Reasons for the Seasons

If you have been outside lately, you may have noticed a slight increase in sweaty people around you, and potentially an increased amount of personal perspiration. You may long for the chill of the lukewarm Decembers Mother Nature promises you as a Houstonian. I have found myself, on occasion, cursing the sun and its inexorable inferno. “Why, WHY can’t we all live in Southern California???”

 …But why curse the weather and your resulting ridiculous air conditioning bills when you can have WAY more fun trying to understand the heat source! The seasons, or the regular change of weather, happen because of the planet’s orientation to the sun. There is a common misconception that they occur because of the earth’s elliptical (like an oval) orbit, making it closer to and further from the center of our solar system at different times throughout our year. However, the ellipse that the earth follows is very nearly a circle, so this theory just doesn’t hold water.

GlowGlobe
Creative Commons License photo credit: etohaholic

 The real reason for the seasons is explained by the earth’s axis! Our planet is tilted at an angle of about 23.5 degrees with the perpendicular to Earth’s orbit around the sun. This means that the world is leaning slightly to one side at all times. Also, this would be a good time to note that this tilt stays the same throughout the orbit; it doesn’t swirl and swivel around as it moves along. So, the Northern Hemisphere leans slightly away from the sun in our winter, making the sun’s rays hit the earth at an oblique angle, which, in turn, makes its heat more diffuse over a large area, which equals cooler weather! The seasons are opposite in the Southern Hemisphere for the same reasons; when the North is tilted away from the sun, the South is tilted towards it, and vice versa. This alternating cycle of direct and obtuse solar rays effects other facets of life on earth; it is the reason for the changing lengths of days and the reason why some people get so sunburned in more tropical areas (which are closer to the equator, go figure.)

mars-06-crop
Creative Commons License photo credit: chipdatajeffb

 We all have first hand knowledge of what the seasons bring to the blue planet, but what about some of the others? Mercury rotates 3 times in 2 of its years and it has some of the most extreme temperature variations in the solar system, with a range of about -297 to 800 degrees F! On Mars, seasons change every 7 months and are much more severe than those on Earth. And although seasons on a gas giant don’t mean what they do on a terrestrial planet, on Jupiter, a change occurs only every seven years! Facts like these make me extremely glad to be an Earthling.

So, instead of pondering what to wear now that heather gray is out of the question, or heading out to buy new bead covers for your flesh-searing vinyl car seats, come to the Houston Museum of Natural Science and explore science in the cool, climate controlled heart of the Museum District.

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