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On which days can I see the Moon in the evening / morning and why is this so?

What factors dictate if the moon is visible in the evening or morning (vs. at night)? My 15-month old loves to see the moon, but she is rarely awake at night so we always look for the moon early in the morning and in the evenings. I'm just curious why it is sometimes visible and sometimes not. (Obviously cloud cover is a factor, but outside of that.)

Background: I am a curious person with a very curious daughter. Thanks so much.

Dear Parent,

When the moon is visible depends where it is in its orbit. Look at the following image:

Image: Sun, Earth, Moon's Orbit

The Earth turns counter clockwise and the Moon follows the black circle counter clockwise. The labels AM, Noon, PM, Midnight indicate your location on the Earth during the day. The labels New, 1st Quarter, Full and 3rd Quarter label the positions of the Moon along its orbit. The Sun is on the left side.

As you can see the Moon will be visible in the evening (PM side of the Earth) starting a few days past new moon, during first quarter until a few days before full moon. It will be visible in the morning (AM side of the Earth) starting at full moon, during third quarter until a few days before new moon. The Moon will not be visible for a few days around new moon because the sunlit side of the Moon is facing away from Earth, towards the Sun. Consult your calendar for the phases of the Moon.

A fun thing to do is to make a picture of the Earth and the Sun with the path of the Moon like the image above and have a Moon cutout to move around the Earth. You stick the cutout Moon onto the orbit and can move it every few days to the Moon's current position. This will help you (and maybe later your child) to know when to go out and see the Moon. This "Moon Clock" can also be used to understand the phases of the Moon by keeping the bright side of the Moon facing the Sun.


Marc Berthoud

September 2006, Marc Berthoud (more by Marc Berthoud) (Like this Answer)

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