Time Travel through movies : Science Behind Fiction.

The inquisitiveness of human mind about space ,asteroids,galaxies always leads to the discovery of new theories, new ideas in the world of science. And when it blends with art and fiction it creates a whole new world for us which we simply call science fiction or sci-fi. It is the genre which attracts the audience regardless of any age group. Though it evolves around scientific ideas, these movies do not showcase the authentic science formulas we usually know. Some movies might do but it is not a restriction. Still these sci-fi movies manages to rise a lot of queries in our tiny head. So let’s talk about some basic science with the help of these movies. For ages we have seen that most of the science fiction movies are obsessed with the idea of time travel. The idea not only attracts the makers but also manages to fascinate a number of audience. To mention a few, there are some prominent examples like back to the future, star trek, twelve monkeys, terminator, interstellar and hundreds more. Let’s start with 1985 movie ‘Back To The Future’. If you are a fan of this genre then ‘Back To The Future’ is definitely something to start with, right? The film simply focuses on a teenage boy named Marty who manages to travel past in order make his parents fall in love with each other. So basically it is about backward time travel and about the changes in the past which leads to a different future. The story is not restricted to the fact that ‘ no changes in the past can alter the present or future’. Let’s take another example which is a more familiar one, it is the 2019 MCU movie Endgame. So in this movie the avengers superheroes travelled back to the past to take the infinity stones in order to prevent Thanos from the snap that wiped half of the universe. So when they travelled back and made changes in the past it did not effect the main future but created a parallel universe with each change. Because in this film the basic condition of time travel was even if you time travel to the past you can’t change your future by altering the past. So hence the idea of parallel universe or multiverse is raised. Similar idea was also involved in the movie ‘source code’ where changes made in the past created a new world and the protagonist managed to stay alive in that parallel reality even he was dead in the main timeline. Though these are considered as some of the best works of its kind, these movies involve more fiction than fundamental principles of physics. But among the other films which are mostly fictional, the 2014 film ‘interstellar’ made by Christopher Nolan tried to hold the science and its fascinating ideas more strongly about time travel. For me it was executed brilliantly as a new age sci- fi movie. Along with the concept of time dilation it also gave us a little idea about time travel through a wormhole. Now the question arises what is a wormhole and how time travel through wormhole is possible. Let’s go back to 1905 when Albert Einstein published his paper of special theory of relativity. It said that time and space cannot be defined separately from each other. Rather they are into single continuum as space time. That means event occur at the same time for one observer can occur at different time for another observer. To simplify we can say time is relative to a particular reference frame. Again according to general theory of relativity space time is a curve incorporating gravity. Gravitational force corresponds to changes in the properties of space and time, which in turn changes the straightest possible paths that object will naturally follow. These conclusions cannot be explained with a few words and may be little difficult for us as we don’t study physics extensively. So let’s go back to movies for now. In the film ‘Back To The Future’ we know that Marty went to past and tried to change a few things. Now imagine what will happen if we become able to change our past! Lets understand this with an example. There is a concept with which many of you might be familiar. It is called grandfather paradox. In this theory if you somehow manage to travel to the past and kill your grandfather at a very young age what changes will possibly occur. In this case your father would not be born and eventually you will not exist to kill your grandfather at past. It will give rise to a paradox and hence the theory is known as grandfather paradox.In the film when Marty failed to unite his parents at first, his existence started to vanish from the main timeline and started to build a paradox .But science on the other hand does not allow such paradoxes. The mathematics of probability prevents such kind of paradoxes. Another logical explanation says that probability bends to prevent paradoxes from occurring. The outcomes would become stranger as one approaches a forbidden act, as the universe must favour improbable events to prevent the impossible ones. Again talking about endgame, each change in the past built an entire new universe. So if we assume that we are able to travel backwards in time and agree to the fact that no changes in the past can make a difference in the future then there must exist multiverse to prevent the paradoxes. Time is not a concept that is obvious to everyone, in fact it is the most arguable one. Though most of the scientists believe that forward time travel is logical and theoretical , backward time travel is impossible. So how we can travel to our future! So let’s recall what establishment was made by general theory of relativity. It suggests that gravity is a geometrical factor which effects the spacetime curve. So if we measure the time near a strong gravitational field with a clock it will tick much slower than the usual gravitational field.Now we are all familiar with black hole. Blackhole is something which absorbs anything which falls into it.Even light can not escape from black hole. The bright boundary surrounding the black hole is called event horizon which have a strong gravitational field. So near a black hole or near event horizon clock ticks much more slowly than on a spaceship orbiting further away. Lets imagine you travel to a part of years has been passed. Dipsikha Barman 1st Semester