It's spring! Even if it doesn't feel like it. Today, March 20, is the vernal equinox, the official start of spring. (Or, in the southern hemisphere, autumn. Sorry.)
We celebrate two main sets of holidays pegged to the orientation of the Earth vis-à-vis the Sun—the “equinoxes” and the “solstices.” A few years ago the team at NASA's Earth Observatory used observations from a EUMETSAT meteorological satellite to make the video above, which shows what the solstices and equinoxes look like from space.
On the equinoxes, like the spring equinox today or the fall equinox in September, the length of the day and night are as close as they'll get. The northern hemisphere's summer solstice, in June, is the day with the most hours of sunlight. The winter solstice, in December, has the least daylight. All of it has to do with the fact that the Earth's rotation axis is tilted 23.5 degrees relative to the orbit we take as we circle the Sun.
For those inclined towards exploring Earth-Sun interactions, playing around with the University of Nebraska-Lincoln's Sun Simulator is a fun way to make a little more sense of the various factors that control how the Sun appears in the sky.
H/T Climate Central