In 1597 the young mathematics teacher in Graz, Johannes Kepler, wrote to a friend that he had received a letter from an Italian with a very strange name; in fact his forename was exactly the same as his family name. The letter was from the Paduan professor of mathematics Galileo Galilei, or in the Latin in which he wrote to Kepler, Galileus Galileus, who was born on the 15th of February 1564. In his letter Galileo thanked Kepler for his book, Mysterium Cosmographicum a strange Renaissance piece of Platonic Pythagorean mathematical mysticism that however revealed its author to be a very good mathematical astronomer, and declared himself to be a secret admirer of the theories of Copernicus. This letter has led to a very common myth in the popular history of science.
Kepler a young unknown mathematician had published his book, his first, in 1596 and like many first authors had tried to win himself a reputation in that he sent gratis copies of his book to the leading experts throughout Europe, amongst others the Imperial Mathematicus in Prague, Nicolai Reymers Baer called Ursus, Tycho Brahe in Hven and according to the myth the famous Galileo Galilei in Padua. The first two addressees are correct and in fact would cause Kepler much stress as the two astronomers were mortal enemies however he never sent a copy to Galileo because he had never heard of him, which was not surprising as Galileo was completely unknown outside of Northern Italy at this point of his life. So how could Galileo send him the letter, mentioned above, thanking him for the book?
Shortly after the publication of his book one of Kepler’s friends was setting out on a journey to Rome and just before he left Kepler gave him two copies of his book asking him to give them to anybody he met on his travels who might be interested in them. Kepler’s friend went off to Rome and having completed his business set off back to Austria. On the return journey he had reached Padua when he suddenly remembered Kepler’s book. Hurrying to the local university he found the professor for mathematics and pressed both copies into his hands briefly explaining their provenance. The professor quickly skimmed the introduction and dashed off the letter to the author mentioned above. Neither professor nor author had ever heard of the other before and so Kepler’s amusement over the Latin rendition of Galileo’s name.
Kepler immediately wrote a long gushing reply and so tried to initiate what might have become one of the most important correspondences in the history of science. I say tried because Galileo never replied to Kepler’s letter. In fact it would be 1610 before Kepler, in the meantime Imperial Mathematicus and most important mathematician in Europe, heard from the Paduan professor again; Galileo wrote to Kepler seeking his support for his Sidereus Nuncius. Kepler did not disappoint and wrote a long equally gushing letter of support, which Galileo published in Venice without the author’s permission but again did not answer. In books on the history of science you will often see references to the Galileo Kepler correspondence but this should be regarded with a dose of healthy scepticism because a correspondence in the conventional meaning of the term between these two giants of science of the early modern period hardly exists.