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> For an infinite universe or multiverse with infinite mass, you'd need infinite energy, right? Given that the current best guess for the geometry of the unive
by BlackFly 8y ago
> For an infinite universe or multiverse with infinite mass, you'd need infinite energy, right?
Given that the current best guess for the geometry of the universe is (conformally) flat, this universe already contains infinite energy. From what I recall, the normal definitions of total energy of a spacetime are not possible to formulate for non-asymptotically flat spacetimes. So it is a bit nonsensical to talk about the total mass/energy.
The easiest skeptical take on multiverses is simply that there are no measurables defined by multiverse theories yet. I usually lump them in with anthropic theories, which a lot of GR theorists seem to love.
- evanpw 8y agoTalking about asymptotics already assumes that the universe is infinite. Any smooth, finite spacetime will have finite energy. The interesting thing about asymptotically flat spacetimes is that they can be infinite in volume but have finite energy.
- darkmighty 8y agoBut our universe is believed to be isotropic, and it has positive energy density everywhere, so it seems that should imply infinite total energy.
- wuliwong 8y agoWhy would this lead to infinite energy? Positive density summed over a finite volume does not equal infinity.
- ouid 8y agoThe "anthropic theories" aren't really something you can be skeptical about in the normal sense of skepticism, unless I'm misunderstanding your point.
- BlackFly 8y agoWell, indeed I disregard anthropic theories largely on the grounds of non-cognitivism, which I suppose is not an ordinary form of skepticism. I lump them both together in my own mind not because of how I rationalize ignoring them, but instead because I think the popularity of both of them is driven more out of spiritualism than science.