Is Time Travel Scientifically Possible?
By Jon Therkildsen, MSc MBA from University of Århus (2004)
THIS ARTICLE WILL ADDRESS AND ANSWER THE FOLLOWING:
CAN TIME DILATION MOVE US FORWARD IN TIME?
CAN WE TRAVEL BACK IN TIME?
WHAT IS THE SOLUTION TO TIME PARADOXES?
WHAT DO THE LAWS OF THERMODYNAMICS SAY ABOUT TIME TRAVEL?
Yes, absolutely. Time travel is scientifically possible. No law of science prohibits time travel, and, in fact, we have specific theories that explain how it might work. Often the “Law of Conservation of Energy” is invoked as a counterargument, but this misunderstands the very law. More on that later, at the end of this article. Other popular notions also claim to shoot down the possibility. All of which I will address too.
The short answer is: Yes, it is possible; we know exactly how to do it; we have done it; and it happens all the time around you.
CAN TIME DILATION MOVE US FASTER TO A FUTURE?
Yes, it can, and we already know how to do it.
Einstein’s theories of relativity revealed that time is not absolute. It depends on both speed and gravity, meaning different observers can experience time at different rates. Not as an illusion, no, as actually different ticking times. In principle, you could step into a machine, spend a week inside, and emerge to find that a century has passed on Earth. This is not science fiction. It is physically possible. Undoubtedly.
Special Relativity (1905): Time and Speed
The faster you move relative to someone else, the slower time passes for you. This effect, called time dilation, occurs at any speed - be it a stroll in the park or in a spaceship whooshing away. The closer you get to the speed of light, the more dramatic the difference becomes, but the effect appears at any speed. Move your arms, and their time will tick slower than your stationary heart. It sounds preposterous, but experimentation confirms beyond any reasonable doubt that speed causes time to tick more slowly (it is a fact our satellites noticeably live by). Imagine for a moment that you are in a vehicle moving very fast, for example, in circles. Once you step out, the world around you will have aged compared to you - you will have effectively traveled to your future.
At the speed of light itself, time will slow down so much that it would effectively stop for the traveler. Meaning this allows travel to any moment in the future, instantly (from the traveler’s perspective). Of course, nothing with mass can reach that speed. But a photon of light - which does travel at light speed - experiences zero passage of time. From a photon’s perspective, the instant it leaves a distant star is the same instant it reaches your telescope, even if the journey took a billion years from our point of view. To it, no time has passed at all. A billion years compressed into a single moment. That’s the ultimate fast-forward through time.
Speed is all it takes.
General Relativity (1915): Time and Gravity
Gravity also warps time. The stronger the gravitational field, the slower time runs. On Earth, time ticks slightly slower than it does in deep space. The difference is extremely small, but your feet (closer to Earth’s center) are technically a tiny fraction of a second younger than your head. If you live near something massive (aka stronger gravitation), such as a mountain, your time is actually ticking slightly slower than if you were not.
We see this effect clearly with GPS satellites. They orbit high above Earth, where gravity is weaker and they move at high speed. As a result, their clocks run 38 microseconds faster per day than clocks on the ground. Engineers must correct for this relativistic difference every day - otherwise GPS would quickly become useless. This is real, measured, and precisely matches Einstein’s predictions.
Every object in the universe experiences time at a slightly different rate depending on its speed and gravitational environment. Your morning run, a flight across the ocean, or a ride on the bus all push you microscopically into the future relative to someone standing still.
The effect is usually negligible for everyday life, but the principle is profound: we are all time travelers, moving into the future at slightly different speeds. Or stand near something heavy, and its massiveness will nudge ever so lightly, too.
HOW DO WE TRAVEL BACK IN TIME?
While time dilation allows us to travel forward in time faster than normal, it offers no path backward to a moment we’ve already lived. It’s strictly a one-way ticket into the future.
As we approach the speed of light, time slows for the traveler relative to everyone else. However, the cosmic speed limit - the speed of light (approximately 300,000 km/s) - is absolute. Nothing with mass can reach or exceed it. You can read more about why here. Hypothetically, if you could somehow travel faster than light, the equations of special relativity would yield results of what some see as “negative time.” Some interpret this as traveling backward in time. Others see it as mathematical nonsense. Either way, it remains an academic exercise: you cannot simply plug impossible values into the equations and claim it reveals a real physical pathway. The universe doesn’t allow “all else equal” violations of its fundamental limits.
