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June 26

Sucking on a button to combat dehydration?

Resolved

In the movie Cube (film), the characters are stranded without water. One of the character swallows a buttons and claims it "keeps the saliva flowing". Does this trick actually work? I have my doubts because a small pebble would work just as well as a button so if this technique really worked it would have been discovered millenniums ago and be much more well-known. Anonymous.translator (talk) 00:12, 26 June 2012 (UTC)

Army trainees on maneuvers in the desert around Fort Bliss, Texas, during WWII used to be told to suck on pebbles to allay their thirst; I used to know one such veteran who told me that. Never tried it to see how effective it is, myself. But yes, the technique is an old one, not unknown. Textorus (talk) 00:17, 26 June 2012 (UTC)

Like text says, if it allays anything, it might allay thirst. But that's not going to actually fight dehydration. It's not like your body can just make new water for the saliva. Someguy1221 (talk) 00:21, 26 June 2012 (UTC)

Wow, 5 minutes. Thanks for the quick answer, guys. Anonymous.translator (talk) 00:28, 26 June 2012 (UTC)

My old Scout Leader in the UK told us about sucking pebbles to prevent thirst on a hot day. We thought that it fell (like much of his advice) firmly into the bracket of old wives' tales. Alansplodge (talk) 00:45, 26 June 2012 (UTC)

Some more old wives here, here, here and here. Alansplodge (talk) 00:54, 26 June 2012 (UTC)

I remember reading about sucking on pebles in Baden-Powell's book Scouting For Boys when I joined the Scouts in the 1960's. This book had been published about 50 years before but was still the primary text for boy scouts (10 to 12 year olds) at that time. I think Scouting For Boys would be the original source for the pebbles advice. I don't have the book now, but I think the advice was aimed at distracting boys from wanting a drink too often while on treks (as the average boy would be accustomed to having a drink any time he liked at home), and not expected to counter genuine thirst, and certainly not dehydration. Other advice in the book was very good, as I recall (except the advice to help old ladies across streets - I tried that once and got told "piss off sonny"). Wickwack120.145.57.11 (talk) 04:10, 26 June 2012 (UTC)

Old boy, the book is scanned here and it still makes a jolly good read. It doesn't mention any "pebles" but says: "If you keep your mouth shut when walking or running, or keep a pebble in your mouth (which also makes you keep your mouth shut), you do not get thirsty as you do when you go along with your mouth open, sucking in the air and dry dust." pp. 160 Scouting for Boys. "When in the street, always be on the look-out to help women and children. A good opportunity is when they want to cross a street, or to find the way, or to call a cab or bus. If you see them, go and help them at once - and don't accept any reward." -- ibid. pp. 178 DriveByWire (talk) 17:51, 26 June 2012 (UTC)

OP, I'm interested in the verb "shallows" in your question. At first I assumed it was a typo for "swallows", but surely you weren't talking of swallowing buttons or pebbles, and the header is about sucking, not swallowing. I checked wikt: shallow but it has no meaning equivalent to "suck". Can you explain this word "shallow" to me, please? -- ♬ Jack of Oz ♬ ^{[your turn]} 19:03, 26 June 2012 (UTC)

Typo.Anonymous.translator (talk) 20:14, 26 June 2012 (UTC)

As a side note, this is how I [1] handle typos.Anonymous.translator (talk) 20:20, 26 June 2012 (UTC)

Thanks, but I still don't understand why you'd be advocating the actual swallowing - not just sucking - of small pebbles. Did you really mean physically ingesting of anything that's not food and not digestible and potentially harmful? -- ♬ Jack of Oz ♬ ^{[your turn]} 20:31, 26 June 2012 (UTC)

I tried the pebble trick as a Scout, and it did not seem to accomplish anything toward "reducing thirst." If 1,000,000 kids each picked up a pebble from the ground and walked around for a few hours with it in his mouth, how many would become ill from crud deposited on the pebble while it was on the ground, how many would accidentally get the pebble stuck in his windpipe, requiring a Heimlich maneuver or tracheotomy, like other boys who placed pebbles in the mouth to keep it moist?See also another case of a 7 year old who had a pebble held in the mouth slip into the trachea. Edison (talk) 13:25, 27 June 2012 (UTC)

Discovery of Uranium in Russia

I am withdrawing this question.

Medical treatments for "Exhaustion"

This is not a request for medical advice, but for referenced information about hospital treatments for this condition, not presently found in the relevant Wikipedia article. There are news stories from time to time about celebrities, musicians, actors, and politicians hospitalized for "exhaustion." Searching for this malady in Wikipedia, one finds a redirect to Fatigue (medical). Leaving out obvious and readily treated causes of various forms of the malady such as physical muscular fatigue (someone trying to swim 100 miles), or sleepiness after staying awake for 4 days, there remains a vague condition. I once read an article (citation not at hand) which said that ordinary people are never hospitalized for "exhaustion" as are celebrities, whose exhaustion may consist of substance abuse, eating disorders, dehydration, "burnout," stress or depression. The "exhaustion" description is sometimes said to be a public relations code word for mental health issues and substance abuse. The relevant Wikipedia article does not describe how exhaustion is treated in a hospital. Any reliably sourced info for current medical practice in treating "exhaustion" in those hospitalized for it? Edison (talk) 04:00, 26 June 2012 (UTC)

No useful answer can be given beyond "rest", as the treatment would vary enormously depending on cause and symptoms, which, as you note, vary enormously themselves. Dominus Vobisdu (talk) 04:12, 26 June 2012 (UTC)

Agreed. The only way that true exhaustion wouldn't be solved by rest is if they have a sleep disorder, and then the hospital/clinic would diagnose and treat that.

Also note that lack of sleep and substance abuse are often combined in celebrities, like Judy Garland, Marilyn Monroe, and, more recently, Micheal Jackson. They can take (or be forced to take) drugs to keep them going while filming, rehearsing a concert tour, etc. A nasty cycle can form where they take "pep pills", such as amphetamines, to stay awake, then take sleep meds to sleep, gradually upping the dose of each to counter the other. In such a case, the hospital/clinic would need to treat the drug addiction first. Then, after they recover, hopefully they can be less ambitious, and maybe do only half as many concerts or movies, or as many as they can handle in a healthy manner. StuRat (talk) 04:14, 26 June 2012 (UTC)

"Exhaustion" is a symptom, not a condition, and it would be possible to be hospitalised with that symptom while the physical cause of the exhausion is investigated. Conditions such as some endocrine disorders (hypothyroidism, myasthenia gravis) could be indicated. --TammyMoet (talk) 09:19, 26 June 2012 (UTC)

"Exhaustion" in these cases invariably means drug or alcohol abuse and its after-effects. μηδείς (talk) 17:13, 26 June 2012 (UTC)

• In the article I read years ago, a doctor or nurse asserted that a publicist may tell reporters that a celebrity was "hospitalized for exhaustion," but that within the hospital, that would not be the diagnosis, illness, or condition shown on the patient's chart, which might indocate detox from painkillers, alcohol etc, or treatment for depression. Yet our article lists diagnosis codes for "exhaustion" per se. So might a patient's chart actually indicate he is "exhausted" and so needs to be in a hospital bed for some days to become "unexhausted?" Edison (talk) 13:09, 27 June 2012 (UTC)

What are galaxies made of?

SN 1994D, a type Ia supernova in the NGC 4526 galaxy (bright spot on the lower left)

How do we know that galaxies are made of stars instead of gas? Have anyone taken a picture of a galaxy which one can see individual stars in it. The milky way does not count. If we cannot see individual stars in a picture of a galaxy what's to say that it is not made up of gas instead? Maybe it's all just gas swirling around a big black hole. 220.239.37.244 (talk) 12:42, 26 June 2012 (UTC)

Yes, we can easily resolve individual stars in many other galaxies. Up until the middle of the 1920s there was a debate, but then Edwin Hubble first identified individual stars in some near galaxies. See Great Debate (astronomy). --Stephan Schulz (talk) 13:00, 26 June 2012 (UTC)

And occasionally we see them blow up. Blakk and ekka 15:30, 26 June 2012 (UTC)

Galaxies glow; big clouds of gas do not. If galaxies did not contain lots of glowing stars, we could not see the galaxies. There are big clouds of gas and dust around which don't contain stars, and we can only detect them when the pass between us and glowing things, the light of which they obscure. -- Finlay McWalterჷTalk 13:08, 26 June 2012 (UTC)

Nebula don't glow? ScienceApe (talk) 15:16, 26 June 2012 (UTC)

Nebula only glow because there are stars in or behind them which are lighting them up. There's no know process where a large, diffuse (cold) cloud of gas by itself can sustain light output for a prolonged period of time. If galaxies outside the milky way were just gas, they wouldn't be visible, as they wouldn't be able to emit light themselves and there would be nothing behind them to illuminate them. (P.S. Galaxies are made up of both stars *and* gas.) -- 71.35.99.136 (talk) 15:36, 26 June 2012 (UTC)

Clusters of galaxies as well as large elliptical galaxies are embedded in hot tenuous gas that radiates in X-rays. This gas is hot because it's in a deep gravitational potential well (it attained its temperature through shock heating when falling into the cluster potential), not because it was heated by stars. In the early stages of galaxy formation, before stars were formed, you could imagine a potential well just being filled with (glowing) gas. The things closest to that scenario are probably Lyman-alpha blobs. --Wrongfilter (talk) 15:45, 26 June 2012 (UTC)

Well then doesn't it stand to reason that there might be a lot of gas in galaxies that we can not detect, and therefore the so called "missing mass" from galaxies does not exist, and that dark matter is probably just undetectable gas? ScienceApe (talk) 18:02, 26 June 2012 (UTC)

No, because we could detect them, due to their absorption spectrum effect on the light from the stars behind them. The missing mass must neither emit nor absorb light or other frequency on the EM spectrum. StuRat (talk) 18:07, 26 June 2012 (UTC)

It's actually not such an easy problem. The majority of astronomers don't think that gas could account for dark matter, but there is a minority who aren't sure, and the arguments are pretty difficult. Looie496 (talk) 18:18, 26 June 2012 (UTC)

The article on dark matter doesn't make any mention of gas as a possible explanation. The only alternative hypotheses it lists are to do with alternate theories of gravity. As I understand it models of galactic evolution put the bulk of dark matter in dense "halos" above the galactic plane, so if dense clouds of gas were present there, they would be easily detectable. 112.215.36.174 (talk) 10:33, 30 June 2012 (UTC)

You might want to read the articles on Uniformitarianism and Astronomical spectroscopy. We do not need to assume, but can directly observe that the laws of chemistry are the same everywhere. μηδείς (talk) 17:11, 26 June 2012 (UTC)

Why does new year start from Jan 1? Why not synchronize it to vernal equinox or winter solstice?

why is the gregorian calendar designed so that new year starts from where it starts now? wouldn't it be better if the new year started from a day more remarkable like one of the solstices or equinoxes? 117.216.157.33 (talk) 17:12, 26 June 2012 (UTC)

