What is time Travel?
As we all know that we humans consider ourselves as unique. 1+1=2, it is a scale created by us to simply simplify the equations. Humans have coded each and everything to make things understandable. Due to this, we forget what our brains are fully capable of acquiring. To understand physical beings, we created dimensions. But do you think only three dimensions are sufficient to understand any event?
Suppose a car is moving on a straight road. Right now it is in 1-D motion. If it takes a left or right turn, this adds up the second dimension. When it moves up or down the hill, it makes the third dimension.
But if we shoot a video of the moving car and fast forward it infinitely, a time will come when it disappears. So how can we prove that there was a car present? Time is the only reasonable answer to it. Time is unity.
Differences in ideologies
Issac Newton stated that time is like an arrow which once fired cannot be reverted back. It always travels in a forward direction and 1 second on Earth is 1 second everywhere in the universe. But if we take the case of Einstein who said that time is like a river which is filled in between planets and stars and it speeds up and slows down too.
What is General and Special relativity?
The theory of general and special relativity given by Einstein in which he stated certain geometries that might allow traveling to the past or future. He said that the empty space can be curved, what we call gravity is merely a consequence of those waves. He predicted that matter curves space-time and we can see the curvature by following the path of light.
For understanding, we can suppose space as a trampoline and put a heavy object at the center of it and now start rolling marbles across. Most of the marbles cross undeviated but some of them bend as they get close to the dip in the trampoline. This is what happens in the real world and we can trace the presence of curvature in the experiments.
Travel in Time
There are many ways to time travel as predicted by scientists such as through a wormhole, by a black hole or a time machine, etc.
A wormhole also known as Einstein-Rosen bridge is a pathway that can be visualized as a tunnel with two ends that connect different points in time or space. They are consistent with the general theory of relativity and could connect long distances such as a million light-years or more.
A black hole is a region in space where the gravitational pull is so strong that even light cannot escape from it. The boundary of the black hole from where no escape is possible is called the event horizon. Time slows down near the horizon. So a spaceship circling a black hole will experience a time difference with the people present on Earth and hence travel to the past.
These are all theoretical concepts and none of them have been proved experimentally but what if by some means a person travels back in time. Will there be any consequences?
How many types of Paradoxes in Time Travel
Time paradoxes whether to the past or future are an inherent feature of time travel. Generally, two kinds of events can occur.
The first one being the Grandfather Parado. To understand this let us take an example. Consider a boy goes to the past and eliminates his parents before he was born or somehow changes the outcome of his birth, then it will result in
a paradox and hence will affect the future events going to take place.
The second one is the Casual Loop. It is a paradox in which you send someone in the past to change the incident that has led to the bad happenings in the future but the person sent back is the reason for starting the problems (as in The Terminator movies). Hence it forms a loop in spacetime but the origin is not known.
Solving the Paradoxes
A paradox is solved by finding errors in the given theories. One such method is the Self Consistency Principle. As we see in the upper example when the boy is about to eliminate his parents, there is something that prevents him from killing them. According to this principle there are some hidden laws of physics that say we cannot change the events that have
happened in the past. But personally I don’t get it.
What is Multiverse?
Another theory is the concept of the multiverse which suggests that if the boy is about to pull the trigger there forms an alternate timeline i.e. the boy is not killing his parents but killed someone else and entered another universe. This means we can go back and forth in time and change the past but in turn creating new multiverses.
To conclude this argument one can say that time travel is impossible or not likely to happen in
the near future but according to notable physicist Brian Greene:- “The bottom line is that time travel is approved by the laws of Physics”.
It might be possible but the trick is that the energy necessary for initiating the time machine or to travel at the speed of light cannot be obtained from an atomic bomb but only from an exploding star. This means that it should be an advanced civilization where humans are able to harness the energy of a star.
Written By Abdus Samad