Wikipedia:Reference desk/Archives/Science/2008 July 16

= July 16 =

astronomy
our solar system is laid out like a plate is it likely that the planets are spin offs from our sun at its birth

dose the sun rotate ?

what is the cause of gravity?

why do the planets rotate anti clockwise? Why do planets revolve around the Sun anti-clockwise?

what is the force that makes the planets travel along the same path around the sun with the same speed all the time ?

do all the stars which are suns all have planets?

where in the milky way is our solar system located?

these questions have been something i have been wondering about for sometime.

many thanks i hope someone can answer them.

Szeretetelchak (talk) 02:08, 16 July 2008 (UTC)


 * Wikipedia is more than a reference desk. It is an encyclopedia.  Try reading some of the following:
 * Formation and evolution of the Solar System
 * Gravity
 * Retrograde and direct motion
 * Orbit
 * Star
 * Solar System
 * Milky Way
 * If you make even the feeblest attempt at finding these answers yourself, others will be happy to fill in any gaps in the information already easily available throughout Wikipedia. -- k a i n a w &trade; 03:22, 16 July 2008 (UTC)
 * And extrasolar planet. --Tango (talk) 04:18, 16 July 2008 (UTC)

I'll bite. Quick and simple laymans answers. For more detailed answers, checkout the relevant articles.

The planets were formed from the accretion disk that surrounded the proto-star that eventually became our sun.

Yes.

General Relativity explains gravity. Any object that has mass, will make a dent in space-time. The larger the mass, the greater the dent. The greater the dent, the greater the force of gravity.

Because of conservation of angular momentum. When the solar system was formed, the accretion disk was spinning in that direction. Venus spins the other way because a massive asteroid collided with it, and changed its rotation direction.

Momentum and inertia. See also Newton's First Law of Motion.

Not all stars have planets.

On the edge.

Hope that helps. ScienceApe (talk) 06:05, 16 July 2008 (UTC)


 * Szeretetelchak, your curiosity is to be commended, but your questions betray some hidden assumptions, which you need to examine more closely.
 * "Our solar system is laid out like a plate ..." - is it really ? Although the orbits of the major planets lie approximately in the same plane, there is much more to the solar system than the planets. For example, the outer Oort cloud, which contains contain several trillion individual comet nuclei, is spherical, not "plate shaped".
 * "What is the cause of gravity ?" - simple answer is mass, but this begs the question "What is the cause of mass". Answer that one, and you are in the running for a Nobel prize (unless Peter Higgs beats you to it).
 * "Why do the planets rotate anti clockwise ?" - there are two misconceptions here: (1) the sense of rotation depends on where you are looking from and (2) even looking from one direction, not all of the planets do rotate in the same sense. But you may be confusing rotation with orbital revolution.
 * "What is the force that makes the planets travel along the same path around the sun with the same speed all the time ?" - a planet does not travel with the same speed all the time. Aristotle believed this, but he was wrong - see Kepler's laws of planetary motion, especially the second law. And a planet does not even retrace exactly the same orbit relative to the sun, due to orbital precession.
 * "Where in the milky way is our solar system located ?" - the solar system is not located at a single place in the Milky Way - it is travelling at a speed of about 220 km/s relative to the Galactic Centre, and it has complete about 20 orbits around the Milky Way since it was formed. It is more meaningful to think about the characteristics of the solar system's orbit within the Milky Way.
 * Hope this helps you. Gandalf61 (talk) 14:36, 16 July 2008 (UTC)


 * Re: clockwise. Consider a sundial.  Clocks spin anti-planetwise.  :-)  Saintrain (talk) 23:53, 17 July 2008 (UTC)

More odd bird behaviour on YouTube...
Anyone know what's happening here? The raptors don't actually seem to be seriously trying to kill each other (with that beak, it wouldn't take long to inflict a fatal wound) - one just seems intent on pinning the other to the ground and keeping him/her there. --Kurt Shaped Box (talk) 06:56, 16 July 2008 (UTC)


