According to the principle of equivalence, local experiments, in all freely falling frames of reference, are independent of the gravitational field surrounding this frame. A simple experiment, in which Einstein’s freely falling elevator is replaced by a pendulum system sliding down an inclined plane, serves as a demonstration for this principle. The pendulum experiences a force orthogonal to the inclined plane. With an eddy current damping mechanism, the oscillation of the pendulum can be damped, and the pendulum will move into its equilibrium position orthogonal to the inclined plane shortly after being released from rest.

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