On Fri, Jul 04, 2003 at 01:47:11PM +0100, William T Goodall wrote: > http://www.newscientist.com/news/news.jsp?id=ns99993895
If I've understood Gold correctly, it seems to me that he is saying that a single photon has a temperature that obeys thermodynamic laws, but a photon does NOT have momentum that obeys conservation of momentum laws. Gold repeatedly mentions "pefect mirrors". That raises my skepticism, since I think that an atomic or sub-atomic viewpoint is more reliable than talking about general thermodynamic laws and perfect anythings. On a lower level, the photons are interacting with the atoms in the sail. When Gold talks about a "perfect mirror", then he is talking about a specific type of interaction where the photon is presumably absorbed by a sail atom(s) and re-emitted in the opposite direction with no transfer of energy. I'd like to see him go into the physics of such an interaction and how it differs in the conventional interpretation vs. his interpretation, rather than waving his hands about thermodynamics and perfect mirrors. Then perhaps it will be clear how to reconcile the phenomenon with thermodynamics. Thermodynamics is extemely useful, but it is a "high-level" theory that tends to "ignore" many details. So, I'll predict that quantum mechanics (momentum of photons) and conservation of momentum are the more straightforward interpretation here, and there is something wrong with the thermodynamic interpretation. That's really just an intuitive guess, though. I'll be anxious to see the experimental results. -- "Erik Reuter" <[EMAIL PROTECTED]> http://www.erikreuter.net/ _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
