Feature

Mapping with GRACE

Twin satellites chart changes in Earth's gravitational field

By
9:57am, December 19, 2002

Concerned about your weight? Don't go to the North Pole, where you're about 20 km closer to the center of Earth–and therefore a pound or so heavier–than at the equator. Head, instead, for India. There, you'd be standing over a less-dense landscape with a gentler gravitational pull. Yes, what you weigh depends on where you are. Your body doesn't change from place to place, but the gravitational field does. Topography, crust composition, and the planet's rotation-induced equatorial bulging are among the factors that influence Earth's gravitational pull at different locations. Furthermore, this uneven gravitational field changes slightly with the seasons, as precipitation carries moisture's mass from the oceans onto the continents.

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