Tag Archives: spacetime

The rubber sheet gets the geometry right and the mechanism wrong!

You have seen this demonstration. Somebody stretches a rubber sheet over a frame, drops a bowling ball in the middle, and the sheet sags. Then they roll a marble across it and the marble curves toward the bowling ball, maybe … Continue reading

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Deriving the Euler–Lagrange Equation for Particles, Fields, and Curved Spacetime

A good way to understand the laws of motion is not to memorize a separate equation for each situation, but to notice there is really only one trick, and every equation of motion is what falls out when you apply … Continue reading

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