Learn about our fellows’ research projects: Andreas Athanasakis on the Reception of the Distance-Period Relationship in the Capellan and Copernican Cosmologies

Guest post by Andreas Athanasakis, Pre-doctoral Fellow in Hellenic Studies 2022–23

Research topic during fellowship: The Platonic Forma Mundi Problem

The pre-doctoral fellowship in Hellenic Studies at CHS has afforded me a unique opportunity to undertake a comprehensive investigation of the Platonic forma mundi problem (i.e., the exact necessary order of the planets), particularly as it relates to the cosmological frameworks posited by the Capellan and Copernican perspectives. Although Plato did not solve the forma mundi problem, he did establish the distance-period relationship, which asserts that planets with larger orbits have longer periods of revolution.

Notably, the Copernican heliostatic cosmology was not the first to consistently apply this principle. In fact, the geoheliocentric system developed by Martianus Capella, more than a millennium before Copernicus, demonstrated a consistent application of the distance-period relationship. Capella achieved this by utilizing circumsolar orbits for the inner planets given that Mercury and Venus complete the ecliptic in a solar year on average and hence, prima facie, do not conform to this principle. Capella employed a rudimentary form of Kepler’s third law (i.e., T ∝ a), which was not discovered until many centuries later, in order to determine the relative positions of the planets.

The heliostatic model introduced by Copernicus represents a major breakthrough in the Scientific Revolution, as it marked a shift from traditional geocentric cosmologies towards a more accurate heliocentric framework. Copernicus posited that the Earth orbited around the stationary mean Sun, enabling him to interpret the epicyclic anomalies of Venus and Mercury as their actual orbits around the Sun. The Copernican model adheres to another form of the distance-period relationship that corresponds to what is now recognized as Kepler’s third law of planetary motion (Τ² ∝ a³), although Copernicus himself was unaware of this law at the time. This new paradigm facilitated the development of a comprehensive and mathematically rigorous model of the solar system, which revolutionized astronomy and sparked a wave of scientific inquiry that ultimately led to our modern cosmology.

Despite Copernicus’ revolutionary accomplishments in the domain of astronomy, it is important not to disregard the significant contributions made by Martianus Capella. Capella’s geoheliocentric model utilized a rudimentary version of the distance-period relationship to estimate the positions of the outer planets. This innovative system constituted a significant milestone in astronomy, as it represented a significant shift away from conventional geocentric cosmologies and foreshadowed several crucial aspects of the modern heliocentric model.

About Andreas Athanasakis

Andreas Athanasakis is a Ph.D. fellow in Philosophy at the National and Kapodistrian University of Athens. During his studies, he received multidisciplinary training in fields like philosophy of science, epistemology, physical philosophy, and mathematics. His research interests lie primarily in the relationship of archetypes, mathematics, and physical philosophy from late antiquity up to early modernity, focusing on the platonic “forma mundi problem” and its impact on the Copernican revolution. His methodology is both systematic and historical. He has been awarded several fellowships among which from the Alexander S. Onassis Public Benefit Foundation and from the Hellenic Foundation for Research & Innovation. He has taught philosophy at the University of Athens and he has participated in several nationwide and international conferences/workshops presenting the results of his publications.

Pre-doctoral Fellowships in Hellenic Studies

The annual Pre-doctoral Fellowships in Hellenic Studies program welcomes up to 3 Ph.D. candidates from all Greek universities who conduct research on topics related to ancient Greek civilization. Find out more about this research opportunity on the Pre-doctoral Fellowships in Hellenic Studies webpage.