Zel'dovich equation

The Zel'dovich equation describes how small initial irregularities in matter distribution in the universe evolve over time due to gravity. It predicts how regions with slightly higher density grow and eventually form structures like galaxies and clusters. Essentially, it models the early stages of cosmic structure formation by showing how matter moves from a nearly uniform state into complex large-scale formations, helping scientists understand the universe’s evolution from a hot, uniform early state to the structured cosmos we observe today.