"Europe's Goce satellite is returning remarkable new data on the way the pull of gravity varies across the Earth...
The instrument is sensitive to accelerations of about one-tenth of a millionth of a millionth of
g.
And the gradiometer measures these accelerations across all three axes of the spacecraft to obtain a multi-dimensional view of the Earth's gravity field..."
http://news.bbc.co.uk/2/hi/science/nature/8408957.stm
1. Goce senses tiny variations in the pull of gravity over Earth
2. The data is used to construct an idealised surface, or geoid
3. It traces gravity of equal 'potential'; balls won't roll on its 'slopes'
4. It is the shape the oceans would take without winds and currents
5. So, comparing sea level and geoid data reveals ocean behaviour
6. Gravity changes can betray magma movements under volcanoes
7. A precise geoid underpins a universal height system for the world
8. Gravity data can also reveal how much mass is lost by ice sheets