It’s hard to overstate how important the telescope was to Galileo’s image. It was his emblem and icon, the first next big thing, the ancestor of Edison’s light bulb and Steve Jobs’s iPhone. A Tuscan opportunist to the bone, Galileo rushed off letters to the Medici duke in Florence, hinting that, in exchange for a job, he would name the new stars after the Medici. He wanted to go back to Florence, partly, it seems, because he wanted to persuade the smart, well-educated Jesuits who clustered there to accept his world picture. Sell the powerful Jesuits on the New Science, he thought, and you wouldn’t have to worry about the Inquisition or the Pope. Galileo felt himself already under enough religious pressure to continue to encode all talk of his discoveries in his correspondence with Kepler. He even sent him a letter about the phases of Venus in cipher, ending, “Oy!” Really, he did. Heilbron suggests, smilingly, that this hints at Jewish ancestry. (No evidence exists that Kepler replied “Vey!”)