Expanding Universe: Cooling Matter, Gravity & Isotropy

[muser]

in an expanding universe is all matter cooling? also, is has gravity become weaker over large distances? does isotrophy apply to the natural forces?

 

[Chronos]

In an expanding universe, the average energy density decreases over time. But this decrease is over all of spacetime, it does not affect matter. So, distant stars do not 'cool' over time, just the space in between. Similarly, gravity does not change, it merely diminishes as distance increases. 'Isotrophy' has nothing to do with the 'natural forces'.

 

[muser]

In an expanding universe, the average energy density decreases over time. But this decrease is over all of spacetime, it does not affect matter. So, distant stars do not 'cool' over time, just the space in between. Similarly, gravity does not change, it merely diminishes as distance increases. 'Isotrophy' has nothing to do with the 'natural forces'.

the big rip theory suggests gravity will weaken due to acceleration. presumably the other forces as well.