Sun sets due west on equinox September 22
Photo: Joe Orman
September 22, 2008.
The September equinox falls today at 3:44 p.m. Universal Time.
That’s standard clock time at Greenwich, England. At the instant of this year’s September equinox, the noonday sun will be directly overhead at the equator as seen from northern Brazil.
Today, the sun leaves the northern half of the celestial sphere and enters the southern half. The sun is crossing the celestial equator. Much as birds and butterflies migrate south for the winter, so the sun can be found heading south on and around the September equinox. The lowering path of the sun is what makes this September equinox the northern hemisphere’s autumnal equinox. For the southern hemisphere, the September equinox signals the arrival of spring.
The sun rises and sets due east and sets due west around the world today. Daylight and nighttime hours are the same worldwide. But by this month’s end, the sun will rise and set noticeably south of due east and west. As the sun moves southward, the days will get longer in the southern hemisphere and the nights will get longer in the northern hemisphere. But today is one of two days in the year when both hemispheres have equal day and night.
