Why can I see the moon during the day?

A few months ago, one of our many readers posed the question asking ‘Why is it that I can see the moon sometimes during the day? I thought the moon only came out at night?’

newmoon1

Dear Reader – terrific question.

Seeing the moon during the day can be a bit odd. A great way to visualize this is to remember that we are on a round ball orbiting around the sun. The moon, is also a round ball orbiting around the Earth. All the while, Earth itself…rotates.

It’s summer/fall season so lets imagine a summer/fall experiment. The next time you’re sitting around a campfire, hold whatever beverage you have you in your hand in front of you between you and the fire – you probably can’t read the label – it’s too dark! This is an example of a ‘New Moon’ when the Moon is between the sun and earth at such an angle that you could only tell it was there if only it passed in front of the sun itself (that’s an eclipse, we’ll get to that in another blog).

If you hold your beverage off to your side, you’ll be able to read just a portion of the label, the portion of the label that is facing the fire that you can also see because that beverage is in a rounded container. This would be an example of a first quarter or third quarter moon.

Lastly, if you turn around and hold the beverage behind you using the fire to illuminate it, you can clearly read the entire label – this being a Full Moon.

Now that you’ve just spun around in circles while drinking around a fire…what does this all mean!?!?

When you had the can off to your side, you could still easily see the fire AND the reflecting light from the fire off the can at the same time. Such is the moon during the day. At times the Moon’s orbit is positioned in a way that still puts it in the ‘daytime sky’ but is at an angle that also can reflect light back down to Earth from the sun. Here’s an illustration I stole from http://www.UniverseToday.com to help explain..

moondiagram

The sun (our campfire) is off to the right of this image, the Moon is your beverage, and you are the Earth. The little images of the Moon are what it would look like to YOU the viewer up in the sky, not to scale of this illustration (my only complaint with it). If it ever gets below 85 degrees at night again I’ll try my campfire analogy for myself and  get a few pictures for ‘evidence.’ It might take a six-pack of tries, but I’ll get it eventually.

-JZH

 

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