Earl Zwicker has been involved in physics teaching and research at IIT since 1953. He received his Ph.D. there in 1959, and frequently teaches the freshman physics course. Thanks to physics teacher colleagues, his approach to teaching/learning has been converted from traditional to phenomenological.
Are you interested in new ideas to try in your classes? Are you looking for fresh ways to stimulate your students to learn? To find more effective teaching strategies with apparatus you already have? Could your enthusiasm use a little "re-charging" now and then? And would you like to do these things in a way that would be fun for you and at minimal cost of your time and effort? Then read on!
There is a group of us in the Chicago area who meet once a month during the academic year. We call ourselves the ISPP Group, and we are teachers of high school and university physics. We have learned how to do the things described in the first paragraph over the past nine years, and we'd like to share some ideas with you. We invite you, in turn, to share with us. 
In order to give you a feeling for what we do, let's run a "gedanken experiment" together; come along with me to an ISPP meeting! We'll synthesize the meeting by putting together bits and pieces from various past meetings (date and place indicated in parentheses), and by interjecting some of the philosophy we have come to believe in and some of the emotion we feel. Our writing style will try to reflect the informality of the meeting. Now - off to Chicago!
We arrive at our meeting place (a high school or university) right on time: 6:30 PM. We are in a typical physics classroom with lab benches and apparatus (or maybe in a lecture auditorium with a demonstration table at the front, and an adjacent preparation and apparatus room). There are about 10 people already present, talking in groups over coffee and doughnuts (and sometimes homemade pastries). We help ourselves to the goodies and join an old friend and some new ones in conversation. During these first 15 to 20 minutes you might find yourself sharing ideas on virtually any casual topic at all, from, "Have you tried this in your class yet?" to, "Did you know you can do this with your calculator (showing us)" to, "local school politics." You get an idea of what other physics teachers are thinking about, and what is going on at their schools. You also get to poke around the open cabinets or apparatus room for new ideas. More and more people drift in and greet one another, and soon the host asks, "Has anyone got anything? Who wants to be first?" - and we begin ....
Ian Laing (October, 1975, Northeastern Illinois University) comes forward and explains that when first developing the concepts of "image" and "object" he found that some of his students had a problem: they insisted that the virtual image as seen in a plane mirror should lie at its surface. How could Ian convince them otherwise without resorting to ray diagrams, which at this early stage they would not understand? An idea! Ian got out his Polaroid camera and took two pictures, first focusing on the image of a word painted on the mirror's surface, and then focusing on the image of the camera in the mirror. Even as Ian tells us about his idea, he passes out pairs of photographs for us to inspect, making the obvious point that the images of the camera and of the word on the mirror surface are not simultaneously in focus in either photograph, and so could not lie in the same place. Neat! Of course, Ian let his students study the evidence and draw their own conclusions, becoming ego-involved as they convinced themselves of the error of their initial concept. It also led them very naturally to ask the next question, "If the image is not at the mirror's surface, then where is it? How can we find out?" And under Ian's subtle guidance, his students were on their way to doing physics instead of having physics told to them.
Next, Pete Insley reminds us of how he got his students to use the idea of the proportionality of the sides of similar triangles to measure large distances, such as the height of a building, and he was wondering if he could use the same idea for small distances. So - Pete shows us how he worked it out, and had his students measuring the thickness of hairs using two microscope slides, a meter stick and a laser. "Let's do it," we say. We tape a pair of slides together at one end so they can pivot on their line of contact, and then sandwich a hair between the slides parallel to the line of contact and a measured distance away from it. A low-power, neon-helium laser beam is directed at the slides, reflecting back onto the wall. By measuring the separation between the reflected spots on the wall and the distance from the slides to the wall, we invoke the proportionality of similar triangles and find the thickness of the hair. Great! Pete remarks that his students have done it with sunlight as well.
You notice that during and after the presentations made by Ian and Pete there were questions and discussion. Frequently the person sharing his ideas "role-plays" with us --- he is the teacher, we are the students --- in order to make us aware of the pedagogy he has worked out to optimize learning. Soon one of us will see a better way to do it, or a variation on it, or a connection it has with something else - and we all end up learning several different approaches to use with a given apparatus in order to teach some physical concept. But back to our meeting ....
