AAbout 800 years ago, Richard Fishacre, a Dominican friar at Oxford University, challenged the scientific thinking of his time by using his understanding of the behavior of light to show that stars and planets were made of the same elements as those found on Earth. Although he faced harsh criticism at the time, Fishacre would probably be pleased to know that very similar principles are used to make discoveries today.
During his lifetime, it was believed that the Earth consisted of four elements – fire, water, earth and air, and the stars and other planets – of a special transparent and unchanging fifth element.
But Fishacre relied on his understanding of light and color claim that if the stars and planets were made of such a substance, they would appear transparent. Instead, he said, the red color of Mars, the yellow color of Venus, and the blue and white colors of the Moon, he said, are clear evidence that they are composed of many elements also found on Earth.
Today, telescopes such as the James Webb are detecting changes in the brightness and color of light from distant planets and stars, recently discovering that TOI-421b – exoplanet 244 light years away – has atmosphere rich in water and sulfur dioxide.
