zondag 17 november 2013

The Earth rotates (except in Copenhagen)

Last week, I was visiting the beautiful capital of Denmark, Copenhagen. I was selected to participate in the International PhD Elite Course "Tectonics" at the University of Copenhagen (READY program), organized by Prof. Hans Thybo and Prof. Irina Artemieva. During this five day course, the participants (PhD students from all over the world and me :) ) were being taught by two experts in the field of tectonics, the wonders of geosciences. From Geology (I write Geology, because it was defined by the lecturer as one of the two only real sciences); Prof. Çelal Şengör from Turkey with a beautiful British-sounding way of lecturing. From Geophysics (capital G, because I disagree with Prof. Şengör ;)); Prof. Seth Stein from the USA, who also brought his wive, Carol Stein. She gave a very interesting view on the Mid-Continental Rift. These last five days were fantastic, because I learned a lot and met numerous interesting people. I recommend any PhD student participating in such a course. It will enlighten your brain. 

The course was given in the Geoscience building of the University of Copenhagen. While entering the main hall, I stumbled onto this view:


A large pendulum was swinging in the centre of the hall. The mass of the solid metal ball was 140 kg. This is the so called Pendulum of Foucault. It proves that the Earth is rotating. At first display in Paris 1851, the pendulum of Léon Focault was the first simple proof that the Earth was rotating in an easy-to-see experiment. The pendulum, swinging in inertial space, would rotate without putting any forces on it. This is because, not the pendulum is rotating, but the Earth, on which the observer is standing. Waiting long enough and you will see the pendulum plane of motion rotating. I recommend you to go and see one (see list), but because you are currently sitting behind your computer, I have a movie:



This video shows the slow swinging motion of the pendulum. I did not film long enough to show you the rotation. Also I think those large ventilation shafts in the floor disturbed the free-motion of the pendulum, because in the evening the plane of motion was in the same direction as in the morning. It was a little bit of a drawback, but I think it is still a cool way to show that the Earth is rotating, just turn off the air conditioning.

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