"The satellites orbit the earth and sends out thousands of radar pulses a second," Sandwell, a geophysics professor at Scripps. tells Popular Science. "So we use that data to generate a topography of the ocean's surface." That topography highlights subtle variations and bumps in the oceans' waters, telling a lot about the surface underneath. For example, if the ocean is slightly raised at one point, it serves as an indication of a larger object below.