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Solstices and Equinoxes

The solstice is an event in the Earth’s orbit during which the tilt of the Earth’s axis is pointed most directly towards or away from the Sun. The summer solstice for the northern hemisphere occurs within a few days of June 21 every year. It is on this day that the position of the Sun in the sky at noon is at its highest altitude of the year, and the position of the Sun at Sunrise and Sunset is farthest north for the year. The winter solstice is around December 21, marking the date on which the Sun is lowest in the sky at noon and rises and sets farthest south. The day of the summer solstice is the longest day of the year, and the day of the winter solstice is the shortest day of the year. The equinox is the time of year when the Sun appears in the sky at the intersection of the ecliptic and the celestial equator. Two such points exist: The vernal equinox (approx. March 21) marks the start of spring. The autumnal equinox (approx. Sept. 20) marks the start of autumn. At each of these points, the Sun rises due east and sets due west.

Radio Programs

Summer Moon The evening sky on the first day of summer June 21, 2023

Moon and Spica Spinning through the zodiac May 30, 2023

Vernal Equinox Springing into a new season March 20, 2023

Winter Solstice Celebrating the darkness December 21, 2022

Paint Rock The Sun stabs the heart of the Sun December 20, 2022

Moon and Mars An old milestone and a new season July 20, 2022

Summer Solstice Heading into summer’s “oven” June 20, 2022

Vernal Equinox A new season and a new beginning March 20, 2022

September Equinox II Changes in the changing seasons September 23, 2021

Autumn Equinox Marking the start of a season September 22, 2021

Equinox Myth Cracking a myth about the equinox March 20, 2021

Vernal Equinox Calibrating the seasons March 19, 2021

Winter Solstice Lining up the start of winter December 21, 2020

Saturnalia A planet and a party share a name December 17, 2020

Autumn The Sun changes directions September 22, 2020

Winter Solstice The shortest day, but not the coldest December 20, 2019

Earliest Sunset Messing with the sunset December 3, 2019

Autumnal Equinox Stretching out the daylight September 22, 2019

Lahaina Noon The Sun stands high July 14, 2019

More Solstice Different dates for summer June 21, 2019

Summer Solstice Springing into summer June 20, 2019

Martian Spring Springing into a long season March 23, 2019

More Vernal Equinox The start of a cosmic journey March 20, 2019

Groundhog Day Celebrating Groundhog Day February 2, 2019

Summer Solstice Standing still for summer June 21, 2018

Winter Astronomy and the changing seasons December 20, 2017

Cahokia Aligning the rising Sun September 23, 2017

Autumn Ushering in the shorter days of autumn September 22, 2017

Summer Solstice Marking time by the motions of the Sun June 20, 2017

Vernal Equinox Springing into a new season March 19, 2017