The multi universe theory is not so popular nowadays, in the scientific comunity even though it is still supported by great scientists

Obviously it has nothing to do with the example provided in this thread

Although it seems a crazy theory, the alternative and widly accepted theories are even worse.
Briefly, the supporters of the multi universe theory simply beleive that :

a) two entities can interact just in case they are in direct contac or if they can exchange messages

b)
an atom is just a particle
It can not be both a wave and a particle at the same time

Probably you ( and me ) have no problem to agree with above claims
Unfortunatly the lab evidence are against a) and b)

The multi universe theory claims that a) and b) are still true but we have a limited knowledge of our universe

Although the theory of multi universe has been almost abandoned the most popular theory nowadays ,the theory of string has actually strong similaritis with the theory of the multi universe