In order to better understand the motion and interactions of the planets (and their satellites) of our solar system, Galileo built mechanical devices to instantiate idealized models of the solar system such as the one in the figure:
Learned about this from Edward Tufte’s “Envisioning Information” and thought it would be worth sharing. This photo is from William Pearson, in Abraham Rees ed., The Cyclopaedia; or, Universal Dictionary of Arts, Sciences, and Literature, Plates, Vol. iv (London 1820).
I think this is a good example of how Galileo placed an emphasis on idealization and understanding by building in science. Not to mention early precursors to the use of computer simulations in science. Interestingly, Tufte warns that these machines may be “directing attention more toward miraculous contraptionary display than to planetary motion.” An important warning for scientists using computer simulations for modeling in general Today.