140. Foucault's pendulum motion has nothing to do with the rotation of the Earth

"Foucault’s Pendulums are often quoted as proof of a rotating Earth but upon closer investigation prove the opposite. To begin with, Foucault’s pendulums do not uniformly swing in any one direction. Sometimes they rotate clockwise and sometimes counter-clockwise, sometimes they fail to rotate and sometimes they rotate far too much. The behavior of the pendulum actually depends on 1) the initial force beginning its swing and, 2) the ball-and-socket joint used which most-readily facilitates circular motion over any other. The supposed rotation of the Earth is completely inconsequential and irrelevant to the pendulum’s swing. If the alleged constant rotation of the Earth affected pendulums in any way, then there should be no need to manually start pendulums in motion. If the Earth’s diurnal rotation caused the 360 degree uniform diurnal rotation of pendulums, then there should not exist a stationary pendulum anywhere on Earth!"

Dubay lies again and makes some more irrelevant points

Sometimes they rotate clockwise and sometimes counter-clockwise

Foucault pendulums rotate anticlockwise in the Southern Hemisphere and clockwise in the Northern Hemisphere. This is exactly as we expect on a rotating spherical Earth.  If this is what Dubay meant  then he is just confirming that Foucault pendulums behave as we expect  on a rotating spherical Earth.

If Dubay meant that there are Foucault pendulums that rotate clockwise in the Southern Hemisphere and anticlockwise in the Northern Hemisphere he really should give at least one example that we can check or at least provide a video of a properly conducted experiment.  As he has not I humbly suggest that he is once again making stuff up.

You can always check for yourself.  Follow the link to find where you can see a Foucault pendulum in action.

https://en.wikipedia.org/wiki/List_of_Foucault_pendulums

The behaviour of the pendulum actually depends on the initial force beginning its swing

Of course ...  if you push the pendulum in an inappropriate motion it can move in the wrong direction.  That is why when conducting the experiment great care is taken not to give the pendulum a sideways motion.  This is usually done by securing the pendulum with a thread and then burning the thread to release it.

Although Dubay doesn’t mention it, it is true that most science museum Foucault pendulums have a mechanism at the top to give the pendulum a gentle push to keep it going.  Without this the pendulum would gradually slow down due to air resistance and have to be restarted.

Conspiracy theorists can no doubt use this to imply that the mechanism is pushing the pendulum in a circle and that all the science museums around the world that host Foucault pendulums are part of a conspiracy to falsify the experiment.  The list of conspirators grows and grows.

You can of course try the experiment yourself as many people have (not including Eric Dubay)

The behaviour of the pendulum actually depends on  the ball-and-socket joint used which most-readily facilitates circular motion over any other

The whole point of this pendulum is that it is free to swing in any direction. A ball and socket joint can do this but it is false to claim that it favours a circular motion.  In order for an object to move in any direction a force needs to be applied.  Perhaps Eric Dubay could explain the force that a ball and socket joint exerts and how.

In any case, you do not need such a joint.  See the following link where a cable firmly just clamped into place is used.

If the Earth’s rotation caused uniform rotation of pendulums, then there should not exist a stationary pendulum anywhere on Earth

Dubay is just misunderstanding the experiment.  No-one is claiming that the rotation of the Earth is causing the pendulum to move.   That happens because of an initial push.  The rotation of the Earth only affects the direction of the swing relative to the Earth.

The following animation shows what is happening.  Note the rotation is greatly exaggerated.

Source: https://en.wikipedia.org/wiki/Foucault_pendulum

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