On Mon, Jul 10, 2000 at 11:18:53PM -0400, Bob Bernstein wrote:
> On Mon, Jul 10, 2000 at 08:02:16PM -0700, Eric G . Miller wrote:
> > It is approximately round (spherical). A better approximation is made
> > with an ellipsoid (rather than a spheroid).
> The Clarke Geoid of 1866 (perhaps our first modern geoid) was an ellipsoid.
> Physically though, earth resembles more an oblate spheroid.
Yep, that Clark 1866 model works pretty good for the Americas. Just
curious, how is an oblate spheroid different from an ellipsoid? Does it
account for the differential flattening between the northern and
southern hemispheres? Or does it just not satisfy the equation for an
ellipse rotated about its minor axis? Interesting stuff, this quest for
the "shape of the earth".
AFAIK, the Earth Gravitational Model of 1996 is
one of the best models of the Earth -- not to easy to work with
computationally, though ;-) Guess there's a grid approximation of it...
According to MegaHAL:
The emu is a mass of incandescent gas, a gigantic nuclear furnace.