Yes. In fact we all are time travelers traversing through time. As every second, every minute passes by, we are in fact traveling through time. So the key question is, can one travel through time at a different rate than it normally is (say 1 day per day) – that is the context in which we are having this discussion.
So if you were to ask, can one travel through time at a differential speed? Well the answer is half yes. Half yes because, this travel is possible only one-way. One can travel into the future, but can never travel back to the past. Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn’t share this multi-directional freedom. “In this four-dimensional space-time, you’re only able to move forward in time,” Charles Liu, an astrophysicist with the City University of New York, College of Staten Island and co-author of the book “One Universe: At Home In The Cosmos” observes. So all the movies where the hero goes back in time to save his college sweet-heart is nothing but extended imagination. And at least for now, everything around time travel is imagination. But we have some theories that prove such a travel is possible, one way at least.
Time travel has always fascinated man and it is true that it is possible well within the laws of physics. Isn’t that amazing… I was really very amazed to know that it was indeed possible and the best part was when I really started understanding the concepts. I have summarized here in my own words what I understood about this possibility and if I can understand, I am sure each one of you will.
Before we start there are some things we should know. This will just help you understand the concept better as we move on.
1. Time, like speed and distance is one of the dimensions in physics
2. Light travels the fastest and according to the laws of physics nothing can travel faster than or equal to the speed of light.
3. As speed increases, the speed at which time moves decreases
4. Time, unlike distance, is a relative measure and not absolute
5. Laws of physics permit time travel into the future and not into the past
6. It’s possible to bend time and cut across to great distances
The video below is a nice example of the points above in general and point 3 in particular.
So how do we say that time travel is possible?? Physicists like Stephen Hawking and Albert Einstein explain it in simple terms. As you start traveling faster and faster and faster, till about you reach close to the speed of light, time slows and slows and slows down around you. So if for example travel around a black hole (that is without getting sucked into its massive gravitational pull) or travel across space in such great speeds, you will eventually slowing down time. This means, if you travel for 50 earth years in that speed, you would have actually traveled only 25. And that means, if you have started your travel in the year 2000, while you have experienced 25 years and reached 2025, the earth years would have already reached 2050… which technically means you have traveled into the future.
Now why should time slow down as you travel faster? Here is an example: Imagine we build a huge space craft carrying people that could accelerate close to the speed of light. Now as the space craft is moving at a speed close to the speed of light, what happens if a person throws a ball inside the space craft… It tends to reach the speed of light or probably would travel faster than light. But that’s not what is possible as per the laws of physics. So to ensure that the ball thrown inside the fast moving space craft does not reach the speed of light, time automatically slows down around the fast moving space craft. Now even the combined speed of the craft and the speed of the ball thrown inside will not equal to the speed of light.
And you might be wondering why I have not discussed the grandfather paradox here. The grandfather paradox is normally discussed whenever one talks (or writes) about time travel. The reason I have left that out here is purely because my explanation covers only travel into the future and the grandfather paradox comes into play only when you talk about travel into the past. And to my mind, travel back into the past does not sound quite possible with the kind of knowledge and understanding I have on time traveling. But here is an interesting video that claims to have captured a time traveler on tape. This is a scene from a Charlie Chaplin film called The Circus. In the video you will see a person who looks like he is talking on a mobile phone and mobile phones did not exist at the time this film was made.
And this may not be strictly within the context we are discussing here, but I am tempted to talk about Deja vu. Deja vu is a French phrase meaning ‘already seen,’ referring to the distinct, puzzling, and mysterious feeling of having experienced a specific set of circumstances before. A woman might walk into a building, for example, in a foreign country she’d never visited, and sense that the setting is eerily and intimately familiar. Some attribute deja vu to psychic experiences or unbidden glimpses of previous lives. So could this mean that the person has undertaken a travel to the future and he is simply revisiting what he has seen earlier?? I keep wondering…
Is time real? Does it flow in one direction only? Does it have a beginning or an end? What is eternity? None of these questions can be answered to scientists’ satisfaction. Yet the mere asking of these questions stretches our minds, and the continual search for answers provides useful insights along the way.