Dark matter pancake stretches across tens of millions of light-years

Turns out, this dark matter "pancake" stretches across tens of millions of light-years, with huge empty spaces above and below.
Because of how gravity works in this setup, nearby galaxies are drifting away from us instead of getting closer.

This finding could help scientists better predict how galaxies will move

These big empty voids help explain why galaxies move the way they do locally.
As researcher Amina Helmi put it, "I am excited to see that, based purely on the motions of galaxies, we can determine a mass distribution that corresponds to the positions of galaxies within and just outside the Local Group."
Basically, this finding could help scientists better predict how galaxies will move and evolve in the future.