Wikipedia:Reference desk/Archives/Science/2009 May 16

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May 16

Dryer sheets

So I have some uniforms for work. On the laundry label it says, in big bold letters, "DO NOT USE DRYER SHEETS." I'm just curious, what's the big deal? Can dryer sheets ruin the clothes somehow? They seem so harmless. TravisAF (talk) 03:28, 16 May 2009 (UTC)

What line of business are you in? Maybe there is some special reason? If (for example) you were in the medical field - perhaps some patients are allergic to things on dryer sheets...I have no idea whether that's true - but it's a thought at least. SteveBaker (talk) 03:31, 16 May 2009 (UTC)

Hmmm TravisAF's user page says he's in the airforce. Airforce uniforms and dryer sheets? SteveBaker (talk) 03:33, 16 May 2009 (UTC)

From what I've been told, dryer sheets affect the absorption of cloth like towels. I doubt that applies here though... Dismas|^(talk) 03:43, 16 May 2009 (UTC)

Google says "..not using fabric softeners or dryer sheets since chemicals from these could clog the pores of the uniform's polyester material and adversely affect performance."[1] and "Evidently the PTU is a special moisture resistant fabric with evaporative properties that is ruined by both liquid fabric softener and dryer sheets."[2] in the specific case of US armed forces PT uniforms. Nanonic (talk) 04:01, 16 May 2009 (UTC)

Microfiber clothes and cleaning cloths sold in Germany bear a warning label not to use fabric softener to avoid ruining them. I've never seen that on any microfiber materials sold in the States. I was wondering whether the European fabric softener was different or whether they just didn't expect Americans to follow such labels anyway, so why bother? 71.236.24.129 (talk) 11:18, 16 May 2009 (UTC)

Using fabric softener on certain microfiber cloths (in particular the one's from Norwex, which are sold in the US now) is a big no-no. The chemicals in the fabric softener are designed to coat the fibers of your clothes and stay there for days and days releasing more chemicals that smell good. This chemical coating is a bad thing for high-quality microfiber cloths with a silver agent in them. The silver agent prevents bacteria growth in the cloth, resulting in a stink free cloth. But add some fabric softener and it coats the fibers, creating a barrier between the silver agent and the bacteria. Greenjen99 (talk) 03:56, 31 July 2010 (UTC)

Digestion

Some people claim that mans digestive system is unsuitable for digestion of flesh of the other animals, but neither can we digest uncooked plant products!!Like we cook meat before consumption we cook even vegetables..We cook most of the natural products.Is meat which is cooked also hard to digest??? —Preceding unsigned comment added by 59.165.84.9 (talk) 05:29, 16 May 2009 (UTC)

The enzymes in your stomach primarily break down meat while other biomolecules are broken down in the rest of the gastrointestinal tract. Humans can indeed digest uncooked plant products, such as bananas. JameKelly (talk) 07:44, 16 May 2009 (UTC)

I'm also intensiely curious about this subject. Many vegetarians - the ones who take the whole thing really seriously - says that the human digestive system doesn't digest meat properly, and that it basically sits in your gut and ... rots. Is there any truth to any claim that eating meat is really that bad for you? The only real facts I know about it (which may or may not be right =p) are that you can't get vitamin B12 from any natural source other than meat, and that the unhealthiest natural fats are also found only in meat... 90.193.232.41 (talk) 08:41, 16 May 2009 (UTC)

Partly they're playing word games. Digestion and rotting both describe the Decomposition of orgainc material. When the Gut flora breaks down long chained fats some toxic substances can get produced. I have no data on whether that only happens if the digestive enzymes haven't broken down the chains sufficiently or whether that always happens. The argument loses a lot of momentum if you look at food chemistry. There are plenty of toxic chemicals in vegetarian foods (Cyanide came up quite often, glycoalkaloids are in potatoes and cinnamon contains coumarin, to name just a few.) Problems arise when petri dish results are transferred to complex real life systems. Evidence based medicine often fails to come to the same conclusions as theoretical models based on studying individual components. Dietary supplements are often not taken up as efficiently as the real nutrients. (google a study for calcium from cheese vs, pills for an example. Don't know of a B12 study.) I have severe doubts that a diet that has been proven to be deficient in at least one essential nutrient can be healthier than a good mixed diet. The thing is we're not eating that either. Some meat is consumed dried rather than cooked. See e.g. Pemmican Jerky (food) For raw meat see Steak tartare. Countless fruits, nuts and vegetables are consumed raw. (Think of all the things you could put in a salad bowl)71.236.24.129 (talk) 11:02, 16 May 2009 (UTC)

Cooking meat does assist digestion, but it's not essential. A much more important concern is infectious disease. The modern processing, storage, refrigeration and handling of meat may lead to harmful bacteria growing in the meat. If the meat isn't cooked properly, this can lead to food poisoning. Axl ¤ [Talk] 11:24, 16 May 2009 (UTC)

Although improper handling of vegetables has also caused a lot of sickness as well, both bacterial (E. Coli for example) and viruses (Hepatitis A, from recent memory). Improper handling of food is bad no matter what it is. -- JSBillings 13:03, 16 May 2009 (UTC)

I'll just come out and say it: it is scientifically incorrect to say we are not able to digest meat well. Actually, it's totally wrong and out of touch with reality. We are actually very well designed for meat consumption: our stomach is full of gastric acid specifically tuned to the right pH to catalyze protease and break down protein found in meat. In fact, we are more specifically tuned for digesting meat than we are for cellulose, which must pass out as roughage. Although we are omnivores, we have more structure and metabolism in common with carnivores than with herbivores. Take a look at human canine teeth and incisors. These are not designed for chewing leaves and roots. (We have molars for that, but unlike an herbivore, we do not replace our molars every year or so). Anybody who wants to make the claim that we are biologically "designed" for vegetarian diets should reconsider their facts. Humans are omnivores. In a modern industrial society, we are able to provide sufficient nutrition with a wide variety of alternative diets (including vegetarianism, which may have some health benefits), but we did not evolve "naturally" to be herbivores. Nimur (talk) 16:14, 16 May 2009 (UTC)

And 90.193 says: "Many vegetarians - the ones who take the whole thing really seriously - says that the human digestive system doesn't digest meat properly, and that it basically sits in your gut and ... rots" which appears to say that all serious vegetarians are cranks who quote anti-science. I assure you that this is not true: some do, no doubt, but not all. --ColinFine (talk) 22:02, 25 May 2009 (UTC)

Bird identification

Garden Warbler?

