The above is a model of the Earth’s geoid constructed from data taken by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite that was launched in March 2009, released three days ago.
The geoid represents the equipotential surface of the Earth’s gravitational field 1, also the mean ocean surface of the Earth in the absence of external forces (tides, currents, winds) 2, also the surface such that the force of Earth’s gravity is always perpendicular to it 3, also “if you were to place a ball anywhere on this potato [geoid], it would not roll because, from the ball’s perspective, there is no “up” or “down” on the undulating surface” 4.
The geoid is useful as a standardized, global point of reference for comparing how external forces influence the local sea level.
The areas in yellow are higher in altitude than the reference ellipsoid model of the Earth, and those in blue are lower. These differences are caused by asymmetrical mass distribution over the volume of the planet (think density). This model has had those differences magnified “nearly 10,000 times” in order to look cool.
0 – http://www.esa.int/esaCP/SEM1AK6UPLG_index_0.html
1 – http://en.wikipedia.org/wiki/Geoid
2 – http://en.wikipedia.org/wiki/Sea_level
3 – http://geophysics.ou.edu/solid_earth/notes/geoid/earths_geoid.htm
4 – http://www.bbc.co.uk/news/science-environment-12911806 (I recommend this one)