Hideously OT: Langrange Points Re: gravity and ftl

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

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!

Ok, I am going to inject physics into this discussion.

The five Lagrange points are not a place where space-time is flat.
Lagrange points are places where the gravitational attaction between two
bodies coupled with the angular momentum a third body has makes the position
of the third body stable. The angular momentum part of all this makes Lagrange
points not just depend on gravity. In other words, for an asteroid to stay in
the Trojan points of Jupiter it must be moving a very specific orbital
velocity (ie, the same orbital velocity that Jupiter has). Flat space means
you feel no effects from gravity regards of your velocity. What the Lagrange
points are are stability points, so this does not mean that you feel no
gravitational acceleration, but it means if you have a certain velocity you
can just sit there without having to worry about straying away or constantly
working to keep your orbit.

Of course none of this has anything to do with Full Thrust or FTL. If you want
to have FTL from every possible Lagrange point, go ahead,
just don't say a Lagrange point has a flat space-time (you can,
however, say because its a meta-stable point in the on the
zero-velocity surface of the effective potential which ought to
impress the hell out of just about anybody.)

Further questions/comments/flames on this should go directly to me
instead of to the list.

cheers