Physics says time travel is possible, but probably not in the way you're thinking.
Is Time Travel Possible?
In short, yes—you’re already doing it, steadily moving forward in time at a rate of one second per second. Whether you’re observing paint dry or wishing for more time with an out-of-town friend, you’re continuously advancing through time at a consistent pace.
However, this isn’t the type of time travel that has inspired countless science fiction stories or led to a genre with more than 400 titles listed under “Movies about Time Travel” on Wikipedia. In popular series like “Doctor Who,” “Star Trek,” and “Back to the Future,” characters enter fantastical machines to journey into the past or leap into the future. After traveling through time, they often face the consequences of altering the past or present based on knowledge from the future, which ties into concepts of parallel universes or alternate timelines.
While the idea of altering the past or glimpsing the future is intriguing to many, no one has ever demonstrated the kind of bidirectional time travel seen in science fiction, nor proposed a method to send someone across significant periods of time without catastrophic consequences. As physicist Stephen Hawking humorously noted in his book “Black Holes and Baby Universes” (Bantam, 1994), “The best evidence we have that time travel is not possible, and never will be, is that we have not been invaded by hordes of tourists from the future.”
That said, science does support some aspects of time manipulation. Albert Einstein’s theory of special relativity, for instance, suggests that time is relative and varies depending on the observer’s motion. An individual traveling near the speed of light experiences time more slowly compared to someone stationary. This phenomenon was demonstrated when astronaut Scott Kelly, after spending a year in orbit, aged slightly less than his twin brother who remained on Earth.
There are other scientific theories surrounding time travel, particularly involving wormholes, black holes, and string theory. However, for now, the concept of time travel remains largely within the realm of an ever-expanding collection of science fiction books, movies, TV shows, comics, video games, and more.
(twin brothers Mark and Scott Kelly who are both astronauts have done remarkable study on how space effects human body)
SCIENCE FICTION
Time travel has been a central theme in fiction for centuries. Even as far back as the "Mahabharata," an ancient Sanskrit epic from around 400 B.C., people have envisioned the possibility of altering the flow of time, according to Lisa Yaszek, a professor specializing in science fiction studies at the Georgia Institute of Technology.
In each story involving time travel, a unique version of space-time is created, often skimming over scientific challenges and paradoxes to meet the demands of the narrative. Some works, like Christopher Nolan’s 2014 film "Interstellar," incorporate elements of scientific theory. In the movie, Matthew McConaughey's character spends several hours on a planet near a supermassive black hole, where the effects of time dilation mean that what feels like hours to him equates to decades passing for those on Earth.
Other portrayals of time travel take a more imaginative route, such as in the television series "Doctor Who." The show centers on the Doctor, an alien "Time Lord" who travels through time in a ship disguised as a blue British police box. The Doctor famously explains that, contrary to the usual perception of time as a straightforward sequence from cause to effect, it’s more of a "big ball of wibbly-wobbly, timey-wimey stuff" from a non-linear perspective.
Popular franchises like "Star Trek" and comic book universes such as DC and Marvel frequently revisit and explore the concept of time travel in their narratives.
ALBERT EINSTEIN'S THEORY
In 1905, Einstein introduced his theory of special relativity, which, along with his later theory of general relativity, has become a cornerstone of modern physics. Special relativity explores how space and time relate to each other for objects moving at constant speeds in a straight line.
The basic principles of this theory are surprisingly straightforward. Firstly, all measurements are relative to something else—there is no universal frame of reference. Secondly, the speed of light remains constant, regardless of the observer’s location or movement. Lastly, nothing can travel faster than light.
These principles lead to the possibility of real-world time travel. An observer moving at a high speed will experience time more slowly than someone who isn’t moving at such velocities.
While we don’t send humans close to the speed of light, astronauts aboard the International Space Station (ISS) do orbit the Earth at about 17,500 mph (28,160 km/h). This has tangible effects on time. For instance, astronaut Scott Kelly, who was born after his twin brother Mark Kelly, has spent 520 days in space compared to Mark’s 54 days. Due to the differences in the speed at which they experienced time, the age gap between them has actually increased.
