What an Alcubierre drive does to the fabric of spacetime.
"Well, would you look at that? It never occurred to me to think of space as the thing that was moving."
has long been a staple of science fiction since it allows you to travel to other solar systems and back inside of a human lifetime. In real life, of course,
according to basic Einsteinian physics
particles with mass can never reach the speed of light, never mind going over it.
In 1994, however,
Mexican theoretical physicist Miguel Alcubierre (pronounced "al-cu-BYER-re") came up with a solution that is technically possible, albeit still out of reach of current technology. There's no law that space itself
cannot exceed c
, so instead of trying to accelerate the object past the speed of light, you move space itself around the object. The ship creates a bubble of spacetime of sorts, compressing space ahead of it and expanding behind it. Since the ship is not moving faster than light relative to the bubble, relativity is not violated. And there is no possible viewpoint from which you can see both the inside and outside the bubble, and find out it moves FTL; the inside of the bubble becomes undetectable to the rest of the universe when the light barrier is broken, and vice-versa: you cannot peek from inside the bubble. This makes the warp bubble behave very similarly to various fictional "hyperspace" drives.
The tricky part is, mathematically this requires a negative energy density, which in turn requires the generation of lots and lots of exotic matter with negative mass: a warp bubble (yes, Alcubierre used this term) large enough for a ship 200 meters across would require ten billion times the mass of the observable universe (though contracting the bubble's perimeter and expanding the volume inside it potentially reduces this to less than three solar masses). There's also various other interesting results, ranging from a possible Hyperspace Lanes
implementation to the fact that when a ship decelerates from FTL, the energy release would fry anything ahead of it
There are several more proposed implementations of the Alcubierre drive that partly eliminate the original's fatal flaws. According to Cleaver and Obousy of Baylor University, the required mass is merely one Jupiter, not the whole universe. And if Harold "Sonny" White of NASA is right in his proposal of altering the warp bubble's shape, it's merely hundreds of kilograms*:
, and the exhaust problem is kinda fixed, too. However, the problem with obtaining negative mass is still standing.
Fiction authors, of course, don't have to face the problem of actually building a practical Alcubierre drive, and since it was proposed it has become popular in harder sci-fi
as a method of achieving Faster-Than-Light Travel
without violating physics as they are currently understood.
A form of Reactionless Drive
and usually a subtrope of Faster-Than-Light Travel
Fictional uses of the Alcubierre drive:
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- Warren Ellis' Orbiter all but directly states that the shuttle has one of these. The name is not stated, but the description and picture of the warp field matches and Prof. Alcubierre's name is mentioned.
- Used in both FTL and STL forms in the Star Carrier series. To go to FTL, most ships have to accelerate to near-c, whereupon they can use their relativistic mass to create an Alcubierre effect capable of traveling about a light-year and a half per day.* At slower-than-light speeds the drive works the same way to accelerate capital ships to fast enough speeds to cross star systems in a reasonable amount of time. Fighters are small enough to use a singularity drive instead (generate a high-gravity field in the direction of travel and blink it on and off really fast to pull the ship), allowing much higher delta-v.
- Used in Stephen Baxter's novel Ark. The ship, Ark 1, is actually composed of two hulls connected with a tether, rotating around each other to generate gravity. Interestingly, due to how the ship's drive works, every jump is a Blind Jump: the destination is calculated beforehand, but once the ship enters warp, there's no way to drop out of it or even see what's happening at the destination prior to arriving.
- Charles Stross' Eschaton series has the Alcubierre drive as one of about six methods of FTL travel or communication currently in use. It's mentioned to be extremely dangerous and difficult to use.
- Star Trek's warp drive is a form of Alcubierre Drive, at least according to some of the technical manuals, and was the inspiration for Prof. Alcubierre's theory. The ship is surrounded by a series of fields that distort ("warp") space around the ship.
- Role Master, Spacemaster Privateer campaign setting. The Quantum Drive uses quantum fields to warp space. The fields contract space in front of the ship and dilate space behind it, allowing the ship to effectively exceed the speed of light.
- The Tarka in Sword of the Stars use Alcubierre drives. They're the slowest but least restricted form of FTL in the game (humans and Zuul use Hyperspace Lanes, Hivers a Portal Network, and Liir and Morrigi speed is variable).
- The Shockpoint drive of Dead Space may be based on the Alcubierre drive.
- Star Control 3 has "warp bubble drive" as an alternative to conventional hyperdrive, which continues to work after hyperdrives cease functioning in our part of the galaxy. The technical details aren't elaborated, though. Considering when the game was made, it may have been a case of Ripped from the Headlines.
- According to the manual for Pandora First Contact, all the ships (6 Sleeper Starships and 1 Generation Ship) sent to colonize the titular world were equipped with Alcubierre drives to allow them to accelerate to relativistic speeds. They were still STL, but much faster than a traditionally-propelled ship would be.
- Orion's Arm has these used on ships built by Archailects, though they can't exceed the speed of light and all but the most advanced put the ship outside the warp bubble, as it takes Sixth Singularity technology to dissolve a warp bubble without annihilating everything inside.
- FutureTimeline.net predicts that humans will have one by 1,000,000 A.D.