Date: November 15, 2011
Title: CMU Physics Concepts Program: Decades-long Outreach to Middle Schools
Podcaster: Diane Turnshek
Organization: Carnegie Mellon University
Description: Wonder why the sky is blue? Why reflection nebula give off blue light? Blue light scatters more easily than red light. This year, one middle school student is experimenting on the concept of scattering through the CMU Concepts program, which is designed to provide mentoring and equipment for students participating in the Pennsylvania Junior Academy of Sciences. We’ll outline the procedure and outcomes of a successful astronomy science fair project that anyone can do.
Bio: Diane Turnshek is Outreach Coordinator for the Physics Department at Carnegie Mellon University. She teaches “Introduction to Astronomy” at CMU and “Physics and Science Fiction” at the University of Pittsburgh.
Sponsor: This episode of “365 Days of Astronomy” has been sponsored by the Lake County Astronomical Society in northeast Illinois.
Hello, this is Diane Turnshek and welcome to 365 Days of Astronomy. I’ve been the Outreach Coordinator for the Physics Department at Carnegie Mellon University for one year and today I’d like to tell you about an outreach program here that long predates me.
The CMU Physics Concepts Program is a long-standing outreach program in which CMU students mentor inner-city middle school (6, 7, 8th grade) students. It has been part of the CMU Physics Department since the late 1990s and is run by Professors Leonard Kisslinger and Tom Ferguson, assisted by about twenty-five faculty and physics undergraduate and graduate students.
Professor Kisslinger’s research spans the universe from studies of the quark/gluon structure of hadrons and nuclei to cosmology. His path to CMU, where he’s been a professor since 1969, went through St. Louis University, the University of Indiana, Case Western Reserve and MIT. In 2009, he won the Mark Gelfand Service Award for Educational Outreach for sustained, effective community service.
His dedication to the Concept Program is commendable, continuing it through student behavior problems, Pittsburgh’s heavy snowfalls, complex logistics and several middle school closures (for which he had to establish new relationships with administrators and science teachers). Taking students out of their environment and bringing them to campus allows them the chance to interact with positive role models from the university community and form solid relationships, while learning the fundamentals of science in updated laboratories.
Overheard in the bus line:
“Where you going?”
“I’m going to college.”
Here’s how the program runs. During the first semester of the academic year, each seventh and eighth grade student, with the help of his or her mentor, plans a project to test an idea associated with a physics concept (astrophysics, biological physics, etc.). The mentor and mentee agree on a topic that is interesting to both of them, doable in the time frame allotted and has a single, clear hypothesis to be tested. The student must demonstrate a sufficient background to understand the concepts involved.
A weekly session runs for two hours every Tuesday afternoon. A Grable Foundation grant pays for transportation for the students to and from the CMU labs, a small hourly wage for undergraduate helpers and refreshments. The students’ goal is to finish the project by Thanksgiving and practice their presentations in December and January.
The students gain hands-on experience by carrying out a scientific experiment, analyzing their data and presenting it to scientists at the Pennsylvania Junior Academy of Sciences. The first Saturday in February is when the presentations are made. The Pennsylvania Junior Academy of Sciences was established in 1934 for junior and senior high school students. Students give ten minute oral presentations and then answer questions.
The judges use five criteria: scientific thought, experimental methods, analytical approach, presentation and a fifth one called “Judges Opinion,” a catch-all category that takes into account the age of the student.
During the second semester, after the Pennsylvania Junior Academy of Science Fair, weekly lectures and demonstrations are given by professors in the department. Selection of the lucky new mentees is made by lottery—there are always more students who want to be in the program than can be accommodated. Sixth graders join the group in the spring to learn the physics concepts necessary for deciding on their own projects the following semester in the fall.
This program has been running for decades and has worked smoothly. One of the projects I’m working on with a middle school student this semester asks the question, “Why is the sky blue?” In class, in my astronomy class, I always demonstrate this concept. White light from the sun is actually a mix of all the colors. When the light hits the top of our atmosphere, some of the violet light scatters away, giving sunlight a yellow cast. Visible light with shorter wavelengths scatters away more easily than longer wavelengths of light, meaning the blue light scatters all over the sky. Everywhere we look up on a bright sunny day, we see blue light from the sun that has been scattered in all directions, some of it towards our eyes.
