Astronomy

Astronomy is the science of celestial bodies, such as planets, stars, and comets, and phenomena which originate outside the earth's atmosphere. Astronomy is one of the oldest sciences. At the beginning, in ancient times, astronomers performed methodical, naked-eyed observations of the night sky. But the invention of the telescope was required before astronomy was able to develop into a modern science. Amateur astronomers have contributed to many important astronomical discoveries, as astronomy is one of the few sciences where amateurs can still play an active role, especially in the discovery and observation of transient phenomena.

In early times, astronomy only comprised the observation and predictions of the motions of objects visible to the naked eye. In some locations, such as Stonehenge, early cultures assembled massive artifacts that likely had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops, as well as in understanding the length of the year. Before tools such as the telescope were invented early study of the stars had to be conducted from the only vantage points available, namely tall buildings, trees and high ground using the bare eye.

Prior to the application of the telescope, a few notable astronomical discoveries were made. For example, the obliquity of the ecliptic was estimated as early as 1000 BC by the Chinese. The Chaldeans discovered that lunar eclipses recurred in a repeating cycle known as a saros. In the 2nd century BC, the size and distance of the Moon were estimated by Hipparchus.