Copernicus's A Very Liquid Heaven

In the pre-Copernican era, geocentrism was the paradigm for astronomers and philosophers. There were some thinkers, such as Aristarchus and Oresme, prior to Copernicus who advocated for heliocentrism or other models. However, the majority of philosophers and scientists held on to the physics and models of Plato, Aristotle, and Ptolemy. Nicholas Copernicus caused the paradigm shift from the idea that the Earth is stationary and central, to the idea that the Earth rotates and revolves around the sun. In De Revolutionibus Orbium Caelestium, Copernicus explains his stance on the shapes, movements, sizes, and positions of celestial objects (Danielson 104). Regarding the movement of celestial objects, he says that all heavenly bodies, including the Earth, move in circular paths. There are, however, inconsistencies that challenge that idea, such as retrograde motion, variable speeds, and variable apparent distances. Copernicus explains these inconsistencies simply: these irregularities appear in heavenly bodies because “Earth is not at the center of their circles of revolution” (Copernicus

Even after his time, though, some thinkers still held on to the idea of a stationary Earth. One such philosopher is René Descartes. In A Very Liquid Heaven, he references Copernicus, stating, “I will be more careful than Copernicus not to attribute motion to the earth” (Descartes 191). Descartes believed the heavens were made of some liquid substance, and all bodies in the cosmos were suspended in it. The Earth is at rest in this liquid, and, in Descartes’ mind, there are no observations to counter that claim. However, the liquid moves but the Earth moves with it and does not change position relative to the liquid surrounding it. Therefore, Descartes states that the Earth is definitely at rest based on his definition of movement as a change in position relative to surroundings (Descartes