Once in a Full Blue Moon

 

Once in a Full Blue Moon

Written by Kristine Manganelli (Somerset County 4-H Coordinator)

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The universe is coming together in a mystical and eerie way, just in time for Halloween this year. On Saturday, October 31, 2020, there will not only be a full moon, but a blue moon…a full blue moon!

The shape of the moon appears slightly different to us each night, here on Earth. However, the moon’s shape is not changing at all, rather our perspective of it is changing.

The moon is described as having 8 phases pictured and described below (from NASA Science Space Place)

🌑 New: We cannot see the Moon when it is a new moon.

🌒 Waxing Crescent: We see the waxing crescent phase as a thin crescent opening to the left.

🌓 First Quarter: We see the first quarter phase as a half moon.

🌔 Waxing Gibbous: The waxing gibbous phase is between a half moon and full moon. Waxing means it is getting bigger.

🌕 Full: We can see the Moon completely illuminated during full moons.

🌖 Waning Gibbous: The waning gibbous phase is between a half moon and full moon. Waning means it is getting smaller.

🌗 Third Quarter: We see the third quarter moon as a half moon, too. It is the opposite half as illuminated in the first quarter moon.

🌘 Waning Crescent: We see the waning crescent phase as a thin crescent opening to the right.

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So if the shape of the moon stays the same, why does it look like it is changing throughout the month? The moon does not produce its own light. What we consider moonlight is a reflection of the sun off the moon’s surface. Since the sun’s light always comes from the same direction, it only illuminates the side of the sun facing Earth. The other side is referred to as the dark side of the moon.

The phase of the moon depends on where it falls in its path, or orbit around the Earth. When the whole illuminated side of the moon is visible to us, it is full. Once the full moon phase has passed, the moon appears to get smaller and smaller until the New moon phase, when it looks like there is no moon at all. During a new moon, the side of the moon facing the earth is dark, because it is not at all illuminated by the sun. From this point, the moon will then appear larger and larger until it reaches its fullness again.

A regular moon cycle lasts around 4 weeks, which is what we consider a month. During a regular moon cycle, there is only one full moon. Full moons are separated by 29 days, but most months are 30 or 31 days long. This fluctuation allows for 2 full moons to rarely fall in the same month.

You may think a blue moon is actually blue in color, but this term refers to the phenomenon when there are two full moons in one month. This only happens every 2 to 3 years, making it a rare occurrence. So the next time you hear someone use the phrase, “once in a blue moon,” you will know what they mean.

Even rarer, is a full moon falling on Halloween; this only happens about once every 19 years, making this Halloween full moon the only one you will see until 2039. The pattern of a full moon falling on the same date every 19 years is a lunar cycle called the Metonic cycle.

Get Outside

Whether you are trick-or-treating, or staying at home for a unique 2020 Halloween experience, be sure to get outside and check out the full moon! Don’t be scared, the fullness of the moon will shine bright in the sky, illuminating your way through the darkness.

Sources:

 
Somerset County 4-H