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July 28

Is there a combination of foods that can explode in a peron's stomache?

Are there any combinations of foods that, although each is individually tasty, eaten succession would explode? —Preceding unsigned comment added by 79.122.77.196 (talk) 04:42, 28 July 2008 (UTC)[reply]

I'm going to make a giant leap of faith here and assume that you mean stomach when you ask about "stomache" and by "peron's" you mean person's. These spelling errors aside, there may indeed be some combination of foods that meet your requirements but you'll not likely find help at Wikipedia unless you provide some context that shows your intentions to be benign. Otherwise, find another site to screw around with. -hydnjo talk 05:08, 28 July 2008 (UTC)[reply]

Unless you develop a taste for something exotic, I really doubt it. And hydnjo, let's assume good faith. 79.122 is probably refering to the urban legend that soda a "pop rocks" can make your stomach explode. The RefDesk gets much stranger questions that this. Plasticup ^T/C 12:10, 28 July 2008 (UTC)[reply]

To explode would require your stomach to be sealed off from the outside atmosphere, but it's not (see belching). --Sean 14:00, 28 July 2008 (UTC)[reply]

The stomach's venting doesn't always work (see "torsion" in dogs, cows, humans and presumably all mammals). This happens when the stomach twists and cuts off the normal intake or exit routes - like bending a garden hose sharply to cut off the flow. The condition can prove to be fatal within the hour. 196.2.124.253 (talk) 19:34, 28 July 2008 (UTC)[reply]

With the right preparation just "one wafer-thin mint" should do it. Richard Avery (talk) 15:53, 28 July 2008 (UTC)[reply]

I doubt there's an explosive combination, but I'm sure you could get something poisonous. Salt is the exact opposite: It's made from chlorine, a poisonous gas, and sodium, which would explode if you ate it. — DanielLC 16:47, 28 July 2008 (UTC)[reply]

Perhaps Evita Peron's and/or Juan Peron's stomach would explode if they took enough nitroglycerin pills ? StuRat (talk) 16:48, 28 July 2008 (UTC)[reply]

Hi. This doesn't make your stomach explode, but certain combinations of foods will cause food poisoning. For example, I don't have a source for this, but it is a widely known fact (in some countries) that eating persimmons and crab meat together will lead to severe food poisoning. There are also claims that other foods together will cause ill effects, like beef with chestnuts or carrots with turnips, but it's more likely that those might be made up. Thanks. ~A H 1^(TCU) 17:59, 28 July 2008 (UTC)[reply]

Hi. Here is an example of ill-matched foods (but will not make your stomach explode). Thanks. ~A H 1^(TCU) 18:05, 28 July 2008 (UTC)[reply]

Are we getting into Culturally specific illnesses like Fan death? 79.66.124.253 (talk) 20:41, 28 July 2008 (UTC)[reply]

A confusing post

(header added by hydnjo)

why does compensation point occurs onlu twice a day? —Preceding unsigned comment added by 219.90.105.176 (talk) 04:58, 28 July 2008 (UTC)[reply]

Is the teeny article compensation point any guide? Julia Rossi (talk) 05:41, 28 July 2008 (UTC)[reply]

Hint: photosynthesis is driven by sunlight - is there more sunlight at noon or at midnight? Franamax (talk) 08:52, 28 July 2008 (UTC)[reply]

Well the rate of photosynthesis will increase from zero at night to a maximum in the day, before returning to zero at night. Intersecting the rate of respiration once on the up and once on the down, these two points are the compensation points. Philc 0780 17:42, 28 July 2008 (UTC)

"Compensation"? Why not equilibrium point? 196.2.124.253 (talk) 19:38, 28 July 2008 (UTC)[reply]

Dolmen construction

Is this the right desk, but after looking at the article refd above Dolmen and finding a topstone that weighed 150 tonnes (I take it the article may mean 1.5 tonnes), how were they lifted into place? Julia Rossi (talk) 05:38, 28 July 2008 (UTC)[reply]

In colder climates, one way to do that would be through frost heave. Get the soil at the centre wet, when it freezes, it will lift the stone a little bit - then brace at the outside to keep it elevated. Next summer, pack more earth underneath and get it wet again. I have no idea if they did it that way, but maybe the aliens gave them some tips. Franamax (talk) 07:57, 28 July 2008 (UTC)[reply]

And I agree 150 tonnes is a little much. Switching units, rock is 160-190 lb/ft3, so a 20' x 8' by 1' slab would be around 12 tons. To get 150 tons, you need 50' x 9' x 4' - none of the pics look to be quite that impressive. Franamax (talk) 08:12, 28 July 2008 (UTC)[reply]

Agreed. Maybe the detail needs a point in the article. Will take it to the talk page. Julia Rossi (talk) 08:58, 28 July 2008 (UTC)[reply]

Hi! The article says The largest dolmen in Europe is the Brownshill Dolmen in County Carlow, Ireland.[citation needed] Its capstone weighs about 150 tonnes where as Brownshill Dolmen says The capstone at Brownshill, weighing an estimated 100 metric tons - so there is definately some error there. (though link 2 from that article gives a 'reputed 150 tonnes'.

Well granite weighs more than water and 1cubic meter weighs ~3 ton so 150 ton would be 50 cubic metre (100 tonn 33 cubic metre) giving 5x5x2m (or 3x2x5.5m) both of which seem optimistic estimates. Tens of tonnes seems more likely87.102.86.73 (talk) 11:18, 28 July 2008 (UTC)[reply]

If you expand this image

then you can see that the stone is ~2x5m on the front face - so maybe the figure is correct.87.102.86.73 (talk) 11:41, 28 July 2008 (UTC)[reply]

Following up a bit, the 150-tonne figure seems not unreasonable for the biggest stone pictured in the article. A general method of construction would be to build a long slope to the desired height and drag or use rollers to move stones into place. Vertical stones can be emplaced by digging a pit and tipping the stone in (some crushing of workers may occur, don't try this at home). The cap stone can be simply dragged over top, clear away all the dirt, bob's yer uncle - standing stones. Considering that these were for ritual/religious purposes, it's not unreasonable to think that this vast an effort would be expended over a period of years. Franamax (talk) 10:24, 28 July 2008 (UTC)[reply]

More likely method is to use a lever or wooden wedges to raise one end of the capstone by a few inches, then secure this end with wooden blocks and repeat at the other end, thus raising the stone incrementally on a wooden platform. An article on Megalithic tombs built by small teams in British Archaeology suggests this could be done with surprisingly small amounts of manpower - it says a team of 8 could have raised the capstones of the Stonehenge trilithons, weighing 40 tons each. But earthen ramps are also possible - I think there is a theory that many dolmens were originally buried in earth mounds, like passage graves. Gandalf61 (talk) 10:38, 28 July 2008 (UTC)[reply]

One theory (for specific dolmens) is that they weren't raised at all - but were dug into below, smaller stones inserted and the rest of the soil removed. This requires the capstones to be already there - erratics.87.102.86.73 (talk) 11:30, 28 July 2008 (UTC)[reply]

Thanks to you all for your convincing studies and proofs. Geniuses all (include the dolmen men) and will leave the article in tact. : ) Julia Rossi (talk) 09:32, 29 July 2008 (UTC)[reply]

The book Aku Aku, by Thor Heyerdahl, describes the methods used to raise the monoliths on Easter Island. Basically, yo use a long lever to raise the block a small amount, and then fill under it with small stones. repeat the process many many times. the block rises on a mound of small stones. A team of about twenty men raised a monolith more thna ten feet horizontally, and then tilted it to a standing postition by raising the head end further, taking less than a week to complete the procedure. They then used the same stones to build a ramp, and then used the same procedure to move a "topknot" stone up the ramp and place it on top of the monolith. I used a variant of thsi procedure to extract a neighbor's Chevy Suburban from a ditch. I worked alone, and used pieces of firewood instead of stones. It took about an hour to raise it about five feet. -Arch dude (talk) 02:30, 31 July 2008 (UTC)[reply]

which kidney works first?

As we all know, most humans have two kidneys. i want to know that which kidney (left or right one)starts to work first & which remains in stand by.Alok2n 00 (talk) 08:04, 28 July 2008 (UTC)[reply]

I don't think it works quite like that. Unless I'm mistaken, they both work simultaneously -- it's just that they're efficient enough that we can get by with only one of them if the other one is removed or stops working for some reason. -- Captain Disdain (talk) 09:54, 28 July 2008 (UTC)[reply]

Wait, you guys don't consciously choose? Plasticup ^T/C 12:13, 28 July 2008 (UTC)[reply]

Well, y'know, kidneys these days. They never do as I say. -- Captain Disdain (talk) 12:41, 28 July 2008 (UTC)[reply]

Have a look at Development of the urinary and reproductive organs#Metanephros and definitive kidney and Kidney#Embryology for more information. Zain Ebrahim (talk) 14:05, 28 July 2008 (UTC)[reply]

Refridgerators

what are the gases that used in refrigerators?what are they used for? —Preceding unsigned comment added by 117.196.134.20 (talk) 15:55, 28 July 2008 (UTC)[reply]

See refrigerant and list of refrigerants.--Shantavira|^{feed me} 16:11, 28 July 2008 (UTC)[reply]

That list is free/on us. StuRat (talk) 16:36, 28 July 2008 (UTC)[reply]

Groannnnn. 128.165.101.105 (talk) 19:27, 28 July 2008 (UTC)[reply]

Maybe we need a page for Hellmanism, the philosophy whose main tenet is, "Keep cool but don't freeze." OtherDave (talk) 23:38, 28 July 2008 (UTC)[reply]

Did Hellman work at the Mayo Clinic ? StuRat (talk) 03:00, 29 July 2008 (UTC)[reply]

Energy efficiency of a human compared to a robot

If we were to compare Asimo with a human, which is more energy efficient? Like if a human ate two burgers in the morning and Asimo had his batteries charged, then both go for a walk, which one uses their energy more efficiently? ScienceApe (talk) 16:03, 28 July 2008 (UTC)[reply]

The average person uses about 2000 Calories per day. That's about 100 watts. This is average, including sleeping. ~~Asimo uses about 25 watts while walking,[1] so he's more than four times as efficient.~~ Sorry, didn't read the article. It's a different robot that they were comparing to Asimo. Asimo uses 1200 watts,[2] so people are about twelve times as efficient. — DanielLC 16:27, 28 July 2008 (UTC)[reply]

I'd say the person is more energy efficient in most situations. This is because machinery often wastes so much energy, in the form of heat, that it gets too hot to touch, while people don't. However, machines have an "off" position, where they use little or no energy, while people don't. So, the robot is more efficient when off than the person when not working. If the machinery is electric, there is also the inefficiency of converting some other form of energy into electricity, delivering it, and storing it. Although, in this case, I suppose the inefficiency of human digestion must also be addressed. StuRat (talk) 16:32, 28 July 2008 (UTC)[reply]

Stu's comment about digestion makes me think the question is not completely answerable unless the Humans and Robots share a common fuel source, otherwise it's hard to contemplate overall efficiency. For example, the robot might be charged by a solar panel of certain dimensions. Could a human be sustained by food grown on farm land of that same dimensions? Probably not if the human's preferred fuel is hamburgers, but probably so if the human can be fueled by blue-green algae or some other such horrible food. APL (talk) 18:16, 28 July 2008 (UTC)[reply]

Perhaps alcohol and/or some organic oils can be used as fuel for both. StuRat (talk) 18:23, 28 July 2008 (UTC)[reply]

Haha alcohol! I'd like to see a workforce powered by that, but more importantly when a human digests alcohol, dont they only oxidise it to a ketone or carboxylic acid, and not fully, like in a combustion engine, to CO2 and water. Gving a much smaller energy release. Philc 0780 18:26, 28 July 2008 (UTC)

I thought grain alcohol was converted to sugars and then fully metabolized. StuRat (talk) 22:18, 28 July 2008 (UTC)[reply]

I'd say the robot because the robot is just walking, the human is walking, thinking, digesting, pumping blood round the body, processing waste, etc. You design a robot to do one task and it will generally do that one task far better than a human ever could. The good thing about humans is that we are extremely multi-purpose. --Tango (talk) 16:38, 28 July 2008 (UTC)[reply]

Would that mean it is foolish to design a robot in the image of a human, as it will only fail to be as versatile, however well it performs at individual tasks. Philc 0780 17:39, 28 July 2008 (UTC)

Humans (and other organisms) do have an "off" switch. It only gets used once. Recycling organic matter is a technology predating Homo Sapiens. Humans (and other...) are self replicating, whilst the production cost of robots is significant. Humans (and other...) are sustained by solar enery. Mind you, this is the Science Desk... --Cookatoo.ergo.ZooM (talk) 18:41, 28 July 2008 (UTC)[reply]

Production costs of humans are significant - I'm sure you've seen the statistics for the cost of bringing up a child. Humans work indirectly from solar energy, just like pretty much everything else. Where do you think the energy in oil comes from? --Tango (talk) 19:09, 28 July 2008 (UTC)[reply]

I pointed out that humans (and other organisms) are sustained by solar energy, implying that heat, food, fossil fuels (and pretty much everything else) is the result of the proximity of a star. I fail to see your point, Tango. --Cookatoo.ergo.ZooM (talk) 20:00, 28 July 2008 (UTC)[reply]

My point is that both humans and robots are powered the same way, so it's irrelevant to the question. --Tango (talk) 22:01, 28 July 2008 (UTC)[reply]

The problem is that it's quite difficult to convert the energy used by a robot and a human both back to the amount of sunlight used. However, if you have them both use a common fuel, like alcohol or other biofuels, then it isn't necessary to convert back to sunlight, you only need to compare the amount of the common fuel each uses (to perform a given amount of work) in order to determine the relative efficiencies. StuRat (talk) 22:15, 28 July 2008 (UTC)[reply]

That only works if the common fuel is an ideal fuel for both technologies. Otherwise you could swing the results either way you wanted by choosing an inappropriate fuel. APL (talk) 00:28, 29 July 2008 (UTC)[reply]

Those cost of bringing up a child statistic usualy involve bringing them up in a rich nation like USA. Presumably it'd be cheaper to manufacture your humans in a third world country. As a bonus, that's probably where 90% of the robot would be manufactured. APL (talk) 21:06, 28 July 2008 (UTC)[reply]

Common cold and sense of smell

Hi, sometimes when I catch a cold, my sense of smell gets altered in a strange way. In such cases, I always sense a characteristic smell which reminds me of pills or medicine, but I can't put my finger on what specific drug it might be. The smell gets stronger as the cold progresses, and I've never had the same sensation when I didn't have a cold.

Is there a place where I can read how the common cold affects the sense of smell? I want to see if other people experience the same thing too. (As a side note, when I get that smell, I almost always find that my nasal mucus gets dry and flaky easily as well.) --Kjoonlee 18:59, 28 July 2008 (UTC)[reply]

I can support your observation. Humans are not so bad when it comes to differentiating smells. Richard Feynman has fascinating anecdotes on that in his Surely You're Joking, Mr. Feynman! (holding a newly bought bottle from a dozen in your hand, or a book from a bookshelf, then trying to sniff it out). I'm currently testing privately the hypothesis that I can smell when someone has a (viral) cold. Support for this comes also from the fact that some viruses have distinct odors. --Ayacop (talk) 09:25, 29 July 2008 (UTC)[reply]

Panadol and fever

My question is, does panadol help cure fever or does it simply relieve the sensations of the patient while the body heals it's self?Bastard Soap (talk) 19:56, 28 July 2008 (UTC)[reply]

It relieves symptoms. This can be a benefit because sleeping helps the body heal itself, and can sleep easier when you aren't being kept awake by coughing and difficulty breathing. ~Amatulić (talk) 20:00, 28 July 2008 (UTC)[reply]

Hmm, no, it lowers the temperature (I can testify to that ;). From the article:

"The mechanism by which paracetamol reduces fever and pain is still a source of debate.[9] The reason for this confusion has largely been due to the fact that paracetamol reduces the production of prostaglandins — pro-inflammatory chemicals." -- Aeluwas (talk) 21:09, 28 July 2008 (UTC)[reply]

Yes, but fever is a symptom of the illness, so lowering the temperature is just reliving a symptom. It doesn't directly do anything to combat the illness, you would need some kind of antiviral drug for that in most cases (and there aren't any of those for most viruses as I understand it). --Tango (talk) 21:57, 28 July 2008 (UTC)[reply]

Not only that, but Panadol's lowering the temperature may actually prolong the illness, since a fever is the body's response to combatting bacterial or viral threats. According to Fever#Usefulness of fever, a fever has some important functions in the healing process.

Indeed, one traditional way to get over a flu more quickly is to "break" the fever by helping it along (sweating under blankets, sitting in a steam bath, etc.) rather than suppressing it. That's not always safe to do, though. ~Amatulić (talk) 22:14, 28 July 2008 (UTC)[reply]

For the record it's also worth noting that if elevation of the body's temperature goes unchecked, the worst fevers can result in permanent brain damage and even death. Often, symptoms are treated because they are uncomfortable aspects of the illness but they can also be dangerous facets of the condition that need to be addressed for the patient's safety. --Shaggorama (talk) 07:49, 30 July 2008 (UTC)[reply]

How to answer this child's question

"Why does a mirror reverse only right and left, but not up and down?"

I have an answer inadequate for a child about how reflectance works, but I want to know what others would say. ~Amatulić (talk) 20:00, 28 July 2008 (UTC)[reply]

Basically, the mirror doesn't reverse anything. It only appears to reverse left/right because your hands are mirror images of each other. Looking at the mirror and moving your right hand, the hand on the right from your point of view moves. If you move your head, your head moves toward the top of the mirror. Your right hand only looks like your left hand because of your own internal symmetry. We don't have top/bottom symmetry, so it doesn't appear to flip that. (I'm sure there are probably better explanations out there, probably with pictures, too). --Bennybp (talk) 20:38, 28 July 2008 (UTC)[reply]

It exchanges back and front, not up and down. It's like looking at your twin, reaching the right hand to shake it. 93.132.186.140 (talk) 20:44, 28 July 2008 (UTC)[reply]

If you hold a piece of paper up to a mirror so that it is facing you and not the mirror, you will have to rotate it 180 degrees for it to face the mirror. Typically, we rotate things horizontally because we have an instinctive desire to keep things "right-side-up", however, nothing is stopping you from rotating it vertically.

Essentially, the reason the page is backwards is because you turned it around to face the mirror. If you turned it over then the left side of the page would still be on the left, however the page would be upside down.

Words printed on a clear piece of plastic make this more obvious. APL (talk) 21:00, 28 July 2008 (UTC)[reply]

That doesn't sound exactly right... the mirror image is projectively symmetric, not rotationally symmetric. You cannot rotate the object in any way to make it look like the mirror image (printed text would be a perfect example of this). Nimur (talk) 22:35, 28 July 2008 (UTC)[reply]

To be clear, the image is always flipped. It's chirality is always reversed. But the question was why left-to-right and not up-to-down. The answer is that there is no intrinsic difference. It just depends on how you're holding it. APL (talk) 00:21, 29 July 2008 (UTC)[reply]

As 93.132 says, mirrors reverse front and back. We define left and right in terms of which way we're currently facing, which means they get reversed too, whereas we define up and down with respect to Earth's gravity and that isn't changed. If you are facing the mirror which is north of you and point east, your reflection will also point east, since east and west don't depend on which way you're facing. --Tango (talk) 21:07, 28 July 2008 (UTC)[reply]

there are mirrors that reverse up and down. Tell your young friend to look into a spoon and describe what they see. --Shaggorama (talk) 22:09, 28 July 2008 (UTC)[reply]

I think it's fair to assume the OP was talking about planar mirrors. Obviously different shaped mirrors do different thing. --Tango (talk) 22:11, 28 July 2008 (UTC)[reply]

(Blush) As a physicist, I should have known better than to omit a key detail like that. Yes, I was referring to mirrors that exhibit a virtual image, which include planar and convex mirrors, and concave mirrors when you are closer than the focal length. A child wouldn't understand a conjugate mirror either. Tango's answer, confirming the anon's answer, said it best. Thanks. ~Amatulić (talk) 22:22, 28 July 2008 (UTC)[reply]

Take the mirror off the wall and put it on the floor, and if it can take it stand on it. You will see up and down reversed. The mirror in front of you is reversing front and back, not left and right. The viewer is imagining turning around. Graeme Bartlett (talk) 02:39, 29 July 2008 (UTC)[reply]

The way I find easiest to explain this is that mirrors don't reverse left and right - rather, other people do. When other people want to look at you, they turn around and face you. There are two ways to do this, by flipping over and doing a handstand (this will reverse their top/bottom in your view, but keep their left/right the same), or, by turning around sideways (this will keep their top/bottom the same in your view, but reverse their left/right). The reason the mirror image seems to be raising the opposite hand to you is because we are accustomed to other people's left/right being reversed when they are facing us. Maelin (Talk | Contribs) 05:52, 29 July 2008 (UTC)[reply]

That's an interesting perspective. Thanks. ~Amatulić (talk) 21:53, 29 July 2008 (UTC)[reply]

Respiration

Is it fair to say that the primary function of respiration is to regulate PCO2 within narrow limits ~40mmHg? That oxygen isn't because under normal circumstances, O2 capacity of blood is surplus to requirements.

