The FireTtriangle. Most people have heard of the fire triangle: heat, fuel, and oxidizer. When these three components come together in the proper proportions, a fireâthe rapid chemical reaction of fuel with oxygen, resulting in the release of heat and light energyâis bound to occur.
Answer by Hank W. The average length of the northern hemisphere summer, calculated as the average time from the June solstice until the September equinox, is about 93 days and 15Â½ hours. The average length of the southern hemisphere summer, calculated as the average time from the December solstice until the March equinox, is about 89 days.
This year, the last day of summer is Sept. 22. Photo: GETTY IMAGES. Labor Day marks the ceremonial end of summer, but there are still a good few weeks to enjoy the season, even after the three-day weekend ends and schools begin their calendar year. This year, the last day of summer is officially on Sept. 22. The fall equinox arrives Sept. 23 and so does the onset of shorter days in the Northern Hemisphere. Equinox is derived from the Latin words aequus, which means equal, and nox, the word for night.