Roy Coleman (May, 1977, Morgan Park HS) comes forward, gripping a steel (ringstand) rod at its center between two fingers. He raps one end sharply against the hard floor, and we hear the rod ring. Roy points out, suiting his actions to his words, that we can grip the rod at 1/4, 1/2, etc. of its length and generate different harmonics, so the single rod may serve as several different tuning forks if there are none handy. We get all kinds of additional discussion and ideas from this, such as matching the frequency of the sound that we hear with a well-calibrated audio oscillator, and taking this, together with the length of the rod and the boundary conditions, to calculate the speed of sound in the rod. We check the result with higher harmonics. Roy next holds the ringing rod at its center in a horizontal position, and slowly rotates it about its vertical axis. Each of us hears the sound grow alternately louder and then softer. Smiles and knowing looks break out here and there as we suddenly understand. The ends of the rod behave as two identical sound sources, and we are "hearing" the nodal lines of the interference pattern change position as the rod is rotated! Neat! More ideas - touch one end of the ringing rod to the surface of water in a beaker and watch the spray that results - to convince students of the oscillating nature of the rod. Or make a wine glass ring and watch a "grip-grop" (a light plastic ball) bounce around inside. Or ... and the ideas continue.
A characteristic of our meetings is informality. Everyone feels free to speak up, to make comments or ask questions, to laugh, to make jokes or puns. Visitors to our meetings often comment on this, but the relaxed atmosphere is invariably regarded as a strong, positive element. We feel so much at home with each other that we're like one large family by now, and newcomers and those who attend relatively few meetings very quickly share this feeling and find themselves contributing freely to the ideas and action. There are no particular leaders and no particular followers, although the host more often than not takes the responsibility to move things along. There are no "Professors" or "Doctors" or "Misses" - we're all on a first-name basis. The meetings are completely open, and many of us occasionally, and sometimes frequently, bring along students, wives, our older children who can learn and participate. And, of course, we're always inviting colleagues and other friends along. By now, at our synthetic "gedanken" meeting you should be feeling like you are among old friends ....
Larry Alofs (January, 1978, Roosevelt University) comes up front and he then attempts various frequency measurements, and uses tuning bars to show us 440 and 436 Hz accurately. Jim Williams says he will bring us the software next time - meaning he will pass out diagrams of the circuitry and elements needed to do this. As a final twist, Larry fastens a marker pen onto a 60-Hz tuning fork with a rubber band, strikes the fork and then draws the pen across a sheet of paper at a uniform rate - tracing out a sine curve in the process, and showing us how to convince students of the nature of the motion executed by the tines. Very nice!
Threaded randomly throughout any given meeting, announcements of various kinds are made, with the information usually written on the blackboard or passed out on ditto sheets. It is also usually summarized in our monthly newsletter, the ISPP Reminder. (More on that later.) Someone might remind us of the next Chicago or Illinois Section AAPT meeting, and suggest there is still time for contributed papers. Other types of information disseminated are: summer and academic year workshops for teachers (Careers, Education, Holography, Piaget), student contests of various types to stimulate academics (Bridge Building, Academic Olympics, Mathematics Olympics), good magazine articles, the latest free films (we occasionally show one), new filmloops and slides from AAPT and elsewhere (almost always shown), where to get it free or cheap (catalogs, companies, state publications, federal surplus), good books with lots of ideas for us to use:
Joe Meyer (December, 1976, Oak Park-River Forest High School) gets our attention. He passes around for inspection an electronic timer that one can make from a cheap calculator (available at a workshop conducted by Joe and Jim Williams at the National AAPT meeting, Rolla. Cost: about $ 10 (*this calculator is no longer available) - and we see how well it works. And Lee Slick gives us a "Commercial" on buttons, bumper stickers, games (design your own), famous scientists, etc., and passes out five pages of information on these things. Lee also has a student "billboarding" various buttons (Fig. 1), and briefly discusses use of this sort of material to motivate student learning. Others point out various strategies they have found effective. Roy Coleman (March, 1977, DePaul University) flashes a T-shirt at us bearing the words "Physics Phreak," and tells us we can buy them from him.
Somewhere along the line of ISPP meetings we got the idea of the Free Giveaway. This is a piece of apparatus or material costing less than $ 1.00 which is given away free to the first 30 people coming into an ISPP meeting. The host is responsible for providing the Giveaway, and at some time in the meeting he shows the rest of us how it works, and how it might be used to teach a concept.
Our host for this evening is Ed McNeil (November, 1976, University of Illinois at Chicago), and he now comes forward and strips a piece of ticker tape from a large roll. He then gives the piece a half-twist and fastens the ends together to form a Möbius strip. He points out that one may have a student trace a line along the length of the strip with a marker pen to convince him of its properties, but then Ed asks us what will happen if the strip is cut in half along its length? This generates much discussion, but in the end we resolve the matter by doing it, and some few of us are correct! One of us wonders aloud to the rest, "What will result if the new strips are cut along their lengths?" More discussion - but then we hurry to cut them and find out what really does happen! We begin to explore how we might have predicted the observed results, and Ed announces to us that the Free Giveaway is a roll of ticker tape. We all come up and get our rolls. There are scissors and sticky tape, and many of us begin our own experiments in tape-topology, challenging each other. What happens if we have two intertwining Möbius strips and we cut one along its length? Both? What else can we use the tape for? Using an inexpensive "doorbell" timer with carbon paper, we can fasten the tape to a bike, a student, a car ... and measure speed and acceleration. Bill Conway (January, 1979, Lake Forest High School) shows us still another use for ticker tape.  (See Fig 2.)
