# If photons are deflected by a strong gravitational field, then how come photons do not have mass? [duplicate]

It has been proved and showed through experiments that light can be bent by the Sun or any other body with considerable mass. Also light is nothing but photons. So can these photons be attracted by massive bodies if they have no mass?

-

## marked as duplicate by Frédéric Grosshans, mbqMar 29 '12 at 13:52

By Einstein's special theory of relativity, the energy and relativistic mass of a body are related by $E=mc^2$. This works both ways. A massive body has energy, and a body with energy has mass. A photon has energy $h\nu$, so it has (relativistic) mass $\frac{h\nu}{c^2}$. Note that it still has 0 rest mass--rest mass is $\frac{E\sqrt{1-v^2/c^2}}{c^2}$. It will be deflected by gravity, but only a tiny bit (due to its tiny mass). And no, in General Relativity, acceleration due to gravity is not independent of mass as Galileo thought.