Today’s factismal: Today is the first day of Summer, the twentieth day of Summer, and the middle of Summer.
Right now, you are probably seeing lots of posts complaining that today is only the first day of Summer and it is already unbearably hot. (Of course, if you live in the Southern hemisphere, you are probably hearing lots of people complain about how everyone ignores the fact that it is Winter where they live and those dumb folks in the North never remember it.) Well, we can’t do much about the heat, but we can do something about it only being the first day of Summer because it isn’t. Today actually marks the first day of Summer for the astronomers. For a meteorologist, today is the twentieth day of Summer. And for folks who read Shakespeare, it is the middle of Summer!
How can all three of them be right?The answer lies, as it so often does, in the ineluctable propensity of mankind to name things. Back in the days of the early Roman kings (about 2,700 years ago), the calendar ran from late spring to early winter and then went silent for a couple of months. The Romans held various fertility and harvest festivals to celebrate the seasons, but the actual date when those were held slipped around a bit thanks to those missing two months. It wasn’t until Julius Caesar fixed the calendar that we started seeing folks who could say with any authority (a legion of armed men is authority, right?) that Spring was officially over and Summer had begun.
The interesting thing is that, while the various Roman provinces didn’t like the Romans very much (after all, what had Rome done for them other than the aqueducts, sanitation, roads, education, and the wine?), they loved the calendar because it made it easier for them to observe their religious rites and mark their seasons. And one of the most influential (at least in Europe) set of seasons was the one that modern pagans call “the Wheel of the Year”, which divided the year into four seasons (Spring, Summer, Winter, and Fall) and arranged them so that the middle of each season happened on an astronomically significant date. The middle of Winter would show up on December 20 (the Winter Solstice), the middle of Spring would occur on March 20 (the Vernal Equinox), the middle of Summer would be on June 20 (the Summer Solstice), and the middle of Fall would roll in on September 21 (the Autumnal Equinox). This method of timing the seasons lasted for more than 1,900 years; you can see its influence in things such as Shakespeare’s “Midsummer’s Night’s Dream” which takes place on the Summer solstice. And while the dates have slipped a bit due to the Earth’s wobble in its orbit, the basic idea remains and is celebrated in many countries.
But as we moved into the 20th century, we decided that those dates didn’t work well for us (mainly because there is nothing special to mark February first as the start of Spring). So we came up with a new system. Actually, we came up with two new systems. Around 1950, the meteorologists decided that the seasons would start on the first day of a specific month, so that each season was roughly the same length of time. Spring ran March, April, and May, Summer took up June, July, and August, Fall was September, October, and November, and Winter was December, January, and February. (These seasons are generally referred to as “meteorological spring” etc.)
At about the same time, the astronomers decided that they weren’t going to let no stinking pagans decide when the seasons started based on obsolete astrological superstitions; instead, they’d start the seasons based on the stars. So the astronomers decreed that Spring would begin on the Vernal Equinox, Summer would come in on the Summer Solstice, Fall would commence on the Autumnal Equinox, and Winter would hold sway beginning on the Winter Solstice. That this effectively shifted the seasons by half a wavelength was irrelevant; it just made more sense to the astronomers.(These seasons are generally referred to as “astronomical spring” etc.)
So, as a result, we now have three different dates to start each season. Of course, Mama Nature is famous for not reading calendars (as anyone who has been caught in a May snowstorm can attest); she starts her seasons when she wants and marks it by changes in the plants and animals. And it turns out that there are a lot of scientists who are more interested in reading her calendar than man’s. If you would like to help them do so by recording when the leaves change color or the butterflies leave or the buds blossom in your area, then why not write a few pages in Nature’s Notebook?