Are time travel possible?

To write this post I was pushed by the topic Physics of the impossible - or rather, the passage about the relativity of the impossible.

Are time travel possible?

Not. At least in our reality. If it were possible, then we would already know about it - reality would change and we would be aware of the precedents for travelers from our future in our past. However, the story does not report anything like that.

There is, however, one “but”: my statement is true under the condition of linearity of time, i.e. if it is an infinite continuous line.

It is possible that time is able to branch: this means that, having returned to the past, the time traveler at the point of his appearance creates a branch that goes according to the new scenario, taking into account its presence. But this automatically means two things: first, the possibility of the existence of an unlimited set of parallel universes, and secondly, that you can’t fix anything by returning to the past, because the reality from which the traveler went to his past will remain unchanged is all that he can do , is to create another reality, where things will go differently. And that is not the fact that it is more successful.

And the most interesting thing in assuming the possibility of “multiplication” of universes is whether they can converge back together.

In this I see a parallel with the discussion of the motion of the Universe after the Big Bang: some scientists say that it will expand indefinitely, until it spreads infinitely far; others - that sooner or later the Universe, having reached a certain limit, will begin to shrink until it collapses completely and causes a new explosion, restarting the cycle. Personally, this option seems to me more likely and natural, chtoli.

But is it possible in this case that parallel universes generated by time travel will, like rays emitted from one point, forever run endlessly from each other? I think no. If we accept the version of a shrinking Universe, then its various alternative options should also be subject to this “pulsation” - which means that they will inevitably come to an end sooner or later - that is, they will collapse. In other words, the diverging branches of time will meet again at one point - at the point of the Big Bang.

In addition, the possibility of the branching of time presupposes the presence of one “correct” universe, which is unambiguously identified as such - and this is our universe, and many “wrong” ones. Identifying them is very simple - if suddenly in the Stone Age an army appears on tanks and aircraft carriers - it means that you are in parallel reality.

But I was distracted, of course. The genesis of parallel universes is a very interesting topic - assuming their existence.

I will return to the question posed in the subject and answer a little more broadly: if time travels are possible, then only as travel in time and reality. Because the fact of moving in time (if it is possible) opens up a new reality.

It's just that time travel - within the framework of one reality - is an unattainable dream.

So if you dream of creating a time machine to fix something, for example, in your past, think about it - your past will not change from this anyway.

UPD user dimonline pointedto a very important thing that I missed at first: people cannot travel consistently to the same past, because each appearance of them there will create a separate branch of time.

And this means that on such alternative branches there could be a group of people, one person or even an inanimate object from the future - even a molecule accidentally moved to the past is enough to launch an alternative branch.

People of this kind of presence in this alternative reality might not have noticed or not recognized.

And this means that my statement above that we live in the only right universe is wrong. We can very well live in this kind of branch. As for me, this is very sad :(