These days are known as the dog days of summer. Many believe the ancient saying is an idiom about dogs panting in high heat . But it is in fact about a set time during the summer between July 3 and August 11. It is tied to an annual astronomical event. This is when Sirius, the bright Dog Star in the constellation Canis Major, appears to rise and set with the sun. Ancient peoples falsely believed that the merger of the two stars in summer caused the high heat. Homer referred to Sirius as an “evil portent” in the Iliad. He described it as "bringing heat and fevers to suffering humanity.” The Romans made sacrifices of dogs and other animals to the gods in response. They believed Sirius and the sun caused summer plagues and crop failures. The reason why it's hottest during the dog days is because of the tilt of the Earth and the length of day. From early July through August the sun hangs high in the sky longer. That heats the planet’s surface in the Northern Hemisphere. Also, the land and sea begin to absorb peak solar energy at the summer solstice (June 20-21). That causes temps to rise in the weeks that follow. A number of studies have shown that the hottest stretch of summer has grown longer in the past fifty years. In some cities, it has lengthened by as much as 14-20 days. And many experts blame human-driven climate change. While it does not change the position of the Earth and the sun, burning fossil fuels releases gases into the atmosphere. Experts say those gases trap Earth's heat. As Shakespeare once suggested, "the fault is not in our stars, but in ourselves." Reflect: How do you notice the seasons changing where you live? Photo of the location of Canis Major from NASA.
