Who don’t want to see future? Like after 50 years or 100 years, how would this world look like? How would people think, eat and live? What would be the technologies? What would be the tradition and culture? Who would be the famous people of those times? And so on. Lots of questions about the future fascinate people and make them search for the possibility of time travel.
This passion makes people to understand Einstein’s Theory of Relativity. This theory requires sufficiently talented brain, especially to understand the mathematics behind it. However, if we start thinking that the speed of light is unchanged everywhere in space, as Einstein did supporting the idea of Maxwell, then anyone can see the possibility of time travel using their simple concept of classical physics. Human perception about time has been like an unchanged thing, we feel time as if a fixed quantity. We associate time with our perception; like our brain considers one second for heart beat of 70 times. So it is all about our brain who let us feel.
I want to present a case similar to twin’s paradox, consider two people one in earth and another in spaceship. I want to apply just one condition that the time of spaceship is slower than the earth. Obviously, the slow in time results slower in the beat of heart. That means the heart beat rate of spaceman is slower than the earthman. Let us consider the time in spaceship is just half than the time in earth, like for half second in spaceship is whole one second in earth. Then the spaceman’s heart beats only 35 times, while earthman’s should beat whole 70 times. Hence the every action and activity of spaceman is slower than earthman and so the physical growth and development of body. So the growth and development of spaceman is slower than the earthman and spaceman becomes still young while earthman becomes old.
This whole concept gives us clue for the time travel. We can see the future if our growth and development slows down. If our activities and growth becomes such slower, like for 1 day of our becomes 1 year for normal people; we can reach to 10 years later time in 10 days. It looks like a dream, since how can be our activities slow down? How can be our heart beat slows down to such an extent that we just completed one heart beat while normal people on earth completed their heart beat 360 times? It is may be the nature or maybe god that has given us this facility. It is all about increase in relative mass resulting slower in time.
The first option is going to fast moving vehicles or spaceships as I described earlier. Your velocity must be near to the speed of light (0.99 c). From Einstein’s relativity, as v→c, m→infinite. This mean our relative mass will increase hugely. Our every action performed becomes such slower that we see light still traveling at c, even though we are at a spaceship traveling at c. Using this concept we can travel 80 millions light year distance in our 80 year lifetime. Nature has given us such facility that we can travel half way of our galaxy in our lifetime though it is at 80 million light year distance. Coming to the point, we can have slow in time if we travel near the speed of light(c).
Second option is gravitation. A high gravity mass object increases the gravitational energy of any small object under its influence. Increase in gravitational energy increase its relative mass and in consequence slow in time. But our earth is not sufficient for such large gravitational field. For this we need a highly strong gravitational field mass object. That object could be a black hole; a good black hole for this purpose is right at the center of our Milky Way galaxy. By some mechanism, we have to reach there and orbit around that black hole so that we might travel in time. But detail calculation shows that even if we orbit round that black hole for fifty years, earth time would have passed by only 100 years. So this provides very slow facility of time travel. Comparing two alternatives, first one look possible, but we can never reach to the speed of light not even near to it. For second option, reaching near to the black hole is dangerous and very risky. So it seems like our dream to travel in the future.
Third option, which is only a hypothesis are warm holes. A wormhole is a theoretical 'tunnel' or shortcut, predicted by Einstein's theory of relativity, which links two places in space-time.
In such warm holes, there is negative energy that pulls space and time into the mouth of a tunnel which emerges out into another universe. Unfortunately, these real-life time tunnels are just billion-trillion-trillionths of a centimeter across and too small for a human to pass through. But some scientists think it may be possible to capture a wormhole and enlarge it many trillions of times to make it big enough for a human or even a spaceship to enter. Anyway it is only hypothesis till now.
(This article is inspired from a Discovery documentary show).
