Re: gravity and ftl [longish] (was severalm other things)

Andrew Martin, Alex Shvarts & Brian Martin (although i suspect Mr Martin
wrote it and shamelessly used other people's names :-) wrote:

> In several SF systems, the writers suggest that FTL drives only work
in
> near-flat space.

for instance, i think this is how it works in the battletch books

> If I recall correctly, these are also Lagrange points.

i don't think there's any 'also' about it - as far as i know that's the
definition of a Lagrange point!

> Around our Earth and Moon, there are, if I recall correctly, six L
points.

i can only think of five - one point between the two, one 'behind'
either body and two equidistant from them and in the plane of the orbit
(the Trojan points). mind you, this probably just means i can't remember
the sixth.

note that there is a set of L points for every pair of bodies, ie many,
given that there is in the Sol system (maybe a poor example, too many
objects) one star, two gas giants, four rocky planets, two ice subgiants
and pluto, along with thirty-odd (?) moons, and einstein knows how many
asteroids (not to mention the particles in the rings of saturn and
jupiter, comets, 'roids outside the belt and man-made entities), and
that each body has one set of L points (5 or 6) for each other body in
the system (10 major bodies, so 90 sets, so 540 points just for
starters).

the points formed by these major bodies would be easier to predict,
since their motion is well measured; the smaller bodies, such as
asteroids, not only have less-well-measured paths, but (see The
Many-Body Problem, Henri Poincare, nonlinear dynamics of the solar
system, etc) their paths are actually chaotic (in the mathematical
sense) and hard to predict; thus, there will be masses of jump points
swarming about a system without much predictability.

in Battletech, i seem to remember that these were known as 'pirate
points' - being used mainly by pirates and other units seeking secrecy
and not averse to risks.

incidentally, if you have Java and decent computational power, try the
gravity simulator applet at:

http://www.newscientist.com/student/newton/newton.htm

which i wrote. well, part of it - another guy did the user interface, i
did the physics (i just tried this and it didn't work - the bug must be
in the other guy's code, all my pointers are properly initialised :-).

hope this helps,
Tom