This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Seasonal changes redistribute enough water around Earth to shift the planet's center of mass back and forth by fractions of an inch relative to its geometric center. NASA scientists are on the case, tracking the oscillations because Earth's center of mass is a crucial reference point for satellite navigation and elevation measurements.
A team led by NASA's Jet Propulsion Laboratory in Southern California has proposed a way to calculate the seasonal swings with extreme precision. The technique and findings are detailed in a new study published in Geophysical Journal International. The authors paint a vivid picture of springtime thaws, churning oceans and dense winter air shifting massive surface loads from season to season.
The study isn't the first attempt to pin down Earth's center of mass. Scientists over the decades have pioneered several space-based techniques to define and locate it. But it's a moving goalpost.
If Earth were a hard blue marble, its center of mass would simply overlap its geometric center. In reality, the planet is sloshing and sagging under the weight of water, ice and air. Because of this, Earth's center of mass continually swivels around its geometric center by as much as several millimeters.
How accurate are existing methods to measure the size of the swivel? The last two international estimates, made in 2017 and 2023, differ by 0.27 inches (7 millimeters), about the height of three stacked nickels. The difference is almost as large as the motion itself.
To reduce uncertainty, JPL geoscientist Donald Argus led the development of a new technique based on ultraprecise satellite tracking. Driven by gravity, satellites naturally orbit Earth's center of mass, as if bound by invisible tethers. Tiny changes in the distance between satellites and ground stations reflect Earth's shifting center of mass.
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