Prologue - Astronomy before the space age

Progress in astronomical and astrophysical knowledge since about 1900 is traced, with a focus on the beginnings of space-based observations in the late 1950's. It is pointed out that observations were almost exclusively restricted to the visible spectrum unitl 1946. The unique possibilities offered by space observatories are listed, and the original plans for space-based studies of the earth, moon, planets, sun, and interplanetary space, as well as of phenomena beyond the solar system are reviewed. The direction of future space observations with the Space Telescope is indicated.