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What if we could send a time traveler to avoid the Covid-19 pandemic?
‘(It might interest you: in the end, it will be better to sell the station to commercial operators’)
The dream of time travel always ends in a nightmare full of paradoxes. We know them through science fiction series and movies. However, physicists do not give up on proposing solutions, at least in the field of mathematics.
Professor Barak Shoshany, of Brock University, and his student Jacob Hauser, of the Perimeter Institute in Canada, recently proposed a simple model that solves the most feared incongruities for time travelers: the cycle of causality, or Bootstrap paradox, and the grandfather paradox.
What are these paradoxes? Let’s illustrate with an example
In the popular Netflix series Dark, season 2, old Claudia Tiedemann meets Noah in a forest. He is determined to kill her. Claudia looks him in the eye and says: “Do you have a choice?” Noah hesitates for a second and shoots him.
(See also: The story of ‘albi’, the first animal with a ballistic tongue)
Claudia knew she was going to die that way that day. How? The information is printed in a newspaper clipping he gave the young Agnes hours earlier, knowing that Agnes would reveal to Noah the place and time of her death.
But where does this newspaper clipping come from? Adam gives it to an elderly Agnes on a mission to hand it over to a young Claudia, who holds the role until “the time comes” to execute her own death at Noah’s hand.
This is a cycle of causality. In this type of paradox, objects and information appear out of nowhere. In the series, information about the circumstances of Claudia’s death is never created, it remains in the tragic cycle.
A similar inconsistency arises when the time traveler goes back in time to kill his grandfather before meeting his grandmother, preventing him from existing. Ah, but the traveler must be born to enter the time machine.
(Plus: 50,000 coins scanned to reveal the origin of money)
Why are physicists interested in solving the time travel paradoxes?
After more than a century, General Relativity is still the best theory of gravity we have. The recent discovery of gravitational waves only reaffirms their validity. However, the fact that time travel is a solution to his equations is a flaw in his success.
In 1983, the Russian physicist Igor D. Novikov proposed that time travel, instead of violating the laws of nature, the laws of nature required the disappearance of inconsistencies. This means that if you travel back in time to kill your grandfather, the universe conspires to ruin your plans by forcing your fate.
The downside to a single, self-consistent story is that it limits the traveler’s reach, eliminating free will.
The authors of this new study ensure that the time traveler – whose mission is to change the past – enters the time machine in one story and exits in another.
The model is an extension of Novikov’s principle to more stories or timelines in which the traveler has more capacity to act. No, it is not science fiction; it is theoretical physics. Professor Shoshany is enthusiastic about his work:
“I’ve always been fascinated by time travel; I wanted to know if they are just science fiction or if they could be backed up by real science. Some of my colleagues thought it was a bad idea and told me I would never publish an article; and in fact I have published two. So my colleagues were wrong, apparently. “
Hauser and Shoshany propose two cases. In the first, they allow the appearance of an infinite number of stories. In this scenario, the traveler enters the time machine in one story and exits in another, never visiting a previous one. This eliminates the cycles and, consequently, both paradoxes.
In the second case, scientists have discovered a way to limit the number of stories, allowing the time traveler to go back to a previous one, including the first. In this scenario, each story begins and ends in a time machine. Here the grandfather can survive at least one cycle; while the traveler is born to kill him in another story.
(In other news: Two meteor showers will grace the skies of November)
Professor Shoshany is thrilled with his model:
“I was a little surprised when we discovered that it is possible to go back to the first story, but then I realized that I should have expected it, because it’s just the usual Novikov conjecture extended to multiple stories. I would say that this is the most important discovery we have made: how much extension is possible “.
Although this proposal is a direct idealization, the authors are optimistic about the future of their research:
“We have shown that multiple stories solve the time travel paradoxes and that this can happen whether there are a finite or infinite number of them,” he says.
And he continues: “However, the question that still remains is what exactly would be the actual physical mechanism for creating new stories in time travel? I think this is the most important thing we should look at next, and if we can answer this question it would be a very interesting discovery “.
Houser and Shoshany’s time travel exists only in the realm of mathematical development, not to mention that we don’t have a time machine (yet).
However, let us dream for a moment that we can use his theory. So some of us may travel back in time, but to another story, perhaps the one where the covid-19 pandemic never happened.
Alexandra De Castro
For the moment
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