Ah, Many Worlds
I keep getting whiffs of baby vomit. Or "spit-up," or "precious white barfikins" or whatever euphemism is making the rounds. No babies currently inhabit my space! How can it be that I smell baby puke when there is no baby present? I suspect that my dimension has cozied up to a parallel dimension in which a feckless baby (probably named Travis) puked on my couch cushion. I can't see the puke, and I certainly can't see the baby, but enough smellton particles have pierced my babyless dimension to make me aware of baby puke and there you have it. Science.