2005-01-01 Discovery Ultra Science Time Travel
Duration: 00:04:53
Transcript
David Deutsch
The laws of physics, as best we know them, don’t forbid us from traveling back into the past. And when the laws of physics don’t forbid something, and we want to do it, then we usually end up doing it. For centuries, people had been writing science fiction stories about traveling to the moon, I mean, for thousands of years. And then all of a sudden, in July of 1969, when Neil Armstrong took his first small step, all those stories were no longer science fiction. They were historical novels, as if by magic fantasy had become true.
Discovery narrator
This is the bridge of the Defiant, known as the toughest little ship in the fleet. And this is where Captain Sisko and Worf and everyone go when they want to both explore and on occasion kick some alien butt, which on occasion has to happen. Could it be that one day starships like this will be driven from fantasy to reality, by technologies that allow us to generate controllable wormholes and to cheat space and time? Now it may be an engineering monstrosity to come up with fields and matter and energies that actually make it happen, but they’re theoretically possible. Someone, somewhere, someday may make it happen. Our challenge now to boldly go where no scientist has gone before, to find ways to make such concepts a reality. We can only imagine how time travel would change our lives. In theory, we could jump into tomorrow and take a cruise through the streets of Las Vegas, then turn back the clock and return to today with the inside knowledge that could win every gambling game in town. Just imagine having the knowledge of what Hitler was going to do and having the ability to warn the world or even to remove the Fuhrer before he got to the surface of the planet. Tempting as it may seem to play hero in the past, there is a catch. It’s called the grandfather paradox. It’s a riddle so perplexing that some scientists believe it proves we’ll never be able to travel into the past. If a time traveler were to go back in time and kill his grandfather before the grandfather had children, wouldn’t that mean that he’d never have been born and therefore couldn’t have traveled back in time to pull the trigger in the first place? If the suggestion sounds mind-boggling, then one possible explanation may seem even more bizarre.
David Deutsch
If you were to travel back in time and change something, you would necessarily end up in another universe. And there’d be no way of getting back to the universe you started in. You’d be trapped.
Discovery narrator
Oxford University physicist David Deutsch believes that is nature’s way of making sure time travelers can’t interfere with what’s already occurred in history. He calls it the multi-universe theory. It offers another loophole, a solution to the grandfather paradox. Deutsch believes there can be unlimited replicas of the world as we know it, all of them with potentially different historical outcomes. According to the theory, when we travel back in time, we enter another universe.
David Deutsch
That universe looks the same as ours, but it follows a different route through history, simply because we’ve entered it and therefore changed it. For instance, you could go back in time and meet another copy of yourself, a copy who didn’t travel in time. And then the two of you would be there in the universe that you’d arrived in, but you’d be missing from the universe that you left. In other words, in some universes, there could be a number of copies of the same person, while in others, there’d be no evidence that that person had ever existed at all.
Discovery narrator
Now could that mean that there are time travelers here now in our world? Visitors from the future who’d been trapped in their travels through history? Some scientists believe such visits may have been crucial to our very existence.
Markdown