Seeing as we die if we run out of oxygen, I'd they both constitute primary functions. Your statement would be like saying the primary function of the mouth is to consume water, since we carry a greater excess of processed food...Someguy1221 (talk) 21:36, 28 July 2008 (UTC)[reply]

I don't think you understand the essence of my question, which relates to control of respiration and not really questioning the function of respiration per se.

As I understand it, the body decides when it needs to breath based on CO₂ levels, not oxygen levels, if that's what you're talking about. Control of respiration should help you. --Tango (talk) 21:55, 28 July 2008 (UTC)[reply]

As both supplying oxygen and removing excess carbon dioxide are absolutely essential, it seems quite pointless to call one a primary function and another a secondary function. StuRat (talk) 22:23, 28 July 2008 (UTC)[reply]

Here's a thread that may be of interest. Apparently we have bad O2 sensors and good CO2 sensors. The thread's a little long... Franamax (talk) 22:58, 28 July 2008 (UTC)[reply]

I just saw a bat!

Hi. I presume this is the appropriate desk to ask questions about animals? Like I said, a rather large bat just flew over me. Are there many bats in the vicinity of Eaglesham? I have seen them before but only very rarely. What sort of species of bat would live in my area? Where do they sleep during the day?; hanging upside-down in trees? Willy turner (talk) 22:20, 28 July 2008 (UTC)[reply]

There are bats all over the world. According to the bat article, of all the different species of mammals, about 20% of them are bats. The article will tell you much more if you're curious. ~Amatulić (talk) 22:26, 28 July 2008 (UTC)[reply]

Most bat species prefer more protected areas, such as caves or attics of houses, barns, and other buildings. Those that eat insects are quite helpful, while fruit bats just make a mess and vampire bats are downright creepy. StuRat (talk) 22:30, 28 July 2008 (UTC)[reply]

There are bats in Scotland. You may look at http://213.121.208.4/pdfs/education/bat.pdf and http://www.first-nature.com/bats/ for the bat species found in Scotland specifically and in Great Britain in general. They are fascinating animals. Enjoy. --Dr Dima (talk) 22:37, 28 July 2008 (UTC)[reply]

Thanks. btw, ive heard of bats living in attics before, but is this a very common home for them? To get outside to hunt the house would have to have a hole in the wall or roof. Surely most owners in non-arid areas would notice this as it would result in water getting in? Willy turner (talk) 23:00, 28 July 2008 (UTC)[reply]

An aforementioned hole in the wall is usually referred to as a window ;) - just kidding. Now seriously, yes, bats may and occasionally do live in the attic of an occupied house. And yes, they need an opening to fly in and out; but it need not be large. --Dr Dima (talk) 00:44, 29 July 2008 (UTC)[reply]

Yes, my mom had bats in her attic (even before she went senile, :-) ). They got in through a plastic attic vent cover, under the eaves, which they had broken. The lack of any insects was appreciated, but not the bat poop in the attic. They were quite difficult to spot because they were silent and black, only came out at night, and generally avoided humans. They usually only gave the impression of a passing shadow. The pest control man repaired the broken vent cover after they had left for the night to hunt. The bats came back home and found that "the lock had been changed". :-) StuRat (talk) 02:54, 29 July 2008 (UTC)[reply]

Take they've moved on from belfries because the articles don't have any. You could always talk to the Central Scotland Bat Group, a bat's only help group through here[3]. Julia Rossi (talk) 08:48, 29 July 2008 (UTC)[reply]

As mentioned above, bats do like to live in peoples homes, under tiles, any small cracks in walls and of course in the attic. Please note that in the UK all bats are strictly protected and it is illegal to disturb a colony, in any way, see http://www.defra.gov.uk/farm/wildlife/bats/index.htm Jdrewitt (talk) 06:44, 1 August 2008 (UTC)[reply]

Why do black things radiate more?

I've looked at black body, in case people are wondering. And I understand the overall argument - "Black stuff absorb more. This means they must radiate more to stay in thermal equilibrium, if they are around stuff of the same temperature. But the amount they radiate is independent of what's around it. So black things at the same temp radiate more." Still, whilst this is an interesting logical proof, I'm wondering if there's any mechanistic explanation - why is it that whatever makes an object reflect light of a certain frequency will also reduce the radiation of that object if heated?--Fangz (talk) 22:54, 28 July 2008 (UTC)[reply]

If it would make it easier for you, you can imagine a time reversal. A time reversal of a reflection is also a reflection; but absorption and emission are time-reversals of each-other. Therefore, the probabilities of absorption and emission are governed by the same matrix element (that of electric dipole, usually) in the space spanned by the eigenstates of the electron-in-external-field Hamiltonian. You may read Atomic spectral line article, or - better yet - you may take any of the quantum mechanics textbooks that deal with the subject and figure it out in detail. It is not trivial, so patience is your friend here. --Dr Dima (talk) 00:21, 29 July 2008 (UTC)[reply]

question about Uniform circular motion

If a bucket is being swung in the vertical plane by a massless/frictionless rope, and only Tension and Gravity act on the bucket, it can't achieve uniform circular motion.

Am I right? Because when the bucket is horizontal there is a component of force straight down, and the tension is straight sideways thus the acceleration is not pointing to the center. Thanks, I have spent an hour on this. Sentriclecub (talk) 23:51, 28 July 2008 (UTC)[reply]

Yes, you're quite right. Algebraist 23:58, 28 July 2008 (UTC)[reply]

Thanks, it is rare that a physics professor at MIT slips up although he didn't necessarily exclude that there wasn't a rocket attached to the bucket.

Update Wait then how can a bucket do a circular path? I imagine that the component of (mg) in the direction of the velocity (and thus perpendicular to the acceleration) increases the angular velocity all-while perfectly balancing the F = ma, and since the angular velocity is variable (and so must be either the direction of acceleration or the magnitude or both!)... Resolved Sentriclecub (talk) 01:18, 29 July 2008 (UTC)[reply]

I think you've got it, but just to make sure: The bucket can move along a circular path, but not at uniform angular velocity, for exactly the reasons you give. --Tango (talk) 02:23, 29 July 2008 (UTC)[reply]

The video was tldr, but the prof may have made the same mistake I made when reading this question, which was reading "uniform circular motion" and thinking "simple harmonic motion". SamuelRiv (talk) 00:27, 31 July 2008 (UTC)[reply]

Just to be pedantic, it is possible for the bucket to perform uniform circular motion under the conditions described. We just need to vary the tension force's magnitude and direction. To maintain the uniform circular motion all we need is for the resultant acceleration on the bucket to always point at the same magnitude to a fixed point (the centre of our orbit). In the vertical case the bucket's acceleration isn't only due to the tension but also due to gravity. So, if we were holding the string, we could move our hand around a bit and tug at slightly different strengths to ensure that the resultant force always pointed to the same place. The bucket won't be orbiting your hand but it could be orbiting in uniform circular motion. --Peter Ballett (talk) 22:25, 3 August 2008 (UTC)[reply]

July 29

What was the last species to become extinct?

In other words, what species most recently became extinct? 71.181.253.33 (talk) 00:24, 29 July 2008 (UTC)[reply]

According to Holocene extinction event, the current rate of extinction may be as high as 140,000 a year, most of which will be species never discovered by humanity. Thus your question is unanswerable. Algebraist 00:30, 29 July 2008 (UTC)[reply]

In that case, what would be the most famous recent extinction? --Kjoonlee 01:29, 29 July 2008 (UTC)[reply]

Altho, I can't find a list directly has the information you want, you could figure it out from List of extinct animals & List of extinct plants. ---J.S (T/C/WRE) 01:46, 29 July 2008 (UTC)[reply]

(ec) The last documented species to be officially declared extinct is Begonia eiromischa. Using the crude equation 'famous'='I've heard of it', the last famous extinction is the Baiji (assuming it is extinct; a few might survive, but they won't last long if so). Algebraist 01:48, 29 July 2008 (UTC)[reply]

Probably the most famous extinction of the last century is the Passenger Pigeon, which not long before had migrated across north America in flocks a billion strong. Algebraist 01:53, 29 July 2008 (UTC)[reply]

To go from "probably extinct" to "extinct", the IUCN requires that no members of a species have been observed for at least 50 years. That uncertainty means that "recent" extinctions are necessarily not very recent. Dragons flight (talk) 03:52, 29 July 2008 (UTC)[reply]

Then let's ignore the IUCN list for the moment, since declaring extinction is distinct from actual extinction. --Kjoonlee 04:28, 29 July 2008 (UTC)[reply]

But that's precisely the problem. How do you know when the last Baiji died (presuming it really has died, which is easily not the case)? How do you know if it died before the last whatever other species you want to name (that was declared possibly extinct at around the same time, I'm obviously not talking about the dodo here) Nil Einne (talk) 15:28, 29 July 2008 (UTC)[reply]

Baiji was a recent probable extinction of a well known species-- declared "functionally extinct". Even if one or two remain they'd still almost certainly die out. And for the record, the IUCN Red List does not require 50 years -- but they do require "no reasonable doubt that the last individual has died." which means Baiji are still listed as Critically Endangered/Possibly Extinct [4] —Pengo 12:35, 29 July 2008 (UTC)[reply]

No baiaji have been taken into captivity? Usually I'm not for captivity, but when it's that or extinct... Pfly (talk) 02:42, 31 July 2008 (UTC)[reply]

There were attempts. Have a look at the article which lists 6 individuals. Note that for a population to sustain itself you generally need at the very least 100 individuals. That's to allow genetic diversity and avoid inbreeding. 60.242.139.27 (talk) 23:25, 31 July 2008 (UTC)[reply]

Organ Donation

which are the organs that can be donated by a brain dead person? why can't all organs be donated?Shraktu (talk) 05:07, 29 July 2008 (UTC)[reply]

All organs can be donated (for example, by leaving one's body to a medical school for dissection). But not all organs are useful for transplant. Most commonly, the organs and tissues used are corneas, skin, bone, kidney, liver, heart, lung. Take a look at Organ_transplant for other transplantable organs. - Nunh-huh 05:22, 29 July 2008 (UTC)[reply]

If the individual is "brain dead" then presumably they are still alive. I'm fairly certain it is considered unethical to remove someone's vital organs (without the intent of replacing them) until after their heart has stopped and they are definitively declared deceased, although this practice would almost certainly provide for more viable organs. Even Dr. Kevorkian didn't directly kill any of his right to die patients. I think they sometimes will push drugs that help preserve a brain dead patient's organs in anticipation of their death, though. --Shaggorama (talk) 08:01, 30 July 2008 (UTC)[reply]

On the contrary, in jurisdictions where "brain dead" has a legal meaning, a brain dead person is dead. A brain dead person on a respirator is a very common source of organs, and removing the organs is indeed done while the heart is beating. - Nunh-huh 12:00, 30 July 2008 (UTC)[reply]

Wow, that's uh...unexpected and scary. I take it the hospital pays for the time the individual is on life support then? I understand many amilies choose to keep "brain dead" individuals on life support for sometime in the hopes that they might come out of the coma. It does happen periodically. I'd feel pretty shitty if I found out I was paying to keep a family member alive while their liver was cleaved out of them. Mind finding some jurisdictions for me? I'd be interested in reading their policies and ethical discussions on this topic. --Shaggorama (talk) 09:47, 31 July 2008 (UTC)[reply]

Well, first: brain-dead people don't come out of comas. You're talking about people who are something other than brain-dead if there's any chance whatsoever they're revivable. Brain-dead means (there are slight variations from place to place, but in general:) irreversible end of all brain activity, including the inability to trigger a respirator, as measured by separate EEGs measured 24 hrs apart, and certified by more than one physician. It's something quite different from the so-called persistent vegetative state coma-patient cases you read about. Once someone's brain-dead, costs for the respirator and hospital are charged to the organ recipient, not the donor. Actually, looking now, we have articles on this: Uniform Determination Of Death Act (for U.S. jurisdictions), brain death, persistent vegetative state. - Nunh-huh 13:19, 31 July 2008 (UTC)[reply]

Feasibility of a vapor and vacuum-based engine?

I apologize if this is too far beyond the scope of the reference desk, but I'm hoping someone more versed in mechanics and fluid dynamics can entertain a thought that I had. Considering that one of the drawbacks of the standard steam engine is the necessity of a fuel source and therefore thermal waste, I imagined something a bit different, and I'm severely interested in knowing if there are similar ideas or instances out there.

In my version, a chamber filled with water or a low-boiling liquid is subjected to a vacuum created by the same liquid being forced over a liquid-impermeable membrane. The subsequent vapor is collected, perhaps with the encouragement of a turbopump, before it can escape into the flow system, compressed by an electric apparatus (but not to the point of liquification, which seems to work for the steam engine) and then injected (Is this possible? Can one inject air from a vacuum without condensation?) to the pistons, which also probably have to be under vacuum to eliminate the need for a high-pressure injector. Perhaps a timed mechanism could be used to vent the "spent" vapor, allowing the piston to fall, after which it is fed into a condenser and back into the vacuum flow--and eventually back into the tank.

Please forgive me if some part of this makes it a horrible idea in terms of thermodynamics. :) Goodbyegravity (talk) 07:35, 29 July 2008 (UTC)[reply]

-The problem I see is that your process could hypothetically generate power in the reverse process also (the whole process ran backwards). Check out Sterling Engines on youtube and Stirling Engine here at wikipedia. The problem I see is that the vapor will strongly resist leaving the vacuumoid region that it entered upon leaving the liquid (or water your choice). You can't "suck it" out, you'd have to displace it with another gas, or if you wish to convert it back to a liquid (condensation) is a very costly chemical reaction. That is your bottleneck. Its a good idea though, creative and original, I like it. Sentriclecub (talk) 09:26, 29 July 2008 (UTC)[reply]

I didn't quite follow everything, but what I did did seem to make sense though the reversability of the reaction makes me question it a little bit. DISCLAIMER: I'm not a lawyer. However, you should know that because all content on Wikipedia is lisenced under the GFDL thereby putting your idea into the public domain for free use with unlimited changes as long as there is attribution to the original source. If I am interpreting correctly, I believe this makes your idea now non-patentable, but you should really ask someone more experienced. EagleFalconn (talk) 14:16, 29 July 2008 (UTC)[reply]

Aside from the energy input from the proposed pumps and compressors, it seems to me that you're hoping to use the semipermeable membrane as a sort of Maxwell's demon. If you're hoping to see more energy out than you put into the pumps and compressors, then you're going to be disappointed. TenOfAllTrades(talk) 15:12, 29 July 2008 (UTC)[reply]

Thank you all so much for your responses! I am not certain what is meant by the possibility of the reverse process; the main vacuum flow should be capable of receiving liquid from one direction, and liquid should not enter it where the flow leads into the containing tank, if that is to what you are referring. The condensation mechanism is indeed what I feared to be the bottleneck as well, but perhaps it would only have to be repressurized to change faces (this might make some other parts of this device useless). The page on Maxewell's demon is a little complex for this early in the morning, so I will check it out in a little while. And @ Eagle: if this idea pops up in some incarnation, I wouldn't wish it to be patented anyway. I want to leave a lasting impression on chemistry, not the automotive market. :) goodbyegravity (talk) 18:00, 29 July 2008 (UTC)[reply]

I think possibility of getting energy from the reverse process implies that it would be a perpetuum mobile, which proves that it can't work. But in any case, I think you would be interested in the Heat pump article and the articles it links to. Using the waste heat from engines or other temperature differentials to produce electricity is not a far-fetched idea. EverGreg (talk) 10:32, 31 July 2008 (UTC)[reply]

Teeth during pregnancy

Please see Wikipedia:Medical disclaimer : as such we cannot give medical advice.

This question has been removed as it may be a request for medical advice. Wikipedia does not give medical advice because there is no guarantee that our advice would be accurate or relate to you and your symptoms. We simply cannot be an alternative to visiting the appropriate health professional, so we implore you to try them instead. If this is not a request for medical advice, please explain what you meant to ask, either here or at the talk page discussion (if a link was provided).

question and responses hidden

My wife is about three months into her pregnancy and has just discovered she has started growing a new tooth! Could this be related to the pregnancy or just coincidence? Iiidonkeyiii (talk) 09:26, 29 July 2008 (UTC)[reply]

Well, humans go through 2 sets of teeth in their lifetime. Pregnancy horomones like FSH and LH do not play a role, sorry. Sentriclecub (talk) 09:42, 29 July 2008 (UTC)[reply]

This is too much a request for a medical diagnosis to be answered. You have given a symptom (what you believe to be a new tooth and not a lodged popcorn kernel or bone tumor or one of many other things that have been thought to be a new tooth by people in the past). You have asked for validation of your diagnosis: pregnancy hormones leading to new tooth growth. We do not validate self-diagnosis. This is a reference desk. If you want references for studies on the effects of pregnancy hormones, please ask. -- kainaw ™ 12:11, 29 July 2008 (UTC)[reply]

What ? Since when is growing a tooth a "medical condition" ? It's a normal part of human growth, and, in this case, most likely just the coincidental natural eruption of a wisdom tooth. Calling this a medical diagnosis is quite absurd. And suggesting that the poster can't tell a tooth from a popcorn kernel is equally absurd. StuRat (talk) 03:56, 30 July 2008 (UTC)[reply]

(Not answering because of diagnosis issue, just asking for clarification.) How many adult teeth has your wife had before? 28? 32? Some other number? —Keenan Pepper 13:16, 29 July 2008 (UTC)[reply]

Although I cannot say what's happening in your wife's case, I will note that wisdom teeth usually grow in during the teens/twenties, even if a person is not pregnant. At any rate, I would recommend consulting a Dentist, as the appearance of new teeth, even wisdom teeth, has implications for the alignment of bite. Teeth that grow in during adulthood (such as wisdom teeth) are usually removed as they may push against old teeth, forcing them out of alignment. Depending on how they grow in, they may not *need* to be removed, but only a licensed Dentist who can physically examine the patient's mouth can make a proper determination. -- 128.104.112.147 (talk) 17:57, 29 July 2008 (UTC)[reply]

I have heard of some people growing three sets of teeth in their lifetime. Cecile Adams will probably debunk me, but I'll have a look for a link. Plasticup ^T/C 19:04, 29 July 2008 (UTC)[reply]

Hyperdontia: growing more teeth than normal or even growing a third set of teeth. This happened to one of my relatives, but I forget what he did about it. A visit to the dentist is an excellent idea.--El aprendelenguas (talk) 20:36, 29 July 2008 (UTC)[reply]

Please note that a discussion on the talk page about whether this question constitutes medical advice may be found here: [5]. StuRat (talk) 05:28, 30 July 2008 (UTC)[reply]

Nature paper

I am doing some research for a paper about Wikipedia's reliability and I have come across this paper. However I do not have a subscription to Nature and am wondering if there is a copy stored on a Wikipedia server someplace? Or perhaps someone has the PDF? Thanks! P.S. Can you copy whatever answer onto my talk page? Bstone (talk) 10:56, 29 July 2008 (UTC)[reply]

Please note that Wikipedia is licensed under the GFDL. Because of this, placing a PDF of this article onto Wikipedia would violate the authors' copyrights by co-opting the article without their permission and placing it into the public domain. While academic fair use is common, particularly among peer reviewed journals, doing this would not fall within those terms. EagleFalconn (talk) 14:20, 29 July 2008 (UTC)[reply]

