The Russian State Commission has given the green light for the launch, in just a couple of hours, of a sophisticated satellite to investigate the Earth’s gravitational field. The Gravity field and steady-state Ocean Circulation Explorer (GOCE), a European Space Agency (ESA) project is to be launched today at 15:21 CET.
GOCE data will let us accurately measure sea-levels and ocean circulation, which are affected by climate change. So what? you say.
Well, we all know the Earth (like all objects with mass) results in gravity. However, the effect of gravity depends on the amounts of mass involved and on the distance away from the mass. Although it’s usually sufficient to think of the Earth as a big round ball, it is in fact neither a perfect sphere on macro (a big sphere in space) nor micro (hills and valleys and seabeds) levels. Neither is its mass distributed uniformly around the globe nor through the layers of its interior. Thus, gravity varies around the surface of the globe.
If we want to get down to the nitty-gritty of the dynamic processes taking place on Earth’s surface and in its interior – sea level changes due to climate change, seismic activity, etc – we need the nitty-gritty detail of how gravity varies around the world. An accurate gravity map – called a geoid – thus becomes an important thing to understand.