Wikipedia:Reference desk/Archives/Science/2009 September 22

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September 22

Soap vs Hand Sanitizer

I'm going to be living in an apartment for a while and was shocked to see them only having hand sanitizer and no other kinds of soap. Hand Sanitizer says it kills 99.99% of bacteria but I know that .01% are probably the dangerous ones. Would you suggest going out and buying bar soap, hand soap, or is the hand sanitizer good enough for daily use? Also, I brought with me some dish soap and wouldn't mind using that but is it affective as a hand wash? -- penubag  (talk) 00:02, 22 September 2009 (UTC)

I hate to break it to you, but your skin is crawling with microorganisms, most of which are harmless. There's simply no way to eliminate 100% of germs, some will always survive. As for effectiveness, soap, antibacterial soap, sanitizers etc are all equally effective - it's far more important how you use them than the product you choose. Exxolon (talk) 00:06, 22 September 2009 (UTC)

Yes, I know there are probably more than a billion microorganisms on my body and probably more in my mouth, but would you say hand sanitizer is just as affective as hand wash? If not, which? -- penubag  (talk) 00:09, 22 September 2009 (UTC)

Washing your hands with soap and water is the best and cheaper, soap stops organisms such as C. difficile as well as everything that's killed by the hand sanitizer, which I'm assuming to be alcohol gel. But then again, you would notice if you or someone in your apartment had a C. difficile infection. Although the article on hand sanitizer states that its the most effective against viruses. But again I'd still think it a bit excessive to have alcohol gel in your house instead of soap... MedicRoo (talk) 00:23, 22 September 2009 (UTC)

Clear advice from this website says hand sanitizer can not and should not take the place of proper cleansing procedures with soap and water. There you have it. --Tagishsimon (talk) 00:25, 22 September 2009 (UTC)

Indeed. It is designed to be used when it isn't practical to use soap and water. It certainly shouldn't be used when you have reason to expect your hands are dirty - it should be used purely as a precaution. --Tango (talk) 03:21, 22 September 2009 (UTC)

My understanding is that no product is good at killing viruses (or deactivating them if you prefer), it is mechanical action of washing your hands that dislodges them (the same is largely true for bacteria - soap is primarily a surfactant, not an antiseptic). --Tango (talk) 03:21, 22 September 2009 (UTC)

A plain bar of soap cleans, and is so cheap (cents for several month's worth of supply) that getting it should be a no-brainer. But yes, dish soap will work as well (although it may be a bit harder on your skin), as will shower gel, or, in a pinch, hair shampoo. For maximum benefit, be sure to rub the soapy hands for 30 seconds, including the space between the fingers, then rinse and dry on a clean towel. Both rinsing and drying contribute significantly to the effect. --Stephan Schulz (talk) 12:16, 22 September 2009 (UTC)

Thanks for thoroughly answering my questions -- penubag  (talk) 19:03, 22 September 2009 (UTC)

As a follow-up (I've only just come across this question), no product will say that they kill 100% of germs, as this can't be proved. The "kills 99.9% of known germs" is a cop-out for advertising the product - if you use their product, and end up dying from a germ which should have been killed by the product, when your family sue the company they can just say "whooaah! We didn't say it would kill all germs... this must have been one of those 0.1% we don't kill". Also, notice that they generally talk about killing "known germs" - you had better hope that you don't get any of those pesky unknown ones, as who knows if the product will kill it? -- PhantomSteve (Contact Me, My Contribs) 08:06, 24 September 2009 (UTC)

anyone have a picture of solid chlorine?

I can't believe I can't find a photo of this online ... I get retarded photos of pool disinfection crystals instead. Chlorine freezes at around -100 C, so I think it should be achievable. John Riemann Soong (talk) 01:33, 22 September 2009 (UTC)

P.S. why are manufacturers allowed to call their crystalline chlorinating agents "solid chlorine"? It really makes life in academia hard. Is it possible to file a lawsuit against these people for misleading product labelling and for misleading the public? John Riemann Soong (talk) 01:36, 22 September 2009 (UTC)

We're not allowed to give legal advice, but I've heard it said that anyone can sue anyone for anything. Doesn't mean your suit will go very far. If I were a juror I wouldn't be very impressed by the claim that consumers would be expecting a cryogenic product to put in their pools. --Trovatore (talk) 02:34, 22 September 2009 (UTC)

I looked very hard for a picture but came up empty handed. Someone needs to make some and take a picture for the good of the internet. Apparently it freezes in liquid nitrogen if any lab tech has a vial handy and an afternoon of free time to make some liquid chlorine. A description from an ancient book says the solid is initially a vivid yellow but goes clear which is odd. I don't know how reliable it is given the text's age and my potential for misinterpretation. I filtered out most of the junk by excluding words like "pool", "spa", and "filter". 66.57.240.8 (talk) 02:58, 22 September 2009 (UTC)

Liquid chlorine is still yellow-green. Is there a reason to believe that frozen chlorine won't just look like yellow-green ice? If not, why would it be something that people would think to snap a photo of and post on the Internet? I'm not saying nobody has done it, but if it just looks like frozen urine, why would it be that interesting? -- kainaw™ 05:07, 22 September 2009 (UTC)

Oh come on. There must be a picture of froze urine somewhere on the internet... — Sam 63.138.152.155 (talk) 19:47, 22 September 2009 (UTC)

It might change color depending on what form it assumes, i.e. if it looks like ice or if it assumes some kind of crystalline structure or something. Keep in mind solid ice (H2O) can look clear or somewhat opaque or even kind of blue, so who knows. I wonder what solid nitrogren looks like, for that matter? Maybe like dry ice? Someone asked me recently how you get liquid nitrogen, and I said, that's easy, you just take solid nitrogen and melt it. That didn't seem like a totally satisfactory answer, though. In any case, I would think there would be a reference, somewhere, that would illustrate various elements and compounds in their solid and liquid states? →Baseball Bugs ^{What's up, Doc?} carrots 08:57, 22 September 2009 (UTC)

This doesn't answer the question, but it does have an illustration of liquid Chlorine.[1] It was produced under pressure. I'm no chemist, but various sources point out that standalone solid Chlorine is not found in nature, but only salts. →Baseball Bugs ^{What's up, Doc?} carrots 09:09, 22 September 2009 (UTC)

It's most certainly not misleading, since 'chlorine' in common speech has meant 'chlorine bleach' (sodium hypochlorite) for quite some time. Saying 'solid chlorine' for crystalline sodium hypochlorite makes perfect sense. Don't be ridiculous. Also, actual frozen chlorine shouldn't really look much different than a yellowish dry ice. It won't likely change color when frozen since only weak van der Waals forces hold the stuff together. --Pykk (talk) 14:13, 22 September 2009 (UTC)

Since solid chlorine is not observable in nature, and probably has little usage otherwise, perhaps it's not surprising that it's hard to find a picture of it. If you google [chlorine solid] you typically end up at pages talking about crystalline compounds like you would add to swimming pools. →Baseball Bugs ^{What's up, Doc?} carrots 14:36, 22 September 2009 (UTC)

It's misleading to scientists and students of science who have to work with halogens and halogenating agents. Can't they just say solid chlorinating agents? I could see solid chlorine as potentially useful for a few organic syntheses (favouring stereochemical selection, e.g. syn addition, for electrophilic or nucleophilic attack). John Riemann Soong (talk) 05:02, 23 September 2009 (UTC)

Again, don't be ridiculous. Any and every chemist and student of chemistry should know perfectly well that common and trade names are not the same as scientific names. There's a whole myriad of compounds this is true for. If a scientist is mislead by this, then he or she is an incompetent chemist. If you don't know that 'chlorine' in everyday speech (in several languages, even) is sodium hypochlorite solution, you've got no business being in a lab. You're a potential danger to yourself and others if you know that little. --Pykk (talk) 12:11, 23 September 2009 (UTC)

But this is the google generation. There is no "technical" or specialised name for chlorine that one could search for, and therefore these companies are squandering the name. John Riemann Soong (talk) 12:41, 23 September 2009 (UTC)

http://www.mrs.org/s_mrs/bin.asp?CID=7587&DID=193420&DOC=FILE.PDF solid cl2 pale green as per gas.83.100.251.196 (talk) 23:20, 23 September 2009 (UTC)

Video proof that Hyacinth Macaw x Ara macaw cross-breeding works (not a question)...

