Time Travel: Fiction or reality of the future? (1)
Humans fantasize about various things. It might be the existence of parallel universes, or aliens, or maybe finding out their doppelganger while going out to buy groceries! Science fiction movies surely make us think of so many possibilities that we may be unaware of. One of the most exciting and sought-out topics among these is the possibility of time travel. It’s a theory that physicists and philosophers having been debating and researching for the last century.
What if we could travel between different points of time, traveling forward to the future or backward to the past as easily as pressing buttons on a TV remote. Franchises ranging from "Star Trek", "Back to the Future" to "Doctor Who" have seen people get in a time travel machine of some kind and go in the past or future, ready to begin their adventurous journey. Each of these science fiction movies comes with its own time travel theories.
We all have some regretful experiences or decisions in our lives, so the concept of turning back time is an appealing one. Who would not want to fix the past, or obliterate an unfortunate historical event that adversely impacted humanity (like the unfortunate event of nuclear bombing at Hiroshima and that WW I and II altogether)? Or for more future-focused people, how about traveling to the future to see events that they could not have experienced in their whole lives - such as humans meeting with aliens or the invention of a new habitable planet?
The reality, however, seems to be much more complicated. The possibility of time travel seems to be a myth to many scientists. Some even say that the results of the discovery of time travel would be catastrophic to mankind. Let us start by understanding different concepts involved in time travel.
Time unfolded:
What is time?
While most people think of time as a constant for everyone and only moves forward direction, it was proved by the world-renowned physicist Albert Einstein time is relative - it can vary for different spectators depending according to their frame of reference. He considered time as the "fourth dimension." Space is termed as a three-dimensional entity, which provides a traveler with coordinates length, breadth, and height - showing location. Time provides an additional coordinate - direction.
Einstein's theory of special relativity states that time speeds up or slows down depending on how fast we are moving relative to some reference. On approaching the speed of light, a person inside a spaceship would age at a much slower pace than some other person born on the same. This effect, known as time dilation, means astronauts are time travelers, as they return to earth marginally less in age than their identical twins that remain on the planet. Also, under Einstein's theory of general relativity, time can be bent by gravity. A more vivid example of time dilation can be seen in the movie “Interstellar” when Cooper and his crew land on “Miller” planet. The nearby black hole causes extreme gravitational field on the planet. Because of this, time slows dramatically for the crew, making one hour on the surface equal to seven years on Earth.
In order to portray a geometric model of the space-time continuum, we can define a coordinate system, which consists of an additional time dimension along with the 3 spatial dimensions. Since it is nearly impossible for us to visualize 4-dimensions, it can be plotted with time on the y-axis and space on the x-axis, also known as the “Minkowski space-time”. Matter bends space-time fabric, which causes other bodies to feel the pull of gravity.
So why can’t we take such huge leaps forward in time yet?
The reason behind this comes down to velocity. We would either need to send the traveler flying into space at a speed close to the speed of light (approximately 3*10^8 m/s) or take benefit of the intense gravitational acceleration caused by black holes in order to generate such large time-travel age differences between them and people living on earth. With our current technology, is all we can manage is jumping a few micro-seconds into the future.
But if we are able to develop such advanced technology that one day can launch a human into space at speed close to the speed of light, would it be possible for him to return to the past using time dilation and report his findings? “Interstellar travel reaching close to the speed of light might be possible, but this voyage is one way – into the future, not back to the past.” says Dr. Jaymie Matthews, professor of astrophysics at the University of British Columbia.
If we cannot use the concept of time dilation to come back to the past, does this mean that we will not be able to access it forever? Maybe not. Einstein suggested that through wormholes, time travel into the past could be made possible. These are theoretical areas of spacetime that connect two distant points in space like a bridge.
It was proposed by the equations of Einstein that this bridge in space could [theoretically] connect two points in spacetime if it were stable enough. An astronaut who enters a wormhole in the Andromeda Galaxy in the year 5000 might find himself coming out from the other end in the milky-way galaxy, in the year 2000. But here is a problem, while there is sufficient evidence of the existence of black holes, the existence of wormholes is just speculation and can’t be proved by the physics that we know today. It needs some entities to exist, such as negative mass and negative energy, which are possible to define mathematically but are not present in reality.
Other than that, time-travel to the past leads to several paradoxes, like “Grandfather’s paradox” in which if you travel through time and kill your grandfather when he was young, it means that your father will not be born which finally means that you will not be born. And hence, you cannot travel back in time and kill your grandfather in the first place. Several other paradoxes come into the picture when we discuss the possibility of time travel.
So, what can we conclude?
While time travel does not seem to be possible using the current physical laws with no possibility of a human to survive traveling through black holes and wormholes, a lot of research is going on in this field. Advances in quantum mechanics could perhaps help us in understanding these paradoxes and their possible explanations.
For now, we can just see them happening in science fiction movies, books, and possibly in our minds. There was a time when the earth was considered to be flat (but it is obviously not!), so there are high chances we might be able to solve the time-travel mystery in the future. Meanwhile, we can just speculate.
Thanks for reading.
Comments and suggestions are always welcomed😊
Godspeed!
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