Group 1 - The summer solstice occurs on June 21, marking the longest day of the year in the Northern Hemisphere, with daylight duration increasing as one moves north [1][4] - The term "summer solstice" refers to the moment when the sun reaches its northernmost point in the sky, directly overhead at the Tropic of Cancer, resulting in the shortest shadows at noon [4][10] - Despite the longest daylight duration, the latest sunset does not typically occur on the summer solstice due to the difference between true solar time and mean solar time, with the latest sunset usually happening in late June [7][10] Group 2 - The difference between true solar time and mean solar time is known as the equation of time, which varies throughout the year, ranging from -14 minutes to +16 minutes [7] - After the summer solstice, the ground continues to absorb more heat than it releases, leading to rising temperatures until the end of summer [10] - Ancient Chinese observed shadow lengths to determine seasonal changes, with the phenomenon of "no shadow" occurring at noon on the summer solstice for regions near the Tropic of Cancer [10]