"One encouraging thing the Guide does have to say on the subject of parallel universes is that you don't stand the remotest chance of understanding it. You can therefore say "What?" and "EH?" and even go cross-eyed and start to blither if you like without any fear of making a fool of yourself. The first thing to realize about parallel universes, the Guide says, is that they are not parallel. It is also important to realize that they are not, strictly speaking, universes either, but is as 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 a 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 Whole Sort of General Mish Mash any way you like and you will generally come up with something that someone will call home. Please feel free to blither now." Douglas Adams, Mostly Harmless, the fifth in the increasingly inaccurately named Hitchhiker's Trilogy