Well, the solstices and equinoxes aren't always on the same calendar day every year, so that would make it difficult to tell on any given year when the new year even starts. Mingmingla (talk) 17:56, 26 June 2012 (UTC)

You're saying in effect that it would not be the simplest thing in the world to convert between the Gregorian calendar and a solstice– or equinox-based calendar; but that's not a valid point against the latter. —Tamfang (talk) 20:42, 26 June 2012 (UTC)

We start the year on January because the Julian calendar, which 2,000 years ago was already the same as what we use now, except for one rule, started on January. If it were on the winter solstice, say, you couldn't say "December 2012" because then it'd be like which December 2012?, the one before the solstice or the one after? Now you could change the months to start on the equinox but why!? We've accumulated a large number of laws, records, birthdates, and holidays that would all have to be changed if we did that. You'd have to relearn everything. What day will be Christmas? NewJanuary 4th? Ultradecember 5? Halloween will be SuperOctober 10. Titanic sinks SubApril the 26th. And either the current August 21st would have to be fall or June 20th in spring, for the Northern Hemisphere, which doesn't seem right. Sagittarian Milky Way (talk) 18:04, 26 June 2012 (UTC)

Excepting all of mine, best help-desk post ever! μηδείς (talk) 03:16, 27 June 2012 (UTC)

hehe, yeah i agree on the uselessness of the excercise. but many other calendars roughly coincide with spring equinox as new year, so i thoght it might be probable that the new year was actually designed to start on winter solstice, but over time, has moved 10 days further due to various probable reasons (historical, astronomical, etc). just a thought. 117.216.157.33 (talk) 18:40, 26 June 2012 (UTC)

I don't think the new year was reckoned as starting on January 1 until the late 18th Century. It used to start on March 1. thx1138 (talk) 18:42, 26 June 2012 (UTC)

I was wrong, it's more complicated than that: Gregorian calendar#Beginning of the year. Anyway, the reason the Julian calendar originally used January 1 as the beginning of the year is because at that time, that's when Roman consuls started their terms of office. thx1138 (talk) 18:45, 26 June 2012 (UTC)

hmm, that's pretty arbitrary. too bad, I was hoping to find a more interesting answer :P

Could it be that January 1 was the winter solstice at one time in the distant past?165.212.189.187 (talk) 18:44, 26 June 2012 (UTC)

Jan 1 was once the solstice in the Julian calendar, but before there were Romans. That's only because of the Julian calendar's inability to track it well, not because it really moved that much. Sagittarian Milky Way (talk) 19:43, 26 June 2012 (UTC)

so it might not be all that arbitrary at all? 117.216.157.33 (talk) 19:59, 26 June 2012 (UTC)

my doubts are exactly the same. 117.216.157.33 (talk) 18:47, 26 June 2012 (UTC)

Just a guess, but Christmas day is on the 359th or 360th day of the year, so I'm thinking they wanted 360 "normal days", ending in Christmas, which makes for 12 months of exactly 30 days, followed by 5 extra days, at the end of the year. StuRat (talk) 18:51, 26 June 2012 (UTC)

But according to Gregorian_calendar#Beginning_of_the_year, Jan 1 was new year since 153 BC; before the tradition of christmas started. 117.216.157.33 (talk) 19:00, 26 June 2012 (UTC)

When was Saturnalia, the Roman pre-Christian festival? Maybe it had something to do with that.

Yes, they may have positioned Christmas at that time of the year, since nobody really knows when Jesus was born. StuRat (talk) 19:54, 26 June 2012 (UTC)

All these dates come in a very small range (arnd 10 days within each other); so it might be possible that some shift might have taken place either due to faulty calculation of dates or (less likely) due to some astronomical phenomena (i dunno, slowing down of earth, or whatever)

uh....::::precession....!?68.83.98.40 (talk) 04:37, 27 June 2012 (UTC)

No precession. In 12,000 years the winter constellations will be best viewed in summer and have had to have been renamed twice. Same for the other seasons. And how wrong the Western sun signs are changes by 1 day every 70 years. (Because they refuse to just rename them 1, 2, 3 and 4 after they grow out of date) But but that's about it. If the solstice is changing by 10 days in 1,000 years then one day it will be snowing in June, and your calendar is not doing it's job, not that anything's moving. (Well, it's not possible to make a perfect season tracking calendar as the eccentricity of the Earth makes the solstices and equinoxes move around a bit, but the it shouldn't ever get further from it's average date by about 21/3 days (and even that takes longer than our months have existed), plus 1¼ day if you have to wait 400 years for the all the leap days to average out like this: .

Add 1 more day inaccuracy every 3,200 years away from now due to a need for longer term leap year rules, or maybe not, this is beyond our predictive abilities). I'm pretty sure no one had thought of January yet when the Julian solstice was on January 1. Season seems to indicate that they started their year at March because it was the start of spring (when it was warm enough to make wars again, typical Romans), so that might be why the months start when they do. Rome winters end earlier than most of the Western civilization that adopted it's calendar, due to it's mediterranean climate, so I assume that's why they didn't make their seasons a little later. Maybe it's not so bad. Though Mother Nature sometimes has the nerve to make it too cold to skinny dip and sleep outside naked well into June, and it's still warm in early Sept., it's not very bright then and the long days are a part of summer too, right? Sagittarian Milky Way (talk) 20:37, 27 June 2012 (UTC)

Until recently, Christmas wasn't a big deal, unlike Easter. —Tamfang (talk) 20:42, 26 June 2012 (UTC)

If I were Pope Gregory's advisor I'd say: each month shall have 30 days until some month ends or begins on a solstice or equinox, and thereafter the sequence shall be 30 31 30 31 30 31 30 31 30 31 30 30¼. —Tamfang (talk) 20:42, 26 June 2012 (UTC)

No, because the goal was to bring the day of the vernal equinox back to when it was at the First Council of Nicea (325AD). Unless skyviewcafe.com is sufficiently inaccurate, it seems they chose the correct number of days to drop (whether Rome, Jerusalem or Nicea local mean time doesn't make a difference). What's puzzling is why it's mentioned alot that they wanted March 21 when they knew the year to less than a minute of accuracy. March 20 is closer, both in 325 and in 1582. It seems like if anything they wanted March 20. It was March 21st around 200. Maybe the current Easter rules (equinox, full moon, sunday) were developed around then? Also, how would you make a month 30¼ days long? Have it end at 6am? Sagittarian Milky Way (talk) 21:38, 26 June 2012 (UTC)

Since no one already said this: The current calendar has a month of 28¼ days, in the sense intended. —Tamfang (talk) 06:23, 2 June 2018 (UTC)

Roman calendar gives more info about older calendars. In particular, Martius/March was once the first month, as is evidenced even now by the names of September through December. The OP would have been happier then: "Roman writers claimed that their calendar was invented by Romulus, the founder of Rome around 753 BC. His version contained ten months with the vernal equinox in the first month". The insertion of January & February is attributed to Numa Pompilius.John Z (talk) 03:43, 27 June 2012 (UTC)

Note to non-classicists: septem, octo, novem, decem = 7, 8, 9, 10. QED. Ghmyrtle (talk) 13:37, 27 June 2012 (UTC)

Is it possible to make a sneaker that makes you run faster?

Topic says it all. ScienceApe (talk) 18:00, 26 June 2012 (UTC)

With little rocket engines on the back, 0.01 millimeters thick, and made of carbon nanotubes? Sagittarian Milky Way (talk) 18:07, 26 June 2012 (UTC)

Acme Corporation should have those in stock. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:55, 27 June 2012 (UTC)

It's easy. You just put some big old springs on it. There are some disadvantages to that approach, though, including an increase in the likelihood of hurting yourself. Looie496 (talk) 18:14, 26 June 2012 (UTC)

Oscar Pistorius would say yes. But the fitting process is a big problem... SemanticMantis (talk) 18:15, 26 June 2012 (UTC)

In addition to adding springs to change the impact energy (normally turned into heat) into kinetic energy, sneakers can also help you run faster by protecting you from injury. Somebody less afraid of injury will run less timidly, and somebody uninjured will also run faster. Sneakers also can get better traction on slick surfaces.

On the other hand, sneakers can keep your feet warm and moist, which is an ideal breeding ground for various nasties, which can reduce your running speed. And then there's the extra weight carried around (and accelerated then decelerated with every step). So, well-designed running shoes, which fit properly, likely increase your running speed, while cheap sneakers may even make it worse. StuRat (talk) 18:22, 26 June 2012 (UTC)

As I sit here on hold for Blockbuster Video's through the mail service, let me speculate that a good pair of well fitting sneakers will allow you to run your best (if not faster) while bad shoes will slow you down compared to bare feet. μηδείς (talk) 00:38, 27 June 2012 (UTC)

I sure I wish I had thought to say that right before you did. :-) StuRat (talk) 02:03, 27 June 2012 (UTC)

So you are about to cancel your through-the-mail account with Blockbuster as well? I have never been so disappointed. After I waited a week for it the first time, then drove it to the store to hand it in with a complaint to the clerk, they sent me the same cracked DVD a second time in a row! μηδείς (talk) 03:11, 27 June 2012 (UTC)

I have Netflix, but dropped the DVD delivery when they upped the price, and now watch streaming only. StuRat (talk) 07:17, 29 June 2012 (UTC)

I'd consider that but my computer chair is way less comfy than my TV chair. —Tamfang (talk) 06:06, 1 July 2012 (UTC)

The OP must not have seen the ads for PF Flyers in the 1960s.  :-) Bubba73 ^{You talkin' to me?} 03:03, 27 June 2012 (UTC)

http://www.rockcreek.com/vibram/flow-mens/13215.rc Count Iblis (talk) 19:25, 27 June 2012 (UTC)

This would be a fine question for the computer who wore tennis shoes. Clarityfiend (talk) 22:01, 27 June 2012 (UTC)

Rectal Swab vs Stool Test

Hello. When might a doctor order a rectal swab over a stool test? The stool test, where the patient defecates into a bag, seems more comfortable than the rectal swab, where the patient picks his rectum with a stick. Thanks in advance. --Mayfare (talk) 18:18, 26 June 2012 (UTC)

The rectal swab would provide more of a local test, while the stool sample is more of a general test of the entire digestive system. So, the rectal swab might be useful if a rectal problem is suspected (like a tear in the lining which then became infected). StuRat (talk) 18:30, 26 June 2012 (UTC)

That's not correct. First of all, a swab is a lot easier to collect than a stool sample. It's fine for detecting bacterial infections like salmonella where only a tiny sample is needed. Stool samples are needed to detect parasites, though, and usually more than one sampling is needed because the concentration of parasites is often low and they are relatively difficult to detect. The third type of test would be the test for occult blood, which requires a sample about the size of a BB. It detects bleeding anywhere in the GI tract, either from cancer or from a bleeding ulcer. Dominus Vobisdu (talk) 18:53, 26 June 2012 (UTC)

Did you say anything that conflicts with what I said ? StuRat (talk) 19:56, 26 June 2012 (UTC)

Yes. The swab does not detect localized problems, but problems with the entire digestive tract, just like the stool sample does. The difference is the kind of pathogen being tested for, with swabs working well enough with bacteria, fungi and viruses, and (multiple) stool samples being necessary for parasites.

