Happy Vernality!

Today is the vernal equinox, what a lot of folks think of as the first day of spring (though given the forecast, people on the U.S. East Coast can be forgiven if they're rolling their eyes at that thought, assuming their eyeballs aren't frozen to their eyelids). There are many definitions of the vernal equinox; it's when the center of the Sun is directly over the Earth's equator, or it's when the Sun's coordinates on the sky (the celestial equivalent of latitude and longitude) are 0°, 0h. That ...