Minor quibble—material on Wikipedia is not by default in the public domain. That term has a specific legal meaning, and Wikipedia emphatically does not release its content in that way. The GFDL – under which our textual content is released – is a specific license enumerating the ways in which we permit our still-fully-copyrighted material to be (re)used. Care should be taken not to conflate or confuse 'GFDL-licensed' and 'public domain'. That said, EagleFalconn is entirely correct that Wikipedia does not can cannot host material that is not under a free license, and that posting an article without the copyright holders' permission would be an abrogation of their rights. TenOfAllTrades(talk) 15:04, 29 July 2008 (UTC)[reply]

From a quick Google [6], I found this [7] apparently legit reproduction (although I have my doubts whether Trevor was really supposed to make it publicly accessible but he is apparently a librarian so one would hope he knows what he's doing Nil Einne (talk) 15:11, 29 July 2008 (UTC)[reply]

(Why would one assume a librarian knows anything about copyright law? Usually they aren't any more informed than anyone else on such things. But it's his problem, not yours.) --98.217.8.46 (talk) 20:50, 29 July 2008 (UTC)[reply]

I would expect a librarian to be familiar with enough copyright law to know which things in their library it's ok to put under the photocopier. More than that, they probably aren't generally too knowledgeable. --Tango (talk) 02:06, 31 July 2008 (UTC)[reply]

I'm not talking about knowledge of copyright law, but knowledge of what stuff they may legally re-distribute, copy, etc and also the smarts to know who to ask when they're not sure. Perhaps I'm mistaken but I expect most would need this sort of knowledge because if not, they're the ones responsible when they screw up and given what they do. And actually, it is against wikipedia policy to post links to sites violating copyright violation and I avoid doing it as much as possible hence the reason I was unsure whether to post this. In any case, I would expect even if their knowledge is not sufficient, the average librarian is more informed then the average person about copyrights because it's something they do deal with to some extent whereas most people don't deal with copyrights much. (I mean how many people have you come across who think "if someone put it on the internet it's fine for me to copy it whenever and however I like"? For me the answer is a lot but I would expect most librarians at least have more knowledge then this.) Nil Einne (talk) 08:46, 1 August 2008 (UTC)[reply]

If you do use this article as a source, please also read the additional data subsequently released by Nature, Britannica's reply, and Nature's reply to Britannica's reply (all of which are linked from the Nature page). Despite its publication in Nature this study doesn't seem to have passed peer review. My subjective impression after reading the whole exchange is that the study was poorly conceived and executed and its results are scientifically valueless. -- BenRG (talk) 19:09, 29 July 2008 (UTC)[reply]

The study compares the Wikipedia you can get for free from the internet to the Britannica you can get for free from the internet. In this way its pretty reasonable, although Britannica has additional layers you can obtain for cash. Wily D 20:53, 29 July 2008 (UTC)[reply]

The question is whether it was reasonable to compare the two, but whether it was executed and formulated well. Personally I'm not so sure whether it was even reasonable—the sorts of things Wikipedia is good at are things that Brittanica is often bad at; the sorts of things Wikipedia is bad at are things that Brittanica is usually pretty good at. In any case, Brittanica and Wikipedia have very different approaches not just to content generation, but content epistemology: Brittanica wants to be correct, Wikipedia wants to report on what other people think is correct. There's a big difference there. --98.217.8.46 (talk) 22:57, 29 July 2008 (UTC)[reply]

Although it doesn't fall strictly under the scope of their project, in the future you may want to try posting requests for published material like this at Wikiproject Resource Exchange. It's only intended to assist research for wikipedia articles, but it's an incredibly powerful and underused resource, so I imagine any reasonable request you post will be answered. --Shaggorama (talk) 08:07, 30 July 2008 (UTC)[reply]

I actually took care of the OP request within about 30 minutes and should have posted to that effect here - but I was responding on the Help Desk, acting as a WP:WRE member.

I did mention the library at the help desk and I'll wholeheartedly second Shaggorama - powerful, underused and somewhat unknown resource where you can get copies of most everything. The more people who use it and the more people who provide to it, all the better! I've just now found that my library card gives me access to all kinds of previously costly resources, so I need to update my entry over there. Please everyone, the more we participate at the Resource Exchange, the more powerful it will be. Franamax (talk) 02:20, 31 July 2008 (UTC)[reply]

Different approaches doesn't really matter however since from a user's POV, all that matters is the result. Remember this isn't about politics. Also remember that Nature is a scientific journal. Their primary interest is science. I don't think it's surprising then that if they want to compare the two, they will do it on science, not of Pokemon or historic people or developing country politicians or whatever. This obviously isn't a complete comparison of the two, but a comparison of the two in a scope of most interest to the journal's audience. And I would say it is relevant. While encylopaedia's are usually not used in an academic context, they are useful on occasion sometimes even for student papers. If you're going to be rejecting use of wikipedia because it's inaccurate but accepting Britannica, then you want to be sure your view is correct. Also, most scientist's have interest in how well people understand science. As both wikipedia and Britannica are a big part of that, with wikipedia becoming even more significant, it's likely to be of interest to see how good, or poor, a job they are doing of it. Finally remember that most people I think when looking for something, if they are going to check an encylopedia are not going to have the detailed knowledge of which encylopaedia they should choose. Nil Einne (talk) 09:01, 1 August 2008 (UTC)[reply]

Organic chem

My daughter is 1 class away from graduation(organic chem). She must have this class and has twice failed it. Is there something like an organic chem form dummies textbook that would help?129.112.109.251 (talk) 14:36, 29 July 2008 (UTC)[reply]

You might try an online retailer or a large bricks-and-mortar bookstore. Organic Chemistry I for Dummies is in stock on Amazon.com. Also available is The Complete Idiot's Guide to Organic Chemistry, if you're looking for other humbling titles. (There is apparently an accompanying workbook available for purchase with the Dummies title.) Note that I haven't reviewed either book and can't offer a specific endorsement, but it appears (from Amazon's Customers Who Bought This Item Also Bought section) that there are a number of titles in this field—your daughter is by no means the only person to have difficulty with organic chemistry. TenOfAllTrades(talk) 14:58, 29 July 2008 (UTC)[reply]

I'm actually holding my Organic chemistry "Quick study guide" UPC 781572-225541 It is $5 from [here barcharts.com] and their phone number is 1800 230 9522 I never liked organic chemistry, so I used flash cards and laminate study guides. Sentriclecub (talk) 15:01, 29 July 2008 (UTC)[reply]

Find out why she failed. Organic chemistry, unlike other chemistry classes, requires the memorization of a lot of compound structures. If she isn't memorizing them, she won't have a shot at answering the questions on the exams. If she is memorizing them, she is failing in the interaction between compounds. Since those are two very different areas of learning (one is memorization, the other a functional understanding), you don't want to waste time focusing on one when the problem is the other. -- kainaw ™ 15:01, 29 July 2008 (UTC)[reply]

Second Kainaw's point. I'm a free tutor for organic chemistry and so I see all types of people. One of the really common mistakes I see is people taking that point too far. While organic does, unfortunately, require some level of memorization its important to choose what to memorize and what to learn. Hopefully since your daughter has already taken the class twice she has at least a basic level of understanding of much of the material. Assuming she's taking a one semester course intend for biology majors or the like, the really important thing to memorize is nomenclature.

Outside of that, the vast majority of organic chemistry she'll encounter can be understood as lewis acid and lewis base behavior. Find the places of high electron density and find the places of low electron density, thats your nucleophile and electrophile respectively. Being able to identify those areas is really important. I suggest she review her general chemistry textbook on VSEPR theory. Our article is decent on the matter, but her textbook is probably better. Have her read our article on the Sn1, Sn2, Elimination reactions (for E1 and E2) and review her textbook on those reactions before the semester starts. A thorough, complete, detailed understanding of those four reactions is key. If she can understand those in terms of Lewis Acid/Base behavior, she can understand the rest of the class in terms of those reactions (with the notable exception of the Diels-Alder reaction). If she gets really gung ho, have her read all of [8]. EagleFalconn (talk) 15:34, 29 July 2008 (UTC)[reply]

One thing I've noticed about ochem (I'm still taking it; see my later question) is that a lot of stuff is quite difficult to derive from basic principles as opposed to inorganic chemistry. So like others have said, you do need to memorize. But you also need to be able to apply memorized concepts to new problems. I have found that the only way around it is lots of practice problems. Lots. Doing all the ones in the book might not even be enough, if she has failed it twice. --M1ss1ontomars2k4 (talk) 04:35, 2 August 2008 (UTC)[reply]

igneous rocks

igneous rocks are classified on the basic of what factor?

See Igneous rock and ask again if you don't get an answer in the first sentence. -- kainaw ™ 17:27, 29 July 2008 (UTC)[reply]

do we explode in outer space?

Hi, if you were released into a zero pressure environment, like outer space without a suit, would you explode because of the greater internal pressure? Would your blood boil instantaneously? Thanks in advance, 202.89.166.179 (talk) 17:32, 29 July 2008 (UTC)[reply]

Please see Human_adaptation_to_space#Unprotected_effects. -- Coneslayer (talk) 17:35, 29 July 2008 (UTC)[reply]

Thanks very much for the link. I haven't read it in full yet, but it seems like a brilliant article, and pretty much on the way to featured status. Fascinating stuff. 202.89.166.179 (talk) 18:04, 29 July 2008 (UTC)[reply]

Follow up question

I just noticed that the article mentions barotrauma, but doesn't explain why the astronaut who was exposed rapidly to near-zero pressure didn't suffer/ die from it. The barotrauma article itself doesn't help much, either. Does anyone know what the reason might be? 202.89.166.179 (talk) 18:16, 29 July 2008 (UTC)[reply]

S/he doesn't explode because skin is tough enough to withstand a sudden drop from one atm of pressure to (near) zero pressure. See Explosive decompression and Cecil Adams' take here. --Sean 14:31, 30 July 2008 (UTC)[reply]

fast room cooling solution

Dear Wikipedians:

I love my little study upstairs. It is a small, cubic room that is enclosed (when I close the door). I loath to part with my study.

However, one big problem is that during the summer, the central A/C does not have enough power to keep my little study cool (and since warm air travels upwards, hot upstairs is a common problem that plague all north american houses). This gets especially bad in the afternoon when the sun shines directly into my study through the window. So I'm forced to flee my little study into my dad's study downstairs. And since it's my parent's house, there's no way that I can request the drilling of a hole on the wall of my study for me to install a window type air conditioner just for myself.

So I am wondering, is there any simple way to cool my study down fast? I am thinking of making big chunks of ice and put them into my study to absorb heat. But thought dry ice/liquid nitrogen might be faster for this purpose. From Michio Kaku's documentaries I know now that liquid nitrogen is as cheap as milk, so that's why I thought liquid nitrogen might be feasible for me, but I'm afraid I might asphyxiate if I don't do it properly.

I'm also wondering if there are small/portable air conditioners that don't require me to drill holes in walls in order to use them.

Any suggestions are much appreciated.

76.68.11.220 (talk) 20:38, 29 July 2008 (UTC)[reply]

How about just a fan? And are your parents really going to be that unhappy about the two small screws used for most window units? You could offer to spackle them over if they want to sell the house. (God knows that the two screw holes are going to be the least of their problems these days.) As for "alternative methods", I suspect it will be far too much hassle to try and cool your room with chemicals of any sort, and probably a losing battle in any case. --98.217.8.46 (talk) 20:47, 29 July 2008 (UTC)[reply]

First off, I'd recommend using curtains to block the sunlight coming in through the window. Judicious use of curtains can keep a room substantially cooler. Secondly, what sort of window is it? Can you install a (small) window air conditioner in it? If the window is too small, you may look into portable air conditioners. From ref 1 (McAfee) on that page: "Portable ACs are similar to the window units ... They suck the hot air from the room and send it outside through a flexible tube that looks like the bendy part of a straw, which you stick in a slat that seals up your window." I was able to find portable air conditioners for sale at the websites of several big home improvement stores in the US (Walmart, Home Depot and Lowe's). If the window is an odd shape, you may be able to cut an appropriate shaped plug from Styrofoam type sheet insulation. (Also conveniently available from home improvement stores.) Good luck. -- 128.104.112.147 (talk) 20:59, 29 July 2008 (UTC)[reply]

My window is those plain-vanilla type house window half-sealed with immovable glass, the other has a mosquito screen that cannot be opened. It's about 1.5 meters by 1.5 meters, the halves are vertical panes, and are therefore unsuitable for air conditioners.

Too much dry ice in an unventilated sunny room may actually kill you, or at least give you a very bad headache. 10% CO2 in air will kill you in minutes; for a 25 cubic meter room that is 4-5 kilogram of dry ice evaporated, maybe less if the air doesn't mix well. Don't do this with dry ice, ever. --Dr Dima (talk) 21:34, 29 July 2008 (UTC)[reply]

A portable air conditioner won't help you in a small enclosed space if you have no way to vent the heat ejected from the air conditioner exhaust.

If the air is reasonably dry, and you do have ventilation from the house, I recommend a portable swamp cooler. You fill it with water, and it blows air past an evaporator to cool down the air. We have one and we use it in the summer. ~Amatulić (talk) 21:45, 29 July 2008 (UTC)[reply]

Light doesn't result in a lot of heat. It is the actual heat from the sun that is heating up the room. There are many relatively cheap window coverings that block much of the heat without blocking the light. That is why most office building have that shimmery look on the windows - they all have reflective film on them that reflect heat without much light. As for the AC, if you are shutting your door and the room is relatively air-tight, then it won't benefit from a central AC system. You've basically closed off the vent. The air needs a way to make it to the return duct. In my house, there is a one-inch gap at the bottom of all the doors. It was easy to do and most people don't notice. I've seen vents directly through walls and little U-shaped vents going through the attic. The main goal is to ensure the room is not air-tight. -- kainaw ™ 02:26, 30 July 2008 (UTC)[reply]

You might hose down the outside of the house in the vicinity of the study. This will evaporate and cool the walls before the heat finds it's way into the study. And, if you haven't considered it already, try closing (inasmuch as they can be closed) the vents in the rest of the house so more A/C will make it to you. Finally, I've got two window A/C units and never bothered to put the screws in. They are an important anti-burgler protection on the ground floor, but I would assume a burglar would need to use a ladder to get to your study, which would be rather too obvious for the average burglar to consider. I do, however, cut a chunk of wood to the proper size to keep the window from opening further, thus preventing the A/C unit from falling or being removed. StuRat (talk) 03:45, 30 July 2008 (UTC)[reply]

Eating and/or drinking something cold, while in minimal clothing, with a fan blowing on you, will also greatly reduce the need to cool the room. StuRat (talk) 03:48, 30 July 2008 (UTC)[reply]

Hosing off the house might cool down the walls of your study, but it would take some dilligent hose work to keep your study from heating up that way. I'd suggest saving the water and investing in curtains and a fan per the other posters. If the window you were complaining about can be openned, I'd suggest pointing a fan AT the window --with the door to your study open-- as an experiment. If you're lucky, you may be able to get enough negative pressure (if the fan is sufficiently powerful and aimed properly) to induce an air flow and suck some of the cool air from the rest of the house into your study. Consequently, this will also increase the load on your AC since you'd also be ejecting cool air from the house. --Shaggorama (talk) 08:21, 30 July 2008 (UTC)[reply]

Point the fan at a closed window ? That won't help. Did you mean to point the fan at the open door to the study to create suction in the room ? That might help, but pointing the fan directly at the person is likely to make more of a diff. If they have two fans, then one fan pointed each way might work. StuRat (talk) 13:42, 30 July 2008 (UTC)[reply]

Actually stu, I meant openning one window and pointing the fan at it with the door open. It's a firefighting trick called negative pressure ventilation. If you push air out the window and the fan is set up in such a way as to minimize churning air though the opening, then it creates negative pressure in the room, sucking air in from the doorway and creating a draft towards the window. Presuming the rest of the house is colder, it could bring some cool air into the room, although it will make the A/C work harder because he'd be stealing cool air from the rest of the house and sending some/alot of it outside. The effectiveness of this strategy for the OP's purposes depends on the position of their study in the house and the power of the fan they use, but it's still worth a shot. --Shaggorama (talk) 14:29, 30 July 2008 (UTC)[reply]

In the long term, creating a better microclima in the vicinity will reduce temperatures by several degrees. That's why cities with many trees (e.g. Berlin) have less problems in summer. --Ayacop (talk) 08:49, 30 July 2008 (UTC)[reply]

My previous house had a 10+ degree difference in the upstairs/downstairs temperature. I fixed it and lowered my electric bill by improving the insulation in the attic. I'm sure your folks wouldn't mind if you volunteered to do that for them! It only takes about a day (a very unpleasant day, but still). --Sean 14:37, 30 July 2008 (UTC)[reply]

Thanks for all the input. I appreciate it very much. I think that for now I will go with the fan suggestion, with a twist -- my mom told me yesterday to set a large chunk of ice in front of the fan and let the fan flow air around ice, then air will come out icy-cool like the air conditioning. I will try the portable and swamp coolers when I get the chance. Thanks again for all the help. 76.68.10.189 (talk) 15:49, 30 July 2008 (UTC)[reply]

I'd avoid any method that's going to increase humidity. It may actually be a lower temp, but that high humidity will make it feel hot and muggy. StuRat (talk) 23:37, 30 July 2008 (UTC)[reply]

Not in all cases. Swamp coolers have been around forever because they work. If the OP lives in a dry climate, they work even better. If it's humid, you need to bring in new air and exhaust the old. I can say our portable swamp cooler works reasonably well. ~Amatulić (talk) 00:08, 31 July 2008 (UTC)[reply]

Tallest mountain in Earth's history?

Mount Everest is obviously the highest point above sea level on Earth. I'm curious if there is any geological evidence of a taller mountain having existed at some point in Earth's geological past. What kind of evidence for prehistoric mountains might there be? Rocks showing signs of immense pressure? Reconstructions of collapsed volcanoes? Guess based on continental plate shifts?

Note: I've asked this question on some other forums and heard a lot of Chimborazo, Mauna Kea, and Olympus Mons. Those mountains are cool too, but I'm asking about a point on Earth higher above sea level than Everest.

192.12.16.65 (talk) 20:44, 29 July 2008 (UTC)[reply]

The maximum height of a mountain on any planet with a fluid interior is limited by isostasy, or the buoyancy of lithosphere material overlying denser mantle material. Think of an iceberg floating in seawater. Another limit is due to the finite material strength of rock in the brittle upper crust. On Mars, Olympus Mons rises nearly 25 km (80,000 ft) from the surrounding plain, more than 2.75 times the height of Everest. This sort of mountain is only possible due to the weak gravity and thick lithosphere on Mars; if you put Olympus Mons on Earth, it would collapse under its own weight due to isostatic equilibrium and structural failure. The total relief on small, icy worlds like Titan and Europa is typically less than a kilometer.

Good question. While I don't know the answer, I do have a suggestion about where to look. The largest current mountains are the result of the collision of the Indian Subcontinent Plate and Asia. This suggests that the collision of two full continental plates may produce even higher mountains. The major continental plates have collided many times in the past, as part of the supercontinent cycle. I would suggest that the initial impact points of the plates would likely be the location for the highest mountains.

The other source of large mountains, volcanoes, doesn't seem as likely to have produced the highest mountain, for a couple reasons. First, note that current volcanic mountains are not as high above sea level as those formed by uplift (although some are higher when measured from the sea floor). Second, note that supervolcanoes don't form a massive single cone, but many smaller surface ruptures. Meteor impacts might also form high mountains, but I'd expect that any that would form peaks bigger than Everest or K2 would liquefy the rock so that it would immediately collapse again. StuRat (talk) 03:30, 30 July 2008 (UTC)[reply]

According to Canadian_shield#Geology, the Canadian Shield once had mountains 12 000 m high. However, the article cites a grade 9 geography textbook as its source, and the textbook mentions only that mountains of that height covered the Shield during the Precambrian. I can't find any sources confirming the textbook's claim.

