Not to nitpick (I only stumbled upon this recently myself), but the mechanism driving a Crookes radiometer (which I presume is the type you're talking about) is

Not to nitpick (I only stumbled upon this recently myself), but the mechanism driving a Crookes radiometer (which I presume is the type you're talking about) is not photon pressure, but interactions with the low pressure gas in the bulb [1]. [1]: https://en.wikipedia.org/wiki/Crookes_radiometer#Explanations_for_the_force_on_the_vanes https://en.wikipedia.org/wiki/Crookes_radiometer#Explanation...