Dark energy takes over
Five billion years ago the expansion of the universe stops slowing down and starts speeding up.
- When
- Known to
- ± 500 million years
- Era
- Enrichment, Stelliferous
For most of cosmic history gravity decelerated the expansion. As matter thinned out, the constant energy density of empty space came to dominate, and around redshift 0.5 the expansion began to accelerate. Type Ia supernova surveys detected this in 1998 and it won the 2011 Nobel Prize in Physics. Dark energy is roughly 68% of everything, and what it actually is remains unknown.