The December full moon has a quiet claim to fame. Called the Cold Moon, it follows the longest route across the night sky. This happens because of the way Earth tilts in winter. When the Northern Hemisphere leans away from the Sun, the Sun sits low in the sky during the day, and the full moon sits directly opposite it. This puts the moon high overhead and gives it a very long arc from moonrise to moonset.

The result is simple. December’s full moon rises earlier, sets later, and stays above the horizon for more hours than any other full moon. For people who once relied on the night sky to mark the seasons, this bright winter moon was a reliable signal that the deepest part of the cold season had arrived.

If you are curious why the Moon is so important to the Earth, this fact uncovers the larger story.