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June 1

Center of mass question

Suppose two particles, far from any other influence, are orbiting around their center of mass due to gravitation. Then, imagine that a third object is introduced to the system. This third object will obviously will move the center of mass. Will the two objects still move about the center of mass in the same way? If so, is this a general rule about center of masses? 173.179.59.66 (talk) 00:19, 1 June 2010 (UTC)

It is really complicated. See Three-body problem. With two particles, they will both orbit in ellipses around the centre of mass. With three particles, they can do all sorts of crazy things. --Tango (talk) 00:26, 1 June 2010 (UTC)

All right, I didn't expect it to be that simple, thanks. 173.179.59.66 (talk) 00:56, 1 June 2010 (UTC)

Generally in real systems you'll only have two bodies orbiting as a very-close-to-true two-body system, with the third body orbiting around the two bodies' center of mass from a much-farther distance. However, in our Solar System, small things like comets and other [[Kuiper belt] objects sometimes get disturbed just enough by the larger planets to be ejected into the central solar system, giving us the weird new comets we see on occasion (or the one that crashes into Jupiter). - User:SamuelRiv 1 June 2010

Sure, if the third body is small enough and far away enough not to significantly affect the other two bodies and is far enough away that the other two bodies essentially merge into one body, then you can get an approximate solution by doing the two-body problem twice. It would only be approximate, though. Exact solutions to the 3-body problem are only known for a few very specific (an unlikely to occur in real life) situations. --Tango (talk) 15:41, 1 June 2010 (UTC)

Tango - in an isolated 3-body system, as in a trinary (I don't use tertiary) star, these systems of a close pair with a far-away orbiter (no matter how massive they are) are the only ones observed. Of course the precise calculation is notoriously unsolvable, and in the case of a many-body solar system, it is utterly a mess with small-bodies being quite unpredictable. SamuelRiv (talk) 16:10, 2 June 2010 (UTC)

I wasn't aware they were the only ones observed, but it doesn't surprise me - more complicated 3-body systems tend to be unstable, so one of the three stars would probably break away from the other two sooner or later. If the far-away orbiter is sufficiently massive (which I think is unusual) then it will have a significant impact on the way the other two stars orbit each other. --Tango (talk) 16:14, 2 June 2010 (UTC)

That's not exacly right. Globular clusters do not fit within that cathegory. Dauto (talk) 20:40, 3 June 2010 (UTC)

Methanol in water

When something like methanol goes into aqueous solution, the hydrogen on the edges of the methanol form weak polar hydrogen bonds with the negative side of the surrounding water, thus the methanol goes into solution. But, why doesn't the oxygen in the middle of the methanol form some sort of similar bond with the positive, hydrogen side of other water molecules? It seems that if the outside of the methanol has a little bit of a positive charge, the middle might have the reverse. --The High Fin Sperm Whale 03:45, 1 June 2010 (UTC)

You are right! The Oxygen is a hydrogen bond acceptor. Have a look in the hydrogen bond article.--Stone (talk) 05:13, 1 June 2010 (UTC)

Sodium acetate heating pads

I have some of these pads, and one of them seems to recrystallise on its own, very slowly, without any stimulus. Its subsequent heating activity is, of course, impaired. Should I dispose of it, and if so, what is the safest way? Could I, for example, just put it into a rubbish bin? --TammyMoet (talk) 09:04, 1 June 2010 (UTC)

I hope this doesn't cross the line to legal advice, but as far as I understand, there is nothing toxic or otherwise particularly harmful in them. (Of course, you will make sure to separate the metal for recycling, identify the type of plastic used in the shell and sort it accordingly, water your flowers with the liquid and use the acetate to season some crisps...)--Rallette (talk) 09:58, 1 June 2010 (UTC)

Sodium acetate is not toxic in normal quantities; react it with acids and you get vinegar. There is probably a scratch in the bag that allows the unstable supersaturated solution to condense as crystals. You can dilute the sodium acetate with water and wash down the drain; shouldn't hurt any more than vinegar. --Chemicalinterest (talk) 11:09, 1 June 2010 (UTC)

Thanks for your help guys - you're really fast!--TammyMoet (talk) 13:20, 1 June 2010 (UTC)

The Relative Passage of Time

It is a common anecdote that the days seem to move faster as an adult than when you were a teenager and certainly faster than when you were a child. Does this phenomenon continue to accelerate during adulthood? That is to say does someone in their 40s experience time (on average) to be faster than someone in their 20s? TheFutureAwaits (talk) 11:00, 1 June 2010 (UTC)

I think it has to do with the "busyness" of your days. As a child one doesn't have many responsibilities and cares like adults do, so time seems to move slower for them. Time also seems to move faster when you are more busy. --Chemicalinterest (talk) 11:11, 1 June 2010 (UTC)

Yes, I'm sure that is a factor, but the effect of time speeding up seems to continue into retirement and even to accelerate, even when days are less busy. Dbfirs 13:23, 1 June 2010 (UTC)

And I'm a complete waster, with absolutely nothing to do all day, and still find that now, in my 30s, the years seem to fly by - unlike when I was, say, seven, and it seemed an eternity until I would be eight. One possibility is that things seem to last longer when they surprise you, and that children are permanently surprised. (It would be funny if it turned out to be physiological, to do with brain chemistry. There are drugs which alter the perception of time, so it's not impossible.) 213.122.61.131 (talk) 20:21, 1 June 2010 (UTC)

Think of it this way: when you are one day old the next day is one half of your whole life at that point, when you are 20 years that same day is 1/7304th of your whole life at that point. —Preceding unsigned comment added by 165.212.189.187 (talk) 13:26, 1 June 2010 (UTC)

Simvastatin toxicity

Is sequestered bile acids beyond what the body can tolerate to lower cholesterol levels the mechanism of Simvastatin toxicity in doses above 160mg? 71.100.8.229 (talk) 11:34, 1 June 2010 (UTC)

Simvastatin is one of the statin drugs that inhibit the enzyme HMG-CoA reductase that is part of the endogenous cholesterol biosynthesis pathway. Statin drugs do not sequester the bile, there are a separate class of cholesterol reducing agents that act through sequestration. There are several different types of toxicity that can occur with simvastatin. Can you specify what you mean? --- Medical geneticist (talk) 12:08, 1 June 2010 (UTC)

I can't seem to find more than the maximum dose as 80mg or the toxic dose as 160mg if that helps. I'm interested in all types of toxicity for Simvastatin from excess dose to interaction with other drugs or interaction of the implied conditions taking Simvastatin represents. For instance, high cholesterol is an indicated condition that suggests that medications which restrict blood vessels such as medications which dilate pupils are toxic in combination with the implications of taking Simvastatin, i.e. high cholesterol. 71.100.8.229 (talk) 13:10, 1 June 2010 (UTC)

Huge sinkholes in Guatemala

There are reports in the new about a gigantic sinkhole in Guatemala ([1]). A web search turns up stories about another occurrence in 2007 ([2]). How were these sinkholes created? Why do they look almost perfectly cylindrical? Where did the earth that originally occupy the hole go? —Preceding unsigned comment added by 173.49.15.136 (talk) 12:00, 1 June 2010 (UTC)

It starts with a system of caves, and an underground river. The river falls down a small hole, over time it enlarges the hole, the swirling motion as it does so tends to make the hole round. See Kettle hole, Plunge pool, and Pothole#Other_uses. Like this photo, sometimes they call them "Glory holes". Eventually there was a massive, and deep hole in there, covered by an earth "roof". Probably fed at the side, with a deep drain. The soil was all washed away by the river, as over time the land above falls down into the water. During that massive rain storm, probably the river level went up a lot, and washed even more soil. To the point that it could not support it's own weight, and fell in. If you look closely at the photo you'll see it's full of water at the bottom. Ariel. (talk) 12:37, 1 June 2010 (UTC)

So close to the meteor impact of 65 million years ago. How far down and how thick is the iridium layer in the hole? 71.100.8.229 (talk) 13:51, 1 June 2010 (UTC)

There might be little or no iridium layer actually at ground zero itself, as the huge explosion caused by the vaporisation of both the meteorite and the rock it struck would have blown all the meteoritic material (which contained the iridium in excess of usual terrestrial concentrations) high into the atmosphere, dispersing it around the globe. Although a small proportion of this material would have resettled at the immediate impact point, that immediate area would have been so heated and/or disturbed by the impact that it would have probably remained in state of turmoil (doubtless there's a technical word for this) long enough to mix up the fallout and prevent the formation of the obvious K-T boundary layer found elsewhere.

In the wider area of the Chicxulub crater, around whose boundaries formed the ring of cenotes/sinkholes that were the clue leading to the feature's discovery, the article's Geology and morphology section states "The K–T boundary inside the feature is depressed between 600 and 1,100 m (2,000–3,600 ft) compared to the normal depth of about 500 m (1,600 ft) depth 5 km (3 mi) away from the impact feature." The original paper from which these data are taken, Hildebrand, Penfield et al 1991 4, might also give the layer's thickness. (87.81.230.195 (talk) 23:34, 1 June 2010 (UTC)

I would be careful with the term "glory hole", it has other meanings - Q Chris (talk) 15:21, 1 June 2010 (UTC)

Crayfish

Any crayfish experts here? - this question Wikipedia:Reference_desk/Miscellaneous#Fastest_Animal slipped through the net (excuse the pun).87.102.77.88 (talk) 13:16, 1 June 2010 (UTC)

The responses on the Miscellaneous page seemed to hit the nail on the head. Do you have a particular clarification you'd like? I will just emphasize two points: First, that the consensus seems that crayfish aren't fast in terms of velocity, but rather acceleration (0-60 in 3 seconds, to use a car term). It would be neat if we had a page on the fastest-accelerating animal, because surely none of those listed in Fastest animal would qualify.

Second, the key to this rapid response is a very conductive "wire" that can connect any kind of stimulus to the tail muscles almost instantly. Human reaction time in such a situation is at best 160ms, which for a crayfish would make them easy prey (finding a list of animal reaction times is very difficult, if someone might help). The essential problem is that the "wire" is a neuron, which is not a very good conductor. Mammals get myelin, a fatty insulation, around some neurons to make signals go faster, but arthropods have to instead make their response neuron thicker. At the end of the day, the sequence is that a stimulus from the eyes or wherever travels to the brain and then shoots down this giant neuron into the tail causing this very fast reaction kick. Sorry I can't be more specific. SamuelRiv (talk) 16:39, 2 June 2010 (UTC)

tendinosis or tendonitis?

Hi all. Are tennis and golfer's elbow examples of conditions caused by tendinosis or tendonitis? The articles on these conditions do not say. Presumably tennis elbow is a tendinosis as there is no inflammation involved and golfer's is a tendonitis because there is histological inflammation? If my presumptions are correct then the link to tennis elbow on the article on tendonitis should perhaps be removed? RichYPE (talk) 13:25, 1 June 2010 (UTC)

"-itis" means "inflammation", and "-osis" means "condition" (usually not a good one). Both golfer's elbow and tennis elbow are associated with inflammation. --Sean 16:26, 1 June 2010 (UTC)

I had heard that tennis elbow was not associated with inflammation, and the wiki article on this seems to say the same thing. 'The condition is also known as lateral epicondylitis ("inflammation of the outside elbow bone"), a misnomer as histologic studies have shown no inflammatory process.' RichYPE (talk) 16:05, 2 June 2010 (UTC)

The article goes on to say that there is inflammation, so I don't know what to think and will defer to someone with more expertise than myself. --Sean 18:23, 2 June 2010 (UTC)

Just by the way, it's spelled tendinitis; there's no o in the word. I assume this has something to do with the Latin (e.g. the Italian word for "tendon" is tendine). --Trovatore (talk) 04:52, 3 June 2010 (UTC)

What's a "Twin Cylinder Reversible Turbine"?

Looking at this 1913 patent, I'm confused: what is it supposed to do? It's obviously some sort of steam turbine; am I correct in guessing that it works inside a steam engine to make the engine more efficient? Nyttend (talk) 15:16, 1 June 2010 (UTC)

If I understand correctly (and I may not be), it is a steam turbine that can be put into reverse (i.e. it spins the opposite direction). Falconus^{p t c} 18:11, 1 June 2010 (UTC)

I wonder if 'cylinder' refers to piston and it is a turbine engine with a piston based gas generator eg Free-piston_engine#Gas_generators , not sure how that would be reversible.

It may not even be an engine - some variation on the fluid coupling seems possible.

Also could reversible mean 'reversing' rather than reversible as in thermodynamics?

(sorry I'm guessing) Is there a better link - all I saw was a very brief abstract - I'm not even sure it is steam from the info I've got. It's US Patent 1064824 - maybe someone else has better resources. 87.102.77.88 (talk) 18:40, 1 June 2010 (UTC)

Silly me here it is http://www.freepatentsonline.com/1064824.pdf

It was reversible as in 'can be put in reverse gear'. As far as I can tell it's a stand alone turbine as described.? In fact the patentee describes one of it's advantages as being compact and able to go in the base of a ship - so there probably wasn't any conventional steam engine involved.

Note - the engine seems to rely on gas flow, and there appears to be no expansion (didn't read it all) - this would have been a tremendously inneficient engine - one of the later patents that references this one corrects this flaw. ie this 87.102.77.88 (talk) 19:00, 1 June 2010 (UTC)

No wonder the inventor kept his day job; he was a prominent smalltown physician. I discovered this patent while researching to write an article about his house. Thanks for the input! Nyttend (talk) 21:49, 1 June 2010 (UTC)

force

what are active and passive forces? —Preceding unsigned comment added by 122.167.120.52 (talk) 15:33, 1 June 2010 (UTC)

A Google search for "active and passive force" results in these definitions from the University of Vermont College of Medicine (2000). Hope this helps, [sd] 16:19, 1 June 2010 (UTC)

I think the term passive force refers to something like friction or viscous force, which only exist as resistance to motion. Say I apply a pushing force of 500 N to a heavy box, but the friction prevents the box from moving. We know that the friction is equal to 500 N, since the box shows no acceleration. However, if I stop pushing, there won't be a 500 N of friction to cause the box to accelerate towards me. I think it is in that sense that the force is passive. --173.49.15.136 (talk) 12:33, 2 June 2010 (UTC)

Sima Martel and Sima Humboldt

Is the sunlight reach the bottom of it? And will animals survive if it drop into it? Is there any possibility there's ancient animals or plants live in it? roscoe_x (talk) 18:39, 1 June 2010 (UTC)

According to our (brief) articles about these holes, (Sima Martel and Sima Humboldt) they are both about 300 meters wide and about 300 meters deep. They aren't narrow holes at all. That means that the sun would only have to be about 45 degrees up above the horizon to light at least a portion of the floor. Google Maps says that they are at about 4 degrees of latitude above the equator - so there will be days in the summer when the sun shines vertically down into the holes, illuminating almost the entire floor of the sink-holes - except that the floor of the holes are slightly wider than the top - so there are probably some small regions that don't get sunlight. However, it's obviously quite light down there most of the time.

Given that, it would be very surprising if there were no plants down there - you'd expect seeds and fruits and nuts to fall down there all the time, so it's quite likely that the floor is mostly covered with the same kind of vegetation as the surface. Animals are a bit more problematic. It's hard to imagine very large animals getting down there and surviving long enough to breed in such a limited space...but anything that can climb a rock wall could make a living there - as could very small animals. With a constant influx of modern life raining down into the holes, it's hard to imagine 'ancient' things living down there. Having said that, many caves have unique life forms (typically, blind, white things) that evolved from animals that fell into the cave system somehow...it's not impossible that such things are in the darker corners. SteveBaker (talk) 00:40, 2 June 2010 (UTC)

Mafeking Oil - obsolete veterinary preparation

Just watching All Creatures Great and Small, and mention was made of a preparation called "Mafeking Oil". It was being used by a farmer as a muscle rub on a lame cow, and the cow had licked the oil off her leg and developed vesicles in her mouth. Siegfried duly castigated the farmer for using such an out-dated and dangerous treatment, and said that "the only good thing the Germans did in the war was to bomb the factory that makes it". So - it was some sort of embrocation, unavailable after the Second World War, and acidic. Anyone know what it was? I have googled, and found nothing (except another person asking the same question). DuncanHill (talk) 18:58, 1 June 2010 (UTC)

Hmm. Dippel's Oil is an unpleasant oil once used with livestock, though since it's supposed to repel animals I doubt the cow would have licked it off. I feel like I've heard of Mafeking oil before, too, but then I also find Shatner's bassoon to be plausibly part of the brain, so perhaps what we have here is just an example of James Herriot being a good writer.213.122.61.131 (talk) 21:02, 1 June 2010 (UTC)

According to a Google Books search, the book All Creatures Great and Small doesn't mention that -- it mentions castor oil, linseed oil, and cod liver oil, but no Mafeking oil. In fact no book of any sort is found that mentions that. Also no mention of mouth vesicles in any of his books. Looie496 (talk) 21:58, 1 June 2010 (UTC)

The vesicles were initially suspected to be foot-and-mouth disease, which I'm sure he does mention. DuncanHill (talk) 22:15, 1 June 2010 (UTC)

Have you considered artistic license? Mafeking being a suitable name for a potent medicine (ie from Siege of Mafeking) - possibly the hypothetical (and possibly imaginary) bottle had a military scene on ala Camp Coffee but with a greater suggestion of physical activity and free from any suggestion of lameness. Maybe simply the words 'mafeking' where enough in themselves. 87.102.77.88 (talk) 23:46, 1 June 2010 (UTC)

The potion referred to is indeed mentioned in televisionseries All Creatures Great & Small Season 4 episode 7 - Ace, King, Queen, Jack. It cannot be found on google, which doesn't mean it never existed. Maybe asking around at Thirsk area ( where Alf White aka James Herriot lived ) would shed some light, asking the oldest farmers around. They should still know it.