"So, whereas I used to be just 6 minutes older, now I am 6 minutes and 5 milliseconds older," Mark Kelly remarked during a panel discussion on July 12, 2020, as previously reported by Space.com. "Now I've got that over his head."
GENERAL RELATIVITY AND GPS TIME TRAVEL
The impact
of low Earth orbit on an astronaut's lifespan is minimal—more suitable for
sibling jokes than for extending life or traveling far into the future.
However, the time dilation between people on Earth and GPS satellites orbiting
in space does have a meaningful effect.
The Global Positioning System (GPS) helps determine precise locations by communicating with a network of satellites in high Earth orbit. These satellites orbit the Earth at a distance of 12,500 miles (20,100 kilometers), traveling at 8,700 mph (14,000 km/h).
While it might take over seven years for a GPS satellite's atomic clock to drift out of sync with an Earth-based clock by more than the duration of a blink, these microsecond adjustments are crucial. The accuracy of modern GPS technology depends on them. Thanks to this precision, your phone can pinpoint your exact location in both space and time with remarkable accuracy.
CAN WORMHOLES TAKE US BACK IN TIME?
According to NASA, general relativity might offer potential ways for time travel into the past, but these methods are far from simple. One such possibility involves wormholes—hypothetical tunnels in the fabric of space-time that could connect different points in time or space. Also known as Einstein-Rosen bridges or white holes (in contrast to black holes), wormholes are a popular concept in science fiction. However, despite their prominence in theoretical discussions, no wormholes have ever been observed in reality.
As Stephen Hsu, a theoretical physics professor at the University of Oregon, mentioned to Live Science, "The whole thing is very hypothetical at this point. No one thinks we're going to find a wormhole anytime soon."
Primordial wormholes are theorized to have incredibly small openings, about 10^-34 inches (10^-33 centimeters) wide. Previously, these wormholes were thought to be too unstable for anything to pass through. However, a study reported by Live Science challenges this idea.
Physicist Pascal Koiran proposed that wormholes could indeed serve as functional shortcuts through space-time. Unlike earlier studies that used the Schwarzschild metric, Koiran employed the Eddington-Finkelstein metric, which allowed him to successfully trace the path of a particle through a hypothetical wormhole.
Koiran's findings were first shared in October 2021 on the preprint platform arXiv, and later published in the *Journal of Modern Physics D*.
ALTERNATE TIME TRAVEL THEORIES
Although Einstein's theories suggest that time travel may be challenging, some researchers have proposed alternative approaches that could theoretically enable movement through time. However, these theories all share a significant drawback: it seems highly unlikely that a person could endure the intense gravitational forces involved in any of these methods.
Infinite cylinder theory
Astronomer Frank Tipler proposed a concept, often referred to as the Tipler Cylinder, where one could take matter equivalent to 10 times the mass of the sun and compress it into an extremely long and dense cylinder. The Anderson Institute, an organization focused on time travel research, humorously compared the cylinder to "a black hole that has passed through a spaghetti factory."
By spinning this "spaghetti-like" black hole at billions of revolutions per minute, a nearby spaceship, if it followed a very precise spiral path around the cylinder, could theoretically travel back in time on what is known as a "closed, time-like curve," according to the Anderson Institute.
The main issue, however, is that for the Tipler Cylinder to work, the cylinder would need to be infinitely long or composed of a type of matter that is currently unknown. For now, creating such an endless interstellar pasta remains far beyond our capabilities.
Time
donuts
Theoretical physicist Amos Ori from the
Technion-Israel Institute of Technology in Haifa, Israel, proposed a time
machine model based on the concept of curved space-time. His design involves a
donut-shaped vacuum encircled by a sphere of normal matter.
BIBLIOGRAPHY
1.https://www.space.com/21675-time-travel.html
2.https://youtu.be/bdV2agMRl1w?si=Uc2W_d3IFiXLD8Ri (for image)
3.https://www.imdb.com/title/tt0060028/. (For images)
AUTHOR
Himanshu( Third year ,
Physics (honours))
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