Galileo's World-Changing Telescope Turns 400

On August 25, 1609—400 years ago today—Galileo Galilei introduced Venice to the telescope, and the discoveries it enabled were every bit as revolutionary as Darwinism, writes Peter Walker of the Guardian. With his telescope, a brown stick weaker than today's store-bought models, Galileo detected moon-like phases of Venus, proving that planets revolve around the sun and not Earth. That brought Galileo scientific immortality, but not before he suffered years of persecution.

The Catholic Church was not happy with Galileo's work, which confirmed Copernicus' century-old speculation that human beings did not stand at the center of the universe, and he spent the last decade of his life under house arrest. Galileo's telescopes now belong to collections in Florence, but one of them is currently on loan to the Franklin Institute in Philadelphia, where visitors can see the instrument that reoriented our place in space.
(More Galileo stories.)