Eeee by gum, that be "Ma fuc*ing oil". Special invenshun of Alf Wright.220.244.245.42 (talk) 03:48, 15 January 2015 (UTC)

Not Sure what it's original purpose was, but it came from Mafeking South Africa. It was the oil used to make Shaka [The Zulu Chief] look young in the movie Shaka Zulu. Which it did by darkening his hair. I believe it was originally used as a heavy preserving oil to keep metal parts from rusting in wet areas. Essentially, like hiding the grey by putting motor oil in your hair. — Preceding unsigned comment added by 101.98.47.42 (talk) 08:37, 5 May 2018 (UTC)

Live bacteria in food

I know I sorta asked this question, but what other foods besides those containing dairy has live bacteria in it? The reason I ask is that I am extremely lactose intolerant and eating yogurt will not be beneficial to me. Nor would drinking beer. Just wondering. Thanks! Reticuli88 (talk) 19:17, 1 June 2010 (UTC)

Just about any food will have some non-zero number of live bacteria on it unless you just pulled it out of an autoclave. You breathe in a huge number of bacteria a day, and some of those bacteria land on your food. Is there a specific species of bacteria you are looking for in food? Googlemeister (talk) 19:21, 1 June 2010 (UTC)

I guess the same ones that are present in yogurt. The "good" bacteria. Reticuli88 (talk) 19:23, 1 June 2010 (UTC)

I know I've already given this answer but see Category:Fermented foods - most are not pasteurised - and so will still contain live bacteria. Clearly many are regional and you won't be able to get them whereever you are. I would guess Fermented soy products , Fermented bean paste , Fermented bean curd and Fermented fish are likely candidates, another is Sauerkraut

This [3] mentions some common products - miso is probably gettable in many places. 87.102.77.88 (talk) 19:41, 1 June 2010 (UTC)

For a list see the section just above Probiotic#Multi-probiotic 87.102.77.88 (talk) 19:45, 1 June 2010 (UTC)

Tempeh is a nice product. I enjoy it. Not sure if it provides what is called for. But it is a fermented soybean product. Bus stop (talk) 19:52, 1 June 2010 (UTC)

Just to state the obvious, remember if you want live bacteria, you can't cook your source or heat it much above 37 degrees celsius. Also based on our yoghurt article, have you looked for lactose free yoghurt? It evidentally exists in the UK Lactofree, seems likely it may exist in the US as well. And it seems soya yoghurt also exists. I presume some of these contain live cultures. Nil Einne (talk) 21:07, 1 June 2010 (UTC)

It is also possible to buy capsules containing such bacteria in health-food stores. I am neither recommending nor dis-recommending these; just letting you know they exist. --Trovatore (talk) 20:06, 1 June 2010 (UTC)

Kombucha contains loads of bacteria. Looie496 (talk) 22:01, 1 June 2010 (UTC)

I don't believe the health of your gut flora relies on regular consumption of live bacteria, contrary to what the advertisers of Yakult would want you to believe. Vespine (talk) 05:53, 2 June 2010 (UTC)

And, of course, contrary to what our articles Gut_flora#Alterations_in_balance and probiotics say. That not everyone will benefit from it is pretty clear: that many people in many different circumstances will benefit from it is supported by the evidence. The problem lies in the advertising suggesting that everyone needs it all the time: but then, there are plenty of adverts that talk about specific symptoms being relieved by probiotics. 86.164.69.239 (talk) 19:01, 2 June 2010 (UTC)

Gull wings

Does a gull wing or inverted gull wing cause more drag than a straight wing? Also, does it provide more or less lift? Thanks, --The High Fin Sperm Whale 19:36, 1 June 2010 (UTC)

I can't answer your question, but see anhedral and dihedral (aircraft). As a pilot, the difference that I have been interested in, is what they do for stability. Falconus^{p t c} 21:08, 1 June 2010 (UTC)

So what does it do to stability? --The High Fin Sperm Whale 21:29, 1 June 2010 (UTC)

RTFA? --Tagishsimon (talk) 21:47, 1 June 2010 (UTC)

I have no idea what "RTFA" means, but a dihedral makes an airplane more stable, and an anhedral makes it less stable. They sometimes put anhedrals on designs where the plane is too stable (you do need to be able to turn them, after all). The plane I fly (PA28) has a very distinct dihedral, making it very stable, which is what you want if you aren't planning on doing stunts. Falconus^{p t c} 22:43, 1 June 2010 (UTC)

I think there's a basic problem with answering your question - more or less under what conditions? for the same width, breadth, weight etc?87.102.77.88 (talk) 22:03, 1 June 2010 (UTC)

What I'm asking is, if you have have a straight wing and a gull wing of the same length, width, etc., what differences will it make to stability, speed, lift, drag, etc. And what does 'RTFA' mean? --The High Fin Sperm Whale 22:14, 1 June 2010 (UTC)

RTFA means that an answer to your "what does it do to stability" question was to be found by reading the articles linked to in the response above it. --Tagishsimon (talk) 22:52, 1 June 2010 (UTC)

And the 'F' should just be left to my imagination? Falconus^{p t c} 23:04, 1 June 2010 (UTC)

Flying. I'm sure it's flying... --Tagishsimon (talk) 23:11, 1 June 2010 (UTC)

We have an article, of course: RTFA. (Well, it's a redirect to an article in which "RTFA" is mentioned.) Comet Tuttle (talk) 23:56, 1 June 2010 (UTC)

At a basic level lift depends on the angle of attack - no difference as a first approximation.

Drag will depend primarily on the thickness of the wing - here again - no difference as a first approximation for wings of the same thickness.

Speed will be a function of drag - assuming the wings have the same sweep - no difference.

Stability - not sure here - but a gull wing has two angles for anhedral/dihedral , whereas a 'normal' wing has one and you haven't specified what it will be - so I don't think that is answerable yet. Ignoring that aspect for a moment -stability depends on the whole aircraft - ie the other smaller wings etc .. so impossible to say.

There should be an article comparison of different wing designs, benefits and drawbacks (Wing configuration is solid but doesn't answer it)- but I'm not familiar with the aviation area of this wiki - maybe someone else can point at a coverall article?87.102.77.88 (talk) 23:28, 1 June 2010 (UTC)

Actually if you read the article Gull wing from top to bottom I think you'll get the impression that the main reason for having a gull wing is to solve secondary (non flight) engineering problems (or issues with centre of mass) rather than any intrinsic pluses or minuses flight wise.. 87.102.77.88 (talk) 00:10, 2 June 2010 (UTC)

The gull wing and inverted gull wing have no effect on lift and drag, but they do provide the designer with the perfect opportunity to ensure adequate clearance between the propeller(s) and the ground; and to allow short undercarriage legs. Dolphin (t) 23:15, 2 June 2010 (UTC)

There is much more to the calculation of drag than implied here. The gull wing will certainly create some sort of vortex drag at its sharp bend - such drag appears also at the wingtips of aircraft, which is why some have the "winglets" at the tips. It will be negligible for low-speed gliders, but likely quite important for any modern powered aircraft. Unfortunately, I don't have the expertise or resources to answer in-depth. Why a gull will glide with such a wing configuration is also unknown to me, but consider looking up a nice computational model of bird flight. SamuelRiv (talk) 02:26, 3 June 2010 (UTC)

Stukas

The article on the Stuka (in the specs section) says it has two forward MG 17 machine guns. Are these the removable pods mounted on the wings (such as the picture left) or are these internal and non removable? And when these machine gun pods are mounted, can the two 110 bombs still be mounted on the wings? --The High Fin Sperm Whale 20:20, 1 June 2010 (UTC)

The article on the Stuka says The offensive armament was two 7.92 mm (.312 in) MG 17 machine guns fitted in each wing, operated by a mechanical pneumatics system from the pilot's control column. original research but I would not think it would interfere with the bomb load. MilborneOne (talk) 20:26, 1 June 2010 (UTC)

The plane in that picture has some enormous guns! Are those really MG 17s? Here's a cross section of a Ju87(b) with guns internal to the wing: [4] ... this was normal. 213.122.61.131 (talk) 20:43, 1 June 2010 (UTC)

If you read the Junkers Ju 87#Ju 87G section, it's immediately clear that your picture shows a variant used for anti-tank warfare on the Eastern Front. Not many were ever produced, I guess. The large guns are evidently 37 mm Flak 18 cannons. The article also says that they were designed to carry one 1000 kg bomb. Buddy431 (talk) 20:50, 1 June 2010 (UTC)

Or maybe BK 37 cannons based on the earlier Flak 18 cannons (and superseded by the 3.7 cm FlaK 43? Those articles need to make clearer the relationship between the different guns). Buddy431 (talk) 20:56, 1 June 2010 (UTC)

(ec) The photo caption notes that the gun pods are 37mm cannon, probably for an anti-vehicle/anti-tank role. They appear to be fixed to the hard points that would otherwise mount the 50kg bombs. — Lomn 20:51, 1 June 2010 (UTC)

Sinkhole

In Guatamala, where did the contents of what is now a sinkhole go? It's not like the Earth is a hollow ball and it fell into the center, right? DRosenbach ^{(Talk | Contribs)} 22:19, 1 June 2010 (UTC)

Dissolved away over many hundreds/thousands of years like other features where the bedrock is limestone. There was probably a limestone cave beneath the sinkhole whose roof collapsed suddenly, the space had already been created. Mikenorton (talk) 22:35, 1 June 2010 (UTC)

(edit conflict..modified) - for this reason sinkholes are often connected to cave systems and underground rivers Subterranean river

For the final collapse see the second to last paragraph in Sinkhole. 87.102.77.88 (talk) 22:38, 1 June 2010 (UTC)

There's a nice diagram of tooth decay limestone cave formation here [5] (scroll down).87.102.77.88 (talk) 22:40, 1 June 2010 (UTC)

See also Wikipedia:Reference desk/Science#Huge sinkholes in Guatemala, above. --Tagishsimon (talk) 22:36, 1 June 2010 (UTC)

See also sinkhole and cenote. Cacycle (talk) 22:38, 2 June 2010 (UTC)

June 2

Decaffeinated coffee acclimatisation

Can decaffeinated coffee still have an effect, whether placebo or directly? I mean, clearly it contains nothing to compete with adenosine so it can't work the same way, and I'm skeptical, but decaffeinated coffee definitely has an effect on my personal sleeping habits. Why would this be? How? Regards, --—Cyclonenim | Chat  00:36, 2 June 2010 (UTC)

One thing to keep in mind is that decaffeinated coffee may still contain clinically significant amounts of caffeine. I suspect this is especially true for higher-quality blends, where the priority is flavor rather than removing all the caffeine you possibly can, but I don't really know that. --Trovatore (talk) 00:46, 2 June 2010 (UTC)

Decaffeinated does not mean caffeine free. --Chemicalinterest (talk) 00:59, 2 June 2010 (UTC)

I would be quite surprised if there wasn't a placebo effect, but generally that would require the drinker to think they were drinking regular coffee. I'm guessing that isn't the case with you, so it is unlikely to be placebo. It could just be confirmation bias, though. Alternatively, Trovatore may be right and the small amounts of caffeine still in the coffee are having the effect. --Tango (talk) 01:08, 2 June 2010 (UTC)

Our article on decaffeination makes reference to an "international standard" that 97% of the caffeine must have been removed, and to an "EU standard" that the beans must be 99.9% caffeine-free. On the other hand, one of the references is to this Science Daily article, which implies that decaf may have as much as 20% of the caffeine of regular coffee.

These facts seem somewhat difficult to reconcile. One possibility is that the coffee referred to by ScienceDaily was not compliant with either of these standards. Another is that beans consisting of 0.1% caffeine by weight (how much is in normal beans?) still produce coffee with 20% the caffeine of regular (maybe in part because you need more coffee grounds to get the same concentration of flavor chemicals?). --Trovatore (talk) 01:40, 2 June 2010 (UTC)

The amount of caffeine is strongly influenced by brewing method, so it's difficult to make good comparisons. Ariel. (talk) 03:40, 2 June 2010 (UTC)

Original research: When I drink a carbonated beverage, I instantly feel a buzz whether or not it has caffeine; I have to think this is some sort of placebo effect my brain is pulling on me (unless it's the carbonation itself). -RunningOnBrains^(talk) 05:25, 2 June 2010 (UTC)

I'd guess it's the sugar giving you the buzz. --Tango (talk) 11:00, 2 June 2010 (UTC)

Can you even get a placebo effect if you know it is a placebo? Googlemeister (talk) 13:47, 2 June 2010 (UTC)

Maybe with a bit of doublethink! --Tango (talk) 16:16, 2 June 2010 (UTC)

Still has caffeine, but maybe similar chemicals (take one or two methyl groups off) also give insomnia. That rooibos tea and chicory root is caffeine free but still has other stimulants. Polypipe Wrangler (talk) 13:40, 2 June 2010 (UTC)

Thanks for the responses :) Regards, --—Cyclonenim | Chat  17:05, 2 June 2010 (UTC)

Different kinds of cold?

Why is it that I could stand cold weather or the temperature in Baguio City but shiver when near an air conditioning unit? Do outside weather and air conditioning cools us differently?--Lenticel ^(talk) 02:12, 2 June 2010 (UTC)

For one thing, the air conditioner is probably blowing the air at you. Moving air will almost always "feel" colder than standing air. (See Wind chill for an extreme example of this). Buddy431 (talk) 02:39, 2 June 2010 (UTC)

One thought is that usually when you're outside you're not just hanging out, you're doing something even if it's only walking from place to place. Inside you're liking to be sitting in a chair and not exerting yourself. APL (talk) 04:17, 2 June 2010 (UTC)

Unfortunately, Thermoception is not a very good article, but that may be what you're looking for. We don't typically feel absolute hot and cold, just relative temperatures, so if you put one hand in hot water, another in cold water, and then put both in lukewarm water, the lukewarm water would feel hot to the hand that was in cold water, and vice versa. If you're air conditioning is much cooler. Also, you likely wear warm clothes outside in the cold, but not inside in your air conditioning. Furthermore, forgive a little teasing, but "cold" in Baguio City (record low: 46 °F (7.8 °C)) isn't exactly the same as the "cold" I know (record low: −24 °F (−31 °C)) -RunningOnBrains^(talk) 05:22, 2 June 2010 (UTC)

Dude, I live in the hot and humid tropics, so that's already cold :)--Lenticel ^(talk) 00:55, 3 June 2010 (UTC)

46 °F (7.8 °C)!?? Haha. I still wear shorts and a t-shirt in that kind of weather if there's not too windy! (admittedly, some neighbors think I'm crazy.)

Actually, the air coming out of your air conditioner could literally be colder than that. (Sure, your thermostat is set to something reasonable, but to achieve that it needs to mix some really cold air into your hot home.) APL (talk) 06:12, 2 June 2010 (UTC)

Air conditioners don't just cool the air, they also dry it, which makes it cool your skin more via evaporation. Since Baguio City, at an altitude of a mile above sea level in the Philippines, must be one of the most humid places on Earth, it can make a big difference. Looie496 (talk) 16:37, 2 June 2010 (UTC)

Humidity. Ah that's must be it! I mean the air is still humid even during the El Nino season. --Lenticel ^(talk) 01:22, 3 June 2010 (UTC)

"Dirty dozen" fruits and vegetables

CNN.com has an article on fruits and vegetables that contain pesticides even after being washed. The article has a "dirty dozen" list and a "clean 15" list of produce. What is confusing is that while potatoes and lettuce are on the dirty list, sweet potatoes and cabbage are on the clean list. Why? There seems to be no simple rules of thumb that can help you figure out for what produce you should go organic. --173.49.15.136 (talk) 02:40, 2 June 2010 (UTC)

My guess would be the susceptibility of the plant to damaging insect invasion leads to the use of insecticide. Bus stop (talk) 03:05, 2 June 2010 (UTC)

For sweet potatos, they may be assuming that people aren't going to eat the skin. That's what appears to separaten the clean vs. dirty foods to a large extent: whether people eat the outside layer. I like how they emphasize the number of different types of pesticides in the different types of produce. Wouldn't make more sense to look at the total amounts of pesticides, rather than the variety? Buddy431 (talk) 03:17, 2 June 2010 (UTC)

"Give me spots on my apples; But leave me the birds and the bees" (Joni Mitchell — Big Yellow Taxi) Bus stop (talk) 03:22, 2 June 2010 (UTC)

Who is applying so many different types of pesticide on the one foodstuff? I find it hard to believe that some foodstuffs contain up to 67 different pesticides. Caesar's Daddy (talk) 07:32, 2 June 2010 (UTC)

A lot of it's probably contamination from other types of produce grown nearby; a good wind and you've got on your plant whatever your neighbor put on his. Still, 47-67 different pesticides does seem pretty excessive. Is there anyone here with experience in this type of thing who can explain how, and how many, pesticides are typically applied to different types of food? Buddy431 (talk) 16:34, 2 June 2010 (UTC)

A "single" pesticide, may actually be a combination of multiple chemicals. Like how with roundup the article mentions how roundup itself is pretty safe, but it's extensive list of additives are the problem. It doesn't say how many it has, but if other pesticides are like that, that could easily increase the number. Just a guess. Ariel. (talk) 18:53, 2 June 2010 (UTC)

Terraformation of Mars

In this picture, they show an artists conception of the terraformation of mars. In stages 3 and 4, they basically just add more water, making the oceans bigger. What exactly is the advantage of that? Wouldn't it be better to have more land than oceans? ScienceApe (talk) 03:42, 2 June 2010 (UTC)

Perhaps because oceans might help regulate the Martian climate better Ocean#Climate_effects.--Lenticel ^(talk) 03:47, 2 June 2010 (UTC)

Water is also the most important greenhouse gas on Earth, and given how cold Mars is, covering a larger surface area with standing water might contribute to getting more water into the air to help support this warming. (Of course to get an ocean in the first place you already have to add something to the atmosphere to trap heat and keep the water from simply freezing.) Dragons flight (talk) 03:53, 2 June 2010 (UTC)

There are several reasons to have an ocean. First, the above-mentioned greenhouse effect. Second, water has a very high specific heat capacity, and because it is mostly transparent, serves as a giant heat sink, which keeps the earth's temperatures from fluctuating too much over the course of a day (currently, martian temperatures can change almost 100 °C (180 °F) in a day). Thirdly, if you hope to terraform a planet, and introduce large amounts of life, you're going to need large amounts of water.

