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The Paradoxes of Time Travel

Time travel is a concept that has fascinated people for centuries. Movies and books about traveling to the distant past or future have sparked the imaginations of people across the world. Right now, time travel is nothing but a theory. We don’t know enough about the properties of time to even guarantee that it’s possible. But that hasn’t stopped theorists from coming up with complex scenarios to test the limits of our knowledge on this topic. 

One of the best ways to improve a theory is to find the flaws or small loopholes that don’t completely add up. In the case of time travel, this can be seen in form of paradoxes. These situations often create mind bending and often endless loops, or even render the situation to be impossible in the first place. Today, we’re going to take a look at some of these paradoxes. 

But before we dive in, let’s clear something up. The ideas of “past”, “present”, and “future” are relative when we’re dealing with time travel. The “present” is viewed as the current time that you are in. The “past” is the time that came before where you are and the “future” is after. Now, if we travel to the “past” then that becomes our present since that’s the time that we are in at the moment. That means that the time you are in while reading this will be considered as the future. This concept is extremely hard to wrap your head around, but understanding it will make dealing with time travel just a little bit easier. 

The Grandfather’s Paradox:

The grandfather paradox is one of the famous paradoxes about time travel. 

Suppose you figured out a way to travel back in time. When you do, what happens if you kill your grandfather? Well, that means that since your mother was never born, then you were never born. But if you were never born, how did you go back in time to kill him? This creates an impossible situation where you complete an action, but by completing that action, you destroy your existence, thereby making it impossible for you to be able to complete the action in the first place. 

This theory, however, assumes that time is linear and that one impact in the past (from the viewpoint of our present) has a direct impact on the current events. But what if that’s not the case? What if every event creates a new timeline with a new set of events depending on the action that’s done? In that case, perhaps we can consider time travel as the jumping of these time streams. This means that killing your grandfather would simply create a new timeline where you don’t exist, but as long as you’re able to return to your original timeline, you’ll still exist. 

There’s still no set of rules as to how time must behave, so at this point it’s all speculation. 

The Butterfly Effect:

This is a concept that occurs separate to time travel, but it’s still an important idea to apply.

The butterfly effect is simply the idea that any small action can lead to larger and larger actions. An easy way to think of this is with dominos. It all starts with pushing one domino over, a seemingly harmless action. But each domino causes another one to fall and within a minute, hundreds have fallen. All that was triggered by the simple action of pushing a single domino over. That’s the butterfly effect. 

Now, let’s think about that in terms of time travel. Because, there’s no way to now what action, event, thing, or person is important or a catalyst, even one small change in the “past” can lead to a completely unrecognizable “present”. Let’s say you traveled back in time an accidentally stepped on a flower. Seems harmless right? But perhaps you just triggered a chain reaction of events, each in turn triggering a larger and larger consequence until by the time the chain reaction reaches the time you came from, the world is completely different. 

As long as there’s no way to tell the exact impact of any action, there’s no way to safely guarantee that the world you’ll return to will be the exact same as the way you left it. 

Bootstrap Paradox:

This paradox causes an infinite loop in time – similar to the chicken and egg question. 

What would happen if you traveled back in time and told Einstein the theories of relativity? After telling him, you return back to your time, but Einstein publishes the work as his own. After some years, his work comes into your hands, so you go back in time to tell Einstein how to formulate them. But who created the actual theory? You claim it came from Einstein, but he claimed that he learned it from you! 

This creates a loop where the original creator of the theory is left unknown. 

Billiard Ball Paradox:

To understand this theory, you need to first understand wormholes. A wormhole is a theoretical bending of the fabric of space-time so that two points (perhaps on either side of the galaxy) as right next to each other. The wormhole then simply bridges the gap, allowing the travel of millions of lightyears in an instant. 

Imagine a billiard ball was tossed through a wormhole. If the wormhole has a type of closed system where it’s possible to return to the entrance that was first used, then there’s a possibility that the billiard ball will hit its “younger” self first entering, thus throwing it off course. This means that the ball never entered in the first place, but then how could it stop itself?

The majority of these theories have many proposed solutions. It’s important to note that at this point these are nothing but speculation, since we don’t fully understand the rules behind how time behaves. Is it linear? Is there a multiverse? Is it branched? Is it in a form that we simply can’t comprehend yet? Hopefully, one day we’ll understand.