Wikipedia:Reference desk/Archives/Science/2010 March 30

= March 30 =

US household voltage
Most residential houses in the US appear to be supplied with 220-240 voltage which is split into 2 legs with each leg carrying 110-120 volts AC. Both legs seem to be connected by a neutral that is sometimes referred to as ground. Does this mean that one of the wires in a wall outlet has not difference in voltage that the ground outside or the floors in the house and that the bottom of the sin or cos wave for each leg is where neutral is actually at rather than at the zero point of the wave? 71.100.3.207 (talk) 02:24, 30 March 2010 (UTC)


 * To your first question: yes, one of the prongs is at ground potential.
 * To your second: it's hard to describe without drawing a picture. Each of the "hot" "phases" oscillates to a positive and negative voltage about that neutral.  The scheme is described in our Split-phase electric power article.  (Too bad there's not a picture on that page, either.) —Steve Summit (talk) 02:30, 30 March 2010 (UTC)


 * Splitphase.gif]] Okay, here's a simple illustration. The black wire alternates from +120V to -120V with respect to the neutral (white) wire, which stays at ground potential (0V).  Meanwhile, the red wire is alternating from -120V to +120V, 180 degrees out of phase.  The voltage from either the black wire or the red wire with respect to the white wire is 120VAC.  But if you connect a load across the black and red wires, you get 240VAC.  (As you can see from the figure, at any given instant, the distance from the black curve to the red curve varies from +240 to -240.)  This is how you can get 120V for ordinary household appliances, or 240V for high-power appliances such as electric stoves, ovens, and clothes dryers.  (These are of course the voltages for North America; YVMV.) —Steve Summit (talk) 03:26, 30 March 2010 (UTC)


 * Please provide an English translation for "has not difference in voltage that the ground outside or the floors in the house and that the bottom of the sin or cos wave for each leg is where neutral is actually at rather than at the zero point of the wave?" Edison (talk) 05:09, 30 March 2010 (UTC)


 * I believe the first part has to do with the distinction between a floating ground and an earthed ground. That is, is neutral (zero) voltage in the electrical distribution system 0V with respect to a metal rod sunk into the ground. The answer to that, at least at the household level, is yes. The neutral bus bar in the electrical distribution panel in most US homes is directly tied to a metal rod sunk into the soil. The second part is asking about where the zero reference point is on the sinusoidal wave of the live conductor - does the alternating voltage swing from -120V to +120V (or whatever the numbers happen to be) or from 0V to 240V (with respect to the given neutral "zero"). In US household current it's the former. -- 174.31.194.126 (talk) 06:15, 30 March 2010 (UTC)


 * A U.S. utility is typically allowed to let the voltage (at the meter) vary +/- 6 volts from the nominal 120. With voltage drop along the branch wiring in the house, this typically still supplies at least 110 volts at the outlet in the house. During peak loads there may be a "brownout" which causes voltage too low for some equipment to operate. The peak of a 120 RMS voltage is higher than 120 volts. To get the peak value, divide the RMS of a sinusoid by .707 and the result is 169.7 volts. A cheap (non-RMS) voltmeter will report a voltage other than the RMS value if the waveform is distorted, but will correspond to the RMS value for a pure sinusoid. So the voltage to neutral/earth from a "hot" wire varies typically from about -170 to about +170, 60 times per second (in the U.S.). If there is distortion (harmonics) in the waveform, the peak may vary substantially. The 240 volts in household supply is the RMS measurement between the two "hot" conductors. In 120/240 supply, the transformer low voltage winding is center-tapped for the neutral, so the two hot supply lines measure 120 from the neutral. The neutral is typically grounded to a substantial metallic low resistance earth ground at the transformer and at the neutral bus of the electric panel. The earth ground in the house might be a metallic cold water pipe coming in from the street, or it might be a driven ground rod. If the neutral were ungrounded, such as in the case of the ground at the utility pole not being connected and the neutral at the house power panel not being grounded, there would still be 240 between the hot wires and 120 from either of them to the neutral wire, but with no earth ground there could be very high voltage, up to the primary voltage, between any of the supply wires and ground, a very hazardous situation. Edison (talk) 16:04, 30 March 2010 (UTC)

Role of the Pudendal Nerve in male sexual function?
I've been studying the role of the Sympathetic Ganglion in sexual intercourse, and I am stumped when it comes to the role of specific neurons in the male ejaculatory function.

As far as I can tell, the Prostatic Plexus and the Pelvic Splanchnic Nerves relay the sensory function —as well as increased heartbeat, blood pressure, body temperature, etc.— and the Pundendal Nerve relays the motor function (enabling ejaculation).

To wit, the Sympathetic Ganglion conveys the relexive arc from the genitals to the spinal cord (and back again), whereas the sensation of arousal/orgasm is received (some time later) by the brain.

My question, however, relates to the Pudendal nerve's function apropos ejaculation and the (subsequent) termination of sexual excitement —and the start of the refractatory period.

If —during the act of coitus— the Pudendal nerve were numbed or incapacitated, how would that affect a male's sexual performance? Would a man become able to feel the thrill of ejaculation for an extended period of time, without actually ejaculating (or losing his arousal)?

