This has been puzzling me for a while. I know it's more a physics question, but I'd like to thrash this out a bit. I haven't been able to find much satisfying answers on the net.
If photons are massless, how can they "push" a solar sail?
I read that it's due to the fact that although a photon is massless, it has "momentum". And yet "momentum" is mass times velocity. So what's the deal? Are physicists (as usual) having their cake & eating it too?
It would seem to me that if photons have any mass at all, it would have to be an infinite mass - because they are travelling at the speed of light. This seems impossible.
So where does the photon's "momentum" come from?