Equinox marks end of summer season
September 19, 2013
As the school year begins and gets into full swing, it also, sadly, means that summer is drawing to a close. Many students perceive the start of school to be the end of summer, which is true in a sense, though astronomically, we are currently in the last week of summer.
This weekend marks the second equinox of the calendar year or the scientific term, autumnal equinox. This means that there are 12 hours of sunlight and 12 hours of darkness and there is gradually less light each day leading up to the winter solstice in December, the shortest day of the year.
The equinox officially marks the beginning of autumn, which also means it is time for cider, changing colors and various autumn holidays.
During the equinox, the plane of the Earth’s equator passes through the center of the sun. This is due to the fact that the Earth’s axis is not tilted away or toward the sun. The term autumnal equinox is derived from Latin. “Aequus” means equal and “nox” means night, making the equal amount of daylight and darkness evident. “Autumnus” means autumn, marking the time of year.
The term equinox is not always accurate, however. One reason is because the sun’s size is so large. The top of the disk rises above the horizon while the center of the disk is still below the horizon. This means that people perceive the start of daylight differently. Some see it when the sun rises, while others see it as when they first see light in the morning sky, because the earth refracts sunlight before the sun has even risen.
The exact date where there is in fact equal daylight and darkness varies from location to location.
The equinox is the only time of year to see many different astronomical events. This is the only time of year that the subsolar point, the place on the Earth’s surface where the center of the sun is exactly overhead, is on the Equator. It is also the time of year when the International Date Line, is exactly perpendicular to the equator.
This means that both the northern and southern hemispheres are illuminated equally by the sun instead of one pole having 24 hours of daylight and the other with 24 hours of darkness.
Earth is not the only planet that experiences equinoxes. In fact, all other planets in our solar system also have their own equinoxes.
The most dramatic equinox in the solar system is Saturn’s equinox, because it places the ring system edge-on facing the sun. As a result of this phenomenon, the picture seen from Earth is only a thin line.
The planet receives very little sunlight. This lack of sunlight occurs every 14.7 years and lasts several weeks before and after the equinox. The next equinox is expected to occur on April 30, 2024.
Even though the days are getting shorter and the weather will soon be getting colder, autumn is a perfect time of year to enjoy your surroundings. Whether you are smelling the crisp autumn air or witnessing the vivid colors all around, there is always something to celebrate during the season.
Cristin Dempsey is an English major and music minor from Eagan, Minn. She enjoys writing, playing the flute and swimming. After college she would like to pursue a career as an editor.