Fires, Flux, and Wintertime

It is one of the more commonly known confusions in Science: The Earth is closest to the Sun in the wintertime (assuming you live in the northern hemisphere!) not when it is hottest. Of course, logic dictates that we can't be closer in the summertime because all the southern hemisphere folk are trudging through wintertime "down" there.

It turns out the proximity of Earth actually has nothing to do with the seasons. As you are taught in grade school, the perihelion and aphelion could occur anytime during the year and we wouldn't notice a difference - the reasons for the seasons is axial tilt. Most of us know this fact, but I'd wager most of us still picture it as a distance issue rather a tilt issue down in our guts. After all, if you are standing about 10 feet from a bonfire and take a few steps closer - you feel warmer. Take a few steps back and you cool off! We know this to be true by experience and we like to think of the Sun as a big fire in the sky. We know this simple fact to be true and so we keep coming back to it when thinking about heating up and cooling off.

(image from http://www.braintree.gov.uk/Braintree/default.htm)
I think one of the reasons for the persistence of science misconceptions in general is that we are not taught well. One must take the misconception head-on and run with it. Your science teacher should pursue this idea of getting closer to a fire: If the Earth -Sun distance was indeed 10 feet, then we could approximate the real change in distance during one orbital revolution by moving our face 2 inches closer to the bonfire. Not much of an effect, eh?

Now, watch the bonfire from 10 feet away and tilt you head back 23.5 degrees. Note the difference between your forehead (northern hemisphere wintertime) and your chin (southern hemisphere summertime). Your forehead is not cooler because it is further away, it is cooler because fewer rays of light are hitting your forehead now. This concept is called flux. Imagine putting your open hand in a waterfall, palm up. Now rotate your hand until only the edge of it is being struck by the waterfall. Your hand and the waterfall have not changed, but their relationship certainly has: you've gone from high flux to low flux.

(image from http://sol.sci.uop.edu/~jfalward/electricforcesfields/electricforcesfields.html)