Sometimes I ponder things. Well, a lot of times I ponder things. Recently I was pondering the rate at which sunrise and sunset times are changing. My intuition told me that sunrise times must resemble a sine curve, slowing down to zero change at the solstices and reaching maximum change at the equinoxes. So I looked up a calendar that showed the sunrise/sunset times for every day of the year. Then I noticed something funny. The earliest sunrise does not fall on the summer solstice, nor does the latest sunset, yet the solstice is still the longest day of the year. The Winter solstice was similar. At this moment, I was tempted to go to wikipedia and read about this phenomenon, but I resisted. Instead I did my own mini-analysis. I took all of the New York City sunrise and sunset data for the year (from this site, which is pretty cool) and plugged it into Microsoft Office Excel 2007. I adjusted the times to ignore daylight savings time and repeated the year so you could see a nice curve. Then I made it into a chart:
The red line is sunset times, the blue line is sunrise times, and the green line is total hours of daylight. Notice that where the green line is lowest is after the earliest sunset and before the latest sunrise. This blew my mind – a little. Then I looked it up on wikipedia where it explained about the latitudes, the axial tilt of Earth, daily rotation of the earth, the planet’s movement in its annual elliptical orbit around the Sun, and the earth and moon’s paired revolutions around each other and . . . then I lost interest. But the graph is pretty cool, right? Right????