18 April 2011

Gravity's Ups and Downs: New map released showing earth's pull

The earth is anything but a smooth sphere. Mountains, valleys, ocean canyons, and expansive deserts give the globe we call home a lumpy, uneven appearance. A newly produced map shows that the strength of earth's gravity varies widely across the planet, as demonstrated in the uneven multicolored sphere called a geoid.

The geoid, a globe showing variations in gravity across the planet

A geoid demonstrates the average (mean) surface level of a hypothetical global ocean as if the earth were stationary. Devoid of other forces such as rotation, wind, and tides, water would 'pile up' in areas with higher gravity while lower gravity areas would result in ocean 'valleys.'

1. Ocean 2. Ellipsoid 3. Local plumb 4. Continent 5. Geoid
Image credit: MesserWoland

This detailed gravity map is due to a new European satellite called the "Gravity field and steady-state Ocean Circulation Explorer." The GOCE, as it is sometimes called, collected data over thousands of orbits to produce a geoid of unprecedented accuracy and completeness.

A detailed geoid of earth is important for many reasons. It enhances the prediction of ocean and air currents. Movement of melting glaciers can be more accurate mapped because we can now account for gravity's varying effects. And perhaps most importantly, the geoid offers geologists more information which can be used to find out more about the earth's internal structure.

Read National Geographic's post here

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