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

You need some energy to push the sail. Things that have mass slow down when they hit the sail. Light doesn’t do that. How much energy light has depends on how much there is and the frequency (a little bit like how fast the wind in the sail is). When the light bouces off a solar sail it has a lower frequency. The light’s colour has shifted a little bit to the outer part of the rainbow.