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“The past is stubborn,” Stephen King wrote in his book about a man who goes back in time to prevent Kennedy’s assassination. “He doesn’t want to be changed.”
It turns out that King may have discovered something.
Countless science fiction stories have explored the paradox of what would happen if you did something in the past that endangers the future. Perhaps one of the most famous examples of pop culture is Back to the Future, when Marty McFly went back in time and accidentally prevented his parents from meeting, jeopardizing his very existence.
But maybe the McFlies weren’t in grave danger after all. According to a new paper by researchers from the University of Queensland, even if time travel were possible, the paradox could not actually exist.
The researchers analyzed the numbers and determined that even if you made a change in the past, the timeline would essentially self-correct, ensuring that whatever happened to set you back in time would still happen.
“Let’s assume you traveled through time in an attempt to prevent COVID-19 patient zero from being exposed to the virus,” Fabio Costa told University of Queensland News Service.
“However, if you prevented that individual from getting infected, it would eliminate the motivation for you to go back and stop the pandemic in the first place,” said Costa, who is co-author of the paper with honors, college student Germain Tobar.
“This is a paradox: an incongruity that often leads people to think that time travel cannot happen in our universe.”
One variation is known as the “grandfather paradox,” in which a time traveler kills his or her grandfather, thus preventing the time traveler from being born.
The logical paradox gave researchers a headache, in part because according to Einstein’s theory of general relativity, “closed time-like curves” are possible, which theoretically allow an observer to travel back in time and interact with their own. past oneself – and potentially endanger one’s own existence.
But these researchers say that such a paradox would not necessarily exist, because events would adapt on their own.
Let’s take the example of coronavirus patient zero. “You could try to prevent patient zero from getting infected, but doing so would catch the virus and become patient zero, or someone else would,” Tobar told the university news service.
In other words, a time traveler could make changes, but the original result would still find a way to happen. Maybe not the same way it happened in the first timeline; but close enough that the time traveler still existed and would still be motivated to go back in time.
“No matter what you did, the salient events will recalibrate around you,” Tobar said.
The paper, “Reversible dynamics with closed time curves and freedom of choice”, was published last week in the peer-reviewed journal. Classical and quantum gravity. The findings appear consistent with another time travel study published this summer in the peer-reviewed journal Physical Review Letters. The study found that changes made in the past will not drastically alter the future.
Best-selling science fiction author Blake Crouch, who has written extensively on time travel, said the new study appears to support what certain time travel tropes have postulated from the start.
“The universe is deterministic and attempts to alter the past Event X are bound to be the forces that bring the past Event X into being,” Crouch told NPR in an email. “So the future can affect the past. Or maybe time is just an illusion. But I guess it’s nice that the math occurs.”