I asked on the Commons help desk if there was somewhere I could check a bird identification (to avoid misclassifying a photo) and was referred here. If this is the right place to ask, could someone tell me if the identification is correct? If not, is there somewhere else I can ask? N p holmes (talk) 09:00, 16 May 2009 (UTC)

I agree with your ID as a Garden Warbler - I looked at it in the Collins Bird Guide. It's the grey patches at the side of the head that clinch the ID. Wood and Willow Warblers are yellower, as is the Chiffchaff. The only real way to absolutely clinch the ID is to hear it, though: the Garden Warbler has the most wonderful song of the summer. --TammyMoet (talk) 09:22, 16 May 2009 (UTC)

Thanks. I did hear it (a fast song with interspersed slightly longer notes): not a Willow Warbler or Chiffchaff, but I've never heard a Garden Warbler. N p holmes (talk) 11:01, 16 May 2009 (UTC)

Suicide Bridge

Isn't it possible to survive a jump into the water from a suicide bridge? Assuming you don't bellyflop.68.148.149.184 (talk) 09:14, 16 May 2009 (UTC)

If you look at Drag (physics) The force depends on the density of the medium. Compare 1.204 for air to 1000 for water from our article. A person Diving off a board that is 10 m (about 11 yd) high will hit the water at almost 50 km/h (31 mph). They will try to achieve a mostly aerodynamic form when they enter the water and try to minimize the area of impact. They will also most likely not choose their head as the first point of impact, but try to create flow around their hands and arms first (also see La Quebrada Cliff Divers). A person jumping off one of those bridges would hit the water at a higher speed (maybe not quite terminal velocity) and will likely present a lot of vulnerable surface area to the impact. Even if they don't break their neck, their skin might break on impact and they'd bleed to death because blood doesn't clot effectively in water. 71.236.24.129 (talk) 10:10, 16 May 2009 (UTC)

The world record for the highest dive stands at over 50m (see Dana Kunze) whereas the mid-span clearance below the Sydney Harbour Bridge, for exampe, is 49m - so, yes, such a jump into water is theoretically survivable, but only with a high level of fitness and training. Gandalf61 (talk) 10:59, 16 May 2009 (UTC)

Presumably that record breaking diver survived the dive with no, or insignificant, injuries. If you land feet first from a pretty high bridge you can easily break your legs but otherwise survive as long as someone drags you out quickly enough and you get medical attention. I'm not sure what the highest survivable dive would be, but it has to be more than 50m. --Tango (talk) 13:32, 16 May 2009 (UTC)

There are MANY people who have survived falls from airplanes without a parachute ([3] for example) - landing in bushes or whatever. I'm sure some of those ended up in water. (See also Free-fall#Surviving_falls) So it's definitely survivable - even at terminal velocity - but it's definitely not certain - or even likely - so it's not recommended. There are more interesting cases in Category:Fall survivors - and some useful data on fall survivability in Alcides Moreno. SteveBaker (talk) 16:03, 16 May 2009 (UTC)

No need to consider hypotheticals or falls from airplanes, there are plenty of documented cases of people surviving actual bridge suicide attempts. Golden Gate Bridge says "As of 2006 only 26 people are known to have survived the jump", but also "Some of those who survive the impact, drown or die of hypothermia in the cold water". So depending on how they counted, at least 26 and maybe more survived the fall (out of 1200 or more). -- BenRG (talk) 21:02, 16 May 2009 (UTC)

I read an article once, sorry I have no idea where, claiming that of all the survivors of Golden Gate Bridge jumps, 100% of them had landed feet-first, and, it's claimed, leaning slightly backwards. Tempshill (talk) 03:27, 17 May 2009 (UTC)

On Mythbusters there was an episode where they tested what it would be like to fall from the Golden Gate Bridge, but having a hammer or something fall below you to break the surface of the water just before you hit. They said there was a myth that this could save your life. The crash test dummy, Buster, was damaged in just the same way as when they did a control without the hammer. In fact, one of its legs came off. It's unlikely to survive such a fall, but, as posters have said above, it is possible. On a side note, There is a terminal velocity, so after a certain point it really doesn't matter how high you fall from, because you'll still be going the same speed (slightly simplified explanation).--KageTora - (영호 (影虎)) (talk) 02:29, 18 May 2009 (UTC)

I read (in one of those worst-case scenario books, I think; don't know the reliability) that a common source of injury when going in feet-first is a jet of water shooting up your bung hole and rupturing your colon. "Puckering saved my life". --Sean 13:34, 18 May 2009 (UTC)

It's interesting to note that there is a "worst height" from which to drop a cat. If you drop them from higher, they will react during the fall and spread out their bodies to slow their terminal velocity. There are wacky cases of cats falling from tall buildings with minimal injuries. Dcoetzee 03:04, 19 May 2009 (UTC)

So, a well trained and fit person could survive a fall from a height from where he would reach terminal velocity if falling into water, with a good tactic? For example, wearing gloves, falling horizontally to achieve a slower terminal velocity, and before the impact changing to a vertical position heads down, arms extended, the gloved fists hitting the water first? That would mean if you survived a 1 km fall, you could survive a 10 km fall as well. --131.188.3.20 (talk) 09:24, 25 May 2009 (UTC)

Age and energy

Why do people above 16 seem to have less energy than those below 16? Thank you. Clover345 (talk) 10:24, 16 May 2009 (UTC)

After 16 we save our energy for things that under-16s in the old days weren't supposed to know about. Cuddlyable3 (talk) 10:37, 16 May 2009 (UTC)

Er no, I don't think that's a very good answer. —Preceding unsigned comment added by 82.44.54.169 (talk) 11:11, 16 May 2009 (UTC)

What do you mean, energy? Olympic athletes are usually not under sixteen. Similarly for Artic explorers who pull sledges to the poles. Perhaps you are thinking about under 16s being less inhibited with moving their bodies around than older people are, such as break-dancers. 78.146.190.197 (talk) 13:32, 16 May 2009 (UTC)

I think simple physics explains this. Assume your "under 16" kid is half your adult height - that means that they have something like one-eighth of your weight and their muscles have one quarter the cross-sectional area. The power produced by a muscle is proportional to it's cross-sectional area - and the amount of work it has to do to (say) have the kid run around yelling something annoying over and over again - is proportional to the kid's mass. So their power-to-weight ratio is twice that of an adult that is twice their size. So I'd conclude that while they might SEEM to have twice the "energy" you have - in reality, they are really able to produce twice the acceleration of one eighth the mass. Obviously as your size approaches that of an adult - this capability gets less and less pronounced. Once you are 90% of the size of an adult (perhaps) at age 16, you have pretty much reached that all-time-low. SteveBaker (talk) 15:54, 16 May 2009 (UTC)

It won't be 1/8 the mass. Humans don't remain in the same proportions are they grow, that's why Body Mass Index is calculated with the square of height, not the cube. Imagine we have a median BMI 4 year old that is 90cm tall and a median BMI adult that is 180cm tall. According to the graphs on our BMI article, the child should have a mass of 13kg and adult should have a mass of 71kg. That's about 1/5.5, quite a bit more than 1/8. I don't know how cross-sectional area of muscles actually varies with height and age, but I doubt it is as simple as for the spherical cow you are assuming. --Tango (talk) 18:50, 16 May 2009 (UTC)

Well, duh - obviously it's not that simple - but whatever is? The point is that small animals have more 'bounce' than big ones...it's a good explanation - despite all of the obvious approximation. SteveBaker (talk) 03:13, 17 May 2009 (UTC)

I'm not convinced that you get an at all meaningful answer after all that approximation. While there may be an increase in apparent energy due to this I suspect that it is negligible. Humans are nothing like spherical cows, not even approximately. --Tango (talk) 14:30, 17 May 2009 (UTC)

The relevent Wikipedia article here is Senescence, which is the study of the process of aging. There's lots of good links from that article to take you where you want to go. --Jayron32.talk.contribs 19:58, 16 May 2009 (UTC)

It doesn't apply very well to the difference in 'energy level' of (say) a 12 year old compared to (say) a 20 year old - which is the kind of thing we're being asked for here. SteveBaker (talk) 03:13, 17 May 2009 (UTC)

For a biological answer, there is evidence that "energy" correlates with the level of dopamine released in the brain -- this is how amphetamine and cocaine exert their energy-enhancing effects. There is also, I have read, evidence that dopamine release is highest in children, and drops steadily with age. Very low levels of dopamine produce Parkinson's disease, which is characterized by torpor. Looie496 (talk) 19:41, 17 May 2009 (UTC)

What is known about the causes of Parkinson's disease. I struck the irresponsible claim above. Cuddlyable3 (talk) 21:03, 18 May 2009 (UTC)

The sentence you struck was correct, see Parkinson's disease#Pathophysiology. Parkinson's disease is the best understood of brain diseases in the sense that we know exactly what the damage is: loss of dopamine cells. Unfortunately, we don't have a very good understanding of what causes the dopamine cells to be lost. Looie496 (talk) 21:47, 18 May 2009 (UTC)

Swans - can they break your arm?

