eli5 – if photons have no mass, how can they be used to push hypothetical “solar sails”?

Question

eli5 – if photons have no mass, how can they be used to push hypothetical “solar sails”?

In: 20

Answer 1

We think that only things with mass can push when hitting something because we are used to everyday interactions with massive objects, including ourselves. Turns out photons can pack some punch too, because they have energy, and Einstein proved that energy is equivalent to mass in a certain sense which is what his famous equation (E = mc2) is all about. The more energetic a photon is (the shorter its wavelength) the more push it has to give.