Time Travel

       

  Time Travel is a concept of movement between different points in time, generally forward or backward in time using a device known as Time Machine. Time Travel is a much discussed concept in Science and Fiction. let us start with its history.

HISTORY OF TIME TRAVEL

            The time travel in ancient and religious worlds is much discussed in sacred books of Muslims ( The Qur'an, 7th Century AD), Hindus ( Mahabharata, 6th Century BC), Christians ( Bible, 1st Century AD) and other ancient texts but it was not clearly mentioned as Time Travel and more often all of them has a story of a one way trip to the Future.
            Now if we move towards fiction the first thought of time travel was popularized by H.G.Wells in 1895 from the novel "The Time Machine" which gave a broad concept of time machine by mechanical means. Although there are also more stories in fiction which say about time travel like Rip Van Winkle in 1819 by Washington Irving, Looking backward in 1888 by Edward Bellamy, When The Sleeper Awakes in 1899 by H.G.Wells. In all these stories a long sleep was shown as a means of time travel.

TIME TRAVEL IN PHYSICS

       
          Theories like Special Relativity (1905) and General Relativity (1915) by great Scientist Albert Einstein says a lot about Time Travel. Albert Einstein showed that time is relative - it is real, it can vary for different observers depending on your speed. To Einstein Time is the "Fourth Dimension".
          Einstein's Special theory of relativity says that time slows down or speeds up depending upon your speed. A person on a spaceship moving with the speed of light ages much slower than the people on Earth.

ALBERT EINSTEIN

          Now the General theory of Relativity says that Gravity can bend time. Imagine a four dimensional fabric tied at four corners above the ground level, when an object that has mass is kept in between it causes the fabric to bend and that's how it works in space. planets bend the space-time and the curvature of that space-time is what we call "Gravity". Both the theories are proven to be correct by GPS satellites. Due to the effects of Gravity and speed variations of satellites depending upon the observer on the ground makes a day on Earth 38 microseconds faster. This effect is called "Time Dilation" which in a sense makes the astronauts slightly younger than their twins and this difference is caused by the speed, the more faster you go the less you age.
          General theory of relativity also provides scenarios that could make travelers go back in time but this could be very difficult to achieve physically. This can be done by creating wormholes in different points in time as stated by NASA. It also says that they might not last longer and could only possibly allow small particles through them. Since Scientists haven't even observed a wormhole yet then creating a wormhole in space is far beyond what we have today.
          Another possibility is to move a ship around a black hole rapidly or creating such a condition artificially. Around and around they can experience time travel as said by physicist Stephen Hawking in 2010.

TIME MACHINE

          So far you've understood that the possibility of time travel can be only through a time machine which can bend the space-time and the causing the time lines to turn themselves and form a loop called "Closed Time like Curve". For this time machines need an exotic form of matter called Negative Energy Density. Such matter has bizarre properties and its still not proved that it exists or not. Researchers suggests that a time machine can also be built without an exotic matter. It involves constructing a doughnut shaped hole inside which space time could bend and form a closed time like curve and in which the machine can race and complete laps, with each lap it can travel somewhere in the time. But there are many obstacles foe this as well as the gravitational field required will be very strong and precise and we might not know where else it can effect.

AN IMAGINARY TIME MACHINE MODEL

GRANDFATHER PARADOX

          Besides all these problems time travel has some unique unsolved situations. One of it is the Grandfather paradox in which a person goes back in time and kills his grandfather before he even met his grandmother, if it happens then the traveler would never exist. Some scientists say that you will never be able to do that as it is destined and the destiny will somehow interfere your plan and things just take place how they did in the past.
         Some scientists say that time travel is just an imagination and is not possible, travelling at a speed of light would be lethal and causes death as said by Jeff Tollaksen, a professor at the Chaplin University in 2012, also using gravity would be deadly, one couldn't easily experience such a high gravitational force and it might rip you apart.

          So is it possible to travel in time? Since there are many theories of travelling in time it might be possible but it can only happen with the help of advanced technology which for now is not possible!!


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