Could this increase one's virility and sexual powers? Pine (talk) 02:39, 30 March 2010 (UTC)


 * There is a technique, taught to couples where the men suffers premature ejaculation, where the perineum is pressed and held in just before ejaculation: this is said to delay ejaculation. I'm not an expert on human anatomy, but is this where this particular nerve is situated? --TammyMoet (talk) 08:16, 30 March 2010 (UTC)


 * To save further responders a little time, let me provide the link Pudendal nerve. (Yes, I could have linked one of its previous mentions, but I didn't want to bring down the Wrath of Steve :-) .) 87.81.230.195 (talk) 10:20, 31 March 2010 (UTC)

PAC MAN MOON
I seen a quick article on the PAC MAN MOON shape (Saturn i think) It seemed glaringly obvious to me that the with the giant impact area that the energy transfered from the impact through the planet to other side and this was some sort of risidual engery left over from this. Ok maybe i am completly wrong but thats what struck me looking at it? So the question is i suppose could this be the case? —Preceding unsigned comment added by Chromagnum (talk • contribs) 05:18, 30 March 2010 (UTC)

Sorry link and Chromagnum (talk) 05:22, 30 March 2010 (UTC)


 * Your description in terms of energy sounds pretty ropey. However, the idea that the creation of the Herschel crater could be linked to the variations in the observed temperature is suggested in the article you provided:
 * "The Cassini team says the creation of the crater itself might have played a key role in changing conditions across extensive regions of the moon's surface."
 * So they're possibly related but I'd suggest reading up on energy a bit. 129.234.53.144 (talk) 12:07, 30 March 2010 (UTC)

The Cassini-Huygens probe has an official website from NASA. Here's a little more technical information from the NASA/JPL Press Release: 1980s Video Icon Glows on Saturn Moon. The early assumption is that the temperature difference is due to surface texture changes, which affect the heating and cooling rate. "Even if surface texture variations are to blame, scientists are still trying to figure out why there are such sharp boundaries between the regions, Spencer said. It is possible that the impact that created Herschel Crater melted surface ice and spread water across the moon. That liquid may have flash-frozen into a hard surface. But it is hard to understand why this dense top layer would remain intact when meteorites and other space debris should have pulverized it by now, Spencer said.". Nimur (talk) 14:48, 30 March 2010 (UTC)

Energy/Heat yes bad wording on my part wanted a quick answer just seemed blatanly apparent the two would be linked thanks for your answersChromagnum (talk) 17:07, 31 March 2010 (UTC)

Number of organs
I've read that humans have 22 or 23 organs depending on how you count.

Do all mammals have 23 organs?

What about fish? Birds? Reptiles?

How many organs do tunicates have?

-Craig Pemberton 07:22, 30 March 2010 (UTC)

Seriously, unless the IAU decides what is an organ and what is a dwarf organ, I don't think it matters much. 88.242.231.192 (talk) 10:28, 30 March 2010 (UTC)
 * How do you define an organ? Are cerebrum and cerebellum seperate organs? What about hypophysis? Is it an organ on its own or a mere extension of the brain? The eyes? If the stomach is granted the title of organ, what prevents the poor duodenum from being called one? Maybe the entire gastrointestinal tract is a single organ, then. Last thing I heard, salivary glands have been lobbying for independence.


 * Maybe he was thinking of chromosomes? Humans have 23 pairs of chromosomes, often split into the 22 pairs of autosomes and one pair of sex chromosomes. His numbers match this fairly precisely. If he meant chromosomes, the answer is that the number of chromosomes varies wildly from species to species (note that the preceding link gives total number, not number of pairs, so humans show up with 46). &mdash;ShadowRanger (talk 12:21, 30 March 2010 (UTC)


 * No. I mean organs. Yes, I realise it's hard to quantify natural phenomena that fall on a gradient such as languages, planets, species, and organs. That does not mean that questions regarding them are not interesting or important. -Craig Pemberton 13:22, 30 March 2010 (UTC)


 * Well, anyways, other animals, even other mammals, have organs that we do not share. Ruminants have a much more complex digestive system, for example. And I have it on good authority that many politicians manage without a neocortex. --Stephan Schulz (talk) 14:08, 30 March 2010 (UTC)


 * (ec)If you can't rigidly define an organ, then your question is meaningless. I have found at least one source that supports your "22 or 23" contention (where the 23rd is the skin, though it neglects to enumerate the rest). I can guarantee you that the number of organs in other animals would not match those of a human though, except by coincidence or in cases of extremely recent speciation (many of the apes may match us though). According to the page I'm referring to, the definition is "a relatively independent part of the body that carries out 1 or more special functions." Given that the appendix would probably not count as an organ under that definition, it would logically follow that any mammal with a functioning appendix (that actually serves the purpose of digesting cellulose) would not have a matching number of organs. Most herbivores have one, so the number wouldn't match. Similarly, many herbivores have multiple stomachs, which would screw up the calculation. And we haven't even left mammals yet. Birds, reptiles, etc., all have substantially different digestive tracts, reptiles, being cold blooded, don't have a liver in the same sense as humans, non-mammals wouldn't have a direct analogue to the mammalian reproductive system, etc. &mdash;ShadowRanger (talk 14:14, 30 March 2010 (UTC)


