Although quantum physics is often hard to wrap one’s mind around, most non-scientists are still familiar with the idea of the multiverse, thanks to its many depictions in science fiction. In layman’s terms, every time you make a choice, a universe splits off from another and a new universe is born. In a world full of choice, new universes are always being born, creating an infinite number of parallel universes.
The ongoing theory about the multiverse is that because universes are consistently splitting off into other bubble universes, the multiverse itself is endless (although some of the bubble universes do eventually die). The idea is that particles are always fluctuating, and in fact, some of this fluctuation affected the rapid expansion of the early Universe, rapidly creating new bubble Universes shortly after the Big Bang.
However, this theory has some inherent problems. If there is even a slight chance of everything happening at some point, if you wait long enough, eventually all this collection of matter in these bubble universes makes self-aware disembodied brains.
At this point, obviously, the theory starts bordering on the ridiculous, at least according to Sean Carroll at the California Institute of Technology. So Carroll proposed a new theory that doesn’t include this weird disembodied consciousness. Carroll surmised that bubble universes did not occur during the inflation of the Universe, as the particles present had nothing else to interact with, meaning no quantum fluctuations occurred. He believes that only after inflation, when these particles became normal particles, were the fluctuations present.
However, there’s still room for the multiverse in Carroll’s theory. He looked at the “observer” concept, which basically means that universes only branch off when we measure a quantum state, which creates quantum fluctuations; each potential outcome ends up with its own universe. This means that the multiverse is not just a bunch of separate bubble parallel universes, but more like universes that overlap each other, having started from the same beginnings. Of course, this then means that the multiverse isn’t endless and that it can die, because at some point, there will be no observers to create the quantum fluctuations needed to create more universes.
It’s a simple theory, at least for quantum physicists, and there isn’t really a right or wrong answer here. But challenging current theories gives us a better understanding of our Universe and its workings.
Via New Scientist