By Divita Narula
(Photo by Andy Beales on Unsplash)
Time travel is something thought to only exist in science fiction and ancient mythology, something only considered as a wish of many and probably not a reality. There are, however, numerous theories developed by some of the greatest minds in humankind that prove time travel as a possibility, such as the theory of special and general relativity and the theory of wormholes.
Einstein’s idea of special relativity in time travel is that time flows relative to how fast you’re moving. By moving faster, time slows, and vice versa. His idea of general relativity in time works similarly, but instead of movement, gravity affects time in that the more forceful the gravity is, the slower time moves. According to Dave Goldberg, a cosmologist at Drexel University, “If the person who was near the black hole returned to this planet, they would have effectively travelled to the future.” There are, however, problems with Einstein’s theory, namely that his idea of relative spacetime is in fact, false.
Although we may always be travelling through time, time travel generally refers to, “the possibility of changing the rate at which we travel into the future, or completely reversing it so that we travel into the past” (“Time Travel – Exactly What Is Time?”). Time travel is impossible in Newtonian (absolute time) and special relativity, but still remains a possibility in general relativity, as has been extensively researched by Albert Einstein and many others. It usually means that a person’s mind and body remains the same, but their location in time changes.
Time travel to the future is relatively easy to understand, but there are significant issues in trying to travel back in time. One issue would be a phenomenon scientists know as “closed timelike curves”. A closed timelike curve “describes the trajectory of a hypothetical observer that, while always travelling forward in time from their own perspective, at some point finds themselves at the same place and time where they started, creating a loop” (Higgins and Scoles). This means that when a hypothetical observer goes back in time and then moves forward in time in their own perspective, they will find themselves back at the point at which they started, from which they’d go back in time again, which would keep the observer in an infinite loop. Another issue would be known as the Grandfather paradox, in which if you were to go back in time and kill your grandfather before he sired your father. This would be a problem because then how did you go back in time and kill him in the first place?
Another possibility for time travel is wormholes. Though they’ve never been found in space, wormholes have been described in the solutions to numerous physics equations, like the equations in Einstein’s theory of space-time and general relativity. There is much debate in the belief of a wormhole’s existence, however, because gravity influences everything in space, which would include wormholes if they exist. The problem, however, is that a wormhole would collapse on itself due to its gravity, unless there is a negative energy counteracting the pull of gravity and stabilising the wormhole. But scientists have found so far that negative energy only exists in quantities much too small to counteract the force of gravity on and from a wormhole. Wormholes still haven’t been considered a part of mainstream science, but the same was true for black holes, so there’s a possibility for proof of a wormhole’s existence.
There are numerous other theories that make the possibility of time travel quite real, but as of now, debate still goes strong among numerous scientists, and it may be decades or even centuries before time travel is proven and a substantial concept.
References
Higgins, Nick, and Sarah Scoles. “Is Time Travel Possible?” Scientific American, 26 April 2023, https://www.scientificamerican.com/article/is-time-travel-possible/. Accessed 23 October 2023.
“Time Travel – Exactly What Is Time?” Exactly What Is Time?, https://www.exactlywhatistime.com/physics-of-time/time-travel/. Accessed 7 November 2023.
Stojkovic, Dejan. “What are wormholes? An astrophysicist explains these shortcuts through space-time.” Astronomy Magazine, 31 October 2023, https://www.astronomy.com/science/what-are-wormholes-an-astrophysicist-explains-these-shortcuts-through-space-time/. Accessed 11 November 2023.
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