Introduction

I have written about the Laws of Time Travel as part of my earlier blogs. However, I realized that these laws need to be well defined so that they can be referred by anyone anytime. These laws are quite different than the popular belief.

These laws are based on Einstein’s Theory of Relativity. Time as we experience everyday is not the same everywhere. Scientists have struggled to understand and explain time using thought experiments, spacetime diagrams and mathematics. The mathematics and spacetime diagrams do not scale well and leads to infinity very quickly. This has led to a lot of misunderstanding regarding Time Travel. Though I published the Laws of Time Travel 10 years back in my blog “Time Travel will remain fiction forever“, the myths still prevail everywhere.

The Laws of Time Travel

1. Time always moves forward

Time always moves forward for everyone. Time always moves forward for everyone. You can go ahead in time, but you cannot come back. If you understand this you understand time travel correctly. It is not a mistake. The first line is repeated on purpose.

2. Time is relative

Though Time moves forward, the rate at which time passes is not the same for everyone. The rate of time passage is different for people at different gravity and traveling at different speed. People with you will have time moving at same rate. Astronauts in space station, traveling at higher speeds and away from earth’s gravity, have time running slightly slower than earth (0.007 secs behind for every 6 months).

3. You can travel to future

By going to a place where time passes slowly and returning back to earth, you are in future. For example, you could travel to a place near a black hole, where time passes more slowly and return to earth. Remember you have to leave earth, spend a few seconds near a black hole and return back to see that many years have passed on earth.

4. You can travel to any time in future

You spend a few seconds near a black hole can return back 10 years in future, 100 years in future or 1000 years in future, depending on whether it was a supeassive black hole or how far you were from the black hole.

5. You can travel to past

By going to a place where time passes more quickly and returning back, time moves only slightly ahead on earth and you assume you have returned to past. For example, you could travel to a place near a neutron star, where time passes more quickly than on Earth and return back. Here too, you leave earth, go to neutron star spend many years and return back to see only few seconds have passed on earth. You believe that you have come to past as nothing much has changed in few seconds.

6. You cannot travel back beyond a point.

You believe you have travelled to the past as only fews seconds have passed. Time always moves forward. So there is no way you can travel back in time to see dinosaurs. You cannot even go back in time even a few seconds to see yourself again.

7. You are always in present time.

When you travel to the future or past, you are always in the present time of that place. For example, you leave earth now, you reach black hole in it’s present time, spend few seconds, return to earth’s present time which has moved many years ahead. You believe you are in future.

8. Time Travel is just your perspective.

You see that whether traveling to past or future, you reach present time on earth. You believe you are in future as time has moved ahead many years or you believe you are in past as time has not moved much on earth. If you had come from a black hole or a neutron star, without first leaving earth, you would not see it as a Time Travel. It is your perspective that you have come to future or past. You are always in the present on earth, yet you have done real Time Travel. That is the real paradox. All other paradoxes are science fiction.

9. You cannot meet yourself – Time is not slice of bread.

Time is not like slice of bread, where you can travel backward and forward. You can see from the above laws that, whether you travelled to future or past you cannot meet yourself. Once you understand this law, even the paradox in law 8 above disappears.

10. Time Travel laws are different from Fiction

You can leave earth and come back in future a 1000 years ahead on earth spending a few seconds at black hole. You can leave earth, spend 1000 years at a neutron star, your future generation return back to earth to see only few seconds have passed on earth. You future generation believe they have come to past. You see that it is possible to travel to future, but not in past. You can also see that it is impossible to meet yourself either in past or in future. You see that though Time Travel is possible, the laws are quite different than that we see in popular science fiction. We must give up all earlier views to understand real Time Travel.

Where did these law come from?

It started with a curious blog in 2014 on possibility of Time Travel, “Will Time Travel remain fiction forever?” As we reached the conclusion, We realised that Time Travel is real and largely misunderstood. We had listed the laws of Time Travel in the blog.

Our curiosity lead us to publish two articles on Time Travel in popular Science Journal, IJSR. The first one in Feb-2016, “Relativity without Complexity” explained – Relativity, the science of Time Travel without mathematics. The second paper we published in Apr-2023, “Relativity without Formulae“, simplified the two formula of Time Travel based on speed and gravity from Special and General theory of Relativity respectively. They both mention the laws of time travel. In fact, the two derived formula are a result of these laws of time travel.

Why these laws are important?

