A telescope to the past.

• Position: ASTRONOMY - Brief article

Four hundred years ago, Galileo Galilei built his first telescope--and began to change the way people viewed the universe. In honor of the anniversary, one of Galileo's telescopes [shown above] is on display at the Franklin Institute in Philadelphia through the summer, (It's one of two that still exist; until now, neither had been outside Italy since Galileo's lifetime.) An astronomer and physicist, Galileo made his first telescope in 1609 after hearing that a Dutch eyeglass maker had built a spyglass. Galileo's telescopes allowed him to become the first to see mountains on the moon and satellites orbiting Jupiter. These...