July 3, 2015

It Happened on July 3rd

The Dog Days of Summer

© Evgeniy Lukyanov/sxc.hu
I've been acquainted with the phrase "dog days of summer" for as long as I can remember, but I never thought too much about what it actually meant. I knew it referred to the hottest part of the summer -- those lazy, sultry days when it's really too hot to feel like doing anything. I suppose I thought that's why they were called the dog days. I know that in heat like that, all I feel like doing is lying under the porch with my tongue hanging out.

As it turns out, the phrase has nothing to do with a dog's laziness, either real or perceived. The Romans named this time of year after the Dog Star, Sirius. Sirius is the brightest star in the constellation known as Canis Major, the Large Dog. At a certain time of year, Sirius rose above the horizon at just about the same time as the sun did. (Well, actually a second or two before, so that you can actually see it.) The Romans thought that the star was so bright that it actually made the weather hotter.

Sirius A & B - artist's impression, provided by NASA.
The Egyptians, too, were cognizant of Sirius. They called it Sopdet, which was translated into Greek as Sothis. In fact, they based their calendar on Sopdet's heliacal rising, which is what you call the rising of a star just before sunrise. Since this occurred just before the Nile flooded, Sirius made a handy "watchdog" for the event.

To the Ancient Greeks, the Dog Days were a time of evil and trouble. Because the weather was unsettled in the early summer, and the Dog Star was so bright, it tended to twinkle more than usual. The Greeks believed that this was because of malevolent emanations. People under Sirius's influence were called "star-struck." Just how bad the evil emanations would be in any given year depended on Sirius's appearance: if it shone clear and bright, it would be a good year; if it twinkled or was dim, you could expect pestilence. The Romans carried things one step farther, and sacrificed a brown dog to appease the gods.

Sirius is actually quite a bright star. In fact, it's the brightest in our heavens, and twice as bright as the next brightest. It can be seen by nearly every one on earth -- the only place you can't see it is if you live north of 73 degrees latitude. It can even be seen in daylight, under very special conditions. (You'd have to be at a high altitude, and have a very clear sky, Sirius directly overhead, and the sun low on the horizon. Oh, and it helps if you're in the Southern Hemisphere.) One reason Sirius is so bright is that it's actually a binary star.

To the Romans, the Dog Days took place from July 24th through August 24th, more or less. The dates have changed since ancient times, however, due to a phenomenon called the procession of the equinoxes. Put simply, that just means that the constellations move around a bit over the years. This year, it will take place in early August. The exact date will depend on what latitude you live in.

The Old Farmer's Almanac has been around
for quite awhile.
So why am I calling July 3rd the beginning of the Dog Days of Summer? The Old Farmer's Almanac gives the traditional dates of the Dog Days as July 3rd through August 11th. Modern mythology is not much different than that of the ancients. According to the Almanac,

"Dog Days bright and clear
Indicate a Happy Year.
But when accompanied by rain,
For better times our hopes are vain."

If it's good enough for the Old Farmer, it's good enough for me.

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