Do you know the story of Foucault's pendulum?

Among the various pantheons that exist around the world is that of Paris. It was built in the 18th century as a church, named after Saint Genoveva, but currently serves as a mausoleum for great French personalities such as Marie and Pierre Curie, Voltaire, Jean Jacques Rousseau and Victor Hugo. Today the place looks much more like a museum, without an altar but with a large pendulum stuck in the center of its dome - which was used by Foucault to prove that the earth revolves around its own axis.

Foucault pendulum

The discussion of which model of the Solar System was real - geocentric (with the sun moving around the earth) or heliocentric (the earth moving around the sun) - lasted a few centuries. Along with the lack of technology and knowledge, there was the Church, which did not accept the new theories and tried very hard to maintain its worldview.

For her, the earth was the center of everything, a fact that was accepted for a long time. Only with the research and effort of the great names of science, such as Nicholas Copernicus and Galileo Galilei, has the accepted model been changed to heliocentrism. This issue has been thoroughly debated, but the search for evidence of the earth's rotation around its axis has been set aside.

Who found a way to prove this movement was the French experimental physicist and astronomer Jean Bernard Léon Foucault. The method was accidentally discovered when he realized that the pendulum of a clock was not influenced by the movement of the surrounding structure as long as the fulcrum remained fixed.

Free spin

Foucault realized that by letting a pendulum swing beyond its expected motion, it would rotate - caused by the movement of the earth around its axis. Through calculations, he determined that the period of this rotation was directly influenced by the latitude of the location where the measurement was made.

At the poles, the movement would take exactly 24 hours and exactly on the equator line there would be no circular motion, with the pendulum always going back and forth on the same line. In January 1851, the physicist held a demonstration of his discovery for the first time for members of the Paris Academy of Science. The fact caught the attention of the French leader at the time, Napoleon Bonaparte, who ordered the execution of a public experiment in the Pantheon of Paris.

At the time, a 28-pound pendulum was attached to the center of the dome, attached by a cable measuring 67 meters. The large public that attended the event could see the movement through a graduation positioned in the center, making the discovery popular throughout Europe.

The possibility of proving something so grand stoked society's imagination, so much so that the experiment was replicated around the globe at public and private events by researchers and ordinary people. In an article he wrote about the repercussions of the discovery in the US, Michael Conlin said that “Foucault's pendulum's popularity was a result of its highly visual effect, its illustration of a physics principle, its use of readily available apparatus and its ability to fascinate observers. ”

Since there was a strong resistance from the Church to accept new discoveries about the interaction between planets and stars, using a sacred place for the public demonstration of the test was quite symbolic. Today the issue is no longer a problem, as there are several churches where you can see a Foucault pendulum in motion, such as St. Isaac's Cathedral in Russia or St. Peter's and St. Paul's Church in Poland.

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