What is Time Travel ? Is it Possible?

Time Travel

The capacity to travel through time, whether to correct a past error or gain insight into the future, has long been a favorite of science fiction and a source of discussion among theoretical physicists. While the discussion over whether or not it is conceivable to travel into the past continues, scientists have decided that traveling into the future is most certainly possible. You don't even need a wormhole or a DeLorean to accomplish this.

Time dilation, a characteristic of Einstein's special relativity, is used in real-life time travel. Einstein was the first to recognize that, contrary to popular belief, time does not remain constant as you move faster across space.

Einstein reimagined space itself as part of his theory. He coined the term "spacetime," which combines the three dimensions of space and the one dimension of time into one concept. Instead of thinking of space as a flat and rigid place that holds all of the objects in the universe, Einstein saw it as curved and malleable, capable of forming gravitational dips around masses that pull other objects in, similar to how a bowling ball in the center of a trampoline causes any smaller object on the trampoline to slide towards the center.

The closer an object approaches the dip's center, the faster it accelerates. The gravitational dip's center is found at the Earth's core, where gravitational acceleration is greatest. Because time slows down as you move faster through space, according to Einstein's theory, the closer an object is to the Earth's center, the slower time passes for that thing.

GPS satellites, which orbit 20,200 kilometers above the Earth's surface, exhibit this effect. Due to time dilation, these satellites have exact clocks onboard that gain an average of 38 microseconds per day. While the time advantage may appear tiny, GPS satellites rely on their inbuilt clocks to keep their worldwide positioning exact. Running at 38 microseconds per second would result in a location mistake of roughly 10 kilometers, which would grow every day if the timing difference was not adjusted regularly.

In the movie Interstellar, Matthew McConaughey and his crew land on a planet with an intense gravitational field created by a nearby black hole, which causes time dilation. Time slows drastically for the crew on the planet due to the black hole's immense gravitational effect, making one hour on the surface comparable to seven years on Earth. This explains why Matthew McConaughey's daughter is an older woman when the team returns to Earth, yet he looks to be the same age as when he departed.

So, why hasn't humanity been able to make such significant jumps forward in time? This question has a simple answer: velocity. To send a traveler years into the future, humanity would have to either use the extreme gravitational acceleration induced by black holes or send the traveler rocketing into space close to the speed of light (approximately 1 billion km/h).

But, if one day, technology permits us to send a human into the future by traveling at near-light speed, would the traveler be able to employ time dilation to return to the past and report her findings?“Interstellar travel at near to the speed of light may be possible,” says Dr. Jaymie Matthews, an astrophysics professor at the University of British Columbia. “However, this voyage is only one way — into the future, not back in time.”

Is it true that we will never return to the past since we can't use time dilation? Possibly not. Einstein postulated that a sort of wormhole called an Einstein-Rosen bridge may be used to travel back in time. Wormholes are hypothetical portions of spacetime that are distorted so that they connect two places in space.

If this bridge in space was stable enough, Einstein's calculations showed that it could theoretically connect two places in time instead. “Right now, even an Einstein-Rosen bridge can't be utilized to travel back in time because it doesn't live long enough — it's not stable,” Matthews argues.

“Even if it were stable, it would necessitate other physics, which we lack. Hypothetical particles and states of matter with "abnormal" physical features, such as a particle with a negative mass that would defy established physical principles. That's why "wormholes" only exist in science fiction."

A recent study from the University of Queensland may hold the key to solving this perplexing puzzle. The researchers show that paradox-free time travel is achievable in this work, demonstrating that the cosmos will self-correct to prevent paradoxes. If this is true, we would never be able to change events in the past to create a new future, even if we could travel back in time.

While these discoveries are fascinating, there appears to be further evidence that, while time dilation allows us to glimpse the future, we will never be able to travel back in time.“The clearest evidence we have that time travel [to the past] is not conceivable, and never will be, is that we have not been invaded by hordes of visitors from the future,” said the late Stephen Hawking in his book Black Holes and Baby Universes.