Ghosts and goblins and ghouls, oh my!

That's what many of us will be thinking this coming week as Halloween arrives, and trick-or-treaters pound excitedly at our doors. You will likely encounter monsters, super-heroes, politicians and singers, but keep track of how many astronomers show up at your house.

If my guess is correct, you won't see any, though it was nice to see on a recent episode of the sitcom "Young Sheldon," this brilliant young man dressed up one year as Carl Sagan! I wish just one "astronomer" would appear my door, especially since Halloween has an astronomical origin.

It all comes down to the seasons and to our planet's annual orbit around the sun.

Today we associate the beginning of each season with the equinoxes and solstices. Recently, we heard the TV weather reporters explain that autumn began on Sept. 22 – the autumnal equinox – when the sun crossed the celestial equator on its way southward. Soon we'll be hearing them say that winter will begin on Dec. 21 – the winter solstice – when the sun reaches its southernmost point in daytime sky and once again begins its northward journey in the heavens.

We hardly ever think about these details; we just recognize these dates as the beginning of new seasons, and that's that, but it wasn't always this way.

To ancient Germanic and Celtic societies, for example, the equinoxes and solstices marked not the beginning of the seasons, but their midpoints. They knew the seasonal beginnings to occur on "cross-quarter" dates: the points midway between the equinoxes and the solstices.

Four cross-quarter dates exist throughout the year, and each has become a minor holiday: Feb. 2 (Groundhog Day), May 1 (May Day), Aug. 1 (Lammas Day) and Oct. 31 (Halloween).

To the Celts, winter began with Halloween, or as they called it, "Samhain" (summer's end), which marked the transition between summer and winter, light and dark, life and death. This was also the Celtic New Year's Eve, when people celebrated the occasion with a great fire festival to encourage the sun not to vanish. On this frightful evening, people danced around massive bonfires to repel demons but left their doors open in hopes that kind spirits of loved ones might join them around their hearths.

So where did all the costumed ghosts and goblins and ghouls of modern Halloween come in? Well, that originates far back in history as well. It was in later pagan and Christian traditions that, at this time of year, people went out in masks and robes to frighten away evil spirits; some even traveled from farm to farm carrying hollow turnips with candles inside and demanding food to honor an old god, Muck Olla.

It's easy to see how these ancient traditions have influenced our modern holiday customs around this time of year. But this Halloween, while you're dressing up in scary outfits or quietly pilfering chocolate bars from your kids' trick-or-treat bags, think about the celestial origin of this holiday.

You might even consider attending a Halloween party dressed as an astronomer though. If you should choose me as your subject, you may send people shrieking out the door!

Visit Dennis Mammana at dennismammana.com.