Paradox-Free Time Travel Is Theoretically Possible: Physicist “Squares the Numbers” on Time Travel

Delorean Time Travel

UQ physicists have been seeking to understand the time travel’s underlying laws. Credit: &

Paradox-free time travel is theoretically possible, according to the mathematical modeling of a prodigious University of Queensland (UQ) undergraduate student.

Fourth-year Bachelor of Advanced Science (Honours) student Germain Tobar has been investigating the possibility of time travel, under the supervision of UQ physicist Dr. Fabio Costa.

“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,” Mr. Tobar said. “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.”

Mr. Tobar said a unified theory that could reconcile both traditional dynamics and Einstein’s Theory of Relativity was the holy grail of physics.

“But the current science says both theories cannot both be true,” he said. “As physicists, we want to understand the Universe’s most basic, underlying laws and for years I’ve been puzzled on how the science of dynamics can square with Einstein’s predictions.”

“I wondered is time travel mathematically possible?”

Mr. Tobar and Dr. Costa say they have found a way to “square the numbers” and Dr. Costa said the calculations could have fascinating consequences for science.

Dr Fabio Costa and Germain Tobar

Dr. Fabio Costa (left) with Bachelor of Advanced Science (Honours) student Germain Tobar. Credit: Ho Vu

“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.”

However, the researchers say their 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.

“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.”

Reference: “Reversible dynamics with closed time-like curves and freedom of choice” by Germain Tobar and Fabio Costa, 21 September 2020, Classical and Quantum Gravity.
DOI: 10.1088/1361-6382/aba4bc

23 Comments on "Paradox-Free Time Travel Is Theoretically Possible: Physicist “Squares the Numbers” on Time Travel"

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

    What if someone were to got back in time and kill their mother before she gave birth to him? How does that get ‘adjusted?’

  2. You decide to go back and end Covid-19; it is Sept 24 2020:
    If you stopped “person-zero” from getting COVID-19, then “person-one” will get it in the “adjustment”.
    Back in Sept 24, 2020, COVID-19 is still around, and you still decide to go back to stop it. So then you are stopping “person-one”, and “person-two” gets the adjustment.
    Back in Sept 24, 2020, COVID-19 is still around, and you still decide to go back to stop it. So then you are stopping “person-two” and “person-three” gets the adjustment.
    So ….. you get trapped in an infinite time-loop from which you can never escape.
    OR this is a poorly written article in which (a) the author did not understand the mathematical model, or (b) the mathematicians did a poor job explaining what they are modeling, or (c) both, or (d) the MODEL is an incorrect model of the “real” universe, even though the “math” that describes the model is error free.
    Whatever the answer, this article left me with more questions than answers regarding the title of the article. WHAT?

    • I don’t think it’s neccessary to get trapped in endless loop. If I would like to try to stop the Patient-Zero from being infected by jumping back in time I would see the futility of the failed attempts and give up after a few loops. More over, jumping back-and-back-to-the-future-again should not cause memory erasure so all the trials would appear to me as a normal cause-effect chain from my perspective, so why should I try again and again? But now we know that timespace could be this self-correcting data stream and I should take this theory into consideration before I try to lose a chunk of >my< lifespan in the history. But that's just me trying to sound logical to myself 🙂

  3. It seems that the poison made by Einstein continues toxicating physicists who blindly believe the current orthodox. They use general relativity as a tool to mathematically speculate the possibility of the existence of closed time curves in the so-called four-dimensional spacetime, but have never seriously defined what time travel really means. When they say somebody time travels to the past, which is the boundary of the person and his surroundings, and how do his surroundings continuously connect from the present to the past? Obviously, there is no way to have a logically consistent definition for so-called time travel.

    It’s true that time scale is different for different physical processes. For example, a rabbit thinks that one year is a long time, but a turtle feels one year is just a blink. Some physical processes can even be reversed. Thus we define our physical time to be irreversible with a fixed scale as shown on a physical clock and use a rate to customize the description of the change of each physical process. For example, when a car has driven 100 km at a speed of 100 km/h, we know it takes one hour time, but then after it has driven for another 100 km backward at the same speed, we still think that the time it takes is another hour rather than a negative one hour because we consider the backward speed is negative, rather than time is negative. If somebody got healthier and looked younger after eating some special food, we would not think that time was reversed but just his aging rate was negative during the period. Reversible physical processes exist everywhere, but our physical time is always irreversible as we have defined.