One exception is the "scotch tape prep" for pinworms. This involves folding a two inch length of scotch tape over on itself sticky side out, sticking one side to a tongue depressor (or spoon), then sneaking into the sleeping victims room with a flashlight at about 5 am, yanking the covers off, pulling their shorts down, and touching the sticky tape firmly to the skin around their their bunghole all with lightening speed. In the lab, the tape is examinined under the microscope for pinworm eggs. The worm crawls out the butt at night and lays them there in large numbers. Dominus Vobisdu (talk) 21:44, 26 June 2012 (UTC)

Certain medical tests are meant as discouragements to would-be patients, of course. μηδείς (talk) 03:55, 27 June 2012 (UTC)

...and even more of a discouragement to nurses and interns. StuRat (talk) 03:59, 27 June 2012 (UTC)

Sodium fuel

Since sodium, as with other alkali metals, are so reactive, even to water, can we use them like gasoline (in the same way gasoline combusts) as a fuel source for cars? 64.229.5.242 (talk) 20:31, 26 June 2012 (UTC)

There are probably ways that energy could be harnessed from pure sodium. But it is unlikely that there would be a safe and efficient system for doing so, and the production of pure sodium would require much more energy than you will get out of it (sodium metal does not exist in nature, so energy would be required to convert available sodium cations to sodium metal). — Preceding unsigned comment added by 148.177.1.210 (talk) 20:34, 26 June 2012 (UTC)

Agreed. Also, if you react it with water you get a salt, which is rather corrosive, and shouldn't be released into the environment in quantity or it will kill the plants by the roads and the fish in the rivers where it ends up. StuRat (talk) 20:51, 26 June 2012 (UTC)

It's a salt but not NaCl, there's no chlorine. Hot sodium hydroxide and hydrogen maybe? Ech, even worse effluent. You could melt human flesh with that. Sagittarian Milky Way (talk) 21:42, 26 June 2012 (UTC)

Or clean your car. :) Matt Deres (talk) 22:10, 26 June 2012 (UTC)

Well it would be far more efficient to using it in a sodium battery as efficiency may be over 50% rather than a chemical reaction making heat. The above water reaction would produce hydrogen, and probably in a more compact and efficient storage form than those liquid hydrogen fueled cars.

Sodium metal, while very malleable, isn't a liquid. It would therefore be difficult to meter precisely. There are also logistical problems of refueling without causing an explosion; providing a transport mechanism from your fuel reserve to the engine; and transporting large quantities of sodium to fuel stations around the country/world . Also because it is so reactive, if any water got into your tank, boom. A little water in your gas tank is not really a problem. Gasoline is a much more stable fuel. Mythbusters tried a similar experiment with gun powder, they were unable to get it to work. Bcr666 (talk) 16:08, 1 June 2018 (UTC)

June 27

Why do dolphins kill sharks?

Why do dolphins kill sharks? — Preceding unsigned comment added by 68.83.98.40 (talk) 04:32, 27 June 2012 (UTC)

Because sharks kill dolphins. Looie496 (talk) 05:40, 27 June 2012 (UTC)

Not being a marine biologist, I'd say Looie's answer is pretty spot-on. My guess is that sharks and dolphins also compete for certain sources of food, but I may be wrong about that. Evanh2008 ^{(talk|contribs)} 05:55, 27 June 2012 (UTC)

OK, can someone point me to something saying that dolphins actually do kill sharks? Between a single dolphin and a single shark, I'd bet on the shark, though I could believe that dolphins might be able to use their intelligence to kill a shark with teamwork. --Trovatore (talk) 07:03, 27 June 2012 (UTC)

Here's something on the behaviour of bottlenose dolphins [2](bottom of page). Mikenorton (talk) 07:15, 27 June 2012 (UTC)

(e/c) I cannot speak as to reliability but per here: "The idea that dolphins will seek out sharks for undersea battle is largely incorrect. It is the unfortunate perception stemming from the 60's "Flipper" generation..." and continues from there.--Fuhghettaboutit (talk) 07:17, 27 June 2012 (UTC)

These sources [3] [4] seem to agree that dolphins rarely attack sharks. Nil Einne (talk) 07:19, 27 June 2012 (UTC) Edit: Also [5]

Interestingly, though, bottlenose dolphins are known to occasionally attack members of other species who seem to pose no obvious threat (porpoises, for example). Snow (talk) 09:29, 30 June 2012 (UTC)

What kills more dolphins: sharks or humans?165.212.189.187 (talk) 13:17, 27 June 2012 (UTC)

(Based on a more careful check of the mortality rate of dolphins from humans, I've reconsidered the answer hence the strike-out.) Considering the above sources suggest sharks don't really compete with dolphins that much, the likely answer is humans. This non-RS [6] makes the claim (edit: that humans kill more dolphins then sharks) but I don't vouch for it as it provides nothing to back up the claim, however it does mention tiger sharks, great white sharks and bull sharks as the likely shark predators of dolphins (one of the other sources mentioned tiger sharks as well). [7] claims that despite a frequent attacks by tiger sharks, the number of dolphins killed is small. (I don't know if the other source really contradicts this as it just said the person had found many dolphins in tiger sharks, the percentage may still be low.) Edit: In any case, it appears to me the mortality rate of dolphins from sharks is not that high although I don't have any specific numbers.

This will also depend on how you define 'kill'. I presume your excluding very indirect methods like overfishing. Are you including slightly less indirect methods like PCB contamination and other forms of pollution or habitat destruction? (I don't know if these are significant enough to be considered.) I presume you're including direct but inadvertent methods like deaths due to bycatch. On that point, I can't find any good non activist recent sources on overall mortality rates how what I've found suggests it's generally low. For example [8] suggests a rate of less then 5000 for those caught for the US market and [9] suggests a rate of 2600 in the eastern Pacific in 1996. You can add to that a few thousand killed by hunting, see e.g. Dolphin drive hunting. Based on this, the answer may very well be sharks in some cases although I have no idea of the mortality rate from sharks. (Definitely based on earlier rates of 100k+ humans seem hard to beat, see also [10].) Of course this does depend on the precise species of dolphin and where they live. I strongly suspect even ignoring habitat loss and degradation, many more Orcaella brevirostris are killed by humans then sharks. Nil Einne (talk) 18:48, 27 June 2012 (UTC) Edit2: Noticed we also have a Cetacean bycatch which seems to support the idea overall the numbers are low now although there may still be some at risk. Dolphin#Human threats also mentions the other threats.

While I wouldn't expect dolphins to kill large adult sharks, juvenile sharks (or adults of small species of sharks) would just be another fish they would eat. I believe the size threshold would be what the dolphins could swallow whole. StuRat (talk) 18:17, 27 June 2012 (UTC)

If humans kill more dolphins than sharks do, both directly and indirectly, then why don't dolphins kill us?165.212.189.187 (talk) 19:51, 27 June 2012 (UTC)

Because sharks have been killing dolphins for millions of years, which is enough time for dolphins to evolve an anti-shark bias, while humans have only been killing dolphins for a few thousand years. Also, if they did kill humans, it would be counter-productive, we'd just wipe them out. However, when dolphins are captured (with their families killed), held captive and forced to do tricks, like at Sea World, they do occasionally get even by killing people (although it's hard to tell if those deaths are on porpoise). Then there's the Simpson's episode where the dolphins take over the land and force all humans into the ocean. :-) StuRat (talk) 21:14, 27 June 2012 (UTC)

You do realize that didn't really happen, since it was a Halloween special? μηδείς (talk) 01:34, 28 June 2012 (UTC)

And the rest of the Simpson's, of course, is a factual documentary of their real lives. StuRat (talk) 01:46, 28 June 2012 (UTC)

Did you guys miss all the stuff up above, demonstrating that dolphins do not in fact kill sharks, at least in numbers large enough to be noticed? --Trovatore (talk) 21:21, 27 June 2012 (UTC)

And did you see Nil's 3rd link, which confirms, as I suggested, that dolphins will attack small sharks, which they don't see as dangerous ? StuRat (talk) 21:39, 27 June 2012 (UTC)

Are you referring to the link which shows that dolphins will attack certain sharks if trained by the US navy, but not large ones? If so I'm not sure that is particularly relevent. Unless I missed it, none of the links indicated there's any real evidence of dolpins regularly attacking sharks big or small. (It does demonstrate that dolphins have evolved an anti certain dangerous animals bias, but I'm not sure if Trovatore was disputing that. The bias appears to be in the form of avoiding dangerous animals rather then trying to kill them as is hardly surprising.) Nil Einne (talk) 19:34, 28 June 2012 (UTC)

Dolphins do kill humans [11] :-P (I primary mention this because a common question and one which confuses results when trying to find out dolphin mortality from humans vs sharks appears to be whether dolphins or sharks kill more humans. The answer appears to be sharks, since I only found one human death attributed to a dolphin in the wild. There are some near misses like a woman who got dragged down 100 feet and also some other results which confuse matters like people who died swimming with dolphins but where the death appears to have been natural causes. Not that sharks actually kill many people any way. BTW the other result which confuses search attempts on the dolphin mortality issues is of course dolphins occasionally saving humans.) More seriously beyond what has been said above, while dolphins are intelligent, as I mentioned above many of the mass killings in particular were from by catches so the connection to humans is rather indirect. Even if there was time to evolve, this would be to avoid nets or boats or otherwise escape from them rather then to kill humans. Note that while evolution may sometimes provide the tools to kill potential predators or other hazards, usually it also evolves towards using them sparringly. It doesn't tend to act towards killing these predators or hazards on sight, that's rarely a productive strategy. As StuRat has hinted at, it's particularly true with humans. While I'm not saying we would wipe them out, I think it's clear the idea of dolphins as cute, intelligent docile creatures you can swim with is one of the reasons people are so much more concerned with killing them then of the many, many 'killer'/'dangerous' sharks killed by humans each year. (Even if these concepts are not particularly accurate.) Nil Einne (talk) 19:55, 28 June 2012 (UTC)

Dolphins do mob sharks: Bottlenose_dolphin#Predators. μηδείς (talk) 01:33, 29 June 2012 (UTC)

Resolved

Which model of Citroën DS?

Citroën DS 21?

