# Curvature of the universe

by zeebo17
Tags: curvature, universe
 P: 41 How has the curvature of the universe changed with time? I know that the universe is observed to nearly flat at the present time and that inflation was proposed (one of the reasons) to drive the universe to be almost perfectly flat. Do we have any idea what $$\Omega$$k could have been like before inflation and how it changed during inflation? Thanks!
 Quote by zeebo17 How has the curvature of the universe changed with time? I know that the universe is observed to nearly flat at the present time and that inflation was proposed (one of the reasons) to drive the universe to be almost perfectly flat. Do we have any idea what $$\Omega$$k could have been like before inflation and how it changed during inflation? Thanks!
Basically, the curvature portion $$\Omega_k$$ changes with the energy density as $$1/a^2$$. So if, for instance, you are matter dominated, as matter dilutes as $$1/a^3$$, as the universe expands curvature becomes more and more important. By contrast, during inflation, our universe was dominated by some stuff that acted much like a cosmological constant, which means its energy density was nearly independent of the expansion. So as the expansion progressed during inflation, the curvature diluted away as $$1/a^2$$. As a result, we can't really know what it was before inflation began, as inflation set it to be nearly identically zero due to the massive increase in $$a$$ during that time.