First, the concept of time travel is one of those fun parts of physics. Whether true or not, it is entertaining to play the ‘what if’ game. If nothing else, the concept makes or forces one to think about the nature of reality.
Secondly, Einstein and others have postulated that time travel is a theoretical reality and I’m not in their sort of league that I can dispute the theories. I’ll leave that to others who know the field inside and out.
Is time travel possible?
The answer is both yes and no. Yes, we can travel into the future at one second per second, we do that anyway whether we like it or not. Yes we can travel into the future at a slightly quicker rate by going to sleep or otherwise having our sense of consciousness, our awareness of rate of change (which is what time really is or measures) incapacitated. You get drunk and pass out and the next thing you know you are 12 hours into the future. Yes we can travel into the future as outlined by Einstein’s twin ‘paradox’ where one twin travels at a very high rate of speed outward bound, stops and returns to home base, while the stay at home twin, well, stays home. Upon their reunion the travelling twin finds their stay at home twin to be far older, so the travelling twin has travelled into the future more rapidly than would otherwise have been the case. Yes, you can travel back in time, in theory, according to the apparent theoretical properties that wormholes or black holes can have. No, you can’t travel to the past because of all of those nasty paradoxes. I like the variation on the grandfather paradox whereby you travel back just one hour into the past and shoot yourself dead. That’s a novel way of committing suicide! The other paradox I like is when you go back in time to have Shakespeare autograph your copy of “Hamlet”.
In the normal double slit experiment
You have an electron gun that fires one electron particle at a time, such that one electron completes its journey before the next one is fired, at two side-by-side slits. If one or the other slit is open, the one-at-a-time electrons pass through the open slit to a detector screen behind the slits. The detector screen gets hit in nearly the same spot every time after each and every electron particle passes through the single open slit. That is straight forward. If both slits are open, the electron shape-shifts into a wave (how I don’t know), passes through both slits (as only a wave can), morphs back into a particle and hits the detector screen. The difference is that after enough electrons have been fired, and have passed or waved through the double slits, the hits on the detector screen are not in just one or two spots but all-over-the-map, albeit all-over-the-map in a classic wave interference pattern. Okay, that’s the classic experiment.