Wikipedia:Reference desk/Archives/Science/2007 June 29

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June 29

One really strange effect...

Hello, I own one of those plasma bulb things, (you know what I'm talking about) and I noticed a really strange effect with it that doesn't make sense to me. If you turn on a plasma bulb and put something on it that can conduct electricity (metal works best) anything that touches the metal and can also conduct electricity has a static shock/charge with the metal. I was wondering if whether the electrons in the plasma bulb flow through the metal and jump to another object or if the plasma bulb negatively/positively charges the metal and it creates a charge similar to that of Lightning but on a much much smaller scale. Thanks for your time!- User:ECH3LON

Capacitance allows high-frequency electricity (alternating current) to flow "through" insulators such as the glass bulb of the plasma lamp. Enough electricity flows through that, concentrated by the metal rod onto a small area of your hand, you perceive it as an electric shock.

Atlant 12:32, 29 June 2007 (UTC)

hydrometallurgy in situ leaching

Eskall 02:19, 29 June 2007 (UTC)What are the environmental or other hazards or risks, e.g. health and safety, associated with in situ leaching in mining operations?

Typically the obvious problem is if the leached liquid runs off (heavy rain etc) it can contaminate nearby streams, soil contamination is also a possibility.87.102.4.153 12:01, 29 June 2007 (UTC)

Normaly heavy metals are present as unsoluble sulfides or oxides and therefor are not mobile in the water (ground water), by leaching you mobilize them. The two incidents which makes the problem clear is the leaching of gold by potassium cyanide, which is a really very toxic substance, and the other was tests with uranium leaching in east Germany which can create a poblem if by exident the now soluble and mobile heavy metal reaches the ground water.--Stone 12:13, 29 June 2007 (UTC)

Largest cow

This highland cow may not be the largest, but it is certainly the most attractive. Nimur 16:52, 29 June 2007 (UTC)

Which is the biggest cow and cow race in the world? In terms of height, length, mass... I'm aware about the massive Piedmontese and Belgian Blue but was wondering if others were even larger though less muscular. --Taraborn 06:50, 29 June 2007 (UTC)

According to this Lyneham News article Charolais are the largest breed. There is a giant cow near Nambour in Australia and Salem Sue in North Dakota, but these aren't what you are looking for. --TrogWoolley 09:53, 29 June 2007 (UTC)

Strictly speaking, you are looking for cattle. A female African elephant seems to be the largest terrestrial cow, and the blue whale the largest sea-going cow, but those aren't what you're looking for either.--Shantavira|^{feed me} 10:45, 29 June 2007 (UTC)

Damn, I can't believe I've been deceived for so many years by my English teachers. Thanks to all. --Taraborn 14:36, 1 July 2007 (UTC)

If a Butterfly Flaps its Wings

I have heard a saying that goes something like this: if a butterfly flaps its wings in Mexico, that creates a hurricane in Japan (or something like that). Is there any truth to that, or is it an old wives tale / urban legend? If it is true, can you please explain the science behind it (in elementary terms). If it is not true, what is the origination of that saying and why does it persist? Or is it just a metaphor for something else? If so, what? Thanks. (JosephASpadaro 07:37, 29 June 2007 (UTC))

What you are referring to is the so-called butterfly effect. It is an expression which should by no means be taken literally, but the story is that the atmosphere is such a complex fluid environment that something as minor as the flap of a butterfly could determine (some time later, mind you) whether or not a major storm system will develop. This phenomenon is known as chaos, or extreme sensitivity to initial conditions, first discovered by meteorologist Edward Lorenz in the 1960s. In a nutshell (sorry if I use too much math language), some systems (such as the earth's atmosphere) are governed by non-linear differential equations. In an ideal mathematical situation, where you know the conditions at all points in a situation, it is possible to predict its future behavior accurately. However, since the supercomputers which simulate the weather take data from weather stations which are spread far apart, they must estimate the conditions between weather stations, and so do not know the exact conditions of the earth's atmosphere. Because the atmosphere is chaotic, the small difference between the actual atmosphere and the computer simulation compound to become large differences as the simulation wears on, making even rough weather prediction more than 10-14 days in advance practically impossible. One estimate is that even if we had weather monitoring stations every 1 meter in all directions, feeding data simultaneously into an infinitely powerful supercomputer, that computer could still not predict the weather with any certainty 30 days later. Hope I've helped, feel free to ask for clarifications! -RunningOnBrains 07:50, 29 June 2007 (UTC)

