Than Light from amazon.com
LIGHT: SUPERLUMINAL LOOPHOLES IN PHYSICS
What's so special about the speed of light? Why do physicists like Einstein
insist that nothing can exceed light speed (Warp Speed 1 in Star Trek)?
Is it possible to evade this speed limit using exotic devices? What about
time travel? (The Japanese edition of this book is called: "How to
Make a Time Machine").
FTL reveals the fundamental postulate that lies behind the Einstein speed
limit--the so-called Causal Ordering Principle (COP) that requires all causal
processes (such as signals) to have the same time direction for all observers.
Space and time may be different for different observers but causal ordering
must be the same for all. Backwards-in-time causal processes are not forbidden
(by relativity at least) but such processes must appear to go backwards
in time for all observers. On page 59, Nick lists 14 "things"
that go faster than light--including comet tails and the subjective velocity
of a space traveller in a near-lightspeed ship--but none of these apparently
superluminal "things" can be used to send signals so they are
immune from the COP rule.
FTL examines several "loopholes" in the subluminal speed law many
of which have already been examined by science fiction writers including
warped space-time such as will be encountered in the vicinity of black holes,
"phase waves" which for some situations are compelled to always
travel faster than light, and the mysterious "quantum connection"
recently proved necessarily superluminal by Irish physicist John Bell.
FTL introduces plausible time travel devices such as the massive rotating
Tipler Top and particular attempts to exploit the quantum connection to
send superluminal signals.
FTL examines the logical paradoxes that time travel might introduce and
suggests ways in which the universe might resolve these paradoxes.
"The Enterprise's maximum cruising speed is Warp 6 (216 times
light speed). At Warp 6, travel time to the nearest star (4 light-years
distant) is about a week. To the crew of the Enterprise, warp drive
technology makes star systems seem as close together as Pacific islands
in the days of clipper ships." (FTL p 16)
"The attempt to send FTL messages via Bell's quantum connection can
be compared to the attempt to utilize superluminal phase velocity for the
same ends. In the quantum case, the message does not get through because
to the receiver the signal looks utterly random. On the other hand, the
superluminal phase wave is perfectly periodic--an infinitely long and infinitely
boring sine wave, whose monotonously identical peaks and valleys are unblemished
by any message. But perfect randomness and perfect order are equally devoid
of meaning. Only a signal that lies somewhere between these two extremes
qualifies as a meaningful message." (FTL p 178)
"Special relativity, which in conjunction with the COP rule seems to
outlaw time travel, paradoxically provides the main reason for a physicist
to believe in time travel because relativity seems to assert that time is
a dimension on a par with space. If time is like space then the past must
literally still exist "back there" as surely as Moscow still exists
even after I have left it. If the past still exists, then it makes sense
to consider whether one could actually travel there." (FTL p 191)
THAN LIGHT from amazon.com--Earth's biggest bookstore.