*85**Advanced Space Propulsion Based on Vacuum (Spacetime Metric) Engineering*11 1

*g*−

<

objects would expand - thus the fourth entry in Table 1 of physical effects.

**3.3****Velocity of Light in Spacetime-Altered Regions**Interior to a spacetime region altered by, say,

a dense mass(e.g., a black hole, the locally-measured

velocity of light *c* in,

say, the

*x*1

=

*r* direction, is given by the ratio of locally- measured (proper) distance/time intervals fora propagating light signal [13]

11 00

*i**L**g dr**v**c**g dt*−

=

=

(6)

From

a viewpoint *exterior* to the region, however, from the

above the remotely-observed *coordinate* ratio measurement yields a different value 11

*e**L**g**dr**v**c**dt**g*=

=

−

(7)

Therefore, although a local measurement with physical rods and clocks yields

*c*, an observer in an exterior reference frame remote from the mass speaks of light slowing down on a radial approach to the mass due to the ratio 11 1

*g**g*−

<

Conversely, under (metric engineering)

conditions for which00 11 1

*g**g*−

>

the velocity of light - and advanced-technology craft velocities that obey similar formulae – would appear superluminal in the exterior frame. This yields the fifth entry in Table 1 of physical effects.

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