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Did You Know?
In Did You Know? the National Geographic magazine team shares extra information we gathered to expand your knowledge of our featured subjects.

Echoes of Vision

Galileo did not invent the telescope, as is often stated, but when news of an "optical tube" crafted in Holland in 1608 reached him at the University of Padua in Italy, Galileo immediately set to work building his own. By autumn 1609 he had made his first telescope—a tube with two glass lenses, one convex and one concave, which made objects seem three times closer than they were. He turned his marvelous new instrument to the skies and changed our view of the universe.

Galileo wrote about his first observations—of the moon "besprinkled" with spots, of "four planets flying around the star of Jupiter," and of the "inconceivable crowd" of stars in the Milky Way—in Sidereus Nuncias ("Starry Messenger" or "Sidereal Messenger") in 1610. He promised that his 60-page, soon-to-be bestseller would unfold "great and wonderful sights" and display them "to the gaze of everyone." He conceded that his observations were only a beginning: "Perhaps more excellent things will be discovered in time, either by me or by others, with the help of a similar instrument."

When Lyman Spitzer, Jr., proposed a large orbiting telescope 336 years later, he echoed Galileo's vision of exploring the unknown. Spitzer foresaw a telescope with the power to "uncover phenomena not yet imagined." Indeed, the Hubble Space Telescope, just as Galileo's primitive "spyglass," has opened a wondrous universe to all who care to look.

—Barbara L. Wyckoff