Date: August 27, 2011
Title: Wonders from Class, Part 3
Podcaster: Diane Turnshek
Organization: Carnegie Mellon University
Description: Just the good bits of astronomy class, Part 3.
Bio: Diane Turnshek is an astronomer and a science fiction author with short fiction in Analog Magazine and elsewhere. She currently teaches classes in astronomy at the University of Pittsburgh, Carnegie Mellon University and St. Vincent College. Her day job is Outreach Coordinator for the Physics Department at Carnegie Mellon University, which includes running a monthly public lecture series in astronomy, traveling to Capitol Hill for congressional visits, advising the Astronomy Club and a StuCo (a student taught course), presenting at astronomy education conferences and answering questions from the public sector.
Sponsors: This episode of “365 days of Astronomy” is dedicated to Dr. Pamela Gay for her tireless efforts to make science education fun and astronomy an endeavor that everyone can share in.
Additional sponsorship for this episode of “365 days of Astronomy” has been provided by thesecretlair.com The Secret Lair is an online magazine and podcast dedicated to world domination and the plight of the grown-up geek. From an undisclosed location near Cleveland Ohio, Overlord Chris Miller, Dr. John Cmar, Commandant David Moore, and Secretary of Artistic Propaganda Natalie Metzger are joined by a stellar cast of contributors to share with you the trials, travails, and trivia of being a modern day working stiff with a strong escapist streak. There are lots of places covering pop culture on the Internet.
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Hi, there—back again? This is Diane Turnshek from Carnegie Mellon University. I’m here with Part 3 of “Wonders from Class: Demos.” I like to move outward in the Universe, starting with the sky as seen from Earth, showing the black and white Charles and Ray Eames film, “Powers of Ten.” As we approach the limits of the journey, we pause to reflect on the constituents of the entire universe. You have to love lines like, “This lonely scene, the galaxies like dust, is what most of space looks like.” And as we begin to move back in, my favorite line, “Notice the alternation between great activity and relative inactivity, a rhythm that will continue all the way in till our next goal, a proton in the nucleus of a carbon atom beneath the skin on the hand of the sleeping man at the picnic.”
Another good one with the same theme is the documentary Cosmic Voyage, narrated by Morgan Freeman. The scale of the universe is a hard thing to grasp. Over and over during the semester, I say, “Space is vast and there’s not a lot in it.” Lately, I’ve been using the glorious vision called “The Known Universe”—it’s the same trip from Earth, this time starting slowly above the Himalayas and moving outward with scientifically precise placement of known objects. This four dimensional map of the Universe was created by the folks at the American Museum of Natural History last year. It’s free to all to see on YouTube, with close to nine million viewers so far. Many teachers get the class to place balls of various sizes at the calculated distances of the planets. That’s always an eye opener, especially if you let the students guess first and find the actual sizes and distances later. Giving the students a sense of scale is one of my class goals.
A great way to get the class up and moving, depicting constellations, is to buy the components of throwies and have the class construct them. Throwies are urban graffiti; each one is made of a magnet, an LED, a lithium battery and a piece of tape to hold it all together. A handful of them, surreptitiously thrown against a metal structure, make a lit-up nighttime display. People toss them willy nilly and let them shine for a day or three wherever they land, but one could also place them in patterns. I have each working group construct a set of say twelve, and then urge them to go out and put them around the campus using the constellation patterns they’ve learned. Their favorites are the Big Dipper (I know, it’s an asterism, not a constellation), Orion and Leo. Of course, I make the students promise to not do anything dangerous like hang off a rooftop and they can’t leave the throwies up after the battery dies. That becomes litter.
Here’s a simple, obvious class activity. For the expansion of the universe demo, I pass out indelible markers and light-colored balloons. The instructions are to blow the balloon part way and hold it, draw dots to represent galaxies (dots, not big smudgy galaxies), at least ten of them, then continue to blowing it up, watching the way the galaxies separate. Try to convince yourself of three things. I write on the board. One, all the galaxies are moving away from all the other galaxies. Two, none of the galaxies is special in that. Mark a particular one and watch it, then mark a different one and watch that one. Blow the balloon up and down, up and down. Indeed, all the galaxies are moving away from all the other galaxies. And three, the farther away a galaxy is, the faster it’s moving. That’s Hubble’s Law. My projected PowerPoint slide has buttons sewn on a balloon, which is weird enough that the students comment. Anything that’s gravitationally bound, like a galaxy, isn’t getting significantly bigger with the expansion of the universe. The buttons are more correct than the student’s dots, which are expanding when the balloon is being blown up. FYI. I have never had a class where someone didn’t keep blowing up their balloon until it popped. Be ready. Don’t jump. Don’t scream. (Like, yeah, I always do.) If any balloons are left, you can have them draw a large triangle on the spherical surface, noticing that the three angles add up to greater than 180 degrees, as opposed to, with Euclidean geometry where the sum of the angles is precisely 180 degrees.
