Satellite to begin gravity quest

There is a misconception that the Earth's pull is the same everywhere. In reality, it differs ever so slightly from place to place.
One of the reasons is that our planet is not a perfect sphere - it is flatter at the poles, fatter at the equator. Its interior layers are also not composed of uniform shells of homogenous rock - some regions are thicker or denser.
Although the variations in the gravity field are subtle, they have an important influence on many Earth systems.
Without a sense of how gravity helps pull water from one location to another, scientists cannot have a full understanding of ocean currents.
And without knowing where gravity shifts mean sea-level from location to location, scientists cannot properly compare the heights of objects, such as the mountain ranges on different continents.
GRAVITY FIELD AND STEADY-STATE OCEAN CIRCULATION EXPLORER

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