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Time Travel! Fantasy Or Reality?
The very concept of time travel has been a fantasy interest for the humans since very ancient time. A lot of Hollywood movies have been featuring this concept for years. But what we are interested in is can the concept of time travel be made real? Can we move into past to see the dinosaurs? Can we move 1000 of years into future? To explore these possibilities lets start with the theoretical challenges and the feasibility of Time Travel................
Lets start with Worm Holes..The existence of which at subatomic level has been confirmed scientifically and is widely accepted. So, what a worm hole is, you might have seen it in the movies like Star Wars where space ships enter a hole at one part of universe and exits at another without any time delay (see the top image). The same concept of worm holes is there which has been confirmed at sub atomic level. That is they too connect the two far points in a region. And recalling the theory of Einstein which said that space and time are interrelated rather than being independent. Thus, the worm holes also connect the two points in different time i.e. it is a portal for time travel. But the problems with these worm holes is that they are so small that a electron can hardly get into it also they last for negligible time i.e they are being continuously created and destroyed with each linking different points in time and space.
So can we think of time travel by developing suitable technology which can enlarge the worm holes for human to let into it and also not letting the worm holes to evaporate that quickly.
Suppose one day we are able to do that and a person uses this portal to get to the time when his own grandpa was a child. Now think what if he kills him. Seeing the time flow in one direction it would seem impossible as how come that time traveler born. The existence of that time traveler will be under uncertainty. And this the famous Grandfather paradox which naturally puts a constraint on traveling in past. Lets consider a more simple example A person say time traveler loads his gun and enters the worm hole which take him just 5 minutes into the past, where he see himself loading the gun. Consider what if the future man kills himself. Again its a paradox as how come he fired if he was killed before loading the gun. And this is termed as Self paradox. Considering these things may convince that the nature doesn't allow traveling into past. Lets see why this is so....
The time as we perceive flows in one direction how ever the rate of flowing may vary as shown by the theory of relativity. And the flow of time is the most irreversible process of nature and traveling in past by reversing the time thus may not be ever possible as it would require to change the condition of entire universe to a state at which it was at that point of time in past which really sound impractical but it is a theoretical way to move to past.
So what we conclude from our discussion: Is the time travel not possible? Can't we ever make this fantasy real?The answer is we might not be able to travel into past but moving into future is definitely possible and one day we will have the technology to move into future.Lets see how the theories predict traveling into future is possible and feasible.
The theory of relativity proposed by Einstein and Lorentz clearly states that the rate of flow of time is different in different parts of Universe being slow at the region with higher gravity. The practical example of which is seen in the Satellites orbiting the earth they develop a slight time dilation in their clock with respect to that on earth, it is not because of the faulty technology rather a simple consequence of theory of relativity. So how can this help us to travel into future? The answer is simple we are required to goto a place in universe which has very high gravitational power, spend some time there and then return to earth when he return he will be in future....how come? It is because if he spend 2 days there according to him then when he returns he would find more than 2 days have passed on the earth. So, where are we required to go to move to a greater depth into future with spending minimum time? The answer is to Black holes. Now we can't move and leave on a black hole as its mighty gravity would make ourselves crush under our own weights.But there is still a way, we can orbit around the black hole in a spaceship with sufficient speed that the centrifugal force overcomes the gravity. Our galaxy has one of the biggest black holes of the Universe and it is right in the center of milky way. Calculations based on relativity show that 1 year spent there would be equal to 2 years on the Earth.For example if a time traveler goes there in 2012 and spends 10 years according to his clock and calender and then returns on earth. Then he will have the earth of 2032. That is he would have moved 10 years into the future.
This method might not seem practical as one has to move to the center of galaxy whose distance is so large from earth that going there is itself a challenge. And also one can't move to far into the future say 500 years and for that, time traveler must spend 250 years orbiting the black hole which is beyond the human age.So there is a another way to move easily 100s of years into the future.One has to do is that he has to move with speed as close as possible to speed of light. The more close the speed the faster will he move into the future.As the theory of relativity predicts that the time slows down in frames moving with larger speed than a reference frame. And the fact that the speed of light measured is independent of the speed of the measuring frame.
But there a problem how do we do it? The answer would be one has to move in a space ship with that speed but developing that is a challenge! The speed that is of even the fastest things made by the man is now feasible for time travel as we will have to spend years for moving a week into the future with the speed of Helios 2 (the fastest thing by man). We will need the space ships with nearly 70% speed of light to really have a feel of time travel. Moving in which we can move 1 year into the future having spent just one day in the ship. Hope someday in near future we will have one and the humans will be able to move into thousands of years in time.
So, here we reach the end of our discussion, i hope to got an idea of time travel. I would like to mention an interesting thing here, the travel into future is allowed and that into past is restricted again showing the unidirectional nature of flow of time.