In 1920, astronomers Harlow Shapley and Heber Curtis held a Great Debate. Shapley argued that the spiral nebulae were small ...

Well, any of us who has ever looked through a telescope could say the same, for the two principal types in use today were developed by giants: the refractor by Galileo and the reflector by Newton.

Callisto, the third largest moon in the entire solar system, orbits Jupiter from about 1.2 million miles away. The rocky ...

Shortly after he began producing his binoculars, news of the telescope reached Galileo. These days, the telescope is mostly closely associated with the night sky, but it's also useful on land and ...

Dust off your old telescope on a clear night and look up. If you find Jupiter, you’ll likely see four small dots to the side ...

In his 2006 book, Galileo’s Instruments of Credit: Telescopes, Images ... of the four largest moons of Jupiter in January, 1610. It is a discovery that backyard stargazers can recreate for ...