Then I was musing (totally off topic again)... what really makes spring come anyhow? What makes Spring spring? Why won't it get here already?!!! Some of you from Pennsylvania will tell me it has to do with a groundhog, and some who remember 6th grade reasonably well will say it has to do with our rotation around the sun. And there are those who might add Spring happens because the days get longer, allowing the sun to heat us up a little more. All of these are sort of correct (well, maybe not the Phil thing), but then again, not exactly. The Earth could rotate until it spun off its axis and it wouldn't change the temperature without one key ingredient. The days wouldn't get longer or shorter save for this ingredient either. And despite popular myth it is NOT correct that the seasons change because we are closer to the sun.
It is, of course, the tilt of the earth. The fact that we spin on our own axis cocked sideways in comparison to our orbit around the sun (the "orbital plane" in Scientific American speak) is what creates the seasons. Without that tilt, everyone would have a temperature and daylight very similar to everyone else, making room for differences in altitude and weather patterns. How crazy and random is that when you think about it? And think about what it would mean if we shifted our tilt? Talk about climate change, and melting polar icecaps! Some more food for thought, the tilt is changing! It varies every 41,000 years or so by about 2.5 degrees.
Okay, getting off track here in my thinking out loud. Here's a picture to illustrate from Wikipedia:
"The North Is Getting Shafted"
So, the orbital tilt.. exactly what does it change that causes these seasons? First, as is probably obvious, the tilt causes one side, either north or south, to have significantly less sunlight then the other side as we rotate daily along the equator. When it comes to the poles, we are talking TOTALLY less light. More light, means more sun baked radiation, which means more warmth (and more skin cancer). The other major contributing factor though is the obliquity of the sun to the spot you are standing. On the 'far side' (i.e. winter), the larger angle of obliquity (less directness) translates also into less radiation for the light we do get. That's why summer sun seems stronger than winter sun, and Florida sun seems hotter than Maine sun. Because it is. This is also why there is ice at the poles even in Summer. The sun is always oblique to a large degree at the poles.
Well, I'm glad I got that all cleared up :). I could go on about solar altitude and radiation lag.. but this is already nerdy enough, and way totally off topic again.
And really this is all to say, of course: Hurry up Earth, I'm sick to death of the dark side! Give it back to Australia and Argentina already.