## Wednesday, November 4, 2015

### vacuum fluctuations

what's wrong with this argument? a moving observer would see quantum fluctuations in e.g. the electromagnetic field blueshifted from the forward and redshifted from the backward direction and would be able to determine the velocity by the amplitude of the motion dipole.

1. The energy density is proportional to the cube of the frequency. Such a spectrum has the property that it is invariant under redshift. (Note that this dependence follows naturally from the derivation and is not postulated in order that the radiation be Lorentz-invariant.)

2. Interestingly, while one cannot detect uniform motion, one can detect acceleration, since an accelerated observer will observe Unruh radiation.