The warp drive, one of Star Trek's hallmark inventions, could someday become science instead of science fiction.
Some physicists say the faster-than-light travel technology may one day enable humans to jet between stars for weekend getaways. Clearly it won't be an easy task. The science is complex, but not strictly impossible, according to some researchers studying how to make it happen.
The trick seems to be to find some other means of propulsion besides rockets, which would never be able to accelerate a ship to velocities faster than that of light, the fundamental speed limit set by Einstein's general theory of relativity.
Luckily for us, this speed limit only applies within space-time (the continuum of three dimensions of space plus one of time that we live in). While any given object can't travel faster than light speed within space-time, theory holds, perhaps space-time itself could travel.
"The idea is that you take a chunk of space-time and move it," said Marc Millis, former head of NASA's Breakthrough Propulsion Physics Project. "The vehicle inside that bubble thinks that it's not moving at all. It's the space-time that's moving."
One reason this idea seems credible is that scientists think it may already have happened. Some models suggest that space-time expanded at a rate faster than light speed during a period of rapid inflation shortly after the Big Bang. "If it could do it for the Big Bang, why not for our space drives?" Millis said.
To make the technique feasible, scientists will have to think of some creative new means of propulsion to move space-time rather than a spaceship.
According to General Relativity, any concentration of mass or energy warps space-time around it (by this reasoning, gravity is simply the curvature of space-time that causes smaller masses to fall inward toward larger masses).
So perhaps some unique geometry of mass or exotic form of energy can manipulate a bubble of space-time so that it moves faster than light-speed, and carries any objects within it along for the ride.
"If we find some way to alter the properties of space-time in an imbalanced fashion, so behind the spacecraft it's doing one thing and in front of it it's doing something else, will then space-time push on the craft and move it?" Millis said. This idea was first proposed in 1994 by physicist Miguel Alcubierre.
In the lab
Already some studies have claimed to find possible signatures of moving space-time. For example, scientists rotated super-cold rings in a lab. They found that still gyroscopes placed above the rings seem to think they themselves are rotating simply because of the presence of the spinning rings beneath. The researchers postulated that the ultra-cold rings were somehow dragging space-time, and the gyroscope was detecting the effect.
Other studies found that the region between two parallel uncharged metal plates seems to have less energy than the surrounding space. Scientists have termed this a kind of "negative energy," which might be just the thing needed to move space-time.
The catch is that massive amounts of this negative energy would probably be required to warp space-time enough to transport a bubble faster than light speed. Huge breakthroughs will be needed not just in propulsion but in energy. Some experts think harnessing the mysterious force called dark energy — thought to power the acceleration of the universe's expansion — could provide the key.
Even though it's a far cry between these preliminary lab results and actual warp drives, some physicists are optimistic.
"We still don't even know if those things are possible or impossible, but at least we've progressed far enough to where there are things that we can actually research to chip away at the unknowns," Millis told SPACE.com. "Even if they turn out to be impossible, by asking these questions, we're likely to discover things that otherwise we might overlook."