NASA/Dana Berry/SkyWorks Digital.
Artist's impression of a supermassive black hole consuming matter from its accretion disk.
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.
Although we have a pretty good idea that our galaxy contains a supermassive black hole at its core, there could be another — albeit rather exotic — explanation for our observations of Sagittarius A*. It might be a wormhole.
This is according to two researchers who explore the possibility in a new paper submitted to the arXiv pre-print service. Although their work is purely theoretical, Zilong Li and Cosimo Bambi of Fudan University in Shanghai have identified a specific emission signature surrounding their hypothetical wormhole, a signature that may be detected by a sophisticated instrument that will soon be attached to one of the world’s most powerful telescopes.
Sagittarius A* (or Sgr A*) is a region in the Milky Way’s core that generates powerful radio waves and astronomers have long suspected that it is the location of a black hole approximately 4 million times the mass of our sun. It wasn’t until astronomers were able to track stars orbiting close to the suspected black hole’s event horizon, however, that the supermassive black hole was confirmed to be there.
But supermassive black holes are a conundrum.
Now we know what signature our supermassive black hole generates, astronomers have discovered that the majority of other galaxies also possess supermassive black holes in their cores. Even when looking into the furthest cosmological distances at the youngest known galaxies, they also appear to host these black hole behemoths.
For a black hole to gain so much mass, it’s logical to think they need lots of time to pile on the mass — eating interstellar gas, stars and other galactic material. But to explain the earliest supermassive black holes in the youngest galaxies, there had to be some as-yet to be understood rapid growth mechanism.
According to Li and Bambi, however, to explain our observations of Sgr A* and other galaxies’ cores, a primordial consequence of Einstein’s general theory of relativity may be called into play instead, thereby sidestepping the puzzle of how supermassive black holes grew so big so quickly.
“While of exotic nature, at least some kinds of primordial WHs (wormholes) can be viable candidates to explain the supermassive objects at the center of galaxies,” they write. “These objects have no solid surface, and therefore they may mimic the presence of an event horizon. They would have been produced in the early Universe and grown during inflation, so they could explain their presence even at very high redshift.”
High redshift galaxies are the youngest galaxies we can observe; where the galactic light has traveled billions of light-years, with frequencies shifted to the reddest part of the electromagnetic spectrum.
The type of wormhole that can mimic a black hole could only have been formed during the Big Bang, exerting a mass millions of times our sun’s mass, possibly explaining why the earliest galaxies appear to have supermassive black holes in their cores; they may not be black holes at all, they could in fact be gargantuan wormholes, linking disparate regions of space and time. (Though whether they can be traversed would likely remain a mystery.)
This may sound like some theoretical fun and games bordering on science fiction, but Li and Bambi have identified a powerful new instrument that could be used to differentiate emissions from space plasma surrounding the Sgr A* black hole or hypothetical wormhole.
GRAVITY will soon be installed at the ESO’s Very Large Telescope (VLT) in the Atacama Desert in Chile and will be used to observe the galactic center with unprecedented precision. The researchers hope to analyze emission data from energized gases (or plasma) that could be found around the object inside Sgr A*. Should the object in fact be a wormhole, that plasma will generate a very different signature as the hypothetical wormhole will be physically smaller than a supermassive black hole.
By modeling a hot blob of plasma trapped in the warped spacetime surrounding a black hole and a wormhole, Li and Bambi noticed two very different emission signatures that both cases will generate. A wormhole would generate a “very narrow emission line,” whereas a black hole would have spectra that is “broad and skewed as a result of special and general relativistic effects,” they write.
It is rare that such exotic theories could be supported or disproved by an instrument that will be commissioned within a couple of years, but it will be very exciting to see whether the plasma emissions around the object in Sgr A* are more black hole-like or wormhole-like. And although the chances are slim, if the latter is detected, it could re-write our understanding of the Cosmos.