do you believe in it? more importantly, if yes/no, what’s the reason why / why not?
i have had a great number of very enjoyable discussions with people about this topic. some say that it is unknowable what the eventual fate of the universe will be, because we can never have experimental confirmation that things will keep on moving forever, unless we wait for the end of the universe, which will never come (or at which point the knowledge would be useless).
however, i keep thinking that cosmic expansion will lift things out of a gravitational potential over time. i’m assuming that we’re all inside a big black hole (the whole universe is a black hole as an object with the mass of the entire observable universe just so happens to have a schwarzschild diameter of about the diameter of the entire observable universe). as the universe expands, its density decreases, therefore its schwarzschild radius decreases and we will eventually leave the black hole without doing anything for it; this obviously adds energy to the system.
or, in case cosmic expansion does not continue exponentially (but slows down over time), then the laws of physics would change over time; then, according to noether’s theorem, we could extract useful energy out of that change of laws over time. also black holes could grow to infinite size simply feeding on cosmic microwave background radiation continuously in this case¹. which we could use as an energy source.
[1]: do the differential equation, you get dM/dt ∝ M²·u₀/a(t) where M is the mass of the black hole, M² is proportional to the surface area, a(t) is the scale factor, and u₀ is the CMB density at current time. If a(t) is less than exponential, i.e. less than exp(Ht), then M(t) diverges in finite time for any black hole with big enough start mass.
sorry for such a verbose post :)
I read some time ago a mathematical proof, or rather an article claiming so because I don’t know enough neither math nor cosmology, supporting my own old intuitive concept that once heat death is complete and all matter has stopped moving and there is an eternity ahead of still nothing, it is by all relevant means identical to a singularity of potential energy.
I don’t know if I believe in it, but I think it makes sense. Even if it takes an eternity or two for a new cycle to start over.
Edit: I mean all of it is speculation anyway. We have and will never have any insight in the “true” nature of the universe beyond our limited measurements and deductions. It could be just what it looks like and there is only one. There could be a finite or unlimited number of multiverse, or a numeral concept beyond what we can comprehend. This could all be an illusion, a simulation, or a super organism of which we are part of or we could be microbes on it. In the end it doesn’t even matter really. But it’s fun to think about.