When we look to the stars, we think of the unknown and the future, but more than any other science, astronomy is deeply rooted in the past. From Stonehenge to Galileo to the Hubble telescope, the following article details the history of astronomy

Stonehenge

The Egyptians, Mayans, and Chinese were all avid observers of the heavens. Perhaps the most recognizable example in history is Stonehenge which was built to the movements of the sun by the Neolithic people of Britain. Stonehenge was important for religious reasons, but people also believed the stars could help guide their lives and foretell events. This was true in a very practical sense: accurately predicting the seasons helped farmers plan their crop season. The stars were also a guide in the sky, used by sailors to navigate journeys.

Around the World

Astronomy was one of the first branches of knowledge to rely on mathematics. In 256 BCE the Greek mathematician Eratosthenes calculated the circumference of the earth using the angles of shadows cast by the sun. About 140 CE Ptolemy, another Greek thinker, advanced a "geocentric" of the universe with the Sun orbiting the Earth.

The Telescope

Although Arabic astronomers and astrologers made advances over the next centuries, modern astronomy began with the invention of the telescope by Dutch lens maker Hans Lippershey in 1608. The next year Galileo Galilei used a telescope and discovered craters on the Moon and the four large moons of Jupiter. Early telescopes were limited because their glass lenses tended to distort the images. Isaac Newton solved this problem in 1668 by inventing the reflecting telescope, using mirrors instead of lenses. A string of discoveries soon followed, including the discovery two new planets, Uranus (1781) and Neptune (11845).

Golden Age of Astronomy

The twentieth century became the Golden Age of astronomy. In 1801, the discovery of the first asteroid, Ceres, started a flood of new objects in the heavens as the tools astronomers work with have grown in variety and sophistication. In 1937 Grote Reber built the first radio telescope. Technological advances made possible huge telescopes like the one at Mount Palomar which has a 200-inch mirror.

The Hubble Telescope

Today astronomers have even more exiting tools. The best known of these is the Hubble Telescope, launched into Earth orbit by space shuttle Discovery in 1990. Amazingly, the Hubble is still based on Newton's original reflecting telescope! Yet it and other space-based instruments are so powerful they have discovered more than 200 planets orbiting other stars.

Amateur Astronomy

Astronomy is unusual because amateurs remain an important part of the search for new knowledge, discovering supernovas, comets, and other objects. For example, the famous Shoemaker-Levy comet that struck Jupiter in 1994 was co-discovered by amateur David H. Levy-and it's only one of 22 comets he has found!

The future of astronomy is as bright as the stars astronomers study-and for the rest of us as well. It is one of the few areas in which non-professionals can actively participate in humanity's search for knowledge.