I have often heard that a swan can break your arm. There isn't anything on the swan article about this - is this true or is it an urban myth. Also should there be something in the swan article about this? Catoutofthebag (talk) 11:09, 16 May 2009 (UTC) Additional question Also are there any recorded incidents of people having their arms broken by swans? Catoutofthebag (talk) 11:42, 16 May 2009 (UTC)

Whooper swan says they can be up to 15 kgs. That means their wings can produce enough lift (force) to move those 15 kgs. Think of hitting something with a 15 kg Mallet. People who handle swans learn how to disable their wings when grabbing them, from experienced swan handlers. (Only example I know is from Hamburg, Germany de:Eppendorfer Mühlenteich.) —Preceding unsigned comment added by 71.236.24.129 (talk) 11:38, 16 May 2009 (UTC)

The "mallet" would have a large wing attached to it, which would slow it down. And being kicked by a 200lb person is probably not going to break a limb either. It is unlikely that Swans move their wings fast enough to provide 15kg of lift when threatening people, as they would either take-off or fall over if the wings were flapped horizontally. The swan handlers would be worried about the swans breaking their wings, as with handling other birds. 78.146.190.197 (talk) 14:37, 16 May 2009 (UTC)

It's a myth.--80.3.133.3 (talk) 12:56, 16 May 2009 (UTC)

Swans in the UK are in theory owned by the Queen. For hundreds of years they have been owned by royalty, and I believe were eaten by them. I understand that the sawns-can-break-your-leg myth was just put about to stop the peasants from eating them. 78.146.190.197 (talk) 13:26, 16 May 2009 (UTC)

On that site it says "From Swanuk.org: "Yes, but only in exceptional cases. If a wing in full span and velocity were to hit a weak-boned person (such as a child or an elderly person) then it is theoretically possible. In reality it is almost unheard of and is never used as a form of attack as swans are a defensive bird. The only time they become aggressive is when they are protecting their nesting ground or cygnets when they will chase off intruders, be they other swans, geese or humans who get too close." So is the answer a yes or a no? Or a theoretical yes. Catoutofthebag (talk) 13:42, 16 May 2009 (UTC)

Parsing the quoted text above indicates that the answer is "no" in almost all circumstances. The answer could only be "yes" in theory for a child or elderly person. 78.146.190.197 (talk) 13:48, 16 May 2009 (UTC)

Anecdote time. I used to share a house with a guy who slaughtered domestic geese for a living (several years before). He told me that a goose had once broken his wrist with a strike from its wing as he was trying to restrain it. He did have some sort of bone condition though... --Kurt Shaped Box (talk) 15:14, 16 May 2009 (UTC)

OR: My Thanksgiving turkey from last year was a fell beast, at least as strong as a swan, and it gave me some pretty good whacks, but nowhere near hard enough to break anything. --Sean 14:53, 16 May 2009 (UTC)

Oh dear. It's also a "myth" (read "not true") that swans in the UK are owned by the Queen. See - er - swan.--86.25.195.52 (talk) 06:32, 17 May 2009 (UTC)

The Swan article does not mention (at the time I read it) the Queen as far as I can see, but the Swan Upping article says that swans are owned by the British monarch - currently the Queen. 78.146.103.200 (talk) 16:10, 17 May 2009 (UTC)

"Today, the Crown retains the right to ownership of all unmarked mute swans in open water, but The Queen only exercises her ownership on certain stretches of the Thames and its surrounding tributaries.

This ownership is shared with the Worshipful Company of Vintners and the Worshipful Company of Dyers, who were granted rights of ownership by the Crown in the fifteenth century. Nowadays, of course, the swans are no longer eaten." From the official website of the British monarchy. 80.41.111.135 (talk) 19:37, 17 May 2009 (UTC)

There's an urban legend doing the rounds that says that killing a swan in Britain is considered an act of high treason and that theoretically, they're still allowed hang you for it. I've had several people quote that little factoid to me over the years... --Kurt Shaped Box (talk) 23:12, 17 May 2009 (UTC)

is there any evidence that the NSA uses Papal infallibility?

Is there any evidence (a leak, etc) of cooperation between the NSA and the vatican for using Papal infallibility to break encryption, for example, by factoring large composite numbers. Once the factors are produced, they are very easy to verify... --94.27.244.146 (talk) —Preceding undated comment added 11:25, 16 May 2009 (UTC).

I am very confused as to what you are asking. Are you saying that the Pope could theoretically use infallibility to have God factor the numbers for him? If so, this is really a question for the humanities desk. Although, if this is what you're asking, it is ridiculous; Papal infallibility only applies to matters of faith. The Pope can't decree who's going to win the Super Bowl, after all :-D -RunningOnBrains 11:41, 16 May 2009 (UTC)

Papal infallibility means the Pope can't be wrong, though you're right in that it applies to matters of faith. However, maybe there is a way to spin a large number with mysterious, unknown factors into a question of faith? If so, is there any evidence that the NSA has done this in cooperation with the Vatican? (The reason it's not "ridiculous" -- I mentioned this before -- is that the NSA doesn't have to believe in papal infallibility for it to work: the numbers are very easy to verify once the Pope produces them.) Any evidence of this ever being done? --94.27.244.146 (talk) 11:59, 16 May 2009 (UTC)

Believing that God would be swayed by any kind of spin is about as dumb as believing a good lawyer could get you out of Hell. SpinningSpark 12:04, 16 May 2009 (UTC)

(edit conflict) Again, you misunderstand the concept of Papal infallibility (I suggest you read the article). It does not suggest that the Pope can not be wrong, it is a provision where a Pope, if given a revelation by the Holy Spirit about church doctrine, can speak ex cathedra, and can not be accused of incorrect reasoning (since the "reasoning" came from God himself). -RunningOnBrains 12:06, 16 May 2009 (UTC)

I'm sorry, but there is no reason church doctrine cannot be massaged into including a factorization. The Vatican could very easily come up with questions of doctrine for the Pope the answering of which would be equivaelnt to factorizing a number. No reason it couldnt be done, and you have not given any. But I've just realized something: you haven't answered my actual question, about any evidence of cooperation between the NSA and the Vatican, at all! So if there is some evidence of that, then your whole answer could be considered a deterrent... --94.27.244.146 (talk) 15:41, 16 May 2009 (UTC)

Sorry, merely trying to clear up an apparent misconception. (But it is true...I am in favor of censorship in all its forms...especially when people get too close to the truth.) -RunningOnBrains 19:17, 17 May 2009 (UTC)

