For those of us who approach things by the Goldilocks Principle (not too little, not too much), spring equinox is practically perfect. Along with the fall equinox, this is when we get that glorious balance of daytime and nighttime all over the world — from the steamy equator to the frigid poles — with just about 12 hours of each.

Spring is almost here — officially, at least. The vernal equinox arrives on Thursday, marking the start of the spring season for the Northern Hemisphere and the fall in the Southern Hemisphere. On the equator,

The vernal equinox arrives on Thursday, marking the start of the spring season for the Northern Hemisphere and the fall in the Southern Hemisphere. On the equator, the sun will be directly overhead at noon. Equinoxes are the only time when both the north and south poles are lit by sunshine at the same time.