Astronomy is one of my hobbies and I enjoy celebrating celestial events. For me, it’s a great way to keep my life in perspective and to continually renew my sense of wonder about life and our minuscule part that we play in the universe. I also find it incredible that humans have have used celestial events to measure the seasons for thousands of years – most of them doing this strictly by observation, without knowledge of fundamental traits such as the heliocentricity of our solar system.
Today marks a celestial phenomenon that happens twice each year: the equinox. The equinox is a way to mark the changing of the seasons, in the case of today’s equinox it’s the end of summer and the beginning of fall for the northern hemisphere as well as the start of spring for the Southern Hemisphere.
The reason for the name “equinox” has to do with the geographical position (GP) of the sun. The suns GP is the location on Earth where the sun is directly overhead. This position changes in latitude throughout the year, moving from its highest latitude at the Tropic of Cancer to its lowest latitude at the Tropic of Capricorn. On the equinox, the GP of the sun is directly over Earth’s equator. The length of daytime and nighttime are approximately equal on this day.
I suppose this is all a very circuitous way of saying “happy first day of fall!”