Telescope

The telescope is an optical instrument made with lenses and mirrors which shows magnified views of distant objects. The invention of the refracting telescope (or "spyglass") is usually credited to Hans Lippershey. When Galileo Galilei encountered the spyglass, he made himself a much more powerful one, and was the first person in history to make detailed recorded observations of the objects in the nighttime sky.

Galileo discovered the moons that revolve around the planet Jupiter. These can seen by anyone with a pair of modern binoculars; they usually look like three or four stars that are close to Jupiter and all lined up in a straight line. This discovery was important because at the time philosophers and theologians believed that everything in the universe revolved around the Earth. They believed that the geocentric design reflected the will of God. Galileo's discoveries and his insistence on publishing them put him into conflict with the Catholic Church and even led to his being put under house arrest.

The simplest telescopes (e.g., the kind Galileo worked with) are built with two lenses in a tube.

During the twentieth century, astronomers built huge telescopes. Some of the most famous in the United States are:

• the Lick Observatory on Mount Hamilton near San Jose, California;
• the Yerkes Observatory in the resort area on the shore of Lake Geneva in Wisconsin;
• the Mount Palomar Observatory near San Diego, California;
• the Keck Telescope on Mauna Kea in Hawaii.
• the Hubble Space Telescope in Earth orbit.