There is a popular misconception that papal infallibility means that the pope is never wrong. That is not the case. It's not even the case that it means that the pope is never wrong when talking about religion/faith. What it does mean is that under certain conditions the pope can proclaim that he has been divinely inspired as to the truth of a certain matter. The Catholic philosophy is that God (the Holy Spirit) would not allow the pope to be wrong when making such ex cathedra proclamations. (Again, while ex cathedra means "from the chair", it doesn't actually mean that there is a special chair he sits on which makes him infallible. The chair is a metaphor referring to his official position as pope.) There are a number of rather strict conditions that must be met before papal infallibility is considered to hold - it is not used on a routine basis. Out article on papal infallibility in fact only lists seven instances in the past 2000(ish) years, the most recent one being back in 1950. Pope John Paul II did not make any ex cathedra proclamations, despite having a relatively long tenure of 27 years -- 76.201.155.7 (talk) 12:15, 16 May 2009 (UTC)

I understand there are very special conditions which must be met for such a procalamtion. Is there any evidence that shows the NSA and Vatican cooperate secretly to make, but not disseminate, such proclamations? Also, your implication that there are only seven instances in the last 2000 years is misleading...the article only lists seven that were recounted in a 1985 study, and the Wikipedia article you just linked continues "The Vatican itself has given no complete list of papal statements considered to be infallible.". As far as I can see the conditions, he would have to speak on a matter of faith that must apply to all followers of the church. I don't see why such a proclamation could not at once answer a question important to the NSA, and I also dont see why it should not be possible not to disseminate this proclamation (keep it secret). If there is no evidence of NSA cooperation with the vatican, why don't you, and the other poster above, just say this? —Preceding unsigned comment added by 94.27.244.146 (talk) 15:51, 16 May 2009 (UTC)

Is this question based upon some sort of conspiracy theory, as a matter of interest? --Kurt Shaped Box (talk) 15:59, 16 May 2009 (UTC)

Even if we accept Christianity and Papal Infallibility as fact, This isn't something the pope can do on demand. (Too bad. If it worked like that it'd be extremely testable. We could have a scientific proof of God in about ten minutes.) The only reason he's infallible is because he's directly relaying a message from God. If God sent you a message personally it'd be just as infallible, except no one would ever believe you. Presumably if God wanted to help the NSA crack some codes, He wouldn't even have to bother the Pope. He could send the decryption keys to the NSA directly. 16:27, 16 May 2009 (UTC)

Of course there's no evidence. It's completely absurd. Nobody can provide any links for you (besides the obvious ones of papal infallibility and NSA) because the idea is so bizarre that nobody has ever thought it worthwhile to refute it. If you had read those articles, you would realize that your question makes as much sense as asking whether the Luftwaffe had secretly been involved in the formulation of Avogadro's number. Matt Deres (talk) 16:39, 16 May 2009 (UTC)

Nobody on here has yet said categorically, "no, there is no such evidence" because nobody has ever researched such a topic. There is no reference we can cite that says "there is no evidence". But even so, I am going to go out on a limb here, and say, no, there is no reliable evidence that the NSA and the Pope have been conspiring together to use whatever misinterpretation of papal infallibility you are working under to break encryption techniques. (I estimate a very low probability that I will be proven wrong in this claim). The very notion is ludicrous, but since you won't give up until someone tells you "no", here it is. No. Maelin (Talk | Contribs) 16:36, 16 May 2009 (UTC)

If such evidence did exist, we would all be furiously investigating it to determine if it was valid evidence. I don't think there's any evidence at all - not even flimsy evidence. If the original questioner believes he/she has found some evidence, then by all means, present it to us so we can tear it to shreds with the merciless scientific method. Nimur (talk) 16:52, 16 May 2009 (UTC)

Well, here was "pope", "nsa", and "crytpography" mentioned on the same page, and at IBM, no less. Nimur (talk) 16:55, 16 May 2009 (UTC)

“ If you haven't been following the cryptography area lately, let me assure you that this action by the NSA was the crypto equivalent of the Pope coming down off the balcony in Rome, working the crowd with a few loaves of bread and some fishes, and then inviting everyone to come over to his place to watch the soccer game and have a few beers. There are some things that one just never expects to see, and the NSA handing out source code along with details of the security mechanism behind it was right up there on that list. Up to this point, the NSA has embodied in itself the classic Cold War paranoia imperative of the past 50 years ("If you knew what we knew, you'd agree with us"). To see it spewing source like some long-haired Stanford student was enough to make for uncontrollable twitching. ” — Larry Loeb, Uncovering the secrets of SE Linux

No. There is no evidence whatsoever. (This is a summary version of the text I wrote that was lost by an edit conflict). The Pope is a normal human being. He has no supernatural powers, because there is no such thing as the supernatural, although it often makes a good storyline for various types of fiction. To stay sane, base your beliefs on true evidence, particularly scientific evidence, otherwise you'll end up like David Icke. You might as well say that the CIA is covering up the evidence that pigs can fly. I find it a matter of concern that in my experience, many North Americans barely discriminate between fact and fiction. 78.146.17.231 (talk) 17:15, 16 May 2009 (UTC)

you might as well say that the CIA is covering up the evidence that pigs can fly -- I guess you haven't been keeping up on the biggest news item of the past few weeks: swine flu. 94.27.244.146 (talk) —Preceding undated comment added 18:45, 16 May 2009 (UTC).

There is no rational link between the CIA's flying pigs conspiracy, and swine flu. Try to avoid jumping to conclusions. 78.146.17.231 (talk) 22:36, 16 May 2009 (UTC)

The swine flu conspiracy? Nimur (talk) 23:37, 16 May 2009 (UTC)

Anyway, the CIA have more important things to cover up. Like how the government puts fluoride in the water to turn the poor homosexual and thus reduce the birth rate... ;) --Kurt Shaped Box (talk) 22:49, 16 May 2009 (UTC)

The trolls are out this weekend. Tempshill (talk) 03:30, 17 May 2009 (UTC)

How to identify flowering plants - both wild and garden?

There are several flowering plants I would like to identify, both wild flowers (here in the UK) and garden flowers. Is there any online database that helps in the identification of such flowers? And are there any usefull clues to narrowing the identification down, such as the number of petals? I have a copy of a flora - the New Flora Of The British Isles by Clive Stace - but you need to be a trained latin-speaking botanist to use it, and it has very few illustrations. 78.146.190.197 (talk) 13:16, 16 May 2009 (UTC)

Here's [4] somewhere to start. You'll need to submit info, but it also serves to familiarise you with some technical words which might assist you with your book. Richard Avery (talk) 14:21, 16 May 2009 (UTC)

You need a botanical key. By the way this is just a redirect and we could do with a more specific article! These can be in several steps, firstly to identify the family, and then down to finer levels of classification. I have an old one in book form to identify genera. Graeme Bartlett (talk) 08:20, 17 May 2009 (UTC)

I mentioned above that I already have got a "botanical key" - I am more familar with it being called a flora. I eventually, after several goes, identified the plant I was most curious about partly using the link above thanks - it is commonly called Green alkanet. 78.146.103.200 (talk) 16:27, 17 May 2009 (UTC)

Adaptation or death effect?

