The notion that other universes may be somehow 'out there' (in here?), and 'sort of' interacting with ours is really difficult to wrap one's head around. If another universe is capable of interacting, it seems like it would be, by definition, part of THIS universe....and if it is, by definition, defined by different spatio-temporal parameters, it seems as if we could not 'know' anything about it or interact with it.

I suppose I am not familiar enough with the math and hypotheses well enough to see why they are taking this seriously, but it seems as if this might be just another attempt to resolve problems like 'missing matter' from the Big Bang.

The alien conundrum (if I understand what you refer to) doesn't bother me at all. If aliens exist and we 'can' communicate with them, we are rather in the position of someone like Vikings...or better, Chinese, in 1000 AD, wondering if there were 'others' out across the oceans.....we simply haven't the technology to go look, or we haven't looked in the right places with the right tools yet. It is pretty smug to imagine that OUR magnificent achievements are sufficient to see/hear 'em if they're there.