Fortunately, General Relativity offers a more promising - though far more complex - route to the past. In 1988, physicist Kip Thorne and colleagues showed that a traversable wormhole could, in principle, be turned into a time machine. Here’s the simplified version:
Imagine creating two connected wormholes in the year 2028. You then move one wormhole at near-light speed or park it near a strong gravitational field (such as a black hole). Time dilation causes time to pass much more slowly at that wormhole compared to its stationary sister. This way, one hole is moving to the future, while the other is still locked here in 2028. Because the two ends remain connected, a traveler could enter one wormhole in the future and emerge from the other in 2028, effectively traveling back to the moment the device was first activated. This method only allows travel back to the wormhole’s creation date (in this case, the year 2028). It cannot send you to the dinosaurs or fix last week’s mistakes. Still, it offers a theoretical doorway to the past once the technology exists. We know how to, just not technically how.
It does not help us now, but it gives comfort knowing it might someday.
So in conclusion, we already know how to move through time at different rates - your car, an airplane, or even orbiting astronauts do it daily (though the effect is tiny). Eating your vegetables and exercising remain a far more practical way to gain a little extra time.
Traveling backward, however, is vastly more difficult. It would likely require godlike engineering: stable traversable wormholes kept open with exotic matter, enormous energy, and solutions to countless stability and causality problems. But the mathematics of General Relativity does not forbid it.
The door is not yet open… but it is not firmly locked either.
HOW DO WE AVOID REALITY SCATTERING PARADOXES?
A time paradox arises when traveling to the past and changing something that would prevent the trip from ever happening in the first place. The classic example is the grandfather paradox: What if you went back in time and killed your grandfather before he met your grandmother? You would never be born - and therefore never be able to travel back and commit the act. But if you never traveled back, your grandfather would live, you would be born, and the cycle repeats. Paradox.
Some dramatic solutions have been proposed: the universe might collapse, the timeline might somehow forbid the change, or you might simply fade from existence (as Marty McFly nearly did in “Back to the Future” (1985)). In truth, we don’t know what would happen, because we don’t yet know whether changing the past is even possible.
However, quantum mechanics offers an elegant way out.
The Many-Worlds Interpretation (MWI) of quantum mechanics suggests that whenever a quantum event has multiple possible outcomes, the universe branches into parallel realities - one for each possibility. In one branch, you turn left; in another, you turn right. These branches split constantly, creating an ever-growing tree of parallel universes. Though it sounds wild, MWI is a serious and influential interpretation that resolves many puzzles in quantum mechanics. If not the most, it is considered the second-most widely accepted interpretation of quantum mechanics.
Applied to time travel, this interpretation dissolves paradoxes beautifully. If you traveled to the past and killed your grandfather, you wouldn’t erase your own existence. Instead, you would create (or shift into) a new branch of reality - a parallel timeline in which your grandfather dies, and you were never born. Your original timeline, where your grandfather lived and you were born, continues unaffected. You remain safe in your own world.
The tree illustrates your life, your timeline. For every action, there is another world where you perform the opposite action, etc. When you travel in time, you are setting off new branches in your tree of life.
In this framework, every change you make while time traveling simply generates new branches. The consequences stay in those parallel worlds. Your original history remains intact.
Any conceivable time travel paradox is solved this way. Any consequences created by meddling with the timeline will be in parallel worlds, not yours.
There are paradoxes no more.
How can a time travel machine avoid STRANDING YOU IN DEEP SPACE?
Earth is constantly hurtling through space - orbiting the Sun, spinning on its axis, and moving with the Solar System around the galactic center. So if you jump forward or backward in time, wouldn’t the Earth be in a completely different location, leaving you floating helplessly in the void?
This is a popular “gotcha” question, and it sounds clever at first. In reality, it overlooks something basic: navigation.
Any form of travel in our universe - whether through space or through time - requires proper coordinates. Trains, cars, airplanes, GPS, even a walk to the corner store, all rely on knowing exactly where and when you want to be. Our reality is four-dimensional (three spatial dimensions plus time), so specifying a destination in spacetime naturally requires four coordinates.
Invite someone on a date and give them only the location but not the time - you will never meet.
Give them only the time, but not the location - you will never meet.
Send a probe to Mars with precise spatial targeting but no timing component —it would never land… at least not on Mars.