I was chatting with a friend and my thoughts sort of got off on a tangent about the human body. I know that, for example, if you eat too much of X you might end up actually needing to eat excess amounts of X because your body is "dependant" on the higher amount. The way people talk about it you'd think the body is aware of itself and makes conscious decisions. Obviously untrue. But is there a specific mechanism in the body that makes it absorb less of something if excessive amounts are present, as a failsafe? Or do the cells that absorb it naturally end up dying from the overdose, leaving only cells that absorb it inefficiently to survive and replicate themselves (a bit like how "supervirii" come about)? 97.104.210.67 (talk) 15:54, 16 May 2009 (UTC)

The effect you are describing sounds like Physiological tolerance which is a redirect to Drug tolerance right now, and contains links to other articles. You may want to follow some of those links and see where it takes you. --Jayron32.talk.contribs 18:49, 16 May 2009 (UTC)

@97.104.210.67 -- Can you justify your assertion that "if you eat too much of X you might end up actually needing to eat excess amounts of X because your body is "dependant" on the higher amount"? While this may be true for drugs as a special case (see Jayron's comment) I don't generally think this has much to do with typical dietary intake. Perhaps you should start by reading about how nutrients are absorbed into the body. Try the articles gastrointestinal physiology and anatomy. In answer to your question, one mechanism by which the body adjusts nutrient uptake is by regulating cell surface proteins on the enterocyte that participate in transport of small molecules across the brush border into the blood stream. --- Medical geneticist (talk) 19:11, 16 May 2009 (UTC)

Minimum force to break an arm (inspired by swan question above)

The above swan discussion (not sure how to link to it) got me thinking - is there are a minimum amount of force required to break an average (healthy) human arm? People seemed to suggest it wouldn't be possible for a swan to, but then i've seen footballers break bones with seemingly minimal force (I guess it may be lots of force just it's not apparent from the camera's perspective). Anyhoo I would've thought that a 'lucky' swan and an 'unlucky' human could result in a swan breaking their arm. ny156uk (talk) 16:59, 16 May 2009 (UTC)

oh come on, "minimal" force? We've all run into door frames, table edges, etc a few times in our lives, not to mention falling on ice etc, none of this breaks an arm! (except perhaps among the elderly) —Preceding unsigned comment added by 94.27.244.146 (talk) 18:31, 16 May 2009 (UTC)

It depends entirely on how the force is applied. The angle and concentration of the force in certain areas will have very different results. Are we striking the arm against the edge, or "jamming" the arm at the wrist or elbow? Are we affecting the humerus or the ulna or the radius bone? There's just far to many variables to predict what will happen. You can break an arm after tripping and falling, and you can be hit by a car and not break an arm. You aren't going to get a reliable number here... --Jayron32.talk.contribs 18:43, 16 May 2009 (UTC)

My friend broke his arm falling off a low sofa. I think it depends how you land. Catoutofthebag (talk) 20:43, 16 May 2009 (UTC)

I think people often underestimate the forces involved. Typically, when footballers break bones, the impacts aren't anywhere near as light as they may seem. First of all, these guys tend to be running at the time, so they're packing quite a bit of energy there. Momentum and mass -- typically, their own body (and your average footballer isn't a short skinny guy) -- can result in pretty impressive forces. I mean, it often looks like they're not really doing all that much (still photographs and slow motion can really fool the eye), but if you've got a guy who weighs, say, 80 or 90kg (about 175 to 200 pounds) running just about as fast as he can, he represents a lot of energy. If he suddenly comes to a stop so that all of that energy is concentrated on a single limb, that's a lot of stress right there.

This video (which, I should add, is work safe but may not be something you want to see, because it does involve a pretty nasty-looking leg break), for example, shows a guy who's just running. Nobody touches him, he doesn't really stumble or anything, but he is trying to slow down and change his direction of movement very quickly to take control of the ball, and unfortunately the way he puts down his foot concentrates the forces involved on that his leg, and the bone just can't take it. Yet his movements seem kind of light, almost effortless, until he falls down.

By comparison, let's take high-speed motorcycle races: crashes tend to look far more dramatic, but the riders often walk away without any serious injury. The reason for this is that not only are they wearing protective gear, but the tracks tend to be flat and surrounded by wide areas of clear grass. That means that when they crash, they can just slide and expend the energies involved until they come to a stop. They typically aren't badly injured unless their initial landing right after the fall is bad or they get hit by another bike -- all they get is bruises and maybe some burns from the friction. The point is, even though the crashes may look very violent, the actual forces the rider's body is subjected to often aren't that great. It's all in how you expend the energy. -- Captain Disdain (talk) 02:20, 17 May 2009 (UTC)

• • In an even more dramatic example, I recently saw footage of a racecar crash in which the car launched into the air, bounced off the guard fence in front of the audience, slid to a stop and burst into flames. The driver walked away from the car apparently uninjured - a woman in the crowd broke her arm. Dcoetzee 02:51, 19 May 2009 (UTC)

HIV antibody testing

Is it possible to have a negative result from HIV antibody test after use of antiretroviral drugs?¬¬¬¬ —Preceding unsigned comment added by Tunmisadej (talk • contribs) 17:55, 16 May 2009 (UTC)

You mean for someone that is HIV positive, presumably? --Tango (talk) 18:35, 16 May 2009 (UTC)

I don't get why a person would have such a test taken if they are already HIV positive -- that status doesn't change -- as indicated by being on antiretroviral drugs... I think we're going to need more background on this one... 94.27.244.146 (talk) 18:49, 16 May 2009 (UTC)

I can think of a cynical reason for taking such a test — with the intention of demonstrating a negative result. Antiretroviral drugs do not remove the antibodies, so the HIV (antibody) test remains positive. However the test can occasionally give false results — see "HIV test#Accuracy of HIV testing". Axl ¤ [Talk] 22:35, 16 May 2009 (UTC)

It's not uncommon for someone to receive care in a location (e.g. country) far from home. Sometimes they are unable to speak due to an acute illness, and they might not have their medication list with them. --Scray (talk) 23:44, 16 May 2009 (UTC)

You can be HIV+ without knowing it, of course. The OP asked if it was possible to get a negative result - interpreted literally, the answer is clearly "yes". You can get a negative result by being HIV-. --Tango (talk) 00:41, 17 May 2009 (UTC)

The standard tests using ELISA screening followed by Western Blot confirmation remain reliable, but false-negative tests in persons receiving long-term antiretroviral therapy have been reported with some of the "quick" tests, which must be interpreted with care (some are no longer in use). --Scray (talk) 23:44, 16 May 2009 (UTC)

I read the OP's question as: Suppose a patient is HIV-positive and takes the drug cocktails. Is it possible for the virus to be hammered down so much in quantity that he'll test HIV-negative? Tempshill (talk) 03:38, 17 May 2009 (UTC)

That's a nice find, Scray. Of note, "These data suggest that these subjects experienced anti-gp41 seroreversion as a consequence of early and prolonged suppression of viremia by HAART." So the answer to the original question is: yes, depending on which test is used. Axl ¤ [Talk] 09:28, 17 May 2009 (UTC)

Thanks and agreed. This highlights the value of our standard test for HIV, and the importance of being very careful before offering alternatives as equivalent. --Scray (talk) 11:00, 18 May 2009 (UTC)

Metal Salts

If I have elemental copper and aluminum, how can I turn them into metal salts? Alyosha (talk) 18:00, 16 May 2009 (UTC)

