>>11292092While it's true that our theories on the matter make all forms of time travel impractical and unlikely, it's ultimately also true than many of the technologies we now posses were once science fiction and your brand of dount creates nothing. A worldline is the path of an object in four dimensions. By treating the universe as one object it makes some sense.
>>11292202There's also the fact that black holes don't work as data compressors, and cell phones don't interface with your temporal lobe in such a convenient way but many things are built for plot convenience. Why the D-mails always arrive where they do is also hand waived. But I'll do my best to address your questions as I understand them
1/2. There are worldlines that are extremely similar to ones from which D-mails branched off. Okabe travels through these while trying to re-retrieve the IBN 5100, and in the alpha portion of 0, and he alternates between three of these worldline clusters in his story in linear bounded phenogram, but they have very slightly different divergence from the one's he's departed from. You have to understand that worldlines are just a particular configuration of the world as it is being experienced and recalled. Every small choice changes it a bit. If events play out which alter the past, the world is rewritten, but if events would alter the future (as experienced by the time traveler) without being one of the branching points between attractor fields, fate steps in and the event is determined.
3. I've always assumed time machines can return to the future they came from in an emergency, essentially hopping back onto a worldline where they didn't fuck up yet. Since time machines going to the future is unique to them compared to d-mails and time-leaps.
It makes enough sense if you think about the particular portion on a penrose diagram for a kerr black hole labeled "other universes" is practically a blank check for sci-fi. It's just an unknown.
