SPRAGGETT ON CHESS
MAPPING THE PULL OF GRAVITY ON THE SURFACE OF THE EARTH
It is amazing what satelites armed with the latest technologies are discovering about our planet. The team behind Europe’s Goce satelite has released some stunning imagery of the earth. The Gravity Field and Steady-State Ocean Circulation Explorer (Goce) was launched in March 2009.
It flies pole to pole at an altitude of just 254.9km – the lowest orbit of any research satellite in operation today.The spacecraft carries three pairs of precision-built platinum blocks inside its gradiometer instrument that can sense fantastically small accelerations.
This extraordinary performance allows it to map the almost imperceptible differences in the pull exerted by the mass of the planet from one place to the next – from the great mountain ranges to the deepest ocean trenches. Just getting it to work has tested the best minds in Europe.
”It is a highly exaggerated rendering, but it neatly illustrates how the tug we feel from the mass of rock under our feet is not the same in every location.
Gravity is strongest in yellow areas; it is weakest in blue ones. Technically speaking, the model at the top of this page is what researchers refer to as a geoid.
It is not the easiest of concepts to grasp, but essentially it describes the “level” surface on an idealised world.
Look at the potato and its slopes. Put simply, the surface which traces the lumps and bumps defines the horizontal – it traces a surface on which, at any point, the pull of gravity would be perpendicular to it.
Described another way, if you were to place a ball anywhere on this potato, it would not roll because, from the ball’s perspective, there is no “up” or “down” on the undulating surface.
It is the shape the oceans would adopt if there were no winds, no currents and no tides.
The differences have been magnified nearly 10,000 times to show up as they do in the new model.
Even so, a boat off the coast of Europe (bright yellow) can sit 180m “higher” than a boat in the middle of the Indian Ocean (deep blue) and still be on the same level plane.
This is the trick gravity plays on Earth because the space rock on which we live is not a perfect sphere and its interior mass is not evenly distributed.”
SPRAGGETT ON CHESS