As for the evidence that mountains existed, rock deformation is the best indicator (see orogeny). --Bowlhover (talk) 09:23, 30 July 2008 (UTC)[reply]

Excellent, thank you for the answers. I also found a reference to 40,000-foot peaks from that same textbook, unsurprisingly I suppose, in the mountain article. The supercontinent cycle article also mentions that sea levels drop when the continental plates are pushed together into a supercontinent, so that may be another place to look, even if lowering the sea level seems kind of artificial. 192.12.16.65 (talk) 16:20, 30 July 2008 (UTC)[reply]

Mount Everest isn't the tallest mountain. It's the one with the highest peak. The tallest is Mauna Kea, which is much lower than Everest, to the point of being mostly underwater. Do you want to know if there was a peak higher than Mount Everest, or a mountain taller than Mauna Kea? 67.182.169.172 (talk) 15:56, 30 July 2008 (UTC)[reply]

The questioner made clear that he is interested in highest point above sea level. Nimur (talk) 16:48, 30 July 2008 (UTC)[reply]

Mount everest may be even taller, if you think of most of it as being underground (below sea level)! :-) --Itub (talk) 17:14, 30 July 2008 (UTC)[reply]

So I'm driving in my car

and picking my nose. Is this wise? If I have a car crash will I poke my brians out? —Preceding unsigned comment added by 86.144.124.43 (talk) 21:32, 29 July 2008 (UTC)[reply]

It is neither wise nor unwise. It just is.

The destination of your finger in a crash depends how you crash. ~Amatulić (talk) 21:41, 29 July 2008 (UTC)[reply]

I have a ten-minute comedy routine on this exact subject :) The airbag deploys with a lot of force. What would the hospital ward be like where they put the nose poking cases? There was an urban legend long ago that cellphones would set off the airbags in BMW's - I always wanted to drive around 'til I saw someone in a Bimmer picking their nose, then give them a call. I could go on... :) Franamax (talk) 22:24, 29 July 2008 (UTC)[reply]

Mind you, we are not allowed to give medical advice here! 93.132.155.253 (talk) 22:26, 29 July 2008 (UTC)[reply]

I'm tempted to suggest you fastrack poking your brain by poking your eye. So I'll resist. Julia Rossi (talk) 05:20, 30 July 2008 (UTC)[reply]

If you're picking your own nose, Brian should be fine. Remember, you can pick your nose, and you can pick your friends, but you can't pick your friend's nose. -- Coneslayer (talk) 11:27, 30 July 2008 (UTC)[reply]

Reminds me of another sketch that had the line: You can prick your finger, but don't finger your...

~Amatulić (talk) 00:03, 31 July 2008 (UTC)[reply]

Coroner: "cause of death is brain trauma due to involuntary nasal finger-poke."

Mom: "I told you if you kept putting your finger in your nose it would get stuck that way!"

Oh please shoot me now. I promise I won't post again to this thread :) Franamax (talk) 09:15, 31 July 2008 (UTC)[reply]

Missed or irregular heart beats

Is there any info on what may cause this phenomenon? —Preceding unsigned comment added by 79.76.156.194 (talk) 22:33, 29 July 2008 (UTC)[reply]

Our article on cardiac arrhythmia links to a lot of information and all of the key Wikipedia articles on the topic. TenOfAllTrades(talk) 22:46, 29 July 2008 (UTC)[reply]

...although I rather suspect that when people subjectively report that their heart "missed a beat" that in fact no significant physical or physiological event occurred, bar perhaps a little jolt of adrenaline. -- Finlay McWalter | Talk 22:49, 29 July 2008 (UTC)[reply]

Pathophysiologically, it's usually a result of coronary artery disease or electrolyte imbalance. However, missed beats and small irregularities are not uncommon in a healthy individual. Wisdom89 _{(_T / ^C)} 00:44, 30 July 2008 (UTC)[reply]

July 30

Redefining the metre

Shouldn't the scientific community redefine the metre so that the speed of light in vacuo is exactly 3 x 10^8 ms^-1? If not why not? —Preceding unsigned comment added by 79.76.156.194 (talk) 00:00, 30 July 2008 (UTC)[reply]

No. It would give a small advantage when remembering and calculating with the speed of light, but such calculations are usually done by people who know what they do, and does it matter how accurately other people can remember the speed of light? It would give huge disadvantages in many other situations, for example uncertainty about which definition is used in a given situation. PrimeHunter (talk) 00:06, 30 July 2008 (UTC)[reply]

You'll note that in the history of the metric system, the various units were defined based on natural and seemingly unchangable measures for convenience' sake (using the circumference of the Earth, density of water, etc). That the speed of light is very close to 3x10^8 was really just a fluke. But in all the redefinitions of units thereafter, the focus has been on finding a more consistent measure that is very close to the one that has been used, again, for convenience' sake. Seeking to actually change a unit of measure would not be very convenient, considering everything that would have to be reconfigured and recalculated. Someguy1221 (talk) 00:44, 30 July 2008 (UTC)[reply]

And even more devastating, the smoot would then require redefinition :-( hydnjo talk 02:24, 30 July 2008 (UTC)[reply]

Couldn't we just say it faster? Relativistic contraction would then supply the necessary correction. Thx for the link btw :) Franamax (talk) 02:35, 30 July 2008 (UTC)[reply]

He-he, excellent idea! hydnjo talk 10:45, 30 July 2008 (UTC)[reply]

The speed of light is 299 792 458 meters per second exactly. It's just as good as any other number. Besides, it makes the permeability of free space exactly 4π × 10⁷. Wily D 02:19, 30 July 2008 (UTC)[reply]

It's the definition of the ampere that fixes μ₀, not the metre. Algebraist 12:18, 30 July 2008 (UTC)[reply]

Err, this are not independent quantities. Wily D 13:27, 30 July 2008 (UTC)[reply]

The physical constraint is that μ₀*ε₀*c² = 1. However, even with fixed c, there is a further choice of definition of the Ampere that fixes μ₀ = 4π × 10⁷ (effectively this is a choice of definition for the charge of the electron). There is no physical reason one can't have both c = 300,000,000 m/s and μ₀ = 4π × 10⁷, provided you are willing to play with the definition of charge units and the value of ε₀. However, messing with the definition of units is generally undesirable for the forementioned reason that it confuses people. Dragons flight (talk) 23:41, 30 July 2008 (UTC)[reply]

You might like natural units which often set the speed of light at 1. J kasd 04:50, 30 July 2008 (UTC)[reply]

Instead of making the meter shorter, we should concentrate on making light faster. APL (talk) 12:49, 30 July 2008 (UTC)[reply]

You missed your chance. The speed of light may have been up to sixty times faster in the early universe (see Variable speed of light#The varying speed of light cosmology). I guess it wore out over the last fifteen billion years. :D TenOfAllTrades(talk) 19:38, 30 July 2008 (UTC)[reply]

The proposal you refer to apply to variation during the first fraction of a second of the universe's existence (i.e. the era of cosmic inflation). The speed of light can not have changed more than a few parts per million since the earliest stars were formed. Dragons flight (talk) 23:41, 30 July 2008 (UTC)[reply]

Diamagnetic materials

What is the most easily obtainable diamagnetic material that has a high negative value of permeability? Ive seen pyrolytic carbon and bismuth mentioned, but where can I get these or some thing similar? —Preceding unsigned comment added by 79.76.156.194 (talk) 02:32, 30 July 2008 (UTC)[reply]

Pyrolytic carbon and ebay is likely your best bet. Mac Davis (talk) 05:02, 30 July 2008 (UTC)[reply]

Bismuth is sold as environmentally-friendly lead shot. If you're in the U.S., try going to a gunstore and asking for it. --Bowlhover (talk) 07:10, 30 July 2008 (UTC)[reply]

Hey thanks Bowlhover. Thats just ideal. I think I can get bismuth shot locally. Its 97% bismuth and 3% tin so hopefully it would not lose much of its diamagnetic strength. Im going to have to melt the shot down so I can cast some plates from it. Any ideas on a safe way to do this? —Preceding unsigned comment added by 79.76.156.194 (talk) 16:57, 30 July 2008 (UTC)[reply]

Bismuth has a melting point of 272 degrees Celsius. Lead turns into liquid at 327 degrees Celsius, yet I easily melted it with a propane torch from Walmart. Perhaps you can fill your cast with lead shot, heat the cast in an oven used for baking, and use a torch to melt the bismuth. Make sure, of course, that you keep the torch well away from the heated oven. --Bowlhover (talk) 19:24, 30 July 2008 (UTC)[reply]

This site describes using either a propane torch or a regular kitchen stove. (Don't use eating utensils for your crucible.) Melting bismuth shot isn't particularly difficult. Note that molten metal – lead or bismuth – is extremely dangerous if handled carelessly. TenOfAllTrades(talk) 19:33, 30 July 2008 (UTC)[reply]

Thanks for the warning TOAT. We wouldn't want to get our fingers (or other bodily parts) burned would we? I know it can be very painful 8-) —Preceding unsigned comment added by 79.76.157.54 (talk) 00:21, 31 July 2008 (UTC)[reply]

Grizzly bear

Since the grizzly bear is not always grey, why does it have the name grizzly? —Preceding unsigned comment added by 79.76.156.194 (talk) 02:51, 30 July 2008 (UTC)[reply]

The article suggests the grizzly has a silver tipped pelt and is a subspecies of the Brown bear, so maybe when it's brown, it's not a grizzly. Julia Rossi (talk) 05:26, 30 July 2008 (UTC)[reply]

Contrarily, the article also states: Their coloring ranges widely across geographic areas, from blond to deep brown or red. due to diet variations. ?! Julia Rossi (talk) 05:29, 30 July 2008 (UTC)[reply]

Because the name, like the bear, is badass. --Shaggorama (talk) 08:29, 30 July 2008 (UTC)[reply]

Indeed. The grizzly will make a grisly mess of his gristly victim. --Sean 14:45, 30 July 2008 (UTC)[reply]

Faraday vs. Lenz

Hi, It is the night before the physics exam (the best time to ask emergency questions), and I have a question. I don't know on which problems I should use Lenz's Law, and on which I should use Faraday's Law. Lenz's appears to be exactly the same, but multiplied by negative 1. How do I know which formula to apply? Thank you oh great desk :) Mac Davis (talk) 04:59, 30 July 2008 (UTC)[reply]

Whell now, good Q. Does this help?

Lenz's law (pronounced /ˈlɛntsɨz ˌlɔː/) gives the direction of the induced electromotive force (emf) and current resulting from electromagnetic induction. The law provides a physical interpretation of the choice of sign in Faraday's law of induction, indicating that the induced emf and the change in flux have opposite signs. Heinrich Lenz formulated the law in 1834.

This tells me that Lenz law also gives the direction of the emf. So if the exam Q asks for direction youll have to use Lenz's law. Otherwise yould be ok with Faraday's Law —Preceding unsigned comment added by 79.76.156.194 (talk) 05:13, 30 July 2008 (UTC)[reply]

Fleas on Horses or Cows

Do Horses and Cows get fleas?. If they don't why don't they? 202.92.75.130 (talk) 05:42, 30 July 2008 (UTC)[reply]

You need to further define "get fleas." Human can have fleas on them and get bit if they are in an infested area, but that is rarely referred to as "getting fleas." Small animals often carry an infestation with them - which is what is often meant by "getting fleas." Cows, horses, and other large animals rarely carry an infestation with them. I grew up around a lot of cow farms and fleas were never an issue. However, it is possible, just as it is possible for a human to take fleas from one building to another. Any warm-blooded animal is capable of providing a safe home for fleas. They just prefer certain animals over others. -- kainaw ™ 06:06, 30 July 2008 (UTC)[reply]

I think there are a couple of reasons why horses and cows don't have fleas. First, their skin is too thick for the penetration of a flea's mouthparts to suck blood. Secondly, and probably more important, horses and cows don't have a nest or home area in the same way that dogs and cats do. The home area is important in the life cycle of the flea to allow the eggs to drop into an area where they can hatch to larvae, pupate and then climb aboard the animal to take in blood to start the next generation. Richard Avery (talk) 07:27, 30 July 2008 (UTC)[reply]

I believe they do get ticks, however. I wonder what's different that allows ticks to feed on them but not fleas ? StuRat (talk) 13:36, 30 July 2008 (UTC)[reply]

I know cows get ticks on their ears. Do they often get ticks on the rest of their body? -- kainaw ™ 13:41, 30 July 2008 (UTC)[reply]

Only if they are fully checked out. —Preceding unsigned comment added by 79.76.185.178 (talk) 00:15, 1 August 2008 (UTC)[reply]

Ticks differ from fleas in two respect that may be pertinent to this discussion. They tend to burrow into the skin thus overcoming the problem the flea encounters. (Why a tick is able to do this and a flea not is beyond my primitive grasp of this topic) The spread of ticks is achieved by the adult, after hatching, looking for and ascending a stalk of grass or a plant to put itself in a position where it can grasp a passing animal, cow, deer, dog or indeed human. This strategy gives it a singular advantage over the flea by allowing it to bridge a much larger vertical space and not having to rely on a central point to board the host. Richard Avery (talk) 14:40, 30 July 2008 (UTC)[reply]

Ocean smell

I've lived for 30+ years in the Arctic. For the first time ever we are noticing a strong "smell of the sea". In other years you would almost have to be on the shore to actually smell it. However, this year it can be smelt quite well at my house, about .4 km (1/4 mi), away and I noticed it the other morning about 2 km (1.2 mi) inland. Any ideas why the smell would be stronger this year than other years? CambridgeBayWeather Have a gorilla 09:40, 30 July 2008 (UTC)[reply]

Warmer water leading to higher growth rate of microorganisms? In the article you cite you can read the mechanism stays off until decaying plankton are around. From this it's not far to a testable hypothesis. --Ayacop (talk) 10:10, 30 July 2008 (UTC)[reply]

Thanks. I should have thought of something like that. Especially as it was only yesterday I was looking at videos of some young people in Ulukhaktok, Northwest Territories jumping their bikes off the dock into the ocean. It's the first time I've ever seen anybody go into the ocean without a suit on. As an aside we've noticed some other changes this year. The ponds which were drying up, similar to the one shown here but not as extreme, are completely full. Also the vegetation, which on our side of the island is usually brown, is very green. CambridgeBayWeather Have a gorilla 13:03, 30 July 2008 (UTC)[reply]

PLZ GIVE ME THE FORMULAE

What is the formula for calculating "port pressure drop" for water passing through a port hole at certain "port velocity"? What is the formula for calculating "wall shear stress" in a heat exchanger? Please give me simplified formulae. I will be grateful.

Chandra 30.07.08 —Preceding unsigned comment added by 117.193.161.16 (talk) 10:49, 30 July 2008 (UTC)[reply]

Does the photon exist?

Wikipedia:Reference_desk/Archives/Science/2007_December_3#Proper_interval_locality_theory

Question \ response

According to proper interval locality the propagation of electromagnetism is facilitated by the signature of the space-time metric. Since the metric signature is common to both flat and curved space-time then the theory is valid in space-time as defined by both special and general relativity.

I would suggest a glance is inadequate if you wish to understand proper interval locality, however here are some of the salient points.

. The wave particle duality of matter results from the geometry associated with our inertial reference frames and is an inevitable consequence of the constancy of the speed of light relative to those frames.
. The theory distinguishes between observable events that can be assigned precise and accurate locality relative to our inertial reference grids and quantum events that do not have exact locality relative to our inertial grids. (Where a quantum event is considered to be a point in the history of a quantum object relative to itself).
. The metric associated with our inertial reference grids, precludes the possibility of quantum events being assigned a unique set of coordinates relative to our reference grids, instead quantum events are projected onto our reference as event surfaces.
. The light cones illustrated in the website are quantum event surfaces. In free space the apex of the light cone is the proper interval locality of the quantum event.
. Pairs of quantum objects are likely to interact if the apexes of their light cones are spatially close. (The likelihood of interaction falling off with the inverse of the square of the spatial separation)
. Every point on the primary light cone is projected onto our reference grids as a secondary light cone. This mechanism results in an infinite succession of event surface projections that fill the whole of space-time. (It is this secondary quantum event surface projection that is responsible for the interference effects in experiments such a Young's double slit.)
. In Aspect's experiment the quantum event surface associated with the cascade of the calcium atom intercepts the detectors at the moments the detections occur. The calcium atom relative to itself interacts with both detectors immediately and simultaneously, therefore, the result must be inherently correlated regardless of when the polarizers are set.
. Proper interval locality is a self-consistent theory which is also wholly consistent with both relativity and quantum mechanics (That is the mathematics of quantum mechanics, clearly it deviates metaphysically in that it does not accept that light is required to be mediated by a particle.)

There is no doubt that the theory of proper interval locality explains interference and how Bell's inquality can be violated without compromising the theory of relativity, but this achieved at the expense of losing the photon as a basic component of physical theory.

Itsuggests that the idea of the photon was a naive interpretation of the results of such experiments as the photoelectric effect, the Compton effect and other scattering experiments. Proper interval locality has the advantage that, though electromagnetism is mediated by neither a wave or a particle, the the characteristics of the electromagnetic process predict both interference and the quantitisation of light, whilst admitting the violation of Bell's inequality without violating relativity.User talk:WROBO 30 July 2008

I hope you don't mind, but since we have complete archives of all of our questions I've linked to the original discussion.--VectorPotential Talk 11:30, 30 July 2008 (UTC)[reply]

I've also made a few formatting fixes (when you use traditional indents (spacebar) wikipedia recognizes this as another type of formatting and generates a large box with a dotted outline around your text)--VectorPotential Talk 11:32, 30 July 2008 (UTC)[reply]

Do you have a question? This seems to be a copy and paste from the previous Ref Desk thread. My best guess is that you're the author of this original research and you're trying to advertise it here, which is not what the Ref Desk (or indeed Wikipedia) is for. -- BenRG (talk) 11:57, 30 July 2008 (UTC)[reply]

According to the edit history it seems that WROBO was the one who added the last reply to that archive (in July). Although it does seem to be a sort of essay. Given that no new question is being asked I'm not entirely sure why this here. --VectorPotential Talk 12:04, 30 July 2008 (UTC)[reply]

Answer:

Q: "Does the photon exist?"

A: Yes.

Pure dogma aimed at perpetuating the popular myth.

Why should nature behave with such exuberant extravagance instead of simple elegance? The photon, no doubt, is the greatest mistake of twentieth century physics and will eventually join its predecessor the Aether. —Preceding unsigned comment added by 84.69.94.168 (talk) 08:40, 2 August 2008 (UTC)[reply]

rember?

