Time travel : fantasy or reality?

Hello time travelers, fasten your seatbelts because it’s time to buckle up for a journey through the unreal. It’s not a lunatic dream of a child, but a step forward to the future, the future of humanity.

After hours and hours of debate it still remains a mystery that time travel is a fantasy for movies and fiction or it can be achieved in reality.

Few years earlier Stephen Hawking proposed to be having experimental evidence that time travel is not possible. He organized a party for so called time travelers. He sent the party invitation only after the party was over. He waited and waited but no one arrived.

But recently in his final book, “brief answers to the big questions” he considered time travel as a very serious question, keeping our hopes alive for a future resembling any sci-fi plot.

Is time travel possible?

Well, to answer this question, we need to first understand what is time. Unfortunately, the answer is not that straight forward. Initially time was thought to be absolute up until Albert Einstein proposed his theory of relativity. According to him time is an illusion and space and time are relative. Well, this may seem absurd, but it’s quite simple.

According to him time slows down or speeds up depending on the velocity relative to someone else. If two men are travelling with same velocities, time will pass in the same pace for both of them.

This is what happens to us on earth. We all are in constant motion with the earth. Hence for all of us time passes with the same pace. But when it comes to 2 men travelling with different velocities relative to each other, the time varies. 

For example, the astronauts are constantly time traveling, because of their velocities in space, though the time difference is one in a billionth. This is known as time dilation, which can be considered as the principle of time travel. Well if you want to learn about relativity more clearly. Check out this video, I gained a lot from it. (Credits to Ted-Ed)

Can we travel back in time?

Whatever we have learnt so far can be compared to travelling into the future, though the time difference is really insignificant (like in the case of astronauts). But, if we travel with really high velocities relative to that of earth, then the time difference between you and the people on earth will be significant, which is actually travelling into the future. 

So, Einstein’s theory actually allows us to travel to the future. But the real gist of time travel is to travel back and forth through time.

One important conclusion from Einstein’s theory of relativity is that the speed of light is constant. And the law of causality follows that nothing can travel faster than light. That is the cause of an action should precede the effect (flow of time is unidirectional). This makes travel to the past far from possible.

But if by any means we can travel faster than light, then the law of causality doesn’t hold good and gives us an opening to travel back in time. Though the possibility to travel faster than light seems impossible, at least as far as today’s technology is concerned. But it’s a topic of discussion for another article.

Other theoretical possibilities

Hours and hours of research have gone into this field making time travel a hot topic of debate. This gave rise to various alternate theories for travelling through time. This includes black holes, wormholes and cosmic strings.

Black holes are very very dense celestial bodies whose gravitational field is so high that even light can’t escape through it. Well Einstein’s theory of relativity considered time as the 4th dimension along with the 3 dimensions of space (length, breadth and height). Time and space together constitute a fabric of space-time. It is said that mass bends the space-time fabric. 

The enormous mass of black holes tend to bend the fabric. Hence if a ship were to move around a spinning black hole, theoretically it will travel through time. But the speed of the ship must be in the order of that of speed of light.

                  

Wormholes on the other hand are referred to bridges that connect two points in space-time. So this could potentially be one more method to travel through time. But wormholes are said to be observed in quantum level and they collapse rapidly.

To create a macroscopic wormhole, it’ll definitely be an enormous task and is practically impossible at least to the reach of our present technology. Well, wormholes are a topic of discussion for another blog post.

             

Cosmic strings are narrow tubes of energy present throughout the universe. They are said to be having enormous mass which can wrap space-time around them. They are said to be infinite with no end or to be present as loops. 

Two parallel strings are thought to be bending space-time in a particular orientation. This allows feasibility for time travel, theoretically. We’ll talk about them properly, some other time.

Paradoxes limiting time travel

Paradoxes are situations where 2 or more parts of it seem impossible of each other. Time travel gives rise to a typical paradox known as “The grandfather paradox” Where if you travel back in time and kill your grandfather, then you will not be born, hence you can’t travel back in time, and your grandfather is alive, which in turn means you are travelling back and killing him again. The cycle keeps continuing on and on. 

This clearly limits time travel because if time travel was possible, then the situation will be impossible to predict. It will be full of confusion.

Similarly, imagine yourself traveling back in time and preventing a war to happen. After some time this will lead your future self with no motive of traveling back in time and hence the war won’t be prevented. Thus the possibility of time travel seems impossible considering such scenarios.

So far we have not witnessed anyone from the future. This may be enough to conclude that time travel will never be achieved in future. Because if it would have been so, then we must have witnessed something like that.

Possible solutions to the paradoxes

Talking about changing your future by travelling through time. Maybe if we travel through time and do kill our grandfather, maybe a separate alternate timeline will be created where I’ll not be born. And this won’t affect my history. 

Also, we know that the sub-atomic particles do exist in two states simultaneously in the quantum level, commonly known as the quantum entanglement. Similarly if time travel was possible then there may be two situations happening at the same time. That is your grandfather is alive as well as dead at the same time. Well this may seem weird but possibly this is a solution to the grandfather paradox.

You can check out the video from minute physics on this topic. Credits to minute physics, I learnt a lot from it. The link of the video is given at the end of this subtopic.

 

A research was published in “classical and quantum gravity” Where Dr. Fabio Costa stated that, “Try as you might to create a paradox, the events will always adjust themselves to avoid any inconsistency”. He discovered mathematically that paradox free time travel is possible in our universe.

Finally, is it fantasy or reality

Time travel is a fantasy or reality still remains a mystery and only “TIME” knows what is going to happen. It is only possible if we can develop the technology to back our theoretical speculations. Some say that it will be a serious threat to humanity itself. Contrary to those, others say that it will be a boon and with proper administration this can be used to do literally anything. Will it be a boon or a bane can only be speculated. 

Though the possibilities of time travel in the near future seems very bleak, but you and me still hope that it will be possible and we will be the time travelers of the future.