Over the years, every time I said something that elicited a laugh, I’d practiced saying it on the next class and then the next, working on my delivery like a stand-up comedian. What have I learned? Self-deprecating humor works well. Saying something unexpected, that’s fine, but be very careful not to use any kind of sexual innuendo. I don’t even say “naked-eye objects,” –oh, okay sometime I have said, “nude-eye objects” because I think it’s funny, but you have to be ridiculously careful. No matter how you pronounce Uranus (or Uranus) you’re going to get a titter, even in a college class. You may not think using puns in class would work, but try it. The students who are paying attention groan loudly and then the others tune in to see what they missed. For instance, when talking about the ancient Greek astronomers who didn’t understand retrograde motion, I define it: an apparent orbital zigzag or loop in the orbit of a planet father out from the Sun than Earth, just as the Earth passes it by on the inside track. Then I say that retrograde motion threw the ancient Greeks for a loop, because they didn’t appreciate that the Sun was actually at the center of the solar system.
And bad poetry—that works just as well. Here’s one I wrote for all those humans (the majority of them) who think cool water is somehow blue and the hottest fire is not white hot, but a dull red. Feel free to share it! It’s called—
“An Astronomer’s Dilemma”
The equations are easy, they follow the rule,
That blue stars are hot and red stars are cool,
My fingers are freezy, I feel like a fool,
The sink knobs are not, blue hot, red cool.
In my opinion, things that engage the students are good, and laughing and groaning is part of being engaged. When I demo conservation of angular momentum, I sit on a stool with no back, grab a couple of full water bottles and spin around with my arms and legs sticking out. When I tuck up tight, the stool flings me around so fast, I invariably fall off. I have their attention and the lesson proceeds. The most memorable demos, I’m told, are the ones where the teacher endangers themselves. I’ve ridden a rocket go kart down the hall, used blow torches, sprayed inky black dyes and lit books of smoking, flaming matches.
I won’t do the one with the bowling ball on the pendulum because I’ve heard of it being done badly. That’s the one where you stand a grad student flat against the wall. Position a bowling ball on a rope tied to a central ceiling beam. Pick it up just to his nose level and let it drop. It’ll swing out and then back again until it barely brushes his nose. The point is to calculate the changing potential and kinetic energy. But if you give it a little push as you’re letting go, a perfectly normal thing to do unconsciously, then it’s a bloody disaster.
There’s a demo of the elastic layers inside a Type II supernova—the outer shell explodes while the core implodes, creating the force necessary to produce a black hole. A supernova can be brighter than an entire galaxy of 100 billion stars when it first releases its energy. Look at the Type I supernova just discovered, PTF11kly is 21 million light years away in M101 and will possibly be visible in a pair of binoculars soon, since it’s brightening still. So, in my demo, I get a basketball and a tennis ball and position them in such a way that they’re just resting against each other when I drop them both. Individually, they are not very bouncy (which I demonstrate at the start), but together? As they hit the ground, the tennis ball zings across the room (and even knocked a student’s glasses off once). A supernova is one of the most energetic explosive events in the Universe. This demo shows the way energy can combine (because of the transitional layers inside the star) to fling matter out of a supernova at tremendous speeds.
Just one more for now, then I’ll continue this (again!) in a later podcast. The University of Pittsburgh has a fantasy guy in charge of demos for the Physics Department. At a ceremony for a staff award, he was introduced like this, “Do you want to know the formula for winning a Nobel Prize? You need only do two things. Tell Jim Stango that you want a magnetic monopole for your class. And rent a tux.” I love Jim. He has so many gadgets, I’ll never work through them all, but I try. For a visual demonstration of the center of gravity of a mass, he has an odd-shaped piece of foam. He’s poked it though with Christmas lights; the one at the very center of mass is the only red one. As it is thrown around the darkened room, student to student, the red light arcs in an obvious graceful curve, while the other ones jumble tumble around.
The students are back, the new semester begins Monday. I’m rolling out the cart with the celestial sphere on it, my meteorite collection, a lunar phase display and a telescope or two. Thanks for letting me share some of the excitement of teaching with you. Next time, I’ll talk about the labs we do in our fifteen week term. This is Diane Turnshek for 365 Days of Astronomy, signing off.
“The Known Universe”
End of podcast:
365 Days of Astronomy
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