Scientists in Australia claim to have proved that time travel is theoretically possible after solving a logical paradox.

Physicists from the University of Queensland used mathematical modelling to reconcile Einstein’s theory of general relativity with classical dynamics. The clash between these two systems is behind a famous flaw with time travel, known as the grandfather paradox.

Einstein’s theory allows for the possibility of a person using a time loop to travel back in time in order to kill their grandfather. However, classical dynamics dictates that the sequence of events following the grandfather’s death would culminate in the time traveller not existing in the first place.

“As physicists, we want to understand the universe’s most basic, underlying laws and for years I’ve puzzled on how the science of dynamics can square with Einstein’s predictions,” said Germain Tobar, who led the research. “Is time travel mathematically possible?”

For their calculations, Mr Tobar and Dr Costa used the coronavirus pandemic as a model for working out whether the two theories could co-exist.They imagined a time traveller attempting to go back and prevent patient zero from being infected with Covid-19.

Einstein’s theory allows for the possibility of time travel but the science of dynamics would mean that the fundamental sequence of events could not be interfered with.

This is because if the time traveller succeeded in preventing the virus from spreading, then it would eliminate their initial motivation for them to travel back in time.“In the coronavirus patient zero example, you might try and stop patient zero from becoming infected, but in doing so you would catch the virus and become patient zero, or someone else would,” Mr Tobar said.

"No matter what you did, the salient events would just recalibrate around you. This would mean that - no matter your actions - the pandemic would occur, giving your younger self the motivation to go back and stop it. Try as you might to create a paradox, the events will always adjust themselves to avoid any inconsistency.“The range of mathematical processes we discovered show that time travel with free will is logically possible in our universe without any paradox.”

University of Queensland physicist Dr Fabio Costa, who supervised the research, added: “The maths checks out - and the results are the stuff of science fiction."

A paper detailing the research was published in the journal *Classical and Quantum Gravity*.

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