When you use your phone to get directions, you're most likely using GPS. These systems rely on an accurate calculation of the Earth's geocenter, or the center of mass of the Earth. But Earth's geocenter is constantly changing. By using a network of ground telescopes and lasers that fire pulses at specific satellites, scientists can calculate where the geocenter of the Earth is within a few millimeters to ensure our Earth observations are accurate. 🌏 🛰️ 🔭 https://go.nasa.gov/3iLqHat | NASA Ear