View Full Version : Phases of the moon
I feel as though I have a good understanding of the movements of the moon, sun, planets and any other bodies out there, but there is still one thing that has been giving me trouble. My problem is finding out the phase of the moon given its position and the suns position in the sky. Can someone help me try to understand a way to visualize it? Here are some examples:
1) Moon is east of the Sun in the sky.
2) The Sun is located at the vernal equinox and the moon is at the autumnal
equinox.
3) A lunar eclipse occurred about one week ago.
russ_watters
Dec13-10, 10:57 PM
Here's a recent thread on the subject: http://www.physicsforums.com/showthread.php?t=441518
However, the best way to visualize the phases is with a table lamp and some fruit!
However, however, I'm not sure what the equinoxes really have to do with the phases and the wording doesn't make much sense to me: the equinox has to do with the tilt of the Earth with respect to the Sun. It doesn't have anything to do with where the moon is. Perhaps equinox isn't the word you are looking for?
I think it means that the moon will be full as they are separated by 180 degrees (if the nodes were aligned then it would be a lunar eclipse).
Thanks for the thread, I'll check it out
Philosophaie
Dec18-10, 08:05 PM
The moon travels from West to the East. Having a Declination +/- 24degrees maximum/minimum somewhere above or below the Ecliptic. When the Declination is graphed with the Right Ascension it creates a sinusoid wth a peroid about 27 days.
http://en.wikipedia.org/wiki/Moon
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