Watched an episode of “The Universe” a while back that was about what happens as the universe dissipates and runs out of energy. What matter is left will be so distant that it won’t be able to interact or be converted into energy.
Re your episode of “The Universe,” it’s a ripoff of Asimov’s idea written in the ‘50s, “The Last Question,” one of the most famous sci-fi short stories ever written. See the link in post 32 for an online version.