Photo top of post by EarthSky Facebook friend Graham Telford.
Here’s a natural phenomenon you might never have imagined. That is, the sun actually sets faster around the time of an equinox. The fastest sunsets (and sunrises) occur at or near the equinoxes. What’s more, the slowest sunsets (and sunrises) occur at or near the solstices. This is true whether you live in the Northern or Southern Hemisphere. And, by the way, when we say sunset here, we’re talking about the actual number of minutes it takes for the body of the sun to sink below the western horizon.
Why does the sun set so quickly around the equinoxes? At every equinox, the sun rises and sets due west. That means – on the day of an equinox – the sun hits the horizon at its steepest possible angle. In other words, the sun is dropping almost straight down from above. Meanwhile, at a solstice, the sun is setting farthest north or farthest south of due west. The farther the sun sets from due west along the horizon, the shallower the angle of the setting sun. That means a longer duration for sunset at the solstices.
Although the sunset duration varies by latitude, the equinox sun sets in about 2 and 3/4 minutes at 40 degrees latitude (Denver, Philadelphia).
Meanwhile, at 40 degrees latitude, the solstice sun sets in roughly 3 and 1/3 minutes.
via Year’s fastest sunsets happen around the equinoxes | Tonight | EarthSky.