Unfortunately, terraforming Mars is unlikely to work. Mars' low mass means that, unlike on earth, important molecules such as nitrogen, oxygen, and, yes, water vapor can escape its gravity directly into space over time. Thus, we would need to constantly replenish any atmosphere we created there. This is of course ignoring the HUGE question of "where the heck to we get a planet's supply of water and oxygen from in the first place?" :-D -RunningOnBrains^(talk) 05:08, 2 June 2010 (UTC)

Atmosphere loss is only significant on a geological time scale. Unless the teraforming is planned to take billions of years, replenishing the atmosphere would be trivial compared to the task of creating one in the first place. --Bowlhover (talk) 08:11, 2 June 2010 (UTC)

To get the water there in the first place (assuming we don't find enough frozen down under the surface already) would probably require bombarding the planet with icy asteroids - no small feat! The whole issue is really about how to warm the planet up - doing that would make it possible to drive water and various gasses out of the soil. There is a lot of frozen CO2 at the poles, melting the icecaps could liberate that and cause enough of a global warming effect to heat up everything else. Once things are warm and there is a denser atmosphere (albeit mostly of CO2) then you'd want to add photosynthesis to the mix to turn CO2 into oxygen. But this is a crazily difficult project. Nobody should ever underestimate the difficulties. SteveBaker (talk) 11:53, 2 June 2010 (UTC)

Indeed, it is beyond our ability to really conceive of how it would be done. It's not going to be done in the next 25 years, and as far as technology is concerned any predictions more than 25 years ahead are little more than guesses. --Tango (talk) 16:18, 2 June 2010 (UTC)

There are arguments that the bulk of Mars' former atmosphere has not been lost to space, but rather has become locked up in its rocks because, unlike on the Earth, it does not get recycled by tectonic activity and active vulcanism. Theorists such as Martyn J. Fogg (a personal acquaintance) have proposed releasing significant quantities from appropriate strata by large scale thermonuclear engineering (i.e. bury huge H-bombs and set 'em off, preferably from a distance). Such released gasses might, by positive global warming feedback mechanisms similar to those we ourselves are arguably experiencing, cause further atmospheric evolution and result in a useful atmosphere quite rapidly, which might persist on a timescale of the order of 100,000 years or more before further replenishment became necessary. 87.81.230.195 (talk) 22:09, 2 June 2010 (UTC)

I was under the impression that lack of a magnetosphere was a (the?) reason Mars doesn't have an atmosphere. From the magnetosphere article: "Earth’s magnetosphere provides protection, without which life as we know it could not survive. Mars, with little or no magnetic field is thought to have lost much of its former oceans and atmosphere to space in part due to the direct impact of the solar wind." How this would play out in human timescales with respect to terraforming, I have no idea. --- Medical geneticist (talk) 22:58, 2 June 2010 (UTC)

On human timescales, it would have very little effect. The Earth effectively loses its magnetic field for a few years every few tens of thousands of years (see Geomagnetic reversal) and our atmosphere doesn't disappear. On geological timescales, it could easily have a very significant effect and may well be the leading reason for Mars not having a thick atmosphere now. --Tango (talk) 16:21, 3 June 2010 (UTC)

"This is of course ignoring the HUGE question of "where the heck to we get a planet's supply of water and oxygen from in the first place?"" -- Isn't there already a "planet's supply of water" frozen in the Martian polar ice caps? 67.170.215.166 (talk) 05:25, 4 June 2010 (UTC)

I think the supply of water is presumed to be coming from the asteroid belt and from comets, where some sort of renewed "bombardment" of the surface of Mars would happen to quickly place that water on Mars... especially while it is mostly uninhabited. A good description of how this would happen can be found in the Mars trilogy of books written by Kim Stanley Robinson. While certainly these books are works of fiction, they do provide real scientific thought on the topic including several competing methods for adding some bulk to the atmosphere. That really is the big issue, as once there is some bulk to the atmosphere you can then use plants and some bio-engineering to convert CO2 to water and other compounds needed for life. If you haven't read these books but are interested in Martian terraforming, these are simply must-read books... at least to carry on intelligent conversations with others who are discussing this concept.

Something else to consider is the Gaia hypothesis, where perhaps the introduction of living things on Mars would also sort of help to also foster an environment that would be favorable to other living things. I admit this is incredibly controversial and its application to terraforming is even more controversial still, but it is at least something to look at. It isn't entirely clear that Mars is completely without life either, although the conditions that Martian life forms are living under would be obviously different than what we find on the Earth and would be more like extremophiles if any are actually found. --Robert Horning (talk) 01:33, 6 June 2010 (UTC)

How much water Mars still has is subject to HUGE debate...but I don't think anyone would argue that there is enough to produce the picture above...especially if you are going to be using this water as a source for your oxygen (of which there is practically zero in Mars' atmosphere currently).

The "ice" caps are mostly frozen carbon dioxide, and they "melt" substantially every summer (CO2 does not melt but sublimates, or turns directly into gas).-RunningOnBrains^(talk) 20:19, 6 June 2010 (UTC)

Why use the water as a source of oxygen, when we could introduce some blue-green algae into the water and use them to turn the CO₂ in the atmosphere to oxygen? 67.170.215.166 (talk) 00:39, 7 June 2010 (UTC)

I believe there is oxygen contained in the molecules that make up the crust of the planet. ScienceApe (talk) 02:22, 7 June 2010 (UTC)

Well, if you use CO2 from the atmosphere, you are still left with an atmospheric pressure that is too low to comfortably support life. -RunningOnBrains^(talk) 15:16, 7 June 2010 (UTC)

To clear up a possible misconception, Photosynthesis#Light reactions, including those of blue-green algae, obtain the oxygen from water and not from carbon dioxide. -84user (talk) 18:33, 7 June 2010 (UTC)

Linde's chaotic inflation: why only one level of bubble universes?

Andrei Linde's theory of bubble universes (I don't know if "bubble universe" is the acccepted term, but you know what I mean) describes them as emerging from an ur-universe (again, I don't know the accepted term). However, from what I can find on wikipedia, Linde's theory doesn't describe bubble universes emerging FROM the first "level" of bubble universes (The "level" emerging from the ur-universe); and the previous statement can be extended to bubble universes emerging from the bubble universes that emerge from the bubble universes that emerge from the ur-universe. In other words, Linde's description seems to involve only one "level" of bubble universes.

However, theoretically, bubble universes could emerge from within THIS ("our") universe, which implies at least one more "level" of bubble universes.

Have I misunderstood Linde's description? Or, perhaps, are further "levels" implied by Linde, but he leaves the implication unstated in order to simplify his description? Have others theorized further "levels"? If so, have they described this as being different from Linde's description, or just a corollary to it? 63.17.75.70 (talk) 04:04, 2 June 2010 (UTC)

In the more esoteric but serious sciences called cosmology and superstring theory, there are many theories of bubble universes, these theories sometimes overlap. For a popular science sampling, you could search for "bubble universe" at www.newscientist.com. It's one of their favourite topics, with repeated coverage. From what I've seen, most such theories imply sometimes a chain of bubble universes of unspecified length, towards both the past and the future, and sometimes that our universe bubbled forth from something "simpler" like some kind of vacuum that's not a typical universe in its own right. Sometimes the future bubbling out of our universe involves black holes, sometimes something catastrophic happening to the vacuum energy. It's all theory and you can really pick and choose. EverGreg (talk) 12:07, 2 June 2010 (UTC)

The diagram I saw (colloquium by someone... perhaps a former student of Linde?) showed sub-universes forming in a sort of bifurcation pattern, so that, if I understand your question right, this universe may already be seeding other universes, but obviously we don't see it (the bubbles form outside our dimensions). That would describe many layers of bubbles. The bifurcation diagram in chaos theory is a nice illustration, though the chaos cutoff doesn't occur I don't think. SamuelRiv (talk) 18:09, 2 June 2010 (UTC)

Thanks -- although I asked a sub-question about "corollaries" and the like, my question is about Linde, specifically. Does his theory describe only one "level" of bubble universes (each one emerging from the ur-universe, and none in turn creating new bubble universes)? That's how it seems to me, but I can't understand why he would stop at one "level." 63.17.89.8 (talk) 02:19, 3 June 2010 (UTC)

Hi, I'm hoping to clarify - the lecture I saw was directly about these bubble universes, and distinctly showed multiple levels, if I understand your meaning correctly, in that our universe may be currently seeding many more universes. Incidentally, the model is very similar to that of a bubble, in which false vaccum (a nice positive energy state that's fairly stable and forms randomly) expands until it can't hold itself up, then either bursts (kaboom) or splits (or bifurcates) into smaller universes that repeat the process, such that there are presumably innumerable levels. SamuelRiv (talk) 02:31, 3 June 2010 (UTC)

As far as I know, in Linde's picture, the large flat regions (like the one we're in) are not chaotic enough to trigger further inflation. In other words, there's only one level. Other people (like Lee Smolin) have attached additional inflationary regions to black hole interiors, making for many levels. You shouldn't take any of this stuff very seriously, though. -- BenRG (talk) 09:35, 3 June 2010 (UTC)

BenRG -- thanks, that's exactly what I was looking for (does anybody else have more?). I disagree with you about not taking it seriously. THIS universe can (possibly) create bubble universes; therefore, it's reasonable (via avoiding anthropomorphic "specialness") to presume that this universe is in turn a bubble universe. Apparently, from what you've said, Linde either does not think that this universe can create bubble universes, or else did not describe such a model. 63.17.46.82 (talk) 04:40, 4 June 2010 (UTC)

Aha, it was Lee Smolin whom I saw give the lecture. I feel like a loser for not remembering, but I was a lowly sophomore at the time, and am not in cosmology. For what it's worth, I take it seriously - it's a very "philosophically comfortable" idea for me. And look... look - bear with me here - cosmology beyond the observable universe has to have a component of philosophical comfort, right? Comfort can certainly change with our changing perception of physics, but that is as much a basis for study as any, right? SamuelRiv (talk) 05:15, 4 June 2010 (UTC)

SamuelRiv, thanks for your responses -- they were useful, but (as you see) it was Linde I was after. But this does bring up another question (if anybody's listening): Lee Smolin wrote a book advocating (or maybe just describing the theory of?) "baby universes." Years later, in a celebrated comment, he said "This universe is the only one there is." I can't figure out if this means he abandoned the baby universe theory altogether, or if he was defining "universe" to mean "the universe that contains all the baby universes." Does anybody know how Smolin's two positions relate to each other? Also, again, I would appreciate more insight into Linde's position if anyone has any.63.17.83.221 (talk) 03:20, 5 June 2010 (UTC)

Lake Okeechobee

Is there any evidence such as shocked quartz, a gravity anomaly, and tektites in areas surrounding Lake Okeechobee in Florida, USA to suggest the lake might be the sight of an impact creator as far back as the end of the Cretaceous period? 71.100.8.229 (talk) 04:48, 2 June 2010 (UTC)

Lake Okeechobee hardly even exists, in a geological sense. It is 13 feet deep at its deepest point. There is a geologist named E. J. Petuch who suggested in the 1980s that the Everglades are the remnant of an ancient crater formed by a meteorite strike 38 million years ago, but he seems to have backed away from that idea, and I can't see any serious suggestions that apply to Okeechobee. The only thing in its favor is that it is sort of roundish. Looie496 (talk) 05:34, 2 June 2010 (UTC)

Reverse jet filter - pressure drop

Hi Can anyone tell me how to calculate the pressure drop in a reverse jet filter if I know the volume flow rate and dimensions of the filter bags, no and material of bags etc Thanks —Preceding unsigned comment added by 123.237.93.244 (talk) 05:36, 2 June 2010 (UTC)

Try Bernoulli's equation —Preceding unsigned comment added by 79.76.159.3 (talk) 09:21, 2 June 2010 (UTC)

Bernoulli's equation has a term for losses. It is that term which I am interested in. So if anybody has a model or correlation for obtaining the pressure loss in the reverse jet filter I will be grateful if you can share it. Thanks —Preceding unsigned comment added by 123.237.93.244 (talk) 09:44, 2 June 2010 (UTC)

What about this ref? [6] —Preceding unsigned comment added by 79.76.159.3 (talk) 23:50, 2 June 2010 (UTC)

mortality percent

What waist to hip or other body measurement ratio has the least percent of death for each age over 60 for males? 71.100.0.241 (talk) 08:50, 2 June 2010 (UTC)

Death is affected by many other factors, so hip measurement may only be a minor one. --Chemicalinterest (talk) 11:12, 2 June 2010 (UTC)

Yes, it is an indicator of heart disease and diabetes (fatter=more likely . suprised?) specifically it's relation in general to Body mass index eg very generalised or bmicalculate.net just google for "waste hip ratio +disease", and choose a disease.

Skinnys die too - and the percentage of death is close to 100% :)

Briefly covered at Waist-hip ratio there's a link in there too. 87.102.114.166 (talk) 12:29, 2 June 2010 (UTC)

LOL... the picture caught me by surprise... the article suggests that there is a correlation between WHR and offspring intelligence due possibly to more polyunsaturated fats the fetus needs for brain development. Maybe the real reason is that the fetus just wants to find ways to attract a mate with large quarters. :-] 71.100.0.241 (talk) 15:15, 2 June 2010 (UTC)

more[7] suggests 0.95 for men and 0.80 women is a good bet, these figures are for specific causes of death , this [8] for all causes of mortality death rate increases with waste to hip ratio.87.102.114.166 (talk) 13:11, 2 June 2010 (UTC)

This has some data. [9] I can't find the exact data you ask for.87.102.114.166 (talk) 14:18, 2 June 2010 (UTC)

This http://www.nhs.uk/chq/Pages/849.aspx?CategoryID=51&SubCategoryID=165 says your waist should be under 37 inches, for men. I would doubt there is a simple optimum - you should be slim but not literally starving, but sometimes becoming thin is a sign of having a serious illness rather than dieting, and this would distort the results upwards. 92.28.249.38 (talk) 14:38, 2 June 2010 (UTC)

Oxidation of copper by iron(III) chloride

When I placed copper in a solution of iron(III) chloride, the brownish yellow solution turned green. Is it due to this oxidation reaction: Cu + 2 FeCl₃ → CuCl₂ + 2 FeCl₂ Thank you. --Chemicalinterest (talk) 11:14, 2 June 2010 (UTC)

Think so Fe3/Fe2 standard potential is 0.77V , Cu2/Cu is 0.34V - the reaction would go, copper (II) chloride is green , ferrous chloride is pale. The potentials for chloride complexes are different, and I haven't bothered to find them since there's no big difference between copper and iron in this respect.87.102.114.166 (talk) 12:35, 2 June 2010 (UTC)

Or .. if you'd read Iron(III)_chloride#Industrial you'd have already seen the answer .. ... yes .. 87.102.114.166 (talk) 12:39, 2 June 2010 (UTC)

That's where I got my idea from; it was used as a copper etchant. It is unlike other metal-metal salt redox reactions in that another metal is not formed. I didn't see any copper(I) chloride intermediate like they stated in the article. --Chemicalinterest (talk) 13:33, 2 June 2010 (UTC)

I don't think the CuCl will be present in large amounts - it might not dissolve depending on the concentration of Cl- in solution. There might be some on the surface of the copper - eg use copper + FeCl3 dilute - remove the copper and wash the surface with (pure) water - a patina of CuCl (might) be present - any CuCl2 would be washed away by the water.

CuCl is white - not sure how to tell if it's in that solution (as CuCl2-) anyway. 87.102.114.166 (talk) 14:10, 2 June 2010 (UTC)

drug interaction checking

I perhaps did not make myself clear in a previous question regarding Phenylephrine, which is given to dilate pupils and has the side effect of restricting blood vessels and Simvastatin, which is given to reduce high Cholesterol which is the intended effect. Although there is no direct interaction between Phenylephrine and Simvastatin for a drug interaction checker to find it does not appear that any drug interaction checker will also look for the combination of blood vessel restriction from high Cholesterol and from the side effect of Phenylephrine which could be deadly. Is there a program or method which checks for these types of deadly interactions since drug interaction checkers appears to ignore such interactions? 71.100.0.241 (talk) 13:11, 2 June 2010 (UTC)

Why do you believe that they don't check for such interactions? 75.41.110.200 (talk) 15:12, 2 June 2010 (UTC)

Because I can find all sorts of drug interaction and WHR and BMI warning check sites on the Internet but not any that warn of this problem. 71.100.0.241 (talk) 16:49, 2 June 2010 (UTC)

Standard checks for phenylephrine show up various warnings and cautions for people with clogged veins etc [10] [11] [12] 87.102.114.166 (talk) 17:39, 2 June 2010 (UTC)

What makes you think that this is a problem? I mean, there could be drug-drug interactions between any combination of medicines, but why would you think that a "drug interaction checker" would look for a combination of phenylephrine and high cholesterol? It just doesn't make sense. We normally associate high cholesterol with atherosclerosis, which typically affects large blood vessels and is associated with acute blockages due to thrombosis. The mechanism of phenylephrine is completely different, as it acts primarily to constrict small blood vessels in the periphery. Can you cite any evidence to suggest that the combination of phenylephrine and "blood vessel restriction from high cholesterol" could be "deadly"? Perhaps the reason that the drug interaction checkers ignore this is that it doesn't exist? If this is something that you are truly concerned about, you need to ask your doctor about it. --- Medical geneticist (talk) 22:50, 2 June 2010 (UTC)

Remote sensing and GIS

1.Write the short notes in image enhancement techniques based on the followings;-

a)Constract stretch.

b)Image filtering.

c)Colour composing.

d)Vegitation index.

2.Write the short notes on digital image classification;-

a)Minimum distance classifier.

b)Box/parallelopipe classifier.

c)Maximum Lixelihood classifier. —Preceding unsigned comment added by Kamtwanje,Hussein George (talk • contribs) 16:01, 2 June 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.--Tagishsimon (talk) 16:04, 2 June 2010 (UTC)

Remote sensing and GIS might help. Pfly (talk) 16:04, 3 June 2010 (UTC)

History of Science: What did Islamic Science invent or discover?

Does anyone on Wikipedia, have a list of scientific discoveries that can be directly attributed to scientific researchers working in the Islamic world?

Sfan00 IMG (talk) 16:20, 2 June 2010 (UTC)

We have a very extensive article on that topic, inventions in medieval Islam. Looie496 (talk) 16:24, 2 June 2010 (UTC)

Also Timeline of science and engineering in the Islamic world for other periods.87.102.114.166 (talk) 16:45, 2 June 2010 (UTC)

Thanks, Both articles seem to have an extensive set of further sources as well :) Sfan00 IMG (talk) 17:06, 2 June 2010 (UTC)

Hmm, Reading that led me to a question on a tangent... Could the Islamic World have developed a self-contained powered vehicle before the Industrial Revolution in Western Europe? Sfan00 IMG (talk) 21:37, 2 June 2010 (UTC)

Hero invented a cart that moved around by itself, the path could be programmed by winding a string round pegs on a barrel. Dmcq (talk) 21:59, 2 June 2010 (UTC)

Shame it wasn't a 'turtle'.  ;) XD Sfan00 IMG (talk) 22:32, 2 June 2010 (UTC)

I assume this was Hero of Alexandria.

