if photons in motion have mass and energy why don't they knockstuff over

In article ,
Bjoern Feuerbacher wrote:

4B wrote:
What about those small propels that "mysteriously" spin when they are put
close to a source of light. Is not the momentum of the photons that make
them spin?

1) Don't top-post, please.
2) *Lots* of photons are acting there together.
3) You need an apparat with very few friction forces for this to work.
4) It is constructed especially to maximize the effect, by making one
side black and the opposite one light-reflecting.

Bye,
Bjoern



Indeed!

And if the radiometer (the small propeller thingie) has a vacuum inside
the glass bulb, the propeller spins in one direction, but, if the there
is air inside, it spins in the other direction.

--
Rudy Garcia