How does light have energy? How can light exert force?

Question

Here is what I know:

Photons have no mass.

Force is change in momentum over change in time.

Momentum is mass times velocity.

E=mc²

SO HOW DOES LIGHT HAVE ENERGY AAAA

I also read that massless particles can have momentum and I do not understand that at all.

Please explain how all of this is connected and how light has energy and exerts force. Thank you!

In: 9

Answer 1

Since this is ELI5, not askscience, here we go.

Newtonian physics is great. Until you get into particle physics. Then it starts to fall apart. That’s where special relativity comes into play.

You need to stop thinking of mass as something other than another form of energy. Thinking about it, being able to convert between energy and mass makes sense, right? Well, of they were fundamentally different, it wouldn’t make sense to be able to convert between the two. So instead of thinking about momentum being strictly mass, think of it as energy. Photons don’t have mass because all of their energy is in the form of motion. Therefore, their momentum is derived from their energy, not their mass.