It's possible but not quite there..

• A steam engine - probably not able to make a boiler that withstood the pressures, and more importantly make pistons to the correct accuracy - but maybe they could have if they'd tried. Similar problem with internal combustion
• Electrical - this seems more likely - they almost certainly had the battery - I assume the knew about magnets - however I don't thing they had made the connection between electricity and magnetism necessary to - make big magnets, and make motors.

I'd be fascinated to be proved wrong.

Are there any other forms of propulsion.87.102.114.166 (talk) 22:18, 2 June 2010 (UTC)

I'm not entirly sure an Arab steam engine is as implausible as you suggest, given that 'distillation' was a chemistry technique discovered in the Arab world (and would thus have needed appropriate vessels).

The articles linked also note that there were automata that ran on steam so...

I'm not saying that the self propelled vehicle has to be 'useful' .. Sfan00 IMG (talk) 22:33, 2 June 2010 (UTC) Other forms of power... - Water... - Sand ... Clockwork mechanisms - Comments on the #wikipedia-en IRC suggested mechanical clockwork power needs a coil spring which would need a certain level of metalworking. That said, simple mechanical power storage like a twisted cord could be built on fairly simple technology...

Yes spring power - in medieval time they definately had the metal working skill to make steel suitable for springs - at least Damascus steel is getting near to a similar thing.83.100.183.63 (talk) 22:53, 2 June 2010 (UTC)

The thing here is that they didn't develop such a thing. Could they (hypothetically) have done? Well, no. After a burst of creativity and invention in the 9th to 12th centuries (roughly) - things pretty much shut down. Look at the list of inventions - hardly anything in the 15th century - pretty much nothing after that. What stopped them from inventing the car (or the bicycle for that matter) was what stopped them from progressing at all since then. What stopped them was largely societal - but that's every bit as much of a brake on progress as (say) inadequate understanding of mathematics stopped the Romans and lack of interest in experimentation stopped the Greeks. In the end, the only inventions that mattered in the western world was aggressive concentration on universal scientific education and the development of "The Scientific Method". SteveBaker (talk) 23:26, 2 June 2010 (UTC)

Whoa nelly, Steve! That's a bit of overt oversimplistic Eurocentricism, don't you think? The question of Enlightenment and Industrialization is extremely complex, and in the case of the former, it's to argue that the Hellenes or Islamic scholars were not as scientifically progressive during their prime as the Royal Society at their founding, say (especially since they didn't have the advantage of a bunch of infinite series and algebraic constructs already pre-written for them). Also, universal scientific education? Not until the mid-19th century. The Scientific Method? Not until the mid-19th century. At least, not in a more advanced state than aforementioned scholars. SamuelRiv (talk) 02:19, 3 June 2010 (UTC)

Not Eurocentricism so much as counting the number of entries in Timeline of science and engineering in the Islamic world for each century. You can do that for yourself - and I'm sure you'll come to the same conclusion that I did. If you look deeper, the situation is even worse than that. So many of the recent entries are the obscure and not-earth-shattering work of a single guy who either works in the west or was trained in western universities. Several of the 21st century breakthroughs are incredibly trivial inventions (a non-glare headlamp and an automatically raising ladder for chrissakes!) - these hardly rate up there with decoding the human genome, building the Internet, writing Wikipedia, flying to the moon, and other modern inventions. I know this sounds terribly non-politically-correct, but just read what the article says...it's undeniable. SteveBaker (talk) 15:06, 3 June 2010 (UTC)

The scientific method was adopted since the Scientific Revolution. Certainly by the 19th century, the accepted way of doing science was by experiment, not by endless philosophizing or appealing to religion. --Bowlhover (talk) 07:04, 3 June 2010 (UTC)

I just noticed the 16th C Taqi_al-Din_Muhammad_ibn_Ma'ruf#The_Sublime_Methods_of_Spiritual_Machines a description of a turbine and a reciprocating engine. I still haven't found evidence that they would have been able to make suitable high pressure cylinders or pistons though.. I think a key technology here is the Lathe for metalworking but I can't find much about this aspect (they had lathes for lenses though) 83.100.183.63 (talk) 11:34, 3 June 2010 (UTC)

One of the biggest issues for the slowdown was that while a lot of the basic science was developed by the end of the 16th Century actually exploiting it to make significant further developments needed an increasingly industrial economy. That required access to suitable raw materials in significant volumes and access to significant workforce.

That didn't really start to kick in until the late 17th Century in Europe. The basic science was essential to the industrial revolution, but building on the basic science wasn't really an option in North Africa and Persia.

ALR (talk) 15:57, 3 June 2010 (UTC)

The Industrial Revolution article does list theories for why it occurred where and when it did. Most of the sociocultural arguments I believe are bunk (Christianity encouraging belief in rational laws?). The most convincing argument I have seen, in contrast to what ALR says above, is in comparative popular history, which set a standard of per-capita income. In all major advanced societies - Rome, the Ottomans, Tang China, and possibly others depending on the analysis - while productivity and scientific advancement were enormous, there were essentially too many poor people providing too much cheap labor to make machinery a worthwhile investment as it was in 1800 England.

Bowlhover-"the accepted way of doing science was by experiment, not by endless philosophizing or appealing to religion" - tell that to Ptolemy or Archimedes or Galileo or Boyle, if we only want to stay in the Western Hemisphere. Conversely, tell it to Faraday or the anti-positivist Maxwell. SamuelRiv (talk) 16:00, 3 June 2010 (UTC)

Hmmm ? Maybe I misunderstand your point, but Galileo Galilei, Robert Boyle and Michael Faraday are well known as experimentalists. Gandalf61 (talk) 08:57, 4 June 2010 (UTC)

See also Al-Jazari#Mechanisms and methods.Email4mobile (talk) 15:12, 6 June 2010 (UTC)

And Taqi_al-Din_Muhammad_ibn_Ma'ruf#Mechanical_treatises section which describes his invention of an early practical steam turbine.--Email4mobile (talk) 15:42, 6 June 2010 (UTC)

Same thing that Hero of Alexandria did in the 1st century BC. (I wonder if this might have been a case of patent infringement?) 67.170.215.166 (talk) 00:42, 7 June 2010 (UTC)

The patent would have probably expired by then. Googlemeister (talk) 14:07, 7 June 2010 (UTC)

density of liquid mixture

i would like to know how do we calculate the density of liquid mixture.for eg how do i calculate density of 40 % ethanol v/v?we know the density of absolute ethanol and that of water but how do we apply this knowledge to calculate density of the mixture?please guide. —Preceding unsigned comment added by 180.149.53.9 (talk) 19:40, 2 June 2010 (UTC)

It's not easy or impossible - you can estimate the density by averaging the densities of the components eg for 40%v/v ethanol water the density would be estimated to be 0.40 x density ethanol + 0.60 x density water.

The actual figure may be different due to the way different shaped molecules fit together as well as short range bonding interactions that differ between different types of molecule, and other factors.

In fact the estimate will be pretty close for most mixtures. Only rarely do significant deviations occur.87.102.114.166 (talk) 20:04, 2 June 2010 (UTC)

Actually ethonol is miscible with water, so mixing 1 liter of 100% ethonol with 1 liter of 100% water will not give you 2 liters of liquid. Googlemeister (talk) 20:08, 2 June 2010 (UTC)

It's separate from miscibility...the question (and solutions (sorry:) ) offered apply for any ratio that does give a solution, even if the components are not soluble at other/all concentrations (miscible). DMacks (talk) 20:12, 2 June 2010 (UTC)

The gory math for "actual" (non-"ideal") liquids is in our volume of mixing article--the intro/definition gives a nice qualitative overview (and specific example for ethanol/water) and then quickly gets to illustrating just now "not easy" the real situation is. DMacks (talk) 20:09, 2 June 2010 (UTC)

The deviation from simple "sum of parts" is noticeable enough for ethanol/water that there are official tables for converting measured density of such mixtures into their component ratio--wouldn't need that if it were directly additive because could just solve the linear combination I guess? DMacks (talk) 20:20, 2 June 2010 (UTC)

(EC with all above) For this example you would take the average of 4 parts ethanol and 6 parts water (since that is what it is composed of. The density of water is 1 g/cm³ and ethanol is 0.789 g/cm³. It would come out to (1 g/cm³·6) + (0.789 g/cm³·4) = 9.156 ÷ 10 = 0.9156 g/cm³ --Chemicalinterest (talk) 20:12, 2 June 2010 (UTC)

87's formula is much easier. --Chemicalinterest (talk) 20:14, 2 June 2010 (UTC)

plumbers putty

i have black plumbers putty sealing my bathroom sink. my sink handle was creaking so i sprayed some pam on it. the next day the pam appeared to eat away the plumbers putty and turn it brown. how is this possible? --Alexsmith44 (talk) 19:53, 2 June 2010 (UTC)

What's 'pam' did you mean PAM (cooking oil) ? If so the oil in 'pam' will have diluted/dissolved the linseed oil in the Plumber's Mait

eg as an experiment add oil (any) to putty - you'll see that it gets thinner and more runny the more you add.

Is a 'sink handle' a Tap (valve) ? 87.102.114.166 (talk) 20:08, 2 June 2010 (UTC)

yes i mean PAM (cooking oil). even if the pam dilutes the linsead oil why does it turn brown? and how does it eat away at it if the outer layer is hard? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 22:04, 2 June 2010 (UTC)

yes - putty goes hard over time - it may be evaporation, though it may also be polymerisation of the linseed oil - nevertheless hard things can be softened by things that dissolve them.

As for the brown colour - it was black before? Maybe the spray is diluting or washing away the pigment (v dark brown = black). It's difficult to say when I can't see it.

Have you got any spare putty - if so put a little in some oil and see what happens - it's possible that the colour in it will leach out (like dyes running from clothes in the wash). There still might be another explanation.

If you get stuck here you could as a last resort contact the manufacturer of the putty - they might even be interested that the colour is fading if its a flaw in their product.87.102.114.166 (talk) 22:10, 2 June 2010 (UTC)

BTW, once installed you shouldn't really be able to see the putty anymore. Its job is to sit between surfaces, not on top of them. The putty that is on top can be removed. Ariel. (talk) 00:28, 3 June 2010 (UTC)

i dont have any spare puddy i didnt install it. i used to use peanut oil to lubricate it and it didnt ruin the puddy. why did the pam they are both oils? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 00:40, 3 June 2010 (UTC)

I don't know about the particular product you used, but a number of spray oils contain lecithin as a significant component. Unlike the triglycerides in "regular" oil, lecithin acts as a surfactant/emulsifier, and as such may act differently in solubilizing/leaching compounds. -- 174.24.200.38 (talk) 03:54, 3 June 2010 (UTC)

so what should i use to lubricate it  ? it needs to be a aerosol

Trigonal Bipyramidal Molecular Geometry

Hello. How was the trigonal bipyramid derived as the shape that allows bonding electrons stay as far from each other as possible? The bond angles in tetrahedral molecules equal. Why can't trigonal bipyramids? Thanks in advance. --Mayfare (talk) 21:35, 2 June 2010 (UTC)

Note that the square antiprism is also a minimum energy configuration even though a cube would give all the angles equal. You can't arrange 5 points evenly into a regular polyhedron Dmcq (talk) 21:48, 2 June 2010 (UTC)

how was it derived.. basically by adding an extra 'arm' to the tetrahedron, or arms to the flat triangular arrangement, and then fiddling to get the least variance in distane between arms.

or from knowledge of the various three dimensional polyhedrons (most simple ones were known early in human history) - and selecting from those that had five vertices.83.100.183.63 (talk) 22:42, 2 June 2010 (UTC)

What these guys are getting at is that the shape taken is the one that minimizes the energy associated with electrostatic repulsion. For some numbers of electron pairs, like 2,3,4, and 6, the minimum energy configuration is indeed one that gives equal bond angles. In the case of 5 and 7, there are no possible ways to arrange the electrons to give equal bond angles, and instead you get a trigonal bipyramid and Pentagonal bipyramid molecular geometry, respectively. If you don't believe that there are no ways to arrange 5 or 7 bonds around a central atom that gives equal bond angles, try it yourself. As to how it was discovered that these types of molecules like Phosphorus pentachloride take this geometry, I don't know. It could have been theoretically deduced to be the lowest energy configuration (and then actually measured somehow), or the geometry may have been deduced for individual molecules, and then generalized in VSEPR theory. There's not much history that I could find. As Dmcq points out, when you get to the case of 8 bonds around an atom (very rare), there is a way for those bonds to have constant bond angles; the bonds could lie at the corner of a cube. However, that's not the least energy configuration. So it's not true, in general, that a configuration that gives constant bond angles is necessarily the configuration that a molecule actually attains. Buddy431 (talk) 22:55, 2 June 2010 (UTC)

What are we seeing when we look at the sun?

Well we all know that the sun is mostly hydrogen. But hydrogen is invisible, and when hydrogen burns, it burns invisible too I believe. So what exactly are we looking at when we look at the sun? ScienceApe (talk) 22:24, 2 June 2010 (UTC)

You're looking at the light emitted from the sun.83.100.183.63 (talk) 22:30, 2 June 2010 (UTC)

(ec) Conventional wisdom says that it emits light because it is hot - white hot in fact (in the same way a Incandescent light bulb emits light because it is hot).83.100.183.63 (talk) 22:37, 2 June 2010 (UTC)

Thermal Radiation, essentially. Anything with a temperature above absolute zero "glows". That is, it releases electromagnetic radiation at a variety of wavelengths dependent on how hot it is. Humans glow mostly in the Infrared range. The sun glows across a wide range of wavelengths, including Visible light. Buddy431 (talk) 22:36, 2 June 2010 (UTC)

I was going to suggest Blackbody radiation but that just redirects to the already linked thermal radiation article.. Vespine (talk) 23:03, 2 June 2010 (UTC)

Hydrogen burns in oxygen with a colorless flame - but what's happening in the sun is nothing to do with 'burning' - that's a confusing term! The hydrogen is participating in fusion reaction where two atoms of hydrogen are crushed together to make a helium atom and producing a heck of a lot of heat and light in the process. The color of sunlight corresponds to Black body radiation at 5800 degC - which is the surface temperature of the sun. You'll need to read the black body article to understand the precise reason for that. The color (if you were out in space) would be almost perfectly white - it only looks yellowish here on earth because so much of the blue light is scattered out there into the sky (white minus blue equals yellow!). SteveBaker (talk) 23:13, 2 June 2010 (UTC)

Strictly speaking, 4 hydrogen atoms create one helium atom, in the Proton-proton chain reaction (mostly) in the sun. Buddy431 (talk) 23:30, 2 June 2010 (UTC)

Neatpicks!!

• The use of the word burn to describe the nuclear reaction that happens in the sun is pretty well stablished language.
• To say that the sun "is almost perfectly white" is a pretty subjective thing to say. It looks pretty white to me even after its light's been filtered by the atmosphere.

Dauto (talk) 01:58, 3 June 2010 (UTC)

I'm still a little confused about the "color of the Sun" thing. I tend to think the main reason we think of the Sun as yellow is that that's the color when it's low on the horizon, but not quite low enough that we'd call it sunset (when it's orange-red). When it's higher in the sky, it's painful to look at and we usually don't.

But when you see the disk of the Sun through a thin layer of cloud, it appears pure white. So the question is, does the cloud layer change the perception of color, or does it just reduce the intensity enough to look at?

On the other hand, I do have the sense that sunlight on objects appears yellowish. But I can't quite figure out what that even means. --Trovatore (talk) 07:25, 3 June 2010 (UTC)

Trovatore, our perception of color is as much a consequence of our eyes and brains phisiology as it is a consequence of the spectrum of the light itself. The eyes and brain do extensive processing that allow us to have a fairly consistent color perception regardless of the king of light used to shine on the object. Because of that the question of whether the sun is white or yellowish is more or less a meaningless question. From a purely spectroscopic point of view the sun is actually greenish, but we don't see that. To answer your question, light that goes through a thick atmospheric layer becomes yellowish -> orangish -> redish while light that goes through a cloud layer doesn't, simply becoming dimmer. Dauto (talk) 15:13, 3 June 2010 (UTC)

• Sure it's established language, but the original poster spoke of how hydrogen "burns invisible I believe", and that's about combustion with oxygen, not fusion. When the question shows signs of confusing two concepts, it's necessary to distinguish them. --Anonymous, 04:36 UTC, June 3, 2010.

Of course we should clarify any confusion or misconception that the OP might have, but we should nopt tell them not to use the word 'burn' when that's exactly the word used by the specialists in the field. Dauto (talk) 15:00, 3 June 2010 (UTC)

We're seeing photons that were created eight minutes ago. When hydrogen atoms fuse into helium, that resulting helium has slightly less mass than the hydrogen did. From E=MC-squared, you can see that the tiny loss of mass (M) turns into a relatively huge amount of energy. That energy is released as photons, an infinitesimal percentage of which reach our eyes (I may have the following wrong: I believe one-third of the photons are "visible," and the other two-thirds are invisible gamma rays). Incidentally, the CNO cycle may be a second type of solar fusion, and it also releases photons. 63.17.89.8 (talk) 02:13, 3 June 2010 (UTC).

