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

Spring Equinox Projecting the spring equinox Thursday, March 20, 2014
Winter Solstice Drawing up the winter solstice Saturday, December 21, 2013
Spring Springing into a new season Tuesday, March 19, 2013
Summer Solstice Lining up the summer solstice Wednesday, June 20, 2012
Sun Tower A moment of sunlight without shadows Tuesday, June 19, 2012
Spring Equinox A new season and a new beginning Monday, March 19, 2012
December Solstice A pale light in the daytime sky Wednesday, December 21, 2011
Summer Solstice Hot times in northern climes Tuesday, June 21, 2011
Spring Equinoxes The start of spring on two worlds Sunday, March 20, 2011
Winter Solstice Marking the start -- or middle -- of winter Tuesday, December 21, 2010
Moon and Aldebaran Lining up a lot of moonlight Sunday, December 19, 2010
Autumnal Equinox II Tilting toward a new season Tuesday, September 22, 2009
More Moon, Regulus, and Saturn A leading light with a leading role Friday, June 26, 2009
Summer Solstice The Sun comes to a standstill Sunday, June 21, 2009

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