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A Daytime Full Moon?

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A Daytime Full Moon?

Full Moons are a topic that gets everyone excited around here. Every time we put up a story, video, or social media post about an upcoming Full Moon, Farmers’ Almanac fans respond, and our Moon Phase Calendar remains one of the most popular features on the site.

One things that causes a lot of confusion, though, is the times we give for the Full Moon. Sometimes they fall in the middle of the day, when the Moon can’t actually be seen. How is that possible?

The answer lies in the definition of what a Full Moon actually is. Most people think the full Moon lasts for a couple of days, because the Moon appears full for two or three nights, on average. Technically, though, the Moon is only considered full for one specific day. Before and after that, the Moon is really either in waxing or waning gibbous stage respectively, no matter how full it appears.

If you want to get even more technical, though, the Moon is really only “full” for a brief instant. The astronomical definition of a full Moon is when the Sun, Earth, and Moon are all in perfect alignment, forming a straight line, with the Moon on the exact opposite side of the Earth from the Sun. From this position, the Sun’s light shines directly onto the portion of the Moon visible to us, creating a full, bright circle of light.

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The time that this brief instant takes place is the time you see when you look at a Moon phase calendar. Depending on where you live in the world, the Moon may or may not be visible to you at this exact time, but it is visible to someone somewhere. If the full Moon takes place near midnight, it will be visible to you. If it takes place near noon, it will be visible to people living on the opposite side of the globe.

By the time it gets dark in your part of the world, the Moon will still look full, and be considered full for the entire calendar day. Because the Moon is always in motion, revolving around the Earth at a rate of one full circle every 28 days, it doesn’t stay perfectly aligned for long. In just one week, the Moon will reach its quarter phase and be “half full,” and in two weeks it will become new and disappear completely from view (this is because it has lined up with the Earth and Sun, but between the two this time, and doesn’t reflect any of the Sun’s light back to us).

That’s why the time of the full Moon can fall during daylight hours, regardless of whether or not you can actually see the Moon at that time. This type of daytime full Moon is based purely on astronomical calculations.

Another type of daytime Moon occurs when you can see the Moon in broad daylight. This often happens near the quarter phases, and we have written about that phenomenon here.

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1 Susan Higgins { 06.09.17 at 8:43 am }

Hi Angela, we have that information in the Calendar pages of the Almanac (at the top of the page for each month), and while not a list, you can find that information on Moon Phases calendar online here:

2 Angela D Eldridge { 06.08.17 at 8:01 pm }

I kelt searching for the new moon dates for 2017 nothing would come up

3 Tony { 01.27.16 at 6:15 pm }

You have missed the point. It has been observed by astronomers at least 5o times in history of the FULL MOON visible in the daylight. That’s the issue.

4 Cryptoctopus { 08.13.15 at 1:12 am }

If the sun is 93 million miles away and the moon 232 000 miles away. How can we both see them in the sky at the same time?

Under those assumptions…it is impossible.

It’s hard to swallow…but the earth is flat.
(Think about longer than a second before dismissing this idea)

This might help come to grasp with reality:

5 Brenda C Sharp { 07.31.15 at 11:35 am }

Anything about the moon is so interesting. My son took pictures last nite and we will do so again tonite. Thanks for your information.

6 Roseanna { 07.31.15 at 8:18 am }

Great..simply explained. Thx.

7 Sandy B { 07.31.15 at 7:32 am }

Thank you – great information!

8 raenna fuchs { 07.31.15 at 4:30 am }

Love the infomation you gave on the blue moon

9 Verna { 07.30.15 at 11:51 pm }

Love this info on the Blue Moon.! Will e watching Friday!
Thank you for making all information on all subjects so readable and interesting!!

10 elaine pantovich { 07.10.13 at 9:16 am }

Summer lovers moon

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