- Time travel is possible based on the laws of physics, according to a new calculation by researchers at the University of Queensland.
- But time-travelers won’t be able to change the past in a way that can be measured, they say – the future will be the same.
- Visit Business Insider’s homepage for more stories.
Imagine that before you jump from a new coronavirus animal to a human, you can press the time machine, the button, and travel to 2019.
What if you could find and isolate the patient zero? Theoretically, there would be no epidemic, right?
Not quite, because then in the future તમારે you wouldn’t have set a time to travel in the first place.
For decades, physicists have been studying and discussing versions of this paradox: if we could travel in time and change the past, what would happen to the future?
The new study gives the possible answer: nothing.
“Events rearrange anything that can cause conflict, so there is no contradiction,” German Tober, author of the study and a student at the University of Queensland, told IFL Science.
His work, published last week in the Journal of Classical and Quantum Gravity, suggests that according to the laws of theoretical physics, anything you try to change in the past will be corrected by subsequent events.
Simply put: going back in time is theoretically possible, but you couldn’t change history.
People in Beijing pay tribute to China’s coronavirus victims during a national moment of silence on April 4, 2020.
Thomas Peter / Reuters
Grandpa contradicts
Since Einstein came up with his theory of relativity, physicists have considered time travel to be theoretically possible. Einstein’s calculations suggest that it is possible for an object in our universe to travel in space and time in the direction of rotation, eventually to a stage of its journey where it was before time – a path known as the end-time curve.
Still, physicists continue to struggle with scenarios like the coronavirus example above, in which time-travelers change events that have already occurred. The most famous example is known as the grandfather paradox: say that a time travel goes back to the past and kills a smaller version of his or her grandfather. Then the grandfather would not have any children, he would kill the parents of the time traveler and, of course, the time traveler. But then who will kill grandfather?
Given this paradox, the movie “Back to the Future” appears, while Marty McFly almost stops meeting his parents in the past – he probably disappears.
A dog dressed as “Back to the Future” Marty MF Cuffly participates in the annual Tampkins Square Halloween Dog Parade on October 24, 2015 in New York City.
Timothy a. Cleary / Getty Images
To address the contradiction, Tober and his supervisor, Dr. Fabio Costa used the “billiard-ball model”, imagining cause and effect as a series of closed billiard balls, and a circular pool table as a curve like closed time.
Imagine a set of surrounding billiard balls in that circular table. If you push a ball from position X, it bangs around the table, hitting others in a specific pattern.
The researchers calculated that even if you messed with the pattern of the ball at some point in its journey, future interactions with other balls could improve its path, returning you to the same position and speed you would not have interfered with.
UC Berkeley theoretical physicist Dr. “Regardless of the choice, the ball will come in the same place,” Yasunori Nomura told Business Insider.
Tober’s calculations, observed by Fabio Costa (left) with Germa Tobar (right), suggest that time travel is possible without contradiction.
University of Queensland
Tobar’s model, in other words, says you could travel back in time, but you couldn’t change how events could evolve significantly to change in the future. Applying Grandpa’s paradox, then, would mean that there is always something in the way of your attempt to kill your grandfather. Or at least until she died, your grandmother would already be pregnant with your mother.
Back to the coronavirus example. Let’s just say you had to go back to 2019 and intervene in the life of patient zero. According to Tober, the epidemic will still happen somehow.
“You can prevent a patient from being infected with Zero, but by doing so you will catch the virus and the patient will become Zero, or someone else will,” Tober told the University of Queensland.
Nomura said that although the model is too simple to represent the full range of cause and effect in our universe, it is a good starting point for future physicists.
