Ruff Forecast

Question: The “dog days of summer” comes to us from the ancient Greeks, who associated this series of sultry days with what celestial object?

Answer: Sirius

Here we are again, stuck in that oppressively hot stretch of weather known as the “dog days of summer.” But while it’s easy to envision panting dogs going mad in the midday sun, the expression “dog days” has nothing to do with Scooby Doo or his four-legged friends. It refers to Sirius, otherwise known as the “Dog Star.” The brightest star in the night sky, Sirius is part of the constellation Canis Major (Latin for Greater Dog). Sitting just below Orion the Hunter, the Greeks thought of Canis Major as one of Orion’s hunting dogs—which is where the “Dog Star” came from.

The ancient Greeks (and later, the Romans) noticed that Sirius was visible near the rising sun for several weeks—which always coincided with the hottest days of summer. They concluded that Sirius must be what was responsible for generating extra heat which made those particular days hotter than all the others. That’s why the Greeks named the star Sirius, which means “scorching,” in the first place.

So, those hot days when Sirius could be seen rising and setting with the sun soon became known as the “Dog Days.” And when the Romans came along, they called it Caniculares Dies, or “The Days of the Dog.” But it wasn’t just the extreme heat and humidity of the Dog Days that concerned the Greeks and Romans—they blamed Sirius for all manner of ill fortune. And there are plenty of sources to back this up ...

These references to the “dog days” are classics

In Homer’s Iliad, the Greek warrior Achilles and his shield are compared to “the star they call Orion’s dog—brightest of all but a fatal sign emblazoned on the heavens, it brings such killing fever down on wretched men.”

The Romans didn’t think much of the Dog Star either. In Virgil’s Aeneid, we read about “fiery Sirius, bringer of drought and plague to frail mortals” and how it “rises and saddens the sky with sinister light.”

In addition to making dogs go mad, the Greeks and Romans believed that Sirius was a destructive power that influenced droughts, thunderstorms, poor health, and all-around bad luck. Sirius is innocent of all those things, of course, even for combining with the sun to bring a little extra heat to our summer weather ...

Some Sirius flaws in the “dog days of summer”

So, were the ancient Greeks correct in linking the “dog days of summer”—the period in which Sirius can be seen rising alongside the sun—to the hottest days of the year? Actually, they got it wrong ...

Sure, July and August are usually the hottest months of the year in the Northern Hemisphere. But aside from the fact that the hottest period can vary from year to year, the astronomical “dog days” come at different times depending on a location’s geographic latitude. For example, this year Sirius will rise around mid-August in Athens, Greece. But it happens earlier the farther south you go, and later in the year the farther north you are.

But a bigger problem has to do with the way our spinning planet has a slight wobble to it. We’ll leave the physics to others, but in a nutshell the stars in Earth’s night sky shift independently of our calendar seasons. So, the “dog days” of ancient Greece aren’t even the same as they are today—in fact, because of the shift our “dog days” are several weeks later than they were during ancient times. And in 10,000 years or so, the shift will be so great that Sirius won’t be rising with the sun in the summer months at all. Instead, it will occur in the middle of the winter.

And when that happens, it’s likely that people will start complaining about the “dog days of winter,” that bone-chillingly cold time of year when dogs are driven mad trying to keep warm.

The Greeks and Roman were mistaken, then, in thinking Sirius gave off heat when it and the sun were in conjunction. The ancient Egyptians noticed the Dog Star’s position in the sky, too. But they believed that Sirius co-rising with the sun was related to the annual flooding of the Nile (the annual floods are actually caused by summer rainfall). To the Egyptians, Sirius (or Sothis, the ancient Egyptian name of Sirius and its personification as an Egyptian goddess) was not viewed as a destructive force as it was by the Greeks and Romans. A life-sustaining annual event for the Egyptians, they counted on the floods to bring silt and fertile soil to parts of the desert.

Centuries later, when the Roman Empire fell, the phrase “dog days” lived on. Once we finally understood that Sirius wasn’t heating up the planet and making dogs go mad, the meaning of the expression evolved as well. It’s now used more generally, to refer to the most uncomfortable, humid days of summer. Cultural references to the “dog days of summer” continue to pop up regularly. Charles Dickens used it quite effectively in his holiday classic, A Christmas Carol. To express how cruel Ebenezer Scrooge could be to his underlings, he wrote how he “... carried his own low temperatures always about with him; He iced his office in the dog-days, and didn’t thaw it one degree at Christmas.”

To be clear, Sirius and the sun have little to do with each other—or with us. And while it may be the brightest star in the night sky, Sirius has absolutely no effect on Earth’s weather or climate.

Oh, and before Scooby Doo lodges a complaint, we should let him know that yes, he is indeed a Dog Star. But a star in the celebrity sense, not like the sun and all the actual stars in the heavens ...

A few more fascinating facts about Sirius, the Dog Star

• It wasn’t this dog’s day—Because they believed the star was the cause of the hottest weather of summer, a brown dog was sacrificed at the beginning of Dog Days to appease the rage of Sirius.
• Aww, a cute puppy—Sirius is actually a double star, two stars orbiting each other in a cosmic dance every 50 years. Because the second star is so much smaller—and 10,000 times fainter—than the big Dog Star, the companion star is referred to as “the puppy.”
• Pacino was a true dog star—The classic 1975 crime drama, Dog Day Afternoon, starring Al Pacino, takes place on a swelteringly hot day in Brooklyn (although it was set on August 22, which was 11 days after the “dog days of summer” were over).
• Going with the Flo—The breakout single by the band Florence and the Machine was called Dog Days Are Over, whose lyrics spoke of coming out of a difficult period of despair rather than extreme heat.
• Sirius is seriously big—Sirius is much bigger and brighter than the sun. Imagine the sun as a large cherry tomato. If you put a lime next to the cherry tomato, that would be Sirius. It has twice the mass of our sun, and 333,000 times the mass of planet Earth. It is fortunate that it’s so far away, since if Earth orbited Sirius instead of the sun, it would be instantly fried to a crisp.
• In a galaxy far, far away—As bright as Sirius appears, the enormous distances between stars are difficult to grasp. If Earth were only one mile from the sun, Sirius would still be 335,540 miles away. Even at a relatively short distance of 8.6 light years away, with current technology and human lifespans, traveling to Sirius is impossible.
• I’m ready for my close-up—Sirius is moving closer to our solar system. Traveling at 12,000 mph, it will reach its closest point in 60,000 years. Even then, it will only be slightly brighter and still very far away.
• White star has some seeing red—Sirius has been classified as a white star system for all of human history, yet in around AD 150, Ptolemy claimed Sirius was a red star. The only explanation astronomers can come with is that the smaller companion star orbiting the main star used to be a red giant, which would have caused the whole double star to appear reddish in ancient times.
• The guiding light—For the Polynesians in the southern hemisphere, the rising of Sirius marked the coming of winter, and it served as an important reference for their navigation around the Pacific Ocean.
• Hogwarts or Hogwash?—It is speculated that the character of Sirius in the Harry Potter series, who has the ability to transform into a black dog, may have been inspired by the smaller companion star of Sirius, “the puppy.”

Learn about the beliefs of the ancients and how much still holds true—or doesn’t—today during The Aegean Islands, Athens & Istanbul.