As we noted two days ago, today is the Winter Solstice in the northern hemisphere. It’s one of two days per year when the tilted axis of the earth’s rotation is at its most extreme tilt with respect to the sun, Three months from now that axis will be at right angles to a solar ray, the north and south poles equidistant from the sun.
If that rotational axis were perpendicular to the plane of the earth’s orbit around the sun, there would be no seasons, no alternating periods of warm and cold weather on our globe. The poles would always be cold, the equator always hot, and the mid-latitudes always in-between.
Having concluded the astronomy lesson, welcome to winter.
