The Telescope

Galileo Galilei, The Phases of the Moon

In 1609 Galileo Galilei, a professor of mathematics at Padua, heard reports of an exciting new instrument, the telescope. He soon made a much improved model and turned it toward the heavens. What he saw there amazed the world and changed it forever. The Starry Messenger (Sidereus Nuncius), a slim volume published in March 1610, reported "great and marvellous sights": "the lofty mountains and deep valleys" of the moon; a Milky Way revealed to be no dusty haze of light but "a mass of innumerable stars" that had never been seen distinctly before; and most astonishing of all, four satellites of Jupiter.

Copernicus had been right about the solar system. The challenge to the fixed-earth doctrine of the church provoked Pope Urban VIII; eventually Galileo was tried and imprisoned by the Inquisition, which forced him to recant. But the revolution in the heavens continued. In the late 1660s, Isaac Newton greatly improved the telescope by substituting concave mirrors for lenses; his six-inch-long reflecting telescope could magnify forty times, surpassing a six-foot-long refractor. With the help of such instruments, Edmond Halley was able to predict the return of the comet that bears his name, and William Herschel discovered Uranus in 1781.

James Thomson, from The Seasons

Many amateurs also enjoyed the pleasures of gazing through a telescope at the night sky. It was a theme of which eighteenth-century British poets never tired, as in James Thomson's appeal to Nature in his poem The Seasons (1730).

From Autumn (lines 1354–59)