Cosmic web

This graphic shows the emergence of a cosmic web in a cosmological simulation using general relativity. From left, 300,000 years after the Big Bang to right, a Universe similar to ours today. The dark regions are void of matter, where a clock would run faster and allow more time for the expansion of space. The lighter purple regions are denser so clocks would run slower, meaning under the "timescape" model of cosmology that the acceleration of the Universe's expansion is not uniform.