The CNO cycle is a different set of reactions that has the same net effect as the p-p reactions - That is the conversion of hydrogen into helium. Dauto (talk) 02:46, 3 June 2010 (UTC)

The photons created by nuclear fusion in the Sun are reabsorbed. The light we see comes from the surface of the Sun and is blackbody radiation, as already mentioned. Possibly you're thinking of neutrinos, ~2/3 of which are invisible to certain detectors in a formerly mysterious way (the solar neutrino problem). -- BenRG (talk) 09:28, 3 June 2010 (UTC)

What about this though? What am I looking at in this picture? Looks like a surface of lava (I know it's not, just saying it looks like that. What is all that red and orange stuff I'm seeing? ScienceApe (talk) 00:41, 4 June 2010 (UTC)

Is it really eight minutes ago though? From Sun: "The gamma rays (high-energy photons) released in fusion reactions are absorbed in only a few millimeters of solar plasma and then re-emitted again in random direction (and at slightly lower energy)—so it takes a long time for radiation to reach the Sun's surface. Estimates of the "photon travel time" range between 10,000 and 170,000 years.[42]" How many of the photons reaching the earth travelled from the core to the photosphere and then to Earth and how many are the result of black body radiation? --Rajah (talk) 22:23, 7 June 2010 (UTC)

Same exact deal...black body radiation. Lava is at between 700 and 1200 degrees C (1000 to 1500K), and if you check the black body diagram on the left here, you'll see that that's in the red/orange range. The sun, at around 6000K is in the white region. The color at which most hot objects glow is directly related to their temperature. SteveBaker (talk) 01:32, 4 June 2010 (UTC)

That's not lava... it's a solar flare! The red and orange stuff is probably thermal radiation from hot plasma (that is, emitting visible light just like the rest of the sun does). Note that solar flares are much hotter than the surface of the sun, so can spit out a lot of radiation for their size. Also realize that electromagnetic radiation can be generated in other ways besides thermal radiation; when you accelerate matter (especially charged particles) to relativistic speeds (as occurs in solar flares), photons can be emitted then too (I don't really understand the mechanism there). This is what's believed to cause Gamma-ray bursts, for example. Buddy431 (talk) 01:45, 4 June 2010 (UTC)

But when I look at that photo, I'm not just seeing photons, I'm seeing matter aren't I? I think it's plasma if I'm not mistaken, so would it be hydrogen plasma? So I guess my question is, is hydrogen visible to the naked eye when it becomes a plasma? ScienceApe (talk) 04:11, 4 June 2010 (UTC)

Yes it is the pink colours are relatively mild plasmas generated electrically in general all plasmas Plasma (physics) emit light because of the high energy they are in.83.100.183.63 (talk) 13:50, 4 June 2010 (UTC)

Sure, you're seeing photons. That's what light is. The hot hydrogen plasma (or the lava, or even your pet cat) radiates photons over a range of frequencies (colors) with a peak frequency that depends on the temperature. At the temperature of your cat, those are in the infra-red range, in the case of the lava, it's in the red/orange range - and in the case of the sun, it's pretty much white. Those photons travel outwards in all directions and some of them arrive inside your eyeball where they are absorbed by chemicals in the rod and cone cells in your eye. Hence the perception of "color".

But that's not the whole picture - your cat doesn't look black (well, unless it's a black cat!). That's because objects also reflect light - so all of those photons coming from the sun hit your cat, some of them are absorbed and the rest reflected...and again, some of the reflected ones hit your eye. So the color of the light arriving at your eye when you look at things is a combination of the light they emit and the light they reflect (and for translucent objects, the light that passes through them).

In the case of really hot things like lava and the sun's surface, almost all of the light is emitted - so the color you see depends on the emitted light spectrum - which (for most things) follows that black body radiation curve. For much cooler objects, that radiation is largely in the infrared and you can't see it because your eyes aren't sensitive in that part of the spectrum - so the only light you see coming from your cat is the reflected light. There is also reflected light coming from the sun - but there is so very little starlight reflected from the sun that all you really see is the emitted light.

If you take a chunk of iron and gradually heat it up, it starts off at room temperature, looking slivery/grey because it's reflecting light and emitting in the far infrared where you can't see it...but as it heats up, it passes the Draper point (about 525 degC) - that emitted light starts to climb in frequency and edge into the red end of the visible spectrum. What we see is that the metal starts to glow red - it's still reflecting light but the relatively tiny amount that it reflects is now dwarfed by the amount it's emitting. As the metal gets hotter, it glows orange (now it's about 1000 degrees - as hot as lava - and roughly the same color), then yellow, then eventually white. "White hot" means "about as hot as the surface of the sun" - and you have to get your metal up to about 5000 degrees to do that. SteveBaker (talk) 14:11, 4 June 2010 (UTC)

Contents of Organic Pesticide

I just used an organic pesticide that contains the potassium salt of various fatty acids as its main ingredient. Will this actually kill/repel/do something to insect pests or did I just waste my money on some oily, salty water?24.88.87.41 (talk) 22:41, 2 June 2010 (UTC)

Maybe somebody else can give you a better answer, but the way to test for it is to spray some plants with this, and leave others of the same type alone. See how they stack up. Falconus^{p t c} 22:49, 2 June 2010 (UTC)

There's an explanation of how they are supposed to work here [13] It looks like they affect the cell wall of things - also works on plants [14] There's plenty of hits on http://www.google.co.uk/search?q=fatty+acid+pesticide&hl=en&start=10&sa=N - so I'd think there must be something in it ??

For aphid on apple trees I think a common treatment is to spray soap on the trees - probably does work, or at least people think so [15] /83.100.183.63 (talk) 22:50, 2 June 2010 (UTC)

This could be just what I've "heard" but i always thought there was nothing wrong with organic pesticide, efficacy wise, you just need to spray more of it and more often for it to be as effective as the non organic counterpart. That's probably just what the planet rapists want us to believe. Vespine (talk) 23:01, 2 June 2010 (UTC)

Sure if you spray enough of many things you'd kill the pest. One of the ways would be by killing the plant or failing that any organisms thats eat even a tiny bit of it. Nil Einne (talk) 00:53, 3 June 2010 (UTC)

Trouble is with "nothing wrong efficacity-wise if you just spray more" is that that costs money. Fine, if like me you're growing a couple of dozen Broad bean plants in your back garden. So over the growing season you have to buy a couple or three bottles of fatty acid pesticide at £1.49 instead of one bottle of something non-organic (if as an amateur you could get it) at £1.00. No big deal. However if you have 100 acres of beans, and you're trying to make a living out of them rather than playing at farming (like me) the financial picture's rather different. Tonywalton ^Talk 01:05, 3 June 2010 (UTC)

There's a good amount about them on Google - just search for /fatty acid pesticide/ and similar terms. Here's one example of many. Yes, they do work OR: I have an unholy glee in spraying a fatty acid pesticide on my roses and watching the greenfly die, although you may need to use more, or apply more often, than, say an organophosphate or pyrethrin. You don't say what you're trying to kill on what crop, but personally I'd much rather get rid of aphids on my broad beans with something rather less poisonous to humans than some insecticides. Of course you could always try Enviromesh instead, if you want to avoid being called a "planet rapist". The mesh stuff also keeps pigeons off, which is a definite plus! Tonywalton ^Talk 00:52, 3 June 2010 (UTC)

We have an article on Insecticidal soap: "Insecticidal soaps are used against soft bodied insects and mites ... Insecticidal soaps have been about 40-50% effective against these pests." -- 174.24.200.38 (talk) 03:49, 3 June 2010 (UTC)

I probably should have qualified the sarcasm of my planet rapist comment, i don't really believe that, i think "organic" farming is far more of a scam then conventional farming. Vespine (talk) 03:51, 3 June 2010 (UTC)

Yes I thought you were being sarcastic but wasn't sure Nil Einne (talk) 05:59, 3 June 2010 (UTC)

June 3

Propagation of bloodline

From Malaria:

Endogamy along caste and ethnic lines appear to have confined these to the Tharu community. Otherwise these genes probably would have become nearly universal in South Asia and beyond because of their considerable survival value and the apparent lack of negative effects comparable to Sickle Cell Anemia.

Do we have an article about this? I'm interested.. say that 100 Chinese people marry into the United States, and no more chinese people after that are allowed in. After hundreds of generations, in the absence of any particular traits that give Chinese people a genetic advantage, will the percentage of Americans who "have Chinese blood" from the original 100 people increase to near 100% or decrease to near 0% over a long period of time? .froth. (talk) 00:14, 3 June 2010 (UTC)

Assuming random intermarriage, the average fraction of the genome that comes from the Chinese immigrants would stay roughly the same (except for random fluctuation), but it would become more and more widely dispersed. So the fraction of people who "have Chinese blood" would steadily increase, but their average proportions of "Chinese blood" would correspondingly decrease. Looie496 (talk) 01:36, 3 June 2010 (UTC)

Genetic drift might be of interest.--Lenticel ^(talk) 01:59, 3 June 2010 (UTC)

Specifically, the section on fixation. At such a low introduction frequency (100 foreigners into a population of 300,000,000), the alleles that are distinctly Chinese will be inevitably lost, given enough time, as a consequence of random fluctuation. Basically, this is because the frequency will fluctuate over time, and if it ever reaches 0, it will never change from that; and because of the low introduction frequency, it is highly unlikely to reach 1, from which it would also never change. Someguy1221 (talk) 05:48, 3 June 2010 (UTC)

I really can't see how a resistance to malaria wouldn't have spread throughout Asia in a few thousand years no matter how strong their rules are against marrying outside. There must be something else in it which is a disadvantage which we don't know of yet. Dmcq (talk) 15:07, 3 June 2010 (UTC)

If the female in a marriage is of a specific ethnicity, then her mt-DNA will be passed down to all her offspring, but there is as much variation in this within an ethnicity as there is between two different ethnicities. ~AH1^(TCU) 23:22, 3 June 2010 (UTC)

That's just because of the meaninglessness of the concept of "ethnicity" from a biological point of view. What does any of that have to do with this? What makes you think the relevant gene(s) is mitochondrial? --Tango (talk) 23:50, 3 June 2010 (UTC)

Chemical solution for producing infrared liquid.

Hello I have a problem. I ve made the chemical solution that produces infrared light, but only lasts for 5 mins when not in a airtight container. I need to find out, how can i make it last for a few hrs in an open aircontainer. Thanks for your time, I am eagerly awaiting your answer.If you could be kind enough to e-mail it to me on (email removed) I will be gratefull to you. Thanks. Amit —Preceding unsigned comment added by 118.90.116.113 (talk) 01:15, 3 June 2010 (UTC)

I'm sorry, but the reference desk does not provide responses via email. You'll also need to provide a lot more detail about what this solution is for us to try to answer your question. Someguy1221 (talk) 05:44, 3 June 2010 (UTC)

(EC)I do not think your question is specific enough to be answered as you've stated it. I doubt there is a generic way to increase the length of an unspecified substance's IR light production in an unsealed container. Maybe if you give us specifically what your substances are and what the reaction is that produces the light, we might have a better chance. I'm not a chemist but at a guess, your reaction is oxidizing, either accelerating or otherwise interfering with the reaction, I'm not sure there is much that can be done short of inhibiting the oxygen availability by sealing the container or flooding it with an intert gas like argon or something. Then you'll of course have to worry about what argon will do to your reaction. Vespine (talk) 05:51, 3 June 2010 (UTC)

This seems kinda basic. "the chemical solution that produces infrared light" could be a bucket of hot water. Anything that's hot (or even just warm) radiates in the infra-red...you don't need some special "chemical". The thing is probably going to stop producing IR because it's cooling down more in an open container. Just stick a heating element in the bottom of a large container of water and stop it from boiling - and it'll radiate in the IR for as long as you keep the thing plugged in! If you need more IR light than that, pick something with a higher boiling point and heat it up more. SteveBaker (talk) 14:43, 3 June 2010 (UTC)

Not a chemist, but I'd also suggest that you might be looking for something that can only reflect infrared light when exposed to only red/infrared light and not normal white light, which has a very different emission curve. Remember that reflected light is an absorption-reemission phenomenon that will depend very much on the energy of light coming in. Also, as an alternative to Steve, any kind of algae or plant life is a great emitter of infrared (aerial surveys usually use infrared cameras to quickly distinguish plant life, especially useful over water). SamuelRiv (talk) 16:07, 3 June 2010 (UTC)

You have an interesting definition of "warm" - according to my calculations, anything above 10K will have a peak thermal radiation in the IR (or higher), and that's just the peak so even things colder will emit a significant amount of IR. --Tango (talk) 21:40, 3 June 2010 (UTC)

I imagine we're talking about IR emissions observable over the background, so i doubt the OP was talking about a warm bucket of water.. I could be wrong, but that's the way i interpreted it. Vespine (talk) 03:54, 4 June 2010 (UTC)

Actually, I'd love to see what the OP had put together as his solution, and maybe I can play around with some quantum mechanics calculations to see if I can get some idea (though it has a 99% chance of being completely fruitless). Beyond that I'm completely lacking in chemistry knowledge, though I know there's plenty of literature on UV-peak solutions - maybe you can do it all backwards :). SamuelRiv (talk) 05:06, 4 June 2010 (UTC)

Cooking oil contamination?

I have a large frying pan and cook raw chicken thighs/legs for about 45/50 minutes on a low/medium setting-the oil bubbles and seems to reach high temperature for long periods. But I change the oil once a week. Bearing in mind carbonised residue build up at the bottom of the pan, could bacteria build up even in boiling oil, and how often should it be changed? The food is for my own consumption, not anyone else. —Preceding unsigned comment added by 80.1.80.13 (talk) 07:27, 3 June 2010 (UTC)

According to our cooking oil article, you should be more concerned about degradation of the oil due to exposure to air and light. Bacteria could develop in the oil when stored in the pan, and our article especially mention the risk of botulism. However, the botulism article also states that a long cooking period breaks down the botulism toxin. For more information it would probably be a good idea to look up guidelines and routines specific to restaurant and take-away kitchens.

As a side note, bacteria and fungi in general are killed by boiling, but the poisons they leave behind could survive. I seem to recall this is a problem with some yeast/fungi. EverGreg (talk) 09:33, 3 June 2010 (UTC)

"45/50 minutes" - you like your chicken well done then. What sort of oil is it, because different oils boil at different temperatures. 86.4.183.90 (talk) 18:00, 3 June 2010 (UTC)

Cooking oils don't boil at all, they break down first. There is no chance of bacterial buildup in oil that is used daily or almost-daily to fry chicken. The main reason you will want to change the oil is because stuff will leak out of the chicken and start to break down, causing it to taste gradually more nasty. Your oil will also contain steadily larger fractions of chicken fat, which is exuded by thighs and legs in large quantities when you cook them that way. Looie496 (talk) 23:07, 3 June 2010 (UTC)

...And let me add that I can hardly imagine a more unhealthy diet than eating chicken cooked that way multiple times per week. Looie496 (talk) 00:57, 4 June 2010 (UTC)

Come now, you can't being trying very hard. A diet made up of 50 Mars bars a day would surely be worse, especially if some of them were deep-fried. Or nothing but rabbits. Or, indeed, nothing but carrots. There are many more unhealthy diets that I can easily imagine, and we don't know why the OP feels the need to eat the way they do. 86.164.69.239 (talk) 20:05, 4 June 2010 (UTC)

Don't quibble - the diet indicated by the OP is still likely to shorten their life by decades, compared to an optimum healthy diet. In addition to the fat and saturated fat, high-temperature cooking creates nasty unhealthy chemicals that I do not know the details of to describe. Re-using frying oil or fat is I believe particularly bad for creating carcinogens. As I never fry food, I do not know enough to describe the details. 92.15.3.53 (talk) 10:16, 5 June 2010 (UTC)

There's a restaurant whose fryer hasn't been completely-emptied/filled-with-new-oil since 1912.[16] DMacks (talk) 20:21, 4 June 2010 (UTC)

Water boiling question

Firstly the actual question: "At what temperature does water boil, and how could this be confirmed experimentally?" (I'm posting this in response to some disscussions elsewhere on wiki :) )

A simplistic answer to the question might be: " Water boils at 100 degrees C. To confirm this heat some water in a kettle and measure the temperature of the steam produced."

However, there are a number of flaws and pitfalls within that answer, I can think of 3 already. :) Sfan00 IMG (talk) 14:04, 3 June 2010 (UTC)

I'm not a chemist, but if I remember my high school chemistry this assumes standard pressure. You would need a phase diagram to correctly answer this question. --Shirik (Questions or Comments?) 14:09, 3 June 2010 (UTC)

Don't you mean high school physics? Dauto (talk) 14:42, 3 June 2010 (UTC)

Well, in the UK at least, this is covered in secondary school chemistry. Vimescarrot (talk) 18:22, 3 June 2010 (UTC)

I suspect that this is in response to a previous question asked by this OP on the Ref Desk Wikipedia_talk:Reference_desk#Reference_Desk_Scope about how original research is handled at Wikiversity. The OP had suggested that doing an experiment to find the boiling point of water was a simple matter. I pointed out that there are a bunch of experimental mistakes you could make - even for such a simple question - that would mess up the answer. Hence if someone claimed to have done the experiment and gotten some value other than 100C, then I'd ask:

1. Did you measure the temperature when the bubbles just started to appear - because gasses come out of solution before boiling point.
2. Were you doing this at sea level or at an elevation where the air pressure is lower?
3. Did you put the thermometer into the water as it was heating up - or just dunk it in quickly (thereby lowering the temperature of the water immediately around the thermometer)?
4. How long did you wait for the temperature to settle down?
5. Did you remove the thermometer from the water in order to read it? (Hint: Rookie mistake - seen it a million times!)
6. How pure was the water? Even if it was distilled water, could contaminants have gotten into it from the container or the thermometer?

I'm not sure what else is being asked here - but I believe that's the background to this question. SteveBaker (talk) 14:50, 3 June 2010 (UTC)

More questions for completeness's sake:

1. How did you heat the water? If it was a pot of water heated on a stove, there could be a significant temperature difference between the bottom and top of the water.
2. If you are measuring the steam and not the water, is there any condensation on the thermometer? The latent heat of condensing water could lower the temperature registering on the thermometer.

-RunningOnBrains^(talk) 20:45, 3 June 2010 (UTC)

Thanks Steve :) , This was indeed a question not only about the actual physics (for which I have a basic idea) but on scientific technique (and the pitfalls thereof)

Of the pitfalls I can think of, the one's Steve mentions do exist :), I was also considering...

• Given the phase diagram, it's maybe possible for 'vapour' to form before the water actually boils?

Meaning that the temperature read might be of the vapour cloud, not the steam...

• Although the simple answer states to measure the steam, it isn't more specfic, This is a consideration because (conjecture)

given how a typical 'cloud' of steam from a kettle disperses, you might get different readings depending on where in the cloud you measured, owing to variations in pressure?

