You know how people say that if time travel were possible, we’d have been visited by time travelers by now (though some think that’s what UFOs are)?
Can I apply that same line of thought to the concept of alternate universes? If there’s an infinite number of alternate universes, shouldn’t there be one populated by cosmic horrors with the raw power to simultaneously conquer every single other alternate universe?
Now, I can already think of objections to this, such as the assumption that alternate universes could develop with such different physical laws (though again, infinite). Indeed, if we posit that alternate universes must be based in our own laws of physics as we know them, then of course not being visited by extradimensional travelers would make perfect sense (if nothing else, because the odds of “sliders” getting to ours in particular is, well, infinitesimally small). But do the current scientific theories do so?
It is not an issue of different physical laws in different parallel physical universes; it is a matter of whether it is a law of the multiverse that you can’t travel between parallel universes. I am not absolutely sure, but I think this is an axiom of the Everett “many worlds” quantum theory, which, so far as I know, is the only (quasi) serious scientific theory to posit multiple parallel universes. Actually, one should probably state it more strongly: the parallel universes cannot affect one another in any way at all.
I guess that your argument adds a bit of weight to the view that if there are parallel world, you can’t travel between them (or otherwise affect ones other than your own), but we should have expected that anyway. (Really, the time travel argument is the same: it just tells us what we should have known, on stronger grounds, already.)
Electromagnetism radiates in three dimensions.
Does Gravity “radiate” in four dimensions?
A big dollop of mass/energy “now” acting upon a proximate object later due to finite-speed c transversing distance.
Can events now “radiate” to the past?
Effect preceding Cause?
I thought that the reason why gravity appears to be so much weaker than any of the other forces is that it exerts itself across many more dimensions than the others.
What he said. There’s no particular reason to believe that “cosmic horrors with the raw power to simultaneously conquer every single other alternate universe” are possible, in which case they would keep on not being possible regardless of how many alternate universes there were. There could also be a finite number of alternate universes, in which case even things that were theoretically possible might not actually ever occur.
If you’re really talking about an infinite number of parallel universes, then yes, there are an infinite number with Cthulhoid horrors invading an infinite number of parallel universes. And, an infinite number where they’re not.
The problem with most parallel universe stories is that they treat it as if there AREN’T an infinite number, but instead, say, a couple hundred. At which point the “why not” question becomes kind of moot. It’s easier to tell a story, because it’s a more easily-grasped number of universes (think Heinlein’s Number of the Beast series–they had a gazillion universes to draw from, which is not infinite but very large, and still only really contacted a few dozen).