There are apparently two theoretical counterparts in our real world, or in our physics. Firstly, there’s the idea that from the beginning, there’s an infinite number of parallel universes where all things that can happen, do happen. Our Universe is just one of that infinite set. In five of those universes, you 1) flip a coin – in one, it’s a heads you flip; in another, tails; in the third, the coin stands on edge! Or, in a fourth universe you decide not to flip a coin at all, or in universe #5 you decide to flip something else instead.
The other theoretical set of parallel universes is a set that ever increases, staring with just one. Universes split whenever an either/or choice is forced upon it, such that all results that can happen, happen. In this (our) Universe you decide not to flip a coin – but that decision results in a division, the universe splits and in that split, in the new universe, you do flip a coin. In that universe it comes up heads. But, that universe then splits into two and yet another universe where your flip has tails comes up. There’s also another universe where the coin lands on edge! There’s also a universe that originally splits off where you decide to flip something other than a coin. This is known as the ‘Many Worlds Interpretation’ theory, (which resulted out of a need to explain certain quantum phenomena). With every passing second, more and more universes branch off (actually trillions per second).
I’ve never been a fan of the Many Worlds Interpretation of all things quantum. That is, the universe keeps splitting each time it comes to a fork in the road. The question of where all the matter/energy comes from – created out of nothing apparently – I’ve yet to see addressed in the texts. But, many top notch 紐西蘭升學
scientists adopt it – perhaps as the least of all the evils certain quantum phenomena dish up. As to where they fit, all those extra universes, that’s not as much of a problem. A motel with an infinite number of rooms never has to put out a ‘no vacancy’ sign – if you get the analogy. Oh, the Many Worlds Interpretation also means that there’s no such thing as free will. You may think you have free will in deciding to wear your red dress instead of your green dress, but in the Many Worlds Interpretation, you do both – so no free will.
However, I myself go for the Copenhagen Interpretation* – when you come to a fork in the road, one and only one choice is made – the other possible choice(s) are never realized and ultimately never have any reality. But, if you start out from scratch with an infinite number of universes, or at least a vast number, then the issue of ‘where’ all the universes are is irrelevant, and the creation of all the stuff that makes them up is equally irrelevant. In the beginning, it was so!
You can have an infinite number of universes in an infinite amount of space. An analogy – there are an infinite number of whole numbers like 1, 2, 3, 4, 5, 6, etc. There’s also an infinite number of even numbers such as 2, 4, 6, 8, 10, 12, etc. Ditto an infinite number of odd numbers. Yet the infinite set of even numbers, plus the infinite number of odd numbers, equals the infinite set of whole numbers. Infinity + infinity = infinity! Or, if you like, think of your house (volume) with just one molecule (universe) in it. You’d agree there’s room for one hell of a lot more molecules (universes). If your house had infinite volume, then…
I had always assumed, and followed the assumptions of others infinitely more brilliant than I, that such theoretical constructions, such parallel / alternative / mirror universes, was forever beyond our actual reach – works of fiction aside of course. We could construct them as an intellectual exercise, but could never verify and understand the actual existence of these mental or thought experiments. That’s because these universes, if they exist, would not be part of our space-time continuum and thusly we could never interact with them.
But what if that assumption is wrong? What if parallel / alternative / mirror universes not only exist, but can and do interact with ours, and thereby give some additional credence to the adventures of our “Alice in Wonderland” and “Star Trek” characters, not to mention the reputations of those physicists who propose infinite universes or Many Worlds Interpretation theories.