Gravity actually acts kind of... weird... in an infinitely large uniform universe. You end up with gravity acting like a time-dependent position-independent scaling factor on position. Leonard Susskind goes over the derivation (for Newtonian gravity) in a Cosmology lecture available on youtube [1].<p>1: <a href="https:&#x2F;&#x2F;youtu.be&#x2F;ERjkSbdn6-4?t=53m50s" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;ERjkSbdn6-4?t=53m50s</a>