25 August 2011
On this date in 1609, Galileo Galilei demonstrated his first telescope to the Venetian Senate in Padua. He didn't invent the telescope -- credit for that goes to a Dutch astronomer, Hans Lipperhey, who had demonstrated one the previous year -- but he heard about it, and by trial and error he figured out how it was made. Galileo greatly improved on the design and made it variable-focus. Venice was known for the quality of its glass craftsmanship, and Galileo bought lenses from spectacle-makers at first, but soon taught himself the art of glass grinding. The telescope he presented to the senate could magnify images to eight times the naked eye, and by the fall, he was looking at celestial bodies through a 20-power telescope. By the following January, he had discovered four moons orbiting Jupiter. The Senate was so impressed with his invention that they gave him lifetime tenure at the University of Padua and doubled his salary.
Thank you, Writer's Almanac.