Dog Days Of Summer

I always thought that the expression “dog days of summer” meant that it was so hot your dog was willing to get in a paddling pool with a baby. I was wrong!

The phrase actually has a celestial origin.

In ancient times, when the night sky was unobscured by artificial lights and smog, different groups of peoples in different parts of the world drew images in the sky by “connecting the dots” of stars. The images drawn were dependent upon the culture: The Chinese saw different images than the Native Americans, who saw different pictures than the Europeans. These star pictures are now called constellations, and the constellations that are now mapped out in the sky come from our European ancestors.

They saw images of bears, (Ursa Major and Ursa Minor), twins, (Gemini), a bull, (Taurus), and others, including dogs, (Canis Major and Canis Minor).

The brightest of the stars in Canis Major (the big dog) is Sirius, which also happens to be the brightest star in the night sky. In fact, it is so bright that the ancient Romans thought that the earth received heat from it. Look for it in the southern sky (viewed from northern latitudes) during January.

In the summer, however, Sirius, the “dog star,” rises and sets with the sun. During late July Sirius is in conjunction with the sun, and the ancients believed that its heat added to the heat of the sun, creating a stretch of hot and sultry weather. They named this period of time, from 20 days before the conjunction to 20 days after, “dog days” after the dog star.

The conjunction of Sirius with the sun varies somewhat with latitude. And the “precession of the equinoxes” (a gradual drifting of the constellations over time) means that the constellations today are not in exactly the same place in the sky as they were in ancient Rome.

Today, dog days occur during the period between July 3 and August 11. Although it is certainly the warmest period of the summer, the heat is not due to the added radiation from a far-away star, regardless of its brightness. No, the heat of summer is a direct result of the earth’s tilt.

8 thoughts on “Dog Days Of Summer

  1. Nicole says:

    Great explanation of the science behind it. I was too lazy to verbalize all this in my post. :)

  2. You investigate and share the most amazing facts and information at times. I am definitely using the info in this post as my trivia question in our nightly game of trivia during dinner tonight.

  3. MsSopia says:

    I love these bits of trivia. They rev up my imagination.

  4. jmgoyder says:

    I love learning these new things!

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