I saw and photographed this car in Paris earlier this month. It looks kind of neat IMO. But exactly what type of car is it? I suppose it is a Citroën DS, but this model has been manufactured in many variants. Being a car ignorant myself, could someone help me getting closer to which exact variant it is? --Slaunger (talk) 14:41, 27 June 2012 (UTC)

Looks like Citroen DS cabrio, as pictured at Citroën DS and [12]. Bazza (talk) 18:21, 27 June 2012 (UTC)

File:1974 Citroen DS23 Pallas.jpg Looks very similar to this one.--Canoe1967 (talk) 18:28, 27 June 2012 (UTC)

Thanks for the hints! I think it is some variant of the Citroen DS Cabrio. It looks very much like this DS Cabrio. But the Cabrio appears to be made with different front light systems, like this DS Cabrio. The Pallas referred to by Canoe has many similarities, but the elevated rear light system found in my photo is not on the Pallas, but seems to be on all the Cabrios found in the link provided by Bazza 7. --Slaunger (talk) 18:39, 27 June 2012 (UTC)

With help from elsewhere it has been confirmed that it is a Citroën DS 21 Cabriolet. --Slaunger (talk) 15:06, 28 June 2012 (UTC)

Resolved

BSP WASHER SIZES

IS THERE A STANDARD FOR BRITISH STANDARD PIPE THREAD WASHERS AND A TABLE OF SIZES ? — Preceding unsigned comment added by 195.74.125.225 (talk) 15:23, 27 June 2012 (UTC)

YOU MEAN THIS? OR MAYBE THIS? ←BASEBALL BUGS ^{WHAT'S UP, DOC?} CARROTS→ 19:47, 27 June 2012 (UTC)

Friction

Can anyone direct me to research regarding the ratio of static friction and kinetic friction, i.e. I am interested in $\mu _{s}:\mu _{k}$. — Fly by Night (talk) 20:04, 27 June 2012 (UTC)

I'd think the highest difference would be in a case where the surfaces actually break. For example, two sheets of sandpaper might have the sand grains ripped off when the object starts to move, greatly reducing the friction. StuRat (talk) 22:06, 27 June 2012 (UTC)

Fiddlesticks. DriveByWire (talk) 00:34, 28 June 2012 (UTC)

How about a flour avalanche in a slowly turning drum? Plasmic Physics (talk) 04:05, 28 June 2012 (UTC)

Just to reiterate my enquiry: "Can anyone direct me to research regarding…" — Fly by Night (talk) 00:01, 30 June 2012 (UTC)

I'm not aware of any, and it would really be non-sense to try and study that non-relationship. Kinetic friction is only approximated using a coefficient. In reality it should be a function of speed, and whether it is also a function of the static friction, and how the static friction contributes, is dependent on the material(s), temperature, etc. 112.215.36.174 (talk) 07:15, 30 June 2012 (UTC)

Actually, I just found one paper that claims a useful empirical relationship between the two for some mechanical engineering purpose [13]. 112.215.36.174 (talk) 07:24, 30 June 2012 (UTC)

To reiterate my answer, the bowing of a stringed instrument (violin, celllo etc.) depends on the different static and kinetic frictions of the bow against the string. Over the course of centuries empirical research into the sound produced has found the effects of typical bow materials e.g. coarse horsehair, rosin, beeswax, and lately synthetic hair. DriveByWire (talk) 12:49, 30 June 2012 (UTC)

June 28

skin flora

is mainting your skin flora helpful in preventing skin infections like mainting your vaginal flora is good?--Wrk678 (talk) 02:19, 28 June 2012 (UTC)

Yes. Specifically, killing off the skin bacteria can allow fungi to grow there. StuRat (talk) 02:26, 28 June 2012 (UTC)

The desk appreciates contributions from owners of good vaginal flora. DriveByWire (talk) 13:05, 28 June 2012 (UTC)

Wife, responding to husband who brought her flowers for no reason: "So now I suppose you expect me to spread my legs ?"

Husband: "Why, don't we have a vase ?" StuRat (talk) 07:14, 29 June 2012 (UTC)

Oh, the classics... Snow (talk) 00:32, 1 July 2012 (UTC)

trees of interest

Berberis gagnepainii thorns

is there a tree or a bush that has about 2 inch thorns on it where every leaf is. — Preceding unsigned comment added by 2602:306:CCF5:E7F0:FDBA:5660:E85A:B5BF (talk) 03:19, 28 June 2012 (UTC)

According to this site, the red hawthorn has 2-4 inch long thorns: [14], although I'm not sure how they are spaced relative to the leaves. StuRat (talk) 03:36, 28 June 2012 (UTC) I've taken the liberty of correcting the 'hawthorn' spelling to link it. Richard Avery (talk) 07:42, 28 June 2012 (UTC)

Thanks, but unfortunately that doesn't appear to be the same species. Crataegus columbiana, Crataegus chrysocarpa, and Crataegus rotundifolia were the three species listed at my link as "red hawthorn". StuRat (talk) 07:06, 29 June 2012 (UTC)

Acacia tortilis the Umbrella Thorn http://www.google.com/search?q=acacia+tortilis&num=100&hl=en&newwindow=1&safe=off&client=safari&rls=en&prmd=imvns&source=lnms&tbm=isch&sa=X&ei=b-PrT5-lFoyA6QH_k6niBQ&ved=0CPgDEPwFKAE&biw=1027&bih=739 μηδείς (talk) 04:56, 28 June 2012 (UTC)

A couple of Berberis species have decent thorns, Berberis julianae and Berberis gagnepainii, the thorns of which are pictured. Richard Avery (talk) 07:39, 28 June 2012 (UTC)

In northern Europe, the Blackthorn has the most evil thorns in town, beating the Hawthorn hands down. A friend had one punch through the sole of his work boot and I've heard of people losing eyes to them. If one gets lodged under your skin, it festers horribly. It is considered unlucky to bring blackthorn into the house the UK, apparently because it was believed to have been used for the Crown of Thorns.[15] Alansplodge (talk) 18:52, 29 June 2012 (UTC)

As an aside: Ah, Blackthorn and brass splinters ... UK chemist shops used to sell 'Yellow Basilicon Ointment -British Pharmacopoeia'. Put some of that over the afflicted part and slap on a sticky plaster and after a few days out came the festering thorn or splinter. Other than not being kosher, I don't know why it was withdrawn. These days, one's extended family often ends up having to take a trip to the doctor to have it removed and usually get presented with a prescription for antibiotics (£7.65) because it was left so long. Is that a step forward? The ingredients however, are still obtainable from artist suppliers and one's local supermarket (thankfully) but I wont give the receipt here... as its too off topic. Call me an old stick-in-the-mud but Blackthorn is a sod, because it's so long and brittle it can brake off under the skin and a 'stitch in time save nine'. --Aspro (talk) 20:02, 29 June 2012 (UTC)

Sorbothane

Can anybody familiar with this material take a look at this question on the Language reference desk? Bus stop (talk) 03:22, 28 June 2012 (UTC)

Effect of over speed test on large steam turbine (>600mw) last stage lp blades->900 mm length

As per iso standards over speed test on large(>600mw)turbine lp rotors is carried out to ensure the intigrity of rotor blade assembly and "permanent set" if any.Generally the over speed holding period is between 2 to 10 minutes as per the design requirement.Over speed run normally is carried out at 120% of the rated speed.Such over speed tests are carried out once in the life time of any rotor and not repeated. 1-It has been observed that certain manufacturers of large steam turbines do not carry out the over speed test on l P rotor (with last stage blade height >930 mm) at 120% but do it at 115% holding for two minutes. 2-In other case the above lp rotor is over speeded at 120% momentarily and the speed is brought down. the bladed lp rotor weight is about >90 mt. my questions are a-Is it detrimental to carry out over speed test-run at 120%? b-Can such over speed run for two minutes impair the blade/rotor material strength/properties? c-Such constraint in conducting over speed test and holding for two minutes--can be attributed to dynamic balancing/ over speed set up or design inadequacy? — Preceding unsigned comment added by Rwgkw81 (talk • contribs) 05:01, 28 June 2012 (UTC)

Refactored to eliminate shouting. Evanh2008 ^{(talk|contribs)} 05:08, 28 June 2012 (UTC)

Wikipedia has an article about Nondestructive testing which is the main intention here, combined with a bedding in process. The given period at given overspeed is chosen by the manufacturer to fulfil the latter process. I expect the turbine is fit to continue indefinitely at the given overspeed, but the manufacturer may be able to give a lifetime estimate based on experience. DriveByWire (talk) 12:55, 28 June 2012 (UTC)

Climate change evolution

I was talking to my grade 9 science (major in biology) teacher about a month ago, and asked if it was possible for humans, as with most other life forms, to naturally evolve to survive in the changing climate (i.e., temperatures). She said that there's not enough time for us to do so, that it would take thousands or millions of years, and the change is happening at a fast rate. However, I was watching a few Richard Dawkins videos about evolution, natural selection, etc. and he mentions that scientists had brought a species of lizards into a new island, and within decades, not millions of years, the species had changed their facial features, as well as their stomach, to adapt to the new environment and foods. So, is my teacher wrong? Could humans, along with other species, evolve in order to cope with the climate change? Thanks, 64.229.5.242 (talk) 07:13, 28 June 2012 (UTC)

Even in the most extreme models of climate change, the actual changes taking place are rather benign as far as the integrity of life is concerned. A lot of people might drown due to increased flooding, and others may starve due to crop failures, but we're not talking fireballs coming down from the sky or anything like that. What specific changes did your science teacher think you were talking about? Someguy1221 (talk) 07:26, 28 June 2012 (UTC)

[16] If humans do nothing about climate change half the currently inhabited earth could become literally too hot for humans to live in. That's still something I'd want to avoid at nearly all costs. Sagittarian Milky Way (talk) 17:54, 28 June 2012 (UTC)

If you think about it, the time between generations in organisms such as lizards is much, much shorter than in humans. Humans have to wait about 20 years to sexually mature and produce offspring, and then that offspring has to wait about 20 years to mature, whereas a lizard may have offspring after 9 months - 1 year, and that offspring can reproduce after 1 year. So 20 generations in a lizard takes 20 years, whereas in a human 20 generations takes 20 times 20 = 400 years. (I'm talking round figures here.) So humans could evolve to take account of climate change, but because their reproduction rate is so much slower than other species, it would take much longer, in which time the changes could wipe the species out. The faster reproducing species are at a greater advantage as far as evolution is concerned when it comes to adapting to rapid changes to the environment. --TammyMoet (talk) 08:38, 28 June 2012 (UTC)

It may just be that humans are already naturally evolved to adapt to climate change. Humans have evolved preconditions to produce and modify technology which can act much quicker to address stressful environmental conditions than genetic adaptation can. All that is needed is the proper resource allocation to solve the problems faced with better technologies or societal organisation. Think about it for a minute, a human without technology would die if left exposed to an English winter or the Saharan desert. It will be the other animals without technology that are to be doomed by extreme or rapid climate change. SkyMachine ⁽⁺⁺⁾ 09:04, 28 June 2012 (UTC)

Wikipedia has a featured article about Evolution. Evolution works by the selective survival of progeny that adapt best to a changed condition. Human evolution today is driven less by natural selection than by social pressures and economics. A sudden climate change that leads to widespread fatalities might be expected to favour certain inheritable human characteristics that already exist in the population but it is difficult to speculate which ones. Perhaps slim people would survive better than obese people in a sudden global warming. DriveByWire (talk) 12:42, 28 June 2012 (UTC)