 * Perhaps it's a dominance display (what, no article ?). StuRat (talk) 14:32, 16 July 2008 (UTC)


 * Or perhaps rough play between siblings? Watching it again, those birds do look quite young and downy... --Kurt Shaped Box (talk) 17:25, 16 July 2008 (UTC)


 * Take note that most animals do not try to kill other members of their own species. Animals that happily and routinely kill other species are usually much more likely to intimidate or submit when among their own. (Humans are often an exception to this.) --140.247.240.177 (talk) 20:02, 16 July 2008 (UTC)


 * Less of an exception than you'd think. A large part of military basic training is about training soldiers to be able to kill. --Carnildo (talk) 23:04, 16 July 2008 (UTC)


 * Outside of military/politically-motivated/gang/revenge situations (what I would refer to as 'violence with purpose'), the vast majority of humans scraps and scuffles have a non-lethal conclusion. Take your typical post-bar-closing scraps. Statistically, very few result in one human beating another human to death with his/her bare hands (obviously, all bets are off when guns and knives come into play). No, the battle seems to end when one combatant is a bloody, broken mess and unable to continue. It takes more will than most people posses to continue to beat and kick a man once he stops moving... --Kurt Shaped Box (talk) 23:59, 16 July 2008 (UTC)

Size of the Internet
What's the size of the Internet? Number of gigabytes sent/stored, number of computers used, number of human users, amount of power consumed daily, etc? —Preceding unsigned comment added by 24.7.54.224 (talk) 08:43, 16 July 2008 (UTC)


 * An interesting question, I expect there is not going to be a precise answer but I'm sure others at this desk will be able to come up with something. In terms of human users, the article Demographics of the Internet may be of interest to you. Jdrewitt (talk) 09:28, 16 July 2008 (UTC)


 * Google is said to process over 20 petabytes (20 million gigabytes) data per day. Obviously, this doesn't really help a lot in getting stats about the internet as a whole. Still darn impressive, though. -- Aeluwas (talk) 11:07, 16 July 2008 (UTC)


 * The problem is that the internet is a system, not a thing. Every computer connected to the internet is, for that time, part of the internet.  Computers connect/disconnect all the time.  This question is similar to asking "How many people are in McDonalds?"  It cannot be answered because the number of people change every second of every day. --  k a i n a w &trade; 11:47, 16 July 2008 (UTC)


 * But you could do a reasonable Fermi estimate to get in the right order of magnitude. Just because something has regular fluctuations doesn't mean it isn't mostly stable to a certain degree of accuracy. The population changes every day but we still have a census that is meaningful. --98.217.8.46 (talk) 14:06, 16 July 2008 (UTC)


 * One of the differences here (and in the McDonalds case) is that the change is likely not close to being constant. Americans still make up a big percentage of internet users despite rises in China etc. And people in developed countries probably have bigger hard drives and more data in general then those in the developing world, probably more power hungry computers (although hard to say given the recent move towards energy efficiecy). Therefore, at peaks times for American connection your going to get a large increase in the overall in the data content. I suspect weekends have even more (on the other hand, businesses are more likely to have their computers offline on the weekends and at night time). Similarly in McDonalds, people don't tend to eat at all hours of the day. And I suspect Americans make up a big percentage of McDonalds customers. The number of people in McDonalds in the world, at say 5-8 p.m. (in the various timezones) in the US is going to quite a bit higher then at 3 a.m. in the US. Again weekends and I suspect public holidays are going to be even higher. While I have no specific evidence, my gut feeling is both the data and particularly the number of people of McDonalds at any given time in a day can vary by a large percentage (say 95%+ for McDonalds) and obviously by even more when we consider over the various days of a year. On the other hand, I suspect population figures in any given country under normal times don't tend to vary by even 1% (for the US this is over 3 million) ignoring overall growth/decline. It would be better in both cases (McDonalds and internet) to think in terms of averages over a time interval (say average per/day). (Another issue of course is what is a computer? Is a Wii? A mobile phone? A router? A fridge? And if I have a P2P app in the background while playing a non online game am I using the internet? What about if I'm occasionally messaging a friend online?) Nil Einne (talk) 17:21, 16 July 2008 (UTC)


