Is Time Travel Possible?

Time is a point of time that is measured in hours, minutes, and even periods while travel is moving from one point or place to another, typically over a distance of something in three points. Therefore time travel is the movement between different points in space by an object or a person. In time travel, one can go there before or after the actual time. But time travel to the past is not possible in day-to-day activities, it is mostly seen in movies in fiction form where people travel to the future (Lobo, M. P. (2019).

As people understand the nature of time, this makes people understand that past is different from the future. The future always seems to have a lot of possibilities in that, people have time to plan and imagine that all the imaginations will come to pass. Past is always related to something that already happened hence it cannot be reversed. It can either lead to regrets or also show some signs of contentment. Now, time is considered as a flowing river that cannot flow backward, hence time travel for the future is possible than that of the past (Ragno 2020).

Real-life time travel occurs through time dilation, a property of Einstein’s special relativity. Einstein was the first to realize that time is not constant, as previously believed, but instead slows down as you move faster through space.

As part of his theory, Einstein re-envisioned space itself. He coined the phrase “spacetime,” fusing the three dimensions of space and one dimension of time into a single term. Instead of treating space as a flat and rigid place that holds all the objects in the universe, Einstein thought of it as curved and malleable, able to form gravitational dips around masses that pull other objects in, just as a bowling ball placed in the center of a trampoline would cause any smaller object placed on the trampoline to slide towards the center.

The closer an object gets to the center of the dip, the faster it accelerates. The center of the Earth’s gravitational dip is located at the Earth’s core, where gravitational acceleration is strongest. According to Einstein’s theory, that time moves more slowly as you move faster through space, the closer an object is to the center of the Earth, the slower time moves for that object.

This effect could be seen in GPS satellites, which orbit 20,200 kilometers above the Earth’s surface. These satellites have highly precise clocks onboard that gain an average of 38 microseconds per day due to time dilation. While this time gain seems insignificant, GPS satellites rely on their onboard clocks to maintain precise global positioning. Running 38 microseconds fast would result in a positioning error of nearly 10 kilometers, an error that would increase daily if the time difference were not constantly corrected.

For humanity to send a traveler years into the future, we would either have to take advantage of the intense gravitational acceleration caused by black holes or send the traveler rocketing into space at close to the speed of light (about 1 billion km/h). With our current technology, jumping a few microseconds into the future is all humans can manage.

But if technology one day allows us to send a human into the future by traveling close to the speed of light, would there be any way for the traveler to use time dilation to return to the past and report her findings? “Interstellar travel reaching close to the speed of light might be possible,” says Dr. Jaymie Matthews, professor of astrophysics at the University of British Columbia, “but this voyage is one way – into the future, not back to the past.”

As the late Stephen Hawking said in his book Black Holes and Baby Universes, “The best evidence we have that time travel, into the past, is not possible, and never will be, is that we have not been invaded by hordes of tourists from the future.”

“The mechanism for traveling into the distant future is to use the time-dilation effect of Special Relativity, which states that a moving clock appears to tick more slowly the closer it approaches the speed of light. This effect, which has been overwhelmingly supported by experimental tests, applies to all types of clocks, including biological aging.

“Time travel into the past, which is what people usually mean by time travel, is a much more uncertain proposition. There are many solutions to Einstein’s equations of General Relativity that allow a person to follow a timeline that would result in her or him encountering herself, or her grandmother, at an earlier time. The problem is deciding whether these solutions represent situations that could occur in the real universe, or whether they are mere mathematical oddities incompatible with known physics. No experiment or observation has ever indicated that time travel is occurring in our universe. Much work has been done by theoretical physicists in the past decade to try to determine whether, in a universe that is initially without time travel, one can build a time machine, in other words, if it is possible to manipulate matter and the geometry of space-time in such a way as to create new paths that circle back in time.

“How could one build a time machine? The simplest way currently being discussed is to take a wormhole (a tunnel connecting spatially separated regions of space-time) and give one mouth of the wormhole a substantial velocity concerning the other. Passage through the wormhole would then allow travel to the past.

“Even if we had a wormhole, would nature allow us to convert it into a time machine? Stephen Hawking has formulated a “Chronology Protection Conjecture,” which states that the laws of nature prevent the creation of a time machine. At the moment, however, this is just a conjecture, not proven.

“Theoretical physicists have studied various aspects of physics to determine whether this law or that might protect chronology and forbid the building of a time machine. In all the searching, however, only one bit of physics has been found that might prohibit using a wormhole to travel through time. In 1982, Deborah A. Konkowski of the U.S. Naval Academy and I showed that the energy in the vacuum state of a massless quantized field (such as the photon) would grow without bound as a time machine is being turned on, effectively preventing it from being used. Later studies by Hawking and Kip S. Thorne of Caltech have shown that it is unclear whether the growing energy would change the geometry of space-time rapidly enough to stop the operation of the time machine. Recent work by Tsunefumi Tanaka of Montana State University and myself, along with independent research by David Boulware of the University of Washington, has shown that the energy in the vacuum state of a field having mass (such as the electron) does not grow to unbounded levels; this finding indicates there may be a way to engineer the particle physics to allow a time machine to work (Voigt & Saba 2019).

“Perhaps the biggest surprise of the work of the past decade is that it is not obvious that the laws of physics forbid time travel. It is increasingly clear that the question may not be settled until scientists develop an adequate theory of quantum (Rupasinghe, 2017).

References

Lobo, M. P. (2019). Time Travel: coexistence of past, present, and future?.

Ragno, A. G. (2020). Time-Travel: Physical Impossibility and Theoretical Interest.

Rupasinghe, R. (2017). The Philosophy and Physics of Time Travel: The Possibility of Time Travel.

Voigt, A. H., & Saba, S. (2019). Back to the Future: Is Time Travel Possible in Entrainment Mapping?

 

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