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Galileo's Pendulum

What is weight?

8 Jul 2013, 14:44 UTC
What is weight?
(200 words excerpt, click title or image to see full post)

There then occurred to me the “glückischste Gedanke meins Lebens,” the happiest thought of my life, in the following form. The gravitational field has only a relative existence . . . . Because for an observer falling freely from the roof of a house there exists — at least in his immediate surroundings — no gravitational field.
– Albert Einstein, as quoted by Abraham Pais

Canadian astronaut Chris Hadfield aboard the International Space Station (ISS), demonstrating weightlessness with tomatoes. [Credit: International Business Times]Weight is not the same thing as the gravitational force. You don’t need a formal study of physics to know that: all you have to do is ride a swing at a playground, or drive over the lip of a hill a little too fast, or ride an elevator on a tall building. In all of these cases, you experience fluctuations in your weight: heavier at the bottom of the swing’s arc, lighter at the top, maybe even momentarily weightless. The elevator is the best example of these, since you could take a scale onto it and see how your weight changes during the various stages of acceleration. (Try it at the Sears Tower or Empire State sometime. ...

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