Equivalence Principle: In this video Paul Andersen explains how inertial mass and gravitational mass are equivalent. He shows you too simple methods for calculated individual inertial mass and gravitational mass. Albert Einstein used this principle to build his general theory of relativity.

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principe d'equivalence

The equivalence principle is key to understanding that light is deflected by gravity, and to understanding gravitational redshift.

Uniformly Accelerating Charged Particles: A Threat to the Equivalence Principle

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Einstein's Equivalence Principle Put to Test, Discovery News | 5/6/16 An orbital experiment is about to test to see if objects really fall at same speed in a gravitational field — or if some exotic physics may be detected.

THE EQUIVALENCE PRINCIPLE: -->

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Illustration of the equivalence principle, showing a caricature of Einstein in freefall with with a scale and ball floating nearby (left) and a caricature of Einstein standing on a scale with a weight of ~140 lbs, with a ball falling nearby (right)

During ten seconds of weightlessness Brynle Barrett from the Laboratory of Photonics, Numerical Sciences and Nanosciences at the University of Bordeaux monitors an experiment to test the ‘weak equivalence principle’ – or why a feather in a vacuum falls as fast as a hammer.

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