Some elements of definition
You may know the meaning of the word heatwave, but do you know the history of the word heatwave? According to the common definition, it is a word used to refer to a period of high heat that lasts for several days and nights in summer (the standard minimum duration is 3 consecutive days).
It should be noted that the temperature thresholds defining a heatwave vary from one French city to another (this also applies between countries, since a heatwave is not defined according to the same criteria in Norway or Niger). Thus, if we take the example of Paris, we will speak of a heat wave if it is at least 31 degrees Celsius during the day and 21 at night. In Marseille, it will be 36 during the day and 24 at night.
And now, did you know that there is a close link between the word heatwave and the planet Sirius, which, as seen from Earth, is the brightest star after the sun? Amazing, isn’t it? To understand this link and thus the history of the word “canicule”, we will have to go back in time…
A little history
More than 3000 years ago, the ancient Egyptians (the civilisation of ancient Egypt took shape around 3150 BC and officially ended in 30 BC, when it was conquered by the Roman Empire and became a Roman province) noticed an extraordinary link between the earth and the sky: at dawn on the 19th of July each year, as the waters of the Nile rose, a star appeared in the sky at the same time as the sun.
Like their Mesopotamian predecessors (a civilisation located in the Middle East, between the Tigris and the Euphrates, corresponding to present-day Iraq and Syria. It appeared around the 10th millennium BC and died out during the first millennium BC), the Egyptian astrologers looked for relationships between what surrounded them in their daily lives and the celestial vault, because they believed in the idea that the heavens gave meaning to their world. The ordering of the sky and the stars allowed them to interpret and understand the world in which they lived.
The history of the word “canicule” is the result of a strange coincidence…
And so, for a month, this star appeared and disappeared with the sun, which was symbolised by the divinity Ra, during the same month when the Nile floods fertilised the arid lands, a phenomenon that allowed them to establish a surplus of agriculture, the indispensable basis for the development of civilisation.
This star then disappeared for a year from 23 August, at the same time as the waters of the Nile receded. This disturbing simultaneity explains why Egyptian astronomers established a calendar beginning on July 19, the exact date of the rising of the waters and the appearance of this star, which was personified by the goddess Sopdet.
A few centuries later, this star, visible in the hottest month of the year, was observed by the Greeks, who first called it Sothis, before finally calling it Sirius (which in Greek means fiery).
Fast forward a few more centuries and it was the Romans’ turn to observe this star. They decided to attach this bright star to the constellation of the Great Dog and named it ‘the little bitch’, which in Latin means ‘canicula‘. And so it is this term that has come to designate this period of extreme heat that is the heatwave.
So now you know the history of the word heatwave.
Nowadays, the sunrise of Sirius takes place in August (in astronomy, the heliacal rise of a star is the moment when this star becomes visible in the east, above the Earth’s horizon at dawn, after a period when it was hidden below the horizon, or was located just above the horizon but drowned out by the brightness of the Sun).
The Big Dog constellation, with Sirius clearly visible. Sirius is the sixth closest star to our solar system.
The constellation of the Great Dog may not be very large, but it contains a large number of visible stars, and several of them have proper names: Murzim (β CMa), Muliphen (γ CMa), Wezen (δ CMa), Adhara (ε CMa), Furud (ζ CMa), Aludra (η CMa) (Source: Wikipedia)
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