Hi, I rather a strange question in that I'm not a physicist and don't really understand the theories I'm about to mention fully, ok disclaimer over. My understanding of gravity, is that a mass warps the spacetime in which it sits. Now my question is that ESA's Gravity field and steady-state Ocean Circulation Explorer (GOCE) shows gravity isn't equal all over the earth. Surely then that means spacetime isn't distorted uniformly around the earth? Surely this would have an effect on an object depending on the position of the earth at the time flyby? Ok maybe not quite such daft a question, but I'm sure there will be a physicist somewhere shaking their head ... :) Mark I think in fact I mean the GRACE project not GOCE.