# How did gravity exist before mass?

I'm brushing up on my Big Bang, and I noticed that, apparently, although gravity is the first force to split from the original "superforce", mass does not appear on the scene until after the second force (strong interaction) has split form the superforce. I understand that there are some things that need to exist before mass can show up, but how does one understand or even scientifically predict the existence of gravity without the existence of mass, in those early fractions of a second in the universe's life?

• You have to look at the total mass-energy content. There was plenty of energy. – Peter R Apr 22 '16 at 13:23
• But how does gravity affect energy, when there is no mass involved? Relativity states that gravity acts through the distortions in spacetime made by massive objects; no mass, no distortions, right? Or....? – Henry Stone Apr 22 '16 at 13:51

In general relativity, the field equation relates the metric (through the associated curvature tensor) to the stress energy tensor $T^{\mu\nu}$. This can be interpreted as a flux of energy and momentum in spacetime (i.e. integrating $T^{\mu\nu}$ over a spacetime hypersurface, like a three dimensional hypersurface of constant time, tells you the rate at which energy and momentum [i.e. 4-momentum] flows through that surface). $T^{\mu\nu}$ is a sort of generalized mass.