MemeMachineGo!

The first derivative of daylight over time, or why the autumnal equinox gives me the blues.

The Autumnal equinox is in a couple of weeks, and during this time the days are getting shorter at the fastest rate they will all year, with the biggest change right on the day of the equinox. This graph is intended to compare the rate of change of the number of hours of daylight at two times during the year. At the Summer Solstice, light blue, there are a few days when the length of the daylight changes very little. But at the Autumnal Equinox, shown in dark green, the slope is very steep, showing that the amount of sunlight we get in a day is falling quickly. This has great implications for anyone with SAD (Seasonal Affective Disorder).