Time travel without paradoxes could make twisting history possible

Who doesn’t wish they could be like Doctor Strange in Infinity War, plunging into alternate timelines and seeing 14 million possible outcomes for the battle against Thanos? Too bad he ended up handing the Time Stone over to the purple tyrant. We all know how that went.

The closest we can get to the Time Stone (for now) is theoretical physics. Even in theory, there are paradoxes that complicate the concept of time travel and make changing the past to affect the future almost impossible. To enter the realm of possibility, you’re going to have to take the infinity out of Infinity War. That is the thinking of Barak Shoshany and Jacob Hauser of the Perimeter Institute in Canada, who are now starting to change what we think of time travel with a model that swerves away from paradoxes by using a huge — but not infinite — amount of parallel universes.

Paradoxes are the “but wait” moments that would happen if we were actually able to travel through time. Take the grandfather paradox. If you were curious to find out what would have happened if you’d never been born, you could go back in time and murder at least one of your grandparents. But wait. If you never existed, how did you catapult yourself backwards through time to begin with? And if there was no such person as you, who killed your grandparents? On and on it goes.

“The parallel universes approach that we suggest says there are different parallel universes where things are roughly the same, and each one is mathematically on a separate space-time manifold. You can go between those manifolds when you travel back in time,” said Shoshany.

This means that on one possible timeline, you could eliminate your grandparents so you don’t exist, but you will still exist on many other parallel universes. Shoshany and Hauser, who recently published a mind-blowing study, believe that there is a mathematically possible way to get through a wormhole if you view the universe as “a mathematical function ordering these points.”

Wormholes are holes in spacetime. Most parallel universe theories keep adding to these points to generate standalone universes. Whatever happens in one of these universes won’t affect the events in another one, but for the scientists, that isn’t enough. Enter parallel histories.

“What time travel means here is stepping between those histories — that’s even freakier,” Lewis said.

If other theories that include multiple universes say each universe is its own unique set of points, imagine that multiple timelines exist within just one universe, or one set of points. A unique mathematical function represents each of these timelines. You can alter that function and rearrange the points in a particular timeline if you create a wormhole and crawl through it. You can then traverse time by going from one timeline to another, so if you want a universe in which you don’t exist, you can try a different method of snuffing out your grandparents in each one. There are multiple plan B's if plan A fails.

Before you wonder what would happen if you dropped a piano on Grandpa’s head, this model can only work in a one-dimensional universe. It couldn’t exactly work out in the three-dimensional universe we live in. So if you really wanted to erase your existence for good, maybe you'd succeed in one universe, but would still be walking around in another one. You’d have to go through a finite but immense number of universes to really cancel yourself out.

Brace yourself for the Doctor Strange fan theories that could come out of this.

(via New Scientist)