The Dangers of Travelling through Time

By Rhys L Griffiths

Doctor Who's TARDIS travelling through time. - ©BBC

Doctor Who’s TARDIS travelling through time. – ©BBC

The idea of time travel is awesome! To have the ability to be part of the wild west or witness the pyramids be built, to watch The Beatles perform in concert or to have an extra hour in bed in the morning. What ever you chose to do I think we can all agree that time travel is pretty great. Or is it? Travelling in time can be quite dangerous as it’s possible you could encounter a paradox.

What is a Paradox?

A paradox is something that cannot be true, but also at the same time cannot be false. An example of this would be the following sentence:

“This sentence is a lie”

If this sentence is true then it’s a lie. But if it’s a lie then how can it be true? It contradicts itself.  This is known as the Liar’s Paradox.  Another variation on this is the Pinocchio Paradox.  I think it’s safe to say that everyone knows that if Pinocchio tells a lie, his nose grows. So what happens if Pinocchio says:

“My nose will now grow”

He is lying when he makes the statement so his nose would grow. But if his nose grows then that makes the statement true, so his nose wouldn’t grow. But that would mean he was lying when he said it which would make his nose grow. But if his nose grows then he isn’t lying so why does it grow? Basically a paradox is a sentence or event that makes your head ache with confusion.

There are many paradoxes out there, especially when it comes to time travel. So before you go journeying into unknown times you should be aware of the problems that could arise. Because if not, you could tear the fabric of space time in half and as we’ve all learnt from those time travel movies, that’s a bad thing. So here are some paradoxes you should be aware of when you’re on your time travelling adventures.

Predestination Paradox

A Predestination Paradox exists when a person travels back in time to prevent a certain event from happening, but in doing so becomes the cause of the event. This is also referred to as a causality loop as the time traveller is caught in a loop of events that predestines or predates them to travel back through time.

The Terminator (1984) promotional poster.

The Terminator (1984) promotional poster.

An example of this would be in the film ‘The Terminator’ (1984). The film starts in a post apocalyptic future where the machine intelligence, Skynet, is busy protecting humanity from itself by eradicating it. However there are a group of humans, led by John Connor, fighting back and doing a pretty good job. So Skynet decides to send a Terminator (a killing robot with artificial intelligence) back in time to kill John Connor’s mother (Sarah Connor) before he is even born. John learns of this and sends a solider, Kyle Reese, back in time to protect his mother. While he protects her from the Terminator, Kyle and Sarah fall in love and Kyle ends up becoming John Connor’s father. So Skynet wants to rid the world of John Connor, sends a robot back in time to stop him from being born, which then forces Kyle Reese to go back in time to protects John’s mum, and ends up fathering John himself. If The Terminator hadn’t been sent back in time, then there would be no need to send Kyle Reese back and therefore John Connor wouldn’t have been born. Skynet tried to stop an event from happening but accidentally became the cause of it.

Does this mean that both the past, present and future are predetermined and there is nothing you can do to change what has already been done? If you do try to change the past you fulfil your role in an already scripted series of events.

Grandfather Paradox

A lot of people travelling in time may want to visit their relatives. But what would happen if you accidentally crashed your time machine on a teenage version of your Grandfather? How would you be able to exist? But then how would you be able to travel back in time, killing him in the first place. This is the Grandfather Paradox. A paradox that shows that if you interfere with your family tree it may result in you not being born. But then you wouldn’t be around to interfere with your family tree meaning that there’s nothing stopping you from existing.

Still image from 'Back to the Future' (1985) ©Universal Studios

Still image from ‘Back to the Future’ (1985) ©Universal Studios

The film Back to the Future deals with this paradox quite well. Marty’s parents meet because his grandfather hits Marty’s dad with his car and brings him inside his house to make sure he’s ok. Marty’s dad then meets Marty’s mum when she looks after him and they fall in love. But when Marty goes back in time, instinct kicks in and he pushes his father out of the way of the moving car. Time starts to correct itself and we watch as a photograph of Marty and his siblings starts fading away.  Marty has to get his parents to meet and fall in love otherwise he’ll never be born. But then if Marty isn’t born then he won’t be there to push his father out of the way of the moving car, meaning that his parents would meet and fall in love like they are supposed to.

The Back to the Future films do not deal with time in a predestined way. When Marty does go back to the future, it’s a new future that he isn’t aware of. His father is successful and more confident and his mother is a lot happier. All this is because of Marty’s influence on them as teenagers. There are other moments in the franchise which sees characters travel from the future to the past, altering time lines and creating parallel universes.

Hitler’s Murder Paradox

This paradox is a variant of the Grandfather Paradox. If someone wanted to go back in time and murder Hitler before World War 2 started, they could think that by doing so they could save a lot of lives by preventing the war. But if Hitler died before he became known, then you wouldn’t know who he was and therefore have no reason to travel through time to murder him.

Bootstrap Paradox

A Bootstrap Paradox is when an object, a piece of information or even a person is sent back in time and has no discernible origin. An example would be if a young musician was sitting alone in their room, trying to write their first number one hit, when suddenly an older version of them appears from the future and teaches the younger musician a song that made them famous. When the musician became older they would then have to travel back in time and teach their younger self the song, meaning that the song would have no original creator. Who wrote the song?


This type of Paradox appears in many science fiction mediums such as Marty McFly inventing the song ‘Johnny B Goode’ in Back to the future, Matthew McConaughey haunting himself in Interstellar or even Dave Lister becoming him own dad in Red Dwarf.

When travelling through time, do be careful

Time travelling can be very dangerous. One wrong step and you can change the course of history wiping out not just yourself, but potentially all of humanity. You could tear a hole in the fabric of time and space and destroy everything! So if you do want to travel in time then maybe its best to stay in and watch Doctor Who on the telly instead.
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Posted in Physics