Astronomy, the study of the motions and nature
of the sun, moon, stars, planets, and other celestial bodies. Thus, astronomy
might be called the science of matter and energy as they are manifested
in the universe. Astronomers bring to this study the resources of the mathematician,
the chemist, and the physicist. Until recent years, astronomy was a purely
observational science. However, the advent of artificial satellites and
space probes has freed the astronomer from the limitation of only being
able to peer into his celestial laboratory with a telescope. The space
age has presented the astronomer with a means of injecting his instruments
into his laboratory, of carrying them into close proximity of the celestial
bodies he is studying. Hence, astronomy has become an experimental science.
(See also Space
Astronomy is one of the oldest of the sciences. Ancient astronomers observed the motions and relative positions of celestial objects for ritual purposes or in an effort to foretell the destinies of nations and individuals, to measure time, to predict eclipses, to establish dates for planting, and for navigation. The ideas and methods for the solution of the practical problems have long since been worked out. Present-day advances in practical astronomy consist mainly of refinements of techniques and instrumentation to meet the contemporary demands for accuracy. (See also Calendar; Time.)
Few astronomers are now actively concerned with the practical side of astronomy. Such matters are usually dealt with by the staffs of national observatories, such as the U.S. Naval Observatory at Washington, D.C., and the Royal Greenwich Observatory, Cambridge, England. Most of the time and effort of astronomers is now expended in theoretical or observational studies of the structure of the universe.
The bulk of astronomical work is carried on by highly trained astronomers in elaborately equipped university and government observatories. However, unlike those branches of science in which research and invention are confined to the laboratory, astronomy offers participation to hundreds of amateur observers throughout the world. Amateurs gather scientifically useful data on variable stars and novas, artificial satellites, meteors, comets, sunspots and solar flares, auroral displays, and changing features on the surfaces of the moon and the planets.