    Einstein made a fatal mistake in his special relativity. He assumed that the speed of light should be the same relative to all inertial reference frames, which requires the change of the definition of space and time. But he never verified that the newly defined time was still the time measured with physical clocks. Then many mathematicians and theoretical physicists think that time is like a playdough which can be made to fit all kinds of theories, while our physical time measured with physical clocks is stiff and absolute, which won’t change with the change of the definition of the space and time. Actually, the newly defined relativistic time is no longer the time measured with physical clocks, but just a mathematical variable without physical meanings, which can be easily verified as follows:

    We know physical time T has a relationship with the relativistic time t in Einstein’s special relativity: T = tf/k where f is the relativistic frequency of the clock and k is a calibration constant. Now We would like to use the property of our physical time in Lorentz Transformation to verify that the relativistic time defined by Lorentz Transformation is no longer our physical time.

    If you have a clock (clock 1) with you and watch my clock (clock 2) in motion and both clocks are set to be synchronized to show the same physical time T relative to your inertial reference frame, you will see your clock time: T1 = tf1/k1 = T and my clock time: T2 = tf2/k2 = T, where t is the relativistic time of your reference frame, f1 and f2 are the relativistic frequencies of clock 1 and clock 2 respectively, k1 and k2 are calibration constants of the clocks. The two events (Clock1, T1=T, x1=0, y1=0, z1=0, t1=t) and (Clock2, T2=T, x2=vt, y2=0, z2=0, t2=t) are simultaneous measured with both relativistic time t and clock time T in your reference frame. When these two clocks are observed by me in the moving inertial reference frame, according to special relativity, we can use Lorentz Transformation to get the events in my frame (x’, y’, z’, t’): (clock1, T1′, x1’=-vt1′, y1’=0, z1’=0, t1′) and (clock2, T2′, x2’=0, y2’=0, z2’=0, t2′), where T1′ = t1’f1’/k1 = (t/γ)(γf1)/k1 = tf1/k1 = T1 = T and T2′ = t2’f2’/k2 = (γt)(f2/γ)/k2 = tf2/k2 = T2 = T, where γ = 1/sqrt(1-v^2/c^2). That is, no matter observed from which inertial reference frame, the events are still simultaneous measured with physical time T i.e. the two clocks are always synchronized measured with physical time T, but not synchronized measured with relativistic time t’. Therefore, our physical time and the relativistic time behave differently in Lorentz Transformation and thus they are not the same thing. The change of the reference frame only makes changes of the relativistic time from t to t’ and the relativistic frequency from f to f’, which cancel each other in the formula: T = tf/k to make the physical time T unchanged i.e. our physical time is still absolute in special relativity. Therefore, based on the artificial relativistic time, special relativity is wrong, so is general relativity. For more details, please check:

    Once we know our physical time is absolute, there is no room for those mathematicians and theoretical physicists to speculate.

  4. I find it disconcerting that space is never discussed while musing over time travel. The arrow of time moves with space, forward. To travel back in time, one would also need to move in space. So, you may go back in time (if you had a sci-fi apparatus), but, the rest of the universe would proceed on its merry way. Thus, you and your apparatus, going back in time one hour would find that you are out drifting in space because the earth and the rest of the universe continues on it way. Time and space do not readily part ways to accommodate a fantasy. There are probably more profitable areas of conjecture for intelligent students, professors and scientists to spend their time.

    • And because time travel implicitly requires space travel, the amount of energy required becomes mind boggling. Also, because there is a finite limit on the speed of any material object, it means that one can’t go back in time instantaneously. It would require a very long time to move to the position in space occupied by Earth 100 million years ago, even at the speed of light. And, the calculations would have to be unobtainably accurate or one might end up outside the atmosphere, or in the interior of the Earth.

  5. Perhaps we should be changing the name of the website from “Sci-Tech Daily” to “Sci-Assume Daily”?

  6. @Clyde

    You fail no matter what you do. It could turn out that it wasn’t really your mother but a lookalike. Or that you hallucinated it, which wouldn’t be far fetched for someone seriously trying to kill their mother.

  7. So this is still wrong. The events wouldn’t “shift” to prevent the paradox. There IS no paradox. You did it because in your timeline the events happened. But in doing so, youve created a timeline where they didn’t. There is no need for your younger self to go back, but you did. This isn’t a paradox, it’s a different timeline. You crated a branch in the timeline. An alternate universe.

  8. Yeah, “Paradox-Free Time Travel Is Theoretically Possible” … it doesn’t mean that we actually have a time travel, or that some advanced civilization has developed a time travel, after all…
    So! The next idea it might be that aliens are the humans from the future! Yeah, that is a great idea, a really great one…

  9. The act of time traveling is a paradox within itself. It has to happen in the greater time line for everything afterwards to occur. Also, the Russians already achieved a six minute time travel a decade ago…

  10. “I wondered: “is time travel mathematically possible?”

