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

be carried along with the expanding
     wave of space.
    One way to picture what is happening is to imagine yourself on the starship. If space
     suddenly expands behind you by a huge amount, you will find that the starbase you just
     left a few minutes ago is now many light-years away. Similarly, if space contracts in
     front of you, you will find that the starbase you are heading for, which formerly was a
     few light-years away, is now close to you, within reach by normal rocket propulsion in a
     matter of minutes.
    It is also possible to arrange the geometry of spacetime in this solution so that the huge
     gravitational fields necessary to expand and contract space in this way are never large
     near the ship or any of the star-bases. In the vicinity of the ship and the bases, space
     can be almost flat, and therefore clocks on the ship and the starbases remain
     synchronized. Somewhere in between the ship and the bases, the tidal forces due to gravity
     will be immense, but that's OK as long as we aren't located there.
    This scenario must be what the Star Trek writers intended when they invented warp drive,
     even if it bears little resemblance to the technical descriptions they have provided. It
     fulfills all the requirements we listed earlier for successful controlled intergalactic
     space travel: (1) faster-than-light travel, (2) no time dilation, and (3) no resort to
     rocket propulsion. Of course, we have begged a pretty big question thus far. By making
     spacetime itself dynamical, general relativity allows the creation of “designer
     spacetimes,” in which almost any type of motion in space and time is possible. However,
     the cost is that the theory relates these spacetimes to some underlying distribution of
     matter and energy. Thus, for the desired spacetime to be “physical,” the underlying
     distribution of matter and energy must be attainable. I will return to this question
     shortly.
    First, however, the wonder of such “designer spacetimes” is that they allow us to return
     to Newton's original challenge and to create iner-tial dampers and tractor beams. The idea
     is identical to warp drive. If spacetime around the ship can be warped, then objects can
     move apart or together without experiencing any sense of local acceleration, which you
     will recall was Newton's bane. To avoid the incredible accelerations required to get to
     impulse sublight speeds, one must resort to the same spacetime shenanigans as one does to
     travel at warp speeds. The distinction between impulse drive and warp drive is thus
     diminished. Similarly, to use a tractor beam to pull a heavy object like a planet, one
     merely has to expand space on the other side of the planet and contract it on the near
     side. Simple!
    Warping space has other advantages as well. Clearly, if spacetime becomes strongly curved
     in front of the
    
    
     Enterprise,
    
    
     then any light rayor phaser beam, for that matterwill be deflected away from the ship.
     This is doubtless the principle behind deflector shields. Indeed, we are told that the
     deflector shields operate by “coherent graviton emission.” Since gravitons are by
     definition particles that transmit the force of gravity, then “coherent graviton emission”
     is nothing other than the creation of a coherent gravitational field. A coherent
     gravitational field is, in modern parlance, precisely what curves space! So once again the
     Star Trek writers have at least settled upon the right language.
    I would imagine that the Romulans' cloaking device might operate in a similar manner. In
     fact, an
    
    
     Enterprise
    
    
     that has its deflector shield deployed should be very close to a cloaked
    
    
     Enterprise.
    
    
     After all, the reason we see something that doesn't shine of its own accord is that it
     reflects light, which travels back to us. Cloaking must somehow warp space so that
     incident light rays bend around a Warbird