The man on the street? Yeh, he doesn’t get this. Most people think the sky is blue because it’s a reflection off the ocean. Others think that air is actually blue (like blue particles in the air) or that sunlight is blue.
I asked a student once “Why is the sky blue?” He gave me a blank look of total incomprehension. “Why is the sky blue?” I asked him again.
He said, “What?”
“Why is the sky blue?”
He said, “What?”
“Why is the sky blue?”
“Because he’s holding his breath? he said.
I said, “What?”
(He thought I’d been saying, “Why is this guy blue?”)
Okay, so I do a demo in class. You could do it with a fishtank of water, a projector and a white screen. Turn on the light so the class can see, then start adding milk in small quantities to the liquid. If you add too much, though, you have to dump the whole thing and start again. I use CoffeeMate (not any of the other brands, the non-dairy creamer brands; they don’t create the same effect), a quarter teaspoon at a time. Stir. As the water gets cloudier, the light traveling through it gets redder and redder until the light goes out all together. Astronomers call that extinction, when dust and gas in the interstellar medium completely block the light from stars.
Be careful not to use a document camera for this, or any other sort of monochromatic light source. Sometimes, I use an overhead projector and two beakers of water. That way, if I go too fast with one beaker, I still have the other one to demonstrate with—as I slowly add the CoffeeMate, first the light coming through looks yellow, and then orange, and then red, and then it disappears. The red light with its longer wavelength powers through—it travels through the cloudy liquid. We say the light is reddened. If you look at the beakers instead of through them, the cloudy liquid looks bluish. The blue light comes up out of the white overhead projector bulb and scatters every which way, some towards your eyes, making the contents of the container look bluish.
Reddening, that’s a scientific term. It’s not at all like redshift. When the sun is on the horizon at sunrise and sunset, it has a longer path through the atmosphere and looks redder than it does when it’s overhead. Reddening of starlight indicated there is dust and gas in the way, between you and the star. You can look at the spectrum of a star and see what the spectral type is, thereby knowing the temperature and the color—but if the star looks redder than you think it should, it has to be reddened by dust and gas in the way. Reddening of starlight provides a way to pinpoint dust and gas in the interstellar medium that might not be visible otherwise.
Also, reflection nebulae in the interstellar medium appear blue. They are on the sides of bright stars, like the nebula in the Pleiades cluster or the Witch Head Nebula; that’s another one; it’s on the side of Rigel in the constellation Orion. Gas and dust scatter the blue light in all directions, some towards our eyes. The Trifid Nebula has another reflection nebula in it.
My mentee has set her experiment up like this. Here’s her equipment:
Beaker of water (600 ml)
CoffeeMate and 1/4 teaspoon measuring spoon
Red filter and blue filter
Ohmmeters and wires
Photocell (can be purchased lots of places, for instance, at RadioShack for under $5.00) Resistance is less when light hits the face of the photocell, so it is used to measure levels of light. A common usage of photocells is in devices that turn on when it gets dark, like night lights.
She hooked up the photocell to the wires and measured resistance with the ohmmeter from a 100-watt bulb placed almost right up against the other side of the beaker filled with water. Then she measured resistance with the ohmmeter after placing the blue filter and then the red filter in between. She found that she had to wait about twenty seconds before taking the reading.
Next, she put a little bit of CoffeeMate in and stirred, repeating the steps with no filter, then the blue filter and then the red one in turn. She’ll try adding more CoffeeMate next week and repeating the steps. She should find that with the blue filter in the way, the light drops off faster than with the red filter in the way. When she plots it all up, her data should support her hypothesis that blue light scatters more easily than red light.
Thanks for listening today. This is Diane Turnshek signing off for 365 Days of Astronomy.
End of podcast:
365 Days of Astronomy
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