4 ms·

I took away from that example that, even though unitarity clashes with cosmology to an extent, you can’t just naively break it or you get “even worse” paradoxes

by alecst 4y ago

I took away from that example that, even though unitarity clashes with cosmology to an extent, you can’t just naively break it or you get “even worse” paradoxes like this one. Plus, conservation of energy doesn’t apply to the universe as a whole, if it’s expanding (space has energy.) The assumption which is being violated by adding the single photon is really unitarity and not the laws of thermodynamics. (But it’s been a while since grad school for me, could be wrong here.)

hinkley 4y ago
> Plus, conservation of energy doesn’t apply to the universe as a whole, if it’s expanding (space has energy.) I don’t believe that, but we either may never be able to prove it, or discover we live in a bubble of space where physics has different properties. We don’t know where the space is “coming from”. It’s the same problem laypeople have with the Big Bang Theory. Well where did the Bang come from? What happened before? There is no Before. The Bang and Time were born together. We may well find that we live inside a black hole. The space inside a black hole grows. One theory says that infinite curvature means it grows at the speed of light. If we live in a black hole then perhaps the energy to create the additional space is coming from outside, our “experiments” are not within a closed system, and look like Free Energy but are not. Or maybe we live in a physics bubble where different rules apply. Which might solve the whole, “how will we ever explore this Universe in time?” ‘dilemma’ because any ship we send outside that bubble starts to disassemble itself. The floor is lava.
- alecst 4y ago
  Energy is guaranteed to be conserved if the Hamiltonian has time symmetry. The Hamiltonian of the universe may not have that property, and probably doesn’t. You can Wikipedia Noether’s theorem for more info.

by alecst 4y ago

hinkley 4y ago

> Plus, conservation of energy doesn’t apply to the universe as a whole, if it’s expanding (space has energy.) I don’t believe that, but we either may never be able to prove it, or discover we live in a bubble of space where physics has different properties. We don’t know where the space is “coming from”. It’s the same problem laypeople have with the Big Bang Theory. Well where did the Bang come from? What happened before? There is no Before. The Bang and Time were born together. We may well find that we live inside a black hole. The space inside a black hole grows. One theory says that infinite curvature means it grows at the speed of light. If we live in a black hole then perhaps the energy to create the additional space is coming from outside, our “experiments” are not within a closed system, and look like Free Energy but are not. Or maybe we live in a physics bubble where different rules apply. Which might solve the whole, “how will we ever explore this Universe in time?” ‘dilemma’ because any ship we send outside that bubble starts to disassemble itself. The floor is lava.

alecst 4y ago
Energy is guaranteed to be conserved if the Hamiltonian has time symmetry. The Hamiltonian of the universe may not have that property, and probably doesn’t. You can Wikipedia Noether’s theorem for more info.