Every time yours truly experiences another summer solstice, sadness ensues as the days will now get shorter by about two minutes a day as we move toward the Winter Solstice on Dec 20th whereby the annual move toward the light begins yet again. Summer's this writer's favorite as light and warmth are the operative terms of the season though August gets rather sticky in this part of CT. The history of determining the solstice goes way back when a very intelligent guy named Eratosthenes discovered not only when the longest day of the year in the northern hemisphere of earth occurs but also calculated how big our plant truly is. Awesome says it all. :)
Can you feel the heat? If you find yourself north of the equator, astronomical summer kicks off today with the arrival of the summer solstice. In the southern hemisphere, the reverse is true, as today’s solstice marks the start of winter.
Thank our wacky seasons, and the 23.4 degree tilt of the Earth’s axis for the variation in insolation. Today, all along the Tropic of Cancer at latitude 23.4 degrees north, folks will experience what’s known as Lahiana Noon, as the Sun passes through the zenith directly overhead. Eratosthenes first noted this phenomena in 3rd century BC from an account in the town of Syene (modern day Aswan), 925 kilometers to the south of Alexandria, Egypt. The account mentioned how, at noon on the day of the solstice, the Sun shined straight down a local well, and cast no shadows. He went on to correctly deduce that the differing shadow angles between the two locales is due to the curvature of the Earth, and went on to calculate the curvature of the planet for good measure. Not a bad bit of reasoning, for an experiment that you can do today.
Yet another graphic showing our relation to Sol and the Summer Solstice.