 * Similar to variations in the digestive system, how about variations in the scent glands of animals, such as skunks ? Venom producing/delivering organs would be another.  Then some animals have other sensory organs, like extra UV and infrared-sensitive eyes and pits, and the echo-location "melon" on a porpoise or dolphin.  Also, some animals have organs which provide the ability to sense weak, or create strong, electrical fields.  Only (female) mammals have (milk producing) breasts and a uterus. StuRat (talk) 14:21, 30 March 2010 (UTC)

Evolution - E. coli
Greetings! Two questions:
 * How old - evolutionwise - is E. coli? (~ 300-400 Mill. years?)
 * As it is not found in the guts of cold-blooded animals (molluscs, fish) what ist the main type of gut bacteria in these species? Thanks Grey Geezer 07:26, 30 March 2010 (UTC) —Preceding unsigned comment added by Grey Geezer (talk • contribs)


 * This link discusses several bacterial evolution estimates; one is "About 4.0×108 years [ago]: gram-negative, microaerophilic bacteria become Enterobacteriaceae in vertebrates in addition to the strictly anaerobic organisms." E. coli is in this category.  You are correct; that is 400 million years ago.  Comet Tuttle (talk) 16:41, 30 March 2010 (UTC)
 * Thanks! Problem seems to be the poor fossil record, so only genetics and mutation rates are used for time estimates. Grey Geezer 07:41, 31 March 2010 (UTC) —Preceding unsigned comment added by Grey Geezer (talk • contribs)

why pumice stone
i have a practical in course its aim is to determine the boiling point of the given sample of water. in the setup of apparatus we are said to put some pumice stone in the boiling tube containing water.
 * tell me why that pumice stone is to be kept? {its not a HW question its indeed a doubt}

in precaution it is clearly mentioned that "the bulb of thermometer should not dip in liquid. it should be about 4-5 cm above the liquid surface."
 * BUT surely then the thermometer will note the tempreture of stem which will not be correct? please clear my doubt —Preceding unsigned comment added by Myownid420 (talk • contribs) 07:33, 30 March 2010 (UTC)
 * You can measure the boiling point of water by measuring the temperature at which steam condenses (on the thermometer, for instance). Therefore the thermometer does not need to be immersed in the water. As for the pumice, its purpose is to assure that the water boils at its boiling point instead of superheating. If the water is quite pure, and the vessel in which it is heated is quite clean and smooth, then the water is liable to be heated above its boiling point and then violently erupt, yielding a false measurement (and possibly giving you a nasty burn as well). The porous pumice provides a rough surface on which the water will readily vaporize into bubbles. You can read more here, in considerable detail.--Rallette (talk) 09:27, 30 March 2010 (UTC)


 * See also boiling chip, if you ever need to buy some from a catalog. As Rallette notes, small, inert, irregularly-shaped chunks with a large surface area (for their volume) are used to discourage superheating and violent bubbling. TenOfAllTrades(talk) 13:07, 30 March 2010 (UTC)

transpiration

 * is it so that a tree on high altitudes will have more or less transpiration, assuming that temperature is same for it in comparison to another tree at lower altitude...thanx--Myownid420 (talk) 07:37, 30 March 2010 (UTC)
 * There seem to be quite a few studies on this. The abstract of the first one in my search says: "An important factor at high elevations is the reduced barometric pressure. It has long been recognized that the reduction of air pressure brings about an increase of evaporation, and the increase of plant transpiration in response to low air pressure has also been demonstrated under laboratory conditions." Other factors also seem to influence the rates of transpiration at different elevations; your best bet is to read some of the articles for yourself. Deor (talk) 11:52, 30 March 2010 (UTC)

Scalar energy
In theoretical physics, has anyone ever conceived the notion of scalar energy ? I was thinking that the LHC in Switzerland might help discover it. 70.31.243.126 (talk) 12:14, 30 March 2010 (UTC)


 * You're going to need to be more specific. An article red link isn't all that helpful. &mdash;ShadowRanger (talk 12:16, 30 March 2010 (UTC)


 * Especially since energy is a scalar in pretty much any formulation of physics. -- Coneslayer (talk) 12:18, 30 March 2010 (UTC)


 * I don't really like this source, but I sums up what I was talking about. 70.31.243.126 (talk) 12:20, 30 March 2010 (UTC)


 * Note that at that site, they mention the World Trade Center, Iraq conspiracies, and conspiracies around Tesla (this one actually has a bit of truth to it). It's surprising they don't mention the JFK assassination and the rise of Hitler. StuRat (talk) 15:47, 30 March 2010 (UTC)


 * I don't blame you for not liking that source, as it has all the hallmarks of crackpot pseudoscience.