We have an article on the Butterfly effect which covers this, but it may be somewhat too technical. In short, for a complex, non-linear system like the weather, a very small change (a butterfly flapping its wings) may be magnified over time to a huge effect (a hurricane). --Bob Mellish 07:48, 29 June 2007 (UTC)

Hmmmmmmmm. So, taken literally, it is or it is not true? That the butterfly's flap causes the hurricane ... (JosephASpadaro 07:57, 29 June 2007 (UTC))

No. --_ʇuǝɯɯoɔɐqǝɟ 08:00, 29 June 2007 (UTC)

One way of thinking about chaos is to imagine a steep hill that has a ball precariously balanced at the very top. The slightest difference in the way you touch it will send it on its way downhill to a much different destination. So too with a butterfly's wings and the hurricane. Is it likely? No. Is it possible? Yes. Clarityfiend 08:19, 29 June 2007 (UTC)

I think we can say it's literally true that a butterfly flap may influence when and where a future hurricane or tornado starts and where it's heading. This takes into account conservation of energy. There's a whole lot of energy in a hurricane and that energy would have had to go somewhere, regardless of the butterfly flapping or not. EverGreg 08:31, 29 June 2007 (UTC)

My understanding of it is that every major event is underpinned by so many seemingly unconnected albeit equally prerequisite minor events that there is no way of determining what they all are as an exact science, hence chaos theory. Some may wonder whether if Franz Ferdinand had been shot, would there ever have been two world wars at all, but think of all the minutest changes in events preceeding that day in 1914 that may have spared his life and changed the course of the twentieth century. A butterfly perching on his shoulder, distracting him enough to move his jugular out of the bullet's trajectory perhaps? Bendž|Ť 08:45, 29 June 2007 (UTC)

Well that's a more philosophical approach, I think Bendzh, and many would argue the long term causes of war would have been sparked by some other incident. But the real point is the mathematical one, that small changes in initial conditions lead to large changes in outcome. One problem is that the relation between accuracy of input (i.e. measurement of initial conditions) and accuracy of prediction are logarithmically linked. Which basically means (roughly) that increasing your accuracy of input by a factor 10, may only improve your predicition by a factor 2, increasing it by a factor 100 might only improve your prediction by a factor 3. We'll never know if an individual hurricane was caused by a butterfly Rather like global warming, although the tendency is to blame every bit of extreme weather on climate change, all we can really see are long term trends. 137.138.46.155 11:42, 29 June 2007 (UTC)

A Paul Harvey news report yesterday marked the anniversary of the shootong of Franz Ferdinand in 1914. He said the motorcade route for the Archduke had been changed at the last minute due to security concerns after a bomb explosion earlier in the day, but his driver was not informed, and took the original route, carrying the car right by where the assassin was waiting. Perhaps someone forgot to mention it to him because of being distracted (maybe by a butterfly or a bumblebee?). In the Wikipedeia article on the assassination there was a paragraph previously about chaos theory and the event, but it was removed. Edison 12:48, 29 June 2007 (UTC)

The Quantum Weather Butterfly has a lot to answer for! DuncanHill 13:04, 29 June 2007 (UTC)

