We Have Seen the Earth’s Gravity, and It Is … Lumpy
Following one year of gravitational data collection, the European Space Agency's GOCE satellite has produced what the ESA says is the most accurate model of the Earth's geoid ever produced. A geoid is, essentially, a surface that describes the way the Earth's oceans would shake out if there were no tides or currents and if the oceans could travel over continents: If gravity was all that mattered. (Wikipedia has a more rigorous definition.) As you can see in the animation above (h/t Bad Astronomy), it is quite a lumpy fellow. ESA:
[The geoid] is a crucial reference for measuring ocean circulation, sea-level change and ice dynamics – all affected by climate change. ... A precise model of Earth's geoid is crucial for deriving accurate measurements of ocean circulation, sea-level change and terrestrial ice dynamics. The geoid is also used as a reference surface from which to map the topographical features on the planet. In addition, a better understanding of variations in the gravity field will lead to a deeper understanding of Earth's interior, such as the physics and dynamics associated with volcanic activity and earthquakes.(ESA, Bad Astronomy via Cindy Au)Read on...
An HD Map of the Earth’s Gravity Field Helps Determine Planet’s Interior StructureNew satellite imaging from the Gravity field and steady-state Ocean Circulation Explorer, GOCE for short, has given us a much more detailed picture of Earth's gravity field, and thus a more accurate knowledge of the planet's geoid. The geoid is basically a depiction of the planet devoid of land masses, where the planet is pure ocean, shaped by the gravitational field. It's pretty lumpy. After all, Earth is by no means a perfect ellipse, so the planet's gravitational field isn't either. The image below is representative of our current knowledge, and a much more detailed version will be able to be created from the GOCE's data. The image above was the result of only two months of gathering, so in a short time we will have an even more detailed sense of the Earth's gravitational field and be able to create an analglyph better than that below.Read on...