Scientific fact versus science fiction

Time travel, an ancient fascination in science fiction, remains a complex and unsolved concept in science. The second law of thermodynamics states that time can only move forward, while Einstein’s theory of relativity shows the relationship of time to speed. Theoretical ideas such as wormholes offer potential routes, but practical challenges and paradoxes, such as the “grandfather paradox,” further complicate the feasibility of actual time travel.

Would it be possible for time travel to happen?

Have you ever dreamed of traveling through time like characters do in science fiction movies? For centuries, the concept of time travel has captured people’s imaginations. Time travel is the concept of moving between different points in time, just as you move between different places. In movies, you may have seen characters using special machines, magical devices, or even jumping into a futuristic car to travel backwards or forwards in time.

But is this just a fun idea for movies, or could it actually happen?

The science behind time travel

The question of whether time is reversible remains one of the biggest unsolved questions in science. If the universe follows Laws of thermodynamics, may not be possible. The second law of thermodynamics states that things in the universe either stay the same or become more disordered over time.

It’s a bit like saying you can’t crack eggs after they’re cooked. According to this law, the universe cannot completely return to what it was before. Time can only move forward, like a one-way street.

Time is relative

However, physicist Albert Einstein’s theory of special relativity suggests that time passes at different rates for different people. A person is riding fast on a spaceship moving at close to the speed of light – 671 million miles per hour! -He will live slower than anyone on Earth.

People have not yet built spaceships that can move at speeds close to the speed of light, but astronauts who visit space International Space Station It orbits the Earth at speeds approaching 17,500 miles per hour. Astronaut Scott Kelly spent 520 days on the International Space Station, and as a result has aged slightly more slowly than his twin brother – and fellow astronaut – Mark Kelly. Scott was six minutes younger than his twin brother. Now, because Scott has been traveling much faster than Mark for many days, so is he 6 minutes and 5 milliseconds smaller.


Time is not the same everywhere.

Theoretical possibilities and challenges

Some scientists are exploring other ideas that could theoretically allow time travel. One concept involves wormholes, or virtual tunnels in space that could create shortcuts for journeys across the universe. If someone could build a wormhole and then figure out a way to move one end of it at close to the speed of light — like the hypothetical spaceship mentioned above — the moving end would age more slowly than the fixed end. The person who entered the moving end and exited the wormhole through the fixed end would exit in his past.

However, wormholes remain a theory: scientists have not yet been able to discover them. It also appears that it will be so Incredibly difficult To send humans through a space tunnel to the wormhole.

Paradoxes and failed dinner parties

There are also paradoxes associated with time travel. famous “The grandfather paradox“It is a hypothetical problem that could arise if someone traveled through time and accidentally prevented their ancestors from meeting. This would create a paradox since you were never born, which raises the question: How could you have traveled through time in the first place? It’s a puzzle.” For the mind it adds to the mystery of time travel.

It is known that physicist Stephen Hawking tested the possibility of time travel Host a dinner party Invitations indicating the date, time and coordinates were not sent until after the fact. He hoped that his invitation would be read by someone living in the future, who had the ability to travel through time. But no one showed up.

As is pointed out“The best proof 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.”

James Webb's artist's conception of a space telescope

Artistic rendering of the James Webb Space Telescope. Credit: Northrop Grumman

Telescopes are time machines

Interestingly, astrophysicists armed with powerful telescopes possess a unique form of time travel. When they look at the vast expanse of the universe, they are staring at the past universe. Light from all galaxies and stars takes time to travel, and these rays of light carry information from the distant past. When astrophysicists observe a star or galaxy through a telescope, they do not see it as it exists today, but rather as it existed when light began its journey to Earth millions to billions of years ago.


Telescopes are a kind of time machine, they allow you to look into the past.

NASA’s newest space telescope, the James Webb Space Telescope, is looking at galaxies that formed at the beginning of the Big Bang, about 13.7 billion years ago.

While it’s unlikely that we’ll have time machines like the ones in movies anytime soon, scientists are actively researching and exploring new ideas. But for now, we’ll just have to enjoy the idea of ​​time travel in our favorite books, movies, and dreams.

Written by Addie Ford, Assistant Professor of Astronomy and Astrophysics, University of Maryland, Baltimore County.

Adapted from an article originally published in Conversation.Conversation

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