Cosmox Blogs

Jun 04, 2022

Time Travel by Time Dilation

Time Travel

The concept of time travel has always excited people and has been a famous part of physics and pop culture. The idea of a time machine was popularized by H. G. Wells' 1895 novel The Time Machine.

If you would have ever heard of time travel, the first thing which comes to your mind would be a person going inside a typical sci-fi machine and going inside a sphere traveling to the future. Well, that’s how it is shown in most sci-fi movies, and for a moment you must have thought that it is impossible to time travel but you might be surprised that it actually is. How so well let me tell you that it is not in the way that you imagine. There are a lot of ways to time travel to the Future.

Special relativistic time dilation:

Our perception of time that it is absolute is nothing but an illusion, time is not absolute it is relative. The faster you move through space the slower you move through time. This phenomenon was described by Albert Einstein in his general theory of relativity. This means that for every single thing time is different, for each person, object, or particle moving at different speeds. But now you might ask if that’s so then why don’t we experience it in our daily lives? Now here is the thing, there is a difference but it’s very small, for instance, let’s say if a person A is at rest with a clock and person B is in an aircraft moving at a high speed for a while and when their clocks are compared it is seen that for person B time was moving slower compared to Person A who was at rest but the difference is in nanoseconds (billionth of a second). Now you will probably think that if this is the case, why we are even considering this as an option of time traveling to the future. Well, this changes when you are traveling near the speed of light (or relativistic speed), when traveling at such a high speed which is about 3,00,000 km/s, time would be significantly dilated. For instance, if you travel at the speed of light for a few years, decades will have been passed for the people on earth when you come back and you will be only a few years old.

A real-life example of special relativistic time dilation is the satellites that orbit the earth at a speed of about 11,300 km/h, at this speed time gets microseconds slow for them every day compared to earth. Due to that reason every day the time is fixed.

Gravitational time dilation:

Just as time can be dilated by the speed it can also be dilated by gravity, how you might ask, the answer is that gravity is not a force but a curvature in the spacetime fabric. Now space and time are two sides of the same coin, they both are connected, therefore it is called spacetime, objects with mass curve this fabric of spacetime, which bends time also. The more the mass an object has the more it will curve the spacetime fabric and hence more will be the time dilation.

For instance, there is person A who is on Earth and then there is person B near a black hole, now blacks are the celestial objects formed when a star at least 3 solar masses (3 times bigger than the sun), runs out of thermonuclear fuel and collapses inward upon itself due to its own gravity, creating a gravitational singularity. A point that has such strong gravity that even light cannot escape it. Singularity is present at the center of a black hole and anything which crosses the event horizon of a black hole will be crushed at the singularity.

Now since these are the heaviest objects in the universe they warp spacetime so much that time almost stops at the singularity and laws of physics break down there.

For person B who is near a black hole time will be so much dilated that a few minutes for Person B would be decades or even centuries for Person A and everything else far away from the black hole, and when that person would come to earth eons would have passed. This concept was also shown in the movie interstellar.

Gravitational time dilation has been proved with the help of atomic clocks and certain experiments. One real-life example is that a person living at the sea level would age slower compared to the person living at the top of a mountain because the person living at the sea level is closer to the center of the earth, therefore the time will pass slower for them(difference in their ages would be in nanoseconds). Therefore earth’s core is 2.5 years younger than its surface.

Cryosleep:

Cryosleep is a process in which a person is put into a state of suspended animation using a drug or a chamber or something very cold and it is a common sci-fi trope. It may be called a way to cheat death, where a person's life form may be suspended at -200 degrees Celsius and probably preserved in liquid nitrogen. Now when this happens a person’s growth gets significantly slow, slowing down the chemical reactions in the body, and hence aging almost stops. This concept was also shown in the movie passengers

Interestingly, NASA, in partnership with SpaceWorks Enterprises, has been developing a cryogenic sleep chamber for astronauts. The “cryosleep” technology works by lowering the astronaut's body temperature to 89-93°F (32-34°C), causing them to slip into a sort of hibernation.

As technology is progressing this is now taking a shape of reality and soon space companies would put a lot of people into a hibernation pod and launch them to different sorts of planets to explore them and make humans a multi planetary species.

Conclusion

As time passes, soon we will be able to venture into different timelines, and space companies like NASA are trying to develop light speed engines and hibernation pods to make time travel to the future possible. Now let’s see what the future has in store for us.