This Is Why It's Called "The Dog Days of Summer"

The phrase has some literal star power behind it.

The "dog days of summer" refers to the hottest, sweatiest, most oppressively sweltering stretch of the year. And though you might think the phrase comes from worn-out, overheated pups laying lazily in the sun, too hot to play even one round fetch, you'd be incorrect. Turns out, the phrase "dog days of summer" has very little to do with dogs at all.

According to Christopher Klein of The History Channel, the phrase dates all the way back to ancient times, when civilizations tracked the seasons by sky patterns. During the hottest days of the summer, ancient Romans and Greeks noticed that Sirius—the brightest star in the sky—set and rose alongside the sun. And as Jay Holberg, the author of Sirius: Brightest Diamond in the Night Sky, explains, Sirius is known as the "dog star" because it's the brightest star in constellation Canis Major, which literally translates to "greater dog" in Latin.

Since Sirius moved in tandem with the sun during this time of immense heat, ancient civilizations believed the star was radiating all that extra heat to planet Earth. The Romans, therefore, referred to the phenomenon as "diēs caniculārēs," which translates to "dog days."

Thanks to advances in modern science, we now know that though Sirius is indeed the brightest star in the sky, it's more than eight light-years away from the Earth. One light year, per the scientists at NASA, equates to nearly six trillion miles. For comparison's sake, NASA puts our own sun as 92 million miles away from the equator. You don't need to be a rocket scientist to tell that Sirius is way, way too far away from our solar system to contribute a single joule of heat to Earth.

Additionally, our dog days are hardly the same dog days of ancient eras. The Old Farmer's Almanac says the current precise dog days of summer fall between July 3 and August 11. The ancient Romans and Greeks, however, are said to have experienced their dog days starting in late July. What's more, as the universe shifts and changes and shrinks and expands at a never-ending rate, Sirius changes locations in the night sky.

"In 26,000 years, the dog days would completely move all around the sky," Bradley Schaefer, a professor of physics and astronomy at Louisiana State University, told National Geographic. "Roughly 13,000 years from now, Sirius will be rising with the sun in mid-winter."

So basically, we'll eventually have the dog days of… winter? Cool! And for more amazing trivia about the hottest time of year, here are 40 Facts That Will Make You So Excited for Summer.

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