How a medieval Oxford friar used light and color to find out what stars and planets are made of

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

During the 1240s, Richard Fishacre, a Dominican friar at Oxford University, used his knowledge of light and color to show that the stars and planets are made of the same elements found here on Earth. In so doing he challenged the scientific orthodoxy of his day and pre-empted the methods and discoveries of the 21st-century James Webb space telescope.

Following the Ancient Greek philosopher Aristotle, medieval physics affirmed that the stars and planets were made from a special celestial element – the famous "fifth element" (quinta essentia) or "quintessence". Unlike the four elements found here on Earth (fire, water, earth and air), this "fift