Thermodynamics doesn't scale downward

Post #45,989 by marlowe 7/18/02 3:10:45 PM Reply	Thermodynamics doesn't scale downward [link\|http://news.bbc.co.uk/hi/english/sci/tech/newsid_2135000/2135779.stm\|It's a macro level thing] Excerpt: Professor Denis Evans and colleagues at the Research School of Chemistry at the Australian National University put 100 tiny beads into a water-filled container. They fired a laser beam at one of the beads, electrically charging the tiny particle and trapping it. The container holding the beads was then moved from side to side a thousand times a second so that the trapped bead would be dragged first one way and then the other. The researchers discovered that in such a tiny system, entropy can sometimes decrease rather than increase. This effect was seen when the researchers looked at the bead's behaviour for a tenth of a second. Any longer and the effect was lost. [link\|http://www.angelfire.com/ca3/marlowe/index.html\|http://www.angelfir...e/index.html] Everything's a mystery until you figure out how it works. Free Joel Mowbray! I'm a-gonna put a gun rack on my SUV.
Post #46,047 by tablizer 7/19/02 1:19:17 AM Reply	If I find lots of tiny monkeys with tiny typewriters..... The article did not say what the bead(s) did that was indicative of something unexpected. Quantum phyz is really really funky sh8t. The government might just start banning it on airplanes. ________________ oop.ismad.com
Post #46,056 by ben_tilly 7/19/02 6:31:02 AM Reply	This is no surprise to me What is this "a few years ago" bull? Thermodynamics is based on a statistical principle, and statistics work better the more stuff you have to apply it to. Cheers, Ben "... I couldn't see how anyone could be educated by this self-propagating system in which people pass exams, teach others to pass exams, but nobody knows anything." --Richard Feynman
Post #46,295 by neelk 7/21/02 2:35:15 PM Reply	What makes it surprising... ...is the scale of the system they observed the effect in. Since the second law is a statistical law, in small-number systems you'd naturally expect to see it break down once in a while. But this particular experiment featured latex beads a few microns in size, suspended in water. Relatively speaking, these are huge objects, comprised as they are of tens of billions of atoms. The sorts of naive counting argument that have indeed been around since the 19th century would say that seeing any kind of fluctuation on this size scale would be extremely unlikely. You need some substantially fancier math to get a more accurate estimate, and this is apparently what was invented around 10 years ago. Having experimental confirmation of the theory is very important too, because it may mean that cell biologists will have to update their models: cells are on the same size scale as the objects the physicists studied. Mesoscale physics is on a much bigger length scale than we thought!
Post #46,301 by ben_tilly 7/21/02 4:23:31 PM Reply	Thanks for the clarification But from the popularized article it looked to me like the billions of particles are a red herring. Rather what matters is the relative motion of the hundred particles that they watched. Did something get lost in the popularization? How did they measure the entropy of the system? Thanks, Ben "... I couldn't see how anyone could be educated by this self-propagating system in which people pass exams, teach others to pass exams, but nobody knows anything." --Richard Feynman
Post #46,310 by Ashton 7/21/02 7:49:44 PM Reply	Heh.. how do we 'measure' the entropy of the Cosmos (?) It would appear that the imaginary line between micro and macro is neither fine nor broad - but entirely situational (too). Unless we imagine we shall score a lateral arabesque around that ol Debbil - the effects of the Observer (?) or in present case: the light energy to watch those small balls. hmmmm maybe ~ menstrual cycle simile at work elsewhere.. Games are fun though; you can always construct a New one. :-\ufffd
Post #46,354 by neelk 7/22/02 9:23:17 AM Reply	Re: Thanks for the clarification The reason that billions wasn't a red herring was because an individual bead in the water was getting a useful work from the thermal kicks the surrounding water imparted to it. This means that the relevant number is the number of water molecules striking the bead at each moment. I'm not sure how they did the measurements, because I was only able to find the abstract, and a short note in the AIP Bulletin. I probably wouldn't be able to understand them anyway, since my physics degree is now 5 years old. :) [link\|http://link.aps.org/abstract/PRL/v89/e050601\| [link\|http://link.aps.org/abstract/PRL/v89/e050601\|http://link.aps.org.../v89/e050601] ] [link\|http://www.aip.org/enews/physnews/2002/split/598-1.html\| [link\|http://www.aip.org/enews/physnews/2002/split/598-1.html\|http://www.aip.org/...t/598-1.html]]
Post #46,430 by ben_tilly 7/22/02 7:59:48 PM Reply	Hey, at least you have a physics degree Me, I am an interested amateur who skipped the minor when I realized that if I didn't get the minor then I could avoid taking thermodynamics from one of the worst teachers I have had the displeasure of meeting. As for the description, that does sound more suprising than what I assumed. Cheers, Ben "... I couldn't see how anyone could be educated by this self-propagating system in which people pass exams, teach others to pass exams, but nobody knows anything." --Richard Feynman
Post #46,814 by deSitter 7/25/02 10:13:00 AM Reply	What Happens... ..if you take into account the entropy of the EM field between the manually charged particles? The presence of essential EM is critical. For example, in the simple case of fast moving electrons, it doesn't appear that action=reaction unless you take into account the energy and momentum stored in the field. I am deeply skeptical of this claim. By its very nature, it is monotonic and must be to provide the necessary dual statement to energy conservation. The principles of thermodynamics are ultimately projective and not metric. -drl

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