How is Time Travel possible?
Can we ever travel to the future? Or can we ever go back to the past? Can we skip a hundred years, while just aging ten or twelve years?
Time travel, which is nothing but moving between different points in time, has been a popular topic for science fiction for decades! Though some scientists have come up with their own theories of time travel, others discard this concept thoroughly.
To understand time travelling, first, let us understand - time.
While most people believe that time is a constant, physicist Albert Einstein showed that time is an illusion. He mentioned time to be relative; it varies for different observers —depending on their speed through space. He also said that time is the ‘fourth dimension’. Space is believed to be a three-dimensional arena, which provides a traveler with coordinates — such as length, width, and height — showing location. Time provides another coordinate — direction — although conventionally, it only moves forward.
Einstein’s theory shows that if you move FASTER through space, you move SLOWER through time. Meaning, imagine you have a twin. You both are 20 when you leave your twin on Earth and go for a voyage through deep-space on a spaceship. Now imagine the spaceship is travelling nearly at the speed of light. When you will come back from your trip after 2 years, your twin would be 50 years old, when IN FACT you’d only be 22!
And that is possible IF you get your hands on to such advanced technology that can make you travel almost at the speed of light. While we are still in search for such a technically-advanced spaceship, there may be more ways than one to travel through time!
We know, gravity warps space-time. Picture a four-dimensional fabric called space-time. When anything that has mass sits on that piece of fabric, it causes a dimple or a bending of space-time. The bending of space-time causes objects to move on a curved path and that curvature of space is what we know as gravity.
The closer you are to the gravity, the slower you move through time. Imagine you are living in a hill station, and your friend is living near a beach. Because of being away (though negligible) from the gravitational pull, you would age faster than your friend who is on that beach! These changes are barely recognized by us because of the little difference in magnitude. But the scientists, have proved this to be correct!
We know that around a black hole the gravity becomes stronger. Hence, time moves slowly. So on a planet orbiting around a black hole, time would move slow. This is what happened in the movie Interstellar!
Scientists have found out yet another way how time travelling can be made possible. And that is through — a wormhole.
What is a wormhole?
A wormhole is a sort of tunnel that could connect extremely long distances such as a billion light-years or more which bends and create curvature in space-time. These tunnels can link different universes or simply different points in time.
Assume that a plane is going to Paris from Delhi. Since Earth is a geoid shape, the plane cannot directly travel to Paris. It ascends up to a certain point and then descends to its destination. This example describes the same situation with wormholes. If the plane was capable of directly travelling from Delhi to Paris, the journey would be much shorter even when the velocity of the plane was the same in both the scenarios.
How is it formed?
Earlier, physicists at MIT had predicted a way for the formation of “wormholes,” or gravitational tunnels. The group showed that by creating two entangled black holes, then pulling them apart, they formed a wormhole — essentially a “shortcut” through the universe — connecting the distant black holes.
While some theories predict these existed at microscopic levels in the early universe, they also found that these wormholes were likely unstable and would have collapsed quickly.
In order for a wormhole to actually work for time travel, there would need to be some kind of exotic matter. To stabilize the wormhole, theory demands this type of exotic matter — an unknown form of matter fundamentally different than the stuff that makes up everything around you — would need to have negative mass and pressure, something scientists have never seen, nor expect to find any time soon.
That is a long shot. But the theories do not stop there!
While we haven’t come up with a guaranteed way to actually travel through time, the field is constantly changing. Advances in quantum theories could perhaps resolve this mystery and one day we could experience it in real life — and not just only through science-fiction!