Hello! It is indisputably spring! Congratulations! Yesterday at 7:21 PM Eastern Time, the Sun crossed the equator, marking the vernal equinox in the Northern Hemisphere. In the Southern Hemisphere, of course, this was the autumnal equinox. “Vernal” and “autumnal” mean spring and fall, respectively, and “equinox” is Latin for equal night.
For the next six months, the north pole will be tilted toward the Sun, making for longer days. Because of math, day-length changes most quickly around the equinoxes and slows down as it reaches its maximum or minimum on the solstices. Here’s a chart showing the hours of sunlight for every day of 2006 in Philadelphia:
Some cultures think of the equinox as the middle of spring, and some think of it as the beginning. Astronomically-speaking, it’s the middle because it’s the halfway point between the shortest and longest days. But weather-wise, it feels more like the beginning because the change of temperature lags behind the actual amount sunlight. The hemisphere takes a little time to warm up.
Also, the vernal equinox happens to be my birthday, so that’s always nice.