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Antimatter Man
Join Date: May 2004
Location: that interweb thing
2011-04-05, 06:01

Gravity on Earth isn't the same everywhere... new map shows stronger (yellow) and weaker (blue) zones and a wacky potato shaped planet.

BBC story

It looks like a giant potato in space.

And yet, the information in this model is the sharpest view we have of how gravity varies across the Earth.

The globe has been released by the team working on Europe's Goce satellite.

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.


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 is where the pull of gravity is the same.

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 of rock is not evenly distributed.

The Gravity Field and Steady-State Ocean Circulation Explorer (Goce) was launched in March 2009.

Goce flies lower than any other scientific satellite
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.

"Ten years ago, Goce was science fiction; it's been one of the biggest technological challenges we have mastered so far in the European Space Agency," said Dr Volker Liebig, the organisation's director of Earth observation.

"We measure one part in 10 trillion; that's beyond what we understand in our daily experience."

An initial two months of observations were fashioned into a geoid that was released in June last year. The latest version, released in Munich at a workshop for Goce scientists, includes an additional four months of data. A third version will follow in the autumn. Each release should bring an improvement in quality.

... continues
Wonder if the Sri Lankan Olympic team jumps higher at home or needs to train in Papua New Guinea

All those who believe in telekinesis, raise my hand.