On the 23rd of November 2018, BBC’s science fiction series “Doctor Who” will mark its 50th anniversary. This TV series has played a huge role in how science fiction and the concept of time travel are viewed. “Back to the Future” and “Star Trek” are two other popular shows that have influenced the idea of time travel. But is time travel really possible?
Time travel has been a topic of contention for many years.
Developed in 1905, Albert Einstein’s theory of relativity suggests that traveling in time is possible. This theory proves that space and time are aspects of the same thing. Time moves at different rates for people, especially when your speed relative to other people’s is close to the speed of light. What this means is that if you were to leave the earth in a spaceship travelling at the speed of light, even though you will have spent only a few years on board the spaceship, many years would have gone by on earth.
If this theory is possible, then astronauts are actually time travelers. These people travel at high speed and live on the International Space Station while in space; because the ISS travels at the speed of 8 kilometres per second, astronauts onboard tend to age a lot less than the people on earth. No wonder when Astronaut Scott Kelly came back from the International Space Station after one year, the age gap between him and his identical twin Mark had widened by a small margin.
Scientists have suggested four ways in which the concept of time travel can become a reality.
Through the wormhole
Einstein’s theory of special relativity states that it is possible for travelers to go back in time but the formula for time travel is difficult to arrive at. One option will be to travel faster than the speed of light. This means traveling faster than 300,000 kilometres per second. Einstein’s calculations show that an object traveling at the speed of light will have an infinite mass and zero length.
But an easier option, according to NASA, is to create ‘wormholes’ between different points of time in space. Even though Einstein’s formula can be applied here, it can only be used for very small particles and would likely collapse in a very short time. The technology needed to create these wormholes are years away from what we have today.
Cosmic strings are one-dimensional cracks in the universe that could allow people navigate through time. Cosmic strings have no end as they are infinite or constantly in loops. Scientists believe that cosmic strings were formed billions of years ago, just a few moments after the big bang that created everything. Because these cosmic strings are very high in mass, they have a very strong gravitational pull.
Research has shown that gravity has the ability to warp spacetime – which is the connection of time and the physical universe. According to experts, when two cosmic strings are parallel to each other, they will bend space-time in such a way that makes time travel possible.
But the problem with this system is that cosmic strings exist only in theory, and even if we come across a cosmic string anytime soon, it will take one that is half the size of the entire universe to travel back just 12 months in time.
Through a black hole
Black holes are described as natural time machines. According to Stephen Hawking, if we could create an artificial condition where a huge structure rotates continuously or if a ship can actually move rapidly through a black hole, the occupants of the ship will experience time at half the speed of people far from the black hole. This means that they would be moving through time. For instance, if they circle round the black hole for 5 years, people elsewhere would have lived 10 years of their lives, however, the ship will have to travel at the speed of light for this process to work, a feat that is not achievable yet; even if it were possible to travel at that speed, chances are the ship will fall apart from traveling at such high velocity. Another potential difficulty regarding black holes is that even though they are more practical than wormholes, they are dangerous and can only travel for a short time frame.
Traveling with a time machine
A lot of time travel enthusiasts understand that in order to travel forward or backward in time, a device has to be used. This device is called a time machine; and TARDIS, Doctor Who’s time machine, has given us some idea of what to look for in a time machine.
Time machines work by bending space-time into itself that time forms a loop, turning back on itself in what is known as a closed time-like curve. With the right calculations, you can travel to a date in the past and arrive at the same location you originally set out from. But time machine operates on an exotic form of energy called negative energy density which is theoretically produced in quantities insufficient to construct and power a time machine. But scientists are working on an alternative power source, a non-exotic matter that requires a strong gravitational pull to work.
5.The Grandfather Paradox
But even if time travel was actually possible, or we got to a point in technological development when all these obstacles can be surmounted, we will still encounter one unique challenge that makes the whole idea of time travel moot. This is called the Grandfather Paradox.
The Grandfather Paradox is the notion that time travel can disrupt the balance of things so that the future is changed and what should happen can no longer happen. A typical example is when a traveler goes back in time and accidently kills his grandfather. This means that he will never be born or that the trajectory of his life will be altered permanently. In the event that the Grandfather Paradox results in the traveler not being born, it means he will not have set out on the time travel in the first place.
In fact, there are a myriad of things that can go wrong in the event of a possible time travel. But the truth remains that as it stands today, time travel is far from reality.