In science fiction movies like the “Back to the Future” saga, they usually show us time travel that amazes more than one viewer. This is not a coincidence, as we have all wondered whether it is possible to do it in the future as well as in the past.
The answer to this question is covered in an article published in the scientific research and news portal The conversationby Barak Shoshany, professor of physics at Brock University (Canada).
The Canadian expert wrote about the possibility that humans need to travel in time and found a solution to the various paradoxes that physicists have discovered in the various theories of time travel.
Current Understanding of the Causality Principle
Our current understanding of time and causality is based on the general theory of relativity of the German theoretical physicist Albert Einstein (1879-1955), which has been around for more than 100 years and on which experts agree, describes the causal structures of our universe quite accurately.
This theory combines space and time into a single entity, “space-time,” and according to Shoshany offers an extraordinarily intricate explanation of how the two work, at a level unmatched by any other established theory.
According to the Canadian professor, general relativity allows physicists to write equations that describe time travel in a coherent way that is compatible with relativity. “But the equations don’t make sense if they don’t match something in reality,” Shoshany said.
In this sense, the question arises why these comparisons should be unreal?
Two big problems with time travel
First, according to the physicist, to build a time machine, scientists would have to use exotic matter with negative energy for the equations. However, negative energy is not available in every corner.
At the current state of knowledge, only quantum mechanics gives us hope, at least in theory, of being able to produce it in very small quantities and for extremely short periods of time.
Shoshany is optimistic and supports the possibility of discovering other equations that allow time travel without the need for exotic matter. “This problem may simply be a limitation of our current technology or our understanding of quantum mechanics,” he said.
Exotic matter aside, the other big problem is the observation that time travel seems to contradict logic in the form of consistency paradoxes. To explain it, the physicist gives a surprising example.
“For example, consider a scenario where I go into my time machine, use it to go back five minutes, and destroy the machine once I get into the past. Now that I’ve destroyed the time machine, I couldn’t possibly use it five minutes later,” explained Shoshany. from.
This means that if you’re in the moment you are, you can’t go back in time to destroy it, meaning the time machine hasn’t been destroyed. And you can use it to go back in time and destroy it. In other words, it’s a time machine that will self-destruct if it doesn’t self-destruct. Paradoxical, right?
“Because it cannot be destroyed and not destroyed at the same time, this hypothesis is inconsistent and paradoxical,” said the physicist, adding that unlike science fiction, where there is a misconception that paradoxes can be “created,” in physics there is no event is that can really happen. Paradoxes, he added, are thus a purely theoretical concept that points to an inconsistency in the theory itself.
Does this mean, then, that time travel is simply becoming impossible in the eyes of science? Not necessarily, according to some researchers.
The theoretical physicist Igor Dmitriyevich Novikov tried to solve the issue of time travel paradoxes with a self-consistency conjecture, which “essentially states that you can travel to the past, but you can’t change it.”
The parallel world approach
However, Professor Shoshany, along with his students Jacob Hauser and Jared Wogan, studied time travel and found in recent work that there are time travel paradoxes that Novikov’s conjecture cannot solve.
Therefore, the Canadian expert and his students proposed a different approach to solve the paradoxes: the theory of parallel timelines.
“We show that allowing multiple histories (or in more familiar terms, parallel timelines) can resolve paradoxes that Novikov’s conjecture cannot. In fact, it can solve any paradox that arises,” emphasized the physicist.
According to his theory, when a person gets out of a time machine, he ends up in another timeline, where he can do whatever he wants, including destroying his time machine five minutes before he’s supposed to use it. In this theory, changes to this new timeline would have no effect on the original timeline.
“Since I can’t destroy the time machine in the original timeline that I traveled to the past with, there’s no paradox,” Shoshany said.
“After working on time travel paradoxes for the past three years, I am increasingly convinced that time travel is possible, but only if our universe can allow multiple histories to coexist.” †
Quantum mechanics seems to be leaning towards yes
According to Shoshany, splitting it into multiple storylines is entirely possible in quantum mechanics.
“Quantum mechanics seems to imply that this is the case, at least if you subscribe to Everett’s ‘many worlds’ interpretation, in which a story can be ‘split’ into multiple stories, one for each possible measurement result, for example if Schrödinger’s cat is dead or alive, whether I have reached the past or not,” he said.
Currently, the Canadian professor is working intensively with his students to develop a specific theory of time travel in different timelines that complies with the law of general relativity.
“Of course, even if we manage to find such a theory, it wouldn’t be enough to prove that time travel is possible, but at least it would mean that time travel isn’t ruled out by consistency paradoxes,” he concluded. in her article.