)

Canada follows US practice here, except that lawyers not only aren't called "Dr.", their degree often isn't called a doctorate anyway. In Britain, I've read, it's different: veterinarians there do not use "Doctor", and more interestingly, neither do surgeons. So if we follow the prevalent practice in punctuating abbreviations, it's "Dr. Vet" but "Mr Vet". --Anonymous, April 1, 2007, 20:57 (UTC).

The person who said all vets in the US and Canada have a doctorate degree is definitely incorrect, not even most general practitioners have a doctorate degree. The Veterinarian article has a "Education and regulation" section. Vespine 22:47, 1 April 2007 (UTC)

According to doctorate, in the Unites States doctors of veterinary medicine are considered to have a professional doctorate. Of course, much more is required to attain a research doctorate. I think most people hearing doctorate would equate it with a research doctorate. -Joelmills 00:23, 2 April 2007 (UTC)

In UK there is a kind of reverse honor sytem for surgeons. Senior surgeons prefer the title "Mister" to "Doctor"...probably surgical veternarians have the same preference. SteveBaker 03:57, 2 April 2007 (UTC)

Heartburn

Why do I sometimes confuse heartburn for hunger? —The preceding unsigned comment was added by 209.53.181.75 (talk) 19:17, 1 April 2007 (UTC).

What you ask, phrased as a subjective, personal experience, can't be answered here. However, if you're experiencing uncomfortable symptoms, you may be suffering from an undiagnosed and untreated medical condition. I'd suggest a course of action that includes:

• consulting a physician through your local health clinic
• reading about your symptoms on Wikipedia pages, e.g. Heartburn and Gastroesophageal reflux disease
• checking the info available on a health website such as Medline Plus, that has pages on heartburn, chronic heartburn, a.k.a. gastroesophageal reflux disease, and heartburn prevention

Hope that helps -- Deborahjay 23:26, 1 April 2007 (UTC)

Doesn't eating help against heartburn? If so, it could be sort of a pavlovian effect. You once noticed that eating helps against heartburn, just like it helps against hunger, so the link between the two suggests they're 'the same'. DirkvdM 18:40, 3 April 2007 (UTC)

Apes and monkeys

Why does the Arabic wikipedia article for Ape and Monkey both point to the same page? was the link made by someone that ignorant or do they have a word that collectively refers to apes and monkeys, and/or not have seperate words for ape and monkey? do we have a word in english that refers to apes and monkeys collectively? (not Primate, because that includes lemurs, and they have a seperate Arabic wikipedia article for primates). —The preceding unsigned comment was added by 209.53.181.75 (talk) 19:21, 1 April 2007 (UTC).

I can only help with the last question... the answer is yes; see simian. --Allen 19:26, 1 April 2007 (UTC)

Most of the IW links for Ape are to pages called either 'Hominidae' or a word meaning 'human-like somethings' (presumably a translation of 'Hominidae'). On the other hand, many of the IW links from Monkey are to words that are clearly related to 'Ape', but apart from Arabic, all the ones I have looked at do seem to be about monkeys not apes. So it rather looks as if many languages do not have a non-scientific word for 'Ape' distinct from 'Monkey', but that most WP's have used a scientific term for the page corresponding to 'Ape'. --ColinFine 22:19, 1 April 2007 (UTC)

Osmosis question

If there's a membrane and on the left of it, the solution has a higher molar concentration of water (moles of water per litre), while the solution on the right side has a higher percentage of water by mass (kilograms of water per kilogram of solution), which direction will water move through the membrane?

Osmosis talks in terms of 'Molar volume', so I imagine that the answer will depend on the relative molecular mass of the solute. --ColinFine 22:25, 1 April 2007 (UTC)

Water moves through the membrane in both directions. It's just that more of it moves in one direction than in the other. DirkvdM 18:44, 3 April 2007 (UTC)

Kiloyottabyte, megayottabyte etc.

Why is there a prohibition on using multiple SI prefixes on the same unit? It seems to me this would be the easiest way to extend the scale beyond 10^±24 and still be understood -- after all, it's easy enough to figure out how large a kiloyottabyte is. NeonMerlin 20:35, 1 April 2007 (UTC)

Well, that would be because the people who control this stuff don't agree that it's easiest. Before the prefix "pico-" was invented and came into common use, we used to see forms like "micromicrofarad", and if it went further with "micromicromicro-", it could get hard to read. Admittedly Neon's idea is not as repetitive as that, but the principle of "use no more than one scaling prefix" is easy to understand, and that's a virtue. Besides, if you need to say "× 10²⁷", you always have the option of just saying "× 10²⁷". --Anonymous, April 1, 2007, 21:00 (UTC).

Furthermore, the specific issue of measuring bytes at these large exponents introduces significant uncertainty as addressed in binary prefixes. Is a yottabyte 2⁸⁰ or 10²⁴ bytes? There's actually a fairly significant difference! -- mattb @ 2007-04-02T02:54Z

There is an IEC standard to resolve that. Replace the final two letters of the SI prefix with a 'bi' to refer to 2¹⁰ intervals rather than 10³. So - Mebibyte is the "binary megabyte". Check out our article on Binary prefixs for more detail. Admittedly, not many people are using the standard (especially in common speech) but the usage is growing. In this case, a yottabyte would be 10²⁴ and a yobibyte would be 2⁸⁰. A yobibyte would be an ungodly amount of storage. It has been estimated [3] that the entire Internet - web pages, email, IM's - everything represents about 532,897 terabytes. That's half an exabyte. So one yottabyte would be enough to store two million copies of the entire Internet! We are a long way from needing words to talk about yottabytes or yobibytes! SteveBaker 03:52, 2 April 2007 (UTC)

Vibrating air columns

I am wondering why in a vibrating air column with one side closed the wavelength of the sound produced is equal to 4 times the length of the column. I've tried researching it and I just don't see it at all. 74.73.109.111 21:30, 1 April 2007 (UTC)

     air vibration
        |
        V
    |\          /| <- antinode (max air displacement)
    |.\        / |
    |  \      /  |  <- tube closed at bottom, open at top
    |   \    /   |
    |    \  /    |
    |     \/     |
    -------------
          ^
         node (no air displacement)

The V in the centre represent the the amount of vibration or air movement in the closed tube. Athe the open end we have an antinode( max displacement of the air) and at the closed end there is a node (no displacement). THe distance between the peak displacement and the no displacement points must be 1/4 of a wavelength. S o the wavelength is 4 * l (where l is the tube length). Get it now?

Oh, I get it! Thanks a ton! So I'm assuming that in a compression/expansion diagram for a sound waves, the nodes are at the point between the center of the expansion and the center of the compressions; the point of least amplitude. Muchas gracias!  :-) 74.73.109.111 22:36, 1 April 2007 (UTC)

Why does this show nodes at the open end though? 74.73.109.111 22:43, 1 April 2007 (UTC)

That paper is considering pressure for some weird reason rather than velocity (which I was always taught was the way to consider it at school). Anyway a pressure node is a velocity antinode and vice versa, so we're both right!

Also dont forget that the V in my diagram just indicates the magnitude of the standing wave in the tube at any point. Sound waves are of course longitudinal.

And again, you can get higher frequencies out of any one length of pipe. These frequencies will be:

3,5,7 etc times the lowest frequecy (longest wavelength) All you need is a velocity node at the closed end, and a velocity antinode at the open end :-)

Yeah, I figured out the harmonics once I understood this, and knew that sound waves were longitudinal. Thanks again for the clarification and all your help! 74.73.109.111 20:42, 2 April 2007 (UTC)