Galileo's Telescope and the Heavens

In 1608 the Dutch spectacle-maker Hans Lipperhey applied for a patent on a device that made distant objects look closer. When Galileo Galilei heard about it in 1609, he ground his own lenses and built telescopes magnifying about twenty times. Pointing them at the sky, he saw mountains and craters on the Moon, countless stars in the Milky Way and four moons orbiting Jupiter, which he published in 1610 in The Starry Messenger.

These observations challenged the ancient belief that the heavens were perfect and that everything circled the Earth. The telescope did not prove the Sun-centred model on its own, but it supplied new evidence that supporters of Copernicus could use. It also raised a lasting question: should people trust what an instrument shows, even when it contradicts the senses and authority? The episode marks the beginning of science that depends on instruments extending human perception.