Two identical satellites fly 220 kilometers apart above the Earth, firing a laser between them precisely enough to notice a change in distance smaller than the width of a red blood cell, and that flicker is how scientists now weigh the water moving beneath entire

Here’s the conclusion first, because it’s the part that still doesn’t feel like it should be possible: nobody photographs the water disappearing from an aquifer in California or the ice thinning unde… [Read Full Story on Space Daily →](https://spacedaily.com/a-two-identical-satellites-fly-220-kilometers-apart-above-the-earth-firing-a-laser-between-them-precisely-enough-to-notice-a-change-in-distance-smaller-than-the-width-of-a-red-blood-cell-and-that-flic/)