In chaotic systems (like the weather) we find large scale stabilities (eg I'm guessing that there have been no hurricanes sweeping over the Sahara desert in all of recorded history - yet we can be fairly certain that at least a handful of them will be sweeping across the Atlantic on the next hurricane season) - but there are small-scale events that are utterly unpredictable (eg will it rain at the Town Hall in Cedar Hill, Texas on July 17th at precisely 2:43pm?). Even in theory, we cannot know enough information about the atmosphere to make even rather general predictions at this fine scale more than a day or so into the future. The position and momentum of every single atom in the entire earth, sun, moon system (and beyond) has a bearing on the weather - and a change in any one of those things could change precisely when and where a hurricane might happen at some time in the distant future - although we can be pretty sure that no matter what, it won't happen over the Sahara. But we can't say for sure which butterfly, on which wingbeat in which part of China is the cause of what future event. In a sense, they all have an influence - so it's true to say that things would have come out differently at some very fine scale of measurement if that butterfly hadn't chosen that moment to flap. But it's not really true to say that (for example) Hurricane Katerina was directly caused by a butterfly ten million years ago, because it was also caused by you failing to have an attack of hiccups on your third birthday because your mother wouldn't let you eat that extra slice of cake - and that cometary fragment that just missed the moon 10,000 years ago was also 'the cause'. This sensitivity to long-past events is the key here - but its' essentially INFINITELY sensitive - to the point where the uncertainty principle of quantum theory ends up being responsible (in part) for that same hurricane. The point here is that the butterfly wing analogy is not meant to be taken literally to be true - it's just a handy shorthand for chaos theory and sensitive-dependance-on-initial-conditions. SteveBaker 14:36, 29 June 2007 (UTC)

This is probably obvious by now, but the point of the argument is obviously not that any butterfly flapping its wings necessarily will cause a hurricane, but that it might. And even if, via some kind of total meteorological omniscience, we were to determine that a particular butterfly flapping its wings had caused a hurricane that otherwise would not have happened, we would also find that it was equally caused by (for example) a particular bumblebee that did not flap its wings, and a particular passenger jet shedding some ice from its wings, and a particularly ravenous baseball fan wolfing down some Buffalo wings, and a particular oldies fan fondly listening to Paul McCartney and Wings. So we can hardly blame the butterfly, let alone go after its liability insurance carrier to try to recoup the hurricane damage... --Steve Summit (talk) 14:51, 29 June 2007 (UTC)

The Flight of the Bumblebee

When I was younger, I was told that aerodynamically speaking, a bumblebee should (theoretically) be unable to fly (due to some physics principles and the anatomy of the bee). Yet, bumblebees do in fact fly. Is there any truth to the statement that theoretically their anatomy should render flight impossible? Or is this an old wives tale / urban legend? If the statement is theoretically true, have scientists reconciled that with the reality that the bees do fly? How so? Please keep the science / physics explanations at an elementary level. Thanks. (JosephASpadaro 07:37, 29 June 2007 (UTC))

Bumblebee#Flight --_ʇuǝɯɯoɔɐqǝɟ 07:51, 29 June 2007 (UTC)

Urban legend - perpetuating a pile of steaming nonsense - dating from a 1934 book (think about the state of the aeronautical sciences in 1934!) - that incorrectly applied the physics for a fixed wing aircraft to an animal that flaps its wings [1]. Similar arguments were applied to the 'fact' that Dolphins can swim faster than physics says is possible. That one turned out to lead to some very interesting discoveries about micro-turbulance caused by the ingenious fine surface texture of the dolphins' skin. No laws of physics were broken - but it took some effort to understand why not! On a more serious note - if there is an outstandingly counter-example to a physical law - then that law has been overturned and it's no longer considered a law. If the bee's flight truly violated physics then you could be very sure that physicists would be working very hard indeed to understand what was wrong with those laws and coming up with new ones to replace them. Scientists get very excited indeed on those rare occasions when this happens because that's where the big breakthroughs and the Nobel prizes can be found! If something as easy to study as a bee lead to that kind of thing - they wouldn't be interested in billion dollar telescopes and atom smashers. SteveBaker 14:09, 29 June 2007 (UTC)

It's been said that the "payoff" sound in science isn't someone shouting "Eureka!" but is, instead, someone softly saying "How odd..."

Atlant 16:57, 29 June 2007 (UTC)

"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' ('I found it!') but rather 'hmm....that's funny...'" —Isaac Asimov

For one thing, bumblebees have to "warm up" before they can take off, particularly on a cold day. Since the chemical reactions which power them are temperature sensitive, this gives them more power than they would have at ambient temperature. A similar thing goes on in the swimming muscles of tuna. Not every creature that is termed "cold-blooded" is actually cold, they just aren't constant in their temperature, like us. Gzuckier 15:59, 2 July 2007 (UTC)

When you push your eye...

