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Homework Help: Understanding Phases of the Moon

  1. Sep 9, 2012 #1
    ok, so I guess this is supposed to be really easy, but I just can not seem to get my head wrapped around this...

    I have a homework question that goes like this. Here is the link to it: http://www.apsu.edu/sites/apsu.edu/f...5_Solution.pdf [Broken]

    If the link dosent work, it asks:In each figure below (A – F) the Moon is shown in a particular phase along with the position in the sky that the Moon would have at one time during the day (or night). The dark areas on each moon figure show the unlit portions of the Moon visible from Earth at that time. Assume that sunset occurs at 6 pm and that sunrise occurs at 6 am.

    I don't get the relation between the phase of the moon, the position of the sky that it is in, and how in the world im supposed to be able to determine what time of the day it rises.

    Perhpas someone knows of a chart of simulation that might help me on this?? My prof used the "moon phases simulator", and made it look so simple, but I am just not getting it :(

    Help please.
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Sep 9, 2012 #2


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    Staff: Mentor

    Your link is not working, and what you wrote doesn't say what the question is. Or at least I am unable to find out.
  4. Sep 9, 2012 #3


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    Consider the situation at sunset. When the Moon is rising just as the Sun sets, the Earth, Moon and Sun lie in a straight line and its entire face is illuminated.... a full Moon. When the Moon lies between the Earth and Sun, the three also lie along a straight line but we are looking at the shadowed face of the Moon... a new Moon. Halfway between that we have the half-illuminated Moon. It is situated halfway between the east and west.... directly overhead.

    Change the time to dawn now. The full Moon sets just as the Sun rises and the new Moon still lies between Earth and the Sun. We still don't see the new Moon. Halfway between those two cases will position the Moon directly overhead but now the other half of the Moon is illuminated. Interesting that the half-illuminated Moon (first and last quarter) describes a right angle with the Earth and Sun.

    Hope it helps.
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