Not a question, rather a delayed response to something that's been mentioned on here a few times in the past.

See this video. The bird is apparently a Hyacinth Macaw x Military Macaw hybrid. I know that some posters here were sceptical that such inter-generic hybridization was possible. I'd actually only ever seen still photos myself until now - some of which may have been 'shooped. Just posting this here FYI. --Kurt Shaped Box (talk) 01:35, 22 September 2009 (UTC)

What kind of medical problems are astronauts in orbital space stations equipped to handle?

I suppose evacuating an astronaut back to earth before the planned return is not something that you want to do unless it is necessary, so what kind of medical problems are orbital space stations equipped to handle? What type of problems would be just serious enough to warrant medical evacuation from space?

Google found me this page, which looks useful. --Tango (talk) 03:16, 22 September 2009 (UTC)

It's not space, but perhaps as close to the isolation and danger of space that we have on Earth, and so perhaps of interest to you: Jerri Nielsen was a physician wintering at the South Pole when she discovered that she had breast cancer. She was the only doctor, and they had no cancer drugs. She actually did surgery on herself and coached fellow crew members on how to administer chemotherapy drugs which had to be airdropped under very dangerous conditions. Her memoir of the time is interesting. --Sean 15:02, 22 September 2009 (UTC)

More like medical emergencies, not problems. DRosenbach ^{(Talk | Contribs)} 19:35, 22 September 2009 (UTC)

I can't locate a source at present, but a few years ago I attended a seminar where tests were made of various methods to perform CPR in orbit, which without the aid of gravity can be surprisingly difficult. I suspect that many medical procedures, especially anything like surgery, would be greatly complicated in a zero-g environment.

Intestinal fortitude....

Are human intestines just loose in the abdominal cavity or are they attached in some way (other than the obvious attachments to the stomach and rectum) ? If attached, this leads to another Q: During surgery they sometimes pull the intestines out of the abdominal cavity. How do they do this if they are attached ? StuRat (talk) 04:00, 22 September 2009 (UTC)

Various portions of the intestines are joined to the (muscular) abdominal walls by loops of fascia or omentum - some portions, for example of the colon are retroperitoneal and not free to move, while others are relatively mobile. The portions of intestines that you may see during surgery when the surgeon "runs the bowel" to look for perforations and such are either found free in the peritoneal cavity, or have been freed up during surgery. The intestine article is a little short on the gross anatomy, but you might get a better idea of the situation looking at greater omentum and lesser omentum. - Nunh-huh 04:39, 22 September 2009 (UTC)

Isn't most of the body's interior bound together, to some extent, by various connective tissue? →Baseball Bugs ^{What's up, Doc?} carrots 09:48, 22 September 2009 (UTC)

Well, yes, I guess. Connective tissue connects various organs in various ways. I think the question was about the anatomy of those connections. - Nunh-huh 10:34, 22 September 2009 (UTC)

Here is a link [2]to a diagram which explains it pretty well, it's a diagram but it makes it clear that much of the small intestine is attached to the mesentery, the large intestine is much less mobile. I have seen programmes where young babies have been born with much of their small intestine outside the abdomen, a condition called exomphalos and the paediatric surgeon just pushed the intestine back in through the open umbilicus, it was clearly quite mobile and not firmly attached to any other structure (of course not, otherwise it would not have been left outside the abdomen - doh!) Richard Avery (talk) 11:36, 22 September 2009 (UTC)

Thanks so far. I now have some follow-up Q's. If the intestines are "freed up during surgery", is this done by severing the connective tissue ? If so, do they re-attach it when they replace the intestines or just leave them loose ? And, if they do leave them loose, doesn't this have any negative side-effects ? StuRat (talk) 13:15, 22 September 2009 (UTC)

Yes, if the surgeon needs to get to a specific part of the intestine that requires it, he or she will make an incision through the connective tissue. In general, afterwards it's just left "loose", with no ill effects. - Nunh-huh 22:13, 22 September 2009 (UTC)

Sometimes there are ill-effects, namely scar tissue called adhesions. Fences&Windows 02:27, 23 September 2009 (UTC)

Aren't there side effects from the intestines flopping around loose ? Just offhand I would expect a greater incidence of the intestines getting twisted or moving to a place where they don't belong. StuRat (talk) 12:14, 23 September 2009 (UTC)

"Volvulus." Axl ¤ [Talk] 14:43, 23 September 2009 (UTC)

Hernia. Fences&Windows 18:46, 23 September 2009 (UTC)

OK, so, is there a procedure to reattach the intestines to the omentum, or secure them in some other manner, for those patients who suffer the side effects of intestines left "loose" ? StuRat (talk) 13:39, 24 September 2009 (UTC)

What is the name of this bird?

I saw a bird in North Western WA and I am awfully curious as to what it was. It was all black with a bit of blue on each wing (rectangular in shape really) as well as on the tail. Thanks!! Veronika Stolbikova (talk) 06:17, 22 September 2009 (UTC)

I live very far from NW WA so I'm mostly guessing right now, but you can check any of the following: common grackle, Steller's jay, Blue Bunting, purple martin, Brewer's blackbird, brown-headed cowbird and see if any of those is even close. Some of those are black but have iridescent plumage. You can do a google image search for each one of these birds to see more images. --Dr Dima (talk) 07:29, 22 September 2009 (UTC)

Dr Dima is assuming that by WA you mean Washington. I had been assuming you meant Western Australia, in which case you could be looking at a Rainbow Pitta.--Shantavira|^{feed me} 08:04, 22 September 2009 (UTC)

Judging by the picture on Veronika's user page, I would bet on the US state of Washington. Dismas|^(talk) 09:38, 22 September 2009 (UTC)

Ford Explorere 1998

Could anyone give me some information on why my 1998 Ford Explorer (import) injectors are over fueling. Desparate?