There were no well defined Laws of time travel. This caused many to come up with their own concept of time, their own concept of how the theory of Relativity can be used to travel in past and future and build stories and paradoxes for movies that excite the general public. One book in particular that came even before the theory of Relativity was H. G. Well’s “The Time Machine”. It’s story with it’s unwritten laws of time travel still stays with everyone in one form or another even after a century.

Many good scientists stuck in Time Travel loop (paradoxes) created even more complex paradoxes and theories, struggling very hard to get around the concept of Time.

These laws of Time Travel are simple yet have been elusive to everyone. Every Google search, every science book, every YouTube video (even from the people we respected and followed for scientific knowledge), even ChatGPT and Bard give incorrect and incomplete knowledge. They were doing more harm to science and themselves.

Even after 100 years of Theory of Relativity, the concept of Time Travel is still considered to be a mere theory and speculation. While Time Travel is possible, the concept of Time Travel that is in everyone’s mind is not correct.

There is one thing that scientists are still struggling with. It is the speed of light limit. It is largely considered that time will run backwards beyond the speed of light. That had given rise to all these paradoxes.

Yes, that can happen. But now that we have listed our laws of Time Travel, we have an answer. Time will run backwards, if that really happens, but it will be relative to us. Once you come back you are in present time. And time always moves forward for everyone. Even for you when you are traveling faster than light.

Getting rid of Paradoxes

Now that the Laws of Time Travel is listed and defined, it is time to get rid of all the wrong and unnecessary Paradoxes that have been created in everyone’s mind. Most of these paradoxes are created to explain time travel to past. The laws of Time Travel that we defined, tells us that going into past prior to starting point or meeting yourself in past or future is not possible. Also time runs ahead for everyone.

So we must let go of these Paradoxes.

• Grandfather Paradox: Here the Time Traveller tries to go back in Time and kill his grandfather. That way neither his father nor he would be born. But if he is not born how would he go back in time and kill his grandfather. This is called the most famous grandfather paradox.
• Causality: Causality tells us that first there is a cause then the result and never the result first and then cause. So, they reason that Traveling back in time is not possible. If we travel back in Time, the causality will break. While it confirms to the laws of Time Travel, the reasoning is wrong and unnecessary.
• The butterfly effect: This principle states that even small changes in the past can have large consequences in the future. It would have ripple effect and lead to completely different future.
• The Novikov self-consistency principle: This principle states that any time travel that would create a paradox will be prevented from happening by the laws of physics. For example, if a time traveler tried to kill their own grandfather, the time machine would malfunction or the time traveler would simply be unable to carry out the act.
• The bootstrap paradox: This paradox occurs when an object or event is created in the past by a time traveler who brought it back from the future. For example, a time traveler might bring back a watch that they will later give to their grandfather. This would create a paradox because the watch could not have existed in the past unless the time traveler brought it back from the future.
• Wormholes: Some theoretical physicists have proposed the concept of wormholes, which are hypothetical tunnels in spacetime that could potentially allow for shortcuts through space and time. Traveling through wormholes, if ever possible, will not allow Time Travel to past as suggested by many.
• Closed Timelike Curves (CTCs): Closed timelike curves are mathematical solutions to the equations of general relativity that suggest the possibility of time loops or closed loops in spacetime. These solutions often involve exotic matter or other conditions that may not exist in our universe. Like, wormholes, CTCs will also not allow Time Travel to past.
• The Twins Paradox: This paradox conforms to the laws of Time Travel and is usually used as an example for explaining Relativity. Here one of the twins goes into space traveling at much higher speeds and returns after say one year. He finds that 10 years have passed on earth and his twin is 10 years older than him. The problem with this Paradox is that it involves traveling at higher speeds, staying in space for years, mathematical calculations with the end result in terms of years is not much to entice a true Time Travel fan. Further, it avoids Time Travel to past. A better alternative is my Teleportation example in earlier blogs, which explains both Time running slow and fast.

Conclusion

The scientific laws of Time Travel are quite different than in science fiction. Many paradoxes of Time Travel need to be discontinued if we want to go forward.

I would like you to identify the paradoxes of Time Travel you encounter in movies and science books and elsewhere and test them against the Laws of Time Travel. Do they agree or disagree with these laws. Share them in comments below.

Time Travel is not impossible, we do it all the time. But the kind of Time Travel we expect is not yet feasible with current technology. We either need to travel significantly faster or go to a place with significantly different gravity. These laws become important as we start thinking in terms of intergalactic travel. If you have not realised yet, these are the laws of Relativity, the laws of spacetime, the laws of the Universe!