Okay, it's coupled to the idea of 'dark energy'.

"I think dark matter is more relevant to the next age of particle physics experiments — hopefully supersymmetry and perhaps other interesting things that we may discover. On the other hand, there’s at least a good chance that dark energy is energy of the vacuum, so it seems to be telling us something about the fundamental structure of physical law, which is a big surprise. The vacuum energy has been a haunting question for particle theorists since the advent of quantum field theory in the 1930’s. As soon as we had quantum field theory we knew that the vacuum was not a simple state: It was a very complicated state with all kinds of quantum fluctuations going on. And there was no reason at all why the energy of the vacuum should turn out to be zero or small.

In fact, nobody knows how to calculate the energy of the vacuum, but if particle physicists were to try to estimate it, the natural answer would be something like 120 orders of magnitude larger than the experimental bound. So it was always a big mystery, but until the advent of dark energy, the belief was that the real number was zero, because of some kind of symmetry that we didn’t understand yet — an exact cancellation between the positive and negative contributions. If dark energy is the energy of the vacuum, now you need that symmetry to make it almost zero, and then some small breaking of that symmetry to make it a small number that’s not zero. And it all gets very complicated and baroque. Nobody has the faintest idea of how it might actually work. There is also the possibility that the vacuum energy is not determined at all by the fundamental laws of physics, but instead it’s determined anthropically, using the idea of a multiverse.

It’s quite possible in the context of string theory that there are many vacuum-like states, and all of them are stable enough that they could provide the underpinnings of a universe. And the one that we happen to find ourselves in is determined by random choice. One would imagine that the universe would inflate eternally through all the different possible vacua of string theory, with infinite amounts of space of every type of vacuum produced — eventually... If this is right, it would mean that in most regions of space the cosmological constant is enormous, and there are some rare regions of space where the cosmological constant happens to be very small. But life can only form if the cosmological constant is very small. So it’s not a surprise that we find ourselves living in one of those regions. An idea like this five years ago would have been completely anathema to particle physicists. It is still anathema to many, but people pay much more attention to this kind of idea now."

Does this connect to the idea of eternal inflation, with different universes bubbling off?

AG: Yes, there are two ideas coming together here. One is the idea from string theory, that there’s a huge number of possible vacuum states. And the other is the idea of eternal inflation, that once inflation starts, it never ends, and it explores all possible vacua." From

Here.. I don't know there myself

Maybe, this is speculation based on theory. String theory to be precise, and in string theory everything becomes possible. There we all are branes, strings or loops, vibrating and 'dimensions' becomes something you can handpick to fit your definitions. It might be so, but there are other variants of string theory too. And in the end we still need to find evidence for string theory actually existing as a 'fact'. It's pure mathematical theory, just as the proof of all parallel lines converging into a point. Mathematically impeccable as I understands it, but nowhere to be seen in our universe, yet. Made sometime in eighteen-hundred if I remember right(?) By a (French) mathematician.

And 'energy' is a conceptual property, defined through interactions. That we found a logic telling us how those 'interactions' will deliver this amount of 'energy' doesn't mean that 'energy' as such exist. We use the concept and I do too, but you could as easily define it as outcomes from a game with rules, no energy at all. You roll the dice and get a six, move three steps to the left. Most of the definition of 'reality' we have is constructed around the Newtonian concepts, which are the ones most suitable, until now, for describing our kind of reality. We now find more and more 'breaks' in that reality and so adapt it. But doing so we still assume that this reality is what counts. Which in a way is perfectly understandable. Then we have others that decides that this reality does not count, and so look at anything that can let us build a 'universe' where one of the outcomes become 'SpaceTime'.

Myself I don't know

Wish I did though.

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I can say this though, I think the problem isn't with us needing a more complicated reality. The real problem lies in our definitions of what 'reality' should be. That's what blinds us to the reality we exist in, and that one we inherit, each one of us, when growing up. The way you relate to the world you live in will color your perception, and there no 'mind' however sharp, can escape. Einstein is a rare exception there.