| When we look to the stars, we think of the | | | | instead of lenses. A string of discoveries soon |
| unknown and the future, but more than any other | | | | followed, including the discovery two new planets, |
| science, astronomy is deeply rooted in the past. From | | | | Uranus (1781) and Neptune (11845). |
| Stonehenge to Galileo to the Hubble telescope, the | | | | Golden Age of Astronomy |
| following article details the history of astronomy | | | | The twentieth century became the Golden Age of |
| Stonehenge | | | | astronomy. In 1801, the discovery of the first |
| The Egyptians, Mayans, and Chinese were all avid | | | | asteroid, Ceres, started a flood of new objects in |
| observers of the heavens. Perhaps the most | | | | the heavens as the tools astronomers work with |
| recognizable example in history is Stonehenge which | | | | have grown in variety and sophistication. In 1937 |
| was built to the movements of the sun by the | | | | Grote Reber built the first radio telescope. |
| Neolithic people of Britain. Stonehenge was important | | | | Technological advances made possible huge |
| for religious reasons, but people also believed the | | | | telescopes like the one at Mount Palomar which has a |
| stars could help guide their lives and foretell events. | | | | 200-inch mirror. |
| This was true in a very practical sense: accurately | | | | The Hubble Telescope |
| predicting the seasons helped farmers plan their crop | | | | Today astronomers have even more exiting tools. |
| season. The stars were also a guide in the sky, used | | | | The best known of these is the Hubble Telescope, |
| by sailors to navigate journeys. | | | | launched into Earth orbit by space shuttle Discovery |
| Around the World | | | | in 1990. Amazingly, the Hubble is still based on |
| Astronomy was one of the first branches of | | | | Newton's original reflecting telescope! Yet it and other |
| knowledge to rely on mathematics. In 256 BCE the | | | | space-based instruments are so powerful they have |
| Greek mathematician Eratosthenes calculated the | | | | discovered more than 200 planets orbiting other |
| circumference of the earth using the angles of | | | | stars. |
| shadows cast by the sun. About 140 CE Ptolemy, | | | | Amateur Astronomy |
| another Greek thinker, advanced a "geocentric" of | | | | Astronomy is unusual because amateurs remain an |
| the universe with the Sun orbiting the Earth. | | | | important part of the search for new knowledge, |
| The Telescope | | | | discovering supernovas, comets, and other objects. |
| Although Arabic astronomers and astrologers made | | | | For example, the famous Shoemaker-Levy comet |
| advances over the next centuries, modern | | | | that struck Jupiter in 1994 was co-discovered by |
| astronomy began with the invention of the telescope | | | | amateur David H. Levy-and it's only one of 22 |
| by Dutch lens maker Hans Lippershey in 1608. The | | | | comets he has found! |
| next year Galileo Galilei used a telescope and | | | | The future of astronomy is as bright as the stars |
| discovered craters on the Moon and the four large | | | | astronomers study-and for the rest of us as well. It |
| moons of Jupiter. Early telescopes were limited | | | | is one of the few areas in which non-professionals |
| because their glass lenses tended to distort the | | | | can actively participate in humanity's search for |
| images. Isaac Newton solved this problem in 1668 by | | | | knowledge. |
| inventing the reflecting telescope, using mirrors | | | | |