
trying to pass psuedo-science as fact much?
No, I'm discussing
actual quantum physics. What gets presented in science fiction is generally a loose or inaccurate extrapolation from ideas that originated in real science. Multiverse theory -- the concept of alternate observed histories for the universe -- is an outgrowth of the mathematics of quantum theory. It's what you get when you take the fact that a quantum particle can exist in a superposition of multiple different states at the same time and apply it to all the particles of an observed system at once. All the science fiction about alternate realities and histories is based on this real-physics idea, though often quite fanciful in its interpretation of it. So grounding the discussion in real science is a way of getting across how it
should work, so we can better evaluate fictional presentations of the idea.
Besides, it's just common sense. Like I said, you wouldn't expect an unrelated universe to have an Earth and a humanity any more than you'd expect another planet to have Earth's geography. The existence of humanity is not some cosmic destiny, it's the accidental result of a bunch of different events that happened in the universe's past. So an alternate reality that has Earth and humans and so forth in it must have branched off from that same history. It
was the same timeline until something in it happened differently and it diverged, just as you said above.
There's different definitions of universe. The definition of universe as its used in TNG episode "Parallels" is the one I'm using.
The point is, that's a vernacular usage that's misleading if you actually want to understand what's being talked about. Sci-fi tends to use terms like "universe" and "timeline" interchangeably, but that's a sloppy practice that confuses the issue.
Having multiple choices at any given moment and representing the result of each of those choices as a quantum universe is one thing. But time travel is something else.
No, it really isn't. As far as actual theoretical physics is concerned, time travel is subject to the same quantum laws as any other phenomenon in the universe. Quantum physics has been applied to the theoretical question of time travel, and what it suggests is that, normally, a time traveler would be unable to create any future other than their own, because their travel into the past would correlate it with the future they came from and, from their perspective, guarantee that that future happened. So that would produce a fixed-timeline model like the movie version of
12 Monkeys or the animated series
Gargoyles, where nothing you do can alter destiny. However, if multiverse theory is true, if alternate timelines can exist, then a time traveler would follow all possible paths at once. There would be one timeline in which the time traveler failed to change history and one in which they succeeded in changing it -- or multiple ones in which it was changed in different ways.
So in real-science terms, the physics that allow for the possibility of time travel altering the timeline are the exact same physics that allow spontaneous parallel timelines to exist in the first place. It may seem to a human being that there's a difference between something that "just happens" and something that a person's actions and choices cause to happen, but the laws of physics don't care about personal will and choice. As far as the universe is concerned, a person is just a bunch of interacting particles and forces. So there is no
physical difference between a naturally occurring alternate history and one created by time travel.