What is the little black spot you can see on the other side of the eye? Also, I had an impact to my eye once (It's fine now though) that causes a large one of those. What are they? Xhin Give Back Our Membership! 12:01, 29 June 2007 (UTC)

I can't see one here, but are you referring to an entoptic phenomenon? --Shantavira|^{feed me} 13:13, 29 June 2007 (UTC)

I can't recommend poking your eye, but what you describe shows that the light sensitive receptors in the retina on the inside of the eyeball are also sensitive to pressure and produce Phosphenes. A professor once said that pressing on the eyeball could cause damage, but I don't have a source and we cannot give medical advice. Why do you see a spot at the left when you push on the right side of the eyeball? remember that the eye. like a camera, or a lens, makes an image that is upside down and backwards on the retina, so the right side of the retina "sees" things that are on the left. The "wiring" in the optic nerve and brains is such that we see things correctly. Edison 14:37, 29 June 2007 (UTC)

I've heard that pressing on your eye can briefly change its shape enough to improve performance on an eye exam. Again, definitely not recommended though. Dragons flight 14:42, 29 June 2007 (UTC)

I suspect that pressing on your eye changes its shape, causing some of the light passing into your eye to be focused somewhere other than your retina, causing a dark spot in your vision. I may be wrong, I have wondered this myself in the past.-RunningOnBrains 18:15, 30 June 2007 (UTC)

What's up with lightning?

I heard from a rather unreliable source that lighning today is stronger than it ever was before. I laughed at the time, but it got me thinking...

66.155.141.135 14:17, 29 June 2007 (UTC)

[2] says that a 1999 study found, based on 3 years of observations, that with "a 1°C increase in global wet-bulb temperature there is a 40% increase in lightning activity, with larger increases over the Northern Hemisphere land areas (56%)." But the data do not go back far enough to make me confident and clearly more recent data and analysis would be needed. Weather services installed a network of electromagnetic lightning detectors about 40 years ago [3] , which allow them to record the location, polarity, and intensity of lightning strikes in the US. An accurate computerized system went in service in 1991[4] to replace earlier less accurate manual plotting. The cited source says that the strokes which cause fires are the 20% which are positive, and of those the lower intensity, longer duration ones are the major starters of forest fires. [5] is a live plot of lightning in the UK. The data exist to say whether the number and intensity of lightning strikes in the US is greater or lesser than when the network was put in service, but I haven't heard one way or the other. Data about the intensity of selected strikes, and the number of strikes st selected locations, (like the Empire State Building), and high voltage electrical lines and facilities, goes back for several decades, but again I don't know what trend they show. I know the number and intensity of lightning strikes varies wildly from day to day and year to year, so a seeming trend might be spurious and just part of normal variation. [6] is a global satellite lightning detection system which went in service in 1997, and the site says "The global lightning flash rate is on the order of 40 flashes per second (fps) as compared to the commonly accepted value of 100 fps, an estimate that dates back to 1925." Of course they had no satellite in 1925 so that figure was a pretty wild guess. This would allow trend tracking as we go forward, but an accurate large scale baseline does not go all that far back.[7] is an interesting plot of lightning frequency worldwide. Lots in some areas, very little in others, such as Europe. Edison 14:52, 29 June 2007 (UTC)

You can WATCH live lightning strikes detected on radio receivers! Most of these stations are located in Alaska, but they detect lightning strikes from all over the planet, because signals can travel very far via the skywave effect. Large vertical lines in these graphs indicate lightning strikes, and horizontal lines typically indicate AM navigation beacons. Nimur 17:01, 29 June 2007 (UTC)

Interestingly, the highest concentration of lightning in the world is in central Africa. -RunningOnBrains 00:47, 4 July 2007 (UTC)

Liquid metal technology

I need to have as much as information on Liquid metal tecchnolgy as possible. Its very less available on Wikipedis itself and on internet. Plz help me in that. Thanks

