Wednesday, September 29, 2010
Driving home the other night, a massive harvest moon filled the sky. Now harvest moons have been the subject of songs (think Neil Young - I was going to put the sound clip on, but just about dozed off when listening to it - sorry all you Neil Young fans), fiction, artwork, festivals and even some sort of gaming kind of thing, but what actually IS a harvest moon?
So what is a harvest moon?
The harvest moon is the moon at or about the period of fullness that is nearest to the autumnal equinox (or for us in the summer hemisphere, the spring equinox!). It signifies the southern hemisphere’s first full moon of spring.
Because Earth doesn’t orbit upright, but is instead tilted on its axis by 23-and-a-half degrees, Earth’s northern and southern hemispheres trade places in receiving the sun’s light and warmth most directly. We have an equinox twice a year – spring and autumn – when the tilt of the Earth’s axis and Earth’s orbit around the sun combine in such a way that the axis is inclined neither away from nor toward the sun. It's almost an exact mirror image of each other, with Earth’s two hemispheres receiving the sun’s rays equally. Night and day are approximately equal in length. The name ‘equinox’ comes from the Latin aequus (equal) and nox (night). But, since Earth never stops moving around the sun, these days of equal sunlight and night will change quickly.
So the 2010 equinox – September 22 or 23 depending on the time zone, is a seasonal signpost in Earth’s orbit around the sun.
Often, the harvest moon seems to be bigger or brighter or more colorful than other full moons. The warm colour of the moon shortly after it rises is caused by light from the moon passing through a greater amount of atmospheric particles than when the moon is overhead. The atmosphere scatters the bluish component of moonlight (which is really reflected white light from the sun), but allows the reddish component of the light to travel a straighter path to one's eyes. Hence all celestial bodies look reddish when they are low in the sky.
The harvest moon I just saw was a significant one as it fell smack bang on the equinox. In the Northern Hemisphere, this was known as the Super Harvest Moon, and was appearing for the first time in 20 years, and it won't happen again until 2029.
I'm guessing that the innocent question of my 10 year old "What's a harvest moon mum" as we drove along looking at the moon together won't be repeated by my 29 year old when the next Super Harvest Moon appears.
Makes me feel a little sad.
And more than a little old!
Did you see the moon?
Labels: My Year of Self Improvement