Thursday is the first day of spring, or the vernal equinox, in the Northern Hemisphere. During an equinox, the center of the sun is on the same plane as the equator. After the vernal equinox in March, the Northern Hemisphere tilts toward the sun until the June solstice, when the sun begins to migrate back south.

The vernal equinox marks the start of spring in the Northern Hemisphere — so does that mean this is the only day out of the year when you’ll be able to balance an egg? Or not see your own shadow?