Copper is fairly inert stuff, but will react with water, oxygen, and carbon dioxide (slowly) in the air to form patina or verdigris. If you are looking for a more controlled reaction, it will react with concentrated nitric acid to form copper(II) nitrate salt and noxious brown nitrogen dioxide gas. Aluminum presents an interesting problem. Chemically, it is a very active metal; however aluminum forms a thin coating of Aluminum Oxide on its surface, which is fairly impervious stuff. Powdered aluminum will react MUCH faster than solid aluminum, owing to the higher surface area. However, even aluminum foil will react with any decently strong acid, say hydrochloric acid, to form aluminum chloride salts. You could also use nitric acid as above, but the production of NO2 gas is to be avoided unless absolutely necessary. Since Copper is not normally oxidized by acid (the nitrate ion in the nitric acid is the oxidizing agent here) HCl won't do much to copper. Aluminum, however, is easily oxidized by any strong enough acid, so I would go with the easier to work with HCl. --Jayron32.talk.contribs 18:39, 16 May 2009 (UTC)

I don't really have either acid, and there's no chance that I'll be able to get them. But thanks anyway! :) Alyosha (talk) 19:01, 16 May 2009 (UTC)

Then let's back up a sec here. Since you're asking (we now know) for practical advice, you'll need to tell us what your level of expertise is and (if you're just a household experimenter) what you do have available. What's your larger goal here? Is the whole point of the experiment to do this conversion? Are you wanting some specific salt? Are you wanting to use the salt for something? Are you just trying to dissolve metal? With some context and constraints, it will be much easier to provide advice that is actually useful to you. DMacks (talk) 19:07, 16 May 2009 (UTC)

I am try to create a Galvanic cell. My plan was to create the metal salts for the electrolyte solution. Alyosha (talk) 19:15, 16 May 2009 (UTC)

this is kinda complicated

this works just as well

No need to. You just need some electrolyte solution that will have material that will complete both the oxidation half and the reduction half of the reactions, and while the "classic" galvanic cell uses a set up like is in this picture, this is really only needed for quantitative studies where you want to carefully control the the concentrations of the solution to study the effect on the voltage, or something like that. If all you want is to make a simple galvanic cell, just about any acidic medium will work. If you take ANY two dissimilar metals and place them into a sufficiently resistive but acidic medium, you will generate a usable voltage. Take an iron nail and a copper nail, jam them into opposite ends of a lemon or an orange or a potato or something like that, and you will get a measurable voltage. It is usually enough to power a small liquid-crystal display, such as a watch. Google "lemon clock" or "potato clock" to get examples. Basically, the acid in the lemon and/or potato acts as the electrolyte solution for both half-cells, and the solid parts of the lemon/potato/whatever are resistive to electricity, but also semi-permiable to ions, so it also acts as the salt bridge. Its really a simple set up. So try it. Take a lemon, jam your metal parts into opposite ends, and hook it up to the leads in your watch in place of the battery. It will probably work. It will at least generate enough current to register on a simple voltmeter. --Jayron32.talk.contribs 19:56, 16 May 2009 (UTC)

Thanks.Alyosha (talk) 20:21, 16 May 2009 (UTC)

Heck yeah, we even have a lemon battery article:) DMacks (talk) 21:51, 16 May 2009 (UTC)

Everyone should build a lemon battery at some point in the lives! (It works well with any citrus fruit, but it also works with other fruits and vegetables - potatoes, even!) --Tango (talk) 22:30, 16 May 2009 (UTC)

quantum mechanics

Question for you about quantum mechanics. At Wiktionary we have a definition of: {{physics}} The branch of [[physics]] which studies [[matter]] and [[energy]] at the level of [[atom]]s and other [[elementary]] [[particle]]s, and substitutes [[probabilistic]] mechanisms for [[classical]] [[Newtonian]] ones.

I reckon we could improve the last part which says "and substitutes probabilistic mechanisms for classical Newtonian ones" into something better. Please see wikt:quantum mechanics. --Jackofclubs (talk) 18:43, 16 May 2009 (UTC)

Maybe quantum theory too - I'm not so sure on this definition. --Jackofclubs (talk) 19:54, 16 May 2009 (UTC)

Is it physically possible to rip a man's arm off with your bare hands?

Question as topic. Partially inspired by the swan question above, partially inspired by my playing of Mortal Kombat II again last night. Is this within the limits of human strength (I'm including trained musclemen/strongmen here too)? --Kurt Shaped Box (talk) 18:55, 16 May 2009 (UTC)

Sure, take a weak man or leper, it is easy. --Jackofclubs (talk) 19:13, 16 May 2009 (UTC)

Leprosy would have no effect on the ease of pulling off an arm. Such notions, and pejorative terms like "leper", have no place on the science desk. --Scray (talk) 23:24, 16 May 2009 (UTC)]]

"Leper" primarily means a person afflicted with leprosy and that useage is proper English. I see no reason to suppose Jackofclubs used "leper" with a secondary perjorative intent nor why WP:AGF is not applied here. Cuddlyable3 (talk) 14:52, 17 May 2009 (UTC)

Fair enough - thanks for pointing out that I worded that too strongly. Leprosy#Etymology does point out that this term is considered pejorative (it's got an ugly past). --Scray (talk) 20:51, 18 May 2009 (UTC)

I don't think so. Regardless of the victim's muscle strength, the ligaments around the shoulder are strong. Dislocation or fracture might occur with a lot of effort, but not avulsion. --Scray (talk) 23:28, 16 May 2009 (UTC)

I'd be surprised if it was impossible! It'd most likely take quite a bit of work and leverage, if the subject was a healthy adult, though, but if you keep yanking on that arm, sooner or later something's going to give. That's a far cry from Mortal Kombat action, of course, but still. -- Captain Disdain (talk) 01:43, 17 May 2009 (UTC)

I read a story once of a chimp ripping the arm off a person who had been tormenting it. Dmcq (talk) 13:01, 17 May 2009 (UTC)

Oh, sure, I have no trouble believing that. Chimps are in a league of their own compared to us puny humans, as this Straight Dope column entertainingly tells us. They pack serious muscle. -- Captain Disdain (talk) 14:07, 17 May 2009 (UTC)

I suppose that if you kept twisting, pulling and bracing against the torso with your leg, then it might come off eventually. Does anyone know offhand (or is able to quickly calculate) the force required to directly rip off a human arm? --Kurt Shaped Box (talk) 01:28, 19 May 2009 (UTC)

• Didn't someone's arm get ripped off in Laurence Fishburn's second CSI episode? = Mgm|^(talk) 11:57, 18 May 2009 (UTC)

Well, if it was on CSI - it must be true. :-P SteveBaker (talk) 01:25, 19 May 2009 (UTC)

If you cooked the person first, it would be a lot easier. Think Thanksgiving turkey. 65.121.141.34 (talk) 13:59, 19 May 2009 (UTC)

True. Also, if you used a meat cleaver, it would be a lot easier. Or tied the torso to concrete wall and attached a rope to the arm, and the other end of the rope to a car, and then drove away. But that wasn't the question... -- Captain Disdain (talk) 11:20, 20 May 2009 (UTC)

My suggestion follows the letter of the law, question, whatever (though probably not the intent). 65.121.141.34 (talk) 16:43, 20 May 2009 (UTC)

I guess it would also depend on whos arm youre trying to rip off. Trying to rip off John Cenas arm would be much difficult than that of Mahatma Gandhi.

