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: Where is Earth's center of mass? The answer seems trivially obvious.
It's right in the middle of the planet. Ah, but that kind of thinking won't get you a paper in the Geophysical Journal International. It's also not a trivial question.
Knowing Earth's center of mass to within millimeters reveals some interesting facts about our planet. To measure Earth's center of mass accurately, we must look to space. Satellites don't just orbit Earth; they orbit the exact center of Earth's mass.
Any small shift in that center of mass means there is a shift in orbital trajectories. All you have to do is measure the orbits precisely. Back in the 1980s and 1990s, this was done using satellites known as LAGEOS.
These spherical satellites were covered in reflective panels so that ground-based laser observatories could measure their positions over time. This allowed us to determine the center of mass to within a centimeter or so. This new study improves accuracy by using GPS data to account for tiny shifts in the locations of ground-based observatories.
It also adds data from a host of low-orbit satellites to improve accuracy even further. The result reduces uncertainty to less than a millimeter. Some of the results are what we expected.
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