Thank you

Val. —Preceding unsigned comment added by 86.132.102.151 (talk • contribs) 11:54, 22 September 2009

I would guess that they might need cleaning - or perhaps the computer is getting a bad reading from one or more of the oxygen sensors. Do you have a check-engine light? After you get it fixed, check the spark plugs, clean & re-gap them. SteveBaker (talk) 14:49, 22 September 2009 (UTC)

Vitamin D from sunlight during a northern winter

I understand that at for example London England in the summer 20 minutes worth of clothed exposure to sunlight is enough to provide your daily requirement of Vitamin D. I also understand that winter sunshine or evwening sunshine is not effective at producing Vitamin D in the skin. What are the approximate dates during the colder parts of the year when clothed sunshine exposure for say 1/2 hour a day cannot provide the daily requirement of Vitamin D please? 78.144.255.50 (talk) 12:01, 22 September 2009 (UTC)

Our article on Vitamin D says that: adequate amounts of vitamin D3 can be made in the skin after only ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen....but also that this requires UV exposure at levels greater than 3. Unfortunately - this isn't just a matter of time-of-year, time-of-day and latitude - it also depends on cloud cover, pollution, ozone damage - and a host of other things. So we can't give even approximate dates. However, most halfway decent weather forecasting sites will give you predicted and current UV indices. This site, for example, is predicting that over the next 14 days in London, only three will have UV indices above 3 (Sun 27th, Wed 30th, Thu 1st) - so getting two 15 minute exposures per week - even at this time of year - would require you to be outdoors at close to midday on every suitable day with sufficient amounts of skin exposed (no hats, no gloves, wear shorter sleeves - don't wear sunscreen, you don't need it at UV levels 5 and below, and it prevents Vitamin D formation). As winter progresses, there are going to be fewer and fewer days where you'll get what you need. So check your weather forecast. SteveBaker (talk) 14:38, 22 September 2009 (UTC)

Hmmm - this site predicts UV levels of 4 for the whole of this week. Perhaps weather forecasting isn't that good at predicting UV levels. SteveBaker (talk) 14:45, 22 September 2009 (UTC)

A spoonful a day of Cod liver oil is not especially tasty or exciting but takes care of Vitamin A and D requirements. That's more reliable than sunlight. Cuddlyable3 (talk) 19:31, 22 September 2009 (UTC)

You risk Vitamin A overdose doing that. 89.242.104.32 (talk) 09:39, 23 September 2009 (UTC)

"...the Lowest Observed Adverse Effect Level ...for vitamin A, when taken over an extended period of time is 21,600 IU. Most multivitamins contain vitamin A doses below 10,000 IU, therefore multi-vitamins are unlikely to cause vitamin A toxicity when taken at their recommended dosage.":Hypervitaminosis A. Also see Hypervitaminosis D. Fences&Windows 19:31, 23 September 2009 (UTC)

Palladium refining.

Are there any easily available substances excluding Na/K chlorate to precipitate palladium from aqua regia solutions? Renaldas Kanarskas (talk) 12:01, 22 September 2009 (UTC)

Does this have to be in aqua regia, or just post dissolution - ie can the aqua regia be neutralised? Hydrazine might be a precipitant https://doi.org/10.1007%2FBF02060315 in 2M HNo3, as could be ammonium chloride see Palladium also [3] after neutralisation.

Aqua regia is neutralized with carbamide or with evaporation of nitric acid. IMHO hydrazine will precipitate not only palladium, but gold also. Renaldas Kanarskas (talk) 20:54, 22 September 2009 (UTC)

"Pd(II) salts + hydrazine in the presence of various ligands" is the standard way to make Pd(0) complexes used as organic catalysts. DMacks (talk) 21:29, 22 September 2009 (UTC)

Also does this precipitation have to be selective ie in the presence of Ag,Au etc. Dimethylgloxime can be a good precipitant, but will not be compatable with aqua regia.83.100.251.196 (talk) 12:19, 22 September 2009 (UTC)

Thank you, I knew about DMG, but thought it is used only to test palladium, not to precipitate. Renaldas Kanarskas (talk) 20:54, 22 September 2009 (UTC)

It'll also precipitate nickel if there is any. There's some instructions here [4] p338 (the extraction of the metal in the method given is complicated by the ability of Pd to form Palladium hydride - calcination of the DMG Pd compound, followed by redissolution and electro-winning might be another way)83.100.251.196 (talk) 10:07, 23 September 2009 (UTC)

In slightly acid solution Ni does not interfere, but gold (and selenium) do. [5] - gold is partially reduced to free metal. Pt, Ir, Rh are not precipitated.83.100.251.196 (talk) 12:22, 23 September 2009 (UTC)

As an aside, to separate Pd and Ni when produced in solution by aqua regia dissultion (after neutralisation) - electroplating of the salt solutions might be an option , with Pd2+ being much easier to electroplate (0.925V) than Nickel (-0.25V) (at standard conditions). This won't separate gold from palladium very well. (no reference)83.100.251.196 (talk) 11:21, 23 September 2009 (UTC)

As yet another aside gold salts can be extracted into an organic solvent (eg ethyl acetate incompatible with Nitric acid) after dissolution, it appears that Pd salts are not extracted by organic solvents.83.100.251.196 (talk) 12:36, 23 September 2009 (UTC)

Where did all the universe's energy come from, and where will it go?

Or is this just a mystical question? 78.144.255.50 (talk) 12:11, 22 September 2009 (UTC)

Have you tried reading Big Bang and Universe, and the latter's See also?

It's not even clear whether the concept of energy is a valid one when talking about the universe as whole and even if it is, it is not clear what the total energy of universe is. it might be zero, in which case there is no need to explain where it came from. Dauto (talk) 12:51, 22 September 2009 (UTC)

Where will the energy go? scientifically this is easy - it will spread out - the universe will acchieve thermal equilibrium - everything will be 'luke warm' (this is ignoring the possibility that the universe collapses in on itself see Ultimate fate of the universe).

See also the somewhat emotively title article Heat death of the universe !83.100.251.196 (talk) 12:54, 22 September 2009 (UTC)

Where did the energy come from - this is as fundamental as "why does the universe exist" -one simple answer is that the energy was created as part of the big bang, which is the most popular current scientific theory. What gave rise to that, and questions such as "why was the unverse (and all it's energy created)" is not answerable by science, and is purely mystical, or philosophical.83.100.251.196 (talk) 12:48, 22 September 2009 (UTC)

As I understand it the related question "what gave rise to big bang / where did the big bang come from" is also not answered by science.83.100.251.196 (talk) 12:51, 22 September 2009 (UTC)

"Yet". There are conflicting thoughts about the Big Bang. If it really started as a mathematical singularity, there should be no way of figuring out what happened "before" it. But a real singularity is incompatible with quantum mechanics. See e.g. this popular summary of a Nature Physics paper. --Stephan Schulz (talk) 13:03, 22 September 2009 (UTC)

And keep in mind the "can't be answered by science" stricture just means, "nobody has yet come up with a way to talk about this that would be anything more than a gigantic leap in logic, a bunch of speculation that could not be tested in any way." Over time, many of these questions end up being answerable by science, both as new information comes in and new theories are thrown around. "How big is the universe" is another one of those kinds of questions that is now pretty straightforward to answer. --98.217.14.211 (talk) 13:10, 22 September 2009 (UTC)

That's not true. There is a difference between not knowing something yet and knowing that something is unknowable. If there was a big bang singularity then any empirical evidence of what happened "before" the big bang (before in quotes since it could well have been the start of time itself, so it makes no sense to talk about a "before") would have been "wiped clean" and could be causally disconnected from us, so we can never know anything about it. The only way we can know anything about what happened before the big bang is if we are wrong about the singularity (which is quite likely - singularities really make no sense, so they are probably just mistakes). --Tango (talk) 13:18, 22 September 2009 (UTC)

As I said, under current understanding, it might be unknowable. However, if someone comes up with a better way to look at it, it might actually become knowable. In Copernicus' day it was considered impossible to use math to say anything about the composition of the universe—the latter was considered to be strictly a philosophical question. Our understanding of what science can and can't answer changes over time. Someday, "is there an afterlife" could be a perfectly scientific question. It isn't now. But let's not pretend that our understanding of what's knowable and unknowable is static. If you look at discussions about the origins of the universe from the 1900s, they are pretty amusing in modern eyes—very quickly every one concludes that one really can't know that much about the early history of the universe, and then some clever fellows came along and found ways to start asking scientific questions about it. --98.217.14.211 (talk) 18:06, 22 September 2009 (UTC)

I once read a 19th century science book for high school students, in which the authors asserted that the atom was as indivisible to the chemist as the Moon was to astronomers. This was a literally correct statement: Note that less than 100 years later the atom could be split in the lab, in the powerplant, in the engineroom of a ship or on the battlefield, and pieces of the Moon were brought back to Earth. 2 weeks ago there was a report in a science journal of the isolation of a magnetic monopole. Edison (talk) 13:46, 22 September 2009 (UTC)

It came from God.