Infinite Improbability

Do we live in a universe that there is is no probability of something happening (it will never happen, probability = zero), or is anything and everything is possible but the probability of it happening is infinitely small (probability = 1/infinity)? 129.21.109.153 (talk) 19:28, 16 May 2009 (UTC)

First of all you have to realize that probability = 0 doesn't mean that it can't happen. For example when you throw a dart at a dartboard, if there are infinite points then the chances of hitting exactly the center is 0, since if you 'zoom in' enough you can always see that it is not exactly the center. Still, it can happen, although the probability is 0 that it will. (1 point is the bullseye / there are infinite points total = 0)

As for your question, it is more relevant to things like location: it is true that everything can be everywhere, but that the probability for example of you turning up whole and unharmed in China in the next second is pretty close to 0 -- however it could happen, because particles don't have exact locations but probability distributions instead... —Preceding unsigned comment added by 94.27.244.146 (talk) 20:00, 16 May 2009 (UTC)

I disagree that the probability of hitting the centre of a dartboard is zero - you are assuming the dart board can by modelled as a portion of a Euclidean plane to arbitrary precision, but that isn't the case. There is a limit to how precisely you can define the centre (see Heisenberg's uncertainty principle among other things), so either you have to say that the concept of a centre of a dartboard is meaningless, so there is no probability, or the centre is a region with finite area, so there is finite (ie. non-zero) probability. --Tango (talk) 22:26, 16 May 2009 (UTC)

Or better yet, Planck length. --131.188.3.20 (talk) 00:14, 17 May 2009 (UTC)

OK that makses sense. So anything is possible then right, even if the chances are really really small? Also as a quick aside, does the probability distribution of a particle cover everwhere, or does it end with in a certain distance from the "center", or where it's most likely to be?129.21.109.153 (talk) 21:08, 16 May 2009 (UTC)

It depends on what you mean by "anything". Anything not specifically ruled out by the laws of physics is possible. It is not possible (unless our understanding of physics is incorrect, which can't be ruled out), for example, for something inside the event horizon of a black hole to leave it. It is not possible for an electron to spontaneously turn into a positron without any other particles being involved (due to conservation laws). etc. etc. --Tango (talk) 22:26, 16 May 2009 (UTC)

What I once read was that in infinite time, everything that is not absolutely impossible will happen. 78.146.17.231 (talk) 22:47, 16 May 2009 (UTC)

Will almost surely happen. That's not quite the same as "will happen", but the difference is rather subtle (and probably only really understandable to mathematicians). --Tango (talk) 00:23, 17 May 2009 (UTC)

According to one interpretation (which I personally think is ricidulous,) everything will eventually happen. See Omega Point (Tipler). -Arch dude (talk) 00:36, 17 May 2009 (UTC)

For any ergodic mesoscopoic or macroscopic system that is not "frozen out" or locked in an infinitely small part of its phase space, it is certain that the vast majority of accessible phase space will never be visited. Consider a system of N = 100 000 non-interacting distinguishable particles in a box (say, a few grams of sand in a jar aboard the International Space Station). The grains of sand are flying around at about 10 cm/s, and the jar is about 10 cm high. Probability for all the grains to momentarily find themselves on their respective sides of the midline of the jar is 2^-N. Even if we assume that the sand changes its state (i.e. any grain crosses the midline) every microsecond, which is over-optimistic to say the least, it will still take approximately 10^3x104 seconds for the sand to visit an non-negligible fraction of the possible states, and very much longer to visit all states (as nothing prevents the same state from occurring more than once). The lifetime of the universe is much, much shorter than 10^3x104 seconds. It is therefore quite meaningless to speak about everything possible happening. In fact, an infinitely small part of possibilities are ever realized, at least in statistical mechanics. --Dr Dima (talk) 02:06, 17 May 2009 (UTC)

Of course - IF the universe is finite in both space and time - then the probability of any of these crazy things happening is extremely close to zero - so close that we can be quite confident in asserting that they won't happen. However, if the universe turns out to last forever - or to be infinite in spatial extent - then no matter how improbable, all of these things are happening (or are going to happen) - not just once - but an infinite number of times. However, the probability of any human ever being able to detect one of these crazy things is still so close to zero that it might as well be. It's worth noting that we don't know for sure whether the universe is either spatially or temporally finite - so we can't be definite about the answer to this question. But infinities and one-over-infinities are tricky things to deal with and talk about. SteveBaker (talk) 02:59, 17 May 2009 (UTC)

As SteveBaker, says "infinities and one-over-infinities are tricky things to deal with and talk about" but in this case we can be pretty definite that not everything that can happen will happen, even in an eternal universe. Consider for example a machine that picks up a random real number between 0 and 1 every second for eternity. Even if run for eternity, the machine will not end up picking all of the numbers in its range; in fact, by some measure, the machine will run through almost none of the numbers between 0 and 1. ( Yes, this mathematical example can be converted to a physical thought experiment, but I won't bother to do so here.)
Of course, the basic problem is that are talking about concepts like "everything" "eternity", "infinite" without actually defining any of those terms. And it's hard impossible to answer the original question, without agreeing upon a common terminology. Abecedare (talk) 03:31, 17 May 2009 (UTC)

Werner Heisenberg, one of the founders of quantum mechanics stated The existing scientific concepts cover always only a very limited part of reality, and the other part that has not yet been understood is infinite. It is presumptuous to claim that anything or everything is not possible in that infinite part of reality. Cuddlyable3 (talk) 14:23, 17 May 2009 (UTC)

I understand all of the points that have been made, but doesn't it make sense that there is infinite time (there is...right?), then everything will happen, exist, occur, eventually. And it already has and will infinitely more times. Even when and however this universe ends then something "new" will come out of it and then that will have an entire time of existing and then it will end and something else will arise, etc. So I think that given enough time, anything and everything will occur, even if it is infinitely improbable. 129.21.109.153 (talk) 16:26, 17 May 2009 (UTC)

The universe almost certainly hasn't existed for an infinite amount of time already (current estimates put it at about 14 billion years old) and almost certainly won't exist in its current form for an infinite amount of time. There are various theories about what could happen, I think the ones that a currently thought to be most likely are heat death and Big Rip. While the universe continues to exist forever in both of those cases, it doesn't exist in a form in which much can happen (at least, it can't happen very fast - I'm not sure if activity in a heat death tends to zero fast enough to prevent infinitely many things happening). --Tango (talk) 16:48, 17 May 2009 (UTC)

Science Desk Question

This is not at all a science question, but a question about the behaviour of this desk. Has anyone noticed that when you ask or answer a question on this desk then publish it, the page appears then immediately begins to scroll up? It only happens on this desk and none of the others. What is happening and can it be fixed by someone?--KageTora - (영호 (影虎)) (talk) 22:40, 16 May 2009 (UTC)

Would be better asked at Wikipedia talk:Reference desk —Preceding unsigned comment added by 82.44.54.169 (talk) 22:44, 16 May 2009 (UTC)

I don't know if this is anything to do with what you're describing - but I've noticed that the presence of mathematical formulas on this page causes the page to scroll up or down (depending on whether they're above or below what you're reading) if you try to navigate the page while the graphics are still loading... --Kurt Shaped Box (talk) 22:53, 16 May 2009 (UTC)

When one returns to a previously viewed page, a browser tries to bring one back to the same position one last scrolled to. I suppose it confuses browsers when a page has changed due to ongoing edits at different places while one is away. Cuddlyable3 (talk) 14:04, 17 May 2009 (UTC)

I think it has something to do with images. When you edit a section on Wikipedia, you are automatically returned to that section when it reloads the page with your changes. If this section is at the bottom of a long page (such as here after you ask a new question in a new section) with images, the text may load far before the images, depending on your browser speed. As the images load, the text will be "pushed down" a certain amount. It may happen here only since we tend to have a lot of images (animal identification, graphs, diagrams, etc.)-RunningOnBrains 19:26, 17 May 2009 (UTC)

Is there any way of telling my browser not to do that? I find it mildly irritating. --Kurt Shaped Box (talk) 23:18, 17 May 2009 (UTC)

You could refuse to look at pages in which the image tags don't carry size info. —Tamfang (talk) 16:43, 18 May 2009 (UTC)

Is there any way of telling my browser to warn me before I do that, then? ;) --Kurt Shaped Box (talk) 23:46, 18 May 2009 (UTC)

TB treatment that grants immunity to lung cancer?

