**Time travel with free will is logically possible in our Universe without any paradox, according to new research from the University of Queensland.**

“Classical dynamics says if you know the state of a system at a particular time, this can tell us the entire history of the system,” said Germain Tobar, a student in the School of Mathematics and Physics at the University of Queensland.

“This has a wide range of applications, from allowing us to send rockets to other planets and modeling how fluids flow.”

“For example, if I know the current position and velocity of an object falling under the force of gravity, I can calculate where it will be at any time.”

“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 future of itself — theoretically turning the study of dynamics on its head.”

A unified theory that could reconcile both traditional dynamics and Einstein’s theory of relativity is the holy grail of physics.

“But the current science says both theories cannot both be true,” Tobar said.

“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.”

“I wondered: Is time travel mathematically possible?”

Tobar and his colleague, Dr. Fabio Costa from the Centre for Engineered Quantum Systems in the School of Mathematics and Physics at the University of Queensland, found a way to ‘square the numbers’ and their calculations could have fascinating consequences for science.

“The maths checks out — and the results are the stuff of science fiction,” Dr. Costa said.

“Say you traveled in time, in an attempt to stop COVID-19’s patient zero from being exposed to the virus.”

“However, if you stopped that individual from becoming infected — that would eliminate the motivation for you to go back and stop the pandemic in the first place.”

“This is a paradox — an inconsistency that often leads people to think that time travel cannot occur in our Universe.”

“Some physicists say it is possible, but logically it’s hard to accept because that would affect our freedom to make any arbitrary action.”

“It would mean you can time travel, but you cannot do anything that would cause a paradox to occur.”

The team’s work shows that neither of these conditions has to be the case, and it is possible for events to adjust themselves to be logically consistent with any action that the time traveler makes.

The study was published in the journal *Classical and Quantum Gravity*.

_____

Germain Tobar & Fabio Costa. 2020. Reversible dynamics with closed time-like curves and freedom of choice. *Class. Quantum Grav* 37: 205011; doi: 10.1088/1361-6382/aba4bc

*This article is based on text provided by the University of Queensland.*