 * Whenever someone says they've got an extraordinary new theory, which is unbeknownst to (and is perhaps being suppressed by) mainstream science, it's possible in some theoretical sense that they're right -- science does always consider the possibility that it's wrong, and it does always have more to learn -- but it's spectacularly, ludicrously, vanishingly improbable. Electromagnetic waves aren't an energy source anyway, so to suppose that these hidden, different kind of waves could somehow provide limitless "free" energy is just, I'm sorry, nonsense. —Steve Summit (talk) 13:14, 30 March 2010 (UTC)


 * The source you cited links to this one, and a Google search yields plenty more, but they all have the same unignorable whiff of magical thinking about them. —Steve Summit (talk) 13:20, 30 March 2010 (UTC)


 * According to the feedback column of New Scientist the "scalar energy" notion is an increasingly prevalent brand of what it calls fruitloopery. Consensus on Wikipedia, for what it's worth, said pretty much the same thing: Articles for deletion/Scalar field theory (pseudoscience). However, unless I am missing something, I disagree with Steve Summit's assertion that electromagnetic waves aren't an energy source. See for example solar power. Steve - perhaps you mean that they aren't an "ultimate" energy source, in that they must have been generated by something else such as nuclear reactions within the sun, but under that interpretation kinetic energy wouldn't be an energy source in lots of real world situations either. Equisetum (talk) 14:01, 30 March 2010 (UTC)


 * Yes, I think he meant that they carry energy, but aren't the source, similar to electricity. StuRat (talk) 15:27, 30 March 2010 (UTC)


 * I made the point a bit too hastily, but Stu caught my meaning. I think of electromagnetic fields and waves as being a means of transmitting energy, but not of storing it, let alone being a source of it.  (Although it'd probably be hard, I concede, to rigorously distinguish between a "source" and a "storage", if it came to that.) —Steve Summit (talk) 16:57, 30 March 2010 (UTC)


 * Just curious; wouldn't it be more useful to have an article on scalar energy that says it's crap rather than just not have one at all? I'm not familiar with the WP deletion policies but common sense says that having information telling you it's highly improbable leads to less confusion than no information at all.  I'll read into the guidelines further and perhaps I can answer my own question.  -Pete5x5 (talk) 14:47, 30 March 2010 (UTC)


 * For very common ideas, like perpetual motion, we have an article explaining the common fallacies. Unfortunately, there is no limit to the number of incorrect theories - it's hard to have an article on all of them.  We reserve our articles for only those most important pseudoscientific theories - the ones which are notable.  Nimur (talk) 15:07, 30 March 2010 (UTC)


 * This seems to be another name for zero-point energy. See Zero-point_energy for a discussion of why this is impossible. StuRat (talk) 15:33, 30 March 2010 (UTC)


 * So that web page links to http://Cheniere.org - which will be instantly familiar to old hands here at the science ref desk. Not that we've necessarily seen that page before.  You don't even have to read it.  It has lots of

Centered text In lots of different fonts' ''AND many different sizes


 * For some reason, this style of web page is completely unique and almost universal amongst pseudo-science nut-jobs. I have no idea why - but it's almost 100% reliably so. SteveBaker (talk) 00:47, 31 March 2010 (UTC)


 * Still, the guy shows remarkable restraint in not using a bunch of different colors. APL (talk) 16:45, 31 March 2010 (UTC)


 * He must be both nuts and color-blind. :-) StuRat (talk) 01:04, 1 April 2010 (UTC)

Why does swishing water help my toothache?
My last molar on the upper left is giving me trouble. I had a crown placed on it a few years ago, and several months ago, ¼ of it broke off. I haven't had the money or the insurance to get it fixed until now, and it hasn't given me much discomfort until the past week or so anyway. (This is not a request for medical advice, because I *know* what I need to do-- have the dentist fix my tooth. I have the appointment. It's in May.) The associated toothache comes and goes, but when it comes, it sometimes is blindingly bad. I'm taking Ibuprofen and treating topically with Orajel, which helps some. However, I have also found that swishing slightly-below-room-temperature water around my mouth also helps ease the pain some. I'm just wondering why this might be. Any ideas? Thanks very much-- Kingsfold (talk) 13:57, 30 March 2010 (UTC)


 * Cooling the nerve may be helping you a bit. Cold brings a certain amount of numbness, and if your tooth is damaged, the nerve is exposed more directly to the cool water. If the tooth is infected, the cool water may also be reducing swelling a bit. You may also be reducing the degree of infection a bit (by washing away some of the pathogens), but that isn't likely to have a measurable effect on your pain, and they reproduce quickly enough and enough of them are likely unreachable by the water that the long term effect is negligible. &mdash;ShadowRanger (talk 14:18, 30 March 2010 (UTC)


 * Thanks. However, I had some slushy (partially frozen) lemonade yesterday, and five minutes later, I thought I was going to die.  So, apparently not TOO cold? Kingsfold (talk) 14:40, 30 March 2010 (UTC)


 * Too cold is going to be a problem, but lemonade (regardless of temperature) would probably make it worse. Lemonade is quite acidic, and contains a lot of sugar (which bacteria in your mouth process, producing more acids). &mdash;ShadowRanger (talk 15:19, 30 March 2010 (UTC)
 * Might be the acid in the lemonade, but it was Crystal Light, so... no sugar. I'll try another flavor today (not frozen), and see if it still causes trouble. Kingsfold (talk) 15:48, 30 March 2010 (UTC)
 * May seems like a long time to wait while you are in such distress, can't you get an appointment with a dentist sooner ? StuRat (talk) 15:41, 30 March 2010 (UTC)
 * Great idea. Wish I had thought of that. (Wink.) I'm on the "call if someone cancels" list.  I'm considering changing dentists.... Kingsfold (talk) 15:48, 30 March 2010 (UTC)


