A Brief History of Motion

Before streets were brightly illuminated at night, astronomy was accessible to everyone and was a matter of great importance: for divination; for setting appropriate dates for planting, harvest, and festivals; for regulating lives. Phenomena in the heavens are still of great importance to many, and much of the lore of astronomy and astrology dates back to the earliest days of civilization. The astronomy of the ancients is thus of interest not only as history but also as the basis for much of what is known or believed about the heavens today. Because phenomena in the heavens are less familiar today than in earlier eras, this book begins with a brief description of what one can see in the sky on dark nights with the naked eye.

by Victor A. Dubrovsky (Author)

Geostationary or equatorial synchronous satellites are a daily reminder of our space efforts during the past two decades. The nightly television satellite weather picture, the intercontinental telecommunications of television transmissions and telephone conversations, and the establishrnent of educational programs in remote regions on Earth are constant reminders of the presence of these satellites. As used here, the term 'geo­ stationary' must be taken loosely because, in the long run, the satellites will not remain 'stationary' with respect to an Earth-fixed reference frame. This results from the fact that these satellites, as is true for all satellites, are incessantly subject to perturbations other than the central-body attraction of the Earth. Among the more predominant pertur­ bations are: the ellipticity of the Earth's equator, the Sun and Moon, and solar radiation pressure.

Geostationary or equatorial synchronous satellites are a daily reminder of our space efforts during the past two decades. The nightly television satellite weather picture, the intercontinental telecommunications of television transmissions and telephone conversations, and the establishrnent of educational programs in remote regions on Earth are constant reminders of the presence of these satellites. As used here, the term 'geo­ stationary' must be taken loosely because, in the long run, the satellites will not remain 'stationary' with respect to an Earth-fixed reference frame. This results from the fact that these satellites, as is true for all satellites, are incessantly subject to perturbations other than the central-body attraction of the Earth. Among the more predominant pertur­ bations are: the ellipticity of the Earth's equator, the Sun and Moon, and solar radiation pressure.