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What’s special about a full moon?

The September 16 full moon is the Northern Hemisphere’s Harvest Moon. But all full moons are special. Here’s why.

Ed Bettina Berg in Las Vegas, Nevada contributed this image of the 2016 Harvest Moon.

Ed Bettina Berg in Las Vegas, Nevada contributed this image of the 2016 Harvest Moon. More photos of this year’s Harvest Moon.

Full moon comes on September 16, 2016 at 1905 UTC. Translate to your time zone. This is the Northern Hemisphere’s Harvest Moon, the full moon closest to the September equinox.

So this full moon is special to us in the northern Hemisphere, but then … every full moon is special. What’s so special about a full moon? Why does it tug our heartstrings? And why does a full moon look full, in contrast to other phases of the moon?

You’ll have to answer the first two questions for yourself, but here’s the answer to the third. At full moon, we’re seeing all of the moon’s day side.

At full moon, the moon and sun are on a line, with Earth in between. It’s as though Earth is the fulcrum of a seesaw, and the moon and sun are sitting on either end of the seesaw.

So as the sun sets in the west, the full moon rises. When the sun is below our feet at midnight, the full moon is highest in the sky. When the sun rises again at dawn, the full moon is setting. We all love line-ups of things in the heavens. Could it be the alignment of the sun, Earth and moon that causes us to feel a special connection with the full moon?

If there’s a lunar eclipse – as there is for the September 16 full moon – it must happen at full moon. It’s only at the full moon phase that Earth’s shadow, extending opposite the sun, can fall on the moon’s face.

In many ways, a full moon is the opposite of a new moon. At both the new and full phases, the moon is on a line with the Earth and sun. At new moon, the moon is in the middle position along the line. At full moon, Earth is in the middle.

Full moon always comes about two weeks after new moon, when the moon is midway around in its orbit of Earth, as measured from one new moon to the next.

Jarred Donkersley caught this photo at the Vincent Thomas Bridge in San Pedro, California. He wrote:

Jarred Donkersley in San Pedro, California caught the September 16 Harvest Moon and wrote: “I’ve been shooting moonrises and moonsets for 3 years and have never really seen a lot of other photographers as I’m usually atop a random parking garage, hill, or mountain. Tonight I counted 7 other photographers!”

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Four keys to understanding moon phases

Where’s the moon? Waxing crescent
Where’s the moon? First quarter
Where’s the moon? Waxing gibbous
What’s special about a full moon?
Where’s the moon? Waning gibbous
Where’s the moon? Last quarter
Where’s the moon? Waning crescent
Where’s the moon? New phase

Moon in 2016: Phases, cycles, eclipses, supermoons and more

Bottom line: A full moon looks full because it’s opposite Earth from the sun, showing us its fully lighted hemisphere or day side.

Each full moon has its own name. Here are the names of all the full moons

Deborah Byrd

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