Is there a Multiverse?

 To believe is to challenge reality.

On Netflix at the moment I am watching an engrossing science fiction series. The question is the multiverse theory expounded by some scientists and philosophers science or science fiction?

In short, the theory is that for every action we take, or don't take a universe is created for that action, this would lead to endless universes of mainly dead ends. On the other side of the coin, some people say that for each action we do NOT take any universe that would have been created for that action doe snot exist.

I have no views either way as I am not educated highly enough to argue for or against a side. Some philosophers say that when we get the feeling that somebody has walked over our grave that is a crossing of time lines.

If you have read my posts, you will know I believe  in what is loosely called "Fringe Science," that is science the world won't accept or believe in now. 

Doppelgangers are totally different thing; I do believe we have doubles as when I had a pen-friend when I was in Scotland, she told me I had a double in New Zealand.