The universe’s evolution seems to be slowing and we don’t know why

There may be something wrong with our models of the cosmos. The matter in the universe is getting clumpier and clumpier over time but it appears to be happening more slowly than expected. This slow-down in the evolution of the large-scale structure of the universe could point to new particles or fields, or it could indicate that our understanding of dark matter isn’t quite right.

The evolution of the universe is largely governed by the push and pull of two competing forces …