This post is an exerpt from the book ‘Archimedes and the Door of Science’ by Jeanne Bendick, published 1962, p73-75.
In the third century before Christ, astronomers had none of the tools that astronomers today have. They had no telescopes, because they had no lenses. They had no radio signals, no spectroscopes, no inferometers, no cameras or computers. They didn’t even have a real clock.
They had only their sharp powers of observation, their curiousity, and great patience. They waited for months, comparing the phases of the moon, and for years, observing the shadows of the sun in different places.
They had their knowledge of mathematics and a few crude tools: peepholes, sundials, measuring rods, compasses for drawing circles. They had a water clock and a sun stick, with the length of its shadow marked off into twelve parts which showed, roughly, the hours of the day. Of course, these hours of daylight were fewer in winter and more in summer.
They charted the course of the sun’s annual path among the stars. By their observations of the time when certain bright stars appeared on the horizon they estimated the seasons and the length of the year. At Alexandria they made a catalogue of all the visible stars, and mapped their positions.
What we now call the solar system, astronomers at that time called the universe, and they thought the earth was its centre. Most astronomers thought the universe looked like this,
with the sun revolving round the earth.
They thought that most of the stars were “fixed”, fastened somehow in place against the sky. But what about those stars that seemed to move? The Greeks called them planets, which meant “wanderers”. Since the astronomers had only their eyes to see with, they found only five planets, but they noticed many things about them.
The smallest and fastest one, they called Mercury, for the messenger of the gods.
They called the brightest one Venus, for the goddess of beauty.
Mars, shining red, they named after the god of war.
Jupiter, because it was so big, got its name from the king of the gods. And the one that seemed to move very slowly they named Saturn, for the god who sometimes could make time stand still.