The Dog Days of Summer

October 5, 2008

“When Sirius parches the head and knees and the body is dried up by reason of the heat, then sit in the shade and drink.” The Greek poet Hesiod wrote these lines 3,000 years ago referring to that stretch of summer that came to be known as the ‘Dog Days.’ Sirius is the brightest star in the constellation Canis Major (the Big Dog) and its name comes from the Greek word for “scorching.” 

Sirius is more than three times the size of our sun and is the brightest star in the night sky, even at 9 light years distance. The Dog Star is so bright that the ancient Romans believed that the Earth was heated by it at night. 

In the summer months Sirius rises and sets with the sun. During late July Sirius is in conjunction with the sun and they believed that the combined heat of the Sun and the Dog Star created this stretch of uncomfortably hot weather. The Romans named this period, from 20 days before conjunction to 20 days after, the Dog Days. 

Of course, today we understand that the heat of the mid-summer season is a result of the Earth’s tilt towards the sun, not from the added ‘heat’ of the Dog Star. Due to the ‘precession of the equinoxes,’ the positions of the constellations have drifted over time; the stars are not in the same place as they were in the night sky in ancient Rome. Today the Dog Days are specifically July 3 through August 11. But this sense has been loosened in popular usage to refer to any stretch of hot, humid weather in the summer.


Got something to say?

You must be logged in to post a comment.