In these times of Covid caused distress, a little interstellar travel and fantasy will do no harm. ‘Back to the Future’, ‘Excellent Adventure’ to more recent flicks like ‘Arrival’ and Interstellar’ are all sci-fi ‘time travel’ films. Apart from being paradoxes, they are also confusing and fun with overactive imagination and temporal gymnastics at play. What is ‘time travel’? We travel one year between birthdays, between festivals at the same speed. One second per second. Is it possible to experience time passing at a different rate than one second per second? How much fun it would be to travel back in time and meet people and events of an elapsed time period or travel forward in time and see events that are yet to unfold? Can a ‘Wormhole’ or a ‘DeLorean’ do it for us?
We use Space telescopes to see stars and galaxies that are very far away, actually billions and trillions of kms away. It would take a long time for the light from these faraway galaxies to reach us. So, what we see is what they looked like a long time ago. Can we travel faster than one second per second, so we catch the stars and galaxies as they evolve?
What is time? Albert Einstein more than 100 years ago, said, that time and space are linked together. He further postulated that in our universe, nothing can travel faster than the speed of light (186,000 miles per second) or the faster you travel, the slower you experience time i.e., ‘time dilation’, a property of special relativity. He first realized that time is not constant, as was believed then, but actually slows down as one moves faster through space.
There are scientific experiments to prove this. For example, if one were to use two clocks set to exactly same time, one on Earth, while the other on an airplane, going in the same direction as Earth’s rotation and if the two were to be compared, after the airplane flies around the world, the clock on the fast-moving airplane would be slightly behind the clock on the ground.
The theory is applied to the GPS satellites used to help us figure out how to get to new places or go around the city. Since the satellites orbit around Earth very quickly at about 14,000 km/hr. the clocks on them slow down by a small fraction of a second. Since they also orbit Earth about 20,200 km above the surface where the gravity is much weaker, their clocks are speeded up by a slightly larger fraction of a second. if this is not corrected, the GPS maps might think our home is nowhere near where it actually is!
‘Time dilation’ was first seen in the movie ‘Interstellar’ when Matthew McConaughey and his crew land on a planet with an extreme gravitational field caused by a nearby black hole. This slows ‘time’ dramatically for the crew on the planet, making one hour on the surface equal to seven years on Earth. When the crew returns to Earth, Matthew McConaughey’s daughter is an old woman while he appears as he was, when he left. So much for travelling faster to experience a slowing of time. The larger question However, is, can we travel faster than light?
The Bhagavad Gita and Bhagavata Purana have multiple such examples. King Kakudmi and his daughter Revati, travelled to different ‘lokas’ in search of a suitable husband and returned to earth in future time, a lapse of thousands of years, only to find that everything has changed. Similarly, King Muchukunda, ancestor of Sri Rama was asked to help the deities in ‘Indra Loka’ in a war with the demons. He fought the war for a long time and when it was time to return, the deities advised him, he cannot go back to earth because of time dilation. Even ‘Tripura Rahasya’, a book on ‘Advaita Vedanta’ discusses a chapter about ‘time-travel’ and cites several instances of people travelling to distant worlds and returning to future times. Even Greek Mythology is full of such examples. Did they really have time machines?
Travelling faster than light is more complicated than travelling faster than sound. An aircraft flying above the speed of sound, such as supersonic or hypersonic jet doesn’t change form, even under extreme temperature gradients. However, if an object attains light speed, it would be converted to energy and hence destroyed. Comprehending its travel dynamics would be extremely complex. Since we cannot exceed speed of light in ‘time-space’ concept, why not change ‘time-space’ concept itself by warping or distorting it? Can we then create a time machine to travel hundreds of years into the past or future?
Can we think beyond fantasy and seek some answers? Suppose we build a spaceship that harnesses something really powerful, like a bunch of super-dense matter from a neutron star. This in a way will be able to warp ‘space-time’ enough to briefly pull two distant points together, the way that the edges of the bed sheet would come together if a heavy weight is dropped in the middle. Such warps in ‘space-time’ are ‘wormholes’ This is no fantasy for it occurs naturally all the time in space. If only we can build such a spaceship, we can travel enormous distances extremely quickly.
Would we really want to travel into the past? That might destroy the future. What happens if one were to go back in time and kill one’s grandfather before the father is conceived? How then is it, that the person is still alive? You can fancy further. On the other hand, to travel years into the future, we would either have to use intense gravitational acceleration caused by black holes, or go into space at the speed of light. Still, the realisation would only be that our time has flown away. So, enough of fantasies for now. With the technology at our command today, all that we can do is jump a few microseconds into the future. Maybe, that also is the truth of the Universe, for no one from the other world has ever come to invade us. Until that happens, we can travel by the good old transport systems we have. If they reach us safe in ‘time space’, we live for another day. If they don’t, well, we can meet in those other worlds.