When you hear Dog Days of Summer the first thing that might have popped into your head is an image of dogs laying out in the summer sun. Although, it may imply that now – originally, it didn’t have anything to do with actual dogs.
The phrase Dog Days of Summer used by ancient Greeks to describe the phenomenon that occurs when the sun occupies the same region of the star Sirius. Sirius is also a part of the constellation Canis Major, the Greater Dog.
When Did They Start Using Dog Days?
The dog days started when Sirius appeared right before the sun rose. This was around late July. These days were known to be the hottest days of the year. Back then the Greeks and Romans believed that it was a bad omen – a period that could bring catastrophe.
Jay B. Holberg, the author of Sirius: Brightest Diamond int eh Night Sky said “If you go back even as far as Homer, The Iliad, it’s referring to Sirius as Orion’s dog rising, and it describes the star as being associated with war and disaster. All throughout Greek and Roman literature, you found these things.”
The phrase Dog Days has been translated from Latin to English. Over time, it has been redefined. Anne Cruzan, an English professor from the University of Michigan said “Now people come up with other explanations for why they’re called the ‘dog days’ of summer, this is when dogs can go crazy. This is a very human tendency”
Holberg says that though the meaning has been lost in translation, the phrase is still being used today. (Source: National Geographic)
Did The Greeks Get It Right?
Let’s circle back to the question, are dog days indeed the hottest days of the year?
Based on the origin of the term, dog days are 20 days before and 20 days after Sirius aligns with the sun. Roughly around the dates of July 3 to August 11. Although, these are generally the hottest months in the Northern Hemisphere, this can vary every year. The heat we feel during summer is a because of the Earth’s tilt. (Source: Farmers’ Almanac)
Bradley Schaefer, physics and astronomy professor from the Louisiana State University explains “Our Earth is like a spinning top. If you toss it onto a table, after it slows down the pointing direction of the top will slowly go around in circles. Similar to a top, the Earth’s rotation is kind of wobbling around.” He also added “In 26,000 years, the dog days would completely move all around the sky. Roughly 13,000 years from now, Sirius will be rising with the sun in mid-winter.”
Larry Ciupik, an astronomer from the Adler Planetarium also explained how stars shift. “The calendar is fixed according to certain events, but the stars have shifted according to the way that the Earth wobbles. In about 50-some years, the sky shifts about one degree.”
This simply means the dog days ancient Greeks experienced may not be the same we experience today. (Source: National Geographic)