Spring officially began this afternoon at 216pm Eastern time. Around here, at this so-called "vernal" equinox, there really wasn't anything special about the sun's position in the sky that would have caught your attention.

But at the North Pole, the sky on the vernal equinox is noteworthy. You see, for the last six months, the sun never rose above the horizon there. But today, the sun finally reappeared. And for the next six months, the sun will not set at the North Pole. It will move a little higher in the sky each day, reaching its maximum altitude, about 23 degrees above the horizon, on June 21, the first day of summer. It will then begin an equally slow descent in the sky so that by the first day of autumn, it will once again duck below the horizon, not to be seen for six more months.

At the South Pole, the situation is reversed. There, six months of darkness begins today.