Time Travel, Science or Science Fiction

Time travel, a beautiful phenomenon considered to be a science fiction event by a vast majority of people. One of the main reasons that this event is considered borderline science fiction is that most people cannot wrap their heads around such a complex phenomenon. In this article, we will discuss the possibility of time travel being actually existing, its scientific basis, and some of the paradoxes that come along with the package.

The Science

The first thing we have to understand before time is not an independent entity for 3-dimensional beings like us, but is intertwined with space as we perceive it. In physics, spacetime is any mathematical model which fuses the three dimensions of space and the one dimension of time into a single four-dimensional manifold. The fabric of space-time is a conceptual model combining the three dimensions of space with the fourth dimension of time. Time can also be represented as a physical dimension but this can be only possible for beings that exist on realities higher than the 3 dimensions we human beings can perceive (yes interstellar did their research). So since spacetime is a single entity any change in the fabric of space results in a change in the fabric of time. Here things get a little bit complicated as we can easily move in any direction of space but as of now it’s only seemingly possible to travel in one direction through time and that’s forward.

Some of you may find it impossible to believe but current-day technology allows us to time travel into the future but not by a large margin and the time difference is mostly accounts for nanoseconds. Still, time travel is time travel even if it’s by a nanosecond or by a year. As of how this is possible you may require a short understanding of Einstein’s Theory of Special Relativity. The faster you move through space the slower you move through time, this has been verified by using synchronized atomic clocks on jet planes that can go up to supersonic speeds. This can also be seen in astronauts as they age a bit slower relative to us, this has been verified through the Scott Kelly effect. Time would completely stop if we had the means to travel at the speed of light, but this currently impossible as an object would gain infinite mass as it closes in on the speed of light.

Another way to slow down or even stop time is with the use of a celestial body known as a black hole. A black hole is a celestial body that is formed when a supermassive star collapses on itself due to its own gravity. The resulting cosmic body produces a singularity that exerts a gravitational force so great that it can bend the fabric of spacetime and not even light can escape its pull after a certain point called the event horizon. If you somehow manage to survive the Spaghettification process then your time will completely stop after you cross the event horizon, but for a third person watching you entering the event horizon, he/she will observe you falling into the black hole for an infinite amount of time. This happens because for the third person observer time is still running but for you who have already entered the event, horizon time has stopped. This effect has been discussed in Einstein’s theory of relativity.

Now that we have discussed two of the common ways to time travel using the current understanding of science, let’s enter the realms of science fiction and see some of the paradoxes that comes if we ever manage to move back in time.

The Grandfather Paradox

This may be the most commonly known paradox as it has appeared in many movies and comics and stories. The simple explanation is when a person time travels to the past and kills his own grandfather before the person’s father/mother is born. This act ensures that the person’s father/mother is never born so the person will not exist, but if the person does not exist in the timeline then the grandfather isn’t killed and the person’s father/mother is born thus the person is also born. This event continues in a loop and there is no clear or oneway solution to this problem.

There are workarounds for this paradox. One such explanation is that nature would simply not allow such an inconsistency. It means that whatever you do in the past the timeline self corrects itself to avoid such inconsistency. This workaround is used in the movie “ Time machine”. These are just theories and the experimental proofs are still lacking but since time travel to the past itself is currently considered science fiction these theories and hypotheses come across as passable.

The Bootstrap Paradox

This paradox comes into play when the real origin of an object or idea is lost inside a time loop. For example, if a time traveler travels back in time and teaches Einstein the theory of relativity and then Einstein claims it his own and publishes it, a number of copies of the original work will be made. One such copy would have been used by the time traveler to study the relativity theorem in the first place. This begs the question that who had actually came up with the original theory. It is not Einstein who invented it as he was taught by the time traveler and it was not the time traveler who invented it as he only studied it from a copy of the original theory. This means that the original theory has been lost somewhere in a time loop. This paradox does not have a particular answer of any sort and still is being pondered upon by many scientists.

Most of these time travel paradoxes can be avoided or explained with multiple timeline scenarios and the Many-worlds interpretation. There is one more paradox which is essentially like a mix-up and is called Polchinski’s paradox.

Time travel is a really beautiful phenomenon for deep thinkers and curious people out there who would like to understand the thin line that separates science from science fiction. There are some more methods through which time travel is possible which hasn’t been discussed in this article like the wormhole theory etc, but that will be for another topic on another piece. Thank you for reading till the end.