People are now living quite happily in climates that are much hotter than Europe, say, will ever be even under the most pessimistic scenarios for climate change. It is the rapid change that is dangerous, and that is dangerous for the survival of societies rather than for the survival of the individual. Consequently, climate change does not actually present environmental pressure for humans to evolve biologically. This is in contrast to the lizards which had to adapt to a new environment with different food sources than what they were used to and adapted to before. That's very strong evolutionary pressure, which leads to very rapid evolution - if you can't deal with the new food, you're out. --Wrongfilter (talk) 17:03, 28 June 2012 (UTC)

Agreed, to quickly evolve a species must suffer massive fatalities (or infertility) from the condition to which they must adapt to survive. StuRat (talk) 20:01, 28 June 2012 (UTC)

The question you have to ask is, how would climate change prevent people from reaching adulthood and/or having children? Lamarckian evolution, where individuals pass on hereditary characteristics acquired during life is a fallacy - evolution is essentially driven by premature death. My guess as to the biggest climate change driven force would be the increased prevalence of tropical diseases such as malaria, with them extending into areas and populations previously unaffected. As said above, humans reproduce (and therefore the species evolves) very slowly however. LukeSurl ^{t c} 00:54, 29 June 2012 (UTC)

Actually, there seems to be some support for a very minor effect similar to what Lamark proposed. There was a study showing that the descendents of people who had suffered malnutrition (in Norway ?) had altered DNA. It seems that periods of starvation cause one's descendents to put on more weight, when the opportunity arises.

As for malaria, yes, that is a major killer, and humans have evolved a response, in the sickle cell gene, which might become more prevalent as malaria spreads. StuRat (talk) 06:59, 29 June 2012 (UTC)

I'd say your teacher has oversimplified matters a bit. In fact, there are occasions in which organisms with complexity equatable to that of a human have, in the context of a drastic environmental change, develop highly efficient adaptations within a handful of generations, and some of these are quite transformative to the species and it's interaction with it's surrounding ecology. As others have noted above, there are limiting factors -- the relative length of the human life cycle (less overall individuals and thus less occurrences of random mutations to generate traits that will be selected for as favourable) and our tendency towards developing technical solutions to problems -- though that second one could be viewed as an adaptation to the changing environment as well, since, if we solve the problem through technical means, it is (speculatively) possible that technical inclination might have been selected for. But I gather when you say "adapt" you mean specifically overt physiological changes, like different profiles and body sizes, increased water retention, adaptations of the eyes to deal with glare or the ability to mentally enslave giant sandworms. While these types of changes (bar maybe one or two of the examples) can occur (and indeed, as has been suggested above, some of these traits might exist in a sub-portion of the general population as genes just waiting for a big break like this), the long and the short of it is this - we just don't know. Short of actually going there, we can't be absolutely positive about what traits might be selected for, nor what new changes to genomes might occur.

If the underlying question for your inquiry boils down to "Can we count on just adapting on time?" then the answer is no; even at an absolute most "optimistic" appraisal of how much we could physiologically adapt in the next few centuries (barring directed genetic manipulation, which is certainly not just the stuff of sci-fi as it used to be, but is a whole other can of worms), we could not change enough to avoid the significant fallout of a genuine global ecological collapse and colossal numbers of people would suffer and die. You must also take into account that evolution is a balancing act: organisms make trade-offs, in the theoretically sense, for new adaptations. They may necessitate a higher consumption rate of resources, influence life cycles, or otherwise inchworm us away from other adaptations that may have proven more beneficial in the long run. Lastly, you must consider the context -- it's not just the individual organism's (or even the individual species') ability to cope with a different temperature or do with less of increasingly scarce resources that matter. In the event of severe food shortages, societal cohesion would suffer and our ability to affect novel new technical solutions -- or even to sustain the stop-gap measures and normal application of technology that we already posses -- would be greatly diminished. Likewise, in the event of widespread environmental collapse, both natural selection and technical ingenuity can only go so far in countering the effects of mass extinctions. Even if a majority of species find ways to adapt, the inability of a few keystone species to do so could none-the-less cause the collapse of entire food-chains. So finding technical solutions to avoid such rapid changes is definitely a more secure approach to the problem than hoping for slightly more advantageous perspiration rates or what-have-you. Although it would be fun to ride a giant sandworm... Long live the fighters! Snow (talk) 08:55, 30 June 2012 (UTC)

The question is actually pretty irrelevant:

• We know humans can survive much higher temperatures than many regions ever experience.^[17]

• Humans have actually "de-adapted" to the weather, with many being practically dependent on air conditioning even in mild climates like we have in the northern U.S.

• It's not the heat that will kill you, it's having your farmland turn into desert.^[18]

That said, I would agree that in a comparatively short term (10-20 generations) you can see many effective adaptations in experimental populations. A 200-400 year timeline is compatible with global warming; by the end of that time, I suppose, there won't be any fossil fuel left to burn and there will have been some very remarkable changes. If those changes can be survived, they will be survived, by people with some degree of genetic advantage. Note that populations in Africa, which have the largest reservoir of genetic variation, will likely do better at this if the most extreme case is tested than Caucasion, Asian, and Native American populations which were adapted for thousands of years to high cold terrain and now have fewer alleles to work with.

In addition to this, epigenetic changes may or may not help humans adapt to the change faster. My guess is that they will do so very effectively, because this isn't the Earth's first rodeo where global climate change is concerned. The epigenetic changes may help both for children to inherit and build on key regulatory responses by adults, and potentially, might even make the genes involved more prone to mutation (e.g. transitions at methylcytosine; I also still have my suspicions about repeat element insertions).

Genetic engineering might also be a factor. We know that some species maintain a higher body temperature than humans, and adapting proteins to survive higher temperatures is pretty standard biotechnology by now. It is conceivable that in the future, for example, a sperm sample could be run through a machine, coherent terahertz radiation could be used to identify the sperm carrying only ten or fifteen of the preferred thermostable alleles, and only those used for breeding. Or, a more active approach of altering the genes directly could be perfected. All this and much more will probably occur long before things start getting hot, until you have people running around with body temperatures of 45 Celsius.

All that said, if the heating causes methane clathrates at the bottom of the ocean to rapidly bubble up, and the methane further enhances global warming, and hydrogen sulfide starts getting released from the heat, and we start seeing a Permian extinction going on, then the Earth could be a very hostile and alien planet by the time it's over. And there's even a theoretical point, I think, where the tropical oceans could start boiling, the steam absorbs more infrared, and the Earth goes the way of Venus. Over billions of years the Sun gets hotter and hotter - it's only a matter of time until it does anyway. I haven't looked into the current status of such speculations, which I assume are difficult to assess because there is no past data we can extrapolate from. Wnt (talk) 14:11, 30 June 2012 (UTC)

Resistivity of plastic cover to heat in presence of water

WHEN A PLASTIC COVER FILLED WITH WATER, HELD TIGHTLY AT THE OPENING OF THE COVER[AT THE TOP] AND IF THAT COVER IS EXPOSED TO HEAT WHETHER THE HEAT SOURCE MAY BE ANYTHING THE PLASTIC COVER MAY NOT DAMAGE NOTHING HAPPENS TO THE COVER..........,,,WHY ? WHY ? WHY ???????? — Preceding unsigned comment added by Madhu Sagar (talk • contribs) 10:48, 28 June 2012 (UTC)

Please note that typing all in capitals is like shouting - it is bad manners. In any case, what you have written is poor english and I cannot work out what it is you are asking. You may like to clarify. Wickwack120.145.74.189 (talk) 11:35, 28 June 2012 (UTC)

The water is absorbing the heat and pulling it away from the container fast enough that it can't get hot enough to burn. A common example is using a candle to boil water in a paper cup. 209.131.76.183 (talk) 11:58, 28 June 2012 (UTC)

It's the same with paper. Just Google "paper kettle instructions", or see here for a paper frying pan.--Shantavira|^{feed me} 11:19, 29 June 2012 (UTC)

Where was the first ever plastic bag ban implemented?

After asking all these questions about plastic bags bans, I was wondering, once and for all, where was the first plastic bag ban in the world implemented? I know that San Francisco was the first American city to ban such bags, and Bangladesh was the first country to do so, but where was the first ever such ban implemented? Was it Bangladesh, a small village in Australia, or somewhere else? Narutolovehinata5 ^tccsdnew 11:24, 28 June 2012 (UTC)

"Ireland began charging 19 cents for each single-use plastic bag taken at the checkout in 2002, reducing consumption by 95% and raising millions of dollars for environmental programs. In 2001, Taiwan instituted a 3-cent fee and reduced single-use bag consumption by 69%. In 2002, floods caused by plastic bags choking drainage systems led Bangladesh to ban plastic bags entirely." from http://plasticbaglaws.org/wordpress/wp-content/uploads/2010/02/The-Evolution-of-SFs-Plastic-Bag-Ban.pdf --Canoe1967 (talk) 19:17, 28 June 2012 (UTC)

As noted above by Canoe1967, it seems that the first total ban was Bangladesh in 2002. See Top 5 places with plastic bag bans. Coles Bay, Tasmania gets a mention here. National Geographic article here, Plastic-Bag Bans Gaining Momentum Around the World. See also the only 3 weeks old WP page, Phase-out of lightweight plastic bags - 220 of ^Borg 05:53, 30 June 2012 (UTC)

12th Century people in 21st Century times

I remember watching a scene in the film Just Visiting where the two 12th century characters were vomiting in a car, saying that it was going too fast. I was just wondering if the 12th century people were time traveled to today, what shocks to the system whould they experience medically, psychologically, etc.? Reticuli88 (talk) 18:33, 28 June 2012 (UTC)

They would have no immunity to many current diseases and would likely be carrying a few, as well as lice and worms, themselves. μηδείς (talk) 19:51, 28 June 2012 (UTC)

what kind of worms? Reticuli88 (talk) 19:57, 28 June 2012 (UTC)

Cestoda - tape worms. --Tagishsimon (talk) 19:59, 28 June 2012 (UTC)

Psychologically, culture shock is the relevant concept. 12th century to 21st century will be far more extreme than our article suggests, quite possibly to the point of being functionally debilitating. — Lomn 20:12, 28 June 2012 (UTC)

They would be psychologically disturbed by the fact that everyone else would say they smelt bad. HiLo48 (talk) 20:22, 28 June 2012 (UTC)

It's highly unlikely they would understand what people are telling them. Is there any current language that is mutually intelligible with it's 12th century "ancestor"? Roger (talk) 20:39, 28 June 2012 (UTC)

Church Latin is a good bet. --Carnildo (talk) 01:00, 29 June 2012 (UTC)

How about danish? Plasmic Physics (talk) 03:34, 29 June 2012 (UTC)

Icelandic, maybe. -- ♬ Jack of Oz ♬ ^{[your turn]} 04:50, 29 June 2012 (UTC)

Hebrew. 112.215.36.174 (talk) 07:39, 30 June 2012 (UTC)

Well, in the movie, a car moving at 20 miles/hr was too much for them and kept telling the driver "too fast" while barfing, providing comedy relief for the movie. I wondered would that happen to someone in reality if they were never in a car before? Also, the culture shock thing was referenced in the movie, when the two characters stepped out into a busy city street. They were overcome with the noise and the movements because they could not comprehend what was happening and ran to the nearest shelter to hide. Another scene was when they approached a modern toilet. One of the characters thought of it as a wash bowl and promplty washed his face with toilet water.

