>>11730140Radiation is considered massless:
"Of course this concept again is incorrect because all types of energy have zero mass. The heated mass as long as it has been supplied by any energy source such as heating or electric potential it radiates an emission spectra in form of light or any frequency as an electromagnetic radiation, but it does not loss any mass. In other clear words, there is no mass loss during radiation."
http://www.mass-energy-e-mbc.com/radiation-mass.htmGravity can affect things without mass as it is the distortion of time and space. Whether something has mass or not is essentially irrelevant. If the very time and space is changed, it can affect even massless things, such as radiation. Due to special relativity, energy and mass are used interchangeably, but photons (which make up waves), do not have a rest mass, but they can have momentum from energy. It is this energy that is affected, but photons are still considered massless anyway.
Think of black holes as a warping of space. Light follows the curvature the black holes create. Mass is not the only thing gravity can affect, so when light passes by the event horizon of a black hole (the radius from a black hole where the escape velocity is higher than the speed of light), the light bends around the black hole. Because the velocity is obviously higher than the speed of light, the light is thus absorbed. That doesn't mean light has "mass" as most people understand it, but it does have energy which can be warped by high gravity's effect on spacetime.
"In general relativity, gravity effects anything with energy. While light doesn't have rest-mass, it still has energy---and is thus effected by gravity.
If you think of gravity as a distortion in space-time (a la general relativity), it doesn't matter what the secondary object is, as long as it exists, gravity effects it."
