Top 5 Sci-Fi Time Travel Methods
There is no shortage of time machines in the world of science fiction. You could probably name a bunch of them off the top of your head, from H.G. Wells' iconic creation to such mainstays as Dr. Who's Tardis and Dr. Brown's flux-capacitated DeLorean. But just how many fictional time machines can you explain? In many works of fantasy and science fiction, the time machine is just a magical plot device. No actual science is thrown at the audience. Most of the time, no one asks for any. After all, you're probably not watching Life on Mars or Terminator Salvation for a lesson in theoretical physics. Plus, if you're writing time-traveling fiction, then skipping the science spares you the embarrassment of getting something wrong. Isn't it enough that you described 1997 as being a world full of flying cars and busty android life partners? Let's take a look at five examples of the plausible and ridiculous ways fictional TV and film characters have traveled through time.
5. Superman Spin Control
If we learned anything about the physics of time and space from Richard Donner's 1978 film Superman, it's that if you fly around the Earth really fast, you can reverse its rotation and roll back time. Although physicists agree that space and time are interconnected, you'd be hard-pressed to find anyone who would back the "science" behind reversing planetary rotation to turn back time. Far from saving Lois Lane's life, the feat likely would have caused global chaos. Slam on the brakes in a moving car and everything inside it continues moving forward. Now imagine this scenario on a global scale, only with oceans, mountains and weather systems continuing to surge forward at up to 1,000 miles per hour, depending on your latitude. Way to go, Superman.
Credit: AP Photo
4. The Voyage Home to 1986
The Star Trek universe is full of fantastic ideas: aliens with rippled foreheads, holodecks and more time travel than you can shake a stick at. According to the Star Trek Wiki, 50 episodes of the six TV series featured time travel, as did four of the 11 films. You'd think the space-time continuum would just be circling the drain after all that tinkering. Time paradoxes aside, Star Trek always flirted with real science. Take 1986's Star Trek IV: The Voyage Home, for example. In this film, the crew of the Starship Enterprise send a Klingon Bird-of-Prey vehicle back to the 1980s by sling shotting it around the sun. The Star Trek slingshot method involves using the sun's gravitational pull as an accelerator to reach speeds necessary to travel through time. The premise falls in line with some theories about time travel and Einstein's theory of special relativity. The theory says if time slows the closer you get to the speed of light, then travel into the future -- or the past -- may be possible. One slight problem: faster-than-light travel is physically impossible. Plus, as Lawrence M. Krauss points out in The Physics of Star Trek, the gravitational field near the surface of the sun doesn't produce anywhere near the boost you'd need to go talk to whales in the past.
3. Trekking into a Black Hole
Paradoxical time travel isn't a thing of the past for the Star Trek legacy. The plot of the new film concerns two starships that are sucked into an artificial black hole, sending them 154 years into the past. While the time-travel method employed in Star Trek IV: The Voyage Home depended on a far too weak gravitational slingshot, many physicists believe that a black hole might indeed provide the necessary portal to the past. Anything that crosses a black hole's event horizon heads toward an incredibly tiny point of infinitely compressed matter called a singularity. That's also one of the huge problems with the new Star Trek film's plot: What's to keep the two starships from winding up as one with the singularity? Physicists point to Kerr black holes as a less destructive alternative. These theoretical cosmic phenomena first described by Roy Kerr in the 1960s lack the matter-smashing singularity at the center, potentially making it possible to pass the event horizon and come out the other side -- in another time.
2. Donnie Darko, Creepy Rabbits and Wormholes
The 2001 cult favorite Donnie Darko spends most of its time exploring the possible effects of time-travel paradoxes and tangent universes on its characters, but it also features a portal through time: a wormhole. Also called Einstein-Rosen bridges, these hypothetical cosmic structures might offer a traveler the necessary means of not just taking a shortcut through space, but also through time itself. Einstein's theory of relativity states that mass curves in spacetime. The most common visual example of this concept is that of space depicted as a curved, two-dimensional plane. Think of a racetrack: If you're speeding around a curve, you're bound to that curve, but what if you could forge a new line of track between its two parallel sides? That's the idea behind a wormhole. If a mass on one side of the spacetime curve applies enough force and a mass on the other side of the spacetime curve applies enough force, then the two could meet, creating a tunnel.
