Cooper, Murph, Dr. Amelia Brand, and Dr. Mann ring a bell? If you are a fan of science fiction, you’d have exclaimed “Aha!” by Murph. Yes, they are beloved characters from Christopher Nolan’s film, Interstellar, the film renowned theoretical physicist Michio Kaku, in a CBS News interview, said “could set the gold standard for science fiction movies for years to come.”
This is not about the movie, however, but about time travel, the film’s central theme, and one of the thought-provoking science concepts your children can learn when you enroll them in Premier Genie’s winter camp for kids Dubai edition.
So, is time travel possible?
The Science of Time Travel: Einstein’s Theories of Relativity
Much of the support for the possibility of time travel comes from Albert Einstein’s theories of relativity (special relativity, 1905, and general relativity, 1915).
Einstein’s theories of relativity basically say that time dilation happens when a person is in motion or has lower gravitational potential. Therefore, a person in motion or a person with lower gravitational potential ages slower than the person at rest or the person with higher gravitational potential.
To put it simply, Einstein’s special relativity theory states that time is a construct, and it moves differently for someone at rest and for someone in motion. Specifically, the closer your speed approaches the speed of light, the slower time moves for you.
A simple thought exercise can confirm this phenomenon for you.
Suppose you have a light clock that emits a pulse of light to a mirror, and the mirror bounces the light back to the clock. Upon detection of the returned light, the clock emits a clicking sound. It then emits another light pulse to the receiving mirror, continuing the cycle.
If this imaginary light clock is stationary or unmoving, you can expect the clicking sounds at constant intervals. In other words, it will take precisely the same amount of time for every cycle of the clock emitting a pulse of light, the mirror reflecting it to the clock, and the clock making a clicking sound.
However, suppose the light clock is moving at a certain speed. The clock still emits its light pulse, and the mirror still bounces the light back. However, since the clock is in motion, it will have moved away from its initial location when it emitted the original pulse of light. Therefore, from an observer’s perspective, it will take a longer time for the reflected light to reach the clock, and thus, it will take a longer time before the observer hears the clock’s clicking sound.
Therefore, between the stationary clock and the moving clock, an observer will hear longer intervals between clicking sounds for the latter than the former. Time — represented by the clicks — moves slower for the moving clock.
Now, suppose the moving clock moves at an even faster rate. After emitting a pulse of light, it will now have traveled an even larger distance than before. This means the reflected light from the mirror will also take a longer time to reach the clock back. Effectively for an observer, there will be an even longer interval between the moving clock’s clicking sounds, which means time travels even more slowly for a faster-moving clock.
In short, time moves slower for a moving object, and the faster a moving object’s speed, the slower its time moves. To put it another way, the closer to the speed of light an object travels, the slower time moves.
This theory of special relativity is actually considered when using technologies and services that rely on satellites (e.g., global positioning system or GPS, very small aperture terminal or VSAT, etc.). Satellites move in orbit; they’re not stationary. For them, time moves slower than it does on Earth.
Einstein’s general relativity theory accounts for the effect of gravity. The closer someone is to a massive body (one with enormous gravitational pull), the lower his gravitational potential. Therefore, the slower time moves for him than for a person much farther away from the source of gravity.
This is wonderfully demonstrated in the film, Interstellar.
Cooper and Dr. Amelia Brand took a lander and visited Laura Miller’s planet, the closest to the black hole “Gargantua” (read: a massive body with enormous gravitational pull). Their extremely low gravitational potential caused time to slow down significantly for them.
When they returned to their spacecraft “Endurance” after being gone for a few hours, 23 years had already passed for Romilly, the crew member left on the spaceship.
You Can Slow Down Time, but Can You Travel Through It?
Science says you can travel forward through time. Just travel fast or close to a gravitational anomaly. This means, since time is relative, you can travel forward through time by moving at speeds approaching the speed of light or being close to a black hole, either of which will slow time down for you.
However, traveling back through time is more challenging. You will need to overcome the speed of light, that is, travel faster than light to travel backward through time. However, this is physically impossible because as you approach the speed of light, your mass increases apace. After a certain point, your great mass will inhibit further acceleration.
A Wormhole Is an Answer
Theoretically, if you can find a wormhole, there is a way to travel forward or backward through time.
Imagine the space-time continuum as a sheet of paper. Fold it so it’s curved in on itself (like a letter C) and the joined edges look like there are two sheets of paper overlaid, one on top of each other. Now, punch a hole through the center of the “overlaid sheets” and use a straw to connect the two holes. That’s your wormhole.
A wormhole is a link or a shortcut between one point of the space-time continuum to the other. Therefore, if you have a wormhole connecting two points in time — e.g., the future and the past — you can enter from the future and exit to the past and vice-versa.
That’s not all wormholes can do, of course. They can connect distant regions in the universe, so you can reach places much farther away without traveling for an extremely long time. They can also link different universes (think parallel universes connected by wormholes).
Can We Use a Wormhole for Time Travel?
Wormholes exist in theory, but man is yet to find an actual wormhole. Furthermore, wormholes are prone to collapse and are highly radioactive, too. The way things are, and based on what is known about wormholes so far, it is unlikely humans can travel through wormholes.
Of course, there’s hope. Perhaps, the technology needed for man to stabilize wormholes and to create machines or protective gear that will let humans traverse wormholes without expiring from extreme radioactivity, among others, is yet to come.
So, can you travel through time? It is highly unlikely for now, but in the future, who knows?