n June 28th, 2009, Stephen Hawking threw a party near the University of Cambridge, but no one was in attendance. The party was for time travelers from all over the world. The catch was simple — Hawkins only sent out the invitations after the party date had passed. That way, the only people who could have been in attendance are people capable of time travel.
Sadly, no one showed up at the party — at least not to our knowledge — but Hawkins didn’t lose hope. According to him, the invitation would last for thousands of years and encourage time travelers to attempt to manipulate time.
But several schools of thought insist that time travel is impossible. Different exponential problems arise immediately when you consider what entails going back in time.
A Time Traveler’s Paradox
There are multiple convincing philosophical problems with traveling back in the past. Let’s assume you get access to a fully functional time machine and can travel back in time. This is groundbreaking, but how does it affect our present-day reality or the world as we know it? Here are the three paradoxes that can arise from using a time machine.
The Hitler Paradox
Assuming you decided to go back in time to the early 1890s and find baby Adolf Hilter to kill him before he can start the Second World War and the Holocaust. While this might sound like a noble cause, your actions would have created an enormous problem.
At the moment you kill Hilter, you stop all the horrible things he had done in the future. And although that’s inspiring, it is also problematic. Killing Hitler would remove any reason for you to have traveled back in time in the first place. There would be no knowledge of Hitler existing in the future — since it only existed based on his actions — and therefore, no need for you to have taken it upon yourself to kill him.
Besides, the consequences of Hitler’s actions are so monumental in our time that most of life as we know it today and the births of every human alive was influenced by it. So if you were to go back in time to erase Hitler, the chain of events that led to your birth probably wouldn’t have occurred. So you won’t have existed and therefore be incapable of traveling back in time.
The Grandfather Paradox
Another way to visualize this same problem is to consider the Grandfather Paradox. Instead of going to erase Hitler, let’s imagine you went back in time to meet your grandfather instead. You met him before he had met your grandmother and you killed him.
Then, it would have been impossible for you to be born since you already killed your grandfather in the past. This means your grandfather would still be alive, meaning you would still be alive and able to go back in time to kill him.
This loop could go on forever, and that’s the paradox.
The Bootstrap Paradox
Consider this final paradox — going back in time with all of the works Shakespeare ever produced. You meet with Shakespeare before he produces the works and give him the ones from the future. Shakespeare goes on to produce all of these works based on the knowledge you gave him.
The problem becomes — where did the works originate from? It wasn’t Shakespeare since he copied what you gave him, and it wasn’t you either since you only brought future Shakespeare’s work back through time. This would mean that the works have no origin point, which is impossible and doesn’t make sense.
The Novikov Self-Consistency Principle
If the technology to take you back in time ever existed, the Novikov Self-consistency principle might be a solution to the paradoxical problems. The law states that the probability of any event that will create a paradox or alter the past in any way is zero. Simply, if you went back in time, it would be theoretically impossible for you to alter any events of the past — either by killing a person or providing them with information from the future.
While this might sound intriguing at first, further analysis shows that it interferes with the concept of human free will. If a time traveler is physically incapable of carrying out an act, then the concept of free will is null.
Here’s another possibility — a time traveler might be able to go back in time and observe events as they occur. However, such a traveler will be unable to make any changes to the events that have already happened. As long as a physical law stops the traveler from carrying out specific actions, such a traveler’s actions are already predetermined.
The Alternate Universe Theory
Yet another solution that scientists seem to toy with is the alternate universe theory. It is possible to alter the past only if you are doing so in an alternate universe. Therefore, you can go back in time to kill your grandfather, but only in an alternate universe where you weren’t born in. That way, you can’t affect your future.
Still, several people don’t subscribe to this since it would not be time travel exactly — you are not in your universe, only an alternate one.
Conclusively, if technology ever advanced enough to allow for time travel, we probably still couldn’t — or shouldn’t — engage with it because of how badly we can ruin things.
Nevertheless, if you ever want to attend that party with Stephen Hawkins, here are the coordinates: 52° 12’ N, 0° 7’ 4.7” E.
We hope you will be the first one to show up in the pictures.