What are Basic Celestial Phenomena?

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An Introduction to Ancient Non-Greek Skywatching

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.

 
Celestial phenomena
What was intelligible to an ancient Greek astronomer may appear "Greek" to us, if we remain unsure about the most basic appearances that the stars and heavenly bodies present from day to day and season to season. This is all the more true for those of us who grow up without constant exposure to the stars and consequently do not develop a familiarity with them. Basic celestial phenomena fall among those things which become less rather than better known with civilization. They are a heritage passed down to us from every generation, yet one which is strangely neglected in the hectic pace of modern life. If we wish, or if we don't make pronounced efforts to the contrary, we city dwellers may spend our whole lives artificially isolated from the stars. In these pages, then, we will try to "take the roof off," to introduce the various celestial phenomena, starting at a much more basic level than Crowe. Take advantage of the skywatching activities frequently suggested. We hope they will help you translate what you read into an actual experience of the night sky, so that you may look up in perfect silence at the stars.

 

Non-Greek conceptualizations
A second aim of the Basic Celestial Phenomena tutorials is to orient us to non-Greek traditions of skywatching in antiquity, those of Babylon, Egypt, Stonehenge, or Meso-America. Accordingly, the conceptualizations we owe to the Greeks or to medieval Latin, Islamic, or early modern astronomers (Eudoxos, Ptolemy, Copernicus, Kepler, etc.) are not emphasized to any great extent. Almost nothing given here was unknown to the ancient Babylonians, however. Our present emphasis is the description of "phenomena," that is, how the sky appears to us at different times.

"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."

Levels of Astronomy

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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:

  1. Naming and Recognition of basic celestial phenomena.
  2. Recognition of various cycles, patterns, or periodic rules.
  3. Arithmetical schemes to predict future phenomena with minimal ongoing observational feedback (quantitative control of phenomena).
  4. Geometrical schemes to explain phenomena, even if only qualitatively.
  5. Realistic cosmological models capable of accurate predictions.

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.

Discussion Questions

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