Is there any scientific way to backup the existence of other realms

Anything Einstein might have said about this... Or is it completely improbable.

You should read Brian Greene's "The Hidden Reality." It discusses the current state of pretty much all the theories that would allow for multiple universes. Very interesting book, in my opinion. One chapter addresses exactly the question you asked, but the short answer is "It depends." Some of the theories postulate universes that could be be detectable via certain sensitive scientific experiments that examine the behavior of subatomic particles, while others propose universes that could never be detectable via any conceivable scientific test performed in this one.

http://www.amazon.com/s?url=search-alias…

I'm not sure what you mean by 'other realms'. 'Realm' is not a scientific term. Do you mean other universes? They might exist, but as of right now, we have no way of seeing them - we can't see outside our universe. We might be able to build telescopes (like LISA) that could see outside our universe in the future.

Only that since the universe is so vast, there might a nearlly infinite amount of sceneraious or tyhings out there. The universe is aparently expanding faster than the speed of light.

It's highly implausible.