I wonder what would happen if someone transplanted us to 700 years from now and how we would be 'shocked' or what behaviors or mannerism would be considered backward or old fashioned, etc. Reticuli88 (talk) 21:23, 28 June 2012 (UTC)

A horse at full gallop can run well over 20 mph, and they had horses then, right? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:47, 29 June 2012 (UTC)

There would be some rough real-world parallels - Uncontacted peoples are generally expected to be living a stone age-like existence. There will be records of what happens when first contact with between the outside world and these isolated tribes occurs. That said, such peoples don't get transported to "very modern" urban environments such as Chicago. LukeSurl ^{t c} 00:41, 29 June 2012 (UTC)

A hint of what it might be like is sometimes made public when someone awakens from a coma after several years. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:47, 29 June 2012 (UTC)

The behaviour of the visitor from the past would resemble that of this rat but with (hopefully) some ability to empathise and adjust. DriveByWire (talk) 15:23, 29 June 2012 (UTC)

May I recommend the French film Les Visiteurs which has exactly this scenario. Tres drole. Alansplodge (talk) 18:26, 29 June 2012 (UTC)

D'oh! I've just seen that the film you linked is a Hollywood remake of the French original. I still recommend it though - US remakes of French films are always a bit poor in comparison. Alansplodge (talk) 18:40, 29 June 2012 (UTC)

recent xkcd cartoon. SCNR Уга-уга12 (talk) 19:34, 29 June 2012 (UTC)

Evolution

Non-question removed. Please don't use the reference desk as a forum to post links for the purpose of general discussion.112.215.36.172 (talk) 04:48, 29 June 2012 (UTC)

Link to the deletion: [19]. Buddy431 (talk) 00:16, 30 June 2012 (UTC)

Cost of interstellar colonization

I'm trying to understand the construction cost assumptions in Ceyssens et al (2011) relative to the much more rigorous Moir and Barr (2005) which doesn't discuss construction costs, only acceleration costs. Assuming a sleeper ship is more economical than a generation world ship in this case, are Ceyssens' estimates unreasonably high? 75.166.192.187 (talk) 22:22, 28 June 2012 (UTC)

I'm not familiar with the papers you cited (I will look into them), but isn't estimating the cost of a sleeper ship kind of difficult given that they don't actually exist? A generation world ship is, roughly speaking, plausible with our current level of technology. Sleeper ships are a whole nother deal, and to my knowledge actually getting one up and running would be contingent on some unforeseeable advancement in cryonics, the cost of which is surely incalculable (in the true sense of that word, not the "really, really big" sense). Evanh2008 ^{(talk|contribs)} 03:24, 29 June 2012 (UTC)

I don't think so. The capacity of vitrification freezers increases at a fairly constant rate. We can make assumptions such as that suspending and reviving someone would generally require an anesthesiologist and a couple clinicians on hand, except for the first people revived, which would have to be done by robot. I think the biggest expense is for the landing craft. 75.166.192.187 (talk) 04:55, 29 June 2012 (UTC)

And another option is the have the vast majority of the crew in stasis, while a small crew, perhaps multi-generational, maintains the ship. Or, instead of one group of people kept awake permanently, you could wake each person in stasis, for maybe a 1 year maintenance shift, then put them back under. StuRat (talk) 06:28, 29 June 2012 (UTC)

For voyages on the order of 50,000 years, I think everyone is going to want to sleep through them in stasis. 75.166.192.187 (talk) 06:39, 29 June 2012 (UTC)

Another reason to wake occasionally is that the stasis won't be quite perfect, and waking them would allow their body to repair accumulated damage from gamma rays, etc. StuRat (talk) 06:48, 29 June 2012 (UTC)

Also, having the entire crew in stasis, perhaps even frozen in liquid helium where the human body becomes far more hardy, you could accelerate the ship at rates that would kill an unfrozen human. As for coming out of stasis to repair damage, even with future technology the act of freezing/unfreezing may still cause far more damage than the inbetween. Someguy1221 (talk) 06:51, 29 June 2012 (UTC)

I agree with waking occasionally, on systems alarm or timer if all clear, to measure health and radiation exposure (which you would want to minimize with asteroid rubble shielding) because nobody will have ever been in stasis for that long. Primary power would probably be aneutronic fusion but a sleeper ship could probably work on hydrocarbon fuels. The difference would be how fast it could accelerate. However, I'm not sure how much of a difference that would actually be, because propellant is limited in both cases. I am not sure about the radiation/acceleration trade-off. Slow acceleration over lengthy periods of time can indeed achieve impressive speeds, but you need almost the same amount of propellant to slow down at the other endpoint. The optimization problem is probably about the same with and without the relativistic component. 75.166.192.187 (talk) 18:05, 29 June 2012 (UTC)

I don't think the acceleration rate would be much of a problem. The ship could accelerate at 1 g for around a year to get close to the speed of light, then cruise weightless, and again decelerate at about 1g for another year at the end. You could accelerate faster, but that would require bigger engines, and more fuel, etc., and only save a few months off your 50,000 year trip, and make any humans who are awoken early during an emergency unable to move, so it seems like a bad idea. StuRat (talk) 04:18, 30 June 2012 (UTC)

You're forgetting the relativistic effects. It only shaves a few months off the journey from the point of view of someone staying behind on Earth. From the point of view of someone on the ship, a 50,000 light year journey done by accelerating at 1g for the first 25,000 light years and then decelerating at 1g for the second 25,000 light years would only take only 21 years (it takes 50,037 years from the point of view of someone on Earth). Increase the acceleration to 2g and it only takes 11 years. See Space travel using constant acceleration and the calculator on the linked page (it's not a very good article, but the facts are right). If you can sustain accelerations of 1g or so indefinately, and can create a ship that can survive travelling through the interstellar medium at relativistic speeds (from the ship's point of view, it is getting bombarded by high energy particles constantly), then for the traveller journeys can be pretty short (a million light years at 1g only takes 27 years). Unfortunately, creating a ship that can do all that would be very difficult, so you're likely to have to travel at non-relativistic speeds. --Tango (talk) 14:01, 30 June 2012 (UTC)

But there's little diff between 11 years and 21 years, if you are in stasis at the time. And doubling the size of the engines to get 2g might not be practical. StuRat (talk) 20:16, 30 June 2012 (UTC)

Closer to 0.01 g for something on the order of months, I would think. I'll raise the question again when I get some decent mass estimates for what the generation ship people say they would need to end up with. Designing the beaching yachts is difficult. Being able to refuel and move on to a secondary destination undetected is a must. 75.166.192.187 (talk) 18:18, 30 June 2012 (UTC)

Undetected by whom? If there are alien civilisations capable of detecting you, then I would think making contact would be a primary goal of the mission. And where are you planning to refuel? I think you would be better off going directly to your destination. There isn't likely to be another system en route without going a long way off course. --Tango (talk) 18:39, 30 June 2012 (UTC)

There are some civilizations you would want to wait before establishing contact with. Unstable civilizations, well, you might want to buzz them and turn off their nukes, but not much else. 75.166.192.187 (talk) 19:07, 30 June 2012 (UTC)

What civilisations are you wanting to wait before contacting? If you mean primitive ones (ie. a Star Trek style prime directive), then they won't be able to detect you anyway. You wouldn't go to an inhabited planet to refuel, there are plenty of better places in a solar system (without the big gravity well of an Earth-sized planet). If you want to stay undetected, you only have to worry about space-faring civilisations (or, perhaps, ones with big ground-based radio telescopes). --Tango (talk) 23:05, 30 June 2012 (UTC)

There is a science-fiction short story by A. E. van Vogt called "Far Centaurus" that explores precisely this idea. There are four crew-members who each get woken up for a few hours every 50 years or so to monitor the systems. It also points out the big problem with such long journeys (in the story, I think it was 300 years, but the problem would be much greater for a 50,000 year journey). It's a really good story, so if you don't want to know the plot twist, stop reading now! They get overtaken by faster craft that were invented during their journey and arrive to discover an entire colony has been established. --Tango (talk) 22:46, 29 June 2012 (UTC)

Why is that a problem? Is that not the optimal outcome for the colonists, and would yield them professorships of history at the colony's universities? 75.166.192.187 (talk) 18:13, 30 June 2012 (UTC)

Their goal was to be the first to get there and they failed (they weren't colonists, they were just a small team of explorers). It meant their mission was pointless. If they just wanted to visit the future, they could have gone into stasis on Earth. --Tango (talk) 18:39, 30 June 2012 (UTC)

From the colony backers' point of view, a soft landing is a sub-optimal success with flying colors. There is no reason that the faster ship shouldn't be able to send a skiff to pick up the passengers, or simply bring the slower ship in tow. 75.166.192.187 (talk) 19:12, 30 June 2012 (UTC)

But what is the benefit of sending the slower craft if it is likely to get overtaken? You are better off just waiting until you've invented a faster craft. --Tango (talk) 23:05, 30 June 2012 (UTC)

And that's why I haven't bought a new computer since IBM 5100. 112.215.36.172 (talk) 00:44, 1 July 2012 (UTC)

Clearly, humans are not suitable to colonize the galaxy, this will be done by machines. Self replicating machines will travel from one solar system to the next, making copies of themselves using solar energy and the materials they find. If the time to travel from one solar system to the next and to get ready to move away from there, is 1000 years, then the entire galaxy will be colonized in about 1000 Log(10^100)/Log(3) years = about 210,000 years (the galaxy is approximately a flat disk, so you can model the colonization process as an exponential growth where in each step you can move to 4 neighboring solar systems, one of which is where you came form, so 3 new places to move to). The entrire energy output of all the stars in the solar systems in the galaxy will be available to this huge machine civilization. Count Iblis (talk) 23:14, 29 June 2012 (UTC)

Then why haven't machines from elsewhere gotten here? Bubba73 ^{You talkin' to me?} 06:52, 30 June 2012 (UTC)

See Fermi paradox. (WP:WHAAOE) --Tango (talk) 07:55, 30 June 2012 (UTC)

I strongly disagree. Humans are the original von Neumann machines on this planet, and therefore the most suited to explore. Robot probes will seem quaint with another decade of telescopy. 75.166.192.187 (talk) 18:13, 30 June 2012 (UTC)