The "continuing" of a problem for which we cannot find a satisfactory answer from one meeting to the next usually occurs several times during the year. Such a "continuing" problem occurred when Harald Jensen (now in California) suggested it to us by mail: Purse your lips (as if to whistle) and blow vigorously on the palm of your hand. Note the temperature sensation. Now open your mouth wide (as if to yawn) and exhale on the palm of your hand. Note the temperature sensation. Query: Why is the first temperature sensation a lower one? (Try it!) After we all had tried it, someone suggested that "expansion is a cooling process," but most of us were not happy with that. The meeting was at an end, and was the first of the academic year. But three months later, at the third meeting about halfway through ...
Somebody recalls the problem posed by Harald. As we are all blowing on our palms again, someone points out that the expansion brought about by pressure difference from the lungs to the atmosphere is insufficient to account for the difference in temperature sensation. Henry Glab (December, 1978, Roosevelt University) points out that eduction of the surrounding cooler air might be a factor. The word "eduction" brings out questions as to its meaning, and Larry Alofs explains how a deep well jet pump works using this idea, so we all could understand the process, and Earl Zwicker points out how it is used in diffusion pumps as well. Somebody suggests that we use a thermometer to find out whether the sensation of hot or cold really corresponds to hotter or colder air from our mouths, but we can't find any. Jim Williams points out that semiconductors are temperature sensitive, and pulls out of his pocket a diode that he happens to have with him. Ed Piotrowski (our host) brings in a digital voltmeter (DVM) and Jim hooks up the diode, explaining that the DVM will bias it. Sure enough, a steady voltage is indicated, When Jim puts the diode between his fingers the voltage drops, indicating its temperature went up; the action reverses when he removes his fingers. Now we have a thermometer, albeit uncalibrated, and everybody can read it at once besides! Next, with all of us now watching expectantly, Jim first "whistles" and then "yawns" air at the diode. It appears that there is no temperature difference. In order to better control the experiment, somebody takes apart a four-color ball point pen, and suggests blowing from the large to small end of the pen barrel to simulate "whistling," and from the small to the large end to simulate "yawning." Jim does this (Fig. 3), again getting no temperature difference between the two experiments, while several of us verify that this use of such a pen barrel produces the same temperature sensations on the palms of our hands as we had before. Another idea! Somebody suggests placing a piece of moistened paper over the diode and blowing, just to see that the "thermometer" registers a temperature drop.
We see the temperature drop when Jim "whistles" at it, but no temperature drop when "yawning" at it. We've got it! The moist paper exhibits the same temperature behavior as we experience blowing on our palms! We quickly try other experiments that suggest themselves, and our hypothesis quickly becomes an accepted explanation, a theory. Very nice! Our conclusion is that evaporation of moisture from the skin produces the lower temperature sensation. The evaporation is greatest when the dryer, educted air lowers the humidity next to the skin, hastening evaporation of moisture and removing the heat from the skin required for the process - hence, cooling. On the other hand, when blowing on the skin as if to yawn, the eduction of dryer air does not occur in any significant degree, so the humidity of the air next to the skin is not reduced, but rather it is raised (air from the lungs being high humidity air), resulting in decreased evaporation from the skin, and a sensation of increased temperature as less heat is removed by evaporation. Beautiful! We are grinning at each other, elated!
The kind of thing that just happened, where we experience the excitement and spontaneity of doing physics together, does not occur at every meeting. But it happens often enough so that we don't want to miss the next! It is almost as good as Harald Jensen working an idea on us. Which reminds me, maybe this is a good point to back up to the beginning and explain how we got started.
In 1967 the National Science Foundation funded a project called the Illinois State Physics Project (ISPP). Ralph Miller (Greenville College), Charles Weller (University of Illinois at Champaign-Urbana, science education) and Robert Waddell (Eastern Illinois University) from the Illinois Section of AAPT teamed up with Harald Jensen (Lake Forest College) and Ed Schillinger (DePaul University) from the Chicago Section in putting the proposal together. It ultimately included 11 colleges and universities involved in summer and follow-up In-Service Institutes for high school physics teachers. A primary focus was to reverse the decreasing enrollment trend in high school physics courses. There were admirable successes which persist to this day, as well as failures. But one of the long-term effects is the existence of the Chicago ISPP Group.