 * I think Nil has it exactly right that the internet as we conceive it has to be looked at as a system in flux. I suppose there's some way of estimating the amount of data stored on all the servers, but it would be a poor estimate for a whole host of reasons. To name only one of the most obvious, a media file that no one has uploaded or downloaded in months might count for just as much as some hot video on YouTube seen by millions a day. I disagree, however, that we have to work at defining a computer; all we need to measure is traffic; I don't think it really matters what device is doing the uploading or downloading. If we stick with the traffic definition, Nil's P2P app would simply contribute to the download or upload quantity. Matt Deres (talk) 18:42, 16 July 2008 (UTC)

JITENDRA ARYA QUESTION ABOUT DISEASE
CAN ANYBODY TELL ME MY AILMENT Question removed. See below. —Preceding unsigned comment added by 59.98.65.51 (talk) 09:57, 16 July 2008 (UTC)
 * I'm sorry, we really can't. You should see a qualified medical professional. AlmostReadytoFly (talk) 10:56, 16 July 2008 (UTC)


 * Caps lock disorder?--Shantavira|feed me 11:59, 16 July 2008 (UTC)


 * Two things are the problem here. (a) We don't know which disease you have, so no. (b) We couldn't even if we did—Wikipedia does not give medical advice. Please see your physician. — CycloneNimrod Talk? 15:33, 16 July 2008 (UTC)


 * Would it be medical advice to note that in the removed question the mentioned previous, now no longer effective prescription would be correctly spelled as Cetirizine? 93.132.131.176 (talk) 22:24, 16 July 2008 (UTC)


 * If it is asking for any advice on treatment, diagnosis or signs and symptoms (the latter is my opinion) then it is a request for medical advice. The specifics, such as the effects of Citirizine, are irrelevant :) — CycloneNimrod Talk? 06:36, 17 July 2008 (UTC)

An inter-fabric-of-cosmos-wormhole/grayhole
Today while I was exercising I thought that in a supermassive blackhole, the fabric of cosmos might break, and the matter will just swarm to the other side of the fabric of cosmos, and warp timespace oppositely by warping on the opposite side of the fabric of cosmos. As the warp builds, it might create a black hole on the other side, which is equivalent to a white hole on our side though no mass is on our side of the fabric of cosmos the place of black hole there(a zero mass black hole(zero mass black holes also act like white holes)). But, due to the hole created by the supermassive blackhole mentioned in the first line will make the matter swarm to the other side and again and again and again... But another thought is that only half of the matter will swarm to the other side, but the fabric of cosmos cannot warp due to having equal mass on both sides and either stabilizing the warp or the fabric of cosmos spiting in half, and having created a new universe with the new half. Still, another thought lead me to thinking the hole will create a big bang on the other side with the matter spreading out, like the big bang, and matter continuely falling over the other side and after half of the matter falls to the other side, pressure will slow down the transfer, but the trend remains. After all the matter flows there, it might ignite a new big bang on the opposite side once again. Or perhaps the matter will equalize and.. the possibilities are infinite. Could such phenomena happen? please reply!!! —Preceding unsigned comment added by Superwj5 (talk • contribs) 12:21, 16 July 2008 (UTC)


 * Please see black hole and white hole. This is a reference desk, not a "tell me if my most recent theory is valid" desk. You appear to be in need of a discussion forum.  There are thousands (if not millions) of them on the Internet.  This is not one. --  k a i n a w &trade; 12:35, 16 July 2008 (UTC)


 * It sounds like you're thinking of the universe as a rubber sheet being warped by massive objects, which is a good analogy up to a point, but isn't entirely accurate. There isn't really an "other side" to the universe where massive objects would push the universe in the other direction, at least not in a standard interpretation of general relativity (M-theory might have something along those lines, I've never studied it). --Tango (talk) 22:17, 16 July 2008 (UTC)

