From The University of Queensland (AU) Via “Science Alert (AU)” : “Young physicist ‘squares the numbers’ on time travel”


From The University of Queensland (AU)



“Science Alert (AU)”

David Nield

Mr Germain Tobar
+61 406 123 686

Dr Fabio Costa
+61 456 646 231

Dominic Jarvis
+61 413 334 924

A futuristic car from the 1980s … physicists seek to understand the Universe’s underlying laws.


No one has yet managed to travel through time – at least to our knowledge – but the question of whether or not such a feat would be theoretically possible continues to fascinate scientists.

As movies such as The Terminator, Donnie Darko, Back to the Future and many others show, moving around in time creates a lot of problems for the fundamental rules of the Universe: if you go back in time and stop your parents from meeting, for instance, how can you possibly exist in order to go back in time in the first place?

It’s a monumental head-scratcher known as the ‘grandfather paradox’, but a few years ago physics student Germain Tobar, from the University of Queensland in Australia, worked out how to “square the numbers” to make time travel viable without the paradoxes.

“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 Tobar.

“However, Albert 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.”

What the calculations show is that space-time can potentially adapt itself to avoid paradoxes.

To use a topical example, imagine a time traveler journeying into the past to stop a disease from spreading – if the mission was successful, the time traveler would have no disease to go back in time to defeat.

Tobar’s work suggested that the disease would still escape some other way, through a different route or by a different method, removing the paradox. Whatever the time traveler did, the disease wouldn’t be stopped.

Tobar’s work isn’t easy for non-mathematicians to dig into, but it looks at the influence of deterministic processes (without any randomness) on an arbitrary number of regions in the space-time continuum, and demonstrates how both closed time-like curves (as predicted by Einstein) can fit in with the rules of free will and classical physics.

“The maths checks out – and the results are the stuff of science fiction,” said physicist Fabio Costa from the University of Queensland, who supervised the research.

Fabio Costa (left) and Germain Tobar (right). (Ho Vu)

The research smoothed out the problem with another hypothesis, that time travel is possible but that time travelers would be restricted in what they did, to stop them 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 out, actually bending space and time to get into the past remains elusive – the time machines that scientists have devised so far are so high-concept that for they currently only exist as calculations on a page.

We might get there one day – Stephen Hawking certainly thought it was possible – and if we do then this new research suggests we would be free to do whatever we wanted to the world in the past: it would readjust itself accordingly.

“Try as you might to create a paradox, the events will always adjust themselves, to avoid any inconsistency,” said Costa.

“The range of mathematical processes we discovered show 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.
See the science paper for instructive material with images.

See the full article here .

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The University of Queensland (AU) is a public research university located primarily in Brisbane, the capital city of the Australian state of Queensland. Founded in 1909 by the Queensland parliament, UQ is one of the six sandstone universities, an informal designation of the oldest university in each state. The University of Queensland was ranked second nationally by the Australian Research Council in the latest research assessment and equal second in Australia based on the average of four major global university league tables. The University of Queensland is a founding member of edX, Australia’s leading Group of Eight and the international research-intensive Association of Pacific Rim Universities.

The main St Lucia campus occupies much of the riverside inner suburb of St Lucia, southwest of the Brisbane central business district. Other University of Queensland campuses and facilities are located throughout Queensland, the largest of which are the Gatton campus and the Mayne Medical School. University of Queensland’s overseas establishments include University of Queensland North America office in Washington D.C., and the University of Queensland-Ochsner Clinical School in Louisiana, United States.

The university offers associate, bachelor, master, doctoral, and higher doctorate degrees through a college, a graduate school, and six faculties. University of Queensland incorporates over one hundred research institutes and centres offering research programs, such as the Institute for Molecular Bioscience, Boeing Research and Technology Australia Centre, the Australian Institute for Bioengineering and Nanotechnology, and the University of Queensland Dow Centre for Sustainable Engineering Innovation. Recent notable research of the university include pioneering the invention of the HPV vaccine that prevents cervical cancer, developing a COVID-19 vaccine that was in human trials, and the development of high-performance superconducting MRI magnets for portable scanning of human limbs.

