Understanding why the Earth has seasons is one of the most difficult concepts for people to understand because it is often difficult for people to abandon their preconceived ideas. Some widely held misconceptions are:
The Seasons are caused by the changing distance between Earth and the Sun.
The Earth’s axis changes the direction of its orientation throughout the year.
Granted, it is difficult to grasp the reasons for the cyclic changes of our seasons from our singular perspective on the Earth’s surface and these common misconceptions are supported by some reasonable evidence. Take for example the first misconception; the seasons are caused by the changing distance between the Earth and the Sun. For example, you may have noticed experiencing more heat energy from a source, like a campfire, as you get closer to the source and notice it less as you back further away. This is an occurrence which seems to support this popular misconception. The reality is that Earth gets only a little closer to or farther from the Sun during its orbit. When near a campfire, it’s easy to get twice as close without much movement at all. It’s largely an issue of scale and distance.
Earth orbits the Sun at an average distance of about 93,000,000 miles. One full orbit takes about 365 ¼ days. Earth is only – about 1.6% closer or 1.6% farther at its extremes throughout the year. That’s not much of a change. The reality is that this change makes very little difference in our temperatures. There is even a paradox. Earth is closest to the Sun on or about January 4th. Six months later when we are farthest from the sun, the date is near the 4th of July. Anyone who lives in Utah, or anywhere in the northern hemisphere, should recognize the paradox. The northern hemisphere is actually warmer when the Earth is farther from the Sun. This paradox shows us that the changing distance has little effect on Earth’s seasons.
As we will discover later, the seasons are caused by Earth’s tilt causing more ‘direct’ rays of the sun to strike the surface of the earth for a longer time in the summer and ‘indirect’ rays to strike the surface for less time in the winter.
In conclusion, we have dispelled the first myth about the seasons. We know that the seasons are not influenced by the slightly changing distance between Earth and Sun. Stay tuned to Clark Planetarium’s blog for part 2 of our seasons discussion were we will examine the second common misconception.