Energy Drinks (E.g. Lucozade)
I have fallen for the marketing tactics - i've bought myself an energy-drink in anticipation of 'cup finals' night at my local football thing tonight. Putting to one side the question of whether energy-drinks produce any increase amount of energy/stamina does anybody know how long before said game is 'optimum' for drinking said energy drink? E.g. Before I play I use my inhaler about 30 mins before (as directed by my asthma nurse) and that tends to mean I don't need to use it during the game. Should I drink my drink 10 mins before, 30 mins, an hour, 2 hours? Granted I don't believe these have a 'major' impact but given that i've bought the drink already I might as well try drink it at the best time possible.

I ask because i'm thinking whatever is in the drink (sugar and chemicals no doubt) needs time to 'work' or be 'digested' or something. Any help greatly appreciated. 194.221.133.226 (talk) 13:17, 16 July 2008 (UTC)


 * They are pretty much sugar-water, with maybe some caffeine tossed in. Since sugar is rapidly digested, I'd drink it right before.  There is also the "sugar crash" to consider, which will cause you to rapidly lose energy as soon as the sugar rush is countered by your own insulin production.  Starches are usually suggested to be eaten with sugar, since they are digested a bit slower, and then hold blood sugar steady when it would otherwise crash.  Protein and then fats are good for even longer terms. StuRat (talk) 14:13, 16 July 2008 (UTC)


 * In most energy drinks, it is not caffeine that provides energy. Caffeine simply helps to bypass your body's feeling of fatigue and helps keep you awake. That is of course a benefit to someone who needs to stay up late working. The energy that you need to be more active is provided by, as StuRat said, sugar (ususally glucose or dextrose, I think it's the former in Lucozade). This is digested very early on and doesn't go through the entire small intestine, as you would expect larger proteins and lipids to do. Energy drinks also contain taurine which helps to do a lot of things but in energy drinks it's particularly helpful due to it's effects of countering osmotic shock (good if you're an athlete) and it's role of being a surfactant of the cholic acid conjugate.


 * Basically, I recommend you'd drink your energy drink about 10-15 minutes before the game. This should mean it's starting to be digested roughly as the game starts and should give you a pretty optimum time with a 'sugar high' before the crash. — CycloneNimrod Talk? 15:31, 16 July 2008 (UTC)


 * When I suggested drinking it right before the event, I was assuming the athlete would have sufficient energy at the start, and would only need the energy burst later on once they burned off that initial energy. StuRat (talk) 23:07, 20 July 2008 (UTC)


 * It also ensures that you're on the loo just when the quarterback makes that fantastic throw right to the runner in the end zone while the cheerleaders flash the other team. Or you keep the empty bottle handy ;-). --Stephan Schulz (talk) 00:19, 17 July 2008 (UTC)


 * And then the wicketkeeper scores a slamdunk? 79.66.90.252 (talk) 13:18, 17 July 2008 (UTC)


 * Ooops...this may be telling about my mindset! I assumed, of course, that the original poster tried to keep awake on the couch while watching the game (in which case the empty bottle can be used as an emergency solution in a private situation), not actually playing in it. If you are actually playing the game, just stick to a fruit juice/water combo. The energy drink is great for after-the-game. Most energy drinks are great at masking the taste of Vodka... --Stephan Schulz (talk) 13:03, 21 July 2008 (UTC)

The discrete movements of chickens
Why do birds move their heads in discrete amounts rather than in smooth and continuous motions as mammals do? They look almost like they're in stop-motion. I can explain further if you don't know what I mean. --Sean 13:22, 16 July 2008 (UTC)


 * I believe they have optical processing in the brain that enables them to easily spot moving objects against a still background (we have this ability, too). This works better if the head is held still to prevent apparent background motion.  So, they hold their head still for a bit then quickly move it to the new position for another "snapshot", while walking.  This might bring up the question "why don't humans do this ?".  Our heads and brains are too big, such that repeated, quick, jerky motions like this would make us dizzy and/or cause us brain injury (although we might hold our head still while trying to spot a small object moving in the distance).  So, apparently there is at least one advantage to having a bird brain. StuRat (talk) 13:43, 16 July 2008 (UTC)


