Physical science mini-lesson for the week

Physical Science: Perihelion

Every one of my classes gets a lesson (or two or three) on seasons--I think grasping seasons should be a requirement to get a driver's license. (No, it won't make kids better drivers, but my students study everything in the New Jersey driver manual.)

A few days ago I came a close to the sun as I will this year. The Earth is getting hit with more solar energy this week than it will all year (well, barring some end-of-our-world series of X-class solar flare--how cool would that be?)

By July, the Earth will be just a bit over 3 million miles farther from us than it is today. (In elementary school, I was taught over and over that the sun is 93 million miles away, and sometimes it is. Sometimes, though, it's 91 million miles away, and sometimes 95 million.) The Earth's orbit is slightly elliptical.

Now in AP physics you can have all kinds of fun with elliptical orbits and Kepler's law and how fast the planet is "flying" through its orbit. (Astronomical winter is shorter here than in Australia, praise the Lord.) You can talk about albedo and incidence of light and seasons and have a ball figuring out why it happens to average low daily temperature is -4C here in January.

I teach physics "lite", but I will not teach physics "fake". The math for physics can be daunting, but many of the concepts can be worked qualitatively, generating good discussion.

I teach about the seasons, walking around the room carrying a globe, circling one of my wackadoodle's hooded heads assigned to be the sun. (Works even better when I remember to bring a light). I try to place their eyes into the head of an imaginary person stuck onto the globe. (I really need to get some tiny plastic man and set up various velcro'ed spots to stick him.)


Try to act out the angles--spinning yourself at a 23 1/2 degree angle is amusing, if nothing else, but you know some of them get it when they go aha! and grasp that the sun "spins" around, not up and down, the summer Antarctic sky.

Casually mention that the Earth is doing a slow drive-by this time of year and ask how come it's still cold outside. Walk aroung the room again, this time in an exagerrated elliptical orbit.


And if even just one of your wackadoodles starts holding up his palms in various angles to the light, sputtering that light that skips off the Earth (or some other kinesthetic version of trigonometry) doesn't warm it up as well as light that hits it smack on--well, you know at least one got it.