For decades there are discussions about the (im)possibility of time traveling. We all know that time traveling on the macroscopic scale is by modern science considered to be impossible. The reason is, that by influencing even a single tiny particle in the past would alter the time line and change history. This would result in paradoxes like “how could I exist in my present time if I travel to the past and kill my mother before I am born”. I think, this particular paradox has a logical and valid solution (using many-worlds ideas or accepting self-correcting approach), but there are other, more complicated, where it is not so obvious if they are resolvable, too. They probably don't.

Still, there are at least two possibilities how to accept time traveling in general with no temporal paradoxes at all. And both are very simple to understand. It is possible I am not the first one who invented it, but at least I neither read nor hear these ideas before.

Solution 1: inflated universe and light cones

It is commonly known, that there is no information in our universe spread faster than with the speed of light. And speed of light is finite number, so it takes time for any thing or signal to anywhere. It has a nice consequence – we see not the current universe. All what we see has happened in the past, the more distant event the more in the past. As time progresses we see more and more distant (means also more past) events. This can be graphically demonstrated as so called light cone – we see what is inside the cone only, but the cone moves in time and so we can later see events which we are not able observe now.

In addition to this, we believe that our universe is inflated. It means there was a time period long time ago, in which universe expanded much faster than with the speed of light. It seems to be possible because only the space-time metrics inflated and matter and radiation were created independently from vacuum energy in the whole universe, not distributed from a single point. But if we accept the inflation phase of universe evolution, it also means there are regions which simply do not communicate with each other because the are apart – so far from each other that even 14 billions years of the existence of our universe was not sufficient for light to travel the distance. If the universe is big enough and expanding with increasing velocity or with a if the universe will not last forever, there is a big chance that there are regions which will never be able to communicate with each other.

We don't know it these regions share exactly the same laws of physics, but suppose they are. In that case, it is principally possible to travel to these regions even in different time, because if we change anything there, there is no way how to influence our past here.

But still, how to travel between parts of universe which are so far that even light hasn't been fast enough for it ? I hope there is possibility to influence the topology of space-time and we will be able to find a shortcut one day.

Solution 2: events sequence logic

This is probably the simplest way to travel through time, although it gives us much less freedom in choosing when and where we will travel, at least in comparison to the previously explained solution.

Every event in our universe triggers another events. This way we can see the universe as for billions of years expanding network of partially interconnected events. It propagates through space and evolves in time. We are familiar with thinking of time in a linear way – simple straightforward direction of time arrow for all the ages. But, as well as we (thanks to Einstein) accepted, that time does not evolve with constant rate in particular regions, what prevents us to believe it can also be non-linear in particular events ? The idea is simple: imagine that the universe has time traveling included in its evolution time line. For example, there can be need for jump back in the time in some particular event to create another event in past to enable some future event. The question is: can our universe be consistent in a special case, where no time travel ever occurred ? I tend to believe there is nothing special on our existence so there is no reason for such a special circumstances as time to be strictly linear.

If this is true, time travel occurs, but we can't neither induce nor hinder it in other places and times than is already projected by the universe itself. It would have vast consequences for our faith in free will.