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Why You Can See the Moon During Daylight Hours

Image: Vaughan Willis
Image: Vaughan Willis

I have a friend whose young son gets incredibly excited when he can see the moon during the day. After several excited shouts of “day moon!” the youngster asks his mom why he can sometimes see the moon when the sun is up, and not just at night. Good question.

Objects in the sky appear to pass overhead on a daily basis because the earth is rotating, or spinning on its axis. For example, at the equator, the sun appears above the horizon for approximately 12 hours a day (though this varies according to the season).

This is true for the moon as well – but the moon is also traveling in an orbit around the Earth.

“And because the moon travels around the Earth, its 12 hours above the horizon aren’t always the same as the sun’s 12 hours,” says Stephen Reynolds, an astrophysicist at NC State who was kind enough to talk to me about this subject. So, sometimes the moon is above the horizon only at night, sometimes only during the day, and sometimes a little of both.

However, any time the moon is above the horizon, you should be able to see it (though it’s a little less obvious in the bright light of day). With one exception.

While we talk about the moon “shining,” it is actually reflecting the light of the sun. And the side of the moon that is lit up is the side that is facing the sun.

Depending on the position of the sun and moon, those of us here on Earth can see different amounts of that “lit” side of the moon. That’s why we see different phases of the moon, such as a full moon or crescent moon.

If the moon is above the horizon, the only time you won’t be able to see it is when it is a “new” moon – meaning that the lit surface of the moon is facing away from the Earth.

Note: Many thanks to Stephen Reynolds, Alumni Distinguished Undergraduate Professor of Physics at NC State, for taking the time to talk with me about “day moons.” Any errors in the above post are mine alone.

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  1. Hi Alex,
    that’s a great question!

    Here’s the answer: “During the day, the brightness of the sky washes out the light from the stars: a region of the sky including a bright star is only very slightly brighter than a region of the sky without a bright star, so your eye cannot notice the difference. However, the region of the sky containing the Moon is much brighter, so you can see it. You can also sometimes see Venus during the day if the conditions are right and you know exactly where to look, but anything dimmer is lost.” — David Palmer and Tim Kallman, NASA

  2. I took an Astronomy class in college. One day the professor took outside, about 10 o’clock in the morning. He pointed us to a particular spot in the sky. One by one, our jaws dropped as we saw Venus. Very cool!

  3. This article is useless and does not answer they key point in the title.

    Only explanation it gives is that the moon is in the sky for almost 12 hrs per day.

    After reading this article can you explain why we can see moon during the day, but not the stars? Starts are there 24 hrs a day, but we can only see them in the night.