What happened when you searched Wikipedia for "liquid metal"? I just tried it and got an interesting page about liquid metal. Is that page not clear, not enough info, too advanced, or some other problem? The phrase "liquid metal technolody" can have many meanings, hard to provide specific info without knowing what meaning you have in mind. DMacks 15:59, 29 June 2007 (UTC)

Maybe you could read the Mercury (element) article? It is a liquid metal at room temperature and it can be used to make mercury thermometers. Nimur 17:04, 29 June 2007 (UTC)

Me, I assumed he was talking about the technology behind the T-1000. --Steve Summit (talk) 23:39, 29 June 2007 (UTC)

Which, to make the point explicit, is entirely fictional. --Anonymous, June 30, 2007, 01:30 (UTC).

What is this plant?

Hi

I have taken a photo of a plant in my garden in Surrey, EnglandDp1st 18:23, 29 June 2007 (UTC) which can be viewed here: http://en.wikipedia.org/wiki/Image:Exoticplant.jpg

Can anybody tell me what this plant is. I've never seen one like it before.

Thanks

David Furst

Looks like some kind of anthurium.--Shantavira|^{feed me} 18:49, 29 June 2007 (UTC)

I think it is Dracunculus vulgaris, known as the Voodoo Lily, Dragon Lily or Dragon Arum. It is native to the Mediterranean and a member of the Araceae (Aroid Family). Anthurium is also an aroid. The family is distinguished by the unique inflorescence consisting of a spathe and spadix. Very peculiar. --Eriastrum 15:37, 30 June 2007 (UTC)

How to explain holding a balloon in an air stream?

A friend of mine asked me if I know the reason why a balloon can be suspended oscillating slightly up and down in a constant air stream. For example, if you place a fan pointing at an angle up, and a balloon at just the right distance in the air flow, the balloon will be suspended relatively in place in midair even when the fan isn't pointing straight up. I've seen a similar demonstration at a science museum where a person moved a dodgeball around in midair using a nozzled leaf blower.

I wasn't sure what the exact mechanism is, though. I think it's related to the Bernoulli Effect or the Magnus Effect (as the balloon moves in the air flow the velocity and hence pressure of the air around the balloon is different on different sides), but I was looking for a more detailed explanation. Thanks! Dugwiki 20:02, 29 June 2007 (UTC)

Consider the fan-pointing-up case: the way it works is that when the balloon starts to drift to the left, say, the air on the balloon's right will cling to its right side (due to the Coandă effect), snake around the top of the balloon, and then jet off to the left. While doing so, the air pushes back on the balloon's right side, so imparts a rightward force which will send it back to the center.

Coanda effect as demonstrated with a spoon and a water stream.

Consider the spoon at right. As the water jets off to the left due to the Coandă effect, a (tiny) equal and opposite force pushes the spoon to the right.

Here's a blurb about it from the author of the *wonderful* book "The Flying Circus of Physics", which has several hundred answers to questions along these same lines. --TotoBaggins 20:55, 29 June 2007 (UTC)

Such a device is commonly known as a Bernoulli blower (wot, no article?). A Google search comes up with quite a few interesting articles about them... Laïka 23:51, 30 June 2007 (UTC)

Yeah, like everybody said, it's the Bernoulli Effect. Short explanation; Bernoulli proved that moving air has lower pressure than still air, so the balloon is trapped in the moving airstream. (Look at a vacuum cleaner for another example) Gzuckier 16:02, 2 July 2007 (UTC)

Can tooth enamel be restored?

A brand of toothpaste claims "Liquid calcium (r) technology fills in tooth surfaces to naturally restore lost surface enamel for whiter teeth". Comparing the list of ingredients with another toothpaste suggests that the active ingrediants are calcium sulphate, sodium carbonate, and possibly dipotassium phosphate - which seem to be plaster of paris, washing soda, and fertiliser.

