In Feynman's book Six Easy Pieces, his chapter on Atoms in Motion describes how gas in a container with a piston behaves. He demonstrates via a figure (1.3) that if the piston is slowly moved to compress the gas, the temperature of the gas will rise. Keep in mind that higher temperature = increase in motion. The reason for this result is that as gas molecules collide with the piston which is moving downward (i.e., toward the gas), the piston imparts a net gain in speed to each molecule (thus increasing the motion, and therefore the temperature, of the molecule and the gas as a whole).
If I haven't been very clear, then you better get a copy of the book! Feynman does it much better.
(By the way, the converse is also true-- if you pull the piston away from the gas, the gas will become cooler for the same reason-- when a molecule of the gas collides with the piston moving away, the speed of the piston must be subtracted from the speed of the molecule.)
[This material has all been a review of what George and I talked about several lunches ago, when we first began reading the Feynman book. I've provided this as a background for George's topic today!]On with the story...
George was telling me that in an air-conditioning system (or, I suppose, any refrigeration system), a gas is contained in a chamber, but some of the molecules escape (are pushed???) through a VERY tiny opening into a larger chamber, where the pressure is much lower. I assumed when he was telling me all this that the second chamber must get pretty cold and that's what is used to cool stuff down (air, etc.).
George points out that even though the molecule has escaped into a lower-pressure chamber, it should still be moving at the same speed. that means the same energy, and the same temperature. So how does it get cold???
I mentioned a great two-volume set of books called The Way Things Work by C. Van Amerongen, thinking that a deciption of a refrigeration system might be found there... but George correctly pointed out that these books (which, it turns out, he owned when he was but a lad) most likely only describe how it works mechanically, paying no mind to the underlying physics. Bummer. They're great books, though! Here's a testimonial by at least one of my favorite authors: Long after I had purchased my copies, I was reading Lucifer's Hammer, by Larry Niven & Jerry Pournelle. After a comet strikes the Earth, an aging science professor is forced to leave his home and can only save a handful of the books from his extensive personal library... and he makes sure that volumes 1 and 2 of The Way Things Work are among them!
Oops... I digress... back to the Gas Temperature story:
The bottom line: We Don't know! I guess we better look this up somewhere. If anyone else knows, please send e-mail!
George told me about another show he saw on The Learning Channel (TLC) called Junkyard Wars. Whoa-- this sounded interesting!
Here's the setting:
George noted that even though there were components such as engines, axles, and wheels to be had, few if any of them were readily compatible. This forced the teams to use cutting and welding torches to modify such components so they could be used together. Not only were they busy at work with their tools, but also with a chalkboard where they created the design for their creations! Naturally, one of the hazards with which they had to deal was a "reporter" with a mocrophone who not only asked questions about what they were doing, but also shared this information with the opposing team!
According to George, the competition did not dissappoint. Both teams produced functioning tractors which seemed very equally matched, and only mechanical failures led to one tractor pulling the other past the boundary.
Sounds like a cool show. I went to the official web site, and discovered (ha! It's part of the Discovery Channel) that they are about to begin the fifth season of this show! Check it out.
Before diving into the relativity stuff, I need to share the following quotes from the two Physics authors I'm currently reading:
"The universe should look essentially the same at all scales."
-- Tom Van Flandern
"Things on a small scale behave nothing like things on a large scale."
-- Richard P. Feynman
George and I talked about Dr. Tom's 8-page essay on GPS clocks (it actually appeared as a chapter in the book Open Questions in Relativistic Physics). the full text is at http://www.metaresearch.org/cosmology/gps-relativity.asp.
Here are some interesting points:
The current issue of Scientific American is a special issue with a majority of the articles dedicated to nanotechnology. I purchased two copies-- one for me, and one for George!
The issue includes an article by K. E. Drexler, the author of Engines of Creation (read the complete text here), and an opposing piece by Richard E. Smalley in which he argues that Drexler's view of nanotechnology will never become reality.
There is even a story about the surge in Science Fiction novels based on nanotech. It discusses elements of Neal Stephenson's nanotech novel The Diamond Age.
George and I plan to read the articles and discuss them in two or three weeks.
In the meantime, you can check out the people Scientific American label as "Fringe Element Futurists" at NanoTechnology Magazine. Then, to see just how early one of our great minds imagined nanotech, read Richard P. Feynman's essay Plenty of Room at the Bottom.