 * You may want to read the saccade article. My guess is that since the eye motion amplitude in birds is somewhat limited (or sometimes very limited, as in barn owl), rapid head rotations are actually saccades.  --Dr Dima (talk) 13:52, 16 July 2008 (UTC)


 * There are four reasons:
 * 1. Balance
 * 2. To achieve depth perception through their (virtually) monocular vision
 * 3. To read a stable image from their sub-standard eyes
 * 4. Because it feels good.
 * So sayeth The Straight Dope.  Plasticup  T / C  14:18, 16 July 2008 (UTC)


 * For "why don't humans do it"... We have depth perception without jerking our heads from side to side. If you lost one of your eyes, you may jerk side to side more to get a sense of depth - and likely become rather accustomed to overlaying something you just saw onto something you currently see - just like a chicken. --  k a i n a w &trade; 14:53, 16 July 2008 (UTC)

Most birds eyes are located on the sides of their heads, permitting them to see over 300 degrees without moving. However, the disadvantage of this positioning is that movement produces motion parallax errors - objects nearby appear to move faster than objects further away. To preserve visual acuity, a bird will lock its head in position whilst moving its body beneath it. It will then move its head to the next 'lock' position, which it again holds. In this way the parallax effects are minimized. Incidentally, the combined action of "head locking" with walking gives certain birds (such as pigeons) the characteristic nodding appearance. See here and here for in depth studies. Rockpock e  t  20:33, 26 October 2007 (UTC)


 * So, why don't all birds do this? Gulls (just to use an example I'm familiar with) have eyes placed at the side, yet they walk with a straight neck. --Kurt Shaped Box (talk) 22:56, 16 July 2008 (UTC)
 * Good question. According to the second source, "This behaviour occurs in at least 8 of the 27 orders of birds including relatively common species such as pigeons, doves, hens, starlings, pheasants, coots, rails, sand-pipers, phallaropes, parrots, magpies and quail." So why not the others? Well, it might be something to do with the neural architecture of the visual system, or it could be do with ecology, or both. It appears to me that most of those listed above would have predators and it might in in their interest to have an ability to watch out for them with good visual acuity. Bird without natural predators may not have the same requirement. This is purely speculative, though. Rockpock  e  t  18:48, 17 July 2008 (UTC)


 * Just for the record, Budgerigars don't head-bob when they walk/run either. --Kurt Shaped Box (talk) 23:20, 17 July 2008 (UTC)

Calibration
What is the difference between Calibration and Standardisation? —Preceding unsigned comment added by Jsummi (talk • contribs) 14:15, 16 July 2008 (UTC)


 * Have you considered reading the very first sentence of calibration and standardization? -- k a i n a w &trade; 14:50, 16 July 2008 (UTC)


 * Agreed, but let's not tare the question asker a new one, please. StuRat (talk) 22:55, 20 July 2008 (UTC)

Unknown plant
Can anyone tell me what this plant is? J.delanoy gabs adds 17:39, 16 July 2008 (UTC)


 * Where? -- LarryMac  | Talk  17:49, 16 July 2008 (UTC)
 * In New York State, but not near NYC. J.delanoy gabs adds  17:53, 16 July 2008 (UTC)

its a weed —Preceding unsigned comment added by 86.158.32.65 (talk) 22:25, 16 July 2008 (UTC)


 * Looks like White Sweet Clover, Melilotus alba (or M. albus). Take a look at the images at this link . Here's our article Melilotus albus.--Eriastrum (talk) 00:14, 17 July 2008 (UTC)
 * That is definitely it. Thanks for your help! J.delanoy gabs adds  14:11, 17 July 2008 (UTC)

astrophysics
i have searched for information on ABSOULUTE POSITION. that is, to be stationary (say, outside the universe) I would like to know (1) If this is possible, and (2) What would be observed' —Preceding unsigned comment added by 86.158.32.65 (talk) 22:13, 16 July 2008 (UTC)
 * I'm no astrophysicist but i'm pretty sure we don't know anything about what is outside the universe, certainly not if it's possible to go there or not. — CycloneNimrod Talk? 22:18, 16 July 2008 (UTC)


