Re: The GZG Digest V2 #1753

Roger Burton West wrote:
> 
> On Fri, Oct 03, 2003 at 10:50:43AM -0400, laserlight@quixnet.net
wrote:
> >>Also would be useful to remember the Lagrange 1 point (between the
Earth and
> >Moon, or the Sun and the Earth, &cet.), where the local gravitational
force
> >is essentially null. There would be a region around this point where
the net
> >force would be beneath the threshold you specify. These points exist
> >throughout the solar system, and are in constant motion! Have fun...
:-)
> >
> >Good throught!  Hadn't occurred to me at all--you win today's Sneaky
Player award.
> 
> Well, the Lagrange points aren't exactly points of neutral gravity;
> they're points of balance between gravity and centripetal force. (And
> L1-L3 are "peak" points, i.e. something put there will drift away,
where
> L4-L5 are "troughs" and will correct small drifts.)

One additional note, Lagrange points are not "points" at all, but
vast areas (by vast I mean larger than Earth; I had the rough area
for the L2 position once but have forgotten it). Going off of FT
specific and into a side note on the real, the JWST (what the Next
Generation Space telescope is now called) will be put out at the
L2 position. It won't stay in one place, but rather will draw out
lazy figure 8s. The L2 area is 4x the orbit of the Moon is to Earth,
in the opposite direction to that of the Sun (I have a rough scale
jpg that I put together earlier this spring that I've used for several
poster papers and presentations on another project I'm involved in; you
can see this jpg at: ftp://ftp.stsci.edu/tmp/kochte/earth_sun_L2.jpg)

Also, another note you'll want to maybe consider is that the Lagrange
"points", being a balanced area as Roger described above, will have
collected "debris" over time. Very likely nothing overly large (like
an Earth-killer asteroid), but enough to make a nuisance of itself for
small craft (and potentially affecting spaceships jumping in/out of
a system using the area?)

> There is, for any pair of bodies, a point where the gravitational
> attractions of the two cancel out - the ratio being that of the square
> roots of the masses. For Earth-Sun, I make this about 260,000km from
the
> centre of Earth.

And at that distance you'll need to add in the effects of the Moon.
;-)

Mk