Does anyone know of any recent publications that mention the exact (or even approximate) chemical composition of the new anti-Alzheimer's drug 'rember'? According to the BBC article Rember = Methylene Blue, according to other AP stories Rember = Methylene Blue + Other stuff. My quandary is that if the first statement is true then it should probably be merged into Methylene Blue, if not then it should probably have its own article. And yes, I am aware that this question is a thinly veiled article improvement drive ;) VectorPotential Talk 13:27, 30 July 2008 (UTC)[reply]

http://www.bestsyndication.com/?q=20080729_rember_active_ingredient_alzheimers_disease.htm Identifies methylene blue as the active chemical, no where else can I find any mention of any other active ingredients, (so the rest is probaly water+flavourings), maybe they add some colouring too (joke).87.102.86.73 (talk) 13:44, 30 July 2008 (UTC)[reply]

I was really hoping for a journal article. I have full journal access but for some reason I just can't turn up a recent publication on the subject. The most recent paper I can find published by Professor Wischik that even mentions methylene blue is "Selective Inhibition of Alzheimer Disease-Like Tau Aggregation by Phenothiazines", and that was published in 1996.--VectorPotential Talk 13:53, 30 July 2008 (UTC)[reply]

Started with journal articles and found this one; it mentions combining methylene blue with "other diaminophenothiazines". (Paired methylene blue with Alzheimer's instead of Rember. This search also turned up two others after the Wischik article you mention; this one from 2007 and this one from 2005). But maybe this is better: the conference report says "Methylthioninium chloride (MTC, or brand name remberTM)" and here's the press release - cheers, WikiJedits (talk) 14:59, 30 July 2008 (UTC)[reply]

The abbreviations "T.C." and "T.C.D." on a plot plan

In a plot plan, what might the abbreviations "T.C." and "T.C.D." stand for? I found a series of labels of the form

T.C. xxx.yy

T.C.D. xxx.yy

along the curb of a street block in a plot plan. In the labels, xxx and yy are three- and two- digit numbers respectively. When interpreted as decimal numbers, those xxx.yy numbers are close to each other, but no two of them are the same, and they are not in numerical order. It is not clear whether they are identifiers or whether they are measurements of some kind. —Preceding unsigned comment added by 71.162.242.76 (talk) 14:09, 30 July 2008 (UTC)[reply]

I don't know, but it is quite common for spot levels to be measured along a curb, so perhaps they are heights above a datum such as sea level (in either metres of feet). Is this plan from an English-speaking country?--Shantavira|^{feed me} 14:32, 30 July 2008 (UTC)[reply]

Yes, the plan is from an English-speaking country. --71.162.242.76 (talk) 14:51, 30 July 2008 (UTC)[reply]

In construction, T.C. commonly means "Target Completion" and T.C.D. means "Target Completion Date". It is also common to represent a date in Julian format - a 3-digit number 0 to 366 followed by a 2 or 4 digit year. Does that format fit with your xxx.yy numbers? -- kainaw ™ 14:38, 30 July 2008 (UTC)[reply]

The xxx.yy numbers don't make sense when interpreted as dates in Julian format. Here's another bit of information: there's a T.C. label and a T.C.D. label in front of each property. The two are quite close together. There are only T.C. labels along the parts of the curb not directly in front of a house, and those labels are farther apart. --71.162.242.76 (talk) 14:51, 30 July 2008 (UTC)[reply]

How about elevations? Top of Curb, Top of Curb at Driveway. Have look at this, page 5, Section G, #7. Franamax (talk) 19:35, 30 July 2008 (UTC)[reply]

Judging from the context, I think you're right. Thanks. --71.162.242.76 (talk) 19:47, 31 July 2008 (UTC)[reply]

The shortest research paper abstract

Years ago I read about a physics paper which had the shortest abstract possible — just one word: "no". (The paper's title poses a question and the abstract answers it in the negative.) I don't remember enough about the title to look it up. Does anyone know what paper I'm talking about?

Update: I found the answer. The paper was:

Hajdukovic, D and Satz, Helmut, "Does the one-dimensional Ising model show intermittency?", 1992 (a pre-print from CERN's theory division).[9]

—Preceding unsigned comment added by 71.162.242.76 (talk) 14:28, 30 July 2008 (UTC)[reply]

A well deserved attaboy for extreme finding. -hydnjo talk 01:52, 1 August 2008 (UTC)[reply]

Unfortunately, when the paper was finally published in a journal, the abstract became much longer: "We give an analytical proof that the general d-dimensional Ising model in an external field does not lead to intermittency." doi:10.1142/S0217732394001350. --Itub (talk) 13:14, 11 August 2008 (UTC)[reply]

The traditional example of "the shortest abstract ever written" is "e=mc²". -- kainaw ™ 14:31, 30 July 2008 (UTC)[reply]

What paper had that abstract? Not Einstein's, which seems to have no abstract at all. -- BenRG (talk) 19:01, 30 July 2008 (UTC)[reply]

Probably just another silly scientific myth. Einstein's paper of course doesn't even have E=mc² in it at all in that particular form. (Scientists love to pretend they care about truth, but clearly their understanding of the term doesn't extend to history.) --98.217.8.46 (talk) 19:56, 30 July 2008 (UTC)[reply]

Nothing like an sweeping generalization to brighten the day, huh? -- Coneslayer (talk) 20:01, 30 July 2008 (UTC)[reply]

I know what you're talking talking about, but I can neither remember nor find it. This is a tough one to google. The paper title was along the lines of "Does the blah blah blah blah?" and the abstract was, as you say, "No." -- Coneslayer (talk) 14:46, 30 July 2008 (UTC)[reply]

It reminds me a bit of this paper, Are crystal structures predictable?, which starts with "No". However, it's not an abstract. --Itub (talk) 17:21, 30 July 2008 (UTC)[reply]

I seem to remember that the question posed is about a certain property, something along the line of "Is symmetry preserved ...?" (I don't actually remember if any of those specific words are in the title. I just have a vague feeling that that's the type of question posed.) --71.162.242.76 (talk) 18:10, 30 July 2008 (UTC)[reply]

I tried searching for this abstract in the database Scopus, but I didn't have any luck. I think Web of Science may have better coverage, but I don't have access. Can someone else try? ike9898 (talk) 20:31, 30 July 2008 (UTC)[reply]

The paper was mentioned in Science along with a number of other curiosities such as most authors on a paper and shortest title ("!"):

Byrne, Gregory (1988-11-25). "Random Samples". Science. 242 (4882): 1130. ISSN 0036-8075. JSTOR 1702629.

Frustratingly though it doesn't give the title. All I can figure out is that it must have been published before 1988, but I'm having no luck finding it. the wub "?!" 22:49, 30 July 2008 (UTC)[reply]

A couple of amusing close contenders I found are "Guaranteed margins for LQG regulators" (abstract: "There are none") [10] and "How good is Morse Code?" (alleged abstract: "Not bad!") [11] the wub "?!" 23:09, 30 July 2008 (UTC)[reply]

Someone on another site asked this question a few months ago: [12]. Some of the more interesting responses included

Title: Guaranteed margins for LQG regulators

Abstract: There are none.

and

Title: On the zeroes of the Riemann zeta function

Abstract: The paper proves the Riemann Hypothesis.

Good hunting, folks. TenOfAllTrades(talk) 23:06, 30 July 2008 (UTC)[reply]

Note that the abstract is presumably incorrect, since the Riemann hypothesis is still an open problem. —Lowellian (reply) 00:50, 2 August 2008 (UTC)[reply]

Kind of related to the subject, but I remember learning in undergraduate physics that the shortest PhD dissertation was probably submitted by Louis DeBroglie. It was 2 pages. His dissertation committee was bothered by that (just two pages? for a PhD?), so they showed the paper to Albert Einstein. Einstein said it's a very good paper, so they awarded deBroglie a PhD. This dissertation eventually led to deBroglie winning a Nobel prize for introducing the theory of electron waves. I imagine with 2 pages of text, the abstract was probably rather short too. I wish I could find references for that story. Wikipedia doesn't mention it. ~Amatulić (talk) 23:59, 30 July 2008 (UTC)[reply]

A little googling suggests that's complete nonsense, I'm afraid! [13] is a site selling his thesis as a 127 page book. --Tango (talk) 01:05, 31 July 2008 (UTC)[reply]

I can't find any verification for that. [14] says his Recherches sur la théorie des quanta was 127 pages long. This corresponds to WorldCat and ScienceDirect, as well as here ("over 100 pages"). Even so, smart guy. --Bennybp (talk) 01:04, 31 July 2008 (UTC)[reply]

This translation of De Broglie's thesis spans 73 pages, and French is less concise than English. --Bowlhover (talk) 01:05, 31 July 2008 (UTC)[reply]

Did they translate the references section? --Carnildo (talk) 20:50, 31 July 2008 (UTC)[reply]

There references (as one can see) only fill up one page (like most Physics theses of that time). --98.217.8.46 (talk) 00:36, 2 August 2008 (UTC)[reply]

Carnildo: I was actually the first user to reply to Amatulic's post, so I was demonstrating that De Broglie's thesis is much longer than 2 pages, not that it's shorter than 127. --Bowlhover (talk) 06:04, 3 August 2008 (UTC)[reply]

Note that length questions aside (which I suppose are spurious), it is true that his committee was very dubious of DeBroglie's thesis (not because of its length, but because of its content) and did show it to Einstein who did not only approve it but suggested it was of immense importance. So there is an aspect of truth to the story, even if parts of it are, well, dubious. --98.217.8.46 (talk) 00:36, 2 August 2008 (UTC)[reply]

Wow. Thanks for the clarification on deBroglie. I guess my physics professor embellished the story regarding the length of the paper, but the other details were correct. Either that, or my own memory has modified the story after 25 years. ~Amatulić (talk) 01:01, 2 August 2008 (UTC)[reply]

Actually, it's likely that neither your professor embellished the story nor you remembered incorrectly. http://www.math.niu.edu/~rusin/known-math/00_incoming/thesis is an example of another person making similar claims about De Broglie's PhD thesis; it seems that the misconception is widespread. --Bowlhover (talk) 06:04, 3 August 2008 (UTC)[reply]

Cat behavior

A stray cat had kittens in my carport and mother moved them across the street when I cleaned the carport up. Occasionally one of the kittens would stay close and follow back over. They found several spots in the yard to sleep. Even though I fed the kitten while it was in the carport it would run like crazy an leave the mother behind who let me hold her all of the time. One morning when I returned from the store, however, to my surprise each cat demonstrated the reverse behavior. The mother slipped away but the kitten stayed behind and did not run away. The impression I had was that they had exchanged personalities as in sort of like who is who. Where can I find information about this type of behavior? 71.100.9.68 (talk) 15:48, 30 July 2008 (UTC)[reply]

This doesn't answer your actual question, I know, but still: I can pretty much guarantee that the cats did not exchange personalities. -- Captain Disdain (talk) 17:09, 30 July 2008 (UTC)[reply]

Maybe what you're looking for is something like imprinting. --98.217.8.46 (talk) 17:32, 30 July 2008 (UTC)[reply]

Perhaps on that day the mother cat simply didn't want to be friendly, while the kitten, after watching you and the mother interact, decided to be bold and investigate. 20I.170.20 (talk) 19:37, 30 July 2008 (UTC)[reply]

Expanding on what 20I.170.20 said, I would think the mother cat was once a house cat, so it initially reacted fondly to you as a human. Then, while you weren't with the mother, another human might have frightened her (e.g. by throwing water on her to get her to go away or yelling at her), which might have put her in a temporary bad mood toward humans. Or she might just be fickle like most cats and tomorrow she'll be fine with you. Since the kittens interacted with you at a very young age, they might have started to trust you and understand you do not want to hurt them but care for them, so they're letting you handle them. I can't base anything I have said on something encyclopedic, just on my own experience with feral cats.--El aprendelenguas (talk) 20:29, 30 July 2008 (UTC)[reply]

Maybe the mother just needed a break and was happy that her kitten finally let someone else take care of it (I am half serious). Maybe the mother needed to go take a call of nature. BTW, you seem to switch between kittens and kitten. If only one kitten was with you, perhaps the mother decided she needed to go look after the other kittens Nil Einne (talk) 14:30, 31 July 2008 (UTC)[reply]

Maximum size of a star

I was reading about VY_Canis_Majoris, and it's said that "the largest possible star is approximately 2,600 times the radius of the Sun." Does anyone know why this is or what happens at that size? Thank you. Louis Waweru Talk 21:42, 30 July 2008 (UTC)[reply]

I was wondering about that too. I'm not sure... The only other objects that are larger are supermassive black holes. OJ 287 is the most massive at 18 billion sollar masses. Maybe if a star becomes too massive, the core pressure forces the density into a black hole perhaps? ScienceApe (talk) 22:30, 30 July 2008 (UTC)[reply]

Stellar evolution#Massive stars has a link to the Eddington limit, saying "Stars cannot be more than about 120 solar masses because the outer layers would be expelled by the extreme radiation." -- 128.104.112.147 (talk) 22:41, 30 July 2008 (UTC)[reply]

Star formation#Low Mass and High Mass Star Formation also has some information - it appears the topic isn't particularly well understood. --Tango (talk) 22:50, 30 July 2008 (UTC)[reply]

(two edit conflicts) I think if a star were so massive, the pressure of gravity would cause it to collapse onto itself. That's what happens to massive but stable stars after they expand beyond a stable point; they collapse and form a black hole.--El aprendelenguas (talk) 22:51, 30 July 2008 (UTC)[reply]

Bah, see Eta Carinae for the most massive known star. Even at the maximum mass, it's often shedding due to its instability. If you're talking about maximum radius, however, see Hayashi limit. More mass in formation means pressure tends to overwhelm gravity, not the other way around. The only way to get a black hole is a large implosion caused by a sudden drop in thermal pressure which occurs when fusion in a stellar core ends. Even in core collapse, though, degeneracy pressure holds the majority of stars as a white dwarf or neutron star. Please read stellar evolution. SamuelRiv (talk) 23:11, 30 July 2008 (UTC)[reply]

Thanks for the information guys. The maximum radius of a star is the Hayashi limit, which varies for a given mass. The maximum mass of a star is the Eddington limit. If a star exceeds that limit, the intense energy from the nuclear fusion will create stellar winds that expel mass until that the star returns to within the Eddington limit. And I guess someone calculated that largest possible radius to be 2600 solar radii. In a broad sense, is that a decent view for the laymen to hold? Louis Waweru Talk 02:20, 31 July 2008 (UTC)[reply]

The Development of Oxygen

What does the eventual development of oxygen mean? Isn't it that most environments were not suitable for anaerobic prokaryotes? Or is it because a large portion of the history of life was devoted to eukaryotic evolution?Crazymaniac15 (talk) 22:37, 30 July 2008 (UTC)Crazymaniac15[reply]

Wasn't this answered already? Someguy1221 (talk) 23:12, 30 July 2008 (UTC)[reply]

Yes, but three contradictory answers were given. According to History of the Earth, "Oxygen was toxic; probably much life on Earth died out as its levels rose." However, according to Oxygen Catastrophe, oxygen provides energy much more efficiently than other sources. This would presumably facilitate evolution of complex organelles like the nucleus, but I could not find a source. I would say that A is the best answer because D is doubtful, and the others are utterly ridiculous. --Bowlhover (talk) 07:14, 31 July 2008 (UTC)[reply]

Rubber band plane.

Looking for stuff to entertain my young son, I saw a rubber band powered plane kit (cardboard) for some ridiculous price in a toy-shop the other day, and I thought I could make that from scratch without too much hassle. However I can't find a decent pattern for such a device anywhere on the net, they all seem to require balsa. I want to make it cheaply as possible, using cardboard (cereal packets, 2+ ply if required), maybe coke cans for the propeller, that kind of thing. Can anyone help with a decent link? Jooler (talk) 23:10, 30 July 2008 (UTC)[reply]

I've made these before for Science Olympiad, and it's really difficult to get going right. My first suggestion is to order online - you can get a great plane for $20 (in 2003, at least). If you don't want to do that, you'll definitely need to order a proper propellor, wing paper, and rubber band online. My "test" plane was the Delta Dart from TurnerToys, which won't get you anywhere but gives you a good 10-second flight with no modifications. The better ones, though, will require you to shave down the propellors with an exacto-knife or sandpaper. SamuelRiv (talk) 23:20, 30 July 2008 (UTC)[reply]

Also see FAI Model Supply. SamuelRiv (talk) 23:24, 30 July 2008 (UTC)[reply]

When I was a kid, balsa rubber-powered planes were available in any convenience store, for usually less than a dollar. These were planes with a stick for a body, and slots for inserting the wings and stabilizer parts. Not really a kit, as they took no skill to assemble. The big brands I remember were Guillows and North Pacific (no article on that, 'cause Guillows bought it out). I never understood the popularity of Guillows planes, as they always had heavy propellers, whereas the North Pacific propellers were thin, light, well-balanced, and had the correct aerodynamic twist.

Guillows, however, made much more elaborate kits (and still does). I just never liked their propeller design. Look in a hobby shop. ~Amatulić (talk) 23:40, 30 July 2008 (UTC)[reply]

$1.79 at Toyworld (kids love 'em and will save you much time). -hydnjo talk 23:53, 30 July 2008 (UTC)[reply]

$1.95 at Megahobby for the Guillows brand. -hydnjo talk 00:13, 31 July 2008 (UTC)[reply]

They're both Guillow's, actually. They both have the fat heavy props. The better North Pacific props can't be found on toy planes anywhere. I liked the Sleek Streek and Skeeter myself. Picture is here.

Look at this, I think it's perfect for your kid: free plans for building a reproduction Sleek Streek. That page also confirms my memory that the Sleek Streek was a better flyer than anything Guillows made. ~Amatulić (talk) 00:57, 31 July 2008 (UTC)[reply]

As I originally stated, I am looking for plans that do not use balsa, just cardboard, and I'm looking for just plans, not commercially available kits. Thanks anyway. Jooler (talk) 07:34, 31 July 2008 (UTC)[reply]

I trawled through a number of Google searches on this and found nothing good, so I haven't posted yet. Pretty much everyone wants some money. You can buy a book to tell you how to do stuff for free. You can buy a kit and try to make some direct copies. Or, if you want to teach your boy something good, you can just wing it (nyuk) and try making the whole thing by yourselves. The major problem with cardboard is that it doesn't have good stiffness (compared to balsa wood, that's why it's used so often). In order to sustain the tension of a wound elastic band, you are likely to need a stiffener of some kind, even if you fold the cardboard. I spent an hour searching this, if it was that easy I expect I would have found a good result. I did find some book reviews with bold promises, perhaps they are at a library close to you. Bottom line - if you want to do it for free, just start trying. We might be able to help with specific advice on wing shape or propeller twist or ways to stiffen individual bits. As far as designs for cardboard planes - sorry, I personally couldn't find any free ones. :) Franamax (talk) 10:51, 31 July 2008 (UTC)[reply]

These types of planes are tough to get off the ground, especially when you're not using ultralight materials, but there's no harm in trying. Here are a few suggestions: To make a propeller from a coke can, cut your figure-8 shape at a slight angle from the vertical axis of the can. Punch a hole in the center and see if you can smooth the edges of the hole, then fit snug around a thin dowel for your axle. Since you're using cardboard, you won't have much of any compression strength, so I suggest rolling a small piece into a tube for the fuselage and then having a paperclip hook fixed at one end to hold the rubber band *inside* the tube. To hook to the propeller axle, I'd say just drive a small, thin nail into the end of the wood dowel and bend into a hook., letting the dowel rest free inside the fuselage. My last tip is that you should make sure the wings are bent into a small arch, and that they make a slight "V" shape when viewed head-on. This will ensure that the plane is stable in flight. SamuelRiv (talk) 14:04, 31 July 2008 (UTC)[reply]

July 31

Touch pads

How can one interface with a capacitance based touch screen without the use of a finger or other body part? Nadando (talk) 00:15, 31 July 2008 (UTC)[reply]

Stylus? unless it has a thermal basis. See Touch screen. Julia Rossi (talk) 00:53, 31 July 2008 (UTC)[reply]

Odor spectrum

As a spectrum analysist, I'm wondering what different foods I should eat to give the broadest range of odors from my gaseous emissions. Any help appreciated! —Preceding unsigned comment added by ProperFraction (talk • contribs) 00:34, 31 July 2008 (UTC)[reply]

As an omnivore you could say it's already happening. Julia Rossi (talk) 00:55, 31 July 2008 (UTC)[reply]

Well from your link, I don't see much about increasing the range of smells emitted from the internals. Could you please be more precise? — Preceding unsigned comment added by ProperFraction (talk • contribs) 01:38, 31 July 2008 (UTC)[reply]

I don't think that more precision would be appropriate from we armchair Gastroenterologists. Please consult a medical professional for a more detailed response. -hydnjo talk 04:48, 31 July 2008 (UTC)[reply]

More elements means more compounds! Increasing sulphur compounds in breath can be done by eating plants from the Alliaceae family, i.e., garlic and onions. When digestion comes into play, sulphur containing food like the above or food with a high percentage of sulphur-containing amino acids would be best, e.g. eggs. --Ayacop (talk) 09:18, 31 July 2008 (UTC)[reply]

Name of measure of time

Is there a measure of time that is some unit from the last planetary alignment? Graham (talk, contrib, SIGN HERE!!!) 03:08, 31 July 2008 (UTC)[reply]

Alignment of which planets? I'm not quite what you're looking for, do you mean a more concise way of saying "X years since the last alignment"? If so, there's nothing that I know of, you'll just have to write it out in full - you can pick your own abbreviation and use it after the first time, though. How about YSA ("Years Since Alignment")? --Tango (talk) 03:12, 31 July 2008 (UTC)[reply]

My understanding is that the planets in our Solar System have never actually aligned. They've gotten relatively close to being in a sort of line-ish sort of position, but never lined up in any real way. So, without a real event, there cannot be any time since the event. -- kainaw ™ 03:30, 31 July 2008 (UTC)[reply]

Do you know when this "sort of" alignment occured? And how exact was it? If it wasn't exact, and no event like this has happened before, I could use the creation of the solar system as my reference point and call it "cycle 0" or something like that. Graham (talk, contrib, SIGN HERE!!!) 04:31, 31 July 2008 (UTC)[reply]

Graham: See Syzygy for some enlightenment, especially the Syzygy#Astronomy section. =Axlq 04:56, 31 July 2008 (UTC)[reply]

[15] is a good explanation of how unlikely it is. --Tango (talk) 21:05, 31 July 2008 (UTC)[reply]

flatulence and skipping menstruation

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

Capillary waves on a lake

Today, while I was out boating, I noticed an interesting phenomenon. There was a large patch of "choppy" water--just small capillary waves with wavelengths being approximately 1-2 inches, caused by wind (i.e. not from boats). Then, just a short distance away, there was a large patch of very smooth water. I was wondering why there would be such defined differences in water turbulence in relatively the same area. I assume that it would be affected by varying air currents over the water and/or the water depth in the different areas, but I would like to know a little more on the subject. Any input would be appreciated. Thanks in advance!!