The University of Queensland counts two Nobel laureates (Peter C. Doherty and John Harsanyi), over a hundred Olympians winning numerous gold medals, and 117 Rhodes Scholars among its alumni and former staff. University of Queensland’s alumni also include The University of California-San Francisco, The University of Queensland (AU) Chancellor Sam Hawgood, the first female Governor-General of Australia Dame Quentin Bryce, former President of King’s College London (UK) Ed Byrne, member of United Kingdom’s Prime Minister Council for Science and Technology Max Lu, Oscar and Emmy awards winner Geoffrey Rush, triple Grammy Award winner Tim Munro, the former CEO and Chairman of Dow Chemical, and current Director of DowDuPont Andrew N. Liveris.


The University of Queensland has a strong research focus in science, medicine and technology. The university’s research advancement includes pioneering the development of the cervical cancer vaccines, Gardasil and Cervarix, by University of Queensland Professor Ian Frazer. In 2009, the Australian Cancer Research Foundation reported that University of Queensland had taken the lead in numerous areas of cancer research.

In the Commonwealth Government’s Excellence in Research for Australia 2012 National Report, University of Queensland’s research is rated above world standard in more broad fields than at any other Australian university (in 22 broad fields), and more University of Queensland researchers are working in research fields that ERA has assessed as above world standard than at any other Australian university. University of Queensland research in biomedical and clinical health sciences, technology, engineering, biological sciences, chemical sciences, environmental sciences, and physical sciences was ranked above world standard (rating 5).

In 2015, University of Queensland is ranked by Nature Index as the research institution with the highest volume of research output in both interdisciplinary journals Nature and Science within the southern hemisphere, with approximately twofold more output than the global average.

In 2020 Clarivate named 34 UQ professors to its list of Highly Cited Researchers.

Aside from disciplinary-focused teaching and research within the academic faculties, the university maintains a number of interdisciplinary research institutes and centres at the national, state and university levels. For example, the Asia-Pacific Centre for the Responsibility to Protect, the University of Queensland Seismology Station, Heron Island Research Station and the Institute of Modern Languages.

With the support from the Queensland Government, the Australian Government and major donor The Atlantic Philanthropies, The University of Queensland dedicates basic, translational and applied research via the following research-focused institutes:

Institute for Molecular Bioscience – within the Queensland Bioscience Precinct which houses scientists from the CSIRO-Commonwealth Scientific and Industrial Research Organisation (AU) and the Community for Open Antimicrobial Drug Discovery.

Translational Research Institute, which houses The University of Queensland’s Diamantina Institute, School of Medicine and the Mater Medical Research Institute
Australian Institute for Bioengineering and Nanotechnology
Institute for Social Science Research
Sustainable Mineral Institute
Global Change Institute
Queensland Alliance for Environmental Health Science
Queensland Alliance for Agriculture and Food Innovation
Queensland Brain Institute
Centre for Advanced Imaging
Boeing Research and Technology Australia Centre
UQ Dow Centre

The University of Queensland plays a key role in Brisbane Diamantina Health Partners, Queensland’s first academic health science system. This partnership currently comprises Children’s Health Queensland, Mater Health Services, Metro North Hospital and Health Service, Metro South Health, QIMR Berghofer Medical Research Institute, The Queensland University of Technology (AU), The University of Queensland and the Translational Research Institute.

International partnerships

The University of Queensland has a number of agreements in place with many of her international peers, including: Princeton University, The University of Pennsylvania, The University of California, Washington University in St. Louis, The University of Toronto (CA), McGill University (CA), The University of British Columbia (CA), Imperial College London (UK), University College London (UK), The University of Edinburgh (SCT), Balsillie School of International Affairs (CA), Sciences Po (FR), Ludwig Maximilians University of Munich [Ludwig-Maximilians-Universität München](DE), Technical University of Munich [Technische Universität München] (DE), The University of Zürich [Universität Zürich ](CH), The University of Auckland (NZ), The National University of Singapore [universiti kebangsaan singapura] (SG), Nanyang Technological University [Universiti Teknologi Nanyang](SG),Peking University [北京大学](CN), The University of Hong Kong [香港大學] (HKU) (HK), The University of Tokyo[(東京大] (JP), The National Taiwan University [國立臺灣大學](TW), and The Seoul National University [서울대학교](KR).