DAYLIGHT IS DECREASING--

Now that we have passed the Summer Solstice our days are getting shorter. Why?

The sun's latitude changes. That’s why.

The sun lights about half of the planet at any moment. As the Earth turns, we enter the lit area, experience a day, and then leave the lit area. When the sun is toward the south, our path through the lit zone has a shorter length. When the sun is toward the north, the lit path has a longer length.

Accordingly, at the Summer Solstice when the sun is highest in our sky our days are longest. Then, the sun starts to head back south and our days begin to shorten. On the Winter Solstice, the sun is farthest south and our days are shortest.

Maybe it is easiest to understand this way: Remember extreme effects occur at the North and South Poles. When the sun is farthest north (our summer) there are 24 hours of daylight at Santa’s house. The opposite occurs in our winter—there are 24 hours of darkness up there.

Consequently, the length of our days change as the sun is making this annual migration back and forth. There, it’s just that simple.

Editor’s note: For those of you with greater scientific curiosity you realize, of course, there are many other things involved: the Earth is tipped 23.5 degrees, it wobbles and precesses in its elliptical orbit, and it takes us 365¼ days to orbit the sun, a fractional inconvenience that imposes the concept of leap year.

You may even note the omission of sidereal and synodic days or the plane of the ecliptic from this discussion, or, mention of how an analemma explains the variation in the rate of change of the length of our days.

While these are very interesting topics to explore, the inclusion of too many facts can sometimes get in the way of comfortable understanding. I chose to present this topic with any error of omission being in favor of both brevity and clarity.