Ptolemaic to Copernican World System Continuum

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The beginning of the Copernican revolution was simply a change in viewpoint. This Demonstration lets you continuously change your point of view on the inner solar system from the ancient geocentric perspective (Ptolemaic system) to the new heliocentric one (Copernican system). You can decide to move along the straight line segment connecting the Earth to the Sun or to vary the radius of your heliocentric orbit, thus exploring the hermocentric (with Mercury at the center), aphrodiocentric (with Venus at the center) and areocentric (with Mars at the center) world systems.

Contributed by: Paolo Maraner (July 2017)
Open content licensed under CC BY-NC-SA



Contrary to what is commonly suggested, the original Copernican model (with circular orbits) provided no improvement in the quantitative description of the heavens. As a kinematic equivalent to the Ptolemaic model, it suffered exactly the same kind of problems and needed exactly the same kind of corrections, such as eccentrics and equants. For this reason, the model was not immediately accepted by the majority of astronomers [1]. Nonetheless, the enormous advantage offered by the change in viewpoint eventually led to the dynamical view of Galileo, Kepler and Newton and to the birth of modern science.


[1] O. Gingerich, The Book Nobody Read: Chasing the Revolutions of Nicolaus Copernicus, New York: Walker & Company, 2004.

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