It's that time of year when witches, goblins and black cats crowd store shelves, backlit by the light of full Moon decorations. It's certainly a Halloween classic, but what does the Moon actually have to do with Halloween?
It's not as obvious as you might think. The Moon is rarely full on Halloween. A full Moon illuminates trick-or-treaters an average of once every 19 years; the last time was in 2001, and the next will be in 2020. (If you count almost-full, it's about once every six years.)
October 31 marks a solar holiday, called a "cross-quarter" day. Imagine the two equinoxes and two solstices dividing the calendar year into four quarters. The cross quarter days divide these four quarters in half again, making 8 slices of the annual pie. We call the cut between the fall equinox and the winter solstice Halloween.
The name Halloween is a contraction of the term "All Hallows Eve," or the night before All Saints Day. All Hallow's Eve was originally practiced by the Catholic Church in May, but moved to Nov. 1 in the 8th century to coincide with pagan festivals of the dead.
On the British Isles, the ancient Celts called their festival of the dead Samhain (pronounced sow-en), meaning "end of summer." As the weather turned colder, people's world turned to focus on the inner life -- both indoors and within the self.
Such turning points were considered "threshold" moments. Threshholds are where two worlds intersect, and were considered particularly potent times. Samhain was known as the time of year when veil between the world of the living and world of the dead is thinnest, allowing spirits to travel back and visit the land of the living.
In ancient astral magic, the Moon served as a mediator between world of the spirits and the world of the living. In this guise, she was invoked to protect home and hearth from strange forces wandering the night.
During Samhain, the Celts would carve faces on turnips to serve as protective talismans. The white, round root was a symbolic reminder of the white, round face of the Moon. Luna both lit the way home for the friendly spirits of family and friends, and warded the gates to those unwelcome.
Turnips, however, aren't easy to carve. So when Irish and Scottish families immigrated to the Americas, they switched to the more accessible and plentiful pumpkin for crafting their Halloween talismans.
And so each time you carve a pumpkin, you are participating in a long tradition of invoking the protective powers of the Moon. The candlelight in the pumpkins mimics the Moon's illumination, even on those Halloween's when she's not in her full Moon phase.