 * I had toothache that was relieved by swirling water. It was due to a large cavity between my teeth - due to moving town I had not had regular check-ups for some time - my fault for not signing up with another dentist and not the NHS's. Coincidence - it was the last tooth on my upper left as well! Luckily it was just a wisdom tooth, so it was removed without any cosmetic or functional effects. Am I right in guessing from the OP saying that they could not afford treatment that OP is from the USA? (Why dont Americans revolt and demand free health care from their government?) 78.146.180.118 (talk) 20:17, 30 March 2010 (UTC)
 * Did you read the post? He does have an appointment to get it fixed, and presumably can afford treatment. But his regular dentist is backed up, so he has to wait a little while (or find another dentist, which he has not yet tried to do). &mdash;ShadowRanger (talk 20:22, 30 March 2010 (UTC)


 * But I though this kind of delay was what Americans imagined happened with the UK NHS, and not what is supposed to happen in the US? I mean, May and he's in pain! Over a month away! This side of the Atlantic you'd probably get it done as an emergency appointment the same day, or the next day at most. And if you had a low income it would be completely free, otherwise a nominal charge of a few pounds. 78.146.180.118 (talk) 20:26, 30 March 2010 (UTC)


 * Trying... to... restrain... British... Teeth... joke... Googlemeister (talk) 20:36, 30 March 2010 (UTC)


 * If British people have stereotypically crummy teeth, how come there are so many Oscar winning British actors? 78.146.180.118 (talk) 20:41, 30 March 2010 (UTC)


 * Americans can't resist the British accent. When they speak, we swoon and forget the teeth. ;-) &mdash;ShadowRanger (talk 20:45, 30 March 2010 (UTC)


 * I thought we Americans liked British accents because they make us sound so masculine, by comparison. :-) StuRat (talk) 17:23, 2 April 2010 (UTC)

I feared that this discussion would eventually turn into a back-and-forth about Nationalized Health Care. I'm not convinced that I'd get in any sooner were the United States to adopt a system like the one in the UK. If anything, I'd think it would be *more* difficult to get in to secure an appointment.... The other chapter of the story (that I didn't particularly care to get into on the Science reference desk) is that it was the crown that broke-- not my tooth. As such, I am only being charged 25% of the usual cost of a crown. (I didn't realize this until the hygenist notified me of this at a recent checkup.) So, I can stick it out for a month and maybe get in sooner on "standby;" or I can go to the hassle of changing dentists, probably not get in any sooner, AND pay full price. My vote: stick it out with my usual, albeit busy, dentist. (Unfortunately for my tooth.) Kingsfold (talk) 02:09, 31 March 2010 (UTC)


 * As described above, you'd probably get emergency treatment for pain the same day in the UK. So you would definately have quicker treatment. I'm shocked that you consider such very bad treatment and totally unacceptable delay, not to mention not getting treatment merely because you cannot afford it, normal. Why don't Americans have a second Revolution against getting such third-world health care? If the same thing happened in the UK the dentists would probably get sacked. 78.147.25.63 (talk) 16:34, 31 March 2010 (UTC)
 * It's a weird part of the U.S. view of health care. For some reason, historically dentistry wasn't considered health care. Same goes for "basic" vision and hearing problems; one of my mostly deaf relatives pays about $5000 out of pocket every few years when he needs a new hearing aid. So a lot of people who have "health care" don't actually have dental coverage. If a dental problem spreads (blood infection or the like), and you lack insurance and the ability to pay, you can visit an ER for treatment. The new health care reform bill takes some steps to address this, particularly in the case of children (though most of the reforms won't kick in until 2014). It's bad, but at least it is getting better. Single-payer would probably have been more effective at controlling costs and better at achieving universal coverage, but it was politically impossible. &mdash;ShadowRanger (talk 19:34, 31 March 2010 (UTC)
 * People in the US don't revolt about inadequate health care because so many of us are completely deluded about US's health care being the best in the world. Afterall this is America! Dauto (talk) 07:12, 1 April 2010 (UTC)

Cancer disease
Can a 13 year old be affected by cancer and if yes, which are its first symptoms? —Preceding unsigned comment added by Rox asmita (talk • contribs) 15:21, 30 March 2010 (UTC)


 * Yes, and being cancer, there are a nearly infinite number of possible symptoms. That said, we cannot give medical advice at this reference desk. You should contact a doctor for specific advice. &mdash;ShadowRanger (talk 15:24, 30 March 2010 (UTC)


 * See cancer for a description of the many different types. StuRat (talk) 15:36, 30 March 2010 (UTC)
 * The Teenage Cancer Trust article has some statistics but they seem to be unsourced. Do we have a better article somewhere? Rmhermen (talk) 15:43, 30 March 2010 (UTC)
 * Here is a PDF of Canadian cancer statistics for 2008. It also has a special section of Childhood (Ages 0-14) cancers beginning on page 60. You can use that to look for articles on specific cancer types. -- Flyguy649 talk 15:50, 30 March 2010 (UTC)


