SHE'LL NO' take it, captain!" How oft was chief engineer Scott's protest aired on the bridge of the Starship Enterprise in Star Trek to no avail? A gung-ho James T Kirk (William Shatner, below) would rev up the anti-matter engines, regardless, to warp factor 10.

Ah, that good old warp-drive. Where would science fiction be without it? Stuck at the start of a very long journey. Even the most advanced propulsion we could design today would take tens of thousands of years to reach the stars.

The real science will be examined on Thursday at a British Interplanetary Society (BIS) symposium in London, entitled Warp Drive, Faster Than Light: Breaking The Interstellar Distance Barrier.

A key problem for warp drive is that nature appears to have a built-in speed bump: the speed of light, 186,000 miles per second. Nothing can exceed this, which means a one-way trip to even our nearest star other than the sun would take over four years at light-speed.

But what if we could cheat the light-speed barrier rather than breach it? What if, instead of traversing spatial distance, we nobbled space-time itself? Or, in other words, created a warp in the cosmos, scrunching up the space-time between us and our chosen destination.

Does this sound nonsensical? How, you ask, can we warp nothingness?

But space-time isn't just nothingness, according to post-Einstein science. It is a malleable medium distorted by matter and gravity. We already know that massive objects like the sun create a dent in the local space-time they occupy, because light from other stars is slightly bent as it passes the sun.

Sci-fi writers pounced on this decades ago. If space-time can be warped naturally, why couldn't a spacecraft of the future artificially induce such an effect? Today, a number of scientists are asking that, too. Ever since Mexican physicist Miguel Alcubierre published a seminal 1994 paper that set out equations describing a warp drive, the concept has edged from the fringe towards the scientific mainstream.

"The main purpose of this week's symposium is to raise awareness of this obscure field of research within general relativity and quantum field theory," says Kelvin Long, of the BIS. "If the fine details are hazy, the principle is sound and well described by Einstein's general relativistic theory of gravity."

The idea is that a vehicle would be confined in a "bubble" of its own space-time. The space in front of the bubble is made to collapse (like a black hole) and the space behind is made to expand (as in the Big Bang). This means that objects in front of the vehicle get closer and objects behind it get further away.

"Although Einstein's special theory of relativity prohibits any object from exceeding the speed of light," explained Long, "it does not prohibit the speed of light itself being a different value, by altering the geometry of space. For example, it is believed that the early universe expanded faster than the speed of light during a period called inflation. So this is, in essence, how the vehicle attains a speed which appears to be faster than the nominal value of light-speed that you and I are used to."

And just how do we "collapse" space-time? We'd need something called negative energy to produce a repulsive gravitational field that causes space-time to expand, or to "push" it away. This is what would seem to give the vehicle its forward motion - although in reality it's the rest of the universe that is moving, not the ship. There is some evidence that negative matter exists, but it's certainly not in abundance, and we'd need lots of it to warp space-time.

That the BIS is holding this symposium, then, does not imply that there is confidence in the warp drive as a realistic proposal for interstellar travel. "The majority of scientists do not consider it a viable method of interstellar travel, either today or in the near future," Long cautions. "The physics indicates that the technical problems are prohibitive."

For instance, estimates suggest it would require astronomical quantities of negative energy to create the necessary space-time warpage. A 100-metre bubble would require 10 to the power of 65 grams of negative mass.

"However, there is still so much we don't know about physics," says Long, a space science teacher at Reading University. "Dark energy, for instance; no proper quantum description of gravity, incompatibilities between general relativity and quantum mechanics. So in my view, we can't rule warp drive out until our understanding of physics and its constraints is more mature."

And this field of research is very young, he emphasises. Future research may present a more optimistic picture. "These issues are hotly debated by those who work in this area. Every year a new paper is published that sheds new insights into the problem," he says.

"I believe that a large advancement in our knowledge of the warp drive will likely come about through other experiments like the Large Hadron Collider a particle accelerator and collider due to begin operation near Geneva next year and gravitational-wave detectors. We really don't know what causes gravity. If we can get a better understanding, we'll be able to evaluate whether it can be used to manipulate space-time, and whether the warp drive is a realistic proposal."

John Davies, an astronomer at the Royal Observatory in Edinburgh, commented: "Practical warp drive sounds hard to believe, but the British Interplanetary Society has a history of doing unusual, almost crackpot things.

"In the 1940s, it published a moon-ship design. In the 1970s, it wrote about off-planet mining of the rare helium-3 isotope to power an unmanned starship. Today, Apollo 11 is history and helium-3 mining is being used to justify a return to the moon. So it is right to keep pushing ahead and thinking about what might just be possible a few decades from now."

Good news, perhaps, for future Captain Kirks. Bad news for poor old Scotty's blood pressure.