In reply to David Roberson's message of Thu, 28 Feb 2013 16:44:14 -0500 (EST): Hi Dave, [snip] >Because it is just wrong! Kidding Robin. Now I am confused a bit, are you >calculating that if I displaced an atom by a tiny amount and let go of it that >it would begin to vibrate at that frequency as the energy damped out?
Yes. >Maybe so, I was not thinking of that process. I assumed that you were >figuring out the vibrations due to the temperature of the metal. If what you >calculated is accurate then an incoming photon of that frequency would easily >be absorbed by one of the atoms and start it vibrating in place. Precisely. And heat has an appropriate frequency. Most sound waves OTOH do not. In fact they are "off" by many orders of magnitude. Hence my suspicion that this is the reason for the difference in speed between sound and heat in a solid. >Do you have any idea of how high the Q of the resonance would be? You might >find that energy is stolen away by the nearby atoms quickly. I think measuring the speed of heat transport in the solid answers that question, since that's exactly what's happening when heat spreads. I.e. energy is transferred to other atoms. The Q must be pretty high, since the speed of heat spread is usually very low, except in metals where it is also spread by free electrons. > > >It would be interesting if you could calculate a similar resonant frequency >for the motion of just the nucleus. >Displace it slightly and allow it to wiggle back and forth within its electron >cloud that is somewhat confined by the atoms surrounding it. 99.975% of the mass of an atom is in the nucleus, so this *is* essentially what I calculated. Since the nucleus is effectively suspended friction free in a mesh of electric fields (think springs), that explains why the Q is so high. >I wonder if a free atom in space exhibits a resonance of this nature? One >might think that in free space that the electrons would compensate for the >nucleus movement so quickly that it would immediately radiate the energy. [snip] Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
