Science of the Harvest Supermoon
Science of the Harvest Supermoon
Non-supermoon vs. Supermoon. Image: NASA Science
When we talk about a Supermoon, we’re not referring to Clark Kent’s secret identity. A “super” moon occurs when a full moon coincides with the Moon’s orbit around the Earth, which is closest in its elliptical orbit, known as perigee. This means the Moon’s appearance in the sky is 14% to 30% larger and brighter than that of a regular full moon, not a supermoon. Because the Moon is closer to the Earth, tides can be higher than usual. And, of course, there are the werewolves to consider.
The term “supermoon” was coined by astrologer Richard Nolle in 1979 as either a new or full Moon that occurs when the Moon is within 90% of its closest distance to Earth.
Supermoons may or may not be “Super Blue Moons,” having nothing to do with an election year or the song by Rodgers and Hart that was popularized by The Marcels. As I’ve explained in this article on blue moons, these occur when there are more than two full moons in the month.
But tonight is not a blue moon. Instead, it’s a…
Harvest Moon
Full Moon in August. Image: Wikimedia
The Maine Farmer’s Almanac first published “Indian” names for the full Moons in the 1930s, and these names have become widely known and used. According to this almanac, as the full Moon in September, the Algonquin tribes in what is now the northeastern USA called this the Corn Moon. This was the time for harvesting their main staple crops of corn, pumpkins, squash, beans, and wild rice.
As the full Moon that is closest to the Autumnal Equinox (September 22, 2025), this is the Harvest Moon. The first known written use of this name in the English language – according to the Oxford English Dictionary – was in 1706.
In Europe, the names for this full Moon are the Fruit Moon, as several fruits ripen as the end of summer approaches, and the Barley Moon, derived from barley harvesting and threshing.
In China and some other Asian countries, this full Moon corresponds with the Mid-Autumn Festival, a traditional harvest festival. Other names for this festival include the Moon Festival, the Mooncake Festival (when moon cookies and cakes are traditionally served), and the Reunion Festival (with wives visiting their parents and returning to celebrate with their husbands and parents).
Is this Different from the Hunter’s Moon?
The Hunter’s Moon is typically the full moon that follows the Harvest Moon, usually occurring in October. It is named because hunters could easily track animals in the fields after the harvest. While these are distinct definitions, there can be overlap.
Every three years or so, as in this year of 2025, the Hunter’s Moon is also known as the Harvest Moon.
Bill Petro, your friendly neighborhood historian
billpetro.com