So either technological civilizations are very rare or that type of colonization of the galaxy isn't feasible. I'd put my money on the latter. Bubba73 ^{You talkin' to me?} 18:16, 30 June 2012 (UTC)

Best estimates are that technological civilizations are separated by about 5,000 light years on average, not counting colonies. However, the most discriminate factor in expanded Drake equations at present is the proportion of planets with the right amount of water to support surface life, so we should be looking for exoplanet ozone. 75.166.192.187 (talk) 18:37, 30 June 2012 (UTC)

How many would that be in our galaxy? Bubba73 ^{You talkin' to me?} 19:34, 30 June 2012 (UTC)

About fifteen. 75.166.192.187 (talk) 21:41, 30 June 2012 (UTC)

Those "best estimates" are worthless, based on fabricated numbers. We have no real data to support any estimate of that sort. "Humans are the original von Neumann machines on this planet, and therefore the most suited to explore" is a bizarre statement. Humans are not the original von Neumann machines on this planet, and are obviously incredibly ill suited to extraterrestrial travel. -- BenRG (talk) 22:24, 30 June 2012 (UTC)

Indeed, we don't really have any estimates worth calling "best". We do, at least, now know that planets are commonplace and habitable planets are very likely to be commonplace (which is a start - we didn't even know that 10 years ago). We still only have one data point for determining how likely it is for life to arise and, if life does arise, how likely it is for a technological civilisation to arise. One data point is enough to conclude precisely nothing (although taking the Earth at different points in its history as separate data points can give us something - the speed with which life arose on Earth after the oceans formed is suggestive of a very high probability of it happening, the very long period before multicellular life arose, though, suggests that is less likely). We don't even have one data point for what I consider to be the most significant factor, which is how long technological civilisations exist for (and, therefore, how likely there are to overlap). We know it is possible for a civilisation capable of radio communication to exist for a hundred years, but that's all we know. It could be that such civilisations usually wipe themselves out within a few decades (and we've just been lucky) or it could be that such civilisations tend to exist indefinitely once they arise. We have no way to know, and that makes a really big difference to any estimate of how many civilisations we may be able to find out there. --Tango (talk) 23:05, 30 June 2012 (UTC)

And you can't do statistics with one data point. And we should exclude ourselves at any rate. Bubba73 ^{You talkin' to me?} 23:10, 30 June 2012 (UTC)

It could be that machine civilizations degenerate over time, losing the capability to coordinate things on a large scale. If we become robots in the future, then we can travel by uploading our brains from one machine to another machine. So, we don't need spacecraft to travel, we simply travel at the speed of light by radio communication. Some individuals will want to make copies of themselves, and if this is not limited in some way, the person who is inclined to make the most copies will dominate the civilization. The question is then how one should police against people making copies of themselves so that the integrity of the machine civilization is maintained on the long run... Count Iblis (talk) 00:03, 1 July 2012 (UTC)

Hypothetically, if machines are going to colonize the galaxy, then I wonder which planets / moons they would prefer? In terms of building durable, long-lasting technology there would seem to be some real advantages to avoiding both weather and biological life. Robots, at least the simple ones that humans have been able to make, tend to operate best is simple and predictable environments. A robot colonist first arriving in the solar system might well think that the Moon or Mars is a more inviting first stop than a place like Earth. Engineers motivated by "moral" concerns might even tell the robots to always avoid planets (or even whole systems) with biological life. Dragons flight (talk) 23:57, 30 June 2012 (UTC)

June 29

Rat poison

I have a pretty severe rat infestation in my house. The rats seem to mostly live in my roof and just come down to eat food. I've tried using warfarin based poisons to kill them. I placed them inside the roof through the manhole. The baits get eaten completely, but the rats don't die. The amount of poison I have placed up there has been up to 1kg of 0.105% warfarin. Essentially all of it was gone within a week but the rats were not. It's possible that the rats are warfarin resistant, but there's no other options at the local shops here. I'm thinking of taking a cereal and potassium cyanide and mixing together with honey to bind it and placing that in the roof. I don't have any pets or children. Would this be an effective mixture for erradicating my rats? 112.215.36.172 (talk) 04:42, 29 June 2012 (UTC)

Try calcium phosphide, it isn't so much a poison really, but it works, unless the calcium phosphide is past it's best before date. On contact with acid, like stomach acid, it produces diphosphane, which is spontaneously combustable. Essentially, it turns a rat crispy on the inside. Plasmic Physics (talk) 05:27, 29 June 2012 (UTC)

Can I mix that with cereal and honey as I was going to do with the cyanide? 112.215.36.177 (talk) 06:11, 29 June 2012 (UTC)

Dealing with mice, I've found glue traps to be effective, although not at all humane (they rip their faces off trying to escape). If they make rat-sized glue boards, I'd try those. StuRat (talk) 05:32, 29 June 2012 (UTC)

Rat glue is available here, but I don't really know how to dispose of a live rat glued to a plate. I checked the instructions and their silence on the matter is telling. 112.215.36.177 (talk) 06:11, 29 June 2012 (UTC)

I'm guessing a high-tech euthanasia device is the preferred solution to that (*ahem*) sticky situation. Evanh2008 ^{(talk|contribs)} 06:16, 29 June 2012 (UTC)

For mice, I used one of those grabber thingies to get hold of the edge of the glue board, then put it in the sink and drowned it (had to hold it under with the grabby thing). If the rat is too big for that, drag it into a trash bag, take it outside, and crush it with a cinder block. Then toss it in the trash, or bury it if dead animals aren't allowed in the trash. Or, you could just let it die and rot in the attic, the smell will likely mostly go up and out. StuRat (talk) 06:22, 29 June 2012 (UTC)

What if the bait in the rat glue is also poison? Then it will die and I can just throw it away. Would that work? I'm also having trouble imagining how I would get a plate with a rat down from in the roof. I don't have an attic, just a crawl space so no lighting and very little room to move. The man hole is only about 1.5sqr feet, no fixed stairs or ladder and the drop is about 3m to the floor.112.215.36.177 (talk)

You could also shoot it on the glue board, perhaps a BB gun would work. Once you have it in the garbage bag (you might want to double bag it), just tie it shut and drop it down. Note that with poison they often die in really bad places, like in the walls, where they smell up the entire house. Or, worse yet, they can stagger into your living area, bleeding profusely. StuRat (talk) 06:41, 29 June 2012 (UTC)

This word count on the posts so far shows infestation by rodents:

• rat : 16
• man: 3

DriveByWire (talk) 15:03, 29 June 2012 (UTC)

Do you have any access to sodium azide-based pesticides? In sufficient quantity, the water-dissolved form should kill essentially anything. But given that, there may be restrictions on its use in your area, due to the potential for environmental contamination. If you are legally permitted to use it, simply spraying it on the glued rat should kill it, of course being very careful not to get it on yourself. Someguy1221 (talk) 06:29, 29 June 2012 (UTC)

I don't know of any sodium azide containing products that I have at my disposal. There's litterally piles of cyandide at the gold mine where I work, so I thought that would be the obvious choice. I also don't know where I would get the calcium phosphide mentioned above, but it sounds like it would allow me to not bother getting the corpses out of the roof, which is an advantage. I suppose the most important question is whether mixing any of these things with honey is going to liberate a toxic gas and kill me, or will it remain solid until the rat digests it. 112.215.36.177 (talk) 06:47, 29 June 2012 (UTC)

This is why we have professionals.--Shantavira|^{feed me} 11:47, 29 June 2012 (UTC)

The dangers of amateur poison warfarin' make one sigh an' hide. DriveByWire (talk) 15:15, 29 June 2012 (UTC)

Let me point out that the OP geolocates to Jakarta, Indonesia. I doubt that many people here are qualified to give advice on getting rid of rats in a place like that, especially not knowing the setting of the house in question. And in any case I certainly wouldn't give advice to anybody who starts talking about using cyanide. Looie496 (talk) 15:54, 29 June 2012 (UTC)

I would be interested to know which mining company would allow people to walk off site with cyanide in what looks like South Sulawesi. We live in a rat-rich tropical environment and our house sometimes has guests in the roof spaces. We don't do anything to control them other than figure out how they get up there and cut any tree branches etc they use, allow cats into the house and allow any rat snakes we see to stick around. It's pretty effective. Sean.hoyland - talk 17:15, 29 June 2012 (UTC)

I'm on holiday in Bali right now, but I live in Australia. Unfortunately, if rats are next door, which I'm pretty certain they are, then they will just walk accross the ground to my house. Mining companies that use cyanide for gold leaching do not keep it very secure as a general statement about the industry. Obviously I'm not going to say who I work for, but it's literally sprayed around the place in heap leaches. I don't know why me saying that I thought cyanide might work would stop people from giving me advice. Wikipedia lists it as a rodenticide, and if it really is a terrible idea, shouldn't you want to advise against it? 112.215.36.174 (talk) 03:41, 30 June 2012 (UTC)

Cheese with Polonium 210 Count Iblis (talk) 18:15, 29 June 2012 (UTC)

My experience has been that cheese is some sort of miracle rodent bait only in cartoons. Peanut butter is much more effective in real life. Evanh2008 ^{(talk|contribs)} 01:35, 30 June 2012 (UTC)

A rat trap with peanut butter, yes; or with a bit of bacon or some other meat firmly tied on to the trigger. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:49, 30 June 2012 (UTC)

Using cyanide doesn't seem like such a good idea. The rats will taste just a little bit of the food and notice they become sick. And if one of them dies shortly after having eaten from a new food source, the others might be smart enough to avoid eating from that same food source. That's the reason for using slowly-acting poisons like warfarin. Icek (talk) 09:06, 30 June 2012 (UTC)

I don't like all this poison stuff. If you end up killing yourself with it, it looks bad for humanity versus ratkind in the global intelligence ranking. Not to mention that you'll have dead rats in your walls, getting ... juicy. Why not use a good old fashioned rat trap? Or a glue trap - apparently they still work for rats, and it has the added benefit of often providing you the live rat for ... wherever your imagination takes you. Or countless other mechanical options. Wnt (talk) 18:14, 30 June 2012 (UTC)

Glue boards have another advantage, in that most rodents start squeaking when they get trapped, providing their own alarm. That allows you to dispose of them before they die and start to rot. StuRat (talk) 20:09, 30 June 2012 (UTC)

iodine reacting with titanium

A few months back I posted this

"I have a titanium mug/cup. After drinking some milk I forgot to rinse it out and it sat and became gross. I decided to add some tincture of iodine along with some water to help sanitize the cup. After adding this in letting it sit for about a minute it changed color and started a foul smell that made my nose sting. Is it possible it reacted with titanium to release some sort of harmful gas or substance? — Preceding unsigned comment added by 64.38.198.61 (talk) 00:08, 4 March 2012 (UTC)

The elemental iodine (I2) is probably reacting with the titanium in the same way it reacts with aluminium. The product of that reaction would be titanium iodide, which is a very soluble salt, but it would also generate heat which volatilises some of the remaining elemental iodine. That stuff's not very nice to breath in. 203.27.72.5 (talk) 00:55, 4 March 2012 (UTC)

According to the titanium alloy article, titanium is usually alloyed with aluminium anyway. The reaction between iodine and aluminium is very spontaneous and can result in iodine vapor. 203.27.72.5 (talk) 04:28, 4 March 2012 (UTC)

The thing is I didn't see any actual cloud of vapor rise from the cup I just smelled it is that normal for this type of reaction? — Preceding unsigned comment added by 64.38.197.212 (talk) 12:04, 4 March 2012 (UTC)

If there had been enough vapor for you to see it in the air it would have been at a lethal concentration. Tincture of iodine only contains a few percent of iodine and not all of it is elemental either. I can imagine it would have been enough to smell but not enough to see by several orders of magnitude. 203.27.72.5 (talk) 20:14, 4 March 2012 (UTC)"

I haven't used this cup since then but I liked it a lot and it was expensive so im wondering is it safe to drink out of it?--64.38.226.89 (talk) 05:04, 29 June 2012 (UTC)

Without giving medical advice, I can point out that the product of the reaction, titanium tetraiodide would be in low concentrations and is highly reactive with water, so a few good rinses should remove it all. Titanium metal in and of itself is nontoxic. Handschuh-^{talk to me} 09:37, 29 June 2012 (UTC)

Glucosamine and tendonitis

Where can I find scientific studies on the effect of the supplement glucocamine on tendonitis?

