TODAY: LONGEST DAY OF THE YEAR
Summer Solstice 2018

Today – June 21st – will be the longest day of the year for 2018. This day is called the Summer Solstice.

The summer solstice occurs when the sun is directly over the Tropic of Cancer or 23.5° north latitude. This will be the longest day of the year for anyone living north of the equator.

The summer solstice marks the day when the Sun appears to reach its highest point in the sky.

Two solstices occur annually on or around June 21 and December 21.

The word solstice comes from the Latin sol (“sun”) and sistere (“to stand still”). Astronomers from centuries past observed the Sun’s declination appears to ‘stand still’ on this day each year. They followed the seasonal movement of the Sun’s daily path closely with stops (‘Solstice’) at a northern or southern limit before reversing direction.

The sun’s angle relative to Earth’s equator changes so gradually close to the solstices that, without instruments, the shift is difficult to perceive for about 10 days. This is the origin of the word solstice, which means “solar standstill.”

This slow shift means that June 21 is only about 1 second longer than June 20 at mid-northern latitudes. It will be about a week before there’s more than a minute change to the calculated amount of daylight. Even that’s an approximation – Earth’s atmosphere bends light over the horizon by different amounts depending on weather, which can introduce changes of more than a minute to sunrise and sunset times.

Monuments at Stonehenge in England, Karnak in Egypt, and Chankillo in Peru reveal that people around the world have taken note of the sun’s northern and southern travels for more than 5,000 years. From Stonehenge’s circle of standing stones, the sun will rise directly over an ancient avenue leading away to the northeast on the solstice. We know little about the people who built Stonehenge, or why they went to such great effort to construct it – moving multi-ton stones from rock outcrops as far as 140 miles away. All this to mark the spot on the horizon where the sun returns each year to rest for a while before moving south again. Perhaps they, like us, celebrated this signal of the coming change of seasons.

To learn more about the solstice, see Stephen Schneider, Professor of Astronomy, University of Massachusetts Amherst and Space.com.

TODAY: Longest Day Of The Year - Summer Solstice 2018

TODAY: LONGEST DAY OF THE YEAR

Sunrise imaged by Taro Taylor
Stonehedge image by Mr. Chang
Solstice Daylight graphic by Brian Brettschneider

Staff Writers

The staff writers at Cullman Today are a collaborative group of citizen reporters sharing the writing of stories based upon their personal interests and work schedules.

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