Is this just a gimmick or is there any scientific support for this claim please? 80.0.109.226 23:20, 29 June 2007 (UTC)

See tooth enamel -- Kainaw^(what?) 23:29, 29 June 2007 (UTC)

Does anyone remember the toothpaste ad in the UK that claimed that the stuff advertised worked by splitting water molecules during brushing and releasing 'active oxygen' into the mouth for a deeper clean? That was probably the clearest example of 'bollocks science' I've ever seen in an advert - even moreso than some of the claptrap that the hair and skincare ads come out with. --Kurt Shaped Box 23:47, 29 June 2007 (UTC)

I have read the article on tooth enamel and it does not answer the question. The same toothpaste company is now advertising a slight variation on "liquid enamel" which is now said to be "zinc activated". As tooth enamel naturally thins and cracks as you get older (one of the reasons why younger people have whiter teeth) then it would be great if it could in truth be restored.

I believe the article clearly states there is no way currently to "regrow" enamel. - Dozenist talk 02:14, 30 June 2007 (UTC)

I cannot see where in the article it says that. In addition, its not true. As my experienced and highly-qualified NHS dentist told me some years ago, that used to be what was thought, but more recently it has been found that teeth can naturally repair small (probably very small I imagine) amounts of enamel damage, which was why she was not being so gung-ho with the drill as previously. In fact the article on Fluoride therapy says "The presence of this fluoride in turn attracts other minerals (such as calcium), thus resulting in the formation of new tooth mineral", implying that tooth enamel can increase. Whether "liquid enamel" is a gimmick or not is another matter. Looking in a supermarket this morning found another variant of the same "liquid enamel" toothpaste, so its got at least three different formulations. 80.2.194.68 10:15, 30 June 2007 (UTC)

Though Dozenist says he is a dentist, and I'd hate to argue this with a dentist, I too had heard from reputable sources (including my own dentist on my last visit a month ago) that it is possible to reverse minor damage before cavities form with careful, thorough brushing. Perhaps this is a different thing than regrowing enamel? --jjron 12:11, 30 June 2007 (UTC)

The article, under the "Development" section says: "At some point before the tooth erupts into the mouth, but after the maturation stage, the ameloblasts are broken down. Consequently, enamel, unlike many other tissues of the body, has no way to regenerate itself. After destruction of enamel from decay or injury, neither the body nor a dentist can restore the enamel tissue." So, enamel cannot regenerate. Fluoride can help slow down the demineralization process in enamel from tooth decay. That does not "regrow" enamel, but it does help reverse tooth decay *if* the decay is really small (meaning it has not actually created a cavitation in the tooth and reached the dentin). - Dozenist talk 00:43, 1 July 2007 (UTC)

OK, I thought something like that may have been the case, and seemed to fit with what else I'd heard. So you can get very minor repair I suppose you could call it, but not actual regrowth. --jjron 11:27, 1 July 2007 (UTC)

Yep, exactly. - Dozenist talk 12:07, 1 July 2007 (UTC)

Shaggy cows?

Just seen the picture of the highland cow above. Question. How on earth is the cow able to see where it's going with all that hair hanging down over its eyes? I suppose that I could ask the same thing about dulux dogs... --Kurt Shaped Box 23:35, 29 June 2007 (UTC)

I guess they can see through the thatch adequately for their needs, i.e. "there's some grass, there's another cow, oh there's a rambler...." Now you know why bull-fighting never really took off in the Scottish Highlands.--Shantavira|^{feed me} 07:05, 30 June 2007 (UTC)

Oh I've had my hair like that, it's not a big deal. It's kinda like when you're taking off a t-shirt, and it gets so close to your eyes you can see through it, except even more transparent. It's nature's sunglasses! --_ʇuǝɯɯoɔɐqǝɟ 10:23, 30 June 2007 (UTC)

It's like net curtains, where you can see out, but not in.

Actually, looking carefully at the picture, it looks like it's eyes aren't actually covered by the hair. Being a herbevore, its eyes are on the sides of its head, where the hair is slightly shorter.

Exactly. Cows don't really "see where they are going", which is why things get trampled in a stampede. They are much more interested in seeing who is coming. Gzuckier 16:03, 2 July 2007 (UTC)