Earth's center of mass drifts half as much as thought

Researchers pinned down Earth's center of mass to within less than a millimeter using GPS data and low-orbit satellites. The seasonal drift turned out to be about half of earlier estimates, suggesting less water and air move between hemispheres.

• Accuracy improved from centimeters to less than 1 mm
• Seasonal drift is about half of previous estimates
• Method combined GPS data with low-orbit satellite tracking
• Long-term shifts from volcanoes and earthquakes also measured