 * See absolute time and space. Things like "absolute position" appear to not exist. PrimeHunter (talk) 23:45, 16 July 2008 (UTC)


 * By definition, the universe incorporates everything that exists. If there are other universes with their own scientific laws, constants, or events (see many-worlds interpretation), its inhabitants would be unable to observe us and we would be unable to observe them.
 * One exotic method of travelling to universes is via wormholes, which require the existance of black holes with no mass. There are two problems with this: (1) black holes are the result of the collapse of massive stars, and (2) any theoretical black hole with no mass would cease to be a vacuum when matter contacts it. --Bowlhover (talk) 23:59, 16 July 2008 (UTC)

are these people crazy??
Not asking for medical advice, but surely this doesn't make any sense. Can someone point out why what they're doing is just wrong? (not asking for legal or medical advice) —Preceding unsigned comment added by 83.199.57.103 (talk) 22:31, 16 July 2008 (UTC)

specifically, the recommendation to use DOVE brand soap, which is 1/4 moisterizer, just seems wrong. here is a list of ingredients mine lists: ''sodium lauroyl isethionate; stearic acid; sodium palmitate; aqua; lauric acid; sodium isethionate; sodium stearate; cocamidopropyl betaine; sodium palm kernelate; parfum; glycerin; sodium chloride; zinc oxide; citric acid; tetrasodium EDTA; tetrasodium etidronate; alumina; alpha-isomethyl ionone; benzyl alcohol; butylphenyl methylpropional; citronellol; coumarin; hexyl cinnamal; limonene; linalool. cl 77891''. I'm not asking for medical or dental advice, but couldn't someone brushing their teeth with that stuff like, get, aluminum poisoning or something? Are any of those ingredients toxic or otherwise harmful? Wouldn't they, at a minimum, wear down the tooth enamel? surely it's no substitute for toothpaste, and even if it's true that "brushing your teeth with a regular unscented bar soap can kill all germs and remove all plaque and tartar that ordinary tooth paste cannot remove" surely there must be something equally negative about it, such as I don't know getting poisoned, or losing your tooth enamel. Otherwise why wouldn't toothpaste just have that stuff to begin with? I am emphatically not asking for medical, dental, or legal advice, just curious what the science behind that might be... —Preceding unsigned comment added by 83.199.57.103 (talk) 22:52, 16 July 2008 (UTC)
 * It is very hard for human digestion to absorb aluminium, particularly from something insoluble like alumina. Those that are poisoned by aluminium, usually have it introduced to the blood.  You will find that toothpaste can have some of those ingredients, and can make similar claims to removing plaque. The soap probably tastes horrible. Graeme Bartlett (talk) 23:09, 16 July 2008 (UTC)

The concern about aluminum, in recent years, has not been so much about acute aluminum poisoning as about the fact that aluminum has been found in the plaques in the brains of Alzheimer's patients. As I understand it, this concern has dissipated somewhat with the failure of researchers to find any direct causitive, connection, but the jury still seems to be out: this article asserts
 * While a direct causal role for aluminum or other transition metals (copper, zinc, iron) in AD has not yet been definitively demonstrated, epidemiological evidence suggests that elevated levels of these metals in the brain may be linked to the development or progression of AD.

