system
Given the following post, respond as if you're commenting on Reddit:
human
Are galaxies continually getting flatter?

Just like accretion disks, are galaxies destined to get flatter and flatter over time?  Ignoring any kind of galactic mergers etc.
gpt
Generally no. The main reason disks get flatter is that they are dense enough for collisions between particles, which causes them to lose vertical speed and hence drop towards a flat disk. In a galaxy, the odds of even a single star colliding is very small, so the vertical velocity spread doesn't significantly change without a perturbing force.