 * Cancer being cancer, it will probably manifest with similar symptoms as it does in adults; however, in children, some cancers may manifest differently, and there are a whole slew of cancers that occur mostly during childhood. It depends on the cancer. 70.179.127.14 (talk) 20:38, 30 March 2010 (UTC)
 * Some cancers, such as leukaemia, have greater prevelence in children and teenagers than other forms (such as carcinomas and melanomas). You may be interested to read this link. Symptoms for cancer will depend highly upon where the cancer is and at what stage it's at. Please seek medical advice if you are concerned about specific, personal health matter. Regards, --— Cyclonenim | Chat 00:59, 31 March 2010 (UTC)

number of sites
If Iran packed every square inch of land under its control with nuclear sites is there a limit in the amount of electricity it could sell to other countries without fear of invasion if Iran cut them off? 71.100.3.207 (talk) 17:24, 30 March 2010 (UTC)


 * You're going to have to clarify what you mean. How would Iran's nuclear sites affect its ability to sell electricity (do you mean nuclear power plants, as opposed to nuclear weapons or nuclear refining sites?), and how would selling electricity have anything to do with fear of invasion? Another country could theoretically become dependent on foreign electrical power, but they usually maintain enough homegrown generation capacity to keep their military functional. &mdash;ShadowRanger (talk 17:43, 30 March 2010 (UTC)
 * Lets see... after a certain distance the cost of transmission might become too high for electricity to sell. with that restriction what is the limit of power Iran could reasonably expect to sell, use or store without unreasonable risk of invasion by others to remedy an energy crisis?. 71.100.3.207 (talk) 18:16, 30 March 2010 (UTC)
 * The range for transmission would likely not be much of an issue. You do lose power over long distances, but given that there are serious (if unlikely to be fulfilled) proposals to use solar power in the American Southwest to power the whole country, it's clear that the losses aren't enough to make it completely impractical. Answering the question of how much power is "too" much, in the sense of attracting the attention of foreign powers looking to remedy an energy crisis, that's asking us to predict the future and human political psychology all in one. According to this chart of power generation capabilities, the U.S. produces as much power as China, Japan and Russia put together. Iran is producing roughly 10% of what Japan uses, so unless you assume that Iran's neighbors are more likely to launch an invasion than Japan's neighbors, Iran should be able to multiply it's power generation capabilities by 10x without risk. &mdash;ShadowRanger (talk 18:43, 30 March 2010 (UTC)


 * Land isn't the limiting factor. I would expect them to run out of nuclear fuel long before they ran out of space. --Tango (talk) 17:50, 30 March 2010 (UTC)
 * Aren't they building breeder reactors? 71.100.3.207 (talk) —Preceding undated comment added 18:09, 30 March 2010 (UTC).
 * Breeder reactors aren't magic. They can turn certain thorium isotopes into usable reaction material, and they can use the initial uranium fuel more thoroughly, but they're still limited by the need for fairly uncommon materials. &mdash;ShadowRanger (talk 18:43, 30 March 2010 (UTC)
 * The transmission cost for electric power is mainly the one-time investment cost in infrastructure i.e. lines, pylons, switchgear and transformer stations. The selling price for electricity varies with market demand, which varies with season. Availability of cheap and reliable nuclear power will tend to stifle use of other forms of power, particularly if it is perceived as less polluting. There is no economical way to store electric power so it makes more sense to run nuclear stations at partial capacity and adjust output to suit demand. Neighbouring countries that might invade Iran for reasons that have nothing to do with electric power would seem less likely to do so if they depended on Iran for cheap power. But the OP makes a big assumption that the world powers will allow Iran to develop nuclear capabilities unchecked. Cuddlyable3 (talk) 19:17, 30 March 2010 (UTC)
 * And the capital costs of such an endeavor are probably beyond them and everyone else. Nuclear power plants cost a non-trivial amount to build and take a long time to pay for themselves. --Mr.98 (talk) 01:01, 1 April 2010 (UTC)


 * Some things are clearly beyond anyone's (and the whole world's) capacity. Iran cannot acquire such potential overnight or in a year or in ten years. There's nothing to discuss here. They can build the system organically, one radius at a time, but it's a whole different scenario. NVO (talk) 19:21, 30 March 2010 (UTC)

Putting it another way... what are the primary limiting factors in the number of sites Iran should build to produce only fuel for the purpose of generating electricity (to sell, use or store - zero degree inductors) to minimize risk of invasion to stop production of WMD? ShadowRange says 10 times its current electricity generating capacity which seems well beyond the amount the world would be comfortable with in absence of direct International supervision.71.100.3.207 (talk) 20:53, 30 March 2010 (UTC)


