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plantary_ephemerides [2010/03/25 22:51] ongplantary_ephemerides [2010/03/28 21:40] (current) – external edit 127.0.0.1
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 As with the moon, the Babylonians conducted observations of the planets with reference to the ecliptic(link). The planets moved along the ecliptic through the years in the same direction of the sun, and eventually completed one trip around it. After this they would exhibit the same phenomena at the same times as the previous cycle. However for a stretch of their orbit the planets would appear to change directions against the sun, in a phase called retrogression. Thus the Babylonians determined the beginning and ending points of each planet's regression. Also, as with the new moon the planets could be in a position relative to the earth such that sunlight obscured their presence in the sky. For the 'outer' planets (that is, Mars, Jupiter, and Saturn), there was only one such phase of invisibility in the (fundamental?) period, and the Babylonians determined the beginning and ending points of this phenomena as well. The inner planets (Mercury and Venus) had two such phases of disappearance, one occurring during the time the planet was seen as an 'evening star', and the other when it was seen as a 'morning star'. For all planets the Babylonians determined the times of opposition as well. As with the moon, the Babylonians conducted observations of the planets with reference to the ecliptic(link). The planets moved along the ecliptic through the years in the same direction of the sun, and eventually completed one trip around it. After this they would exhibit the same phenomena at the same times as the previous cycle. However for a stretch of their orbit the planets would appear to change directions against the sun, in a phase called retrogression. Thus the Babylonians determined the beginning and ending points of each planet's regression. Also, as with the new moon the planets could be in a position relative to the earth such that sunlight obscured their presence in the sky. For the 'outer' planets (that is, Mars, Jupiter, and Saturn), there was only one such phase of invisibility in the (fundamental?) period, and the Babylonians determined the beginning and ending points of this phenomena as well. The inner planets (Mercury and Venus) had two such phases of disappearance, one occurring during the time the planet was seen as an 'evening star', and the other when it was seen as a 'morning star'. For all planets the Babylonians determined the times of opposition as well.
  
-== Determining the fundamental period ==  
  
-The Babylonians were primarily interested in the two points in a planet's orbit+
plantary_ephemerides.1269557470.txt.gz · Last modified: 2010/03/25 22:51 by ong
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