The fact that multiple realities might exist would have physicists losing their minds. I'd love to see that. I'd never been one for string theory, or that crack parallel universe nonsense, but it seems more possible than it did back home. I may look into it, though I'm not sure I really want to know what it's like being dead.
He pretty much is. I created him and he's -not to brag- the best AI on the planet.
I'm sure there's some frequency they can show up on, even if it's not the typical light or ultra-violet or red spectrums. JARVIS might be able to scan them all and see if it's even possible. If they exist and you can see them, there's got to be some way to make them visible to the rest of us.