The mystery of Time Travel

In the beginning, it was all darkness. And then, Bang! Giving birth to an endless ocean of Time, Space and Matter. 

Every day, physicists are discovering the mysterious, mind blogging and deadly secrets of the Universe. One of the most fascinating mysteries of the Universe is Time Travel.

This all goes back to Einstein's theory of relativity, when he showed that Time is experienced individually and it depends on the position and velocity of a certain individual. According to Einstein's theory of relativity, the faster you move through space, the slower you move through time. If you travel at the 99.9% of the speed of light for 7 years, that would be equivalent to 500 years for the people on earth. And if somehow, you travel faster than the speed of light, you'll move backwards in time. (read the last post to have a better understanding of what we're talking about)

 But traveling into the past has been the most controversial topic among the physicists  during the past few decades. There are some paradoxes we face when consider time travelling into the past; one of them is the grand father's Paradox:
Suppose you some how travel into the past to the time of your grand father, just  when your grand father is about to meet your grand mother, and somehow, you convince him not to meet her,
In that case, your father never meets your grand mother so how could you be born in the first place to be able to travel back into the past in order to stop him from meeting your grand mother?

However, some physicists argue that the nature will somehow prevent you to stop your grand father from meeting your grand mother,  That's because universe prevents every inconsistency in its way of doing things. We may not be sure about that but one  thing is for sure, and it is the fundamental property of Universe too, that it ultimately makes sense. So you'll not be able to do that anyway. But the question here is that when you'll born in the world where you time travelled to the past, what will be the significance of your existence in the first place? will you be real you or that baby-you who'll born? Plus, apart from this, when that baby-you will grow up and travel back into the time, it will start a never ending loop and this is again an inconsistency. Well, this is pretty bizarre.

A stronger theory against the grand father paradox is the idea of parallel realities, or parallel Universe. According to this theory, when you'll travel back into the time, you'll enter a parallel universe and nothing will change in the universe where you came from. This may sound strange to you but this theory is widely accepted by the physicists. We'll go through this idea in future but for the time being, you need to know that the existence of parallel universes have been proven  theoretically using the laws of quantum mechanics. According to quantum mechanics, a particle can exist at multiple place in a single point of time. This has been proven experimentally in case of electrons. In addition to this, the murphy's law states that what ever can happen will happen ( but in a parallel reality). But we only live through one group of realities depending on the choices we make throughout our lives.

Anyhow, time travelling into the past or even to the future is still a pretty far-fetching idea.

Because for higher velocities we need a really large amount of fuel which would obviously add to the mass of the spacecraft and consequently we'll need even more and more energy to accelerate it. for speed of light, we'll need infinite amount of energy, according to the theory of relativity.

The good news is that , for travelling into the future, higher velocity isn't the only way.

Because Einstein showed that space bends due to gravity and as the space and time are dependent on each other, when space bends, so does time. And nothing bends time more than the super gravity of  a Black Hole. To understand what I mean is, suppose you are in a spaceship travelling near the black hole i.e. in its gravitational field. Time will pass more slowly for you as compared to your friend who's on earth. Your some hours will mean years to him and by the time you'll reach the earth, you'll probably meet your friend's grand grand grand children.

The methods we discussed  are  the slow kinds  of time travelling, or its like cheating, this is surely not in the way which we've been watching in the movies since our childhood, where one person enters into a time machine and the machine takes him to the future or to the past in an instant.

Actually that idea was taken from wormholes, a wormhole is kind of a shortcut in time, it is actually a distortion in space and time. both ends of the worm hole have same date and time no matter what happens, what I mean is, when you'll enter into the worm hole from one end, you'll appear trough the next end in an instant, while hundreds of years would've been passed for some one who's on earth, it depends on the size of wormhole. The worm hole also works in reverse i.e. travelling into the past, from where you started. The good news here is that nothing in the laws of physics forbids the wormholes, they are theoretically possible. But if theory says that wormhole is the secret to time travel, then what does it takes to make one?

In order to make a worm hole, we need to manipulate the fluctuations &  distortions in space-time found in the sub atomic particles and expand them, this would require very high energies; possibly, the energy released by a dying star when it explodes. So hopes shattered once again. 

However, there is just a slight possibility that nature has already made them for us somewhere in the universe, like it has created black holes. We don't see it coming in near future though.

To conclude, I'd say that time travelling seems to be a far-fetching idea today, but those who allow their imaginations to roll, there is a bright glimpse of hope for them. There was a time when the airplanes and modern vehicles seemed to be impossible for the mankind, and we already know that where we are today with them, so maybe one day, hopefully in near future we'll be able to discover the missing laws of physics that would enable us to accomplish wonders, and that day might not be very far. We must keep in mind that all of the above concepts & methods were from the modern physics, but today, the Quantum physics has radically challenged the way we perceive things. Teleportation; for example, enables us to transfer a body from one place to another, which could be thousands of miles away, in just an instant. Although Human teleportation has don't been done yet, but  Physicists have already teleported  photons, which means transfer of information at the speed of light.

Furthermore, the phenomenon of quantum entanglement, The String theory, Law of attraction, murphy's law and the existence of parallel realities has opened new doors for the mankind through which we'll be able to achieve the things which appear to be impossible today.