"Well, would you look at that? It never occurred to me to think of space as the thing that was moving."Faster-Than-Light Travel 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 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. And for the record, it's pronounced "al-cu-BYER-re". A form of Reactionless Drive and usually a subtrope of Faster-Than-Light Travel.
— Lt. Cdr. Montgomery Scott, Star Trek
Fictional uses of the Alcubierre drive:
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