Tuesday, 5 April 2011

The Shape of the Earth

Roundish, obviously. And constantly changing shape, due to weathering, tidal forces, moving masscons in the mantle causing gravitational effects, plate tectonics... even relativistic curdling of spacetime due to rotation.

But roundish. Quite close to a spheroid. But what about the Geoid, the notional surface of gravitational equipotential, after removing tidal effects etc?

From ESA Portal - Earth's gravity revealed in unprecedented detail - images:
ESA's GOCE mission has delivered the most accurate model of the 'geoid' ever produced, which will be used to further our understanding of how Earth works.

The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid. The blue colours represent low values and the reds/yellows represent high values.

The geoid is the surface of an ideal global ocean in the absence of tides and currents, shaped only by gravity. It is a crucial reference for measuring ocean circulation, sea-level change and ice dynamics – all affected by climate change.

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