    Well, we all have asked our self the very same question. However, we have no evidence of such a thing happening, or ever happened. Though, it would be great.
    Second thing is that time dilatation, which has been proven correct, but was it perceived in a proper way, or it is just the numbers that mean something else.

  11. According to current physical theory, is it possible for a human being to travel through time?

  12. … ask Goedel, he would know about paradoxes that might arise from theory of relativity…

  13. It would correct itself if you tried to kill your mother by someone stopping you from doing it or you leave thinking your mother is dead but isn’t or even that you’re giving birth to buy a different woman. And this time travel thing kind of plays along in the theory that our universe is actually the interior of a black hole just inside the horizon. A wormhole would be like getting right to the edge of the horizon and then it bending you back around to a point in the past as you try to cross it. Which kind of goes along with the fact that if you tried to travel in a straight line away from the Earth fast enough for long enough you would get back to the Earth except if the speed is fast enough you would get back to the Earth in the future though you would not have aged. But anyway going back in the past and killing your mother would be made impossible by whatever happened to stop you from killing her. Moreover you would never even be allowed to meet her at least not where she’s aware that it’s you because that would change the future. So impossible to kill your mother in the past no matter how hard you tried. And people like to say well if sometime people invent time travel to the past why haven’t they come back and talk to us. Maybe it’s impossible because of time correcting itself. Or if creating a paradox is possible people of the future realize that they could wipe themselves out and interference with the past is not something they do. They only observe. Maybe even have rules for exactly when they’re allowed to go to. Maybe they’re only allowed to travel to prehistory. Not travel to somewhere where it could cause a paradox just by knowing someone’s from the future.

  14. Steven Lee Hanson | August 4, 2021 at 2:24 pm | Reply

    All of these comments are interesting and informative.

    But they all assume a past Paradigm that only Time Moves. We are holding onto a rock in the river of Time as the current flows past us from the Past through the Present and into the Future.

    We are not holding onto the rock of Earth as the Sun, planets, stars and galaxies flow around us. We move through moving Space.

    ALL OF THESE VIEWS also assume we can change Time with our actions.
    (Drop your egocentric notions.)

    We move through moving spacetime.

    A Paradigm Shift from geocentric to heliocentric helped explain our neighboring space.

    A Paradigm Shift from Newton to Einstein helped explain our neighboring spacetime.

    Publishing my spacetime / mattergy Paradigm Shift Work
    will solve all your Paradoxes.

  15. Time travel could very well be possible in this day and age. But it may be a whole lot slower than people would imagine.

  16. That Old Cartoonist | May 4, 2022 at 10:31 am | Reply

    I’ve been travelling forward in time for sixty years.

  17. Time travel? The paradox that these two words conjure in one’s analytical mind are endless. No two people imagine what these words mean in the same way. Some believe only a single body jumps through time with all the cognitive capabilities and memories of another time left in tact. Where others imagine the time travelers mind and memories also change to synchronize with the time visited. Does this insinuation limit time travel for someone to the number of years they have been alive? And does the visitation of a time where the traveler was an infant subject that person to a life of Deja-Vu episodes? Does the number of times one has time traveled have a direct correlation with an elevated intelligence to reasoning capability? If so, would that be a reason to assume an increased intellectual capability of anyone who leaps through time to visit our planet. And No, the mere virtue of them having the technology to travel in that method does not imply they must understand how it works. Look how many use modern conveniences regularly with no clue as to their engineering. Everything a person does in this modern society is by the grace of someone else’s knowledge and occupation. My guess is that if time travel is possible, the ancillary effects of doing so would be unavoidable. Nothing in this universe has only positive result. For every action does have an equal and opposite reaction. My luck I would leap to a time in the future, and find its one day after my burial. Oh Chit!

  18. How could you travel back to a period of time from which you have no memory of to a place you’ve never seen or have no accurate visual representation of in your memory I can travel anywhere I’ve never been in the universe but will only become aware of its spatial and physical and visual properties once I have arrived at that location in space and time or have at least observed it at a distance before arriving there so how could you ever go to a place or time in the universe that never entered your light cone

  19. You can mathematically prove anything just like you could make anything bad sound good if you shuffle the words around enough numbers and ideas are all creations of our minds to help us understand our existence the truth is our ideas and our perception of reality is the universe we are nothing more than a way for the universe to know itself for it to feel and see what it is and in that we are stuck in an infinite unbreakable loop of never being able to break out of the constraints the universe (us/we) have put on ourselves or fully understand the nature of our own existence because we all came from nothing and therefore are nothing but what the universe imagines itself to be

  20. I’ll admit it is fun to try to imagine anything is possible and maybe that’s enough to make anything possible

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