Western Cosmology and the Becoming of Possibility: 5 Copernicus to Galileo: The Decentering of Earth and the Expansion of Possibility

The transition from medieval to early modern cosmology inaugurates a decisive reopening of potential through heliocentrism and systematic observation. Copernicus’ radical proposal that Earth is not the centre of the universe fundamentally altered the horizon of possibility: the cosmos was no longer a fixed, hierarchically ordered stage for human and celestial events, but a vast, dynamic field with new degrees of freedom for both celestial bodies and human understanding.

Observational astronomy, particularly through Galileo’s telescopic investigations, reinforced this construal shift. The heavens were revealed as complex, dynamic, and accessible to empirical investigation. Possibility expanded not merely in a spatial sense but epistemically: humans could now test, measure, and engage with phenomena previously reserved to theological or speculative frameworks. The cosmos itself became a field in which relational patterns could be apprehended and interpreted, opening new pathways for conceptualising potentiality.

Two modulatory voices further enrich this period. Giordano Bruno’s vision of infinite worlds challenges any residual hierarchical centrism, presenting the cosmos as potentially boundless and multiplicities of worlds as actualisable possibilities. Johannes Kepler’s laws of planetary motion introduce precise mathematical regularities, demonstrating that the relational structures governing celestial bodies could be rigorously described, predicted, and thus conceptually integrated into the horizon of human potential.

In this period, construal strategies pivot from theological determinism to empirical relationality: possibility is both discovered and structured through observation, calculation, and conceptualisation. The decentring of Earth signifies not just a spatial reorientation but a profound epistemic and ontological shift — humans are participants in a universe whose potentialities extend far beyond prior hierarchical constraints.

In sum, the Copernican-Galilean revolution exemplifies how cosmological innovation reconfigures both cosmic and human possibility. By decentring the familiar, expanding observational scope, and introducing new conceptual tools, this era establishes a foundation for the mechanistic and mathematical cosmos of the seventeenth century, while opening the door to radical imaginaries of infinite worlds and relational laws.