if photons are massless, how can it push something like a light sail, and how can sunlight adds weight to earth?

Question

if photons are massless, how can it push something like a light sail, and how can sunlight adds weight to earth?

In: 2

Answer 1

Photons don’t have mass, but they have momentum because they carry electromagnetic energy. The change of direction of this energy is what creates the force that pushes a solar sail.

It doesn’t accumulate though, so the Earth is being constantly pushed away from the sun by a tiny force but it’s not getting bigger because of it.