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Why Riding An Elevator Is Like Changing Gravity

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A long time ago, in between undergrad and grad school, I had a job as a New York City foot messenger.

It was pretty cool. I got to know the subway system with startling accuracy. I delivered stuff to Annie Leibovitz's studio weekly. And I got to peer into the lives of many an investment bank.

But the best part of the job was the elevators — those long, high-speed elevator rides.

Being a physics student, I knew about Albert Einstein's famous recognition that riding on an upwardly accelerating elevator would be the same as feeling the "force" of gravity while being stationary on a planet's surface. It was this equivalence that led him to key parts of the General Theory of Relativity.

Being the dork that I was, I kept a red ball with me — so that every time I got on an elevator, I could toss it upwards at the exact moment the elevator accelerated upwards or downwards. If I caught it just right, the ball would seem to hang in the air for a moment, like gravity had been canceled.

Everyone else in those workday elevators thought I was nuts — but it always blew my mind.

To illustrate the point I was trying to work out back then, here is a great video from the . As is often the case, I initially found this video on the great site The Kids Should See This.

Adam Frank is a co-founder of the 13.7 blog, an astrophysics professor at the University of Rochester and author of the upcoming bookLight of the Stars: Alien Worlds and the Fate of the Earth. His scientific studies are funded by the National Science Foundation, NASA and the Department of Education. You can keep up with more of what Adam is thinking onFacebook and Twitter:@adamfrank4

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Adam Frank was a contributor to the NPR blog 13.7: Cosmos & Culture. A professor at the University of Rochester, Frank is a theoretical/computational astrophysicist and currently heads a research group developing supercomputer code to study the formation and death of stars. Frank's research has also explored the evolution of newly born planets and the structure of clouds in the interstellar medium. Recently, he has begun work in the fields of astrobiology and network theory/data science. Frank also holds a joint appointment at the Laboratory for Laser Energetics, a Department of Energy fusion lab.