If you have a time machine that lets you solve a problem in your timeline by going back in time to solve it, then you also eliminate the reason causing you to go back in time to solve it, which means that you aren’t going to go back in time…
That’s one possible option. The other is that going back in time and changing anything creates a new reality without destroying the one you come from. But since we can’t go back in time we don’t know if it’s the multiverse or the only-one-timeline.
If you have a time machine that lets you solve a problem in your timeline by going back in time to solve it, then you also eliminate the reason causing you to go back in time to solve it, which means that you aren’t going to go back in time…
Great Scott!
That’s one possible option. The other is that going back in time and changing anything creates a new reality without destroying the one you come from. But since we can’t go back in time we don’t know if it’s the multiverse or the only-one-timeline.