SYDNEY: The search for the Holy Grail of intergalactic travel has encountered a slight hitch, say Australian scientists.
Recent research predicts that upon reaching its destination, the theoretical Alcubierre warp drive – a speculative idea proposed by Mexican theoretical physicist Miguel Alcubierre in 1994 by which a spacecraft could be accelerated to speeds greater than the speed of light – would unleash a high energy cocktail of particles and radiation, blasting anyone in its path “into oblivion”.
The findings echo science-fiction more than science-fact, and make astronauts travelling by warp speed the ultimate in unwelcome guests, according to a paper accepted for publication in Physical Review D. The finding was unexpected for the University of Sydney researchers, who had set out to investigate the danger to astronauts posed by particles and radiation passing through a spaceship travelling at warp speed.
Warp speed travel: theoretically possible
The eponymously named Alcubierre warp drive theoretically allows for faster-than-light travel by dramatically distorting the fabric of spacetime. In exotic conditions like these, the constraints of Einstein’s special theory of relativity are craftily sidestepped, removing the normal physical limits on speed. The drive achieves the feat by ‘picking up’ and moving space itself.
“There’s actually very few rules on what you’re allowed to do to space itself,” said lead author and astrophysicist Brendan McMonigal. “Without travelling faster than the speed of light in space, you can [still] get from where you are to somewhere very far away in an arbitrarily short space of time by picking up that space you are in and moving it to somewhere else.”
The Alcubierre warp drive places a spaceship inside a spherical shell or bubble of curved spacetime. While the Earth’s gravity is one example of a mild distortion in spacetime, the warp drive bubble is a more extreme version.
Riding like a surfer
Inside the bubble is a safe cocoon of so-called flat spacetime, where no harmful effects are felt by astronauts on the ship and clocks run exactly as they would on Earth. The astronauts are also at no risk of acceleration or deceleration injuries.
“Normally, if you were to get into a spaceship and fly off to some distant place, you’d be slammed into the back of the spaceship as you experience an extreme amount of acceleration, but because we’re picking up the space the spaceship is in and moving that, the astronaut will be in freefall the entire time. They’ll be floating in the spaceship and won’t be experiencing the effects of the acceleration,” said McMonigal.
Around the edge of the warp drive bubble, things become more peculiar. Spacetime is contracted at the front of the bubble and expanded at the back of the bubble. The difference creates a wave of warped spacetime that the bubble, with spaceship inside it, rides like a surfer at speeds faster than light.
The distortion at the front of the warp bubble was found to be responsible for the explosive breaking effect of the warp drive. As the warp drive travels through space, it sucks up any particles and radiation it encounters like a vacuum cleaner.
The researchers predicted the behaviour of the particles and radiation using a computer model that calculated the distortions in spacetime produced by the Alcubierre warp drive. They used Einstein’s general theory of relativity to estimate the paths and energies of the particles.
“What we actually found was that the particles inside the bubble itself, the ones that do get in, would not be a significant danger to anybody inside the spacecraft,” said Geraint Lewis, astrophysicist and senior author of the study.
What was more of a surprise was the finding that some particles get caught up in front of the bubble, and carried along with the warp drive. The computer model went several steps further and proved that over the course of the journey, the particles can absorb unlimited amounts of energy and when the warp drive stops, the particles are released in a destructive high-energy beam. “We hadn’t really expected that,” said Lewis.
Dodging the energy burst
The findings spell bad news for anybody at the warp drive destination. But could the friendly fire of the warp drive be avoided by aiming to one side of your destination? Lewis said further research of the problem in 3-D is needed before that question can be answered.
“We didn’t look at the full 3-D effect of the bubble, so we don’t know if when you stop the drive if it sprays off particles in all directions or if it’s just a very finely collimated beam, but we do know it will throw off beam of high-energy particles,” said Lewis. “So we don’t know [yet] how much to the left or the right you need to stand to be safe!”
In-press paper for Physical Review D
Geraint Lewis’s homepage
Miguel Alcubierre’s original paper in Classical and Quantum Gravity