Credit: AP Photo
1. Lost on a Time-Traveling Island
If you've watched ABC's "Lost," then you're probably used to things not making a lot of sense. A big reason for this is that the show's mysterious island bounces the characters around through time seamlessly. Seriously, by the end of the series, everyone will be lucky to make it off the island without becoming their own grandparent. Yet "Lost" at least makes an effort to prop up the fiction with a little science. According to blog analysis at Popular Mechanics, the science behind the show's time travel seems to depend on quantum mechanics, a mysterious substance in the ground called "exotic material" and possibly a wormhole. Might this buried, volatile substance produce the necessary energy to manipulate a breach in spacetime? To varying degrees, you could argue that this is all any writer can achieve when crafting a piece of time-travel fiction -- not counting writers who are actually from the future, of course.
British physics superstar Professor Brian Cox has gone on the record to say that time travel is possible. Unfortunately, there’s a huge caveat to his claim: if you were able to achieve this feat, you’d only be able to travel into the future never to return. Why? Traveling into the past is impossible. Possibly.
The idea of mono-directional time travel is a slap in the face for most science fiction storylines, but fortunately for Marty McFly there’s no risk of accidentally sleeping with his mother from 1955 in this scenario. However, zooming around on hovering skateboards in the future is totally plausible. Maybe.
Cox pointed out this little trick of physics at a speech at the British Science Festival while discussing the merits of Doctor Who’s TARDIS, but it probably isn’t news to anyone with a basic knowledge of how Einstein’s theory of Special Relativity works. Although the UK national press seems to think otherwise.
“Can you build a time machine?” said Cox. “The answer is yes.”
Assuming we could build a spaceship that will accelerate an astronaut close to the speed of light, only for them to return a few hours later (in the astronaut’s time frame), through a quirk of relativity it’s possible that thousands of years would have passed on Earth. Therefore, the superfast spaceship will have become a time machine! Want to go further into the future? No problem! Fly the spaceship even faster.
(Keep in mind that it’s still impossible — according to our current knowledge of space, time and good ol’ fashioned physics — to travel faster than the speed of light, but traveling at any fraction of the speed of light is still allowed in physics. The engineering of such a machine, on the other hand, would require some pretty epic propulsion technology behind it.)
“If you go fast, your clock runs slow relative to people who are still. As you approach the speed of light, your clock runs so slow you could come back 10,000 years in the future,” he said.
Cox is basically describing a famous thought experiment taught to university students around the world as the “Twin Paradox.”
Imagine twins, one stays on Earth (Twin A) while the other (Twin B) boards a spaceship and flies off at relativistic speeds. Compared with Twin A’s timeframe, Twin B’s timeframe will slow. If time is running slower for Twin B, then he/she will return to Earth where a lot more time has passed and Twin A has aged significantly more than Twin B. The mechanism behind this is “time dilation” and it has a stronger effect as you travel closer and closer to the speed of light.
So far, Cox has described a time machine (a.k.a. a relativistic spaceship) stuck in fast forward. What would it take to wind back the years and test out the “Grandfather Paradox”? (Warning: If you just so happened to find yourself in the past don’t bother testing out this paradox. Spoiler: It could end very badly for you.)
Well, that would require some pretty fancy and exotic physics.
“In General Relativity, you can do it in principle,” said Cox. “It’s to do with building these things called wormholes; shortcuts through space and time. But most physicists doubt it. Hawking came up with the ‘chronology protection conjecture’ – physics we don’t yet understand that means wormholes are not stable.”
A consequence of some of Einsteins relativity equations predict the existence of wormholes — but they are not traversable wormholes (i.e. you can’t pack your bags and jump into one of these quirks of spacetime), they are short-lived, small scale anomalies. To create a wormhole from science fiction, you’d need an exotic form of matter that can stabilize the mouth of a wormhole using negative energy.
Currently, such a form of matter is pure theory, but if it were to be discovered or manufactured, it would be pretty useful for time travel and, potentially, interstellar travel.
For now, the only conceivable time machine is one that’s stuck in fast forward.