Sun worshipers rejoice! Here in the Northern Hemisphere, summer officially begins on Thursday, June 20 at 11:04 p.m. Mountain Daylight Time. This is the Summer Solstice, the date when the Sun rises at its most northeasterly point along the horizon, is highest in the sky at mid-day, and sets at its most northwesterly point. The word “solstice” means, “Sun standing still.” For a few days before and after the solstice, the location of the Sun along the horizon at sunrise and sunset will change very little, and daylight will last about 15 hours. By the end of the month, observers will begin noticing that the Sun sets a little farther south each evening, and rises a little farther south each morning. This will continue until the Sun rises and sets at its most southeasterly and southwesterly points on the winter solstice on December 21.
While the solstice is commonly called the longest day of the year, it is not the date of earliest sunrise or latest sunset. The earliest sunrise occurs about a week before the solstice and the latest sunset about a week after. This results from a combination of Earth’s changing speed as it orbits the Sun and the tilt of its axis.
As Earth orbits the Sun each year, the Summer Solstice marks the position of Earth where the Northern Hemisphere is leaning most in the direction of the Sun, and the Southern Hemisphere is leaning most away from the Sun. For inhabitants of the Southern Hemisphere this is the beginning of winter.
“Reason for the Seasons” will be the topic in Clark Planetarium’s Windows to the Universe show on Thursday June 20, so mark your calendars to attend.
Tags: Summer solstice