The word equinox comes from two Latin words meaning equal and night. That’s because on the equinox, day and night last almost the same amount of time — though one may get a few extra minutes, depending on where you are on the planet.

Spring brings a dramatic change to Washington’s sky this year. The bright planets that have kept us company over the long winter nights are dropping out of sight, and winter’s bright constellations give way to the more subtle stars of the season.