A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Fred Hebard
Date: 2003 Aug 19, 15:19 -0400
On Tuesday, Aug 19, 2003, at 14:53 US/Eastern, George Huxtable wrote: > However, we have to keep a sense of proportion here. On weather maps, > isobars can wander all over the place. Conversely, if the Earth was a > uniform sphere, the equipotential shells would be exactly spherical, > and > so, as it happens, would be our equal-g contours. Even the ellipsoidal > effects caused by the Earth's spin give rise to changes which are less > than > 1%. And the hills and dips, that we've been discussing in such detail, > are > molehills on that ellipsoid. So the gravity variations that we have > been > discussing are small, and the surfaces of equal potential and the > surfaces > of equal gravity, though not spherical shells, are pretty damn near to > that. So, once again, just how big are these molehills? 200 meters is about .001% of the earth's radius, if my calculation is correct, which is pretty insignificant. But that would be a fair-sized skyscraper or hill.