system
Given the following post, respond as if you're commenting on Reddit:
human
If Time is influenced by gravity does that mean that in the "void space" between two galaxies time will flow really fast, thus making humans and materials age much faster than if they were inside the galaxy?

Sorry if the question is obvious, I´m not a physicist thus I have limited knowledge on the matter. This question spurred from the "if you live on a mountain you will age slower than someone who live at the sea level, since the gravity pull will be greater for the latter". 

Also, could you suggest me some books on the time and relativity theories? I´m shitty at math but I suppose I might understand a book like that anyway... or so I hope.
gpt
Nah the effect isn't very big in galaxies. The gravity field of a galaxy isn't astonishingly strong, it's just spread out over a huge volume. The Sun's acceleration around the Milky Way is a tiny fraction of a fraction of a percent of the gravity you feel on Earth.

You get a small effect close to objects like planets and stars, but even then you only notice it if you're making really accurate measurements - you need atomic clocks etc.

The effects only really get noticeable on a human scale if you're in the vicinity of a black hole (or to a lesser extent, a neutron star). But even then, if you want the extreme time dilation depicted in Interstellar, you need to be pretty much right on top of the event horizon.

When we're doing galaxy simulations in astrophysics, we can actually just ignore time dilation, and most relativistic effects, except for the expansion of the universe. On that scale, the universe does seem to mostly run very close to classical physics, and relativity mostly comes into play in a few extreme circumstances.