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Why the hottest days of summer are the "dog days"
The term "dog days" has a celestial origin.
August 10th, 2012
08:31 AM ET

Why the hottest days of summer are the "dog days"

By Jim Roope, CNN

(CNN) – The hottest days of the summer in the Northern hemisphere are commonly called the "dog days."

It turns out the name has nothing to do with man's best friend.

It comes from the star Sirius, the brightest star in the night sky. Sirius is also called “the dog star” because it is found in the constellation, Canis Major, or “the greater dog.”

Dr. Ann Marie Cody, Astronomer with the California Institute of Technology in Pasadena, California, said this time of year, Sirius is situated in the sky very close to the sun.

[1:40] “The Romans and other ancient people knew this and they understood that when the sweltering summer heat set in, Sirius was right up there next to the sun even though it was not visible,” said Cody. “They concluded that the presence of this bright star was actually contributing heat and all the associated summertime misery to the Earth.”

But now we understand that it's the tilt of the Earth on its axis, the angle of the light rays and the duration of daytime that makes the difference in heating, not the “dog star.” That still doesn’t stop us from using the “dog days” as an excuse to escape.

Some take last minute trips to cooler spots like the beach. Some take time off from work to relax and stay out of the heat. And for others, because so many school districts are starting earlier, these hot, sticky days mark the end of their summer.

[2:57] “In August you’re school-supply buying, going to the dentist, get your check up, filling out this form, football practice. It’s no longer summer vacation,” said Celina Simic, a mother of four with kids spread from kindergarten to high school.

How do you spend the "dog days" of summer?  Let us know in the comment section below.

soundoff (2 Responses)
  1. lionelsoni

    The tilt of the Earth on its axis is indeed the cause of the heat; but that tilt does not bring the Earth closer to the sun. In fact, the Earth is somewhat farther from the sun during the northern-hemisphere summer than in the winter.

    August 16, 2012 at 1:01 pm | Report abuse |
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