Geometrization 3.0: The Black Hole Shadow

There have been three geometrizations in history. The first is historically due to the Pythagorean school and Plato while the second comes from Galileo, Kepler, Descartes and Newton, and the third geometrization of nature begins with Einstein’s general relativity. Here the term geometrization of nature means the conception according to which nature (with its different meanings) is broadly described by using geometry. In this article, I focus on the third geometrization, in which the black hole shadow phenomenon relates shape to dynamics. As a consequence, spacetime symmetry could play the role of the formal cause in black hole physics. Spacetime symmetry as a formal cause of spacetime could be an interesting point in the kinematics-dynamics debate in the theory of relativity.