For the first time, cosmologists have used the full power of Albert Einstein’s general theory of relativity to perform detailed calculations of the Universe’s evolution.
The two groups’ techniques—which break with nearly a century of tradition—could help to settle a controversy over the accuracy of previous, simplified simulations, and could help researchers to interpret the results of astronomers’ increasingly precise observations.
General relativity interprets gravity as the warping of space-time. Soon after Einstein proposed his theory in 1915, others realized that it had dramatic implications on the cosmic scale. Belgian cosmologist Georges Lemaître and others pointed out in the 1920s that a Universe that satisfies Einstein’s theory should either expand or contract. (Meanwhile, astronomer Edwin Hubble and others showed that it was, in fact, expanding.)
But solving Einstein’s equations on a cosmic scale was impossible without making assumptions to simplify the calculations. To reach their conclusions, Lemaître and the other early relativists assumed that matter was uniformly distributed as a continuum across space, rather than being concentrated in stars and galaxies.