Earth’s roundness is obvious to any who care to observe, but the fact that Earth spins on its axis is not as apparent. French physicist Leon Foucault wanted to remedy this situation so that the masses could experience Earth’s rotation with their own eyes. To do so, he built a 67 meter long pendulum in the Pantheon in Paris, France. The point being that the pendulum not only bobs back and forth but also rotates as well. This phenomenon is of course due to the rotation of our planet. What’s happening is that, because the pendulum bobs and rotates regardless of our planet's rotation, it remains fixed while Earth beneath it spins. So to anyone who’s attached to and therefore spinning with our planet, it’s the pendulum that rotates and not Earth. So through this simple experiment we can experience indirectly the rotation of our planet. This phenomenon is easy to visualize when we are at the poles. But not as easy in between the poles, because in between the poles, our pendulum is flung around Earths axis. So it’s not clear what “fixed” means in this context. In this video we help you visualize why the pendulum spins in between the poles using visual aids. Circles, cones, lines to be exact. We also show you how to derive the equation that predicts how long it takes for the Foucault Pendulum to rotate at any given latitude. A little bit of math but totally worth it.

If your interested here's an in depth paper on the subject: A simple geometric model for visualizing the motion of a Foucault pendulum, John B. Hart, Raymond E. Miller, and Robert L. Mills, American Journal of Physics 55, 67 (1987)

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00:00 – Intro
00:24 – At the Poles
01:08 – In between Pole and Equator – Cone Method
03:49 – Equation for Rotation Time
04:45 – At Equator
05:07 – Conclusion

#foucaultPendulum #roundEarth #flatEarth #3danimation #pendulum #coriolis

BG Music: Original Music "Curiosity's afoot" by Stick Science

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