Time travel is one of the most interesting and controversial topic in the world of science. Majority of people think that time travel is not a true concept and is only a science fiction. But in the world of science, science fiction is bound to exist but some things are based on real experiments too and they are said to be scientifically proven. But some things are not proven by real experiments but are theoretically proven by mathematics and hence they are said theoretically proven. And time travel is one such concept that is not proven practically but is proven theoretically by mathematics.
The theories of Einstein and many other scientists actually allows time travel. And this is the reason because of which time travel became a controversial topic. Like said earlier the thing about time travel not being practically proved is right and wrong at the same time. On a small scale time travel is actually proven. In an experiment time travelling was done but only for a few Nano seconds. This is not a long duration but at least we got to know that time travel is possible.
This experiment was done in October, 1971 and it was called Hafele-Keating experiment. Astronomer Richard Keating took four atomic clocks and boarded on an airplane and he flew twice around the world. When he came back after taking two rounds of earth and came back to the naval observatory in the United States he matched the time on both clocks and the amazing thing was that the clock in the observatory was some Nano seconds faster than the clocks in their plane.
So if we try to understand this with an example, if the initial time of both clocks was 4 hours 10 minutes and 10 crore 10 lakh Nano seconds and after 4 hours when they came back the time on both clocks should be 8 hours 10 minutes and 10 crore 10 lakh Nano seconds. But the time in the clock of their plane was 10 lakh Nano seconds behind the time on the clock of observatory means the time was 8 hours 10 minutes and 10 crore Nano seconds. Now some people will say that the difference is just few Nano seconds and it doesn’t make any difference and may be the clock was damaged. But let me tell you that the experiment was not done using any general clock or any advance electronic clock. But was done using an atomic clock. Atomic clock is the most accurate clock in the world and it can record even the trillionth fraction of any second.
By this experiment it was scientifically proven that the clock kept on a fixed place on earth was faster than the clock kept in plane. So what does this mean? Did the clock kept on earth was faster or the clock kept in plane was slower? Actually the clock kept in plane became slow. And this means that the faster an object moves the speed of time on that object will be that much slower. And this was the one and only proved experiment in the history that proves time travel. And this was an official experiment and nothing like a mysterious time machine was involved. The clock on earth was kept in one place and the clock in plane was travelling at the speed of 900 km per hour. This means that for any moving object time passes slowly compared to an object that is resting on one place.
This means that if we look at it deeply we can notice that whenever we travel on a bus or a car our time passes slowly compared to when we are just simply sitting in our house. Yes, this might sound weird when we hear it but this is true there is definitely the difference of the fraction of Nano seconds. So if we want to do time travel in future this method can be used. But what can we do by travelling into the future by just Mille seconds, right? So if you wish to go into the future by 5 years, then you will have to travel really fast at great speed. And the same exact thing was said by the great scientist Stephen Hawking. In most sources of time travel states that if you travel at the speed of light then you can do time travel but no one tells the logic behind it which was explained earlier. That’s why it is said that if you travel at the speed of light then you can do time travel.
What happens is when you travel at the speed of light the time will pass really slow for you compared to someone who is in earth. If you travel close to the speed of light or at the speed of light in a spaceship then you will be doing time travel. If you travel in such a spaceship for 3 years and come back to earth then you will realise that 900 years have passed on earth. Because time passed slowly for you but not for the rest of the world so the amount of time passed was less for you but for everyone else in the world it was normal time. Now most people will ask how you can just casually say that if you travel 3 years then 900years will pass. There must be some perfect ratio.
Yes, there is an equation and ratio and you can read about it on the official page of Wikipedia. Like said earlier the time in spaceship will be slower and compared to that the time will pass much faster on earth but not for you. You will be travelling comfortably on your spaceship and when you will come back many years have already passed. So in this way you can travel into the future. But one limitation is that you won’t be able to come back from that future. If you go into the future using this method then you will have to stay there forever.
So this is the science behind going into the future. But why this method is not practical and just theoretical? That is because it is obvious that making a train that travels at the speed of light isn’t practical at all. Because even if we make such a machine we won’t be able to provide any source of power to operate it. So we can say that time travel into the future is not impossible but it is not practical.
Since we talked about time travel into the future now let’s have a look at time travel into the past. We cannot go into the past by using something that travels at the speed of light. So this is even more controversial than travelling into the future because of a paradox called ‘the grandfather paradox’. This is a famous paradox and it states that imagine you somehow managed to do time travel into the past and you killed your grandfather, then how is it possible for you to exist in the present? If you killed your grandfather then how did you take birth? You were not even born so who killed him? This does not make any sense. This is a super confusing problem which has no proper answer. And that’s why many people think that travelling into the past is impossible.
But Stephen Hawking said that this is possible and the method is wormhole. Albert Einstein had said about this earlier and another name of wormhole is Einstein Rosen Bridge. So what is wormhole? This can be explained as a tunnel that joins two places or two time zones in the universe. But this thing is very much non theoretical. Scientists argue that wormhole exist but no one has seen that until now. So you can say that the chances of such a wormhole existing is very low and this is a mystery. And like every other unexplainable thing it has only theories that exists. This is just mathematically prove but not practically.
The most interesting method of time travel is travelling through a time machine. But time machine will seem like very much out of a science fiction. To operate this we will need a special type of energy called negative energy. And negative energy is also a theoretical concept like any other typical mysterious concept is just mathematically proven. And no one has any special formula for making a time machine. But we can still hope that in future someone might make a time machine. So we can conclude that time travel into future is practically possible for sure even though we cannot make something that travels fast enough to do that. But time travel to the past is possible just mathematically but not practically.
So just imagine a time machine is made so would you like to travel back into the past and correct any mistake or you would like to travel into the future instead?