Photons have zero rest mass, but energy itself has a gravitational effect too. It's even theoretically possible to create a black hole entirely out of light htt

Photons have zero rest mass, but energy itself has a gravitational effect too. It's even theoretically possible to create a black hole entirely out of light https://en.m.wikipedia.org/wiki/Kugelblitz_(astrophysics) https://en.m.wikipedia.org/wiki/Kugelblitz_(astrophysics)