IVb. BABYLONIAN CHARACTERISTIC PHENOMENA The Babylonian use of characteristic synodic phenomena appears to have been largely minimized and generally misunderstood by most modern commentators for reasons that are far from clear. It is certainly true that the phenomena in question are not generally treated by modern astronomers, but even so there are aspects of the methodology that require careful consideration--not least of all the twin components provided firstly by the diurnal axial rotation of Earth about its axis from west to east, and secondly--also from west to east--the annual revolution of Earth itself. East and west are therefore loaded terms, but they are nevertheless perfectly understandable in the Babylonian context, especially from the heliocentric viewpoint, as indeed are all the Babylonian synodic phenomena. Take, for example, the following description of the motion of Jupiter with elliptical planetary orbits viewed from above with both Jupiter and Earth moving concentrically around the Sun from west to east roughly in the same plane. According to the procedures outlined in Sections 30 and 31 of ACT 813 (a lengthy Babylonian procedure text for Jupiter) starting with Jupiter positioned at 90 degrees and Earth at 257 degrees (say), as faster-moving Earth continues to move away from Jupiter there will eventually be a Last Appearance (i.e., last visibility) in the West for Jupiter when this planet becomes obscured from view, i.e., when Earth moves behind the Sun. The next time Jupiter will become visible will be the First Appearance in the East (after a further 29 days of motion by Earth) as Earth swings around the Sun and Jupiter becomes visible once again as it rises on the eastern horizon on one specific date (i.e., the helical rising). Next, as Earth continues to gain on Jupiter, it will reach a position (the First Stationary Point)whereafter Jupiter will appear to move backwards and then reach opposition when Jupiter, Earth and Sun are in line. Further progress takes Earth to the second Stationary Point after which Jupiters forward motion will apparently resume. Lastly, continuing to move away from Jupiter, Earth will once again reach a point in the orbit when Jupiter finally disappears from view, i.e., the Last Appearance in the West is reached again, and so on into the next cycle. All of which is perfectly understandable in heliocentric terms and almost meaningless without. It is not certain whether sequential observations of this kind necessarily resulted in the Babylonian determination of the 12 and 71 year periods and ultimately the fundamental period relationship for Jupiter of 427 years with its 36 sidereal periods and 391 First appearances in the East. But one thing seems clear enough; carrying out continued observations of successive synodic phenomena around the complete orbit of a planet against the background provided by the goal-year and other stellar reference points would naturally lead to an awareness of the faster, slower and mean orbital velocities and also where they were located. Thus it is not that difficult to envisage how the Babylonian were able to determine varying orbital velocity, the range between extrema, the rate of change and even the location of the line of apsides. Nor is it hard to see that in doing so and also coming to terms with the apparent retrogradation and stationary points, that the Babylonians had no need whatsoever for auxiliary devices. Their approach may have been a simple one, but it was the simplicity of Occams Razor nevertheless, as the following detailed example shows:
Posted on: Tue, 07 Oct 2014 11:52:37 +0000
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