What the Ancient’s Say
Solstice comes from the Latin words for “sun stands still” a reference to when the star seems to be stationary in the sky for three days of the year before moving back in the opposite direction in both winter and summer.
‘The turn of the year’s tide; a pivot-point; the day when the dark stops rising & the sun begins its slow climb back. We need all the light we can get right now.’
Equinoxes and solstices are a result of two things: Earth’s tilt and its orbit around the Sun.
Earth spins on its axis of rotation an imaginary line running through the North and South Poles. The spinning Earth orbits the Sun once a year, tracing out an imaginary disk called the orbital plane or ecliptic plane.
Compared to its orbital plane, Earth’s axis of rotation is tilted by about 23.4 degrees. This is referred to as Earth’s axial tilt or obliquity.
Earth’s axial tilt remains the same throughout the year. The North Pole always points toward the star Polaris, while the South Pole points toward the much dimmer star Polaris Australis. However, as Earth travels along its orbit, its tilt changes with respect to the Sun.
For six months of the year, the North Pole is tilted toward the Sun, and the Sun lies somewhere above the Northern Hemisphere. For the other six months, the South Pole is tilted toward the Sun, and the Sun lies somewhere overhead the Southern Hemisphere.
The Solstices
The farthest points from the equator where the Sun can appear directly overhead are referred to as the tropics.
The tropics are that circle the Earth above and below the equator, at about 23.4 degrees north and south. This angle is set by Earth’s axial tilt.
There are two moments each year when one of Earth’s poles is tilted the most toward the Sun, and the Sun lies directly above one of the tropics. These moments are the solstices.
The June solstice takes place sometime between June 20 and 22, when the Sun is directly above the Tropic of Cancer in the Northern Hemisphere. As a rough guide, the Tropic of Cancer passes through Mexico, northern Africa, the Middle East, India, and China.
The December solstice happens sometime between December 20 and 23, when the Sun is directly over the Tropic of Capricorn in the Southern Hemisphere. In brief, the Tropic of Capricorn runs through South America, southern Africa, and Australia.
In the Northern Hemisphere, the June solstice and December solstice can be referred to as the summer solstice and winter solstice. In the Southern Hemisphere, June is winter and December is summer.
On the date of the summer solstice, all locations in that hemisphere experience their longest days and shortest nights. The winter solstice produces the shortest days and longest nights.