Your next question is liable to be, "Define 'God'." At that point, things become circular. →Baseball Bugs ^{What's up, Doc?} carrots 13:26, 22 September 2009 (UTC)

The total energy in the universe can only be estimated from our position, and our best estimates put it somewhere around zero, and certainly within error of zero (noting of course that this margin of error is very large), leaving the possibility that actually is zero. From a dirac-esque "knowing it is right because it is beautiful" poin of view, this certainly appeals. But of course dark energy and all that will probably just mess everything up if or when it is discovered. Elocute (talk) 21:53, 22 September 2009 (UTC)

0 =1-1. so if you start with 0, you can get positive and negative versions of the same thing for free!

Curious -- couldn't this be kind of related to the fate of the universe? If the net energy of the universe is negative, then perhaps the ultimate fate of the universe is a Big Crunch. If it's positive, the universe will just expand itself to death. If it's zero, then perhaps its fate is periodic. John Riemann Soong (talk) 05:08, 23 September 2009 (UTC)

Since there seems to be a huge amount of energy in the Universe - for example the energy of matter E=mc^2 - then where is all the negative energy to balance this if the total energy is zero? I did not think you could have negative energy. 89.242.104.32 (talk) 09:43, 23 September 2009 (UTC)

Gravity is essentially stored negative energy since it is an attractive force whose 'zero point' is at infinity. Elocute (talk) 09:56, 23 September 2009 (UTC)

The question is predicated on the assumption that things must come from somewhere. All religions do not agree on this point, e.g., Buddhism. I think that existence is necessary for things that exist, but they don't all need an origin. When a question is invalid, no valid answer can be given. Imagine Reason (talk) 00:23, 25 September 2009 (UTC)

Luckily religious concerns are largely disregarded completely in fundamental physics research. The question is as far as I can see asked merely on the premise of current physical understanding and asks for an answer within that same framework (Which is that the universe had a beginning and that energy is conserved over non-negligible timescales). I apologise if I am te only one who is inclined to dismiss this discussion, of the origin of the universe on a science desk being conducted in a religious context, as fairly facetious. Elocute (talk) 09:53, 25 September 2009 (UTC)

Archives for Raw Solstice Data

The "Calendar shift with Seasons" graph from 1750 to 2250 shows two (2) specific measurements for the actual date and time of Winter solstices. The 1st is Dec 23, 1903 at 0:18 UT; and, the 2nd is Dec 22, 2003 at 6:59 UT. I would like to know where the Archives for all this data can be found. Thankyou for any help that can be provided. 12:45, 22 September 2009 (UTC)

Where is this graph? Can you supply a link to it please?--Shantavira|^{feed me} 14:39, 22 September 2009 (UTC)

The referenced graph has been under the previous "Gregorian Calendar" heading in Wikipedia for many months. I just checked and it is no longer there. Apparently an entire new entry has been substituted. Now under "Calendar Seasonal Error" a new graph appears entitled "Leap Shifting of the Gregorian Calendar" showing "Date of Summer Solstice over 400 years"; (actually 500 years due to beginning and ending 50 years not being labeled). This is the same type of raw data I am interested in reviewing.-- [[User:Edwrdgmbl]Edwrdgmbl (talk) 12:30, 25 September 2009 (UTC)

Craving certain foods

There are times I crave to eat spinach and someone told me that I probably have an iron deficiency and my body is craving it. If that is so, why are there times I crave raw mushrooms or, at one time, anything with vinegar? Is there an article about this? (note: I am not pregnant unless it is by the Holy Ghost) --Reticuli88 (talk) 13:08, 22 September 2009 (UTC)

The mushroom craving may be because you're low on protein (in which case I'd also expect you to crave meat, fish, eggs, milk, and nuts). However, raw mushrooms may be contaminated with the manure in which they grow, which could cause disease, so I sure don't recommend eating them without cooking.

Vinegar contains a weak acid (acetic acid). It's possible that your body detects that it's excessively alkaline and thus craves acid (the two cancel each other out to produce salt and water). Do you also have a craving for fruit or juice at those times (which contains citric acid) ? StuRat (talk) 13:22, 22 September 2009 (UTC)

Incidentally, while spinach is a relatively good iron source as leaf vegetables go, its fantastic reputation in popular culture is mostly due to a misplaced decimal point giving the false impression it has ~10 times the iron content of similar vegetables. AlmostReadytoFly (talk) 13:34, 22 September 2009 (UTC)

I'm not convinced there's necessarily a link between a food craving and a deficiency. That could lead to irrational justifications for eating junk.--Shantavira|^{feed me} 14:44, 22 September 2009 (UTC)

Well said Shantavira. My belief is that food cravings have a psychological basis. I'm not saying that is bad in any way but that is I think the source of our needs for certain flavours or foods. Richard Avery (talk) 15:33, 22 September 2009 (UTC)

I am convinced that there is often a link, but our understanding of how food cravings arise is remarkably weak. We know that the brain contains powerful mechanisms, operating below the level of consciousness, for associating foods with changes in body state that follow eating them, but we have hardly any understanding of how they work. We have a better understanding of how food aversions arise, but even for that there are a lot of puzzles and controversies. (One example of a craving that often strikes me is that people who come to town after a long backpacking trip usually have a tremendous appetite for fruits and vegetables -- they're notorious for "cleaning out the salad bar".) Looie496 (talk) 15:36, 22 September 2009 (UTC)

I'd say that we have an imperfect mechanism for craving foods high in nutrients we need. One way it can fail is with foods designed to fool us. Thus, someone craving fruit juice may settle for some brightly colored sugar-water (or even worse, sugar-substitute-water), which doesn't actually have any of the nutrients we need. Another way it fails us is that our bodies remain designed to prepare for famine, by packing on the pounds by eating high-fat, high-calorie foods whenever we can. Also, since salt is hard to come by in a natural diet, we tend to crave excess salt all the time. StuRat (talk) 19:05, 22 September 2009 (UTC)

After working outside in the North African desert for several weeks, I started realizing that I had been having constant, intense cravings for Chinese food. I didn't make the connection, however, until someone pointed out how little salt we had been eating (compared to what we had been sweating out) and how salty soy sauce is. Then I realized that what I really wanted was just to drink a bottle of soy sauce. — Sam 63.138.152.155 (talk) 19:54, 22 September 2009 (UTC)

Other than a basic craving for something like water or salt, how could it be that someone craves something when they have no clue what that food contains? If one has no idea what foods contain iron, how could you crave an iron-containing food? Sort of a bizarre, bacronym-sort of concept. DRosenbach ^{(Talk | Contribs)} 19:38, 22 September 2009 (UTC)

You body does all sorts of things like that. You don't have to know that air contains oxygen and you need this to burn calories for your body to tell you when it's time to take a breath. Your body keeps track of what happens after you eat various foods and determines for itself when you need those foods. Just like you will despise foods that make you ill, you will crave those that make you feel better by satisfying some deficiency.