Just to clarify I am not asking for medical advice. — Preceding unsigned comment added by 99.146.124.35 (talk) 20:43, 29 June 2012 (UTC)

Our glucosamine article contains a long and well-referenced section on health effects; that would be a good place to start. Looie496 (talk) 20:52, 29 June 2012 (UTC)

June 30

given that gold foil averages 2 atoms thick...

... how many atoms, very approximately, would be in a square centimetre of 22k foil?

thanks Adambrowne666 (talk) 04:46, 30 June 2012 (UTC)

What's the source for that "given"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:48, 30 June 2012 (UTC)

$\rho _{Gold}=19.3g/cm^{3}$
$M_{rGold}=197g/mol$
${\frac {19.3}{197}}\approx 0.1mol/cm^{3}$
$N_{A}=6.022\times 10^{23}$
$0.1\times N_{A}=6.022\times 10^{22}$
${\frac {1}{6.022\times 10^{22}}}cm^{3}/atom$

${\sqrt[{3}]{\frac {1}{6.022\times 10^{22}}}}=2.55\times 10^{-8}cm$

${\frac {1}{2.55\times 10^{-8}}}=3.92\times 10^{7}$
It's two atoms thick so,
${\frac {1}{6.022\times 10^{22}}}\times 2\times (3.92\times 10^{7})^{2}=5.103\times 10^{-8}cm^{3}$

${\frac {5.103\times 10^{-8}}{\frac {1}{6.022\times 10^{22}}}}=3.07\times 10^{15}atoms$
$karats=24\times {\frac {M_{Gold}}{M_{total}}}$
Assuming the impurities are the same atomic mass of gold and they occupy the same size space in the lattice;
$\therefore {\frac {22}{24}}\times 3.07\times 10^{15}=2.82\times 10^{15}atoms$
112.215.36.174 (talk) 05:45, 30 June 2012 (UTC)

that's fantastic, thank you .174; the formula will look very impressive in my artist's statement. Bugs, I must admit, I can't remember where i read that factoid, and am now finding estimates on the net ranging from 2 to 300....Adambrowne666 (talk) 07:29, 30 June 2012 (UTC)

Just to let you know, the assumption that the impurities are similar to gold in atomic mass and size in the lattice is wrong, but shouldn't make a big difference. It's almost certainly copper which is 3.1x lighter in terms of atomic mass, but the small proportion of it in the gold makes it more or less negliglible. Also, I didn't calculate this in the easiest way; it is much simpler if you do it like this:

$\rho _{Gold}=19.3g/cm^{3}$
$M_{rGold}=197g/mol$
${\frac {19.3}{197}}\approx 0.1mol/cm^{3}$
$N_{A}=6.022\times 10^{23}$
$0.1\times N_{A}=6.022\times 10^{22}$

${\sqrt[{3}]{6.022\times 10^{22}}}=3.92\times 10^{7}atoms$
$2\times (3.92\times 10^{7})^{2}=3.07\times 10^{15}atoms$
${\frac {22}{24}}\times 3.07\times 10^{15}=2.82\times 10^{15}atoms_{Gold}$
I just found the first way a bit more logical as it showed the volume of the individual atom and worked out the total from there. 112.215.36.174 (talk) 07:49, 30 June 2012 (UTC)

300 would be the absolute thinnest gold leaf you'll find, I think. I have a hard time imagining going thinner without breaking it, unless you're using electroplating, but then it's not foil. Someguy1221 (talk) 07:46, 30 June 2012 (UTC)

According to gold, 1 gram of Au can be beaten into 1sqm of gold leaf. That corresponds to 110x thicker than my calcs above i.e. ~220 atoms thick. 112.215.36.174 (talk) 07:59, 30 June 2012 (UTC)

Gold foil a few atoms thick is used in science labs. I think you are right that you wouldn't be able to use it for art without breaking it. --Tango (talk) 08:01, 30 June 2012 (UTC)

You can also work it out by taking the atomic radius, multipling by 2 to get the diameter and dividing 1cm into it. Square that to get the number of atoms of 1 thickness in 1cm^2 and then multiply by 2 to get it for 2 atoms thickness or whatever. I got 2.4x10^15 atoms for 2 atoms thick using a radius of 144pm. 112.215.36.174 (talk) 08:36, 30 June 2012 (UTC)

It can be fewer. Gold foils down to 0.02 µm (2x10^-8m or 20nm) are supplied by this company. At this thickness the foil is transparent. The atomic diameter of gold is 2.88x10^-10 m so its thickness is about 70 atoms. Its density is 19.32 kg m^-3. DriveByWire (talk) 12:25, 30 June 2012 (UTC)

That makes an unstated assumption about the orientation of the crystal. The distance between the layers is only 2.03x10^-10m, so there could be up to 98.5 atoms of thickness in 0.02µm if you assume optimum packing. 112.215.36.172 (talk) 00:05, 1 July 2012 (UTC)

science

is students perusing engineering from computer science branch can participate in u.p.s.c exams or they can give i.e.s exams? as computer science is not a core branch so to give such exams what should be the plan of action for such students?Divyajharia (talk) 07:40, 30 June 2012 (UTC)

Your question isn't very clear. Is "u.p.s.c" the Indian Union Public Service Commission? And is "i.e.s" the Indian Engineering Services? You probably have a tutor that can help you easier than we can. If you want our help, you'll need to ask your question more clearly. What are you studying? Where are you studying? What exams do you want to take? Why do you want to take them? --Tango (talk) 08:08, 30 June 2012 (UTC)

What is this machine

What might this machine be for? Roadsworth88 (talk) 17:38, 30 June 2012 (UTC)

A (1940's era ?) device for measuring the flow rate (of water ?) between Croydon North (UK Parliament constituency) and Mitcham and Morden (UK Parliament constituency), presumably. StuRat (talk) 17:51, 30 June 2012 (UTC)

Indeed, the river Wandle flows just south of a sewage treatment plant in Beddington Park, so it's important to be able to tell if things are threatening to back up, and drop a trouble ticket if they do. 75.166.192.187 (talk) 17:55, 30 June 2012 (UTC)

More modern I think. Seems to show flow rate of water (or sewage?) and the total quantity (calculated by integrating the flow rate. Integrator round the back!)--78.150.226.117 (talk) 17:59, 30 June 2012 (UTC)

Dial on right looks like pressure meter.--78.150.226.117 (talk) 18:01, 30 June 2012 (UTC)

Agreed. It must have something to do with the Wandle Trust. 75.166.192.187 (talk) 18:02, 30 June 2012 (UTC)

How to fix scrolling/tiling interference

I recently purchased a Panasonic Plasma TV 720 DPI 600 Hertz. After hooking it up to my digital low-def cable service I got a low hum in the audio and lines of lighter and darker interference traveling in horizontal bands up the screen taking maybe 5-7 seconds to go from the bottom of the screen to the top. No interference originated from the DVD signal, only from the cable signal when routed directly or indirectly into the TV through the AV (red/white/yellow) input. The RF (co-ax) input was clear. I had the cable guy visit. Depending on which of the three cable boxes we used the problem was more or less pronounced. We tried analog TV's, and the problem disappeared. I finally took the Panasonic TV back and traded it in for a Samsung plasma 720 dpi which is getting the same exact video problem, but now through both its RF and AV inputs. I have scheduled the cable guy back out. Is there any way to identify this type of rolling interference and what causes it? Can I assume it is an interaction between the signal source and the TV, i.e., interference on the cable line which shows up only on a certain type of set? Will ferrite cores potentially correct this sort of problem? Will it help to call 911? μηδείς (talk) 19:27, 30 June 2012 (UTC)

Assuming you tried different red/white/yellow cables, from the tests which have been done so far, it sounds like the interference comes from the cable boxes, apparently a defect in their design. Assuming they don't have another model of cable box for you to try, this leaves the following options:

1) Use an HDMI cable to connect to the cable box, if it has an HDMI output. Same with S-Video, etc.

2) Use the RF (co-ax) input. Picture won't be as clear, though.

3) Switch cable companies (or switch to satellite) and hope new one has a better cable box model.

4) Stick with analog TVs. If your digital TV has an option to lower resolution below 720, that might be worth a try, too. StuRat (talk) 20:00, 30 June 2012 (UTC)

The Panasonic which we took back had a perfect picture with the RF cable and craptastic with the RCA. The Samsung picture has weak interference through both lines. I don't see the ultimate problem being with the boxes but with a voltage on the line itself from the pole. Our neighbours all have the same cable company but not the interference we are getting.

The cable company doesn't want to give us a box with an hdmi connection unless we pay for hidef, although I intend to have the tech let us try out a box to see if it fixes the problem. Sattellite does not offer the sports broadcasts we want. μηδείς (talk) 21:27, 30 June 2012 (UTC)

If the HDMI test is clear, then you might be able to convince them to give you that box for free, if their tech tells them that their non-HDMI box just isn't working and you threaten to find another cable company due to their failure to uphold their end of the contract (provide a clear pic). StuRat (talk) 21:39, 30 June 2012 (UTC)

At this point what I really want to know is what sort of interference we are having and what typically causes it and what can fix it, like can a ferrite core fix visual interference. Again, the interference is perfectly horizontal bands of lightening or darkening of the picture of varying widths from fractions of an inch to a few inches which travel in regular waves up the screen from bottom to top over a period of about five to 10 seconds, maintaining their spacing and speed as they rise. The article on ferrite core is not very helpful and I don't know where to begin to look under interference. μηδείς (talk) 21:27, 30 June 2012 (UTC)