Galileo’s Instruments of Discovery

Galileo’s telescope anchors the exhibit “Galileo, the Medici and the Age of Astronomy,” which is at the Franklin Institute in Philadelphia until September 7, 2009. Though Galileo didn’t invent the telescope (Dutch opticians did), he improved upon it. The first telescope used a combination of two lenses within a tube, and it could magnify items by three times, but showed them upside down. But when Galileo constructed his own telescope in 1609, he added a third lens. His telescope magnified items by eight times and showed them right side up. Over the following years, Galileo built several telescopes, including one that would magnify items by a factor of 30.