Once Again, Summer Falls

Tuesday, September 22, marks the occasion of summer giving way to autumn, and the change of season officially occurs at 5:18 pm Eastern Daylight Time.

While there's an old wives' tale about egg balancing on the day of an equinox that is, in fact, completely bogus, there are several attributes and characteristics of this day that are totally cool and completely true.

Our planet happily rotates on an axis that is oriented at a 23-1/2 degree tilt with respect to the Earth's orbital plane. Three months ago at the start of summer, the North Pole reached maximum tilt toward the sun. Three months hence when winter kicks in, it'll be the South Pole's turn. The beginning of fall and spring, however, occur when the axis tilt is neutral with respect to the sun.

The word equinox, cobbled together from Latin words meaning "equal" and "night," is understood to feature 12 hours precisely of both night and day. In truth, if you happen to check your local weather almanac for sunrise and sunset times, you'll probably note that it's actually a few minutes off the exact dozen. This is a result of how light becomes refracted in our atmosphere, as well as to the fact that the Earth is not perfectly spherical.

But on the day of the equinox, the sun does indeed rise in true east, sets in true west, passing directly over the equator on the day.

The North Pole sees its last rays of sunshine today for the next six months, while the South Pole bids adieu to six months of darkness.

And don't look now, but there are only 94 more shopping days left until Christmas.

Image courtesy of Przemyslaw Idzkiewicz, via Wikimedia Commons