Phrase Nerd Friday: Dog Days of Summer

First, some music. I find this video strangely disturbing. Must be the make-up. Or something:




Unlike the song, the Dog Days are just beginning. But where does that phrase come from? Why 'Dog Days'? Glad you asked.

I have always thought of the Dog Days of summer as being that period in August, which, where I grew up, tended to be the hottest, laziest time of the year. It was laziest because it was always so damn hot, quite frankly. I never quite understood why it was called Dog Days. The explanations I heard often had to do with actual dogs--they start shedding (which mine is doing now; what a mess!), they sit around and pant, they go crazy from the heat. Maybe all of these are true, but the actual reason goes back to ancient Greece and Rome, and the name has little to do with real dogs.

In the northern hemisphere, the brightest star to be seen in the night sky in winter is Sirius, in the constellation Canis Major. Canis Major follows what is probably the best-known constellation outside the Big Dipper: Orion.

Ooh, fancy!

Orion is in the upper right of the image. I've always thought it looks less like a mighty hunter than a bow-tie stood on its side. Anyway, follow the three stars of Orion's belt down and you point almost directly at Sirius, the Dog Star, in Canis Major, conveniently located in the center of the image above. Sirius is the brightest star visible in the northern hemisphere at night, and also the closest at a mere 8.6 light years away, which means when we look up in mid-January at Sirius, we're looking at light that is 8.6 years old and has traveled a ridiculous distance to get here (remember the speed of light? That would be approximately 186,000 miles--per second. Don't try to figure out how far away it is, it will cause your head to explode).

The name Sirius comes from an old Greek word that means 'scorcher'. It's a safe bet that it's pretty hot there, as it would be at pretty much any star, and that brings us back to the whole 'Dog Days' thing. Back during those Greco-Roman days, Sirius rose at or about the same time as the sun in late July or early August, adding it's heat to an already powerful sun. This was believed to be the cause of the extremely hot days of this period of summer. If only Sirius could send some heat our way during the winter nights when it's high up in the sky!

Sirius no longer rises with the sun at this time (I can't remember why this is, and my brain is not quite functioning well enough this morning to do that last bit of research) of year. Today, it rose about an hour after sunrise. It will rise four minutes earlier each day, while the sun rises an increasing number of minutes later each day, until it eventually starts rising ahead of the sun. This will occur in another week or so.

There you have it. A quick and dirty explanation for the Dog Days of Summer. Have a great weekend, all.


Image from Wikimedia Commons