My grandmother says she underwent an aggressive drug treatment for tuberculosis, and that doctors told her she can never get lung cancer as a result of it, despite that she smokes daily. If drugs used to treat TB can totally prevent lung cancer, why aren't they offered to all smokers? NeonMerlin 22:51, 16 May 2009 (UTC)

I don't know the medical side of that statement. But from an ethical point of view, doctors do not want to encourage smoking. Smoking can cause all sorts of other diseases and other cancers (cancer of the mouth being one). --KageTora - (영호 (影虎)) (talk) 23:05, 16 May 2009 (UTC)

Certainly sounds like misinformation, miscommunication, misunderstanding, misremembering, or denial. My vote is on the last one. Smokers are always looking for excuses. --Scray (talk) 23:12, 16 May 2009 (UTC)

Yes, we are. And I will admit to being guilty many a time for that.--KageTora - (영호 (影虎)) (talk) 23:28, 16 May 2009 (UTC)

I don't buy it either. The treatment for TB is antibiotics. If antibiotics acted as a vaccine against lung cancer I'm pretty sure I would have heard of it. --Tango (talk) 00:38, 17 May 2009 (UTC)

As the other posters have mentioned, this is almost certainly a "no way", but it may be worthwhile to ask your grandmother exactly what the treatment was. You could then research that treatment (at an online encyclopedia perhaps!) and that might give you insight into how she got confused by what the doctor said. Quitting smoking at any age can be a boon; this kind of misinformation is helping her make an unhealthy choice. Matt Deres (talk) 14:21, 17 May 2009 (UTC)

Quitting smoking at that age (I assume she is fairly old) is rare, but my father did it at 65 - everyone was shocked because he had been a smoker for exactly 50 years. However, when quitting smoking it is best to do so gradually, as it can be a dangerous shock to the system for some people (this is not medical advice - wait for it!) so my father went on to having a cigar or two a day (max) instead of a full packet of cigarettes. He's done well, and still enjoys his cigars. It's always best to make an effort, at least. I went down from 20/day to 10/day a few years ago, and managed to even get that down to 5/day when I cam back to the UK (because it's so bloody expensive and having to go outside all the time is a PITA!). Good luck in your research!--KageTora - (영호 (影虎)) (talk) 02:19, 18 May 2009 (UTC)

There is a treatment for cancer that uses active TB. Maybe her doctor was referring to that [5]. I would be surprised if it provided immunity. [6] This study found both TB and cancer in a small number of patients. [7] 71.236.24.129 (talk) 17:32, 18 May 2009 (UTC)

Time Zones

Inspired by a question over on Misc. Desk about planes, jurisdiction, and British Licensing laws. In some ways I consider this a science question, but don't ask me what the relevance to the question on the Misc. Desk is, because it's very convoluted. How fast (or slow) would a plane have to fly through time zones (west, of course, and at the equator) for the time to remain the same, say, at 6pm? Basically, I suppose the question is asking how fast does the Earth rotate.--KageTora - (영호 (影虎)) (talk) 23:03, 16 May 2009 (UTC)

1670 km / hr (1040 mph). Dragons flight (talk) 23:55, 16 May 2009 (UTC)

That's 40,000km in 24 hours. The circumference is also 360*60=21,600 nautical miles, so the speed would be 21,600/24=900 Knots. Yo cannot do this in a commercial airliner at the equator since it's faster than the speed of sound. I find it easier to remember that 40,000km=25,000 miles=21,600nautical miles, than it is to remember the actual conversion ratios. (For miles and km, you can also remember that C=186,000 miles/sec=300,000km/sec.) -Arch dude (talk) 00:30, 17 May 2009 (UTC)

Of course, if you simply stand sufficiently close to the North Pole, you could do it yourself just by walking in a circle over the course of a day, although the time of day in the polar circles is less meaningful than elsewhere due to the strange observed behaviour of the sun. Note that since geographic time zones boundaries are set based not only on the sun's behaviour but also on national borders and other geographical features, the intervals around the equator are not perfectly evenly spaced. Whilst you would see the sun remain in the same relative position, if you kept a clock at local time and updated it each time you crossed a time zone boundary, you would not get a nice, perfectly regular update. Maelin (Talk | Contribs) 02:04, 17 May 2009 (UTC)

If it is done at a latitude where a jet plane could do it, don't forget that as it crosses the International Date Line, traveling west, the calendar date jumps forward one day. However, you must put your watch back one hour each time you cross a time zone demarcation line. You put your watch back 24 times when going around the earth. That negates the calendar jump forward. In between each putting back the watch moves forward normally, and that adds up to the actual flying time. The plane would get back the day after it started because somewhere on the trip local time passed from 11:59:59 p.m. to 00:00:00 a.m. (not necessarily at a time zone demarcation line). That would move the date forward. This would apply even if you are close to the North Pole and walking around it. – GlowWorm. —Preceding unsigned comment added by 98.21.104.80 (talk) 03:41, 17 May 2009 (UTC)

As always, Wikipedia has an article on this topic. Take a look at sun-synchronous orbit. The article geared towards satellites, because those are the most likely realistic scenario. There are a lot of variations, based on particular orbit inclinations and trajectories. You can work out the necessary velocity for a plane to do this (substitute orbital radius for Earth's radius plus altitude above sea level). Specifically, you want an orbital period to be one sidereal day as viewed from the surface of the earth; this is called a semi-synchronous orbit, and it's discussed in several articles. Nimur (talk) 04:14, 17 May 2009 (UTC)

If there were continuous land mass at the equator and no national boundaries then time zones could match the Earth's rotation which is 15 degrees of longitude per hour. Flying at the speeds calculated above could keep one at the same time in each zone. However the actual equatorial route passes over various national borders and coastlines. These are the reason for displacements of some time zone borders to east or west[8] and therefore the plane would have to vary speed correspondingly, while the average speed is as given above. AFAIK countries on the equator do not add the complication of Daylight saving time. Cuddlyable3 (talk) 13:50, 17 May 2009 (UTC)

So it would actually be quite hard, then? Oh, and thank you all for understanding that my question did not mean 'at exactly 6pm', as that would be impossible, but meant 'within a certain hour, such as 6pm-6:59pm'. Thanks for the answers.--KageTora - (영호 (影虎)) (talk) 14:47, 18 May 2009 (UTC)

If you did not need to fuel, Concorde, and many military aircraft could do it. Practically speaking however, midair refueling is not possible on the Concorde, and takes place at relatively low speed in any case. 65.121.141.34 (talk) 13:56, 19 May 2009 (UTC)