What’s Up in the Sky – January, 2014
An Interesting Time of the Year
A Private Universe is a classic video documentary produced by the Harvard-Smithsonian Center for Astrophysics that examines the mystery of why the most basic scientific concepts are so widely misunderstood. I was reminded of the famous opening scene at Harvard graduation recently when I was visiting a highly regarded, first class local exhibition. In short, the wording on one of the descriptive placards led us to believe that it is summer in Australia at Christmas because the earth’s axis is tilted so that the southern hemisphere is closer to the sun than we in the north are.
I was astounded! This was not a ninth grade paper I was reading, but an explanatory placard of very high quality written by an obviously well-educated individual working for a prestigious institution. So, I wondered, why are the most basic scientific concepts so widely misunderstood? Therefore, here goes my contribution to the effort to reverse this trend.
Yes, Australia is a little closer to the Sun this time of year. But consider this: the entire earth is two million miles closer to the Sun than it is in July. That’s over 350 times the diameter of our entire planet so I can’t believe being in the south makes that much difference. If the campfire feels the same if you take two steps toward it, I’m sure your nose is as warm as your forehead.
So what does cause the seasons? Google does a splendid job on this so let me just suggest a wee demo: shine a flashlight straight down on the floor and notice the area lit up. Then change the angle of the flashlight and notice that the same amount of light is now spread over a larger area. So in the winter the same amount of heat from the Sun is spread over a larger area so the average temperature drops. Plus, winter days are short so the entire hemisphere receives less sunlight over a given day.
I was also recently asked this question: why don’t the earliest sunset and latest sunrise occur on the shortest day of the year? That one is beyond the scope of this column and requires extensive knowledge of what’s up in the sky.
This month in history:
Jan. 1: Isaac Azimov born – 1920
Jan. 13: Galileo discovers Ganymede, moon of Jupiter – 1610
Jan. 15: Samples of comet dust returned by Stardust spacecraft – 2006
Jan. 22: Apollo 5 launched = 1968
Jan. 27: Apollo 1 astronauts Chaffee, White and Grissom die in fire in capsule-1967
Jan. 28: Seven astronauts killed when Space Shuttle Challenger explodes during launch – 1986