This is the seventh part in an eight-part series on the future of transportation. New articles published every Monday.
Whether it's to colonize new worlds, cavort with the Klingons, or strip-mine unobtainium, many people blithely assume that our descendants will go to the stars.
The well-known problem with this promising scenario is that the stars are immensely far away. Consider this: The fastest vehicle ever piloted by humans was the Apollo 10 command module. In May, 1969, it returned from the moon in a mere three days, plummeting earthward at a blistering seven miles per second. But cosmically speaking, the moon is cheek-by-jowl with our planet. A jaunt to Proxima Centauri, the nearest other star, would take 110,000 years at seven miles per second. You should hope for decent onboard food.
That undoubtedly sounds discouraging for space travel, but you might expect that our space-faring progeny will engineer rockets faster than a Saturn V. However, what they can't do, at least according to Albert Einstein's physics, is break the universe's ultimate speed limit: the speed of light. So interstellar trips will inevitably take many years-at least as measured by the society that launches them. (The crew may age less rapidly thanks to special relativity, but what good is that if everything left behind becomes fossilized ?)
This is a long-standing problem for sci-fi authors who can't afford to slow their stories while protagonists play Sudoku (or just sleep) for decades or centuries between one alien encounter and the next. So writers have peppered their yarns with plausible-sounding schemes for quickly zipping around the galaxy.
Two ever-popular schemes from sci-fi are hyperdrive and warp drive. Both beat the speed of light by manipulating space.
When you shift your rocket into hyperdrive, it makes a lane change and travels through "hyperspace"-an imaginary alternative pathway that comprises a geometric shortcut to your destination. When Han Solo barrels around the empire in Star Wars, he's using technology that is presumably as conventional a transport medium for him as the wheel is for us. Stargate also invokes hyperdrive, as did Babylon 5. A slightly different flavor of hyperspace called jump drivewas used in Battlestar Galactica and Isaac Asimov's Foundation series.
But is hyperspace just hype? Could there really be shortcuts through space that would mimic this sci-fi trope? There might be, and physicists call them wormholes. These possible pathways to other parts of the cosmos seem to work on blackboards. But actually constructing a wormhole and keeping it open long enough to slip a rocket through seems to require either enormous amounts of energy, or the use of something called "exotic matter," a hypothesized material that has negative energy, if you can picture that. To make exotic matter would take incredibly large quantities of ordinary energy, and so this is one material that makes even unobtainium seem prosaic. Given the difficulties with wormholes, both theoretical and practical, it's unclear whether a real-life version of hyperdrive can ever be achieved, so it remains problematic. For sci-fi authors, of course, "problematic" is still better than "forbidden by physics."
The most iconic FTL-travel scheme remains Star Trek's warp drive, which works by distorting space, compressing it in front of the ship, and expanding it behind, thereby bringing you more quickly to your destination without having to cross swords with Einstein. Think about it: As you read these lines, you're moving at tremendous velocity away from galaxies that are billions of light-years distant, but not because you're on a hi-tech rocket. Your apparent speed is actually the universe expanding the space between you and those distant nebulae.
Warp drive works similarly-by enlarging the space behind your spacecraft and collapsing it in front. You literally shrink the distance to your destination, thereby avoiding the inconvenience of building ultra-high-speed rockets.
When Captain Kirk is alerted to troubles in the Gamma Quadrant, he gets Scotty to crank up the Enterprise's cruise control to many times light speed. The Enterprise accomplishes this with matter-antimatter engines, mediated by dilithium crystals (whatever those are). How these manage to warp space is unclear, but then again, so is a lot of what goes on in Star Trek. But if you really want to distort space, you need to tow around either a black hole, or some incredibly massive, rotating objects able to drag space-time around like a teaspoon in a pot of syrup. Neither seems practical.
Faster-than-light travel has been invented because we want to send ourselves into space, and being confined for all time to the solar system is about as satisfying as the idea that you'll never take your Maserati farther than the end of the driveway. But the universe isn't obliged to make all our whims feasible, and FTL travel may be-like the perfect martini-little more than a nice idea.
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