Gary, There is no such thing as a "tangental wave," because tangent (and arc tangent) is a discontinuous function. Sine and cosine curves are identical, but out of phase by 90 degrees. From the north ecliptic pole, the Moon's path would produce a pattern like that of the blue trace (Saturn) in the first, World-centred diagram on the "Flower Pattern Discover" page of www.midclyth.supanet.com under the heading of "The Universe." Regards, Neville. Gary Shelton <garylshelton@xxxxxxxxxxx> wrote: Cheryl, I meant to comment on the one movie that had the moon orbiting a revolving earth, when viewed from the north celestial pole. That is exactly what I have been telling folks for years. The path of the moon's orbit is not, no, CAN NOT be a closed circle or ellipse, simply because the earth is moving. It necessarily ends up looking like a sine wave from the North Celestial Pole just as your movie depicts. I might have to beg forgiveness for using the term "sine wave". It is certainly some kind of wave pattern. I really can't tell a "sine wave" from a "co-sine wave" or a "tangental wave" (if such exist). Sincerely, Gary Shelton --------------------------------- ALL-NEW Yahoo! Messenger - all new features - even more fun!