From a reader, subject header: “Solar Sailer Rebuttal”:
In case you cared…
Carnot law does not say that the temperature must go down…it says that the entropy of the universe must go up. For thermal systems, there is a temperature driven maximum efficiency. For non thermal systems, there is no such limitation, hence fuel cells, which use gibbs free energy to calculate efficiency versus carnot efficiency, have very high efficiency rates. Photons reflected from a solar cell (due to compton scattering) are at a lower energy … Energy of photons e=hv (where h is planks constant and v is frequency) and E=mc2 (where E is energy, c is speed of light and m is mass, photons have relativistic mass = hv/c2 since momentum p is = mass x speed , thus hv=pc..h and c are constants, so if p goes down (loss of momentum, and momentum is always conserved) v (frequency) must go down, and energy was hv, thus energy went down. Since energy was transfered, the future usefulness of the reflectant photons goes down, and thus entropy of the universe goes up. The photons cannot possibly transfer more momentum than the difference between current momentum (which was reduced by the solar cell) and the momentum due to brownian motion of the interstellar hydrogen (about 3K)with which they must be discharged. The crookes radiometer is consistent, since the mirrored surface encounters much less compton scattering it reflects most photons at a higher energy (thus on that side less momentum is transfered) than the black side which absorbs the high energy photons (visible light) and emmits lower energy photons at near infrared (it will heat up more). Thus the black side is absorbing more energy, and hence transfering more momentum, so the net moment arm pushes forward on the black side.