Don't tell that to Mr. Photon.
Ever shine a flashlight into vacuum jar and start an aluminum vane spinning around?
Please explain?
Those toy radiometers have nothing whatsoever to do with radiation pressure, are not in a vacuum and spin counter to the direction of radiation pressure.
The vanes have one side white and the other dark. If the mechanism were radiation pressure, the light recoiling off the white side would exert twice the radiation pressure experienced by the dark side absorbing them. The mechanism is heat, they are tiny heat engines, the dark side is warmed more by the light than the white side and the heated air molecules carry off more momentum on the dark side than the light.
Radiation pressure is also expected from Maxwell’s equations and is consistent with E= mc2. See the wiki link in my post above for Einstein’s correct derivation.
It always bugged me when physicists use the figure of speech that photons have no mass. They have energy, and any 9th grade algebra student can prove then that a photon’s mass = E/c^2. Maybe in theory if a photon could be brought to rest it would have no mass, but then it would still have relativistic mass since it is at rest only relative to something else. And while we’re at it, I wish ‘they’ would make up their minds and let us know if gravity is really a force or just an effect of curved space. ‘They’ seem to try to have it both ways on that one all the time too.
And that effect is cause by the heating of the vane not anything else....Lord you know so little fundamental science