The 3 Schools of Time Travel Theories, Part 0: Paradoxes

Estimated reading time: 5 minutes

I’ve been meaning to do this post for quite some time now and then I’d forget all about it. Not today.

So buckle up and brace yourselves, because we’re about to look at the 3 most prevalent time travel theories out there and we’ll be discussing the sort of time travel paradoxes that arise from each theory…


Today, we need a post to lay the groundwork for time travel paradoxes. Time travel is easy to think about, but once you start getting into the nitty gritty of paradoxes, it quickly becomes a big ball of wibbly-wobbly, timey-wimey… stuff.

Get it?


So we need to talk about paradoxes to properly examine time travel theories and their paradoxes. Here goes.


A paradox is a concept that challenges our understanding of something, causes us to ask questions, and exposes how flawed our understanding of that something really is. Some paradoxes essentially become a contradiction of themselves, not because the paradoxes themselves are particularly clever, but because the framework in which they exist is flawed.

It’s easier to see with an example. One of my favorite paradoxes deals with how we look at the self, our own bodies and consciousness. It is then applied to teleportation concepts to bring up some very deep philosophical dilemmas with the technology. It’s the Ship of Theseus paradox, and here’s how it goes. (Or at least, the modern version of it.)


Consider two cars: car A and car B. I take a part out of car B and install it into car A. Is car A still car A? Most would say “Yes”. But if I take another part, and another part, again and again, at which point does car A stop being car A and become something else?

An even simpler version… take an old hammer, and replace the head. Is it still the same hammer? Again, most would say “It’s the same hammer, just with a new head.” But then, what happens if I replace the handle? Is it still the same hammer now?

Now, most people would agree: this is not the same hammer, but that’s where it all crumbles, because this paradox can be used to challenge the way we look at the concept of the self. Our body does the same thing. It’s continuously replacing parts in car A. First the head, then the handle. Our cells are always dying and being replaced, so frequently that in a couple of years, every cell in your body has been replaced. So are we still occupying the same body? If you said it’s not the same hammer, then are you not the same person anymore?

And if you answered “But I’m the same person because it’s my consciousness that’s the same.” If your body has been completely replaced, where exactly does your consciousness reside? Where’s it gone?

Many would then say, “Well, we are the product of our past experiences. Our memories make us who we are.” Well, even looking past the issues this causes with memory loss (if we are our memories, are people with complete memory loss not the same people, then?), we can also apply the paradox to teleportation.

You take person A, digitize a copy, destroy every cell in their body, then rebuild it from the digital copy to make person B. Keeping in mind your answers to the previous paradox examples, is person B the same as person A?

These questions are half-rhetorical because there isn’t only one answer. Different people will give different answers and no one person can say they have the right answer, because there simply isn’t one. That’s the reason paradoxes exist. They challenge our understanding of the world around us, creating philosophical problems or dilemmas to expose the flaws in that understanding.

Paradoxes are essential to time travel theories because they force us to see the issues with those theories.


Paradoxes are rife in time travel because time travel is both unknown and challenges the very core of our perception of time. But that doesn’t stop people from asking questions and coming up with solutions because that’s what people do.

There are three prevalent time travel theories out there, and each theory exists to solve another theory’s paradoxes. We’ll discuss the theories at length in future posts but here’s the too long didn’t read version:

  1. In the Dynamic Timeline theory, you can change the past and affect the future. This is the most common time travel theory, especially used in movies with time travel because of the storytelling opportunities it creates. And because it’s easy to work with when you ignore the paradoxes. Paradox: what if you kill your own grandfather, what happens then? Is this even possible?
  2. In response, the Fixed Timeline theory arose, where everything the time traveler does has already happened in history. So you can’t kill your grandfather. Paradox: the causal loop, in which the time traveler gives himself information in the past.
  3. And finally, the Multiverse theory, commonly regarded as the paradox killer, in which time travel involves stepping from one universe to another universe. Paradox: there aren’t any particularly related to time travel, but the multiverse creates a whole slew of other related paradoxes.


Tomorrow we’ll start by looking at the most commonly used time travel theory: the Dynamic Timeline. It’s a complete mess of paradoxes but it’s also the one that sees the most use in popular media. It’s usually safe enough to say “Don’t think too hard about it. Sit back and relax.” when watching a movie, but if you’re seriously thinking about time travel, this theory unravels quickly and in a great flash of mind-bending inconsistencies.

I’ll see you all tomorrow. Until then, here’s a particularly relevant Austin Powers clip.

The 3 Schools of Time Travel Theories – Table of Contents

Part 0: Paradoxes << YOU ARE HERE
Part 1: Dynamic Timeline
Part 2: Fixed Timeline
Part 3: Multiverse

Amante Reale

I'm a freelance writer specializing in tech, gadgets, security, cryptography and cryptocurrency. Warning: I am armed with very strong opinions and I'm not afraid to use them. Hire me!