Far out cosmology: energy in this universe (Introduction)

by David Turell , Monday, July 05, 2021, 21:01 (1235 days ago) @ David Turell

There has to be some in the vacuum:

http://backreaction.blogspot.com/2021/07/can-we-make-new-universe.html

"Einstein also taught us that space is dynamic. It can bend and curve, and it can expand. It changes with time. And if space changes with time, then energy is not conserved. I explained this in more detail an earlier video, but here’s a brief summary.

"The simplest example of energy non-conservation is the cosmological constant. The cosmological constant is the reason that the expansion of our universe gets faster. It has units of an energy-density – so that’s energy per volume – and as the name says, it’s constant. But if the energy per volume is constant, and the volume increases, then the total energy increases with the volume. This means in an expanding universe, you can get a lot of energy from nothing – if you just manage to expand space rapidly enough. I know that this sounds completely crazy, but this is really how it works in Einstein’s theory of General Relativity. Energy is just not conserved.

***

"...no one really knows how our universe was created in the first place. There are many different theories for it, but none of them has observational support. However, one of those theories has become very popular among astrophysicists, it’s called “eternal inflation” – and while we don’t know it’s right, it could be right.

"In eternal inflation, our universe is created from the decay of a false vacuum. To understand what a false vacuum is, let’s first talk about what a true vacuum is. A true vacuum is in a state of minimal energy. You can’t get energy out of it, it’s stable. It just sits there. Because it already has minimal energy, it can’t do anything and you can’t do anything with it.

"A false vacuum is one that looks like a true vacuum temporarily, but eventually it decays into a true vacuum because it has energy left to spare, and that extra energy goes into something else. For example, if you throw jelly at a wall, it’ll stick there for a moment, but then fall down. That moment when it sticks to the wall is kind of like a false vacuum state. It’s unstable and it will eventually decay into the true vacuum, which is when the jelly drops to the ground and the extra energy splatters it all over the place.

***

"What does this have to do with the creation of our universe? Well, consider you have a lot of false vacuum. In that false vacuum, there’s a patch that decays into a true vacuum. The true vacuum has a lower energy, but it can have higher pressure. If it has higher pressure, it’ll expand. That’s is how our universe could have started. And in principle you can recreate this situation in the laboratory. You “just” have to create this false vacuum state. Then part of it will decay into a true vacuum. And if the conditions are right, that true vacuum will expand rapidly. While it expands it creates its own space. It does not grow into our universe, it makes a bubble."

Comment: This explains how our universe has 'dark energy' producing the expansion. All theory, as no one has found that energy for real