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 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."
Already happened?
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."
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