Also consider that hardly anyone ever actually dies from a nutritional deficiency in places where a variety of food is available. Why don't we all just eat our single favorite food until we die from whatever it lacks ? Well, some people obviously attempt to follow a healthy diet, but there are also plenty who eat whatever they crave, nutrition be damned. Even those people rarely die of a deficiency, precisely because this "craving" system provides for a minimum level of nutrition. StuRat (talk) 20:39, 22 September 2009 (UTC)

Note also that spinach doesn't have particularly much iron. This bit of folklore is due to a wrong measurement decades ago. --Ayacop (talk) 08:54, 23 September 2009 (UTC)

Are you saying that spinach is nothing more than a placebo to Popeye? Well, blow me down... another core belief demolished. :( →Baseball Bugs ^{What's up, Doc?} carrots 09:29, 23 September 2009 (UTC)

Chopped liver [6], on the other hand, is a good source of iron (seriously). AlmostReadytoFly (talk) 16:03, 23 September 2009 (UTC)

Try this article on food choice in animals. Also see the work of Steve Simpson at the University of Sydney on this. Fences&Windows 19:41, 23 September 2009 (UTC)

Infra-Red rectenna power breaks the Second Law of Thermodynamics?

On a recent television program, an advanced infra-red (as opposed to microwave) rectenna, based on nanotechnology was demonstrated. This device converted heat radiation into electricity even from the ground at night! Could such a device convert the low grade heat at the end of the universe back into high grade energy, breaking the second law of thermodynamics and preventing the ultimate heat death of the universe?Trevor Loughlin (talk) 13:55, 22 September 2009 (UTC)[Trevor Loughlin]

• I'm sure the answer is "No" - but you might like to read our article Nantenna which describes such things in detail. I believe these devices can only operate if kept cooler than their environment - and that's probably the key to why they don't break the laws of thermodynamics. SteveBaker (talk) 14:03, 22 September 2009 (UTC)
• (EC) The ground at night is still probably 270 degrees or so above absolute zero, so there's no lack of energy there to be made use of. As to your second question, err, let me think for a moment ... no. There's no reason to suppose, on the basis of a very poor understanding of the physics involved, that the device could do something as fundamental as that. --Tagishsimon (talk) 14:04, 22 September 2009 (UTC)
• (EC) No. Even if this really exists (and TV programs typically are lousy sources), it would live off the temperature difference between the (warm) ground and the colder atmosphere/antenna at night. --Stephan Schulz (talk) 14:10, 22 September 2009 (UTC)

The amount of energy that it could receive is actually very small, and you will find that the amount is of the order kT_cmbB, k the Boltzmann constant, T_cmb the CMB temperature, B is bandwidth. Any antenna that receives also makes a similar quality transmitter, so it would be transmitting the thermal energy of the rectifier out the antenna. This would be about kT_antennaB. All resisters, and electronics have a background energy, kTB. See Johnson–Nyquist noise. So to receive energy the antenna has to be a lower temperature than the CMB. This means that the 2nd law is not violated, and you won't be able to get free energy from thermal radiation. Graeme Bartlett (talk) 07:37, 23 September 2009 (UTC)

Don't we have an article on antenna temperature? It should be noted that antennas, especially phased arrays or "rectanna/nantenna" systems, are narrow band. The antenna temperature is therefore sort of unintuitive, since we expect a blackbody spectrum if we seek to have a well-defined temperature. According to NASA, "Antenna temperature is a way of expressing the brightness of a radiation source - it is proportional to the power per unit area emitted by the source". Keep this in mind when analyzing second-law-of-thermodynamics - you might be comparing two "temperatures" that cannot actually be compared. The catch-all is that power will not flow into the antenna in signficant quantities, at any band, against the thermal gradient. Nimur (talk) 15:46, 24 September 2009 (UTC)

Neutralizing Acid waste

In order to neutralize the acid in a waste stream (composed of H2SO4and H2O), dry ground limestone (composition 95% CaCO3 and 5% inerts) is mixed in. The dried sludge collected from the process is only partly analysed by firing it in a furnace which results in only CO2 being driven off. By weight the CO2 represents 10%of the dry sludge. What percent of the pure CaCO3 in the limestone did not react in the neutralisation?

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. Please attempt to solve the problem yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. ~ Amory (user • talk • contribs) 16:44, 22 September 2009 (UTC)

I attempted this experiment in high school, I was troubled by two issues, one was how dry was dry, the hotter the drying the lighter it got, and there seemed to be no completely dry state. And also there were other gases given off such as H₂S. (yuck). You may also strick Selenium, and sulfur dioxide in your case, but I expect your teacher does not want you to consider impure limestone! Graeme Bartlett (talk) 22:50, 22 September 2009 (UTC)

What would happen in space

I'm very curious about the details of what would happen physically to my body if I was, say, ejected from a rocket. I've seen in games and movies that space seems to suck you out of a spaceship if a door leading outside opens. Is that accurate? If I was sucked out into space, what would happen to my body before I died? And I'm not wearing a spacesuit or anything of that nature. Thanks : ] EVAUNIT-666 16:34, 22 September 2009 (UTC)

Try the search available at the top of the page. A quick look reveals this, this, and this. Essentially, you die. Quickly. ~ Amory (user • talk • contribs) 16:51, 22 September 2009 (UTC)

But you don't explode. We have an article on space exposure.--Shantavira|^{feed me} 17:00, 22 September 2009 (UTC)

It would be more accurate to say you get blown out into space, because of the pressurized air (normal air pressure) behind you and no pressure resisting that force on the outside of the ship. StuRat (talk) 19:13, 22 September 2009 (UTC)

I was just about to post the same (ec) and that sucks!Cuddlyable3 (talk) 19:17, 22 September 2009 (UTC)

Most vacuum cleaners just plain suck, but ours both sucks and blows ! StuRat (talk) 20:29, 22 September 2009 (UTC)

My undergrad lab was in an oooold building, running joke was that everything sucked but the fume hoods and everything blew except the ventilation. DMacks (talk) 20:34, 22 September 2009 (UTC)

I've heard this line before (I think Data said it on Star Trek), but never understood it. What does it mean to be "sucked out of" something if not that there's a lower air pressure at the destination and the air where you are is blowing you towards it? How is the space example any different from a vacuum cleaner which creates a low-pressure chamber which causes stuff to be "blown" into it by the air behind the stuff? --Sean 13:17, 23 September 2009 (UTC)

I suppose the diff is that a vacuum cleaner itself lowers the pressure versus the ambient pressure, and this lowering of the pressure with predictable results constitutes "sucking". Since space doesn't "lower it's pressure with the goal of causing suction", it doesn't suck (although being in space without a spacesuit would most definitely suck). StuRat (talk) 14:16, 23 September 2009 (UTC)

It is well known that suction is a phallusy fallacy. Ie it doesnt exist: its the air pressure that pushes.--CruelSea (talk) 17:30, 23 September 2009 (UTC)

I believe that is the logic of the "blown not sucked" assertion above. Presumably when someone in that camp falls through the ice, they complain about the quality of the heat, since "cold" doesn't exist, either. --Sean 19:48, 23 September 2009 (UTC)

if i remember correctly, it takes about 9 seconds to die in space. in the mean time the part of your body that is facing the sun is burning and the side away from it is frozen, and if your rotating in space you'll thaw out and burn along with the fact that your under the pressure of the vaccume in space. essentialy its going to be a looong 9 seconds till you die. DanielTrox

Our article on Space exposure, to which Shantavira linked in the second answer to the original question, does not agree with you. 87.81.230.195 (talk) 02:27, 26 September 2009 (UTC)

GREEN HOUSE EFFECT

HOW MUCH TEMPRATURE WE CAN RAISE BY USING GREEN HOUSE EFFECT.

