Brief Histories: The Alcubierre Drive

The ‘Brief Histories’ series is a recurring profile of a fascinating theory or concept in science. For notifications of new articles and updates to the series, follow MFP on Twitter: @ThePhysicsBlog The Alcubierre Metric is a warp-field derived from the principles of General Relativity, though is not a wormhole. A real physical theory inspired by the ‘warp-drive’ of science-fiction, theoretical physicist Miguel Alcubierre proposed that a spacecraft could achieve apparent faster-than-light travel if negative mass can be created. The Inception Alcubierre’s 1994 paper begins by introducing locality in general relativity. Its the principle of locality that has enabled theorists to conceive of non-tachyonic superluminal transmissions ( i.e. traversable wormholes). Inside the ‘warp-bubble’, a spaceship would be stationary relative to the local spacetime. It is implied that it may be possible to warp spacetime in a small region (similar to a bubble) so as a spaceship within Alcubierre’s metric can achieve an arbitrarily high velocity relative to observers in ‘flat’ spacetime outside the metric. The Argument Exotic matter would almost certainly be required for the metric. However, if a less recognized theory of quantum gravity called conformal gravity were proven true, the Alcubierre metric could in-principle be produced without exotic matter. There are solid arguments against Alcubierre’s metric outside of exotic matter as well. Most prominently, a spaceship at the center of the warp bubble would be causally separated from the boundary. This means that regardless of whether negative energy densities are producible, a real spaceship could neither create nor control a warp bubble. Additionally, proposed methods of superluminal travel always create time-travel paradoxes in relativity, as Alcubierre himself recognized in an online forum: “The conjecture does not prohibit faster-than-light travel. It just states that if a method to travel faster than light exists, and one tries to use it to build a time machine, something will go wrong: the energy accumulated will explode, or it will create a black hole.”      – Miguel Alcubierre The Status NASA has stated in 2012 that one of their laboratories was running an interferometer to determine if the spacetime of the Alcubierre metric is correct. However Alcubierre expressed skepticism that his theory could be verified with current technology. Proceed to the Next Post: Brief Histories: The Quantum Zeno Effect

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