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We’ve all seen the exact same movie trope. A crazy-haired scientist wires a glowing dashboard into a DeLorean or a phone booth, hammers a giant red button, and vanishes in a flash of lightning to the year 1955. Or maybe the year 3000.
Time travel is the ultimate, undefeated fantasy. Everyone has that one mistake they want to undo, or that one future lottery ticket they want to peek at.
But is it just a Hollywood fantasy? If you walk into a university and ask a theoretical physicist if time travel is possible, their answer is going to completely throw you off: Yeah. It is.
In fact, you are time traveling right now. Forward. At a strict, boring rate of one second per second. But manipulating that speed? Leaping into the future or stepping into the past? That is where the physics get unbelievably weird. Let’s break down what Albert Einstein actually said about hacking the timeline.
Fast Forward: Traveling to the Future
If you want to travel to the future, throw away the blueprints for the glowing machine. You don’t need magic. You just need to go really, really, really fast.
Back in 1905, Einstein dropped the Theory of Special Relativity and broke everybody’s brain. He proved that time isn’t a massive ticking clock that everyone agrees on. Time is relative. The faster you move through space, the slower you move through time compared to a guy just standing still. They call this Time Dilation.
Picture this: you jump into a rocket ship and blast off at 99% the speed of light. You fly around for what feels like 5 years to you. But when you land back on Earth? 50 years have passed for everyone else. Your friends are old. You haven’t aged a bit. Boom. You just time-traveled 45 years into the future.
And this isn’t just a whiteboard theory. It’s a proven fact. Astronauts orbiting Earth on the International Space Station at 17,500 mph actually age a tiny, tiny fraction of a second slower than the rest of us. NASA’s Physics pages have some incredible, easy-to-read breakdowns on this if you want the exact math.
If relativity scrambles your brain, do yourself a massive favor and grab Astrophysics for People in a Hurry by Neil deGrasse Tyson. It explains the wildest concepts in space without making you feel stupid.
The Heavy Alternative: Gravity
Einstein also figured out that massive gravity crushes time (General Relativity). If you were crazy enough to park a spaceship near the edge of a supermassive black hole—where the gravity is violently intense—time would crawl to a halt for you. Hang out there for a couple of hours, fly back to Earth, and you might find that decades have passed. (Yes, Christopher Nolan basically built the entire movie Interstellar around this exact concept!)
Hitting Rewind: The Big Mess
Okay, so the future is just a speed problem. But what about traveling backward? What if I want to go hang out with a T-Rex?
This is where the physicists start shaking their heads. Traveling to the past completely shatters the law of cause and effect. It creates paradoxes that break the universe.
The most famous one? The Grandfather Paradox. You travel back in time and accidentally run over your own grandfather before he meets your grandmother. Because of that, you are never born. But wait—if you were never born, how did you travel back in time to run him over?
Some wild mathematical models hint that if you could somehow stabilize a “Wormhole” (a shortcut tunnel through spacetime), you might be able to loop backward. But keeping that tunnel open requires something called “negative energy,” which we aren’t entirely sure even exists. The geniuses over at the Perimeter Institute for Theoretical Physics publish some incredibly trippy research on wormholes if you want to fall down a rabbit hole.
10 Riddles to Bend Space and Time
Can you solve these without jumping timelines?
1. The Riddle: I fly without wings. I cry without eyes. Whenever I pass, everybody dies. What am I?
The Answer: Time.
2. The Riddle: I am the genius with the crazy hair who proved that time slows down when you speed up. Who am I?
The Answer: Albert Einstein.
3. The Riddle: I am the absolute speed limit of the universe. Cops can’t pull me over. What am I?
The Answer: The speed of light.
4. The Riddle: I am a theoretical tunnel straight through the fabric of space and time. What am I?
The Answer: A wormhole.
5. The Riddle: I am the mind-bending problem where a time traveler accidentally stops themselves from being born. What am I?
The Answer: The Grandfather Paradox.
6. The Riddle: I am the heavy, invisible force that glues you to the ground, but I also have the power to slow time. What am I?
The Answer: Gravity.
7. The Riddle: I never was, and I am always to be. No one has ever seen me, nor ever will. What am I?
The Answer: Tomorrow (The Future).
8. The Riddle: I am an iconic 1980s car that needs to hit exactly 88 miles per hour to jump decades. What am I?
The Answer: The DeLorean.
9. The Riddle: I am the scientific term for time slowing down for a moving rocket compared to a standing man. What am I?
The Answer: Time Dilation.
10. The Riddle: I have hands but cannot hold a thing. I have a face but cannot smile. What am I?
The Answer: A clock.
The Wrap Up
Look, building a time machine in your garage to go back and buy cheap Bitcoin isn’t happening. But you are absolutely a time traveler. When you look at the stars at night, you are literally looking into the past, because that starlight took millions of years to reach your eyes. And just by walking down the street, you are warping the flow of your own future.
If you want to keep breaking your brain with theoretical physics, bookmark Scientific American and Physics Today. The universe is way weirder than the movies.