 * Ah, see now you're talking about something different. Your original question, at least as I interpreted it, was what level of power generation would make its neighbors get greedy enough to risk war. That said, the calculus involved in what would trigger international sanctions, or even a U.N. sponsored invasion is at least as complicated; the neighboring states may be more volatile, and therefore unpredictable, but worldwide politics is at least as complicated, and much harder to read. What would it take for Russia or China to not veto a use of force resolution? If that doesn't happen, what would it take for another country to become sufficiently worried as to attack without U.N. approval? Neither question can be easily answered. The Iraq invasion was launched with little evidence; with Iran, we *know* they are further along than Iraq had been in the last 15 years, but the U.S. hasn't invaded. Some reticence after the Iraq debacle is expected, but where the new line is drawn is not clear. &mdash;ShadowRanger (talk 21:00, 30 March 2010 (UTC)
 * Misunderstanding can often require that a question be rephrased. To be more precise let me rephrase by asking then is there any correlation between number of sites and Iran's power generation capability versus Iran's WMD capability and if so what number of site would trigger world wide consternation or would that be triggered only by Iran's refusal in absence of limiting the number of sites or WMD correlated activity to guarantee the security of Israel from intent of use it has already expressed? 71.100.3.207 (talk) 01:39, 31 March 2010 (UTC)
 * WMD production capabilities aren't directly correlated to power generation. As noted in the article on Breeder reactors, a single breeder reactor can consume its initial fuel (and in fact produce fuel from other elements, such as thorium-232) with far greater efficiency than the typical non-breeder light water reactor, but they also produce nuclear weapon fuel (specifically plutonium) in significant quantities as a consequence of operation. Therefore, the most efficient means of producing power is also the one that gives the international community the most sleepless nights. Failing to reprocess the fuel is a waste, which Iran understandably wants to avoid. Proposals to ship the partially used fuel to Russia for reprocessing have not progressed (last I checked). The point is, trying to infer Iran's nuclear weapons capability from their power production isn't possible unless you know their power generation technique. And it still won't tell you if they have nuclear weapon capabilities, because you can breed plutonium and enrich uranium without hooking it up to the power grid. After all, if the whole base is a secret, it's handy to have it off the main grid, so an in-house generator/breeder is quite handy. &mdash;ShadowRanger (talk 19:26, 31 March 2010 (UTC)
 * Thorium reactors produce Uranium-233, which is similar in its properties to plutonium (fissile, high background neutron rate, difficult to handle), but not quite the same thing. Just a small caveat. --Mr.98 (talk) 01:01, 1 April 2010 (UTC)
 * I'm not sure there's any way to gauge in real terms your proposal. What you have proposed is not an economic question but a political one. There is unlikely to be any price that Iran can put on 3% enriched uranium that would make it significantly more politically palatable. Or put another way, the reason people don't invade the Netherlands is not because they produce a lot of the world's nuclear fuel. The economic output is simply not all that important in the vast scheme of their economy, or in the world's political balance. If an invasion will happen, it won't be because the economic aspects weren't important enough; if an invasion doesn't happen, it won't be because the economics of uranium was cheap. --Mr.98 (talk) 01:01, 1 April 2010 (UTC)

calorie consumption
Is there a formula to calculate the number of food calories needed to fulfill both the BMR requirements and number of calories needed to ride a bicycle different distances and at different speeds? 71.100.3.207 (talk) 17:39, 30 March 2010 (UTC)


 * There are a million different calorie calculators online, just Google (or Bing) for them. This is one. They're all going to have a very limited amount of accuracy, due to the fairly substantial differences in metabolic rates between people. &mdash;ShadowRanger (talk 17:47, 30 March 2010 (UTC)


 * ...err, that's why I'm looking for a formula not a calculator. 71.100.3.207 (talk) 18:02, 30 March 2010 (UTC)


 * You'd have the same problem with a formula. Unless you spend a lot of time to determine your particular basal metabolic rate, you will just have to settle for an average, which won't be accurate enough to be of much value, unless you just happen to be a throughly average person.  See basal_metabolic_rate.  Also, the air temperature, humidity, hilliness of the path, clothes you wear, whether it's sunny or cloudy, etc., would all have an effect on the calories you use biking.  But, if you want to ignore all that, here's a site which has the formula to calculate calories burnt bicycling: . StuRat (talk) 18:14, 30 March 2010 (UTC)


 * The ability to include and change the values of major factors is what I'm looking for...  —Preceding unsigned comment added by 71.100.3.207 (talk) 18:23, 30 March 2010 (UTC)


 * English BMR Formula
 * Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
 * Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )
 * Metric BMR Formula
 * Women: BMR = 655 + ( 9.6 x weight in kilos ) + ( 1.8 x height in cm ) - ( 4.7 x age in years )
 * Men: BMR = 66 + ( 13.7 x weight in kilos ) + ( 5 x height in cm ) - ( 6.8 x age in years )
 * 71.100.3.207 (talk) 18:19, 30 March 2010 (UTC)
 * Pedantic point - if that forumula was truely English, it would use stones and pounds. 78.146.180.118 (talk) 20:38, 30 March 2010 (UTC)
 * And all those numbers apply to the average person. And virtually no one is actually average in every way. &mdash;ShadowRanger (talk 18:34, 30 March 2010 (UTC)


 * I'm not looking for a formula to satisfy your desire or lack thereof for it. 71.100.3.207 (talk) 18:53, 30 March 2010 (UTC)


