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

Indeed, photons have no mass but they have energy and it this energy (and momentum) that push the solar sail forward.

As for adding weight to earth, that happens when light is converted to chemical energy via the way of photosynthesis from plants, which “traps” the energy in chemical form, which has mass.