Enlarge / The original letter in which Galileo argued against the doctrine of the Roman Catholic Church. (credit: Royal Society)

Renowned astronomer Galileo Galilei has been lauded for centuries for his courageous principled stance against the Catholic Church. He argued in favor of the Earth moving around the Sun, rather than vice versa, in direct contradiction to church teachings at the time. But a long-lost letter has been discovered at the Royal Society in London indicating that Galileo tried to soften his initial claims to avoid the church’s wrath.

In August, Salvatore Ricciardo, a postdoc in science history at the University of Bergamo in Italy, visited London and searched various British libraries for any handwritten comments on Galileo’s works. He was idly flipping through a catalogue at the Royal Society when he came across the letter Galileo wrote to a friend in 1613, outlining his arguments. According to Nature, which first reported the unexpected find, the letter “provides the strongest evidence yet that, at the start of his battle with the religious authorities, Galileo actively engaged in damage control and tried to spread a toned-down version of his claims.”

“I thought, ‘I can’t believe that I have discovered the letter that virtually all Galileo scholars thought to be hopelessly lost,’” Ricciardo told Nature. “It seemed even more incredible because the letter was not in an obscure library, but in the Royal Society library.”