dDaylight/dt

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).
Graph of the length of days
I used Juergen Giesen’s Daylight Applet to generate the numbers and graphed them in Excel.

Update 10/28/2006:
Juergen has since added a graphing function to his Daylight Applet. Do go take a look at it.
Thanks to Saheli Datta for adding a blue dimension to the topic.

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