The Start of Summer - The Solstice

June 20, 2014 Posted by: Ranger Tim

As each day comes to a close we will start losing a little more daylight after June 21, 2014 (this year June 20) the official first day of summer and the longest day of the calendar year. The word "solstice" is derived from the Latin words sol (sun) and sistere (to stand still) – therefore solstice means "sun standing."

The summer solstice occurs as the sun reaches its most northern point in the sky at local noon. After this date, the days start getting "shorter," i.e., the length of daylight starts to decrease. Summer solstice occurs when the tilt of a planet's semi-axis, in either the northern or the southern hemisphere, is most inclined toward the sun that it orbits. This occurrence happens twice a year, in which the sun reaches its highest position and lowest position in the sky as seen from the north or the south poles. The summer solstice occurs during a hemisphere's summer. In our part of the country this is referred to as the northern solstice.

What is the solstice exactly? The solstice has to do with imaginary lines on our planet. These lines are important because they help people navigate and measure time. Let's look at the equator for instance.  The equator is an imaginary line drawn around the Earth's middle, like a belt. It divides Earth into two hemispheres – northern and southern.  Another imaginary line drawn straight through Earth connecting the North Pole to the South Pole is the Earth's axis of rotation. The line is tilted 23.5° degrees from Earth's path around the sun. The tilt is the cause of Earth's seasons.

Other useful, but imaginary, lines around the Earth are parallel to the equator called lines of latitude. These lines are numbered 0° to 90° degrees. The line at 0 degrees is the equator itself. The higher the number, the farther north (a "+" number) or south (a "–" number).

Have you ever look closely at a map of the world? You may have noticed two special lines of latitude on a globe: One in the Northern Hemisphere called the Tropic of Cancer at +23.5° latitude. This is the northernmost point on the planet.  The other latitude in the Southern Hemisphere is called the Tropic of Capricorn at − 23.5° latitude; it is the southernmost point on the planet.

The Tropics of Cancer and Capricorn are the latitudes where the Sun is directly overhead at noon once a year – or when the sun's rays reach the northernmost or southernmost point of the planet. The summer solstice usually occurs on June 21.  This means that on or about June 21, the earth's axis of rotation points most toward the sun and receives the most hours of sunlight. On or about December 21 the earth's axis of rotation points most away from the sun creating the winter solstice and receives the fewest hours of sunlight.

Did you know?!? What most people in the Northern Hemisphere probably associate with solstices is that the summer solstice is the day of the year with the most daylight and the winter solstice is the day each year with the least daylight; the opposite is the case for those living in the Southern Hemisphere.

Last updated: April 14, 2015

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