Isn’t time travel something that we all think about? Whether sitting in a class or writing an exam, don’t we all wish we could go back to a particular time in the past or see just a glimpse of the future? From brain storming movies such as ‘The Interstellar’ to lame comedies such as the ‘Hot tub time machine’, time travel is a concept that not many people understand but can certainly relate to.
But before anything about time travel, let’s get to the fundamentals, what exactly is time?
Most people think of time as a flowing river, and flow that cannot be reversed, something that has been going on in the same direction since the beginning of the universe. To Einstein, time was the ‘fourth dimension’. Time is also called an illusion or is just an expression for the measurement of separation among events that might occur in the same location.
But is it really possible for us to go into the future? To disrupt something that’s so constant?
Travelling near an object like a blackhole can make us travel into future, but how?
According to Einstein, time slows down around an object with a huge mass like that of a black hole(a blackhole is a singularity, which means that the mass of on entire star is concentrated at a single point and hence it has a large density). To understand this better, assume the entire space time as a rubbersheet(let’s call it the space time fabric).
Anything having a mass will make a curvature in the space time fabric. An object such as a blackhole will result in a bigger curvature as compared to our lighter objects.
Since time can be assumed as straight lines running through space time, it will bend along this curvature. Therefore time takes a longer route to travel giving us the impression that the time has slowed down. This is known as gravitational time dilation. This means that we experience time dilation even on earth like when standing next to the great pyramids, the time actually slows down, but its effect is next to negligible. Therefore, time slows down quite a bit around the black hole causing anyone near it to age slower as compared to their counterpart on the Earth. When the person travelling near the blackhole returns to the earth, he would have aged slower and hence would actually step into the future.
Another way to travel into the future is using the special relativity by Einstein. According to him, time speeds up or slows down for an object depending on how slow or fast it is travelling relative to something. That’s the theory of special relativity.So as an object approaches the speed of light, time actually slows down for the object. For instance, hands of a clock in a moving train moves more slowly than that of a stationary clock. Anyone travelling inside the train wouldn’t feel any difference but at the end of the trip, the clock would have slowed down by the billionth of a second.
But how can we use this to travel into the future?
Imagine travelling in a train that has a speed of 99.99% that of speed of light (hypothetically), then the time for the passengers inside the train would slow down so much as for every one year spent inside the train, 225 years would have passed on the outside world. So if a person successfully completes his trip on our superfast train, his new destination would be 224 years into the future.
This situation is still hypothetical, but if we do manage to go fast enough, who knows what the future holds for us.