A functional time machine would operate on the same principle. It wouldn’t just jump to a specific time; it would target a specific spacetime coordinate - the exact location of your chosen spot on Earth at that moment. The machine would calculate the Earth’s position relative to the Sun, distant stars, or other stable reference points, much like how sailors once navigated using celestial bodies.
As long as the time machine is properly engineered (and you definitely shouldn’t buy one from IKEA), it should deliver you safely to the right time and certainly the right place.
THE LAWS OF THERMODYNAMICS
There are no laws or theories in science that prohibit time travel. And I hope this article has shed some light on several theories that actually support the mechanics of time travel. The Law of Thermodynamics does, however, provide a concern:
The First Law of Thermodynamics (aka the Law of Conservation of Energy): Energy cannot be created or destroyed in an isolated system.
The Second Law of Thermodynamics: Isolated systems tend toward an equilibrium state of total entropy, where no energy is available to perform useful work.
The third law of thermodynamics: As temperature approaches absolute zero, the entropy of a system (whether isolated, closed, or open) approaches a constant absolute value.
At first glance, time travel seems thermodynamically problematic:
Arriving in the past or future appears to “add” energy and matter where it didn’t previously exist (First Law).
Your presence might locally decrease entropy or reverse its natural increase (Second Law).
You would introduce heat in the past, raising the local temperature (Third Law).
These concerns are understandable, but they do not actually violate the laws of thermodynamics.
All three laws are statements about isolated systems - systems that exchange neither matter nor energy with their surroundings. This crucial detail is a prerequisite for the laws to be in effect. If a system is not isolated, the laws do not apply to that system. When you travel through time, you move between what can be treated as distinct systems (your original timeline and the destination timeline). The act of traveling “de-isolates” them by creating a connection, and this de-isolation makes the laws void at that moment, because then the timelines are no longer isolated. Once these timelines are linked, they form a single, larger system that can again be considered an isolated system. Within this new combined system, the laws of thermodynamics are therefore restored to full validity hereafter - until, of course, you choose to leave this system, again de-isolating it.
For the First Law, the accounting is also straightforward if we view all timelines as one grand system up front, rather than as distinct systems as above. When you travel amongst timelines under one unified system, the total energy balance remains unchanged: leaving 2028 (“2028 minus you”) and arriving in 1975 (“1975 plus you”) produces no net gain or loss in energy or matter within this system. Conservation holds.
The Second and Third Laws require a bit more nuance because they describe tendencies over time. Entropy tends toward a maximum in an isolated system, and entropy approaches a minimum as temperature nears absolute zero. These are directional statements aligned with the arrow of time. Your arrival introduces a local perturbation, a temporary fluctuation in entropy or temperature, but it does not erase the underlying tendency of the larger system. Such local changes are fully permitted in thermodynamics; the second and third laws are not absolute prohibitions against external influences or short-term deviations.
Having said that, Past, present, and future timelines are best understood as initially separate systems until a time traveler bridges them. If you start combining systems, you can absolutely add matter, import energy, or even reduce the entropy of one subsystem without breaking a single rule of physics. The laws of thermodynamics govern processes within systems. They are not barriers to movement or interaction between systems. Once the bridge forms, the combined system simply re-equilibrates under the same laws, with no net violation.
The laws of thermodynamics are profound cornerstones of physics. They elegantly describe energy, entropy, and temperature inside a given system. They do not, however, rule out the possibility of traveling across systems. Time travel may face enormous practical, causal, and engineering challenges - but a fundamental thermodynamic prohibition is not one of them.
EPILOGUE
The above article is not indirectly representing my view on time travel. I have no idea if it will ever be possible in any remarkable sense. Likely, I think it won't. But my article aims to show how our science supports the possibility, as I believe this fact is generally and unfairly ridiculed.
Attribution: I am often asked if Time Dilation has been confirmed? As expressed, in the article: yes it has, beyond any reasonable doubt. For reference, see, for example, these experiments: Pound–Rebka experiment (1959), Hafele–Keating experiment (1971), Gravity Probe A experiment (1976), Iijima et al. experiments (1975 - 1977), Chou et al. experiments (2010), Via our Particle Accelerators; fx (2014), van Baak et al. experiments (2005 - 2016) & Wayward Satellite Experiments (2019), etc.
Photos via Google