Have you ever made a blunder you wish you could take back? One of the reasons we find the notion of time travel so intriguing is because it allows us to correct previous mistakes. Nothing is permanent with a time machine, as depicted in science fiction, since you can always go back and alter it. But, in our reality, is time travel truly conceivable, or is it simply science fiction? General relativity is responsible for our present understanding of time and causation. Albert Einstein’s theory merges space and time into a single entity — “spacetime” — and gives a breathtakingly complex description of how they both function on a level that no other known theory can match.
This theory has been around for almost a century and has been empirically tested to a great degree of precision, so physicists are certain that it accurately describes the causal structure of our world. Physicists have been attempting to utilize general relativity to determine if time travel is conceivable for decades. It turns out that time travel may be described using equations that are entirely compatible and consistent with relativity. However, physics is not mathematics, and equations that do not relate to anything in reality are worthless.
OBJECTIVES TO TIME TRAVEL, There are two major concerns that lead us to believe that these equations are impractical. The first problem is a practical one: it appears that manufacturing a time machine necessitates unusual stuff, or matter with negative energy. Positive energy pervades all we encounter in our everyday lives; negative energy isn’t something you’ll find sitting about. We know from quantum physics that such stuff may theoretically be generated, but only in very small amounts and for very brief periods of time. However, there is no evidence that producing unusual matter in significant numbers is difficult. Other equations that allow time travel without the need of exotic stuff may also be discovered.
As a result, this problem might simply be a result of our existing technology or knowledge of quantum physics. The other major difficulty is the discovery that time travel appears to violate logic in the form of time travel paradoxes, which is less practical but more crucial. There are various sorts of such paradoxes, but consistency paradoxes are the most troublesome. Consistency paradoxes are a common cliché in science fiction where a given occurrence causes the past to change, yet the change precludes the event from occurring in the first place.
Consider the following scenario: I enter my time machine, use it to travel back in time five minutes, and then destroy it as soon as I reach the past. It would be impossible for me to utilize the time machine five minutes later now that I had destroyed it. But if I can’t use the time machine, I won’t be able to destroy it in the future. As a result, it has not been destroyed, allowing me to travel back in time and destroy it. To put it another way, the time machine is only destroyed if it is not destroyed. This situation is illogical and paradoxical since it cannot be both destroyed and not destroyed at the same time.
GETTING RID OF THE PARADOXES, in science fiction, there’s a prevalent notion that paradoxes may be “made.” For this reason, time travelers are frequently advised not to make large alterations to the past and to avoid encountering their previous selves. Many time travel movies, such as the Back to the Future trilogy, have examples of this. In physics, however, a paradox is a purely theoretical term that refers to a contradiction in the theory itself, rather than an actual event. In other words, consistency paradoxes don’t only suggest that time travel is perilous; they also imply that it is impossible.
One of the reasons for theoretical physicist Stephen Hawking’s chronology protection conjecture, which claims that time travel should be impossible, was because of this. However, this theory has yet to be verified. Furthermore, instead of abolishing time travel due to paradoxes, we could just erase the paradoxes themselves, making the cosmos a far more intriguing place. The self-consistency hypothesis of theoretical physicist Igor Dmitriyevich Novikov, which effectively asserts that you may go to the past but not alter it, is one effort at resolving time travel paradoxes. According to Novikov, I would be unable to destroy my time machine if I attempted to do it five minutes in the past. The principles of physics would collaborate in some way to maintain consistency.