Dimblethum (talk) 06:54, 31 July 2008 (UTC)[reply]

You may have seen Langmuir circulation, whose wikipedia page is unfortunately a bit short on explaining the mechanics. EverGreg (talk) 11:21, 31 July 2008 (UTC)[reply]

Optical illusion, disappearing image

Can anyone tell me why image 18 in this gallery only appears at a distance? If the monitor matters, I'm looking at it on an LCD. Disappears completely when I get close to it. Someguy1221 (talk) 07:14, 31 July 2008 (UTC)[reply]

Try Figure-ground (perception) - this site has lots more. -hydnjo talk 11:02, 31 July 2008 (UTC)[reply]

I think this one is closer to the same illusion. -- BenRG (talk) 11:29, 31 July 2008 (UTC)[reply]

'tis indeed! I was shy about linking to that site with its Dalí image beneath. ;-( hydnjo talk 23:36, 31 July 2008 (UTC)[reply]

This also seems relevant: http://www.michaelbach.de/ot/fcs_SpatFreqComposites/index.html —Keenan Pepper 03:47, 1 August 2008 (UTC)[reply]

Note that shrinking the image in a photo editor, shaking your head violently, scrolling the page quickly, and dimming the light will all cause the image to become more prominent. This implies that the contrast between the white and dark bars hides the subtle colour differences in the dark bars. When the bars are blurred by distance, most of the image becomes shades of grey or brown and the colour differences can easily be noticed. The fact that dimming the light helps implies the white bars are overwhelmingly bright at close distances and causes all darker bars to seem completely black. --Bowlhover (talk) 07:57, 1 August 2008 (UTC)[reply]

Although interesting enough, that figure doesn't work at all for me. Even if my nose is touching the monitor I can kind of still see the bear (obviously it's difficult to recognise as a bear but there's clearly a shape). Well unless I turn the contrast to an insanely low level Nil Einne (talk) 08:26, 1 August 2008 (UTC)[reply]

The image is quite clear to me at any distance... --M1ss1ontomars2k4 (talk) 03:31, 2 August 2008 (UTC)[reply]

semiconductors

What will happen to the characterstics of any semiconductor if we add an impurity with two or six electrons in valence shell???? 13:19, 31 July 2008 (UTC)swadesh

Looks a bit like homework, so see Doping (semiconductor) to find the answer yourself —Preceding unsigned comment added by 79.76.183.222 (talk) 16:08, 31 July 2008 (UTC)[reply]

Answer is not there..

Typically silicon ( and other group 4 semi conductors are doped with group 3 and 5 elements), doping with group 2 and 6 might be expected to have the same effect, but is not as likely, in the case of oxygen (6), formation of non conduting silica is likely, in the case of magnesium or calcium (2) - salt like compounds may form and 'salt out' to form separate phases. If they do not salt out -then expect properties similar to B doped Si, but more so.

In the case of other group 6 elements S, Se, Te I would expect an increase in conductivity (similar to P doping) but with the larger elements it may not be likely that the element will successfully incorporate itself into the Si matrix.

Was it Silicon you were specifically thinking about, or another semiconductor? - because in some cases metal atoms eg can increase conductivity in semiconductors by electron donation, or even convert non conductors to semiconductors.

You may need to be more specific.87.102.86.73 (talk) 17:00, 31 July 2008 (UTC)[reply]

Bug I.D. of the day

Can anyone make a guess about the species of an insect I found in my house last night (and foolishly released before photographing)? I'm in eastern Massachusetts. Features I remember are:

- generally appeared like something between a stonefly and a moth

- overall ~2 inches long

- Two pairs of transparent wings, which fold parallel to the perching surface when it's not flying (resulting in overall elongated heart-shaped profile.) Back wings shorter than front wings.

- feathery mothlike antenna

- long, narrow dark brown body. Very flexible, such that it almost looked limp hanging below the wings when in flight.

Any guesses, or leads? My wife and I have exhausted all the dichotomous keys and such that we could find.
Thanks, jeffjon (talk) 15:43, 31 July 2008 (UTC)[reply]

First thing to hit me is something like a lacewing. The green ones are the ones I usually see. --Wirbelwindヴィルヴェルヴィント (talk) 18:23, 31 July 2008 (UTC)[reply]

That Chrysopa perla is definitely the closest yet. The trick will be finding one with that particular coloring and antenna type. jeffjon (talk) 18:52, 31 July 2008 (UTC)[reply]

Tree I.D. of the day

Can anyone make a guess about the species of a tree growing near my home (which I'll be photographing later)? I live in Belle Center, Ohio, but the property's owner told me some time ago that it's from her native Colorado. It's somewhat furry, and is (according to her) called an "elkhorn", but Elkhorn doesn't have anything like it, and nothing that I can find on Google (either searching for elkhorn tree or "elkhorn tree") is at all related to it. Nyttend (talk) 17:20, 31 July 2008 (UTC)[reply]

Here are the pictures. Nyttend (talk) 17:38, 31 July 2008 (UTC)[reply]

It's not quite "elkhorn," but could it be a Staghorn Sumac? Laenir (talk) 20:07, 31 July 2008 (UTC)[reply]

The leaves are the wrong shape for your basic wild staghorn sumac. This may be the cultivar Rhus typhina "Laciniata", the cutleaf staghorn sumac. Deor (talk) 22:33, 31 July 2008 (UTC)[reply]

Logical calculation

  TWO
+ TWO
_________
  FOUR
_________

In the equation above if W=2,Find T,F,O,U,R.such that no one of them will be same. —Preceding unsigned comment added by 195.225.63.218 (talk) 19:40, 31 July 2008 (UTC)[reply]

Assuming you mean 'no two are the same', there's a unique solution. The easiest way to find it is probably to consider the possible values of O. Algebraist 19:47, 31 July 2008 (UTC)[reply]

That assumes, of course, that T,F,O,U,R are whole numbers less than ten. Maybe that's why the OP is confused? --Bowlhover (talk) 21:05, 31 July 2008 (UTC)[reply]

And please find the solution yourself.--El aprendelenguas (talk) 19:51, 31 July 2008 (UTC)[reply]

Got it! Assuming that each alpha was assigned to only one digit, the solution is unique. Proof in the margin. -hydnjo talk 21:23, 31 July 2008 (UTC)[reply]

Well done. Algebraist 21:26, 31 July 2008 (UTC)[reply]

Easy peasy! And, why isn't this at /math? -hydnjo talk 23:18, 31 July 2008 (UTC)[reply]

And why are we whispering? --Shaggorama (talk) 06:15, 1 August 2008 (UTC)[reply]

unidentified bird

Hi. A few weeks ago, I saw a bird perched on a coniferous tree branch. I live in S. Ontario, and the reason I'm asking is because I tried to find it in whatbird.com (blacklisted), without success. It had a reddish head, yellow belly, and probably a green underside in a shade similar to the tree spines (between light and dark green, more light than dark). It was small, and it looked almost tropical. I think it might be outside of its normal range or something, because I don't recall having seen it before and I can't identify it using that website even if I allow for as many possibilities as possible. Any idea what it might be? Thanks. ~A H 1^(TCU) 20:05, 31 July 2008 (UTC)[reply]

I have no answer but I will note, I read ON Nature regularly and rather than the bird being outside its range, there's an equal possibility that your province is moving underneath the bird. As in, ranges are shifting northward, you might need a different bird guide in future. If I recall, several species are now making appearances. Franamax (talk) 22:37, 31 July 2008 (UTC)[reply]

Is it a Ruby-crowned Kinglet, better images here[16]? Julia Rossi (talk) 01:27, 1 August 2008 (UTC)[reply]

Franamx it looks like you just shifted westwards. ; ) Julia Rossi (talk) 05:34, 1 August 2008 (UTC)[reply]

Hi. Parts of it look similar to the Ruby-crowned Kinglet, but there are differences. My memory of this isn't very clear, but I was viewing the bird from underneath, and I could still clearly see the reddish head area, which was probably solid and extended town maybe to its eyes. My vision of faraway objects isn't perfect, but someone beside me also noted a greenish tail area. The belly area was sufficiently more yellow than the tail area. I don't remember seeing any markings or stripes. Could it be a tropical bird by any chance, maybe an escaped pet or a vagrant? Thanks. ~A H 1^(TCU) 16:15, 1 August 2008 (UTC)[reply]

Sounds kind of like a Western Tanager, but Ontario is a bit out of their range. Take a look at the other tanagers, they are among the few birds in N. America that have really vibrant coloring. 161.222.160.8 (talk) 19:04, 1 August 2008 (UTC)[reply]

mega-tsunami dynamics

Hi. Can a megatsunami possibly be high enough (say caused by an asteroid or catastropic land/ice-slide or super-eruption) to reach into the stratosphere? This is not homework. If so, what would happen? Would it sweep away the clouds/air ahead of it, form some kind of fog, or would its tops freeze? If it freezes, what happens to the ice, or would it not be possible for a moving wave to freeze? What happens if an air blast hits the wave? From the same direction, and what about from the opposite direction or side? Can any tsunami possibly be powerful enough to push the ocean ahead of it and grow taller, or does that violate a law? If such a tall tsunami were "tripped" by some mountains, would its bottom slow down but its top keeps going? Is there any geological (or historic) evidence for such a tsunami? Thanks. ~A H 1^(TCU) 20:16, 31 July 2008 (UTC)[reply]

Megatsunami should answer some of your questions. It says that they could possible by thousands of metres high, and the stratosphere starts at about 10,000m above sea level, so I guess it's just about possible that a really large one could reach the stratosphere. While it is very cold as those altitudes, I wouldn't expect the water to freeze - the wave is going so quickly that no individual bit of water is at that height for more than a fraction of a second. Clouds start all the way at the ground - that's what fog is - so it's certainly possible for a tsunami to reach cloud heights. I guess it would sweep the clouds away... it might sweep them forwards or upwards or destroy them completely, I don't know... I'm not sure what you mean by pushing the ocean ahead, the tsunami is a wave in the ocean, so in a sense that's what it's always doing. It only gets really tall, however, once it hits land, in the deep ocean it's just a couple of metres tall, although it's moving much faster. I'm not sure what happens when a tsunami hits a sudden bit of high ground but not higher than the wave itself, but presumably a megatsunami going over a mountain would work the same as a regular tsunami going over a hill, so someone probably has the answer. --Tango (talk) 20:56, 31 July 2008 (UTC)[reply]

Hi. Thank you for your reply. What I meant by pushing the ocean ahead was, is it possible for the wave to sweep away the ocean ahead of it and leave a lower sea behind it, so that it pushes the ocean into the wave itself, making it higher while being in the open sea, similar to what happens if you cup your hand slightly and sweep it along the surface of a pool? Or, does that violate some kind of physical law, or is a tsunami just not powerful enough because of low friction or something? Thanks. ~A H 1^(TCU) 21:44, 31 July 2008 (UTC)[reply]

After reading through Megatsunami, I have some serious questions. The stated heights are at the shoreline, not the open sea, so I'd question whether a solid ocean wave could reach the stratosphere. Droplets, definitely maybe, given sufficient impact, but a solid wave? If a piece of the ocean is accelerated to the extent it can reach the stratosphere, wouldn't it exceed the speed of sound and break up in the shock wave? Additionally, the article cites shoreline damage to specific heights, fair enough - but I can move back and forth in the bathtub, the waves don't get higher than the edge, but the water definitely sloshes over at the end of the tub. My understanding of the tsunami generated by the 2004 Sumatra seismic event is that rather than the height of the wave at shore, it was the momentum of the water that carried it far inland and to higher elevations than the impacting wave itself. I'll be glad to get corrected on any of this. I don't think much of megatsunami right now though. Franamax (talk) 22:59, 31 July 2008 (UTC)[reply]

Hi. I don't know how to calculate a megatsunami's height, maybe something involving the amount of water displaced verses the ocean depth, etc, but the amount of water displaced by the Chicxulub impact was likely somewhere arount 2500 km³ (600 mi³). Assuming an ocean depth of about 100 metres, and the diametre of water displaced about 170 km, how high would the resulting initial tsunami be? Also, by the time it reaches the shore, it would already be squeezed by the mesozoic Niobrara sea, meaning it would have reached around the South Dakota area before hitting shoreline. The trajectory of the asteroid/comet impact was also likely more towards the north than the south. If the end of the sea was about 3000 km from the impact, and the sea was about 1000 km wide and 50 m deep, would the wave increase or decrease in height at that time? Would it sweep all the way into the Mezosoic Arctic ocean? Thanks. ~A H 1^(TCU) 16:26, 1 August 2008 (UTC)[reply]

In order to travel effectively over great distances, a wave's amplitude must be much lower than the depth of water it is traveling in. Otherwise, the drag of the bottom causes the wave to break and dissipate energy interally. I don't know what the physical maximum is for a tsunami that will comfortably travel across an ocean basin, but I'm fairly confident that it is more likely to be tens of meters rather than thousands. Dragons flight (talk) 19:35, 1 August 2008 (UTC)[reply]

Some interesting information: when an asteroid hits the ocean floor and vaporizes, the cavity created is quickly filled by water, creating a water jet in the centre whose collapse causes the main tsunami. Even a 1 km asteroid can generate a jet 20 km high and a 1000-m tsunami (http://library.lanl.gov/tsunami/212/gisler.pdf, pg. 4). According to the graph on p. 5 of this paper, tsunamis produced by large asteroids can reach a deep water height of 10 km 1000 km from the epicenter, although the authors may be extrapolating too much for the data to be accurate.

The asteroid that hit Earth 3.47 billion years ago flooded all land except the mountains; the tsunami must have been at least several kilometers high for this to happen (http://news.nationalgeographic.com/news/2002/08/0823_020823_asteroid.html). --Bowlhover (talk) 20:45, 1 August 2008 (UTC)[reply]

Your first citation predicts a height of 10s of meters at 1000 km. Your second says they ignore wave dispersion, which means their predictions only really make sense for wave heights significantly shallower than the depth of the ocean it is travelling in (or at sites very close to the point of impact). As I said above, you can't propogate a wave substantial distances unless its height is substantially smaller than the thickness of the ocean basin, otherwise it will break up on itself. The transient "splash" from an impact might be enormous locally, but physics limits the effect it can have at great distances. Dragons flight (talk) 22:25, 1 August 2008 (UTC)[reply]

Quad-core processors

how do quad core processors work? —Preceding unsigned comment added by 24.140.68.142 (talk) 20:38, 31 July 2008 (UTC)[reply]

I've moved this question to the computing reference desk where you may get more responses. You can check progress here. Franamax (talk) 23:06, 31 July 2008 (UTC)[reply]

August 1

Raindrop

What is the weight of a typical free falling raindrop? —Preceding unsigned comment added by 79.76.185.178 (talk) 00:57, 1 August 2008 (UTC)[reply]

According to rain, typical raindrops are approximately spherical, with a diameter of 1-2mm. Thus they have a volume of about 5×10⁻¹⁰–4×10⁻⁹m³, a mass of about 5×10⁻⁷–4×10⁻⁶kg, and a weight of about 5×10⁻⁶–4×10⁻⁵N. Algebraist 01:08, 1 August 2008 (UTC)[reply]

Or in more readable units (no offense Algebraist), a raindrop has a mass of about a milligram (and therefore a weight of about 10 micronewtons). —Keenan Pepper 03:35, 1 August 2008 (UTC)[reply]

Wait does a free falling raindrop have any weight? I mean it has mass..but does it have weight? As the raindrop basically no longer exists when it goes * splat * does a raindrop ever have any weight to begin with? —Preceding unsigned comment added by PvT (talk • contribs) 08:27, 1 August 2008 (UTC)[reply]

Weight is the amount of gravitational force pulling on an object. A raindrop may be ~~in freefall~~ falling, but that's because gravity is acting on it. --Bowlhover (talk) 08:38, 1 August 2008 (UTC)[reply]

Everything with mass in a gravitational field has weight. --98.217.8.46 (talk) 13:51, 1 August 2008 (UTC)[reply]

Bowlhover, raindrops aren't in freefall. Their terminal velocity is 9 m/s at the highest. After a few seconds, they pretty much stop accelerating at all. — DanielLC 17:09, 1 August 2008 (UTC)[reply]

Oops, I used "freefall" to mean "in a fall". --Bowlhover (talk) 18:28, 1 August 2008 (UTC)[reply]

Insect identification

What is this insect? It was in Vancouver. Sancho 07:24, 1 August 2008 (UTC)[reply]

Oh, I think it's a Firebrat. Sancho 07:36, 1 August 2008 (UTC)[reply]

Copper Sulfate as an algacide

I have some copper sulfate I purchased from Southern States Coop and I used it in my pool as an algacide. I was amazed at the quickness which it cleared the pool(overnight) with only about 2 teaspoons of CuSo4. I still have not added any shock in over two months. My pool has 14500gals of water. I have a terrible problem now with algae taking over my small (test)aquarium.I have one fish (left)an he's a Jack Dempsey, who gradually killed the other fish.1) Can I dose the aquarium with him in it? 2)If I must keep him out, for how long? 3) should I just leave him in and OVERdose it for his murder of the other fish? (just kidding) (e-mail removed as per guidelines)—Preceding unsigned comment added by 72.84.241.243 (talk) 12:17, 1 August 2008 (UTC)[reply]

You can use it - though it is pH sensitive - there are many guidlines on the web eg http://www.fishyfarmacy.com/Q&A/all_about_copper.html or search 'copper sulphate aquarium', it's also poisonous to snails. http://www.sydneycichlid.com/algae.htm says 0.3ppm 87.102.86.73 (talk) 12:41, 1 August 2008 (UTC)[reply]

Loop Quantum Gravity

Why does loop quantum gravity predict that the speed of light depends on its energy? Do all LQG theories make this prediction? Thanks, *Max* (talk) 15:44, 1 August 2008 (UTC).[reply]

I'm no expert, but the article section "LQG and string nets" mention that some researchers try to derive photons as analoges to phonons. Phonons are vibrations in a medium that propagate at the Speed of sound, which can in fact depend on frequency in certain media. (And high frequency means high energy). So by the analogue, the speed of photons could depend on their energy too. If I read the article correctly, this is an effect of their model and for instance the "preon approach" would presumably not predict it, so not all LQG theories predict this. EverGreg (talk) 22:02, 1 August 2008 (UTC)[reply]

Robert I of Parma's children

Does someone know what was the mental illness of Duke Robert I of Parma's children by his first marriage with princess Maria Pia of the Two Sicilies? His children by his second marriage are all healthy. Maybe the problem is of the Princess Maria Pia? Help me because it's important..... --84.222.154.178 (talk) 17:24, 1 August 2008 (UTC)[reply]

The article says mental retardation - that's an intellectual disability. (also read this for a list of possible causes)87.102.86.73 (talk) 17:53, 1 August 2008 (UTC)[reply]

It's worth nothing we have no way of knowing if these claims are accurate at least from the information I've seen in the articles. It could be for example that the youngest son or someone else conspired to have them declared mentally retarded for his, her or their own interest. Given that this occured in 1907, I would say it's possible. Also Infanta Maria Antonia of Portugal says two of her children have "issues" (no idea what that means although most of Maria Pia's children has "issues" as well) and one of them was deaf Nil Einne (talk) 18:14, 1 August 2008 (UTC)[reply]

Had 'issues' usually means had offspring - not health issues.87.102.86.73 (talk) 18:19, 1 August 2008 (UTC)[reply]

See Issue and Issue (legal)87.102.86.73 (talk) 18:21, 1 August 2008 (UTC)[reply]

(edit conflict) The problem could be with the union and not specifically with the woman.

