Time travel opens up a dimension we never really think about. Everybody loves to dream of special powers, super-fast, super-strong, flying, telekinesis, but as special powers go, time travel takes it by a country mile.
The movie, Back to the Future had Marty McFly battling for his own existence as his parents looked like they weren’t going to fall in love. Twelve Monkeys, Terminator, The Philadelphia Experiment, the Butterfly Effect, Interstellar and so many more showed how popular the genre is. They command big fee actors and big fee directors.
Time travel has been referred to in biblical and other ancient religious texts for thousands of years.
In Hindu mythology, 2,500 years ago, the Mahabharata mentions the story of King Raivata Kakudmi, who travels to heaven to meet the creator Brahma. When he returns to Earth, he learns that he has travelled several hundred years into the future.
One of the Buddha's chief disciples, Kumara Kassapa, explains to the sceptic, Payasi, that time in the Heavens passes differently than on Earth.
The Japanese tale of "Urashima Tarō", first described in the Manyoshu, tells of a young fisherman named Urashima-no-ko, who visits an undersea palace. After three days, he returns home to his village and finds himself 300 years in the future, where he has been forgotten, his house is in ruins, and his family has died.
In Jewish tradition, the 1st-century BC scholar Honi ha-M'agel is said to have fallen asleep and slept for seventy years. When waking up he returned home but found none of the people he knew, and no one believed his claims of who he was.
In literature, early science fiction stories feature characters who sleep for years and awaken in a changed society or are transported to the past through other supernatural means.
Among them is “L'An 2440, rêve s'il en fût jamais” (1770) by Louis-Sébastien Mercier, Rip Van Winkle (1819) by Washington Irving, Looking Backward (1888) by Edward Bellamy, and When the Sleeper Awakes (1899) by H.G. Wells.
Prolonged sleep is used as a means of time travel in these stories but the earliest work about backwards time travel is most probably Samuel Madden's Memoirs of the Twentieth Century (1733), which uses the idea that the author is given documents from 200 years in the future. He’s given a series of letters from British ambassadors in 1997 and 1998 conveying the political and religious conditions of the future. While no person is shown travelling back in time, the documents do.
The narrator receives these letters from someone he refers to as his “guardian angel” and Paul Alkon suggests in his book Origins of Futuristic Fiction that "the first time-traveller in English literature is a guardian angel." Madden does not explain how the angel obtains these documents, but Alkon asserts that Madden "deserves recognition as the first to toy with the rich idea of time-travel in the form of an artefact sent backwards from the future to be discovered in the present."
Many ancient tales are uncannily in sync with current theories, what we see today as the fundamental reality of space travel.
If you travel fast enough for long enough or get too close to a black hole, your time slows down but on Earth, everyone else’s time stays as it was. After a few years, you’d find yourself returning to find your granddaughter an old lady.
If your spaceship circled the Earth at a fast enough speed (many times faster than light), you might witness the Earth growing old, eventually being absorbed by our sun’s expansion in 5 billion years.
Time machines are theoretically possible if you can construct devices of infinite size using almost infinite energy travelling at almost infinite speed, but at no point could such constructions by any race be feasible.
But wherever the technology comes from, however it works, time travel is one of our favourite after-hours conversations. Once we’ve exhausted the tales of the day, exhausted the news, sports, fashion and assorted banter. It’s the time for noble and futile speculation apropos of nothing.
What would you do if you could go back in time?
We’ve been thinking about it for a very long time. Maybe ever since we could exhibit coherent thought as ancient home sapiens. When a loved one was taken by the wolves, did ancient humans, just like us today, wish they could revisit the scene and make it work out differently?
The question causes people to smile and put their heads back, delighting in the wilful descent to a dream world where anything is possible, ultimate control can be seized.
It would be a rare person without an already well-planned answer to it. Take today’s winning lottery ticket back to last Tuesday, see your parents when they were small, see a dinosaur?
If you didn’t fancy humble tourism or feathering your nest, maybe you’d right a terrible wrong, kill Hitler or Stalin or some other nasty, meet Jesus or just learn about what really happened at any given point in history.
And this is where our fanciful thoughts have to be analysed.
What are the repercussions of time travel, if indeed we could do it?
Let’s say we killed Hitler, perhaps saving millions of lives. Try and map through time and what could have happened after that moment.
Are we that sure of our genetic isolation from the events we change to ensure our own existence?
Are we sure that the bug we’ve just stepped on 50 million years ago, didn’t evolve into something important today?
Apart from the inherent dangers of doing this, it also brings up paradoxes. A paradox is why potentially we can never travel back in time.
A situation or statement that seems impossible or is difficult to understand because it contains two opposite facts or characteristics. For example, drinking a lot of water can often make you feel thirsty. (Cambridge Dictionary)
There is nothing in Einstein’s theories of relativity to rule out time travel, although the very notion of travelling to the past violates one of the most fundamental premises of physics, causality. Causality states that the effect of an action can only occur after the cause.
The classic paradox is the Grandfather Paradox. If you go back in time and kill your grandfather before even your father was born, how could you ever be born yourself and go back and kill your grandfather?
Similarly, with the “Killing Hitler” paradox.
If you go back in time and kill Hitler, it erases your own reason for going back in time to kill him in the first place.
So, because paradoxes are logical to us, and we love logic, can time travel backwards ever be possible?
Possibly.
It’s called Multiverse Theory.
Every action we take has an alternative. We might have turned left instead of right. An atom might have behaved slightly differently. Every branch on the probability tree has its own existence, seemingly independent of our own and they’re all running in parallel.
There is no time machine and we have no idea how we control access to it but it’s much tidier. There are no paradoxes in multiverse theory because each time you travel back in time, you are actually travelling to a different universe, almost identical to our own.
If you go back and kill Hitler and stay in that universe, you will see the repercussions play out.
If you return to your own time or universe, Hitler will still have existed.
Teaser – Episode 2 – How Close are we?
So, with all this in mind, how close are we to being able to travel back in time?