In this excerpt from Mostly Harmless ©1992, Douglas Adams explains the concept of Parallel Universes:
The first thing to realize about parallel universes… is that they are not parallel.
It is also important to realize that they are not, strictly speaking, universes either, but it is easiest if you don’t try to realize that until a little later, after you’ve realized that everything you’ve realized up to that moment is not true.
The reason they are not universes is that any given universe is not actually a thing as such, but is just a way of looking at what is technically known as the WSOGMM, or Whole Sort of General Mish Mash. The Whole Sort of General Mish Mash doesn’t actually exist either, but is just the sum total of all the different ways there would be of looking at it if it did.
The reason they are not parallel is the same reason that the sea is not parallel. It doesn’t mean anything. You can slice the Whle Sort of General Mish Mash any way you like and you will generally come up with something that someone will call home.
There’s something about this that does ring true.