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Month Index: March, 1995

From:     Eugene Shumu1insky <static@??.???.????.edu>
Date:     Wed, 22 Mar 1995 22:33:38 -0500 (EST)
Subject:  Re: Gravity revisited...
	Hello all...

	I know this topic has been touched upon *many* times, but I'd like
to talk about gravity.  I'm currently working on converting SJ to GURPS, and
I thought that I'd start posting chuncks as I finished them for critique.
My WWW page ( has the nicely formatted stuff,
plus a bit of extras, but I thought I'd post here also.
	I'm currently working on air envolpes and stuff, so if anybody,
especially biology types, can tell me anything about how much air the
human body needs on average, etc, I'd be greatful.


------ Cut here ------


Gravity is the force which keeps everything "down".  That we already know.
What follows is an explanation of how it works in fantasy space... (This
part assumes a working knowledge of binary gravity and gravity planes.)

First, some basic facts:
 - A gravity plane's "reach" is a bubble which is about three times the size
of an object, with the object at its center.
 - Planer and axial gravity tends to be about Earth-normal.
 - Planer and axial gravity "breaks down" for very large (2 - 3 miles on an
axis) objects.  It simply collapses in on itself, becoming...
 - Spherical gravity takes over where planer gravity starts to fail, but
its strength tends to vary on the objects size.  Strength depends on an
objects size and density.  (Just like in real life!)
 - Spherical gravity isn't binary.  It actually allows objects to orbit,
unlike planer gravity, and follows what we consider to be "normal" physics.

Let's start with the placement of the gravity plane.  Gravity planes form
around any object with at least one axis of around twenty feet (6 - 7 yards).
This gravity plane
seems to fall in the direction "which is most convenient".  That's all good
and well, but what exactly does it mean?  It means that the gravity plane,
or gravity axis in some cases, will fall through or along the center mass.
Long thin ships have to be constructed very carefully to distribute the mass
along a flat plane, otherwise gravity may end up being axial.  A very tall
flat ship could even end up with a "vertical" (to its own "floor") gravity
plane!  A heavily loaded ship's gravity plane would also shift, which could
cause problems.  The point is that this gravity plane (or axis) may not
always fall in a way that is most convenient for the ship designers.

To solve this problem, certain magics were developed to keep the gravity
plane bound to a specific surface.  These magics also adjust the plane
to give it a more "Earth normal" feel.  (Note: The spell or spells involved
are at level of power that is not too common, but at the same time not rare.
I may actually write them up for GURPS and/or AD&D at some point.)  Gravity
planes are usually bound to the lowest floor or deck of the ship, to keep the
gravity from flipping at takeoff and landing.

Objects left floating along the gravity plane will slowely drift in
towards the "center" of the plane.  This effect is probably due to
gravity's nature of becoming spherical around large bodies.

A misconception about planer gravity is that it's truly binary, either on
or off.  This is not quite true.  Along the gravity "edge" there is a fringe
zone where gravity drops of very quickly.  This area is only a few feet wide
on smaller objects, but grows as the object becomes larger.  Where large
ships and small asteroids have fringe zones of up to several yards.  This
is also due to gravity's spherical nature as objects get bigger.

Hopefully this information will help clear up certain inconsistencies in
the current theories.

Comment and complaints welcome...

-------Cut ------

Let me know if there's anything you have to add.  Also, any thoughts on other
aspects of SJ (helms, air, ship design) that you have an idea about, please
let me know about it.

  Static        |            Sleep all day.  Party all night.
    on the      |              Never grow old.  Never die.
      silicon   |               It's fun to be a vampire.
        web.    | (RPG, MtG, and more...)

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