Far out cosmology: enough energy for multiverses (Introduction)

by David Turell , Sunday, December 13, 2020, 23:58 (1439 days ago) @ David Turell

More weird thinking:

https://www.forbes.com/sites/startswithabang/2020/12/11/ask-ethan-how-do-we-get-enough-...

"...where does all the mass/energy for a multiverse come from? That’s what Professor Laura Templeman wants to know, asking:

“'I don’t know how to explain the multiverse’s mass. If it constantly is splitting into new multiverses where is the conservation of energy? Is it bc gravity is negative energy? Is it because expansion creates more? I am sure I’m missing something elementary but... how we can have enough mass for so many multiverses?”

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"...no matter how big our Universe actually is, that doesn’t mean it’s the only one. Even if the Universe is infinite, there can be others; remember that some infinities are bigger than others.

"The key to thinking about this is to understand where the (physically motivated) idea of the multiverse actually comes from. It arises if you take seriously the idea of cosmic inflation, which is the best theory and mechanism we have for what came before, set up, and gave rise to the Big Bang itself.

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"When we look out at the Universe and extrapolate what it must have been like at the start of the hot Big Bang, we find a few puzzling phenomena. We see that it’s the same temperature and density everywhere and in all directions, even though the distant regions to your left and right haven’t had time to exchange information or communicate over the known history of the Universe. We see that the total energy density and the initial expansion rate must have been equal, at the start of the hot Big Bang, to approximately 25 significant digits, something that the Big Bang doesn’t explain. And we see that there are no leftover high-energy signatures from the early Universe, something that would be expected if the Universe rose to infinitely high temperatures and densities early on.

"How is this possible? That’s where the idea of cosmic inflation comes in: perhaps the Universe had a phase preceding the hot Big Bang. In this phase, rather than being filled with particles, antiparticles, radiation, and other quantized forms of energy, the Universe is filled with a form of energy much like dark energy: energy inherent to the fabric of space itself. While it’s in this state, the Universe expands at a relentless, exponential rate. Only when inflation comes to an end does this energy get transferred into particles, antiparticles, and radiation, creating a hot Big Bang.

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"There’s a lot we don’t know, even in theory, about these multiple Universes, but if inflation is correct and the laws of physics that we know are still valid during it, their existence is all but inevitable. This is where the idea of the multiverse, from a pure physics perspective (with no appeals to philosophy, interpretations of quantum mechanics, or assumptions about the pre-inflationary Universe), arises from.

"That’s where the idea of a Universe from nothing comes from. If “nothing” is the nothingness of empty space, but empty space started off in an inflationary state, not only will it give rise to a Universe like ours, but an extraordinarily large (and possibly infinite) number of independent Universes will arise as well. Each one will be filled with its own particles, antiparticles, radiation, and whatever forms of energy are allowed.

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"As the Universe expands, the number of particles stays the same, the volume increases, but the total energy remains the same.

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"Dark energy is also different. It’s an energy inherent to the fabric of space itself: a form of energy that has a small value today, but had a very large value during inflation. As space expands, the energy density remains constant, but the volume increases. The total energy of the Universe goes up over time, since energy equals density multiplied by volume.

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"The fact is that energy conservation only works at a particular location, not for the expanding Universe. You might have heard the expression that “there’s no such thing as a free lunch.” While that might be true here on Earth, that reasoning doesn’t apply to the expanding Universe. In fact, if ideas like inflation and the multiverse are correct, perhaps the real truth is that the Universe is the ultimate free lunch. In these trying times, this is one thing we can all be thankful for."

Comment: It all depends on which squirrel cage you live in. When Guth developed inflation, in his book he stated the universe had zero energy because gravity is a negative value and everything added up to zero. Siegel says different. When inventing possibilities anything seems to go.