|MadSci Network: Physics|
Scientists in 1851 should have been unsurprised by Foucault's pendulum. Educated people of the day knew very well that the earth was round and rotated - after all, Juan Sebastian de Elcano, Magellan's navigator, sailed all the way around the world in 1519-1522 (Ferdinand Magellan didn't actually make it). Indeed, the world was well-known to be round by (some of) the ancient Greeks. So Foucault's demonstration would have been seen as beautiful, elegant, and dramatic, but it shouldn't have changed their world view.
What about the man-on-the-street? Again, I think that a well-educated citizen - the sort of person who attended the 1851 Crystal Palace exhibition in London, or people like Napoleon Bonaparte who attended Foucault's demonstration in Paris - certainly knew that the world was round and rotated. This was the Victorian Era; things were changing fast. The Industrial Revolution had begun. Modern medicine had been invented. Michael Faraday was studying electricity and magnetism (and delivering hugely popular lecture-demonstrations). There was popular interest in, and excitement about, all of the sciences; people felt like humankind was finally mastering science and nature, and that a golden age of technology was just around the corner. I think that's why Foucault's demonstration attracted so much attention: not for discovering something new, but for an impressive demonstration, and for reinforcing the idea of the triumph of science. "Now we have tamed the Earth's very rotation! What wonders shall the future bring?" And, of course, it's much more intuitive to see the Earth rotate in front of you, rather than to read about it in a book, or measure it in the motion of the sun and stars.
I don't have any specific information on the reaction to Foucault's pendulum, other than that it was very popular. There is a well-reviewed biography of Foucault entitled "Pendulum: Leon Foucault and the Triumph of Science" by the excellent writer Amir Aczel - check your local library. You might also read up on Victorian-era science in general (try www.victorianweb.org); biographies of Michael Faraday, who I think really exemplified the spirit of his day; or books about the Great Exhibition of 1851 at the Crystal Palace in London.
Hope this helps,
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