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No one has managed to time travel yet – at least to our knowledge – but the question of whether such a feat would be theoretically possible continues to fascinate scientists.
As films such as The Terminator, Donnie Darko, Back to the future and many others show, moving through time creates a lot of 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? time in the first place?
It’s a monumental scraper known as the ‘grandfather’s paradox’, but in September of last year, physics student Germain Tobar from the University of Queensland in Australia said that ‘he had found a way to “balance the numbers” to make time travel viable without the paradoxes.
“Classical dynamics say that if you know the state of a system at any given point in time, it can tell us the whole story of the system,” Tobar said in September 2020.
“However, Einstein’s general theory of relativity predicts the existence of time loops or time travel – where an event can be both in the past and in the future of itself – theoretically turning the study around. dynamics on his head. “
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 spread of disease – if the mission was successful, the time traveler would have no disease to travel back in time to conquer.
Tobar’s work suggests that disease escapes in yet another way, through a different route or by a different method, removing the paradox. Whatever the time traveler does, the disease would not be stopped.
Tobar’s work is not easy for non-mathematicians to delve into, but he examines the influence of deterministic processes (without any randomness) on an arbitrary number of regions in the space-time continuum, and shows how the two Closed time-type curves (as predicted by Einstein) can fit into the rules of free will and classical physics.
“The math checks – and the results are science fiction,” 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 smooths out the problem with another hypothesis, that time travel is possible but time travelers would be limited 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 numbers can work, it’s still hard to bend space and time to step into the past – the time machines scientists have designed so far are so conceptual they don’t exist today. as calculations on a page.
We might get there one day – Stephen Hawking certainly thought it was possible – and if we do, this new research suggests that we would be free to do whatever we wanted with the world in the past: it would readjust accordingly.
“Try as you can to create a paradox, events will always adjust on their own, to avoid any inconsistency,” says Costa. “The range of mathematical processes that we have discovered shows that time travel with free will is logically possible in our universe without any paradox.
The research was published in Classical and quantum gravity.
A version of this article was first published in September 2020.
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