When Foucault set up his experiment in The Panthean in Paris in 1851 why did the plane of the pendulum change 11 degrees in the first hour not 15 degrees as I would have expected.
15 x 24 = 360 degrees!
Always stuff I don,t understand.
Mike.
What is the latitude of Paris?
http://en.wikipedia.org/wiki/Foucault_pendulum
To understand why the plane of the pendulum changed 11 degrees in the first hour instead of 15 degrees, we need to consider a few factors. One important factor is the latitude of the location where the experiment was conducted, which in this case is Paris.
The latitude of Paris is approximately 48.9 degrees north. The rotation of the Earth causes objects, including pendulums, to experience a deflection due to the Coriolis effect. The amount of deflection depends on the latitude of the location.
In the case of the Foucault pendulum experiment in Paris, the deflection is determined by the sine of the latitude multiplied by the rotation rate of the Earth. The rotation rate of the Earth causes the pendulum's plane to rotate counterclockwise.
In Paris, the deflection due to the Coriolis effect is approximately 11 degrees per hour. This means that the plane of the pendulum would change by 11 degrees in the first hour of the experiment.
The reason why you were expecting a change of 15 degrees per hour is likely due to a common misconception or confusion with the full 360-degree rotation of the pendulum over a 24-hour period. However, it's important to note that the deflection per hour is not a constant 15 degrees but depends on the latitude of the location.
In summary, the plane of the pendulum changed 11 degrees in the first hour because of the deflection caused by the Coriolis effect at the latitude of Paris, which is approximately 48.9 degrees north.