The gradients seem less marked over the oceans where a lot of gravity field information has already been determined by spacecraft that measure sea-surface topography.

BBC: Europe's Goce satellite probes Earth's gravity

They predict that about 73% of the Universe is made up of dark energy - a pervasive energy field that acts as a sort of anti-gravity to stop the Universe from contracting back in on itself.

BBC: Dark Matter: Experiment to shed light on dark particles

At Oort-cloud distances, the strength of this combined gravity adds up to the same sort of force as that exerted by the solar gravitational field, enfeebled as it is by its remoteness from the sun.

ECONOMIST: X marks the spot

In World War I the Allied strategy was to engage and defeat the center of gravity of the Central Powers, the German field army.

FORBES: World War I's Crucial Lesson for Today's Leaders

This has allowed scientists to retrieve information about the Arctic Ocean region's gravity field, its surface circulation, and the thickness of its sea-ice cover.

BBC: Cryosat spots Arctic sea-ice loss in autumn

In a culture that encourages the constant search for the limits of human achievement, we, the fans, the consumers of popular sports entertainment, revel in record-breaking, gravity-defying, barely believable feats on the field of play.

CNN: Opinion: It's time to allow doping in sport