Smith F.G. Radio Astronomy

Penguin Books, 1966 - 286 p.
Third editionRadio astronomy, a very young science, is a vigorous offshoot of a discipline whose roots are found in our earliest recorded history. Those who first observed and wondered at the courses and constellations of the stars, and the wanderings of the planets, had no instruments to extend their observation beyond the perception of keen eyes. But in 200 b.c., in Babylon, astronomers had already established a system of time-keeping based on their observations of the sun and the stars, dividing the year into twelve months, and the day into hours, minutes, and seconds. And sailors of the same period had learned to navigate with the help of the stars.