It depends on the conditions. Venus is often considered to have a runaway greenhouse effect and has surface temperatures of some 460 °C. You may also be interested in our articles on global warming and global climate models. — Lomn 18:03, 22 September 2009 (UTC)

It also has roughly 200,000 times as much carbon dioxide per square meter as we do. Which illustrates the point that the greenhouse effect can basically be dialed up as high as you want provided you have sufficient greenhouse gas or in the case of a physical greenhouse that you have enough building materials. It is a matter of diminishing returns though since every increase will provide less extra warming than the one before. Dragons flight (talk) 18:16, 22 September 2009 (UTC)

I don't see any reference to climate in the question so are you sure they are not asking about greenhouses etc? My solar vaccuum tubes get to 200C easily using only the greenhouse effect when they have no coolant in them (if the pump doesn't work the coolant blows off at 140C as I discovered this summer)... --BozMo talk 20:45, 22 September 2009 (UTC)

Does a rotating ring show length contraction?

If a straight rod were to travel past me at a significant fraction of the speed of light, I understand that I would observe it to be length-contracted. And I understand that this relates to relativity of simultaneity: even if I observe that the two ends of the rod are passing two points on the ground at a certain instant, from the frame of reference of the rod, the ground is length-contracted and the front end of the rod will pass the first point before the back end passes the second point.

However, what would I observe if a ring (say a hula hoop) were rotating around me? If it rotates at a high velocity, then it seems to me it should be length-contracted, that markings on it will be closer together. But since it's a continuous ring, it still has to join up. The only way for me to observe all the points closer together would be for the ring to have a smaller radius, right? What makes this complicated for me is that if it's rotating, the parts of the ring are accelerating, and I don't really know how length contraction or the other transformations work in this type of accelerating frame. — Knowledge Seeker দ 19:16, 22 September 2009 (UTC)

The hoop will shrink. Imagine starting with a solid object at rest (with respect to frame S) and then simultaneously (with respect to S) accelerating every part of it by the same amount. The object is now physically stretched in the direction of the acceleration—if you boost into its new rest frame it will be longer by a factor of γ. Since it's a solid, it will shrink back to its preferred size through the action of intermolecular forces (or it will break if you accelerated it too much). The preferred size with respect to frame S is of course 1/γ times the rest size. Essentially the same thing happens with the hula hoop, except that the lowest energy state will be a hoop of smaller radius. It's very much like a metallic object shrinking as it cools. This is different from the length contraction you get from a Lorentz boost, which is just a coordinate change and not a physical change in the object.

(Actually, there is also a centrifugal tension that will tend to make the hoop expand. Which effect dominates will depend on the characteristics of the material, but there aren't many materials that can survive the stresses of relativistic rotation anyway.) -- BenRG (talk) 22:08, 22 September 2009 (UTC)

See Ehrenfest paradox. — DanielLC 22:22, 22 September 2009 (UTC)

The conclusion from the Ehrenfest paradox article is that clocks cannot be synchronized between rotating reference frames. SO this means you won't really be able to tell where that hoop has rotated to in a time interval. Graeme Bartlett (talk) 10:07, 23 September 2009 (UTC)

Thanks for the responses. I'm gratified that there isn't a very clear answer to this, though I was hoping for some nice, simple explanation. The reason I was pondering it was I was reading about how magnetism was a consequence of length contraction — while I can grasp that for a straight wire, if the wire were in a circuit, it seems to me that that...actually, never mind, I've tried rewriting this sentence three times and I can't get my thoughts out right. I think I will have to ponder this some more. I really appreciate the answers and any insights you have. — Knowledge Seeker দ 06:10, 24 September 2009 (UTC)

There is a clear answer to this, the one I gave. It's complicated inasmuch as it depends on the properties of the material, but there's no debate over it. The Ehrenfest paradox is a disagreement about words, specifically about how reference frames ought to be defined. The Sagnac effect is closely related. For some reason it's mostly crackpots who argue about the Sagnac effect and mostly real physicists who argue about the Ehrenfest paradox, but the arguing is equally silly either way. Good article, though. -- BenRG (talk) 11:24, 24 September 2009 (UTC)

There is some interesting physics related to current in a wire. For example, an ordinary neutral object is still neutral under a Lorentz boost. But consider a straight neutral wire with current running in it. Under a Lorentz boost (in any direction other than perpendicular to the wire), the moving charge carriers will change density differently from the stationary opposing charge, so the wire acquires a net charge. How can that be, when charge is supposed to be frame invariant? If the wire is part of a circuit, it has to bend around and go in the opposite direction at some point, and that part will acquire an opposite charge; it all adds to zero. If the wire is transporting charge from one reservoir to another, then the relativity of simultaneity implies that in the boosted frame the sum of the charges in the two reservoirs will be different, and that difference shows up on the wire. If you have a hoop of superconducting wire with a current in it and you start it rotating, charge conservation implies that it can't acquire an overall charge and symmetry implies that no part of it can have a local charge either. However, a measurement device sitting on the wire (and rotating with it) will measure a net charge density in the wire (as you can see by doing a local Lorentz boost). If you walk it slowly around the whole wire it will measure the same charge density everywhere. When you reach your starting point again you might conclude that there's a nonzero charge on the wire as a whole, but you'd be wrong. This is another version of the Ehrenfest/Sagnac effect. -- BenRG (talk) 12:18, 24 September 2009 (UTC)

A quick summary of our article on relativity and electromagnetism is here. I think it's deeeply fascinating that special relativity "proves" that electricity and magnetism are two sides of the same coins. Had the math of lorentz been developed and applied earlier, it could have beaten Faraday to the discovery. EverGreg (talk) 08:42, 25 September 2009 (UTC)

Behind the navel

What can be found behind the human navel ? Is it possible to feed a person by injecting nutrient at the navel ? Cuddlyable3 (talk) 19:40, 22 September 2009 (UTC)

The human navel (umbilicus) is the remnant of the insertion site of the umbilical cord through which the umbilical vein once provided nutrients to the developing fetus. After birth, the umbilical cord no longer functions and eventually falls off, leaving behind the navel. Behind the navel is the Ligamentum teres hepatis, aka round ligament of the liver, which is essentially a string of connective tissue that connects to the liver. In an adult it's really no more than an anatomic landmark and doesn't do anything. The remnant of the umbilical vein is collapsed and replaced with fibrous tissue. Is it possible to feed a person? Yes and no. Not an adult person -- there really isn't a passage that could be used. However, the umbilical vein is commonly used as an IV access site in neonates, particularly in premature infants, through use of an umbilical line. --- Medical geneticist (talk) 21:32, 22 September 2009 (UTC)

Do Re Me

I hear that Indian [subcontinent] music possesses 8 notes instead of the seven commonly used in the US/Europe/etc. Where does this extra note fit in? Are the other notes shifted to make room, or is there an uneven distribution of space between notes to achieve placement of this extra note between Te and the next Do? I thought I'd find an answer or a direction for the answer at Do Re Me or Solfège, but I could not. DRosenbach ^{(Talk | Contribs)} 20:04, 22 September 2009 (UTC)

