The Foucault pendulum is considered one of the most elegant experiments in the world of Physics, as it demonstrates the Earth’s rotational movement.
It is called the Foucault pendulum in honor of its inventor, Jean Bernard-León Foucault, a French physicist.
History
The first time this pendulum was seen was in 1851, at the Pantheon in Paris, where its inventor hung a 28 kg iron ball from the dome of the building, supported by a 67-meter-long steel cable.
Thus, those observing this pendulum noticed that the direction in which the pendulum oscillated slowly rotated clockwise. This rotation is due to the Earth’s rotation.
Explanation of this phenomenon
The operation of this pendulum lies in the fact that it is not its plane of oscillation that rotates, but rather it continues oscillating in the same direction, without changing.
If we were to observe it from space, we would see that the pendulum does not rotate; it remains on the same axis.
However, since we are on Earth, we rotate with it (Earth’s rotation) and observe the pendulum as if it were constantly rotating, but this is not the case.
In other words, the pendulum does not rotate, but rather we are the ones rotating along with the Earth.
Does friction affect the pendulum?
Yes, or at least it should. To prevent this, a special device, including an electromagnet, is placed at the top of the cable to compensate for the energy loss due to friction. This way, the pendulum never stops.
But, is the pendulum a clock?
It might seem so, but the reality is that, depending on the location on Earth, it would rotate at a different pace (depending on the latitude), making it impractical.
For example, at the North Pole, the pendulum would complete a full rotation every 24 hours approximately. However, in Paris, it takes a little over 32 hours, and in Valladolid (Spain), it would take about 36 hours. Thus, we conclude that the lower the latitude where the pendulum is located, the slower the oscillation plane of the pendulum rotates.
At the Equator, it remains oscillating in the same plane, as it does not rotate.
Explanatory video from the Science Museum of Valladolid
To write this article, I relied on the following video published by the Science Museum of Valladolid, where they explain in a very educational way how the Foucault pendulum displayed in their museum works.
