Time travel has long fascinated science fiction writers and the science community. ScienceAlert was interested in the physicist who thought he had discovered what made this phenomenon possible.
Our current understanding of time relies on Einstein’s theory of general relativity. This makes it possible to understand space and time as a single entity: the famous “space-time”. Physicists have verified Einstein’s theory with the greatest accuracy and are quite sure that it is the most successful description of the structure of the universe.
They also use it to try to find a way to time travel. Thus, we have found equations that are consistent with this theory, but cannot be applied in practice for two reasons.
The first is to build a time machine, you need something called exotic matter, which is negative energy matter. Thanks to quantum physics, we know that this type of matter can be created theoretically, but in too small and too unsustainable quantities. And we have no concrete evidence of this achievement at this time.
The second reason is even more significant: the time travel paradox defies logic. The most problematic of these is the coherence paradox. Here’s a simple example: imagine you’re building a time machine and come back five minutes. Then you destroy this machine. But since you destroyed it five minutes before you made it, how can you use it five minutes later? And most importantly, if you can’t use it five minutes later, then you can’t go back in time and destroy it…
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