This condition can be, but is not necessarily, inherited (have a genetic cause) see http://specialed.freeyellow.com/YAdaptUse.html

There is also the possibilty of bad luck.

I'll leave as message at the humanities desk to see if anyone knows more about this specifically.87.102.86.73 (talk) 18:19, 1 August 2008 (UTC)[reply]

I'm not certain that there was a modern diagnosis-I haven't seen one in reading about it; one could speculate that there was an Rh blood factor incompatibility in the first marriage (and not in the second), or a congenital toxoplasmosis infection (such as that responsible for mental retardation in the French royal pretenders), or any of a number of other possibilities. - Nunh-huh 01:24, 2 August 2008 (UTC)[reply]

Gull strength

For its size, is a gull (say, your basic Herring Gull) physically stronger than a human? --Kurt Shaped Box (talk) 19:49, 1 August 2008 (UTC)[reply]

Well I can't fly - so at a guess - yes?87.102.86.73 (talk) 20:04, 1 August 2008 (UTC)[reply]

I expect that if Kurt were shrunk to the size of a gull, he could kick its ass, (but couldn't fly) and if the gull were enlarged to Kurt's size it would be unable to support its own weight and would fall over (and also be unable to fly). See Square-cube law and "On Being the Right Size " by Haldane Edison (talk) 20:18, 1 August 2008 (UTC)[reply]

I hope not - if Kurt were gull-sized I'd imagine that he would find its claws to be as big as kitchen knives...87.102.86.73 (talk) 21:43, 1 August 2008 (UTC)[reply]

I don't know for certain, but I suspect from observation that gulls have faster reflexes and reaction times than humans too. I don't know how effective punches and kicks would be against thick feathers either... --Kurt Shaped Box (talk) 22:09, 1 August 2008 (UTC)[reply]

Plus gulls have beaks. —Lowellian (reply) 23:51, 1 August 2008 (UTC)[reply]

Could this be adequately modeled by a fight between gull and equally sized primate, such as a small monkey? A Tamarin is approximately the same mass as a gull (at about 1 kg), and they look pretty human-like to me. Nimur (talk) 00:02, 2 August 2008 (UTC)[reply]

Due to the shorter nerve paths, Kurt's reflexes and responses to stimuli would become faster. As for the beaks, his musculature is designed to operate an organism many times larger. Read the Haldane ref and consider how things like strength and mass vary by squares and cubes as size is scaled by an order of magnitude. A human, scaled down, would be far stronger than a small primate or a bird. I personaly would pay big bucks to watch the fight on pay per view TV. Edison (talk) 04:19, 2 August 2008 (UTC)[reply]

Kurt-shaped or not, a box can't beat a gull in a fight. Not even boxing. — DanielLC 17:26, 2 August 2008 (UTC)[reply]

Am I the only one who gets unsettled?

Question restored per Wikipedia talk:Reference desk#Am I the only one who gets unsettled?

When discovering that one's pet parrot not only has sexual thoughts, but has sexual thoughts about humans, namely me? Just to look at a parrot, you wouldn't think it. I'm quite religious and this disturbs me a little. --81.79.21.14 (talk) 19:24, 30 July 2008 (UTC)[reply]

If you're asking do parrots exhibit sexual feelings towards their owners, I'd imagine the answer would be yes, in some circumstances, as parrots often form close, affectionate bonds with their owners. There are several interesting answers from this yahoo! answers post on a similar question, and this article also makes for an interesting read. 20I.170.20 (talk) 19:56, 1 August 2008 (UTC)[reply]

It seems a bit of a leap assume that thought in parrots is equivalent to thought in humans. I have no idea if they do think, but whatever thinking they do is probably pretty parrot-y. Even if the bird is becoming sexually excited, psittacine morality is likely quite different from your own. This is not to say "you're wrong," only to suggest that you may be applying standards to the parrot that apply mainly to humans.

Do parrots looking at their reflection in a mirror act as though they're seeing themselves, or another parrot? I'm thinking of the elephant self-awareness discussed here (an elephant touched a painted mark on her forehead that she could only see in a mirror; she did not touch a similar mark made with "colorless paint"). Lack of such awareness would suggest the parrot isn't all that responsible for its actions. OtherDave (talk) 20:17, 1 August 2008 (UTC)[reply]

I'll tell you what unsettles me. "If the insects had hit on a plan for driving air through their tissues instead of letting it soak in, they might well have become as large as lobsters,..." from the essay linked earlier about animal sizes. Insects the size of lobsters? Gahh. That's really unsettling. Imagine walking through the forest and seeing a mosquito the size of a small raccoon... Nimur (talk) 23:52, 1 August 2008 (UTC)[reply]

Heh, insects were that big during the Carboniferous period, due to higher oxygen levels. ;) —Lowellian (reply) 00:42, 2 August 2008 (UTC)[reply]

Imagine if a mosquito the size of a small raccoon decided that it would like to feed on your blood! Man! It would be the similarly scaled-up centipedes that I'd have a real problem with - I think I've mentioned before that I have a phobia of those particular creatures. I'd have to carry a machete with me everywhere (handguns are illegal here) - just in case I came face-to-face with a skittering 4-foot length of legs, armour-plating and malevolence... --Kurt Shaped Box (talk) 11:26, 2 August 2008 (UTC)[reply]

Male budgies will certainly attempt to copulate with their human's hands or head (if their human is their closest flockmate). It's not something I encourage. I know that some owners find it amusing - but to me, it's a bit like bestiality-lite. I certainly don't know many dog-owners who would willingly allow their pet to hump their leg to the point of climax... --Kurt Shaped Box (talk) 11:33, 2 August 2008 (UTC)[reply]

Astronomy - Solar Eclipse

I was reading an article on the solar eclipse presently underway, and it discussed the rarity of solar eclipses in the universe. It explained that the only reason that we have a precise solar eclipse is that the "...moon is 100 moon diameters away from Earth and the sun is 100 sun diameters from Earth and that that is how it works."

The Solar Eclipse article adds weight to this statement of rarity by discussing how, because of tidal acceleration (the moon's orbit slowly increasing) and that the sun will slowly increase in size over this timescale (presumably because the spent nuclear fuel reduces it's mass and therefore gravitational pull?) full eclipses will no longer occur on earth in slightly less than 600 million years, then never again.

So I wonder if anyone has any comments on the likelihood of this rare little spot in time and space that we happen to be in. How did the moon form at its' present size? Has any statistical work been done on estimating the chance that a randomly selected planet-moon pair in the universe would have these properties? (I know how imprecise planet estimates are.)

I just found this all very interesting. 24.68.246.113 (talk) 20:15, 1 August 2008 (UTC)[reply]

To the best of my knowledge, the approximately "same" (~ 30 arc-minutes) angular diameter of Earth's moon and the sun we orbit is nothing more than "dumb luck", but you can probably expand a variety of Drake equation style estimates to determine likelihood. As far as I am concerned, the likelihood is empirically measured as, "100% of known inhabited planets exhibit this coincidental phenomenon." Alternatively, consider the anthropic approach, "100% of intelligent life evolved visual acuity that could not perceive or distinguish the apparent difference of angular diameter between the two largest astronomical objects visible in the sky of the planet on which it developed." Nimur (talk) 00:07, 2 August 2008 (UTC)[reply]

The chances that a solar eclipse would occur on other planets with moons is quite high. The unusual part is that our Moon and Sun have almost the same apparent diameter, which makes for a very interesting solar eclipse where the body of the Sun is blocked, but the corona is still visible. StuRat (talk) 03:52, 2 August 2008 (UTC)[reply]

Sunburn

What causes the outermost layer of the skin to peel off after sunburn? JIP | Talk 21:28, 1 August 2008 (UTC)[reply]

Apoptosis: programmed cell death. In essence, the body decides that the top layer(s) of skin cells (keratinocytes) are irreversibly damaged by solar radiation and those cells are killed. Some time later, they slough off. TenOfAllTrades(talk) 21:47, 1 August 2008 (UTC)[reply]

A non-sourced photo caption in sunburn says, "the dehydration of the epidermis causes the top layer to flake off." I am going to guess that the cells, which have presumably died all around the same time as TenOfAllTrades described above, shrink, lose their flexibility, and detach from the lower layers as they dry. The combination causes them to flake off in big sheets rather than in small pieces like normal. 71.77.4.75 (talk) 22:11, 1 August 2008 (UTC)[reply]

creation of the universe

why is this universe created? —Preceding unsigned comment added by Pramod tiwari (talk • contribs) 21:28, 1 August 2008 (UTC)[reply]

Wouldn't this be better listed on the Humanities desk? Nyttend (talk) 21:33, 1 August 2008 (UTC)[reply]

Possibly.87.102.86.73 (talk) 22:09, 1 August 2008 (UTC)[reply]

I asked God to come by here and give an answer. If he's not too busy playing mmorgs, perhaps we'll get an answer soon. -- kainaw ™ 22:03, 1 August 2008 (UTC)[reply]

(I'm not too busy)87.102.86.73 (talk) 22:09, 1 August 2008 (UTC)[reply]

There are many responses to this question but none I've heard that could be described as an final and only answer.

One response is basically summed up by the response "It must".

Alternatively you may consider that the universe is never created, if you meant 'why is it created' as being different from 'why does it exist'.

Finally I can suggest that the answer (if it exists) may be beyond human comprehension.

There are other responses, no doubt, that I hope others will be able to link to for you to read - we have numerous articles relating to this - both scientific, spiritual and religious.

I hope that some one does know - for this I leave the space below blank:87.102.86.73 (talk) 22:09, 1 August 2008 (UTC)[reply]

There are several possible answers in our article on creation myths. You may also find a number of useful links in our article on cosmogeny. TenOfAllTrades(talk) 22:14, 1 August 2008 (UTC)[reply]

You need to make the question more specific. Then again for every interpretation of your question I can think of except why god created the universe (in which case there is no generally accepted answer, and AFAIK few religions give an answer at all), the question is pretty much meaningless and there is no reason. If there where laws of metaphysics that explained the laws of physics, then you could just count them as the laws of physics and you'd be back to square one. If you were going to use infinite recursion and have meta-meta-physics, meta-meta-meta-physics, ... for ever, it just wouldn't be logically sound. — DanielLC 17:16, 2 August 2008 (UTC)[reply]

Large Hadron Collider

Some have suggested that the Large Hadron Collider could create small black holes. If this does happen, what could this cause? 67.150.168.139 (talk) 23:20, 1 August 2008 (UTC)[reply]

Micro black hole talks about this issue. "According to the standard calculations these (micro black holes) are harmless because they would quickly decay by Hawking radiation." Someone else with more understanding in this area will have to explain what sorts of particles/products a decaying micro-black-hole would produce... 71.77.4.75 (talk) 23:31, 1 August 2008 (UTC)[reply]

The rule for quantum mechanical decays is "everything not forbidden is compulsory", i.e. any decay that doesn't violate any conservation law has a nonzero probability of happening. A free muon can decay into an electron plus neutrinos because all the conserved properties add up correctly, but a free electron can't decay into a muon plus neutrinos because that would violate the conservation of mass-energy, and it can't decay into particles lighter than itself because, for one thing, all the lighter particles have no electric charge. That's why the electron is stable and the muon isn't. A micro black hole, because of its large mass, would have the whole Standard Model particle zoo to choose from, and presumably would decay pretty quickly into some assortment of everyday particles, there being no conservation law to prevent it. If small black holes dramatically violate the approximate conservation laws, as large black holes are believed to, they might be easy to spot. Otherwise, they would behave much like any other quantum particle with the same mass, electric charge, etc, and I'm not sure how you would even tell that they were black holes. My secret hope is that particles and black holes are actually the same thing, and Standard Model decays are the same thing as evaporation by Hawking radiation. This isn't a completely kooky idea; it has been investigated by real physicists. It runs into serious theoretical difficulties, like the fact that the electron violates

a^{2}+Q^{2}\leq M^{2}

by many orders of magnitude, but I still hope it's somehow true. At any rate, thinking of the electrons and nucleons that make up your body as tiny stable black holes might help some people get over their fear of a tiny stable black hole destroying the Earth/Universe. -- BenRG (talk) 01:35, 2 August 2008 (UTC)[reply]

August 2

Body part focus of cell phone health studies

Most studies I have heard about on cell phones and health focus on brain diseases. But most people I know carry their cell phone in a trousers pocket or a purse or have it hanging on the belt most of the day; people don't put their cell phone next to their head unless they're talking on it, and most people spend more time during the day carrying a cell phone then actually talking on it. So shouldn't the torso, waist, and pelvis be more affected than the head by the radiation? If so, why are the studies focusing on the head and brain; isn't their focus misplaced? —Lowellian (reply) 00:00, 2 August 2008 (UTC)[reply]

Cell phones are usually not transmitting, especially not when they are in your pocket and "inactive" - the device may be on, but the transmit radio is almost entirely off. (They may periodically send a short pulse to the local cell tower to retain link connection). However, during conversation, the mobile device is actively transmitting (at "maximum power"). This necessarily increases the exposure to electromagnetic radiation while a telephone call is active. The assumption is that the cell phone is held near the head (ear) during conversation, thus, during peak radiation levels, so this is the time period of interest to many scientists. Nimur (talk) 00:13, 2 August 2008 (UTC)[reply]

Addendum: As we get more "internet"-ish cell phones, which use persistent data connections, the connectivity model I just described may become less accurate as a descriptor of the cell phone transmitter/radio usage; however, the historical technology trend has been a move towards lower-power radio signals with more sophisticated digital modulation to preserve signal integrity. This will almost certainly be true of any persistent data connections; if for no other reason, it's usually better for battery life, since even complex digital circuits use less power than a nasty high-power narrow-band transmitter. Nimur (talk) 00:22, 2 August 2008 (UTC)[reply]

Considering how many people keep their cell phones in their pockets or otherwise attached to the waistband of their pants/shorts while talking using hands-free sets though, studies on other parts of the body besides the head would still seem useful. —Lowellian (reply) 00:33, 2 August 2008 (UTC)[reply]

Also, you wrote "This necessarily increases the exposure to electromagnetic radiation while a telephone call is active." Another question: how much of an increase? Two-to-one? Ten-to-one? A hundred-to-one? (boldfaced because this question seems overlooked by being in the very middle of a long discussion rather than at the end; I will deboldface this question once it is answered) —Lowellian (reply) 00:38, 2 August 2008 (UTC)[reply]

Keep in mind, that while EM radiation is indeed "radiation", it is not ionizing radiation. It is not the same kind of "radiation" that one means when talking about nuclear weapons or reactors or things like that. Whether there are long-term health effects that can be traced to it or not (I suspect not, other than distraction-related injuries), one should be aware that the terminology can get slippery if one is not careful. --98.217.8.46 (talk) 00:23, 2 August 2008 (UTC)[reply]

Ionizing radiation and radiation may help clarify. Of course, though ionizing radiation is generally considered worse, it is not valid to use this classification as the sole distinction between dangerous and not-dangerous. Nimur (talk) 00:25, 2 August 2008 (UTC)[reply]

I wasn't implying that it was. But "radiation" in the common parlance is something very different than the "radiation" in cell phones, or light bulbs, for that matter. It's entirely true that light bulbs output LOTS OF RADIATION!!! but that doesn't really mean "radiation" in the sense that most people know it. When most people think of "radiation", they mean ionizing radiation—they are thinking about genetic damage, cell damage, etc., not the sorts of things one gets at the microwave level, e.g. heating. --98.217.8.46 (talk) 00:27, 2 August 2008 (UTC)[reply]

Research has been done in mammals and through observational methods in humans, see this and all of it's linked papers and this study on mammals. Nanonic (talk) 00:25, 2 August 2008 (UTC)[reply]

Also, how much radiation are wireless cards generating in comparison to cellphones? —Lowellian (reply) 00:34, 2 August 2008 (UTC)[reply]

Cellphone: 2 W

WiFi card: 0.1 W

These are the regulatory limits [17], but the devices don't operate flat-out all the time. --Heron (talk) 14:11, 2 August 2008 (UTC)[reply]

A Cell phone transmits at "maximum power" only when the cell signal is weak. The cell tower interacts with the cell phone to restrict the power what is actually needed. Thus, you are exposed to more power when you are in a weak signal area. this is why your battery runs down faster when you are in a weak signal area.If you are worried about radiation from your cell phone and it your hours or office gets a weak signal, you might want to install a femtocell. -Arch dude (talk) 16:20, 2 August 2008 (UTC)[reply]

Predatory Dinos

I remember reading a book on predatory dinosaurs a long time ago, which wass mainly about theropods, but had some passing references to 2 other types of carnivorous dinos, herreravians, which I don't know how to spell, and another which I forget. Google turns up nothing. they might have undergone a name change. Does anyone have an info on these "herreravians"? Sliver Slave (talk) 02:13, 2 August 2008 (UTC)[reply]

Herrerasauridae ? They are technically theropods AFAIR. --Dr Dima (talk) 03:09, 2 August 2008 (UTC)[reply]

Allylic halides and nucleophilic substitutions

How do you know when an allylic halide would rather undergo S_N1 rather than S_N2? Is there some sort of rule? I ask because my organic chemistry textbook just says that allylic halides can undergo both but doesn't mention specific conditions for either. On top of that, one of the exercises just claims "S_N2 conditions!" with no explanation of why it's S_N2-favoring conditions. --M1ss1ontomars2k4 (talk) 03:35, 2 August 2008 (UTC)[reply]

There may be something specific to sp²-hybridized carbons (in which I'd be quite interested), but ignoring that, I think the conditions favoring S_N1 or S_N2 mechanisms are the same as for sp³-hybridized carbons: Polar solvents, more-substituted carbons, and stearically hindered attack angles (opposite the leaving group) favor S_N1, the opposite conditions favor S_N2. —Keenan Pepper 04:47, 2 August 2008 (UTC)[reply]

See Neighbouring group participation which speeds up both SN1 and SN2 reactions (quite a lot)87.102.86.73 (talk)

Thanks! I actually found it in my notes already. I never remember a thing about my notes once I've taken them; it turns out that nonpolar solvents tend to favor S_N1, whereas polar aprotic solvents encourage S_N2. --M1ss1ontomars2k4 (talk) 04:54, 2 August 2008 (UTC)[reply]

I think it's the other way round - polar solvents should favour SN1 !87.102.86.73 (talk) 12:38, 2 August 2008 (UTC)[reply]

Yes there is something special about allylic halides assuming you mean XCH₂-CH=CH₂ etc (and not CH₂-CH=CHX which are vinylic haldide technically)

SN1 is favoured compared to a normal alkylic halide due to stabilisation of the carbon cation CH₂⁺-CH=CH₂ by resonance

eg CH₂⁺-CH=CH₂ and CH₂=CH-CH₂⁺

Additionally SN2 can occur at the gamma carbon too eg

XCRH-CH=CH₂ + Y^- >>> CRH=CH-CH₂Y + X^-

Watch out for the above reaction when the question says SN2 conditions. —Preceding unsigned comment added by 87.102.86.73 (talk) 12:36, 2 August 2008 (UTC)[reply]

Actually Neighbouring group participation points out that allyl groups have faster SN2 reactions as well...87.102.86.73 (talk) 13:40, 2 August 2008 (UTC)[reply]

Can you explain this 'major discovery'?

What was the novelty the MIT team in fact discovered in this press release? [18]. When electricity -- whether from a photovoltaic cell, a wind turbine or any other source -- runs through the electrode, the cobalt and phosphate form a thin film on the electrode, and oxygen gas is produced. Well, I thought the production of oxygen and hydrogen from water would happen with any electrode, just using the electricity.

