No one has yet been able to travel through time, at least as far as we know, but the question of whether this feat would be theoretically possible still fascinates scientists.
Like movies like The Terminator, Donnie Darko, Return to the future and many others prove it, moving in time creates many problems for the fundamental rules of the Universe: if you go back in time and prevent your parents from meeting, for example, how can you exist to go back in time in first place?
It’s a monumental scratcher known as the “grandfather paradox,” but in September last year a physics student Germain Tobar of the University of Queensland in Australia said he had worked as a “square. numbers “to make time travel viable without paradoxes.
“Classical dynamics says that if you know the state of a system at a particular time, that can tell us the whole history of the system,” Tobar said in September 2020.
“However, Einstein’s theory of general relativity predicts the existence of time loops or time travel – where an event can be both in the past and in the future itself – theoretically turning the study of the dynamics “.
What the calculations show is that space-time can potentially adapt to avoid paradoxes.
To use a topical example, imagine a time traveler traveling to the past to prevent the disease from spreading; if the mission were successful, the time traveler would have no disease to go back in time to defeat it.
Tobar’s work suggests that the disease would still escape in some other way, by a different pathway or by a different method, eliminating the paradox. Whatever the time traveler did, the disease would not stop.
Tobar’s work is not easy to dig for non-mathematicians, but he analyzes the influence of deterministic processes (without any randomness) on an arbitrary number of regions of the continuous space-time and demonstrates how the two time curves closed (as predicted by Einstein) can fit with the rules of free will and classical physics.
“Mathematics is checked, and the results are science fiction stuff,” said physicist Fabio Costa of the University of Queensland, who oversaw the research.
Fabio Costa (left) and Germain Tobar (right). (Ho Vu)
The new research solves the problem with another hypothesis, that time travel is possible, but that time travelers would be restricted in what they did, to prevent them from creating a paradox. In this model, time travelers have the freedom to do whatever they want, but paradoxes are not possible.
While the numbers might work, the inflection of space and time to get into the past remains elusive: the time machines scientists have devised so far are so high that they currently only exist as calculations on a page.
We could get there someday (Stephen Hawking thought it was possible) and if we do, this new research suggests that we would be free to do whatever we wanted in the world in the past: it would be readjusted accordingly.
“Try how you can create a paradox, events will always adjust to avoid inconsistencies,” Costa says. “The range of mathematical processes we discovered demonstrates that time travel with free will is logically possible in our universe without any paradox.”
The research has been published in Classical and quantum gravity.
A version of this article was first published in September 2020.