Entropy and time

[Fed]

How I understand it, we define the forward direction of time as the direction that results in an overall increase of entropy for the universe.

Let's say the universe expands forever (doesn't collapse - I believe this is the current cosmological view). When it enters heat death, does time as a concept have any meaning?

 

[arunma]

Yes...sort of. At the quantum level, things still happen, so time would have some meaning even in a heat death. Not that it would really matter on a larger scale.

 

[Fed]

What do you mean by stuff happening at the quantum level? You're referring to the uncertainty principle?