Look up tonight, and you'll see a rare sight: a 'Worm Moon'.

It's happening only twice this year. There'll be one today at 7:51pm ET and one on March 31 at 9:42pm ET.

Yes, those dates line up perfectly with the full moons this month - that's because a Worm Moon is just a term for a full moon that happens in March.

Some people call March's full moons Sap Moons, while others refer to them as Crow Moons. But they're all just big, round moons in the sky.

A full moon is visible when the Earth is in between the moon and the sun, fully illuminating it from our perspective.

The term Worm Moon is assigned to March because this is the time of year when more worms begin slithering out of the thawing ground in the northern hemisphere.

The second full moon in a calendar month is sometimes called a blue moon, so the one later in March could be considered a "blue Worm Moon." But it's not technically different from any other full moon of the year.

There are a ton of other names for full moons throughout the year - here are some of them:

  • January: Wolf Moon, Old Moon.
  • February: Snow Moon, Hunger Moon.
  • March: Worm Moon, Sap Moon, Crow Moon.
  • April: Pink Moon, Grass Moon, Fish Moon.
  • May: Flower Moon, Planting Moon.
  • June: Strawberry Moon, Rose Moon.
  • July: Buck Moon, Thunder Moon, Hay Moon.
  • August: Sturgeon Moon, Red Moon.
  • September: Harvest Moon, Corn Moon.
  • October: Hunter's Moon.
  • November: Beaver Moon, Frost Moon.
  • December: Cold Moon, Long Night's Moon.

You can read more about the monthly moon names here.

The terms are nothing more than a reminder that people have for centuries marked their days on Earth by looking into the sky, noting the passing of weeks and months as the moon waxes and wanes.

So take a peek at that Worm Moon in the sky on Thursday night - a full moon is always a little exciting.

And if you miss your chance, remember there's another one coming in a few weeks.

This article was originally published by Business Insider.

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