https://en.wikipedia.org/wiki/Alcubierre_drive The Alcubierre drive or Alcubierre metric (referring to metric tensor) is a speculative idea based on a solution of Einsteins field equations in general relativity as proposed by theoretical physicist Miguel Alcubierre, by which a spacecraft could achieve faster-than-light travel if negative mass existed. Rather than exceeding the speed of light within its local frame of reference, a spacecraft would traverse distances by contracting space in front of it and expanding space behind it, resulting in effective faster-than-light travel. Objects cannot accelerate to the speed of light within normal spacetime; instead, the Alcubierre drive shifts space around an object so that the object would arrive at its destination faster than light would in normal space.[1] Although the metric proposed by Alcubierre is mathematically valid in that it is consistent with the Einstein field equations, it may not be physically meaningful or indicate that such a drive could be constructed. The proposed mechanism of the Alcubierre drive implies a negative energy density and therefore requires exotic matter, so if exotic matter with the correct properties does not exist then it could not be constructed. However, at the close of his original paper[2] Alcubierre argued (following an argument developed by physicists analyzing traversable wormholes[3][4]) that the Casimir vacuum between parallel plates could fulfill the negative-energy requirement for the Alcubierre drive. Another possible issue is that although the Alcubierre metric is consistent with general relativity, general relativity does not incorporate quantum mechanics, and some physicists have presented arguments to suggest that a theory of quantum gravity which merged the two theories would eliminate those solutions in general relativity which allow for backwards time travel (see the chronology protection conjecture), of which the Alcubierre drive is one.
Posted on: Sun, 02 Feb 2014 18:13:16 +0000
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