Date: August 18, 2011

Title: Wonders from Class Part 1

Podcaster: Diane Turnshek

Organization: Carnegie Mellon University


Description: Just the good bits of astronomy class, Part I.

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.

Diane Turnshek teaches astronomy at CMU, Pitt and St. Vincent, and coordinates the physics outreach at CMU. St. Vincent’s planetarium boasts a state-of-the-art Spitz SciDome projector. Diane worked as a planetarium operator at the Carnegie Science Center’s Buhl Planetarium, assisting in the production of shows. In her astronomy outreach efforts, she has visited to schools, libraries, camps, Scouts and Congress. She hosts a monthly public lecture series at Allegheny Observatory. She has consulted with many who wished to keep their science accurate, from authors to opera companies. She is a science fiction author and editor, whose short fiction has been published in Analog Magazine and elsewhere.

Sponsor: The Department of Physics at Carnegie Mellon University in Pittsburgh, PA is proud to sponsor 365 Days of Astronomy and its efforts to bring the world together in appreciation of our sky.


Hi, this is Diane Turnshek and welcome to 365 Days of Astronomy. Let me give you a peek into my world of teaching introductory astronomy. I’m trying to build a cadre of educated voters. I feel the need to teach that the Universe is knowable, have the students understand the degrees of uncertainty in science and instill in them the importance of the scientific method. I try very hard to make the class fun. We read astronomy current events articles and discuss the science in movies in an effort to hone their critical thinking (with appropriate skepticism).

Here’s a quote from an article by Bruce Partridge and George Greenstein in the Astronomy Education Review published on October 13, 2003:

“Roughly 10% of all U.S. college students take an introductory astronomy course while in college. The vast majority of these students are not science majors, and this course often represents the only college-level science these undergraduates will ever encounter.”

Underneath all the fun we have, I do appreciate the seriousness of the task.

On the first day of class, I like to introduce the students to some mind-boggling concepts of the Universe, while maintaining their connection to it. I show a range of pretty pictures and play spacey intro music as they find their seats.

Have you heard of It’s a website that takes data in the form of word lists and makes word pictures. I ask the students to write down three separate words describing what they’re eager to learn this semester and three more words that mark some things they’re not so keen to learn about. They pass the papers forward and front row students volunteer to enter them into files—the data is entered online at The more times a word is repeated in the list, the bigger the word’s font in the colorful, artistic display. Soon, we have word clouds displayed for all to see. My classes are mostly arts students. Invariably, they say they want black holes, constellations and stars and are afraid of learning anything that has to do with math, black holes and galaxies. This visual pleases them, but to me, it shows a profound lack of understanding of what the study of astronomy actually is. We repeat this exercise at the end of the semester (three words indicating astronomy topics that interested them and three subjects that we covered that didn’t really interest them) with markedly different results, which is validating to me as well as the students.

The first day, we talk about light travel time and then marvel at what that means. The further out into the Universe you look, the further back in time you’re seeing. You’ve all heard, “We see the Sun as it was eight minutes ago, the nearest star as it was 4.3 years ago, Orion Nebula as it was 1500 years ago, Andromeda Galaxy as it was over two million years ago.” Astronomers study the history of the Universe with large telescopes. Beat that, Chemistry, Math and Biology! Imagine what that would be like if light travel time was slower? What if we could see our Sun and the planets forming? The evolution of life on Earth unfolding through our telescopes? Instead, taking light travel time into account, we’re seeing young misshapen galaxies from the early universe, which are very different from the mature galaxies around us today.”

I ask the class, “Does anyone have any gold on them? Silver?” I hold up my platinum ring. “In the beginning of the Universe, a few light elements were formed (helium, deuterium, some lithium), then more elements formed in the centers of stars, but those metals you’re pointing to? The only place metals heavier than iron can form in the whole Universe is in the centers of supernova explosions, explosions so big and so bright that the light from them rivals the light from a whole galaxy of hundreds of billions of stars. That means the atoms in your ring, earrings, necklace were once in a supernova, and then traveled through space until they joined the gas cloud that formed the planet Earth. Billions of years later, veins of precious metal were dug up and the metal formed into your ring. You own atoms that were made in a dying star.”

