redpandaeater t1_j2qj2gk wrote on January 3, 2023 at 5:59 AM

Reply to comment by Aseyhe in How do galaxies move? by modsarebrainstems

Is there anything to suggest why the density wasn't uniform? For example if we consider having particle-antiparticle pairs constantly popping into and out of existence could something like that have been enough perturbation to start things moving?

Aseyhe t1_j2r0e5t wrote on January 3, 2023 at 9:32 AM

We don't know, but the most popular hypothesis is that the density variations originated as quantum fluctuations during inflation (the hypothesized early period of accelerated expansion). They would begin around the Planck scale but rapidly expand due to inflation. This process creates fluctuations over a huge range of scales, as fluctuations created earlier grow larger than later ones, and that matches what we observe.