Free The Physics of Star Trek by Lawrence M. Krauss Page B

instead of being reflected from it. The
     distinction between this and deflecting light rays away from the
    
    
     Enterprise
    
    
     is thus pretty subtle. In this connection, a question that puzzled many trekkers until the
    
    
     Next Generation
    
    
     episode “The Pegasus” aired was, Why didn't the Federation employ cloaking technology? It
     would certainly seem, in light of the above, that any civilization that could develop
     deflector shields could develop cloaking devices. And as we learned in “The Pegasus,” the
     Federation was limited in its development of cloaking devices by treaty rather than by
     technology. (Indeed, as became evident in “All Good Things ...,” the last episode of the
    
    
     Next Generation,
    
    
     the Federation eventually seems to have allowed cloaking on starships.)
    Finally, given this general-relativistic picture of warp drive, warp speeds take on a
     somewhat more concrete meaning. The warp speed would be correlated to the contraction and
     expansion factor of the spatial volume in
    front of and behind the ship. Warp-speed conventions have never been particularly stable:
     between the first and second series, Gene Roddenberry apparently decided that warp speeds
     should be recalibrated so that nothing could exceed warp 10. This meant that warp speed
     could not be a simple logarithmic scale, with, say, warp 10 being 2
    
    
     10
    
    
     = 1024 x light speed. According to the
    
    
     Next Generation Technical Manual,
    
    
     warp 9.6, which is the highest normal rated speed for the
    
    
     Enterprise-D,
    
    
     is 1909 x the speed of light, and warp 10 is infinite. It is interesting to note that in
     spite of this recalibration, objects (such as the Borg cube) are periodically sighted
     which go faster than warp 10, so I suppose one shouldn't concern oneself unduly about
     understanding the details.
    Well, so much for the good news....
    Having bought into warp drive as a nonimpossibility (at least in principle), we finally
     have to face up to the consequences for the right-hand side of Einstein's equationsnamely,
     for the distribution of matter and energy required to produce the requisite curvature of
     space-time. And guess what? The situation is almost
    
    
     worse
    
    
     than it was for wormholes. Observers traveling at high speed through a wormhole can
     measure a negative energy. For the kind of matter needed to produce a warp drive, even an
     observer at rest with respect to the star-shipthat is, someone on boardwill measure a
     negative energy.
    This result is not too surprising. At some level, the exotic solutions of general
     relativity required to keep wormholes open, allow time travel, and make warp drive
     possible all imply that on some scales matter must gravitationally repel other matter.
     There is a theorem in general relativity that this condition is generally equivalent to
     requiring the energy of matter to be negative for some observers.
    What
    
    
     is
    
    
     surprising, perhaps, is the fact, mentioned earlier, that quantum mechanics, when combined
     with special relativity, implies that at least on microscopic scales the local
     distribution of energy can be negative. Indeed, as I noted in chapter 3, quantum
     fluctuations often have this property. The key question, which remains unanswered to date,
     is whether the laws of physics as we know them will allow matter to have this property on
     a macroscopic scale. It is certainly true that currently we haven't the slightest idea of
     how one could create such matter in any physically realistic way.
    However, ignore for the moment the potential obstacles to creating such material, and
     suppose that it will someday be possible to create exotic matter, by using some
     sophisticated quantum mechanical engineering of matter or of empty space. Even so, the
     energy requirements to do any of the remarkable playing around with spacetime described
     here would