• How is 'water' defined? Steve makes a valid point about impurities. A releated consideration if not using distilled water

would be the potential for substances in solution(?) or dissolved gas, (water being a solvent IIRC)

• The simplistic answer assumes a single measurement with a thermometer., but depending on the type of thermometer there

may be characteristics of the thermometor which affect the result obtained.

All considerations.

I suppose revised questions should be

' How do you determine the temperature at which pure water boils given identical inital conditions, in a repeatable manner?' ' What external factors would potentialy have an influence on the boiling point of 'water' ?'

which are slightly different question to those asked initially. Sfan00 IMG (talk) 15:17, 3 June 2010 (UTC)

And while we're being uber-picky, let's toss in:

• Did your ultra-pure water have the correct ratios, deuterium, tritium, O¹⁷ and O¹⁸ in it?

SteveBaker (talk) 13:47, 4 June 2010 (UTC)

It all depends on what level of precision you want. Just sticking a thermometer into boiling water will give you the correct answer to within a few degrees every time, I can assure you. If you want to get down to a few hundredths or thousandths of a degree you need to start eliminating unknowns: Heat everything equally (atmosphere and thermometer too!), use ultra-pure water (reverse osmosis works great supposedly), and use other methods to control your environment as much as you can. -RunningOnBrains^(talk) 20:45, 3 June 2010 (UTC)

Water is rather a very difficult one to measure, partly due to the very high latent heat, which means that one has to apply a high heat source to get a good boiling mixture - thus the reading in the water can be a bit higher than you expect - just try making jam, it will vary where you locate the thermometer in the pot. Another point is that thermometers are calibrated for a fixed dip - may be 76mm, may be total immersion - you need to get that correct. The ideal way is to measure a mixture of steam and boiling water far away from its initial heat source - and the only bit of kit I have ever used that works well is a "Gillespie Still" - the boiling water/steam mixture is carried up away from the heater to the thermometer. The accuracy is very good.  Ronhjones  ^(Talk) 20:33, 3 June 2010 (UTC)

Could you clarify what you mean by a Gillespie Still as they doesn't appear to be an article yet?

( although as an item of lab equipment it shows up in a number of scientfic links when looked for on Google..) Sfan00 IMG (talk) 22:16, 3 June 2010 (UTC)

IMHO the answer you're providing begs the question, 100 degrees Celsius is an arbitrary constant BY DEFINITION the boiling point of water. It is more correct to say that you get 100 C at the point when water boils, as opposed to water boils when you get 100 C. IMHO, to prove 100 C is actually the correct boiling point you have to NOT take it for granted, a more meaningful answer would be to prove that water boils at 387.15 K. Vespine (talk) 03:48, 4 June 2010 (UTC)

That's a very misleading statement - and our OP should ignore it. The tie between definition of a degree and the boiling point of water only holds under very specific circumstances. If you measure the boiling point of water at the top of Mount Everest, it'll be around 69 degC. We don't change the temperature represented by a degree centigrade when you're standing on the top of a mountain...so your assertion that the answer begs the question is quite untrue. You can meaningfully measure the boiling point of water and end up with an answer that isn't 100C...so "BY DEFINITION" doesn't hold here. It is also untrue that the definition of 100C is simply that of the boiling point of pure water at standard air pressure. That definition was changed in 1954 and again in 1967. These days, it's defined by the triple point of Vienna Standard Mean Ocean Water which is not just pure water, it has to have precisely the right mix of hydrogen and oxygen isotopes - so even ultra-purified water might have too much or too little deuterium or tritium in it or the wrong amounts of O¹⁷ and O¹⁸ to get precisely that 100C result. So, again, this fixed relationship concept is bogus. SteveBaker (talk) 13:47, 4 June 2010 (UTC)

Water doesn't boil at 387.15K (at least not at standard pressure) according to the relevant article..

Follow on question : ' How to define the boiling point of water in manner that allows it to be used as

a reliable calibration point?' Sfan00 IMG (talk) 11:41, 4 June 2010 (UTC)

Vienna Standard Mean Ocean Water has that explanation. SteveBaker (talk) 13:47, 4 June 2010 (UTC)

Yes you need a standard composition for the water, and you also need to measure the bp under specific conditions - the atmospheric pressure is one of the most significant factors affecting the boiling point of water. pressure/bp data here. For reliable accuracy you need to know how the bp will vary with impurities as well - so you know whether the error in experimental variables will affect the bp measurement significantly.87.102.32.39 (talk) 15:41, 4 June 2010 (UTC)

I'm considering bookmarking this thread, clear yet interesting discussions. :) Sfan00 IMG (talk) 16:22, 4 June 2010 (UTC)

Another thing you can do is to define (and/or measure) the bioling point of water as a function of different variables (such as pressure) - then when you measure the boiling point another day you can look up on a table (such as given above) - to find out what the temp. should be under those conditions - ie use a barometer as well.

if you bookmark this thread the URL will change in 2-5 days when it is archived. the actual URL will probably be http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2010_June_3#Water_boiling_question 87.102.32.39 (talk) 16:29, 4 June 2010 (UTC)

Weller soldering

Good Morning, My question refers to Soldering and Weller. I've learned that my relative is Mr.Harry A.Ungar who invented the Ungar soldering pencil, Ungar soldering system, Soldering toys etc.. This has become a genealogical search as well. It seems Harry Ungar left Hungary, either from the Slovakia or Austrian areas. I've learned Mr Ungar had a plant located at 1401 Redwood, California, There is little to no biographical information that I've found but dearly need to track him back to my Great grandfather and to find living relatives.

Mr.Ungar it seems had a government contract to make soldering pencils for WW2.

Merged with Karl Weller.

Ungar/Weller sold to Cooper.

Listed in the southern Ca business directory listings1958,1961

Sidney Ungar Donated to save the Hollywood Bowl.LA Times Aug 21, 1951

His Children may be : Sidney, Leon, and Ruth Ungar(Marks).

Toys Manufacturer Assoc LA Times Dec 21, 1950 pg 25 Sidney Ungar.

I beg you! with your wonderful resources, can you help to find biographical information from any sources /media. The genealogists have accepted my hundreds of dollars but claim they are stuck. Even the above information is my work not theirs. I really need to give my children some attention and stop wasting their time as I search W/O result. Thank you in advance. Perry Urany <email redacted> —Preceding unsigned comment added by Perrykesan (talk • contribs) 16:03, 3 June 2010 (UTC)

• I've reformatted your question slightly to avoid an ugly layout of boxes and removed your email address so you don't get spammed to death. Any answers will appear here - we don't email answers out. Exxolon (talk) 16:32, 3 June 2010 (UTC)
  • Both Ungar and Weller are very well respected companies in the soldering business, and I have been a proud owner of their products. At Google Book search the earliest ref I found to Harry A. Ungar was Boys Life, Nov 1936 page 40, where he advertised a "woodburning" kit using a little heated stylus much like a soldering pencil. (I remember getting a nice third degree burn from one at summer camp crafts). The soldering pencil as such shows up in Popular Mechanics, December 1944 page 144, for a 17 watt soldering pencil which reached full heat in 90 seconds. On page 6, his company was listed as the maker. An ad showing some models of the pencils was in Billboard Nov 24, 1945 page 96. At Google News Archive there were several stories about persons named "Harry Ungar" (including a manager of the Stewart Products Service Station in California) back to 1919 but no idea if they are the same one. The first certain one is a pay per view from the LA Times, Feb 1, 1953 about a new factory in Venice CA, where it said "Sidney D. Ungar" was company president. Edison (talk) 04:00, 4 June 2010 (UTC)

cold fusion

OK, suppose somebody invents cold fusion in order to make electricity. On an industrial scale, they take water, hydrolyse it to its constituents hydrogen and oxygen, and then fuse the hydrogen to form helium. In doing so, they save the world from global environment change. However, might this cause other separate problems? Wouldn't water run out eventually? If tonnes of helium and oxygen are released into the earth's atmosphere, wouldn't they become pollutants? Bobble hobble dobble (talk) 17:36, 3 June 2010 (UTC)

According to World energy resources and consumption: "In 2008, total worldwide energy consumption was 474 exajoules (474×10¹⁸ J)." If we use the proton-proton chain reaction as an example (there are lots of different fusion reactions - this is the one that dominates in the Sun), then we get 26.73 MeV for every 4 hydrogen nuclei being turned into helium (and some positrons and neutrinos and things, that we can ignore). Google says we need about 4x10³² hydrogen nuclei a year. That corresponds to about 6.6 million litres of water. The Earth has about 1,360,000,000 km³ of water. That's 1.36*10²¹ litres. So even with a massive increase in energy consumption, we still wouldn't use even a noticeable fraction of the water in the billions years or so the Earth will be habitable for. The 2x10^³² atoms of oxygen that would be released a year compares with about 4x10^⁴³ atoms of oxygen already there, so again it wouldn't be significant over the remaining habitable lifetime of the Earth. The 10^³² atoms of helium released corresponds to 4x10³⁹ atoms already there. So that would be significant over timescales of millions of years, but wouldn't be a problem since helium is a noble gas, so is very inert. Basically, the amount of energy released by the creation of each atom of helium is so great that you don't need to make many to meet our energy needs. --Tango (talk) 18:19, 3 June 2010 (UTC)

If there was a dirt-cheap form of energy, the first side-effects would be the collapse of the current energy infrastructure and those nations dependent on them, like Saudi Arabia. In the long term, cheap energy might lead to "bad behavior", such as heating outdoor areas, like beaches, with radiant heaters. We might eventually get to a point where global warming created by actual heaters and A/C would surpass that due to greenhouse gasses. Also note that while total water consumption isn't an issue, water levels in lakes near large populations might eventually decrease by a detectable level. StuRat (talk) 18:57, 3 June 2010 (UTC)

Simple answers: No, no, and no. Dauto (talk) 20:27, 3 June 2010 (UTC)

Release of molecular hydrogen into the atmosphere on a large scale could severely deplete the ozone layer [17]. It would depend on how much hydrogen you would need to create, and how leak-proof your systems are.-RunningOnBrains^(talk) 20:55, 3 June 2010 (UTC)

You could always collect the wast H2 for portable fuel needs. Googlemeister (talk) 21:04, 3 June 2010 (UTC)

The point is to transmute the hydrogen into helium. I don't think helium would have much effect on the atmosphere, being inert. APL (talk) 21:27, 3 June 2010 (UTC)

...and very light. Atmospheric helium evaporates into outer space pretty readily, is the reason the concentration is so low even though "so much" is being released terrestrially. DMacks (talk) 21:31, 3 June 2010 (UTC)

You can burn off any leaking hydrogen and turn it back into harmless water. --Tango (talk) 21:29, 3 June 2010 (UTC)

I remember hearing about an electronic device in Germany that uses water molecules to produce electricity, but the voltage is on the order of <1.0V. ~AH1^(TCU) 23:18, 3 June 2010 (UTC)

I believe the water just serves as a catalyst. The energy comes from something else in the fuel cell. Water is a very low energy state, so it is extremely difficult to get energy out of it (fusing the hydrogen is the only method I know, and the device you remember certainly doesn't do that). Of course, the media when the device was announced said it used water as a fuel, but the media were talking nonsense. --Tango (talk) 23:54, 3 June 2010 (UTC)

Would my voice start to sound squeaky with all that helium? Edison (talk) 03:58, 4 June 2010 (UTC)

No - the amount produced is utterly negligable. Of course hydrogen would also make your voice sound squeaky - but I strongly recommend that you DO NOT try that! SteveBaker (talk) 13:11, 4 June 2010 (UTC)

variations of h2o

It is my understanding that H2O can only be in three states: liquid (water), gas (steam) and solid (ice) and that regardless of the state the chemical configuration is the same. So, are there other states of H2O and does the formulation remain independent of the state? 69.77.185.91 (talk) 18:26, 3 June 2010 (UTC)

The chemical formula has to stay the same, otherwise it wouldn't be water any more. There are 15 known phases of ice (Ice#Phases). It can also exist as a supercritical fluid, which is sort of a another phase of matter and has properties in common with both liquids and gasses. --Tango (talk) 19:20, 3 June 2010 (UTC)

Is it possible to create water plasma? Googlemeister (talk) 19:40, 3 June 2010 (UTC)

In a plasma the atoms are ionised and do not form chemical bonds, so it wouldn't be water anymore. A supercritical fluid isn't technically a different phase since it can be reached without going through a phase transition. Dauto (talk) 20:26, 3 June 2010 (UTC)

That's why I said "sort of" - I didn't want to get into details. I guess the closest thing to a water plasma would be a mixture of oxygen and hydroxyl ions. --Tango (talk) 20:47, 3 June 2010 (UTC)

Water is a molecule with strange properties, for example one test showed water to have a chemical formula of H_1.5O even though it is not possible. ~AH1^(TCU) 23:17, 3 June 2010 (UTC)

I'd love to read about that test - do you have a link? Water definitely does some odd things, but I can't think of any interpretation by which it would have a fractional chemical formula like that. --Tango (talk) 23:55, 3 June 2010 (UTC)

I don't see it mentioned in Water (molecule), but see [18] for example. DMacks (talk) 00:09, 4 June 2010 (UTC)

That article says it isn't a property of water, but rather just the way hydrogen works - they tried the same experiment with benzene and got very similar results. --Tango (talk) 00:31, 4 June 2010 (UTC)

Perhaps you're thinking of the self-ionization of water (though I think that water is not the only thing that does that)? Paul (Stansifer) 00:50, 4 June 2010 (UTC)

It's not; the article talks about properties of certain molecules containing hydrogen where, under certain circumstances, on very short time scales, some of the hydrogens seem to not exist when neutrons are bounced off of them. It appears to be some sort of quantum effect. Buddy431 (talk) 01:20, 4 June 2010 (UTC)

With self-ionisation, the ratio of hydrogen atoms to oxygen atoms stays at 2:1, they just aren't joined together in the same way. This is something quite different and it seems nobody really knows why it happens. --Tango (talk) 01:29, 4 June 2010 (UTC)

There are alternate forms of solid ice, such as ice IV. Also under extreme pressure you may form a metallic phase. Graeme Bartlett (talk) 05:36, 4 June 2010 (UTC)

Other variations with different formulas are: Hydroxyl radical, Hydroxide, Hydrated hydroxide ion H₃O₂⁻, Hydronium and on a side track Dioxygenyl and peroxide. Also you can get Supercooled waterand Superheated water. Graeme Bartlett (talk) 05:57, 4 June 2010 (UTC)

interactions of colloidal gold

How strong is a bond between the surface of a gold nanoparticle and say, a lipid compared to most lipid-lipid interactions? What about polar molecules and aromatics? John Riemann Soong (talk) 18:27, 3 June 2010 (UTC)

Colloidal gold particles are charged, so they might have a small effect on polar molecules, probably not much else on any other molecules. --Chemicalinterest (talk) 20:34, 3 June 2010 (UTC)

see also Chrysiasis. Rmhermen (talk) 20:38, 3 June 2010 (UTC)

They're charged? I'm pretty sure the gold nanoparticles I am using are Au(0)... would some atoms be charged and not the others? John Riemann Soong (talk) 17:10, 4 June 2010 (UTC)

See Colloids#Interaction between colloid particles. Since they are often charged...--Chemicalinterest (talk) 23:10, 4 June 2010 (UTC)

An odd one - gold colloids are indeed Au(0) - the charge is often from citrate (from sodium citrate) stuck to the surface of the gold [19] or Cl- [20] - but they carry a negative charge - you can demonstrate this by using an electric field, see also 87.102.32.39 (talk) 00:38, 5 June 2010 (UTC)

Reduction potential of selenium

What is the reduction potential of selenium? (Se + 2 e^- ←→ Se^2-) --Chemicalinterest (talk) 20:36, 3 June 2010 (UTC)

-0.67V, if this tattered piece of paper in my disused chemistry notes folder is to be relied upon. ~ mazca ^talk 21:10, 3 June 2010 (UTC)

Sounds right. Oxide is +1.23, sulfide is +0.14, selenide is -0.67, telluride is -1.14... Thank you. --Chemicalinterest (talk) 21:18, 3 June 2010 (UTC)

Mmmh [21] gives a totally different figure - wonder why. The Table_of_standard_electrode_potentials gives a figure for Se <> H2Se - which is what would happen in standard conditions - it should be possible to work backwards from that if you've got figures for the acidity constant of H2Se87.102.32.39 (talk) 15:16, 4 June 2010 (UTC)

It could be that too, it still fits in with the periodicity of the chalcogens. --Chemicalinterest (talk) 23:07, 4 June 2010 (UTC)

That's why I didn't include any figures in the selenide article, just said they're moderately reducing. --Chemicalinterest (talk) 23:08, 4 June 2010 (UTC)

cell phone

how come my cell phone gets very hot if i talk for awile ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 22:06, 3 June 2010 (UTC)

Its microprocessor is doing more work, e.g. digitising your voice, converting incoming sound to analogue, and ancillary electronics are also doing more - driving the speaker and the aerial system. And the battery is doing more work to provide the current for all of this. When you're not talking, very much less is happening in all departments and so it keeps its cool. (What I'm not sure about, and perhaps someone else will be, is whether there's any significant microwave -> heat thing going on with it.) --Tagishsimon (talk) 22:13, 3 June 2010 (UTC)

it feels like it the battery that gets hot —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 22:26, 3 June 2010 (UTC)

It is the battery that get's hot. Your phone is using more energy. (Mostly through its radio transmitter, not its CPU) The more electricity your battery has to put out, the hotter it gets. APL (talk) 22:52, 3 June 2010 (UTC)

June 4

How does a battery-less moisture-meter work?