--Trovatore (talk) 23:20, 16 July 2008 (UTC)

are you guys telling me that despite being 25% moisterizer if the ingredients are as above, they shouldn't be harmful to use in place of toothpaste? What about my enamel question?
 * I'm not telling you anything of the sort. I mostly responded to get the correct spelling of aluminum into the text as many times as possible. Because that's how aluminum is spelled, you know. Aluminum. --Trovatore (talk) 23:42, 16 July 2008 (UTC)
 * You do know you're wrong, though :-) Aluminium needs no shortcuts. And don't start me on Niteclub or Drive-Thru. ;-) Fribbler (talk) 23:51, 16 July 2008 (UTC)
 * Aluminium is a silly word; aluminum as derived from alumina was just fine, until someone decided to add the spurious i. Who knows how much platinium someone paid to IUPAC to pick the wrong spelling, but they have no authority. --Trovatore (talk) 23:56, 16 July 2008 (UTC)
 * Pah! I won't accept it. It may take another millenum before I can ententan such a thng!  -)   (a smiley without spurious 'i's). Seriously though, spelling differences are interesting, and Alumin(i)um has an interesting history in that regard. Fribbler (talk) 00:04, 17 July 2008 (UTC)
 * Consistency and common sense wins out over history every time Nil Einne (talk) 11:23, 17 July 2008 (UTC)
 * Common sense says it should be aluminum, as derived from alumina. Consistency with what? There are other element names that end in um -- platinum, tantalum. --Trovatore (talk) 17:18, 17 July 2008 (UTC)
 * But far more with ium, Americium, Barium, Berkelium, Beryllium, Bohrium, Cadmium, Caesium, Calcium, Californium, Cerium, Chromium, ... I'm now getting bored, but you get the picture, about half of all element names end in '-ium' and all recently named ones do, so this suggest convention is in favour of an 'ium' ending, with those without being the spurius early discoveries for which there was no naming convention. Aluminium QED. Philc 0780 11:32, 18 July 2008 (UTC)
 * No, that's completely wrong. Aluminum is just what you get when you change alumina from first declension feminine (or second neuter plural) to second declension neuter singular. Simple, clean, obvious.
 * As I say, alumium (derived from alum rather than alumina) would also have been OK, but it didn't win out, whereas aluminum did, in the dialect of English spoken by more than 60% of first-language speakers worldwide, namely North American English. --Trovatore (talk) 15:48, 18 July 2008 (UTC)
 * I'm sorry, but, WHAT!?!?!?? you think american english is the first language of 60% of the worlds population? do you live under a rock? are you infact some sort of shrew or snail? English in all its dialects is only the first language of 5% of the population! all I can hope for is that you added spurious 0 to your number! p.s. you mispelled aluminium again. Philc 0780 12:36, 25 July 2008 (UTC)
 * I checked out the interwiki links of Aluminium, and I didn't find ONE single language, except for English, that calls it Aluminum or similar. Almost all entries using our writing systems have it ending with "-inium". :-) Aeluwas (talk) 13:35, 17 July 2008 (UTC)
 * So what? It was discovered hmm--not quite "discovered" maybe; "first named" anyway by an English speaker, and he called it aluminum (well, first he called it alumium, which would also have been OK, but it doesn't seem to be a contender anymore). --Trovatore (talk) 17:18, 17 July 2008 (UTC)
 * Well, they're deliberately using a product for a purpose it is not meant for, and has probably not been tested as safe for. They're also foregoing the aspects of toothpaste that are known to be beneficial—the fluoride compounds. And they're justifying it based on ad hoc ideas about the benefits of anti-bacterial soap should affect their mouth (which they know nothing about—there are many types of helpful bacteria in the human body, and rampantly introducing anti-bacterial agents into different parts of it is not a great idea), and rumors about toothpaste (evil glycerin etc.), and then justifying it not with systematic testing, but confirmation bias-rich anecdotes. So yeah, in my book they're doing a few things wrong, a priori. I mean, science ain't perfect, and for that matter neither are regulatory agencies, but I trust them a lot more than some anonymous yokels on the internet and their folk medicine. --98.217.8.46 (talk) 00:10, 17 July 2008 (UTC)


 * Toothpaste and soap differ in detergent content--it's the main ingredient in any soap. Detergents can contribute to wear of dentine and soap can reduce the strength of dentine bonding agents. These people may experience a subjective benefit, but I couldn't readily find anything in PubMed that would suggest that this is an idea currently studied or recommended by the dental community, but these two studies indicate potential problems to worry about with this technique (beyond the aforementioned lack of safety testing & no fluoride benefit). &mdash; Scientizzle 17:51, 17 July 2008 (UTC)


