Zero-G Indicator

When Crew 5 rocketed to orbit last week aboard the SpaceX Dragon “Endurance” bound for the International Space Station, I was curious to see their zero-gravity indicator. A tradition SpaceX crews have adopted from Russian cosmonauts, the zero-g indicator is usually a stuffed animal whose first float announces the free-fall of Earth orbit. Was that a plush Einstein doll?

On orbit, Crew 5 pilot and physicist Josh Cassada explained that the doll demonstrated Einstein’s happiest thought, that people falling can not feel their own weight. This insight, essentially the equivalence of inertial mass and gravitational charge, permits gravity to be interpreted as geometry in the theory of general relativity, still our best description of gravity. Crew 5 is experiencing Einstein’s happiest thought not merely momentarily but continuously!

Einstein doll zero-g indicator floats (top right) aboard the SpaceX Crew Dragon "Endurance" illustrating Einstein's happiest thought. ( NASA TV)

Einstein doll zero-g indicator floats (top right) aboard the SpaceX Crew Dragon “Endurance” illustrating Einstein’s happiest thought. (NASA TV)

About John F. Lindner

John F. Lindner was born in Sleepy Hollow, New York, and educated at the University of Vermont and Caltech. He is an emeritus professor of physics and astronomy at The College of Wooster and a visiting professor at North Carolina State University. He has enjoyed multiple yearlong sabbaticals at Georgia Tech, University of Portland, University of Hawai'i, and NCSU. His research interests include nonlinear dynamics, celestial mechanics, and neural networks.
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