How would a moisture meter such as this work, bearing in mind that it uses no batteries? When inserting into soil, the needle flicks to the right before slowly moving a distance to the left and settling. Which of the readings can be considered the proper moisture level of the soil, based on how the device supposedly works? Would it be likely to harm the meter, to leave it sitting in soil, rather than removing and cleaning it every time? --92.25.237.15 (talk) 01:18, 4 June 2010 (UTC)

The picture clearly shows the two electrodes are made of different metals, so I would imagine it works in a similar way to a lemon battery. In the normal use of the device, the electrodes will be eroded (that's how it works - see the article I linked to), so leaving it in the soil will drastically reduce its working lifetime. --Tango (talk) 01:34, 4 June 2010 (UTC)

Have you tried covering the light sensor of the light meter? If the device stops working it might mean it uses the light as a source of energy. Either way, leaving it in the soil might not be a good idea. Have you tried asking the manufacturer? Dauto (talk) 02:45, 4 June 2010 (UTC)

That's a quote from the link provided by the OP "To avoid damaging the electrode, please clean the electrode after each use". I guess that answers the question. Dauto (talk) 02:50, 4 June 2010 (UTC)

Does Synthetic Vanillin / Vanilla contain Alcohol

Does synthetic Vanillin or synthetic Vanilla contain alcohol? Or is alcohol used in the process of making synthetic vanillin/vanilla? If yes which alcohols are used?---- —Preceding unsigned comment added by 212.22.185.11 (talk) 06:30, 4 June 2010 (UTC)

I think that vanillin is often dissolved in ethanol - pure vanillin would not contain any alcohol but if you were to buy a bottle of vanilla extract then it will contain 35% alcohol. 86.7.19.159 (talk) 12:21, 4 June 2010 (UTC)

I have a bottle of synthetic vanilla which contains: water, caramel color (to make it dark like real vanilla), flavors, potassium sorbate. No alcohol. --Chemicalinterest (talk) 12:42, 4 June 2010 (UTC)

Guys, vanillin is not water-soluble. It has to be dissolved in some sort of (edible) organic solvent or be stabilised with surfactants. John Riemann Soong (talk) 17:27, 4 June 2010 (UTC)

The "alcohol-free" vanilla flavorings I've seen use glycerol or other "not ethanol but similar-structure" solvent. DMacks (talk) 17:41, 4 June 2010 (UTC)

Vanillin is water soluble. Not highly soluble, admittedly, but I've regularly made 100mM solutions in water without it crashing out. Rockpocket 18:04, 4 June 2010 (UTC)

"Solubility in water 1 g/100 ml (25°C)" if we're to believe our own article. DMacks (talk) 18:10, 4 June 2010 (UTC)

Mercury and Dental Fillings

Let me preface this question with two things: this is not a request for medical advice, and I do not put any stock in amalgam fillings causing mercury poisoning. However, my question is related to the second point; supposing you took a normal sized amalgam filling and ate it, what would the effects be? What if you inhaled the equivalent ammount of mercury present? Finally, instead of ingesting/inhaling it all at once, what if you stretched out the time span to taking 1/500th of the filling every day, what would be the effects after 500 days (any number can be put in place of 500, I'm really just curious about how dangerous amaglam fillings would be, were the people opposing them correct.) 66.202.66.78 (talk) 10:43, 4 June 2010 (UTC)

Have you looked at Dental amalgam controversy which while not addressing your hypotheticals would seem the obvious starting point. Nil Einne (talk) 11:12, 4 June 2010 (UTC)

Mercury poisoning also has a lot of useful information. Between the fact that the mercury is in an amalgam with silver and is thus carried out of the body fairly easily - and the fact that the uptake of mercury through the digestive system is so low (0.01%), this is a really small problem. Mercury is exceedingly dangerous when it's reacted with other stuff - but the pure metal is much less nasty. The amount of mercury you absorb from a tunafish sandwich is likely to be greater than from accidentally swallowing a tooth filling. SteveBaker (talk) 13:06, 4 June 2010 (UTC)

Mercury is a rather inert metal, so its rate of absorption is low. Mercury compounds are reactive and toxic, and some of them are easily absorbed, making them extremely toxic. Improperly made dental fillings may be at more risk of mercury poisoning. --Chemicalinterest (talk) 14:38, 4 June 2010 (UTC)

I had a filling like this when I was a kid. I remember nausea and a lot of vomiting. --Ouro (blah blah) 15:56, 4 June 2010 (UTC)\

That may be better explained by stress or side effects of the anaesthetic, Ouro. The studies I've read show zero history of actual mercury poisoning effects in post-1950s dental fillings. SamuelRiv (talk) 17:33, 4 June 2010 (UTC)

As I recollect, I got this filling in communist Poland. I surmise that the quality might not have been that high. Or I was young, or stressed. No way to check it out. Just volunteering information, SamuelRiv. But thanks though. --Ouro (blah blah) 19:42, 4 June 2010 (UTC)

Technological family tree.

Partly a follow on from an earlier disscusion...

Has anyone here come across (in published sources) the idea of a technological family tree?

This being a diagram illustrating which technologies or discoveries are required for a particular technological development to occur.

Technology trees are used in the computer game Civilization and it's sequels and was wondering if these had been used in the academic world as well?

Sfan00 IMG (talk) 13:43, 4 June 2010 (UTC)

It's not really academic, nor does it involve a formal graphical "tree", but I'm reminded of James Burke's interesting series Connections and its sequels, which traced (some of) the developments that were necessary for particular bits of modern technology to arise. Deor (talk) 14:13, 4 June 2010 (UTC)

Burke's website here may also be of interest. Ghmyrtle (talk) 15:11, 4 June 2010 (UTC)

As you can see from his website, though, Burke would be the last person to describe technological advancement in that way as he's spent his professional life illustrating that technology in fact gets developed through all kinds of weird happenstances. He would (and is trying to) make a web, not a tree. Matt Deres (talk) 16:28, 4 June 2010 (UTC)

Well, the technology trees in Civilization are actually more complicated webs, as I recall. They are greatly simplified from real life, of course. --Tango (talk) 17:03, 4 June 2010 (UTC)

General histories of technology commonly note breakthrough technology which is the key to some later invention. A powerful compound electromagnet with many layers of insulated wire (Joseph Henry, 1827)) was essential to a practical electric telegraph relay and sounder(one which would function over miles of wire under all conditions), so Morse could not have introduced the practical telegraph before 1827. The phonograph (able to record and play back intelligible speech and music) was invented in 1877, but no breakthrough technology came along just in time as was the case for the Morse telegraph. It could have been built many decades earlier, or as early as good machine tools were available, perhaps in the 1770's, had someone chosen to mechanically impress concentrated sound vibrations on a medium such as wax, tinfoil, lacquer or even soft wood or clay. Edison (talk) 18:30, 4 June 2010 (UTC)

I think instead of a tree, it would be a directed acyclic graph with all edges pointing in the direction time is flowing. --Rajah (talk) 01:07, 5 June 2010 (UTC)

Houseplant identification please...

Unfortunately, I haven't a picture. In several stores around China I've seen a small houseplant for sale. It has one very large seed - almost as big as a golf ball - that is dark green and split down the middle from which a stem and a few leaves grow. I can't describe it better than that, but if you've ever seen one that should be enough. I've tried all manner of google searches and haven't hit on a picture. Can anyone out there help me? 91.216.105.31 (talk) 13:50, 4 June 2010 (UTC)

Are you sure it's a seed, and not some form of bulb? Sfan00 IMG (talk) 13:59, 4 June 2010 (UTC)

If the seed was red, then it could be a lychee which is a fruit, but I doubt if they are grown as house-plants. CS Miller (talk) 14:15, 4 June 2010 (UTC)

I've grown avocado seeds before, and the description of the seed fits the bill here. --TammyMoet (talk) 14:48, 4 June 2010 (UTC)

OP here, on a different IP. I'm sure it's not avocado (I've got one of those growing right now) - this seed is a dark forest green color and smaller than that. It has 2 clear hemispheres. I'm also sure it's not a bulb. If all else fails, I'll try and get a picture on Sunday for you all to look at... no chance before then though. 61.189.63.191 (talk) 15:40, 4 June 2010 (UTC)

Oil floating under water

News reports say there are "huge plumes" of crude oil from the leak in the Gulf of Mexico which are floating around below the ocean surface. [22] lists densities of various forms of crude ranging from 790 to 973 kg/cubic meter. compared to 1021.98 for "ocean water at 77 F." Tony Hayward of BP claims that"oil has a specific gravity that's about half that of water" per that news story, quite different from the s.g. values cited from the online source. In either case, what force would prevent the less dense crude oil from rising to the surface, or is it uniquely dense, or is the water in the Gulf uniquely less dense? Consider how much force would be exerted by 1 cubic meter of crude at the weakest assumption of 973 density for crude, when it was submerged in seawater at density 1022 kg/cubic meter? Would it be simply the mass difference of one cubic meter (49 kg) times 9.81 m/sec² or 480.7 Newtons (108 pounds force)? Does the density of the water change more than the density of crude with depth or temperature? Each barrel of oil (.159 cubic meter) should require about 17.1 pounds force to hold it below the surface. If it were in 1 ml droplets or smaller would it somehow not tend to rise? Is it supposed to float under heavier liquid from surface tension/force of habit/? Edison (talk) 16:32, 4 June 2010 (UTC)

My understanding is that the oil is mixed with gas, which blows it apart into droplets after it escapes. Just as tiny droplets of water may remain suspended in air for a long time, tiny droplets of oil may remain suspended in water for a long time. It's basically what happens when you mix the vinegar and oil to make salad dressing. Looie496 (talk) 16:53, 4 June 2010 (UTC)

I tried as an experiment releasing 0.1 down to 0.01 ml droplets of motor oil (density about 888 kg/m³ below the surface of a basin of (fresh) water (density about 998 kg/m³. The tiny drops tended to stick to the hypodermic needle, but when I shook it a bit they darted rapidly up to the surface of the water. How small are the "plume" droplets supposed to be, and what principle of physics or chemistry would keep them from rising? So far it sounds like "force of habit." Edison (talk) 16:56, 4 June 2010 (UTC)

I think it's a result of the dispersant they've been adding to the oil. It causes the oil to form droplets rather than a layer, and those droplets end up suspended in the water. I don't know the details. --Tango (talk) 17:01, 4 June 2010 (UTC)

If the droplets are down in the "few micron diameter" size then maybe they are in fact rising but some frictional effect of moving the water apart impedes the rise to a slow rate and some surface tension effect impedes their coalescing into larger drops with a greater terminal velocity of rise. Edison (talk) 17:06, 4 June 2010 (UTC)

Yes - upward force is proportional to cube, 'drag' proportional to square - so smaller drops should accelerate faster slower - though I expect there's a peak velocity in water as there is in air. Also viscosity

Don't think any surface tension effect would prevent coalescing though - unless when as a micelle

Perhaps there are down currents in that area that keep the drops underwater for longer ???87.102.32.39 (talk) 19:18, 4 June 2010 (UTC)

Keep in mind too that the crude is coming out pretty hot so it may also be partly fractionating, so the light ends will separate and head more quickly to the surface. The s.g. of vacuum tower bottoms is 0.97 to 1.03.[23] Admittedly, that is the very heaviest fraction. Franamax (talk) 17:19, 4 June 2010 (UTC)

If it so hot that it is "self refining" in a fractionating or cracking process, then why is it simultaneously so cold that it freezes up and clogged the removal dome? And the sludge left in a refinery (if that's what "vacuum tower bottoms " is) is still far lighter than seawater. For the stuff to stay in an emulsified blob below the surface, the blob would have to have a higher density than the water, or the entire column of water would have to be part of the emulsion. Edison (talk) 17:29, 4 June 2010 (UTC)

First of all, the crude is what's hot, it's the ocean water that is very cold, it is mixing with the gas portion of the outflow to form gas hydrates, that is what is clogging the containment domes. Second, the MSDS I linked for bottoms (it's only sludge when it's really hot, it's asphalt when it cools) says the specific gravity is 0.97-1.03, this [24] shows seawater wirh a s.g. of 1.025, so are you saying 1.025 >> 1.03? Or have you done all the lookups for temperature and pressure and you have a derivation for "far lighter than"? Lastly, all crude oil is "self-refining", that's why it stinks. The lighter fractions are separating preferentially and the benzene is making you dizzy. Crude oil is not one "thing", it is a mixture of many different compounds, each with a different partial pressure. There is certainly no cracking process at work, but the light ends will definitely get to the surface (and evaporate) faster than the heavies. That's why they've been discussing the problem with burning-off once the slick has been floating around more than a few days. Franamax (talk) 03:56, 5 June 2010 (UTC)

Press reports, such as one from the New York Times say one plume is "3 miles by 10 miles by 300 feet," which would be 7.5 x 10 ¹¹ cubic feet, which would be 133 x 10⁹ barrels of oil. The max leak rate estimate is 80,000 barrels a day, or about 3.5 million barrels total so far. Thus there appears to be a gross overstatement of the actual mass of oil involved in the plumes. A scientist states it might have the "consistency of thin salad dressing" in places, fostering the impression that far more mass of oil is in the plumes than seems likely. Edison (talk) 17:44, 4 June 2010 (UTC)

The media can also be quick to jump on a sensational story and slow to admit error. The laws of physics are hinting to me that this is what is going on. Googlemeister (talk) 18:26, 4 June 2010 (UTC)

Two things - when the Times gives the size of a plume, they're likely to be describing the volume in which the concentration of oil is appreciably higher than zero — not the volume of pure oil. Compare with coverage of the 2010 eruptions of Eyjafjallajökull, where our article discusses an ash plume more than 8 km high. The ash is there, it's visible, it's definitely occupying that volume — but no one assumes that there's a solid inverted cone of ash more massive than the volcano beneath; there's air mixed in. Indeed, the vast majority of the ash plume is air, just as the vast bulk of these oil plumes is seawater.

A second point that the ash also illustrates nicely is how long it takes for fine particles to settle. Air and volcanic ash particles have a much greater difference in density than oil and water, and air is a far, far less viscous medium than water — but volcanic ash still managed to stay suspended in the atmosphere for days and travel for hundreds of miles. I applaud your experimental spirit in your motor oil and water test, but if the oil is being forced out of the borehole and is undergoing turbulent mixing, then the droplets produced – at least some fraction of them – are apt to be significantly smaller than the 10-100 microliter volumes you tested. Using the creeping flow approximation to calculate terminal velocity, and assuming a density difference of 200 kg/m³ between oil and water one can estimate the rate at which oil droplets will rise to the surface. A sphere 1 mm in diameter (which is quite distinctly visible, though it only has a volume of about 0.5 microliters) would have a terminal velocity of just 3 millimeters per minute; the effect of its bouyancy would in most cases be dwarfed by the effect of rising or falling ocean currents. At that speed, droplets deposited at the borehole depth of 1500 meters would take about a year to reach the surface. TenOfAllTrades(talk) 20:11, 4 June 2010 (UTC)

One of the biggest sources of error here is accurately estimating the density of the oil that is coming from the reservoir. It is at least plausible that some of the oil in the Gulf of Mexico is on the order of 10° API - in other words, heavy oil - in which case it is not less dense than water. Deep below the sea surface, there is not much turbulence, but as the plume jets its way out of the bore-hole (or some other place where it is leaking), it is probably spraying out in a very turbulent way. This may complicate its path to the surface. If the pressure were low, the plume would rise as a laminar flow to the sea surface (where wave action would turbulently mix it in the top few feet of water). But since the borehole pressure was very high (enough to cause a blowout), it is hard to predict exactly what happens as the oil contacts the open ocean at the sea bottom (or other leak location). As has been pointed out above, the situation is further complicated because the fluid that is leaking from the reservoir is a mixture of crude oil, natural gas, sediments, brine, drilling mud, drilling crud, and other impurities. Nimur (talk) 19:17, 4 June 2010 (UTC)

Heavy crude oil describes that product as bitumen or oil sand. Is there any evidence that was in the deposit they drilled into, or that it is found in that area of the Gulf? It sounds like heavy crude does not flow well in general. Edison (talk) 20:20, 4 June 2010 (UTC)

[25] "What we're doing is we're taking a highly pressurized solution, and we're exploding it out of the sea floor under high pressure and high velocity."

expand assuming the oil is tar+oil+gas then at lower pressures the gas will boil off .. pressure increases with depth - it's possible therefor - that as the mixture rises further de-gassing (of methane/ethane etc) happens. It's possible again that this degassing is sufficiently violent (especially if it becomes supersaturate with gas before boiling) that this loss of gas causes the droplets to become yet smaller, again reducing the speed at which they rise. It's also possible that this doesn't happen or the effect is negligable.

I didn't actually see anywhere a claim that the liquid is heavier than water though. Density of 0.8 - 0.9 cc takes quite a long time to rise hundreds of feet - and there may be strong lateral currents.