 * I would like to point out that most toothpastes also contain detergent (usually sodium lauryl sulfate or sodium laureth sulfate), although, granted, not at the levels usually found in soaps. -- 128.104.112.147 (talk) 17:45, 18 July 2008 (UTC)


 * Indeed I know someone who gets ulcers due to this, apparently a not unknown problem. Nil Einne (talk) 07:58, 19 July 2008 (UTC)

is there a distance where eye focus and binocular effect disappears?
Is there a distance at which no normal person can tell, without moving their head for parallex effect, whether there is a poster (for example) at that distance or, for example, a mountain hundreds of miles further, because the focus and binocular effect have become imperceivable? Sorry for the awkward phrasing, I think you get what I mean and you're welcome to offer to a better phrasing. —Preceding unsigned comment added by 83.199.57.103 (talk) 22:39, 16 July 2008 (UTC)


 * Yes and no. Somewhere around 20-50 feet away, binocular cues start being useless for depth perception, but the brain uses many other techniques as well.  You might be interested in the article depth perception and the articles linked from the "monocular cues" and "binocular and oculomotor cues" sections. --Carnildo (talk) 23:22, 16 July 2008 (UTC)


 * you said binocular cues are useless, is that true of focus too? —Preceding unsigned comment added by 83.199.57.103 (talk • contribs) 23:39, 16 July 2008
 * Yes, because compared to the size of a human eye's lens, 20-50 feet is almost an infinite distance. Imagine a point source of light at 7 m with the middle of the lens directly facing it.  Since the source's image on the retina must also be a point, the lens refracts all light rays onto the centre of the retina.  5 mm from the lens' centre, light from the source is bent by 0.04 + x degrees; a refraction of 0.04 degrees would cause the light ray to be perpendicular to the retina, while an additional x degrees is needed for the ray to hit the retina's centre.  Rays from an infinitely-distant source are refracted by x degrees, where is only 0.04 degrees less than the source at 7 m.
 * As for the binocular effect, the distance between the eyes is 5 cm. The angular positions of a 20-ft-distant object that the eyes report differ by 0.6 degrees, which is the angular diameter of the Sun--probably large enough to notice.  30 m is the distance at which an object's apparent positions differ by 0.1 degrees, so I would say the binocular effect absolutely cannot be used at greater distances.  --Bowlhover (talk) 01:08, 17 July 2008 (UTC)


 * This is just anecdotal, but it relates to the question, so I'll tell the story. I wear glasses for myopia.  One time years ago I got a new prescription for slightly stronger glasses.  I put them on in the optician's office and they seemed fine.  I then stepped outside and discovered that most of the world had become flat: nothing was farther than 20 feet away!  I was traveling by public transit and next had to cross a 4-lane street to get to my stop, and crossing the street with that illusion in place was downright surreal.  The cause, of course, was that with the old prescription my eyes had been unable to quite focus at infinity -- and my brain had learned to use this as a distance cue!  Anything that's in sharp focus, it had learned, must be 20 feet away if binocular vision doesn't say it's closer.
 * Fortunately, the brain adapts well; the effect faded within an hour. --Anonymous, 05:30 UTC, July 17, 2008.


 * Another anecdote. I've found that looking at photos with a significant depth (it works better with some then with others) with one eye gives them an almost 3D look. Obviously with no binocular vision, the brain starts to look at other clues more and you see depth that isn't there Nil Einne (talk) 11:19, 17 July 2008 (UTC)


 * As an example of what I'm talking about, try closing one eye and looking at these photos Image:CH Gotthard Basistunnel Amsteg 1.jpg, Image:Sharpened Pencil.jpg, Image:SchwetzingenSchlossgarten.jpg for a while. You may find they start to look like they really have depth Nil Einne (talk) 21:05, 26 July 2008 (UTC)


 * Trompe-l'œil 79.66.90.252 (talk) 13:13, 17 July 2008 (UTC)