On Tuesday 23 January 2007 17:41, Henry Baker wrote:
This professor suggests that one can put such a photonic crystal "filter" in front of a "blackbody", and thereby allow only the most energetic photons to leave. _Presumably_, the photons that bounce back into the blackbody exchange energy with the blackbody to reconstitute the classic blackbody radiation spectrum, so that the only photons leaving the blackbody are those with high energies.
This is not a perpetual motion machine of the first type, because energy is conserved, but isn't it a perpetual motion machine of the second type?
Why doesn't this idea violate the non-existence of Maxwell's demon?
Because (I'm guessing; I don't know anything about photonic crystals) it will stop working if the "far" side of the filter is bathed in high-energy photons. So it only works for as long as its operation increases entropy rather than decreasing it. After that, you'll get a net flow of high-energy photons back to the black body. -- g