Time Travel

Take a step back with this 5-minute video that raises questions about the very existence of time. Does it physically exist, or is it just in our heads? Einstein’s theories of relativity, which explain the behavior of large objects, assert that time is a fundamental property of the universe. But, as physicists try to develop a Theory of Everything that explains the behavior of large and small things, they’ve begun to ponder if time might just be an illusion.

While the author discounts the possibility of traveling to the past, it lays out five hypothetical modes of catapulting into the future: speed, gravity, suspended animation, wormholes, and light. Each has some scientific basis, but none are realistic for humans. Read the article to learn where they offer promise and where they fall short.

These hypothetical distortions in the fabric of spacetime may connect vast distances across or even between universes. While science fiction often portrays them as traversable tunnels, the energy and matter required to keep a wormhole open defy current physical understanding.

This 8-minute video explores how time travel influences the narrative arc of several movies, books and video games, from Harry Potter to A Christmas Carol. (Warning: it contains spoilers!) J.K. Rowling and Charles Dickens set myriad parameters as they’re worldbuilding to avoid paradoxes and create quasi-logical timelines. By drawing diagrams as he’s speaking, the video breaks down how time works in some of popular culture’s most beloved fictional universes.

When renowned theoretical physicist Stephen Hawking did not rule out the possibility of time travel in his posthumous book Brief Answers to the Big Questions, many hopefuls got excited. But, unfortunately for them, Hawking believed that yet-to-be discovered laws of physics will prove time travel impossible. This piece outlines some practicalities about the speed of light and wormholes that lend way to Hawking’s prediction.

In 2009, Hawking hosted a reception but only sent out invitations afterward, hoping that time travelers from the future would attend and prove time travel possible. He later joked it was "experimental evidence" that time travel doesn’t exist.

If something travels faster than the speed of light – 670,000,000 miles per hour – it could hypothetically travel back in time. These notional particles are called tachyons, and their existence would send our understanding of cause and effect into a tailspin. For now, as this article explains, tachyons only live in thought experiments used by physicists to contemplate the boundaries of our universe.

We can travel forward and backward, up and down, side-to-side in space. So, why can’t we travel back in time? Why can we only move forward? This article takes us all the way to the beginning of time – the Big Bang – to explain why time only moves in one direction. And it raises the ominous question: If time has a beginning and only moves in one direction, does it have an end?

If you went back in time and killed your grandfather when he was a child, what would happen to you? One of your parents would never be born, so you wouldn’t be born either. But, if you’re never born, how could you kill your grandfather in the first place? This so-called grandfather paradox is something physicists, philosophers and sci-fi writers constantly ponder. Read the piece to learn how they’ve been trying to reconcile it.

When you look up at a constellation with your naked eye, you’re looking thousands of years into the past. The stars are so far away that it takes their light that long to reach us. Today’s most powerful telescopes, such as the James Webb Space Telescope, can see billions of years into the past. So, as this article suggests, looking through a telescope (or even up at the stars with your own eye) could be considered a form of time travel.