Students in history of science classes may find these web pages to serve as a reading companion to the first chapter and appendix of Michael Crowe, Theories of the World from Antiquity to the Copernican Revolution (Dover, 1990). This inexpensive little book also includes excerpts from the works of Ptolemy and Copernicus. Throughout these web pages we will constantly refer to page numbers in Crowe where his discussions supplement our introductory explanations.
Crowe noted that nearly all of his first chapter "could have been written by an ancient Greek astronomer." Indeed, and therein lie two problems.
"Phenomena" (plural) and "phenomenon" (singular) derive from the Greek, "phainomen" = appearances. Natural phenomena, of course, are all the various observable appearances that natural philosophers, astronomers, or other scientists try to explain (provided that they notice them and consider them worthy of explanation).
In these pages we do not emphasize the Greek concepts of a spherical or moving Earth, of heavenly spheres, circular motions, and coordinate systems, as well as Keplerian celestial mechanics with its ellipses. These are more fully explained by Crowe. However, by first acquainting ourselves with the basic celestial phenomena, we may retrace the invention of these significant conceptualizations in a simulated rediscovery. We may even glimpse some of the ways in which later explanatory concepts affect even the way we now "observe" the "phenomena."
In a study of Babylonian astronomy, Asger Aaboe distinguished three levels of skywatching activities, to which we can add a fourth and fifth. These levels of "astronomy" are as follows:
The first two levels could take place in any settled community, and are evidenced from peoples and locations all over the globe. For this and other reasons, Aaboe himself was willing to designate as "astronomy" only the third level, which characterizes Babylonian work by the time of the Seleukid period (322 B.C.). The fourth level represents Greek astronomy and the fifth astronomy after Ptolemy in medieval Latin, Islamic, and early modern European traditions (for which see Crowe and other recommended sources). With these distinctions in mind, in the Basic Celestial Phenomena web pages we are concerned only with the first two or three levels.
We now will explore the skywatching possibilities or "celestial arts" of priests in their temples and ziggurats, of poets and sailors, of farmers and shepherds in their fields, of Arabian nomads in their desert caravans. That is, we will identify the basic celestial phenomena that require unsophisticated observing skills to name or to recognize. These constitute only a prelude to astronomy, perhaps, not the science itself. If we were a stone age community living night after night unsheltered from the sky, perhaps all of this would be common knowledge. Knowledge of these phenomena in varying degrees might be found in almost any settled community nearly anywhere in the world, whether literate or not--perhaps even in a small university town at the beginning of the third millenium after Christ.