The Alcubierre Drive Might Someday Be A Reality
NASA seems to be of the opinion that warp-speed is no longer science-fiction. To any fan of the genre, this won't be news because, on 11th June 2014, the mainstream press in the UK reported that NASA had revealed designed for a craft which might make interstellar travel a reality. They also reported that NASA had sat down with an artist to give some visual life to that reality (Matthew Jeffries, who designed the USS Enterprise). The result really is rather beautiful and about as close to what most sci-fi fans might have dreamed up themselves. Meet the IXS Enterprise. These wonderful designs are rendered by Mark Rademaker.
Using an Alcubierre drive, (named after Mexican theoretical physicist, Miguel Alcubierre), through the auspices of NASA and Dr Harold "Sonny" White, it might be possible to ‘bend’ space-time, and travel tremendous distances almost instantly. WOW! That's momentous!
What was curious to me when I read this, as a science-fiction author with a (very) limited understanding of theoretical physics, was that faster-than-light (or superluminal) travel has usually been discounted as "science-fiction" in the truest sense for some time. Many physicists say it offends the theory of special relativity. It depends, of course, on your definition of "faster than light" and many theories out there seem to be subsets of categories which actually postulate interstellar travel which is not actually 'faster-than-light'. For example, could the speed of light be slowed down to the point where something else might travel faster through a given medium than light can (the Cherenkov Effect)? There are other arguments, but they seem to revolve around artificial construction of the speed of light, rather than a means of moving faster than the universal constant.
Miguel Alcubierre became famous by postulating a theory which utilised a warp 'bubble' to describe what we might consider to be the Star Trek 'warp drive'. Dr Alcubierre was inspired by the show and in fact references it in his work (and he even emailed William Shatner to tell him about the fact the show had inspired him). It is Dr. Alcubierre's work that NASA are working on (Alcubierre was a college physics student when he came up with the theory, but abandoned it due to the power problems he saw). The 'warp' in space-time might make it possible for an object to travel faster then light while remaining on a timelike curve. Dr. Alcubierre wrote, “in this way, the spaceship will be pushed away from the Earth and pulled towards a distant star by space-time itself.” Dr. White has famously likened it to stepping onto a moving walkway at an airport. However, as Dr. Alcubierre noted in his largely theoretical paper, to create such a warp would require exotic matter with negative energy density and, even if such exotic matter can exist, it is not yet clear how it could be deployed to make the warp drive work. This is what Dr White and NASA are trying to do and they think they might be close to making it a reality. In theory, interstellar travel which might otherwise have taken thousands of years could be completed in weeks or months.
There is some scepticism about this. Wired reported soon after on the tests and were less than complimentary (it's an interesting article to read on its own):
The team was testing a theory that there’s a new way to propel satellites, instead of using rockets powered by a limited supply of fuel. So they put a radio antenna in a specially designed, sealed container. Turned on, the antenna bounced 935MHz radio waves (similar to those used by some cell phones) around, and the container apparently moved a tiny, tiny bit. This violates Newton’s third law of motion, one of the basic tenets of physics.
Loosely put, Newton taught us that no action can occur without an equal and opposite reaction. Because there is nothing pushing against the container, propelling it along—no hot gases exploding out the back, for example—it shouldn’t be able to move. It’s like moving a broken-down car by pushing it from the inside.
But David Warmflash, writing for Discover magazine, was not impressed by Wired's analysis and had this to say:
We don’t know how the story will turn out, but for the record let’s establish one thing: if the new engine works, it does not violate Newton’s third law. The misunderstanding is based on the fact that the propulsion device does not require a supply of reaction mass. Instead the idea is that, using a kind of electromagnetic effect, it manages to exert force against virtual particles in space. These are subatomic particles that, according to quantum theory, continuously pop into and out of existence. Newton’s theory is a special case that does not apply in the quantum world, just as it does not apply to objects moving at relativistic speeds (close to the speed of light).
Einstein demonstrated the latter, which did not disprove Newton, but expanded on his discoveries, while a series of other physicists developed quantum theory, which also does not disprove Newton. Whether you’re throwing a basketball, performing a double twisting back somersault, or flying supersonic across the Atlantic Ocean, Newton is still correct. And he’d be correct with this experimental engine too, taking the virtual particles into account. Yes, they sound weird, but in terms of a reaction mass, they’re like the water or the air being pushed back by the propeller of a boat or airplane.
The power of the recent hollywood blockbuster Interstellar cannot be underestimated either. It demonstrates that we are not only still enthralled by the idea of interstellar travel, but also that we still have a soft spot for science fiction. Interstellar may have got an awful lot wrong, but no one ever got it right first time in anything that actually mattered. We are not going to travel out of our solar system, even our galaxy, unless we applaud the people trying to find that answer rather than ridiculing them. A Hollywood blockbuster is a great way to capture the attention of the public.
The impossibility of faster-than-light relative speed only applies locally which is what the Alcubierre warp 'bubble' takes advantage of. Wormholes might allow superluminal travel by ensuring that the speed of light is not exceeded locally at any time. While traveling through a wormhole, subluminal (slower-than-light) speeds are used. Classic wormholes, or Einstein-Rosen bridges, are "shortcuts" through space-time from one location in space to another – essentially tunnels where the ends are at different points in space-time. Think of a wormhole as a tunnel through a huge mountain – light travelling around the mountain might well reach the other side after a spaceship travelling along a tunnel through the mountain. Obviously, light travelling through that tunnel would travel faster than the spaceship. It's a shortcut, rather than an attempt to travel superluminally. Like all tunnels, it's a workaround (or a workhrough).
In Beyond the Wall, I chose to use wormholes for interstellar travel because it fits the storyline which unfolds much later on in the series. Wormholes are a feature of classical general relativity, but creating them requires a change the topology of space-time, which is thought to be possible. Wormholes which could actually be crossed in both directions, known as traversable wormholes, would only be possible if exotic matter with negative energy density could be used to stabilise them (this sounds awfully familiar to the Alcubierre problem). Misner and Thorne have suggested using the Casimir Effect on a grand scale to generate the negative energy, while Visser (whose grandson features in my series as the person credited with discovering wormholes) has proposed a solution involving cosmic strings. These are very speculative ideas which may not be possible – exotic matter with negative energy simply may not exist in the form we need.
Kip Thorne has found that if wormholes can be created, then they can be used to construct closed timelike loops in space-time which would imply the possibility of time travel. Stephen Hawking says that wormholes would simply be unstable and therefore unusable. The subject remains hotly debated, but a verdant area for theoretical experimentation.
I love this stuff and it is exciting as hell. Whether we are close to a warp-drive or, as in Beyond the Wall, we are able to create wormholes, interstellar travel is suddenly back on the menu, and we sure as hell should be encouraging it, rather than doubting it. Right now, we could do with a few wins.