On Wednesday (June 20), the sun will arrive at its northernmost point in the sky and herald a season change on Earth, with summer officially beginning in the Northern Hemisphere, while the winter season kicks off in the Southern Hemisphere.
(The seasons are caused by Earth’s tilt. In the Northern Hemisphere it is summer when the Northern Hemisphere is tilted towards the sun. CREDIT: Starry Night)
“The northern summer solstice will occur at 7:09 p.m. EDT (2309 GMT). Just as the word “armistice” is defined as a staying of the action of arms, “solstice” is a staying of the sun’s apparent motion over the latitudes of the Earth. At the summer solstice, the sun stops its northward motion and begins heading south. At the winter solstice, it turns north.”
(Contrary to widely held notions by smart people, the Northern Hemisphere is not warmer in summer than in winter because the Earth is closer to the sun in July than in January. Today the Sun reaches its northernmost point in the sky for the year, before beginning its long descent toward the south, all due to the 23.5 degree tilt of the Earth’s spin axis. -JCB)
Astronomy news, recent research results, and pretty pictures from the media along with context, commentary, and explanations for folks who dig this sort of thing. Written by a quasi-professional astronomer affiliated with the University of Texas at Austin.