Why Four Seasons

Yates Association

Why Four Seasons
Tom Rood

March 20, 2002

Spring is only a few short days away as this is written. Spring is one of the four major solar events which many of us mark as the passing of time. The earth is tilted on it axis as it rotates while travelling around the sun. We are actually a bit closer to the sun in winter than in summer but due to the tilt of the earth's axis, most of the extra winter's solar energy received in the northern hemisphere is deflected off into space. The more perpendicular any point on the earth's surface is to the sun the more the earth's surface is warmed in that area. Perpendicular is one of those twenty-five dollar words which in this case means straight up.

The four seasonal solar events mentioned above are of course Spring, Summer, Fall and Winter. These four events occur as milestones along the way of the sun's perpendicular mark upon the surface of the earth. There are technical terms for these events but the important thing is to understand the relationship of the sun and the earth's surface. The first days of Spring and Fall occur on the solar calendar when the sun is directly over the earth's equator. We all are watching daylight time increase along with the position of the sun on the horizon. It gives us the illusion that the sun is moving northward every day. Actually it is the tilt of the earth's axis travelling around in its orbit of the sun that causes the sun's position to appear to move.

The first days of Summer and Winter mark the extremes of the sun's perpendicular position on the earth's surface. Remember those dull geography lessons with the earth's globe setting on the corner of the classroom? Well, the globe does come in handy from time to time. The equator of course runs directly around the center of the globe. But those two other circles, one above and one below the equator, were identified by our geography teacher as the Topic of Cancer (northern hemisphere) and the Tropic of Capricorn (southern hemisphere). Capricorn and Cancer represent the sun's maximum northern and southern perpendicular movement upon the earth's surface. Interestingly, this imaginary line of the Tropic of Cancer passes just above the northern coastline of Cuba which is pretty far south of the finger lakes. There were a few days last summer when I thought the sun was directly overhead, at least it seemed that way as the sun's solar furnace tried to burn a hole in my t-shirt.

Our first day of Summer occurs when the sun is directly over the Tropic of Cancer. The early geographers didn't realize they were giving gardeners a warning to wear sun screen while working or playing out doors when they named this position on the globe. We are warm in the northern hemisphere because more of the sun's energy is absorbed by the earth's northern latitudes. We are closer to the perpendicular position over the earth's surface. In winter, the tilt of the earth on its axis causes much of the solar energy received in northern latitudes to be deflected off into space. The reverse of these events occurs in the southern hemisphere.

These solar dates on the calender are all three months apart and occur right around the 20th or 21st of March, June, September and December. There is what I call a fly wheel effect in the relationship to the effect of the sun's energy on the earth and these key solar events. For example, the shortest day of the year or the first day of Winter occurs December 21st. However the coldest day of winter doesn't normally occur until late January or ea