Did you misread the CEO ? :

Mr. TONY HAYWARD (Chief Executive Officer, BP): There's no evidence of (that) .. (the) oil has a specific gravity that's about half that of water. It's very difficult for oil to stay in the column. It wants to go to the surface because of the difference in specific gravity.[26] [27]

As regards the density vs. depth question compressibility is the thing you want this compares toleune and water (tolune is ~twice as compressibile at 8.94 x 10-4 MPa^-1) - so maybe there is something in this idea.. but it's a very small figure (no idea what the pressure is down there) There should be better tables somewhere on the internet.87.102.32.39 (talk) 19:56, 4 June 2010 (UTC)

87.102.32.39 (talk) 19:27, 4 June 2010 (UTC)

Hayward seemed to be trying to say that the oil has a low specific gravity and that there was no evidence of plumes (despite the fact that he was speaking in a nonsentence which could be taken to mean the opposite). Edison (talk) 20:22, 4 June 2010 (UTC)

Uh - yes - I think they mistyped in the link is used (corrected it) - looks like they've joined two sentences together - but it does look like he was saying oil has half the density of water. (The english have acquired the bad habit of lying/stretching the truth in the last decade - I know . live there.)..87.102.32.39 (talk) 20:48, 4 June 2010 (UTC)

Several news sources ([28] [29] [30]) have used the terms "heavy crude" and "tarballs". It is not clear whether this terminology is scientifically accurate or media hype. Heavy oil is definitely known to exist in the gulf, and indeed is the primary constituent of the geologically similar Orinoco Belt. Biological activity in the deep subsurface and the origin of heavy oil (Nature, 2003), states: "Biodegraded oils also represent a significant fraction of the petroleum in conventional oil reserves and will be common among future oil discoveries likely to be made in deep-water areas of the world (for example, the Atlantic margin basins of Africa, South America, Canada and the Gulf of Mexico)." Reservoir geochemistry of South Pass 61 Field, Gulf of Mexico: compositional heterogeneities reflecting filling history and biodegradation (Organic Geochemistry, 1996) has tables of geochemical analysis. A quick look through some of my Oil & Gas Journal archive has a bunch of market report stories on "heavy" crude in Gulf of Mexico - I'm looking at a February 2010 issue talking about 14 and 17° oil production in Louisiana. Those would still be lighter than water, though. Unfortunately, the exact chemical makeup of the Macondo is pretty intensely "company confidential" and I'm sure only privileged members of BP's production team know what's coming out of the reservoir. Nimur (talk) 20:56, 4 June 2010 (UTC)

John Ebdon, an Emeritus Professor and chemist at Sheffield University said in a letter in Friday's Guardian (can't find a link): "...True, seawater has a specific gravity of about 1.03g/cubic cm whereas that of crude oil is about 0.8g/cubic cm ... but significant fractions of crude oil consist of asphaltenes and other complex substances with specific gravities around 1.4g/cubic cm ... these heavier fractions will almost certainly separate and so be retained at depth." --Tagishsimon (talk) 04:11, 5 June 2010 (UTC)

The improvised refinery which fractionates the oil to create the asphalt/bitmen submarine is of dubious plausibility. Asphalt of dubious 1.4 density "retained at depth" would not wash up on Pensacola Beach and would not be much more of an issue than if it had not been brought up by drilling. The media creates spectres of "plumes" of oil many orders of magnitude greater in mass than could possibly exist. Edison (talk) 04:41, 5 June 2010 (UTC)

Doorbell Continually Hums or Buzzes

the button is stuck in the contact position. how long till the electromagnet will burn out and the bell unit won't work —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 17:30, 4 June 2010 (UTC)

Why not just disconnect and repair it, rather than go through the discomfort of waiting for it to burn out. [31] which I suspect you've already read as it's linked to from a page almost identical to your question, gives you a description of how to dissemble a doorbell. Regards, --—Cyclonenim | Chat  17:37, 4 June 2010 (UTC)

can you just tell me how long till it burns out? i dont have the tools right now. —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 17:50, 4 June 2010 (UTC)

It depends, but "long" is a good estimate. Think weeks or months, or even years. There is no particular reason why anything should "burn out". --Stephan Schulz (talk) 17:57, 4 June 2010 (UTC)

A defective doorbell circuit is likely to cause radio, television and celphone interference, which is one good reason to get it fixed. Some doorbell transformers have a thermal protection element which heats up and opens the current , then resloses, providen a spark each time which interferes with electronic communication. The thermal protector often burns out and just arcs continuously, provide ongoing interference. In the US, it is a violation of the FCC rules to create "harmful interference". A shorted transformer could also start a fire, [32]. (Paradoxically, in a great many instances over the years, doorbell wires shorted by a house fire have alerted the family and saved their lives).How long would it take to burn out? I once read an account of a person growing up in an apartment with a defective doorbell circuit. The transformer or chime hummed all the time, 24/7, except when someone pressed the doorbell, at which time it quit humming momentarily, and they knew someone was at the door. Edison (talk) 18:00, 4 June 2010 (UTC)

Doorbells are often very high-current devices - you may be burning two or five amps if the electromagnet is constantly activated. (Some are lower-power - here's a 30 watt bell). Most bells are not intended to be "energy-efficient", because you want the bell to be loud and momentary - so effectively, they are designed to consume on the order of 50 or 100 watts, (but quickly shut off). If the switch is stuck in contact-position, and you are burning a steady 50 or 100 watts, over a month that will add up) and will cost you in the neighborhood of $5, depending on your electricity price. Nimur (talk) 19:08, 4 June 2010 (UTC)

That makes me wonder, is there a danger that it was installed with wiring that can't handle constant use? APL (talk) 20:45, 4 June 2010 (UTC)

Actually, since you mention it - that's certainly possible in older houses. In the UK, there is stuff called "bell wire" that used to be used specifially for wiring up doorbells and those bell systems in big houses that let the lady or gentleman of the house summon servants from the kitchen from any room in the house. That wire was very thin indeed, single-core with enamel paint insulation. Bell wire was the home-experimenters wire-of-choice back when I was a kid because it was cheap and you could get it in any electrical repair store. So it wouldn't surprise me at all if it overheated and burned out in an old property...and that's a fire risk. But I'd expect chunkier wiring in modern doorbells - so it's probably not a problem for a house that's less than maybe 50 or 60 years old. SteveBaker (talk) 04:25, 5 June 2010 (UTC)

can any of these radio frequencies harm me?

No. APL (talk) 20:45, 4 June 2010 (UTC)

Really - you can trivially repair this with no more tools than a screwdriver - or (if desperate) a kitchen knife - or maybe even a thin coin! Waiting - on the offchance that it'll just blow up and "fix itself" - is pretty pathetic. Turn off the power, unscrew the bell button or pop open the cover, if the contacts inside look corroded then just scrape off the surface corrosion with your knife/screwdriver - then bend them so they don't quite touch when the button isn't pressed, and do touch when it is pressed. Reassemble the button and turn the power back on - and you're done. It couldn't possibly take 10 minutes to fix. SteveBaker (talk) 23:12, 4 June 2010 (UTC)

Curiously enough, there was "bell wire" before electricity was in use. Great houses in the 18th century, including the White House in John Adams' Presidency had "bell pulls" to signal servants that someone in a certain room wanted a servant to come. The "bell wire" was uninsulated copper, brass, or iron running to the kitchen or "Servant Central" where a pull on it rang a bell. Edison (talk) 04:31, 5 June 2010 (UTC)

Yes - I noticed that when I searched Wikipedia for bell wire and found it mentioned in Bell pull. It did surprise me to see the term used that way. I wonder whether these old houses went from physically pulling the wires to passing electicity down them when they converted to new-fangled electrical systems (maybe using an earth as the return path). That would save ripping out the walls to put in the new wires. But the stuff I remember having as a kid in the late 1950's was single-core copper, very brittle and coated with what looks like a brown enamel paint or maybe a dark varnish...that was called "bell wire" too. The electrical projects in "Boy's Own" style books always specified either "Bell wire" for battery-powered things or "Lamp wire" where higher current was required. This definition on Answers.com confirms my memory. SteveBaker (talk) 04:56, 5 June 2010 (UTC)

The difference between fire and plasma

Take this image for example, it's a projectile fired from a railgun. But of course, there are no explosives involved so that trail behind the projectile is plasma and not fire correct? So is it fair to say that plasma and fire can look the same sometimes, but are two different things? ScienceApe (talk) 18:06, 4 June 2010 (UTC)

You don't need explosives for flame; just heat, oxygen, and something to burn. --Sean 18:53, 4 June 2010 (UTC)

(ec) Most of the time, ("day-to-day" interpretation), when you think of fire, you are thinking about two things: (1) an oxidation reaction between oxygen in the air and carbon (or something else) in the fuel; and (2) a gaseous semi-ionized plume of hot air that is incandescent - glowing reddish yellow because it is so hot. The chemical reaction (1) provides the energy and heat, and contributes some chemical constituents to the flame plume, but mostly the glowy part is just the ambient air getting heated up (and indeed, somewhat ionized). It would be fair to call that flame plume a "plasma" - but more specifically, it would be a dense weakly-ionized plasma. In other words, it is more "gas-like" than "plasma-like", in that thermal interactions dominate the behavior, rather than electromagnetic interactions. Typically, in plasma physics, we like to think about "sparse" (i.e., nearly a vacuum) plasmas where the collisions between molecules and ions are very rare. But plasmas can be created in many ways - anything which provides enough energy to ionize a gas sufficiently that its electromagnetic effects are non-negligible. That can be a chemical flame, or any other energy source.

All this being said, let's analyze the railgun photo you linked. Unfortunately, the caption/description is not really very explanatory - it says the gun is "electromagnetic," but that doesn't necessarily mean that there was no explosive (a lot of railguns use a primer charge to create a super-compressed gas in preparation for additional energy). It's also possible that at 2000 m/s, the hypersonic projectile is tearing up its surrounding air so much that the thermal energy imparted to the shock cone is enough to incandesce or even ionize. To what extent is the shock cone ionizing? To what extent does the electromagnetic propulsion system ionize the surrounding air? To what extent does the primer-charge interact with the muzzle blast? How do these parameters affect the muzzle ballistics, kinetics, trajectory, and the energy balance for the projectile? All of these things would be interesting research questions, and I would bet that the NSWC guys are instrumenting the heck out of this apparatus to answer exactly those kinds of questions. But we only have the image caption - without further information, it's not easy to answer definitively. But keep in mind - a plasma is just a gas that has been ionized so much that the electromagnetic effects are dominant, whether it's ionized by energy from a chemical fire, thermal collisions, electromagnetic radiation, nuclear energy, hypersonic shock, or other energy source. Nimur (talk) 18:57, 4 June 2010 (UTC)

chemisty I've always understood most flame/fire to be primarily a radical reaction - also high energy but not a "full" plasma since many of the entities are neutral. If the flame is hot enough though gas will be ionised.. answer? it's a borderline case depending on T and gases burnt as well.87.102.32.39 (talk) 19:38, 4 June 2010 (UTC)

(EC)Plasma and a fire can look alike. Both can involve very hot gases. See Plasma (physics), which says that a plasma is electrically conductive because of ionization. But flame and smoke can also be conductive, depending on what the chemical composition is. Edison (talk) 19:01, 4 June 2010 (UTC)

If you look at the video that this shot was taken from, I think that it appears to be flame, not plasma. J.delanoy^gabs_adds 19:05, 4 June 2010 (UTC)

I can't tell - but yellow air plasma isn't usual. A plasma should decay without any soot etc. Maybe there was some coating on the 'bullet' that caused the plasma to go yellow?87.102.32.39 (talk) 19:45, 4 June 2010 (UTC)

You're right, for it to glow that brightly there must be something more than just incandescent air. With a flame, there are tiny particles of soot glowing (if you have complete combustion with no soot then you don't get a yellow flame, you get a dim blue flame that isn't caused by incandescence). There must be something similar in that plume. --Tango (talk) 19:54, 4 June 2010 (UTC)

This sounds 'clu-ey' [33] "Particle debris ignites as a test slug exits the Office of Naval Research (ONR) 32 MJ (megajoules) Electromagnetic Railgun (EMRG) laboratory launcher located at the Naval Surface Warfare Center Dahlgren Division (NSWCDD)." 87.102.32.39 (talk) 20:04, 4 June 2010 (UTC)

Also, we have no way of knowing whether the photo is a true-color or false color image. I'm leaning towards a Schlieren photography, Rapatronic camera, polarizing filters, or some other "weird" photographic trickery (not even counting post-production digital color rescaling!) Note that the timestamp has microsecond precision. Such high-speed cameras often are monochromatic. Note how you can see the shock cone - that's a dead giveaway for a shadowgraph or Schlieren system. So, we can't say for sure whether the yellow and green in this photograph are "meaningful" for analysis. Nimur (talk) 21:11, 4 June 2010 (UTC)

There's an even more clear image of the shock cone at this link (scroll down) [34] 87.102.32.39 (talk) 21:30, 4 June 2010 (UTC)

Horse's mouth [35] "The flames are from pieces of the projectile disintegrating; the 7-pound slug is jammed so firmly between the rails that when it’s fired, pieces shear off and ignite in the air."

one commenter says "...but the video is slightly out of order... the first shot is of the impact. If you pause the video around 6-7 seconds you can see the projectile only has a plasma trail until it strikes the target." (same link) this isn't quite right the image above is earlier in time than that in which the projectile flys between gun and target.

The linked video has time count in the lower right . so if doubtful you can check for yourself. 87.102.32.39 (talk) 21:49, 4 June 2010 (UTC)

This image is confusing File:EMRG 070128-N-0000X-001.jpg - apparently showing a very similar moment in time - but a different colour - since the slug is aluminium and the fire is supposed to be from particles from the slug I would assume that the photo is a better colour representation. So why is the video footage (and the frame above) yellow?87.102.32.39 (talk) 22:12, 4 June 2010 (UTC)

Archimedes principle???

if a body is immersed in a fluid,is the volume of the displaced fluid equal to the volume of the body???......... —Preceding unsigned comment added by Researcher02 (talk • contribs) 19:38, 4 June 2010 (UTC)

Only if it sinks - this can be demonstrated with a full bathtub, large amounts of polystyrene foam, and some lead shot..

The density of the body must be more than the density of the fluid.87.102.32.39 (talk) 19:42, 4 June 2010 (UTC)

(e/c) under conventional assumptions (non-viscous fluid, unconstrained and not otherwise subject to compression, non-bouyant, non-dissolvable object, etc), yes. The fluid will conform to the shape of the object (so displacement will not be greater than the volume of the object). note that for hollow objects, displacement will differ according to whether the interior spaces are open or sealed - open spaces will fill, making the displacement equal to the volume of the solid material; sealed spaces will displace both the volume of the solid mass and the volume of the sealed space. --Ludwigs2 19:48, 4 June 2010 (UTC)

(ec) The volume of the displaced fluid is equal to the volume of that part of the body that is in the fluid. If the object sinks, that will be the whole body. If the object is floating then it will only be part of the body (a part with volume equal to the volume of the fluid that has the same mass as the object). --Tango (talk) 19:49, 4 June 2010 (UTC)

The article section about this is Buoyancy#Archimedes' principle. Comet Tuttle (talk) 21:09, 4 June 2010 (UTC)

The OP's question does not concern Archimedes' principle. The OP did not ask about a floating body. Cuddlyable3 (talk) 22:41, 4 June 2010 (UTC)

Why did my bonfire burn 'blue'?

Last summer, I used a bonfire to dispose of a large quantity of waste wood (mainly laurel branches) in my garden..

I noted that, when started the fire was rather yellow and produced a lot of smoke, but as it got going it smoked a lot less and changed from a yellow flame to a more blueish and less visible one...

What might be the cause of this?

In addition, a previous bonfire in a previous year apparently managed to make a small quantity of charcoal, although I'm not entirely sure how... The same bonfire for whatever reason was also able to be 'relit' merely by placing suitably dry fuel on the ashes the following morning, which came as a quite a suprise...

Anyone care to suggest a possible explanation for the charcoal production? or for the 're-light' capability? 62.56.112.251 (talk) 20:19, 4 June 2010 (UTC)

It's very common for a wood fire to create coals that stay burning hot overnight, in some cases they can continue to burn for days. That article describes them better, but briefly: after the outside of the wood burns, and the more volatile componants of the wood have escaped and burned, the heavier carbon based solids in the innermost parts of the wood stick around because they haven't been properly exposed to the air, but at the same time they're not volatile to evaporate through the hot wood. Usually these componants burn very slowly making hot coals. (These are good for cooking over, because of their even heat.) If they go out before they're entirely spent I suppose you'd have charcoal. (Which does not come from true coal. A lot of people are confused on this point.)

Hot coals can stay hot for a suprisingly long time because they're covered in a layer of light, fluffy ash that both insulates them and prevents very much oxygen from reaching them. That way they don't cool off, but they also don't burn up very quickly. APL (talk) 20:39, 4 June 2010 (UTC)

Indeed - a fairly large bonfire will usually have hot embers left for several days. --Tango (talk) 21:12, 4 June 2010 (UTC)

Follow on question, Would this 'coals' method be exploitable for low-level metalworking? Sfan00 IMG (talk) 21:55, 4 June 2010 (UTC)

Did you mean could the charcoal you made be used for metalworking? I see no reason why not - it was used in the past,as the article charcoal says. 87.102.32.39 (talk) 03:21, 5 June 2010 (UTC)

Hmm. Have you seen She? --Trovatore (talk) 20:42, 4 June 2010 (UTC)

I would think that at first the oxygen supply was limited. After a while it started burning more completely, producing the hotter blue flame and less smoke. --Chemicalinterest (talk) 20:54, 4 June 2010 (UTC)

The yellow flames are incomplete combustion. The blue flames are complete combustion. If everything burns cleanly then there are no soot particles to glow red-hot, which is what gives the flame its colour. --Tango (talk) 21:12, 4 June 2010 (UTC)

June 5

Reduction potential for nitrate

What is the reduction potential for this reaction: 2 NO₃^- + 12 H⁺ + 10 e^- ←→ N₂ + 6 H₂O Thank you. --Chemicalinterest (talk) 00:28, 5 June 2010 (UTC)

from [36]

NO3- > NO 0.957

NO > N2O 1.591

N2O > N2 1.766

I think you can just add those ~2.2V ? Maybe not - different number of N atoms... Different number of electrons transfered in each reaction.

It's {(0.957x3)+(1.591)+(1.766)}/5 (reason for that formula at Standard_electrode_potential 87.102.32.39 (talk) 01:20, 5 June 2010 (UTC)

About 1.25V also see here [37] 87.102.32.39 (talk) 01:39, 5 June 2010 (UTC)

Who first hypothesized/discovered/elucidated gluconeogenesis?

Who first hypothesized or discovered or elucidated gluconeogenesis? Thank you. --Rajah (talk) 00:54, 5 June 2010 (UTC)

this link mentions some key people (last 2 paragraphs) 87.102.32.39 (talk) 03:17, 5 June 2010 (UTC)

Thanks, but that's about glyceroneogenesis, which is a subset of gluconeogenesis. The conversion of pyruvate to glucose would be the major component of gluconeogenesis. --Rajah (talk) 06:52, 5 June 2010 (UTC)

Brass

Alloys of Copper and Zinc create a how to hop metal brass.lam not work on this solution and HCl solution H2SO4 ? —Preceding unsigned comment added by I love chemistry (talk • contribs) 04:02, 5 June 2010 (UTC)

"How to hop?" Leap up and down. What does this have to do with alloys? Edison (talk) 04:27, 5 June 2010 (UTC)

Could you please rephrase your question, I don't really get what you're trying to do. 67.170.215.166 (talk) 04:30, 5 June 2010 (UTC)

Sounds like "I love chemistry" is asking how to separate Cu and Zn in brass using HCl and H2SO4, which sounds a little like a homework problem, though I won't assume, but I recommend checking [[reduction potential]s and noting if any salts will precipitate. SamuelRiv (talk) 05:41, 5 June 2010 (UTC)

Asa Gray and John Edward Gray

I'm planning on editing a few articles on nineteenth century biology and I've come across a question I can't answer. Is there a relationship between Asa Gray and John Edward Gray? I know one is British and the other American, but they both seem to be biologists during the same time period. I'm most interested in if they are related biologically and if they there are any primary sources mentioning the relatedness of both of them. Thanks a bunches :) Peter Napkin Dance Party (talk) 07:27, 5 June 2010 (UTC)