The idea of a warp drive taking us across large areas of space faster than the speed of light has long fascinated scientists and sci-fi fans alike. While we're still a very long way from jumping any universal speed limits, that doesn't mean we'll never ride the waves of warped space-time.
Now a group of physicists have put together the first proposal for a physical warp drive, based on a concept devised back in the '90s. And they say it shouldn't break any of laws of physics.
Theoretically speaking, warp drives bend and change the shape of space-time to exaggerate differences in time and distance that, under some circumstances, could see travelers move across distances faster than the speed of light.
One of those circumstances was outlined more than a quarter of a century ago by Mexican theoretical physicist Miguel Alcubierre. His idea, proposed in 1994, was that a spacecraft powered by something called an 'Alcubierre drive' could achieve this faster-than-light travel. The problem is it requires a lot of negative energy in one place, something that's simply not possible according to existing physics.
But the new study has a workaround. According to researchers from the independent research group Applied Physics based in New York, it's possible to ditch the fiction of negative energy and still make a warp drive, albeit one that's maybe a bit slower than we'd like.
"We went in a different direction than NASA and others and our research has shown there are actually several other classes of warp drives in general relativity," says astrophysicist Alexey Bobrick, from Lund University in Sweden.
"In particular, we have formulated new classes of warp drive solutions that do not require negative energy and, thus, become physical."
Why is negative energy such a big deal? The need for negative energy gets around some of the general relativity problems of faster-than-light travel, by allowing for space to expand and contract faster than light, while keeping everything within its warping within universal speed limits.
Unfortunately, it introduces more problems of its own – primarily that the negative energy we'd require exists only in fluctuations on a quantum scale. Until we can figure a way to scoop up a Sun-sized mass of the stuff, this kind of drive just isn't possible.
The new research works around this – according to the paper, negative energy wouldn't be required, but a hugely powerful gravitational field would be. The gravity would do the heavy lifting of bending space-time so that the passage of time inside and outside the warp drive machine would be significantly different.
You won't be able to book tickets just yet though – the amount of mass required to produce a noticeable gravitational effect on space-time would be at least planet-sized, and there are still plenty of questions to answer.
"If we take the mass of the whole planet Earth and compress it to a shell with a size of 10 metres, then the correction to the rate of time inside it is still very small, just about an extra hour in the year," Bobrick told New Scientist.
One other interesting finding from the research concerns the shape of the warp drive: a wider, taller vessel will need less energy than a long and thin one. Think of a plate being held upright thrown at a wall face first, and you have an idea of the optimum warp drive shape.
Even though the reality of travelling to distant stars and planets is still a long way off, the new study is the latest addition to a growing body of research that suggests that the principles of warp drives are sound in scientific terms.
The researchers admit that they're still not sure exactly how to put together the technology that they've described in their paper, but at least more of the numbers add up now. They're confident that far into the future, the warp drive will become a reality.
"While we still can't break the speed of light, we don't need to in order to become an interstellar species," says Gianni Martire, one of the scientists at the Applied Physics group behind the new study. "Our warp drive research has the potential to unite us all."
The research has been published in Classical and Quantum Gravity.