So, they convert surplus electricity to H2/O2 for storage. Where is the deal? --Ayacop (talk) 07:05, 2 August 2008 (UTC)[reply]

See User talk:SteveBaker#Interesting? for discussions made by one of the greatest (ex-)RD contributors on this topic. --antilived^{T | C | G} 07:44, 2 August 2008 (UTC)[reply]

Thanks. To summarize, splitting water with normal electrodes isn't 100 percent efficient (probably producing too much heat), so that can still be optimized which they apparently did. I hope the PR writer will never edit Wikipedia. --Ayacop (talk) 07:52, 2 August 2008 (UTC)[reply]

Confirmed. As I understand it, using two platinum electrodes is about 60% to 70% efficient [19], with the rest lost as heat. Nearly all of the loss is at the anode where O2 is made [20]. Nocera's catalyst fixes the anode problem, increasing the overall efficiency to "near 100%" (can't find the exact figure), but still requires a platinum cathode to make the H2. The next step is to find a cheap cathode material. --Heron (talk) 13:59, 2 August 2008 (UTC)[reply]

Life time of hydrogen economy

A question that bothers me for a good time, already: How long can a hydrogen economy survive, given nonzero leaking of hydrogen into the atmosphere plus nonzero leaking of hydrogen from atmosphere into space? What's the order of magnitude of lifetime if you assume 5% leakage on earth, and the normal rate into space? --Ayacop (talk) 08:03, 2 August 2008 (UTC)[reply]

I assume by hydrogen economy you mean using hydrogen as main carrier of energy. But where would that hydrogen come from in first place? From water, consuming lots of energy, leaving O2, or from hydrogen carbons, consuming lots of energy, leaving, perhaps graphite or soot? I admit I never understood the benefits. As for the leakage, I guess H2 would be oxidized pretty fast and the leakage into space would be quite that from natural water vapor. 93.132.136.138 (talk) 11:29, 2 August 2008 (UTC)[reply]

As far as I'm aware, most proposals for a hydrogen economy have it coming from seawater since we have it in abudance. 5% leakage seems rather high to me but even so, I expect it would last several million years or more. I don't think anyone seriously thinks were going to run out of seawater. The main problem is finding a way to produce the energy needed to produce said hydrogen. Nil Einne (talk) 12:31, 2 August 2008 (UTC)[reply]

A quick calculation shows that, at current world energy consumption levels, even if we assume that all the hydrogen we burn immediately vanishes into space by magic, we still have 30 million years or so before we run out. We are not going to run out of ocean any time soon. Algebraist 12:50, 2 August 2008 (UTC)[reply]

The article hydrogen economy states. "As an energy carrier, hydrogen could substitute for dwindling supplies of petroleum and provide energy independence to countries without oil resources."

How could that be? 93.132.136.138 (talk) 13:12, 2 August 2008 (UTC)[reply]

I think the principle is Nuclear+Wind+Hydro etc >>> Energy and then Energy+Water >>> Hydrogen

Thus avoiding any petroleum in the chain.

However I can't imagine Hydrogen power ships/planes/trains anytime soon - so I think the emphasis is on could87.102.86.73 (talk) 13:37, 2 August 2008 (UTC)[reply]

So the energy independence really comes from "Nuclear+Wind+Hydro etc". Why is the article falsely implying hydrogen alone could lead to energy independence? 93.132.136.138 (talk) 13:55, 2 August 2008 (UTC)[reply]

It's slightly misleading perhaps "As an energy carrier, hydrogen could substitute for dwindling supplies of petroleum and provide energy independence to countries without oil resources when coupled with alternative energy sources"

Is that better - make the change yourself if you wish.87.102.86.73 (talk) 14:12, 2 August 2008 (UTC)[reply]

It would still be subtly but massively misleading. Energy independence does not depend on the energy carrier but on the energy resources. For renewable energies, this is mostly land, and not an alternative (though a valuable supplement) for highly populated countries. 93.132.136.138 (talk) 14:49, 2 August 2008 (UTC)[reply]

In the current world, you need both an energy carrier and energy resources. While trains in particular can use electricity most other forms of transport including air, sea and trucks+cars and a lot of other stuff (e.g. farm machinery) can't for long distance at least given the current state of battery technology (fuel cells may change this although I suspect it will be a long, long time before we're using electric planes). Also I don't think it purely depends on land. A desert country for example can get a lot more out of solar then say, Scotland. Some countries have good access to geothermal, others don't. Inland countries have no access to tidal power. Wind is better in some countries then others. Hydro depends on rainfall, rivers etc. And some countries have a lot of uranium, others not much. Tropical countries can potentially produce an equivalent amount of biofuels with less land usage then temperate countries (although again this varies a lot from location to location) although of course if you are producing biofuels you may not need hydrogen as an energy carrier. Fresh water may be a limiting resource for biofuel production in some cases Nil Einne (talk) 16:46, 2 August 2008 (UTC)[reply]

I tweaked the article in an attempt to make it less ambiguous. --Heron (talk) 14:44, 2 August 2008 (UTC)[reply]

Note that hydrogen could potentially be used for energy storage as well as an energy carrier. Energy storage is particularly vital for renewable sources which (barring hydrogen and perhaps geothermal to some extent) tend to be unreliable and also can't respond to demand & may also be useful for nuclear which can only respond very slowly to demand. Currently the only energy storage I'm aware of suitable for power stations is pumped hydro. (Non-pumped hydro can of course also respond on demand and can be used to supplement other renewable sources and nuclear but isn't an energy storage system.) Energy storage may also be deemed necessary for security reasons (e.g. if a big chunk of your power is coming from solar and your solar power stations are mostly in one area that may be deemed a big security risk.) Hydrogen could also potentially be used as an energy carrier over long distance where simply high tension wires are not deemed feasible e.g. desert countries could produce hydrogen via solar power and sell it to countries with less available solar power (obviously this doesn't help energy independence), some ideas appear to be here [21]. Of course all these are simply possibilities what actually happens is anyone's guess (I personally believe the hydrogen economy idea is overated) Nil Einne (talk) 16:59, 2 August 2008 (UTC)[reply]

Pumped air and NaS batteries have also been demonstrated for energy storage at the power station scale. Dragons flight (talk) 16:52, 2 August 2008 (UTC)[reply]

Zenker's Diverticulum is well know among Gastroenterologists, who was Zenker and where did he publish his new disorder?

As a retired medico, I have encountered patients with Zenker's Diverticulum. Most embarrassing when I had to admit to one of them that I didn't know who Zenker was. That was before Wikipedia, of course! —Preceding unsigned comment added by 77.127.125.172 (talk) 12:12, 2 August 2008 (UTC)[reply]

Um now that this is after Wikipedia, did you try looking at Zenker's Diverticulum? Seems the obvious place to look... Nil Einne (talk) 12:25, 2 August 2008 (UTC)[reply]

Applied maths

Which type of engineering uses the most maths and which uses the least? I would also liek to ask the same question for physics. Clover345 (talk) 17:54, 2 August 2008 (UTC)[reply]

How do you measure maths and physics? Without knowing that, there's no way of telling who uses most. 93.132.136.138 (talk) 19:18, 2 August 2008 (UTC)[reply]

As a gross generalization someone majoring in biophysics will have probably have taken fewer math courses than someone majoring in theoretical particle physics for example. Physics pretty much entails doing math, though the complexity of the math varies from problem to problem and depends on how difficult you want to make it and what sort of answer you are looking for. If this question relates to picking a major, it is probably best to look at the major requirements are at whatever institution is relevent. If you are asking which type of physics or engineering is the "harder science" (vs. the "softer science"), I don't think you can get an answer everyone will agree on. —Preceding unsigned comment added by 71.16.107.2 (talk) 19:58, 2 August 2008 (UTC)[reply]

Probably the heaviest use of mathematics in physics is in particle physics, especially string theory (a lot of which is indistinguishable from pure mathematics). In engineering I have no idea—aerospace? The least mathematical is harder to judge because of the fuzzy boundaries of both subjects. Building Lego structures could count as engineering and juggling could count as physics. -- BenRG (talk) 20:00, 2 August 2008 (UTC)[reply]

Why didn't man evolve wings?

I thought that every life form evolved based on need. Don't get me wrong, I believe in evolution , but it seems odd that such a useful trait wasn't given to us. Instead it was given to birds, and insects (As if they need it. There's too damn many of em, already!)

But seriously, imagine how useful it would be.- Gas crisis? Solved! Road congestion? Solved! Elevator repairmen? Sadly, unemployed. Oh well, there's always a trade off. Hey, I'm Just Curious (talk) 18:18, 2 August 2008 (UTC)[reply]

If "that would be handy" was the only factor in the natural selection of animals, birds would long ago have evolved into F-15 Strike Eagles. There are costs as well: flying needs one to be light (which generally means small, with thin honeycombed bones) and strong (a winged human would have impossibly massive chest and back muscles), and (for larger animals at least) flight is very expensive (energy wise). Animals all live in a complex multivariate world - you have to survive drought and famine and flood and you have to exploit times of plenty when they come, and you have to find a niche in life that isn't occupied by something that's better at living there than you are, and doesn't make you lunch for too many other things. And (returning to the lighter-hearted tone of your question) wings are for chickens. -- Finlay McWalter | Talk 18:34, 2 August 2008 (UTC)[reply]

(EC) If you're talking about traits being 'given', you don't understand evolution. If you think life forms evolve base on 'need' you also don't understand evolution. I don't say this to put this down, simply suggest that you may want to read our articles, e.g. Introduction to evolution, Evolution & Modern evolutionary synthesis since it will help you answer this question for yourself and a lot more besides like asking 'why' something didn't evolve is pretty pointless. But to put it simply, evolution doesn't happen based on need. 'Nature' doesn't choose what traits would be best for an organism and add them because it 'know's' the organism 'needs' them (that's a design view not evolution). Instead, random/spontaenous mutations give rise to different traits. If a trait is advantageous in a organism population's current niche, then it is likely this trait will become more common in that population over time (see Adaptation). There is no guarantee a trait is going to arise, and even if it does, there is no guarantee it will be fixed in the population even if it's advantageous. Also, flight requires a lot of tradeoffs (e.g. light body) and it's unlikely to be advantageous for humans to have natural flight in any case IMHO. (Not that this matters since as I've said, traits aren't selected in any way). And BTW, flight is itself a very complicated trait and only arose after a lot of mutations and their corresponding different traits lead there. Since as I've said, there is no overall purpose (i.e. there was no consideration, we need flight and we need to do this to get there), understanding how & why flight evolved in any given organism that has flight is not so simple as it may seem. (Although it's worth understanding not every single step happened because it was advantageous, see genetic drift and that we can never know for sure why something evolved, we can only speculate on possibilities.) This is a greatly simplified view of evolution and not entirely accurate so I suggest you read the linked articles if you want to learn more. Nil Einne (talk) 19:00, 2 August 2008 (UTC)[reply]

If you read Last and First Men you'll see that we will eventually have wings, we just haven't got there yet. Dmcq (talk) 19:45, 2 August 2008 (UTC)[reply]

If we had wings we wouldn't have arms. If we had wings we'd be birds, and we'd be wondering why we don't have arms, as we have to use our beaks and feet for everything. --M1ss1ontomars2k4 (talk) 19:51, 2 August 2008 (UTC)[reply]

Those before me have posted useful links, another would be Common_misconceptions#Evolution. --Mark PEA (talk) 21:50, 2 August 2008 (UTC)[reply]

Synthesis problem

How might this synthesis be accomplished? I'm guessing that butadiene becomes the central part of the new molecule, but I don't see how to do the addition. --M1ss1ontomars2k4 (talk) 19:41, 2 August 2008 (UTC)[reply]

What does the text say eg "from any SM and S-C" - What does that mean.?87.102.86.73 (talk) 20:10, 2 August 2008 (UTC)[reply]

The little note says "from butadiene and any Starting Material 5 Carbons or less". --20:20, 2 August 2008 (UTC)

Oh, I was thinking that if I started with cyclopentene and used a bromine radical to abstract an allylic hydrogen, I might add that way, with 1 π electron from each double bond moving inward to form the new double bond and the other π electron moving outward to form a new bond with the allylic radical. --M1ss1ontomars2k4 (talk) 19:47, 2 August 2008 (UTC)[reply]

We cannot do homework for people on the ref desk. We can help point you in the right direction though if this is indeed a homework question. You will need to extend the butadiene by forming new carbon-carbon bonds. You may need to add some more reactive functional groups to it first. Note that the end product is symmetrical, this might make things easier. --Russoc4 (talk) 19:50, 2 August 2008 (UTC)[reply]

I'm not asking you to do my homework. I've already thought about it, and several classmates have already spent a great deal of time thinking about it (or so they've led me to believe). I've been here probably just as long as you, and I don't appreciate the fact that you assumed I was trying to get others to do my homework for me. This problem is neither homework nor required; I ask because there is an exam on Monday and this showed up in the professor's review handout (which has no solutions, just questions), and I'm assuming that we are expected to know how to do it, when I can't find anything in my notes or the text that seems to help with extending the butadiene or usefully adding functional groups.

The closest I've come so far is this: first hydroxylize the double bonds (monohydroxylation with BH3), use PCC without water to get to the aldehyde, convert cyclopentadiene into an organocuprate, then mix them up. Get rid of the carbonyl oxygen with whatever's handy, and you end up with something similar to the product but lacking a double bond. Besides the obvious problem of not making the desired molecule, this synthesis is far longer than our professor usually expects of us. Also, this is a class, not real life, so we're not expected to use BH3 as that was featured in another class. --M1ss1ontomars2k4 (talk) 20:19, 2 August 2008 (UTC)[reply]

I don't know if it is relevant to this problem, but don't forget the possibility of designing a reaction so that the rings of the molecule close up on their own. 71.16.107.2 (talk) 20:08, 2 August 2008 (UTC)[reply]

(convert to di-epoxide, react with 2x (3-metallo-cyclopenta-1-enyl) grignard, convert to 1,2 dioxide to an alkene...? There must be a better method)87.102.86.73 (talk) 20:15, 2 August 2008 (UTC)[reply]

As I've said elsewhere, this is a class, not real life, so while that may be a viable method of synthesis, converting alkenes to epoxides and using Grignards on them is probably not part of the solution. Pretty much the only tools we have are carbonyls and delocalized pi systems. --M1ss1ontomars2k4 (talk) 20:25, 2 August 2008 (UTC)[reply]

It says use any starting materials 5 or less C chains. What's wrong with Grinards? Is this what we've come up with so far, because it's all I can think of. I can't quite figure out how to get the double bond back without disrupting the cyclopentenes. And you aren't allowed to use reactions you've previously learned?? --Russoc4 (talk) 20:31, 2 August 2008 (UTC)[reply]

Update: is the last step here possible? --Russoc4 (talk) 20:46, 2 August 2008 (UTC)[reply]

Well I'm certainly allowed to use reactions I've previously learned, but all previous test questions I've done so far for this course haven't involved as much usage of "old stuff" as we've been using here, and this is from a review guide thing for the chapter on delocalized π systems. Plus, the teacher specifically mentioned that stuff from our previous course would not be tested in this course (except for basic things like ozonolysis, hyrdogenation of double and triple bonds, and oxidation with PCC and/or chromate) and that our syntheses should use stuff from this course. That's why I'm hesitant to use other stuff. As for the first image, that was indeed my thoughts, but like we've said, it doesn't quite work. The other reaction you've suggested can afford the desired product if ??? is PCC or chromate followed by Wolff-Kishner reduction, I think. Like I said though, this question is supposed to be somehow related to delocalized π systems... --21:24, 2 August 2008 (UTC)

P.S. Those are nice drawings; I would have done the same but 1. ChemSketch isn't cooperating with Wine and 2. I haven't really figured out how to make a nice reaction sequence like that; the arrows are always too long, too short, or not straight. --M1ss1ontomars2k4 (talk) 21:24, 2 August 2008 (UTC)[reply]

(IF I was teaching I'd assume that epoxidation and grignard reactions were basic things)

Have you done pericyclic reactions yet - I can't help wondering if there is a 'clever' way to do this using a cycloaddition followed by rearrangement - but nothing I can think of makes any sense...87.102.86.73 (talk) 21:39, 2 August 2008 (UTC)[reply]

Oh, Grignards are quite often used in this course, just not in this particular chapter. So they're less likely to be involved in the solution, but it's certainly possible. Epoxidation has never even been mentioned in this course, so that's most likely out of the picture... We have indeed done pericyclic reactions (specifically, electrocyclic reactions and cycloadditions) and that stuff is also in the chapter that this problem came from. That was my first though too, given the context of the problem, but I couldn't see any way to do it either. --M1ss1ontomars2k4 (talk) 22:06, 2 August 2008 (UTC)[reply]

human cloning

in human cloning, can it be done to make someone at desired age or start from a baby? will their life style be similar to ours, lifespan,health? should all the parts be stitched into them? when life is put into them, will they feel totally blank or will they remember anything, atleast can their brain adapt soon to its ambience? —Preceding unsigned comment added by Shiniga (talk • contribs) 19:44, 2 August 2008 (UTC)[reply]

At the moment it's nearly impossible to clone humans. Once we do, however, it would have to start from a baby, and it would hopefully have similar lifespan and health. They won't remember anything, as we don't know how to transfer memories. Of course, it's possible that in the future we'll come up completely new techniques to transfer memories, start clones off as adults (or make them mature faster), or whatever. It's hard to say for sure, as we're currently stuck in the present, and we can't even solve the problem of getting an embryo to develop properly. --M1ss1ontomars2k4 (talk) 19:50, 2 August 2008 (UTC)[reply]

Another thing to take into account is that clones will develop differently from the "original" because it is impossible to place them in indentical environments and chance events in development will result in them having non-identical physical and mental features. Clones should theoretically have about the same level of similarity that identical twins have with each other (they are not completely identical mentally or even physically). One problem with clones produced from mature cells is that they really don't have the same DNA. Cells modify their DNA epigenetically in order to regulate the activity of genes and to differentiate themselves from each other. If you use the DNA of a skin cell to create a clone, it already has been modifed. The electric shock is intended to strip some of these modifications off, but this is kind of like using an axe to cut a slice of bread, it's not very clean or precise and some modifications may stick around or the DNA could be damaged. Geneticists suspect this can lead to some down the road health problems, so clones produced from already differentiated cells may have reduced health compared to "originals".

If a clone is produced like a normal baby, then it has a "clean memory slate" and should develop and behave like any non-cloned human will. Thus a clone will be fully "human" in that it has an independent conciousness and will and is a totally different human being than the original, the same way identical twins are separate people. A clone of Gandhi would not be Gandhi: raised in a normal environment the clone is no more likely to become a great political spiritual leader than any other human on earth.

Memory and consiousness is created by the physical layout of the neurons in the brain, the structure and other stuff going on inside of the neurons themselves, how they connect to each other, and how they signal to one another. To reproduce someone's memory and personality (this is speculation by the way), identical neurons would have to be stuck in the same places, connected the same way, and induced to signal each other just like the originals. Brain development relies in part on chance events that even two genetically identical brains in identical conditions will not develop exactly the same. It would probably be easier to try to brainwash someone to believe that they had a past experience than to try to reproduce a memory by controlling the brain's development or creating a copy of a brain. 71.16.107.2 (talk) 20:37, 2 August 2008 (UTC)[reply]

Pigs on the wing

How difficult would it be for humans to genetically engineer a pig with wings and the ability to actually fly?

@@ Line 435: / Line 435: @@
 :If a clone is produced like a normal baby, then it has a "clean memory slate" and should develop and behave like any non-cloned human will. Thus a clone will be fully "human" in that it has an independent conciousness and will and is a totally different human being than the original, the same way identical twins are separate people. A clone of [[Gandhi]] would not be Gandhi: raised in a normal environment the clone is no more likely to become a great political spiritual leader than any other human on earth.
 :Memory and consiousness is created by the physical layout of the neurons in the brain, the structure and other stuff going on inside of the neurons themselves, how they connect to each other, and how they signal to one another. To reproduce someone's memory and personality (this is speculation by the way), identical neurons would have to be stuck in the same places, connected the same way, and induced to signal each other just like the originals. Brain development relies in part on chance events that even two genetically identical brains in identical conditions will not develop exactly the same. It would probably be easier to try to brainwash someone to believe that they had a past experience than to try to reproduce a memory by controlling the brain's development or creating a copy of a brain. [[Special:Contributions/71.16.107.2|71.16.107.2]] ([[User talk:71.16.107.2|talk]]) 20:37, 2 August 2008 (UTC)
+== Pigs on the wing ==
+How difficult would it be for humans to genetically engineer a pig with wings and the ability to actually fly?