See musical scale and swara. Dragons flight (talk) 20:10, 22 September 2009 (UTC)

A major scale (and its wraparound buddies the minor scale and various modes) aren't evenly distributed at all; they're only 7 of the 11 notes in the chromatic scale. Most of the world's musical traditions use scales that take some number of notes from the chromatic scale. While the Solfège major scale sounds nice and even to someone from a western background, that's largely because they're so basically acculturated to it (people have been speaking to them in it since the day they were born); things like a Iwato scale will sound just as consonant to someone from that culture (cf Scientific American article from about 1991). But even that chromatic scale (the notes on a piano) isn't the limit; some music is microtonal, which means it uses notes between the piano keys, and even the notes you might think a piano is tuned to are kinda wrong (see musical temperament), but unavoidably so. -- Finlay McWalter • Talk 20:37, 22 September 2009 (UTC)

Do you mean 12 pitches in the chromatic scale? Rckrone (talk) 22:04, 22 September 2009 (UTC)

oops, yes, 12. -- Finlay McWalter • Talk 23:01, 22 September 2009 (UTC)

And westerners aren't prisoners of the tyrannical major mode either; the harmonic minor scale (which deviates from the modal template by raising its last note) is very common in classical music, and the blues scale (which devilishly flattens the fifth) is dominant (sic) in blues, jazz, and rock music. Plus the scales used for the folk musics of many western places (e.g. Hungarian gypsy scale) use different notes again. -- Finlay McWalter • Talk 20:53, 22 September 2009 (UTC)

It's not just acculturation. There's a preference for small-integer-ratio jumps in frequency, because their overtones reinforce one another in chords. So you have the perfect fifth, the most basic interval after the octave, as a 3/2 ratio, and the fourth at 4/3 and the major third at 5/4. How you fit these into a temperment where you're allowed to change keys, that's less canonical, but these basic intervals, at the very least the octave and the perfect fifth, I would expect to be reinvinted in every musical tradition. --Trovatore (talk) 00:04, 23 September 2009 (UTC)

In fact, except for the octave, none of the intervals that the standard chromatic scale produces are perfectly harmonious, because the ratios aren't precisely integral. The advantage of the system is that it allows switching to a different key without retuning, and key changes are essential to modern western music. This system of tuning is called well-tempering, and became popular in the 1700s -- Bach's Well-Tempered Clavier is a group of pieces written to exploit it. Looie496 (talk) 18:17, 23 September 2009 (UTC)

Gull hypnosis

How does this work? Seems similar to chicken hypnotism, from when I've seen it - but the technique is completely different. Any ideas? --Kurt Shaped Box (talk) 20:37, 22 September 2009 (UTC)

I would refer you to our resident gull expert, but, oops, that would be you. I could guess that they have a "sleep mode" that is triggered by their parents or possibly their mates, and that they are somehow tapping into this. StuRat (talk) 21:47, 22 September 2009 (UTC)

(after ec)I've never seen anything like that before in my life. I wouldn't have thought it possible to flip a gull onto its back like that and touch its belly without getting your fingers mauled. Could whirling it around beforehand cause the gull to become too dizzy to move? Na, that doesn't seem plausible to me. --Kurt Shaped Box (talk) 22:04, 22 September 2009 (UTC)

Some animals pretend to be dead not to be eaten -it does not work with scavengers of course, but not everybody is. Could it be this case too? maybe not.--84.220.118.29 (talk) 22:29, 22 September 2009 (UTC)

Well, I don't hang out with gulls 24/7 - but I've never seen nor heard of them 'playing possum' before. If a gull was cornered, I'd expect it to fight for its life. I do know that covering a gulls eyes (say by putting a piece of cloth over its head, or putting the entire bird in a sack - as the bird ringers do) will render it 'mostly docile' after a couple of minutes - but this is clearly not what happened in the video... --Kurt Shaped Box (talk) 22:51, 22 September 2009 (UTC)

Though the bird was shaken beforehand, and already in the upside down position, it was placed down on the hard surface with notable gentleness. I would imagine that the psychology of the bird already largely accepted the likelihood of defeat in this encounter with the man. Thus it experienced (psychologically) relief when it found itself merely resting on its back on the hard surface, no longer in the grasp of the man. And the stroking of its belly also was gentle, thus it failed to trigger an alarm response, due to the special circumstances of having just been released from what it surely perceived as a life threatening situation. It was choosing to leave well enough alone. I have little doubt that animals have psychological states of mind that are analogous to humans'. The gull is probably not going to go to law school, but I think it shares some version of the human basket of frames of mind. Bus stop (talk) 23:06, 22 September 2009 (UTC)

That's an interesting hypothesis - thanks. I've just been browsing YouTube for similar videos and it seems that doves, pigeons lovebirds and canaries can also go into/be put into the same 'trance state'. --Kurt Shaped Box (talk) 23:46, 22 September 2009 (UTC)

I may be wrong. These other instances don't show how the bird got to be on its back, immobile. Bus stop (talk) 00:00, 23 September 2009 (UTC)

I now suspect that there's a specific method of 'hypnotizing' birds, which works with many different species. Some sort of magician's parlour trick that the performer intentionally doesn't show in the vids. Birds do sometimes play or sleep on their backs - but never with their necks in that position, as far as I'm aware. --Kurt Shaped Box (talk) 00:08, 23 September 2009 (UTC)

Birds, among other animals, seem particularly helpless and vulnerable when on their backs. Cats and dogs for instance can defend themselves and fight while on their backs. But bird's wings would seem to me to be at their most useful only when the bird is upright, but I could be wrong about this. Bus stop (talk) 01:33, 23 September 2009 (UTC)

I think you're all a bit too gullible. Why should this bird have been hypnotized, because it says so on the page? Maybe it hit its head on a ship plank and the guy just had the right timing for his show. Maybe chemicals were involved, fed to a random gull beforehand. --Ayacop (talk) 08:43, 23 September 2009 (UTC)

"Gull"-ible? Dat's fer da boids. Chemicals? Like when a wolf slips a mickey to a gull? My first thought on seeing this video was, "He's not dead! He's just stunned! He's pinin' for the fjords!" Then away he flew (assuming it was actually the same bird), headed for them fjords. →Baseball Bugs ^{What's up, Doc?} carrots 09:27, 23 September 2009 (UTC)

WP:OR: I hypnotized my pet rabbit when I was a kid: you cover its eyes and rub its belly and it goes into a similarly flaccid state. --Sean 13:22, 23 September 2009 (UTC)

I'd be curious to know how those fishermen harmlessly captured a wild seagull while on the water in their rickety craft. Bus stop (talk) 13:29, 23 September 2009 (UTC)

Gulls, whilst normally quick-witted, fast-moving and difficult to catch, do have a habit of tangling themselves up in fishing lines or getting the hooks embedded in their beaks when they're trying to snatch the bait - especially when following boats. Those guys probably just reeled the gull in. --Kurt Shaped Box (talk) 19:37, 23 September 2009 (UTC)

I've never seen this, and don't have a real theory. There are parallels in invertebrates too, such a tickling trout (as a means to catch them) and standing a lobster on its head - or more accurately a tripod of its head and front claws - which also seems to induce a trance-like state. I wonder if the whirling of the gull or the inversion of the lobster cause a rush of blood to the head? Jimfbleak - talk to me? 12:55, 25 September 2009 (UTC)

It would be useful to discover if the behaviour of the gull and the other birds in those videos corresponds to any particular known trance/altered consciousness state. It's not something I have any experience in either. Anyone here up on this? --Kurt Shaped Box (talk) 23:26, 25 September 2009 (UTC)

Significant figures

What is the significant figure rule for addition and subtraction?174.6.144.211 (talk) 23:37, 22 September 2009 (UTC)

This should give you all you need to know: Significant figures#Arithmetic. ~ Amory (user • talk • contribs) 23:46, 22 September 2009 (UTC)

Roller Coaster Momentum

How do I determine the momentum of a roller coaster? I know that momentum is mass times velocity. If the height of the roller coaster is 191ft tall, the length is 1204 ft. long and the speed is 65.6 mph, what is the mass?

