Estimated reading time: 4 minutes
A week ago we started this series about time travel theories and the paradoxes that arise from each, with an introduction and a “quick” look at what paradoxes are, why and how they exist. Then, on Monday, we discussed the Dynamic Timeline theory and its biggest paradox, the Grandfather Paradox. Next came the second time travel theory, the Fixed Timeline, which solves the Grandfather Paradox but causes a new paradox, the Causal Loop.
For our last post of the series today, we’re looking at the last theory, what many consider a “paradox killer”: The Multiverse.
HOW IT WORKS
The Multiverse Theory suggests that time travel into the past is possible, and you can change the past… but not really. What it does is combine both the Dynamic and Fixed timeline theories into a timetravel theory where you can change the past without breaking space and time. Here’s how:
Whenever you travel back in time, change something, and then return, you do not return to your own universe and your own timeline. Instead you find yourself in a copy of the universe in which the Fixed Timeline theory applies to your situation.
Let’s look at an example. Here we go with killing Hitler again.
You’re a guy building a time machine. Hating Hitler is basically a requirement to becoming a time traveler so as soon as you complete your machine you get in there and head into the past with a handgun and a bullet with Hitler’s name on it.
So you find Hitler, and pull the trigger. BAM! Hitler’s de–pause.
You are now in an alternate universe, a universe in which Hitler was killed by a time traveler (Fixed Timeline). Maybe this alternate universe already existed, or maybe it was created by your meddling around with history. Either way, you’re in an alternate universe.
resume–ad. Mission accomplished. But you don’t notice anything. You get back into your time machine and head to your own present. Obviously things are different (Dynamic Timeline) and as far as you’re concerned (from your own point of view) you’ve changed the past, but this is not really your universe. In your universe Hitler was never killed by a time traveler. The people you left behind still live with Hitler in their past. The only thing that happened in your universe is a time traveler got into a time machine and never came back.
Now you’re living in a universe where Hitler was killed by a time traveler, but you didn’t cause a paradox because the Fixed Timeline theory protects you from it.
HOW IT BREAKS THE PARADOX
This theory’s prerequisite is that you believe in the Multiverse, an infinite number of alternate universes that cater for all possible scenarios and choices people make every day. This is why most people are resistant to this time travel theory because it requires an additional, entirely unproven theory.
But if you can wrap your head around the possibility of infinite universes it will quickly become clear why this theory is considered the “paradox killer”.
Killing your own grandfather is no problem because it’s not your own grandfather you’re killing, but the grandfather in the timeline where he was killed by a time traveler (that looks a lot like him).
And you can‘t cause a causal loop because the past of the timeline you came from (in which the inventor actually did design the original blueprints) is not the same inventor of the past from the timeline you travel to (in which the inventor got the blueprints from you).
Because you have both Dynamic and Fixed timeline concepts rolled into one, it’s rather hard to come up with a paradox to disprove our understanding. But still, this theory is not without its own share of problems. Specifically…
…WHAT HAPPENS TO THE “OTHER” YOU?
In our Hitler story, Dude A travels into the past of Timeline A, kills Hitler which creates or transfers to Timeline B, and then goes back to the present (future?) of Timeline B, in which there is no Hitler.
But what about Dude B? What about the alternate Dude A that inhabits Timeline B? Would Dude A return to the present to find himself cohabiting Timeline B with Dude B? That would be bad, because now you’re suffering from Dynamic Timeline paradoxes.
So the logical conclusion would be that Dude A resumes Dude B’s life from the time he returns, and this is somewhat rough to wrap your head around, especially when you start examining all the ethical issues raised by the thought. Hard enough that it still isn’t the most widely accepted time travel theory.
Not too bad, was it? Three time travel theories and the paradoxes they raise, hopefully explained in a sufficient straightforward manner. I hope you enjoyed this series and that it, at least, got you thinking about the possibilities.
So what do you think? How do you think time travel would happen? Will we ever be able to achieve the dream of changing things in the past to better our present?
Let me know in the comments! And if you enjoyed the series, why not share it with your friends? :)
The 3 Schools of Time Travel Theories – Table of Contents