 * Not sure if this helps but the article on Harris-Benedict equation (which are the equations above) has a section on adjusting the calculated BMR for people who exercise. Zain Ebrahim (talk) 07:59, 31 March 2010 (UTC)
 * Yes, that is more or less the function I'm looking for. However, the exact formulas I'm looking for will show calorie consumption based on: miles and duration, weight of bicycle and rider, bicycle resistance (due to condition or need for repair), wind and hill resistance and urban versus rural traffic conditions. I'm open to all other significant conditions that might effect calorie consumption to a great extent. 71.100.3.207 (talk) 17:45, 31 March 2010 (UTC)
 * A mathematical formula with all of those variables (and some you might have neglected such as average altitude, riders clothing, tire pressure etc) would probably be too complicated for the average Joe to use. Also, it would surprise me if such a formula would still be all that accurate, since person A and person B could both do the same task with all of the quantifiable variables the same, but the non-quantifiable variables will give different results.  If person A was in great shape, and person B was in poor shape, all else being equal, person B would burn more calories because being in better shape also means using energy more efficiently, but how do you apply a number for that into your equation?  Googlemeister (talk) 19:22, 31 March 2010 (UTC)


 * Formulas are generally created to replace searching tables of data. Some table lockup routines merely give you the closest answer. For instance a table for age based on height and weight and gender will start by including ages for only the selected gender. Next from the previous list only ages with weights equal or near to the weight entered will be retained, Next only ages with heights that are equal or close will be retained from the previous list. So long as you end up with more than one age you can keep adding variables like hair color to eliminate ages you don't need. In this case we are talking about calories and not age.  71.100.3.207 (talk) 19:24, 2 April 2010 (UTC)

Broom handle manufacture
How are the modern wooden cylindrical broom handles made?--79.76.190.44 (talk) 20:30, 30 March 2010 (UTC)


 * Originally with a lathe, though it has likely been heavily adapted for mass production. &mdash;ShadowRanger (talk 20:50, 30 March 2010 (UTC)
 * Information on using a lathe in woodworking can be found in this article on woodturning. &mdash;ShadowRanger (talk 20:52, 30 March 2010 (UTC)


 * If you look carefully at your broom handle (as I have at mine) you will notice no evidence of lathe work (grooves) whatsoever!--79.76.190.44 (talk) 20:58, 30 March 2010 (UTC)


 * Presumably a sufficiently precise set of machinery would leave minimal traces. Finishing the job with an automated round of sanding would remove what remains. &mdash;ShadowRanger (talk 21:04, 30 March 2010 (UTC)


 * From Google search, most now appear to be made in China. They do not include a description of the manufacturing process. The wood is variously listed as birch, pine, fir, or poplar. Strangely, wood dowels, which are basically the same thing, are sometimes made in the U.S.. A broomstick or dowel could be made on a lathe from a piece square in cross section sawed out of a larger seasoned timber, as suggested by . Rather than placing a dowel in a lathe and spinning it around its axis, it could also be made by feeding it lengthwise through a milling machine in which cutters of half-circle profile form it from above and below. This should leave some longitudinal ridges or grooves, in contrast to lathe manufacture, which should leave annular ridges or grooves. Edison (talk) 21:07, 30 March 2010 (UTC)
 * (ec)In my (admittedly limited) experience, they rarely have grooves at all. So they could be using either technique, then sanding it down to the perfectly smooth cylinder. Same results either way. Old school operations presumably use whichever technique they were using originally (since upgrading machinery costs money up front), while modern operations use whichever technique wastes less wood (since wood costs money over time, and a new operation may as well go for the efficient approach). Per Sean's comment below, the rate of mishaps associated with a particular technique may also guide the decision. Lathe clearly indicates that it is used for tool handles of all kinds, so presumably *some* broomsticks have been made using that technique. &mdash;ShadowRanger (talk 21:21, 30 March 2010 (UTC)


 * Here's a description of making a dowel with a router. I find it hard to imagine lathing something as long and thin as a broomstick without it flying off, but I guess it's possible.  --Sean 21:16, 30 March 2010 (UTC)


 * Google Book search does not provide a view of the text other than this snippet: Wood working digest, Volume 65‎ - Page 59, Hitchcock Publishing Company, Wheaton, Ill - Business & Economics - 1963: "DAH, British Guiana Broom Stick Machine We have a prospect for semi-automatic equipment for high speed production (turning and sanding) of broom sticks, ..." So some modern ones were made by turning. In an 1895 book there is a description of a lathe machine with a hollow mandrel and internal curtters which rounded the broomstick as it passed through the machine . As ShadowRangerRIT noted a piece of wood as long and thin as a broomstick would not be easy to turn at high speed. Cutters could spiral around the piece of wood, which might leave spiral groves. Something like a pencil sharpener, but with cutters that make a cylinder rather than a conical point at the end. Sanding could smooth away the ridges. Edison (talk) 22:04, 30 March 2010 (UTC)


 * My broomstick does not appear to have been sanded (ie grain is not filled with sawdust) neither does it it have longitudinal grooves: so hows it done?--79.76.190.44 (talk) 22:33, 30 March 2010 (UTC)


 * Sawdust can be removed by a number of methods, from simply falling out during the course of transport to active washing to remove the dust. It's all speculation though; unless you visit (or contact) one of the Chinese broom manufacturers you probably won't know for sure. &mdash;ShadowRanger (talk 19:13, 31 March 2010 (UTC)