By John Copeland
As months go, July is a bit unusual. Most of the other months of the year are named for either gods, goddesses, festivals or numbers. July is one of two months named for real people. In the case of July, the person is Gaius Julius Caesar. August is the other one, which honors Julius Caesar’s great nephew, Gaius Octavius, better known to history as Caesar Augustus and the first Roman emperor.
All the months of our calendar were handed down to us by the Romans. July was originally the fifth month of the Roman calendar and called Quintilis, which is Latin for “fifth.”Over the years, the Roman calendar had become hopelessly confused. It was very cumbersome and full of inaccuracies, and had, over time, allowed the months to drift across the seasons. In Caesar’s day, January was in the autumn. In 46 BCE, he initiated an overhaul of the calendar that established a new dating system, the Julian calendar.
This calendar was more closely synced to the year’s seasons and closely resembles the Gregorian calendar we use today.
After Caesar’s assassination in 44 BCE, the Roman Senate renamed the month Quintilis to Julius. Caesar had been born during the month of Quintilis, so for the Senate it was the natural choice for honoring him. So much for how the month of July got its name.
July is also when the dog days of summer begin. The phrase “dog days of summer” conjures up images of the hottest, most sultry days of the season. Today, many people believe the dog days are a reference to the conspicuous laziness of domesticated dogs and humans “dogging” around, or being “dog tired” during the hottest days of the summer. Like so many references in our language, the underlying meaning of this common phrase has become somewhat obscure in our culture. The origin of “dog days” is more involved and interesting than many realize, so here’s a little reminder.
The Romans called the dog days, in Latin, “diēs caniculārēs.” According to John Brady’s history of our calendar, “Clavis Calendarium,” printed in 1813, the Romans believed it to be an evil time “when the seas boiled, wine turned sour, dogs grew mad, and all creatures became languid, causing to man burning fevers, hysterics, and phrensies (frenzies).”
In reality, the dog days actually referred to when the star Sirius was brightest in our skies. During this time, Sirius rises and sets with the sun. If you get up early in the morning during July to early August, go outside and watch the sunrise, you will see both the sun and Sirius climbing into the sky. The ancient Greeks and Romans, also called Sirius the “Dog Star” because it is the brightest star in the constellation Canis Major (Big Dog). Sirius was thought to be responsible for summer’s hot days — the name is actually derived from the Ancient Greek word “seirios,” meaning “scorching”. That’s obviously not the case at all — it’s far too distant to have any effect, but it demonstrates how important in human history the sky has been.
Our summer heat is not caused by the added radiation from far-away Sirius, regardless of its brightness. Warm summer weather is a direct result of Earth’s tilt on its axis. During the summer months, the position of the Northern Hemisphere allows the rays of sunlight strike it more directly. Because Earth’s oceans heat up and cool down slowly, it takes time for the summer sunlight to have a warming effect. In July, the oceans are still cool from the winter and that delays peak summer heat by about a month and a half.
In ancient Egypt, the Nile River flooded each year, usually beginning in late June. The people welcomed this event, called the Inundation, because the floodwaters brought rich soil needed to grow crops in what was otherwise a desert.
No one in Egypt knew exactly when the flooding would start, but they noticed a coincidence that gave them a clue: The water began to rise on the days when Sirius began to rise before the Sun. The ancient Egyptians called Sirius “sothis” and the Inundation became so important to the Egyptians’ survival that they began their new year with the new Moon that followed the star’s first appearance on the eastern horizon.
Today, the Dog Star rises later than it did in ancient times. Its ascension no longer coincides with the start of the Nile flood, which no longer occurs, because the river is now controlled by the Aswan Dam. The change is due to the very slow wobble of Earth’s axis the stars in our night sky shift independently of our calendar seasons. The shift is about 1 degree every 50 years. The term for this is the precession of the equinoxes. The constellations we see in the night sky, today, have moved roughly 41 degrees from their positions in the sky in ancient times. Sirius still makes its appearance during hot summer days. Today the dog days of ancient Rome are not the dog days for us. Roughly 13,000 years from now, the conjunction of Sirius and the sun will not even occur during the summer. Sirius will be rising with the sun in mid-winter. Then, we may be referring to the dog days of winter. But for now, most of us see the dog days as the start to our vacations.