During the 1240s, Richard Fishacre, a Dominican friar teaching at Oxford University, argued that stars and planets aren’t made of a unique “fifth element” as mainstream science held. Instead, he used observations of light and color to conclude they consist of the same materials as Earth – a remarkably prescient view that modern astronomy has confirmed.
The Established Belief: A Celestial Hierarchy
For centuries, Aristotelian physics dominated scientific thought. It posited that the cosmos was structured around Earth, with nine concentric spheres housing the planets and stars. These weren’t made of familiar terrestrial elements (fire, water, air, earth) but a perfect, unchanging “fifth element” – quintessence. This supposed substance was believed to be transparent and formed the basis of all celestial bodies.
Fishacre’s Challenge: Light, Color, and Composition
Fishacre openly rejected this idea, arguing that stars and planets were composed of the same four elements found on Earth. His reasoning centered on how light and color behave. Composite bodies, made of multiple terrestrial elements, typically exhibit color. When observing Mars (red) or Venus (yellow), Fishacre noticed faint coloration, suggesting they weren’t pure quintessence.
The moon provided the strongest evidence: its color and ability to eclipse the sun proved it wasn’t transparent. If it were made of quintessence, sunlight should pass through it unimpeded, like glass. The fact that it blocked light meant it shared the same material makeup as Earth. Fishacre logically extended this conclusion to all celestial objects.
Facing Opposition
Fishacre’s ideas weren’t well-received. He anticipated backlash, noting his contemporaries would “cry out and stone us” if he challenged Aristotle. And they did: his teachings were condemned in 1250 by St. Bonaventure at the University of Paris, who mocked those questioning the established doctrine of the celestial fifth element.
Modern Confirmation
Contemporary astrophysics has vindicated Fishacre’s reasoning. The James Webb Space Telescope now uses transmission spectroscopy – analyzing how light passes through exoplanet atmospheres – to identify elements like water and sulfur dioxide. This method, in principle, mirrors Fishacre’s approach: subtle variations in light reveal composition.
Fishacre’s insight demonstrates that centuries-old observations, combined with basic physical principles, can yield remarkably accurate conclusions. Modern astronomy has simply refined the tools, but the core logic remains the same.
Fishacre’s bravery in questioning established dogma nearly 800 years ago foreshadowed a scientific revolution. He demonstrated that the universe isn’t built on mystical substances, but on the same fundamental elements as our own world.