You can't tell without more information. Rckrone (talk) 00:22, 23 September 2009 (UTC)

Maybe this can be worked out. Let mass of coaster be M. Assume its initial velocity is zero. Force (gravity) = Mass X acceleration

So What is the component of gravity acting along the hypotenuse of a right angled triangle height 191; baseline 1204?

Momentum does not come into the solving of this problem. Enough clues!--CruelSea (talk) 00:50, 23 September 2009 (UTC)

With respect, momentum is what the OP asks for. But you cannot evaluate the mass M from the information given. Cuddlyable3 (talk) 06:49, 23 September 2009 (UTC)

Agree it looks like that if you dont have the time taken from top to bottom. Pity!--CruelSea (talk) 16:06, 23 September 2009 (UTC)

Even if you did have the time, it wouldn't help. Remember the story about Galileo and the Leaning Tower of Pisa? (Yeah, it didn't really happen, but the principle is valid enough.) --Anonymous, 20:27 UTC, September 23, 2009.

Postmature birth

Okay, we all know being born premature is bad for you. Would a 10 month term baby have the brain/mind of a 1 month old or a newborn? I doubt much nonsomatic development (beyond the usual) or experience can occur in an environment less stimulating than Plato's Cave.

Unlike normal newborns, this infant will be able to lift his head at birth. Will he say his first word 1 month "earlier" and remember 1 month earlier and walk 1 month earlier etc. for life, fading into normal bounds (for the choice of age start point that is anamolous)? Or will the brain and/or body play catch up/slow down? What studies are there that attempt to follow postmatures' height/weight and developmental milestone excesses (delays) as deep into life as statistically significant? Sagittarian Milky Way (talk) 23:52, 22 September 2009 (UTC)

BozMo said it is possible for babies to be able to lift their heads at birth. (curious: was your baby some number of days overdue?) If you used enough infants, I bet you could easily find better than chance more likely to lift the head at birth the older they are, at least up to a point (even 13 days overdue is still not outside medical normal yet, so it's harder to make the health complications excuse). Likewise, even after accounting for everything one could possibly think of, finding a correlation likely not from chance in ages of death seems almost impossible. Somewhere in between either we csn't track the discrepencies anymore or the discrepencies even out before then. I'm not expecting to find correlations with menarche or anything.. :) Sagittarian Milky Way (talk) 19:55, 23 September 2009 (UTC)

It is perfectly 'normal' for a child to be able to lift their head at birth, just rather 'unusual'. One of mine could. --BozMo talk 10:46, 23 September 2009 (UTC)

I would suspect that the real issue here is not whether the relative "early" nature matters much, but whether there are health risks involved with pregnancies that late. I would suspect that a much more difficult labor would raise a variety of risk factors for both child and mother. As for being a month more developed than your peers, it can hardly matter—a month is just not enough time to matter. I am born in January, my peer is born in February. Does it matter if I have a February brain? Not at all—it will be indistinguishable, and nobody cares what month you are born in (it's not like I'll be tracked with all of the January births—nobody will say, "gosh, he seems a month smarter than his peers!"). --98.217.14.211 (talk) 01:01, 23 September 2009 (UTC)

Being born prematurely is not bad for you. If the mother is terminally ill and the fetus is induced prior to the mother dying and the mother dies prior to the due date, bring born prematurely would be good. DRosenbach ^{(Talk | Contribs)} 12:41, 23 September 2009 (UTC)

Yes it is, unless you have some unusual definition of "bad". From the preterm baby article:

The shorter the term of pregnancy, the greater the risks of mortality and morbidity for the baby primarily due to the related prematurity. Preterm babies have an increased risk of death in the first year of life (infant mortality), with most of that occurring in the first month of life (neonatal mortality).

It goes on to list a variety of serious complications that premature babies are at higher risk for. --Sean 13:28, 23 September 2009 (UTC)

Your quote fails to take into account my given premise. The most serious complication is being dead, unless you have some unusual definition of "complication" or "death." DRosenbach ^{(Talk | Contribs)} 14:30, 23 September 2009 (UTC)

We're all talking about risk factors here. Being born prematurely raises your chance of dying quite a bit. I imagine that being born postmaturely would increase the risk of complications as well. Statistically speaking, being born prematurely is bad for babies, even if in the case of any given individual, it might not be a problem. There are of course mitigating circumstances, but your "terminally ill mother" example is certainly not very common. In medicine (as in many other realms), talking in terms of what is actually likely to happen (and what is more probable) is more useful than being pedantic about it. --98.217.14.211 (talk) 15:37, 23 September 2009 (UTC)

I agree with Sean. DRosenbach's scenario is unhelpful in the context of the original question. Axl ¤ [Talk] 17:04, 23 September 2009 (UTC)

It's not the frequency of "terminally ill mothers", but the idea that just because there is a worse evil that the lesser one is not "bad" for you. If a thought-experiment demon says he'll kill the baby unless mom drinks and smokes throughout her pregnancy, that greater evil doesn't magically make those behaviors not-bad for the baby. --Sean 19:54, 23 September 2009 (UTC)

My son was born about 2 weeks post-mature. When my wife didn't give naturally give birth on the pre-ordained date, they first decided to induce her - but then changed their minds and scheduled a Caesarian section - but then she got a really nasty cold and so they postponed that even longer. The most noticable side-effect was that my son had lost a significant amount of weight...aside from that...not much. He certainly wasn't born with the abilities of a 2-week-old baby. SteveBaker (talk) 23:24, 23 September 2009 (UTC)

I'm a bit late to the discussion here, but I have to say that, despite a somewhat pointless digression into prematurity, no one has mentioned the article on postmature birth, which lists some potential complications of a post-dates pregnancy. (Isn't this supposed to be a REFERENCE desk?) It's also worth noting that the "dates" of a pregnancy are notoriously prone to error. Since the dates are based on the last menstrual period (also discussed in the pregnancy article), dating can be difficult in women who have an irregular cycle. --- Medical geneticist (talk) 23:46, 23 September 2009 (UTC)

What, you don't use one of those time of ovulation things when trying to get pregnant? I suppose the trial and error method is more fun.

acid battery casing repair

Hi, I have a near new deep cycle acid battery (no warranty) which has a pinhole leak at one end. I was wonderin wether there is any common materials or glues that i could use to seal the leak in the casing cheersGegnus (talk) 23:58, 22 September 2009 (UTC)

Sorry, I don't have an answer - but there was a similar question asked here a couple of weeks ago. Those replies may be of some use to you... --Kurt Shaped Box (talk) 00:14, 23 September 2009 (UTC)

Same questioner double posting!--CruelSea (talk) 00:52, 23 September 2009 (UTC)

polythene is acid resistant, so if you get a polythene glue gun you can probably fill that hole. It will not take too much heat however. Graeme Bartlett (talk) 10:34, 23 September 2009 (UTC)