To encourage questions, I give out NASA stickers. Teachers can get packets of them free for the asking. For top scorers on tests, I’ve been known to give out astronaut ice cream, meteorites and astronomy posters. If they’re free or low cost, why wouldn’t you? Make it fun! We look at spectral tubes (a variety of them: glowing gas of hydrogen, helium, neon, argon, krypton, mercury and nitrogen), and the students get to keep their diffraction grating glasses. Sometimes, days later, I see them walking around campus wearing their white cardboard glasses.

When the topic of stellar classification comes up, I balk at using the canonical pneumonic. I can’t do it. I can’t bring myself to say, “Oh, be a fine guy kiss me” for the spectral classes O B A F G K M. I have to use, “Oh, boy, another F’s gonna kill me!”

Doppler shift? After the lecture, after the Lecture Tutorials, after the discussion, then I tell them to remember, to think about car’s taillights (red), which are going away. “You know those new halogen headlights? They can look blue as they’re coming towards you.” It’s important to give them this cheat last, as a check of their reasoning skills. It should be a comfort them, not a replacement for understanding the concepts.

Same with phases of the moon. All waxing phases are lit up on the right; all waning phases are lit up on the left. At the end of the class on lunar phases, I give them a cheat. The curve of a small letter b (I draw it on the board) in the word “born” shows you the shape of a crescent moon that is waxing, getting larger, lit up on the right. The curve of a small letter d as in “die” shows the shape of the waning crescent, lit up on the left.

While talking over several classes about the stages of stellar evolution, I describe hydrostatic equilibrium as the balance between the force of radiation from the core pushing outward and gravity pulling inward. For a white dwarf—the force keeping the star from gravitational collapse is electron degeneracy pressure. In a neutron star, the force opposing the crush of gravity is neutron degeneracy pressure. “The neutrons are touching—how much closer can they get?

I ask the class, “For a black hole, what force holds the matter up against the force of gravity trying to pull it inward?”


I wait ten seconds. Repeat the question. “What outward force balances the pull of gravity in a black hole?”

No one ever speaks here. Finally, when I can’t hold it in anymore, and I say, “You’re right! Nothing! It collapses completely.” They look startled at first, but it generally begins a discussion.

I love the puzzled looks when the subject of spacetime curvature comes up. The students’ faces as they try to figure out in which direction we have to point to, not any of the three dimensions of space that we know—not up/down, back/forth, right/left. Space is curved by large masses into yet another direction that we can’t visualize. For some of them, it’s the first time they’ve heard that space has more dimensions than three. Special relativity and general relativity were proposed by Einstein in the early 1900s. They wonder out loud, “How can this be generally agreed upon by the scientific community if I’ve never of it before?” Space is curved around large masses. I can see they feel like they’ve been let into an adult secret, a profound concept that they are only now mature enough to grasp.

Do they leave my class and look around at people on the street wondering, “Does he know? Does she know? Do they all know? Did they all know yesterday and I didn’t?”

I use a number of online clips. I play the minute-long YouTube video of the hammer and feather drop on the Moon (by the Apollo 15 crew) when I talk about Galileo. Commander David Scott drops both objects simultaneously, a hammer and a falcon feather. Both objects hit the lunar surface at the exact moment.

Another useful YouTube video is a demonstration of the inverse square law, done by a guy with a delightful accent. You’ll find this butter gun experiment under the title, “Inverse Square Law: a Beginners Guide.” The narrator puts a piece of toast near the butter gun and shoots. “Oh, no! Too thick! Let’s move it back and put TWO pieces of toast there.” Another shot. “Oh, no!” The wall is covered with butter above the two pieces. Put four pieces. Shoot! “Ahhh.” And now we’re all right. Juvenile? Maybe. Memorable? Absolutely.

And I’m running out of time. I have more. The methods of talking about time dilation, the labs we love and those we don’t, and some fun lab and class demos we do. I’d like to bring you that in Part II. What’s the formula? Caring and sharing. Giving the students a fun experience they won’t soon forget and enough knowledge to make them lifelong learners. Thank you for listening. Diane Turnshek, signing of from 365 Days of Astronomy.

Beautiful word clouds

Lecture Tutorials for Introductory Astronomy
by Prather, Slater, Adams, and Brissenden
ISBN-13: 978-0-13-239226-6
ISBN 10: 0-13-239226-7

Feather and Hammer Drop on the Moon

The Inverse Square Law: a beginner’s guide

End of podcast:

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