In 1970, with NSF funding at an end and other funding impossible to get, the ISPP leadership held a meeting and decided to abandon further efforts to continue the project.
Following the meeting, Harald Jensen and three or four others of us from the Chicago area were seated around a table having some soda pop and discussing the situation when Harald said, "We can't let this happen! There are just too many worthwhile things coming out of this to let it stop!" And then Harald said we'd keep it going ourselves. We quickly made up a list of nine schools (universities and high schools) where we knew physics teachers who would be willing to host, set down each teacher's name and a calendar date in each month of the academic year, set the time from 6:30 to 8:30 PM, and that was that! We got a list of all ISPP participants and staff, picked out those within 50 miles of Chicago, and when September arrived we mailed out our first ISPP Reminder - though we didn't call it that then - inviting people to the meeting. The meeting was great, and they've continued ever since!
Now Harald was our real leader. Although we have all contributed to the meetings in various ways, Harald is the person most of us try to emulate. "Start with the phenomenon!" admonishes Harald, as he puts the live physics on the table in front of us. Exciting our curiosity and then involving us in a dialogue combining pedagogy and physics, Harald inspires us. We go back to our students with new ideas and enthusiasm, and it works! What Harald has showed us we call the "phenomenological approach," "let the phenomena do the teaching" --- and then we believe in it because it helps us get more learning done than anything else we've tried so far.
Over the years each of us has tried to inspire the others by following Harald's example. We start with a phenomenon containing the physics we want our students to learn, then develop a way to make them curious about it. Curiosity may be defined as an emotional need to understand --- to satisfy the intellect. Once we have emotion on "our side," intellect tends to follow and it is nearly impossible to keep the learning from happening. And then we get our students involved in a dialogue, experimenting together with the live phenomenon, drawing the physical concept(s) out of our observations, experiencing that "mental smile" as the idea suddenly becomes clear and they begin to understand the beauty of it! Marvelous!
Well, our "gedanken" meeting is beginning to break up now. It is past 8:30 PM and some friends are leaving, but some of us coalesce into conversation groups again. Let's linger just a bit longer and pick up a few more ideas ....
By now it is evident to you that our ISPP group believes in the "phenomenological approach," although the presentations at our meetings are not always as elegant as this might lead one to expect. But we continually do try to achieve the ideal set forth by this approach; we have something to "shoot for." The important thing is to bring in some phenomenon, some new idea, and share it. We are continually "stealing" ideas from anyplace we can find them, and alerting each other to good sources. It is one thing to read, or hear about an idea; it is quite another to experience it "live" at a meeting. Experience is still the best teacher! Whether it is something that takes 60 seconds or 60 minutes does not matter; the important thing is to do it, not just talk about it. There are several ideas that have developed over the years which make our meetings more valuable to us. The Free Giveaway is one of them. We also have learned to schedule each successive monthly meeting on a different day of the week, Monday through Thursday. That way a person who is not able to attend, say, on Mondays, has a chance to attend meetings scheduled on the other days. We try to alternate the locations of our meetings between city and suburbs, so that people will not always have to travel far to make a meeting. And we try to see that a given institution is not asked to host during the same season every year --- say in the dead of winter. Incidentally, we estimate that the average person in our group spends about 45 minutes getting to a meeting. No one receives any academic credit, travel expense, tuition, or other incentives. What we do get from our meetings is obviously of such value to us that we do not need other incentives. The backgrounds of ISPP teachers span the spectrum from "young and inexperienced" to "retired and having more fun than ever!" - so age and experience are not limiting factors.
For his tireless work with ISPP and for providing his fellow-teachers with "insights, ideas, concepts, and innovations" the appreciative members of the group, at their June 1979 meeting, gave an award to the author of this article. Nearly 200 people participated when Earl was given a 28-mm lens, a plaque, a "Flying Finnegan" game and a popular desk-top wave machine. Our informant, Roy Coleman, of Morgan Park High School, says, "We all consider him to be a Non-Stop Teacher's Teacher."
It turns out that the number of people attending a meeting is not very important. Our meetings have varied in size from about 12 people (we had a heavy snow that time!) to as many as 85, and they average somewhere around 30 over the years. The number and quality of useful ideas we get out of a meeting appears to be independent of attendance. Some meetings are relatively unexciting; others leave us buoyant with enthusiasm; but we invariably come away with useful ideas which make our time well-spent.
We do mail out the ISPP Reminder, a monthly newsletter which reminds us where and when the next meeting is, and includes a map and directions showing how to get there. It is nothing fancy, consisting of two or more dittoed pages, sometimes poorly typed and not always well-written, though we do strive to express ideas clearly. A regular feature is a summary of the things that happened at the last meeting; we have found this to be particularly useful. When doing "lesson planning", one frequently recalls an idea he experienced at one of the meetings. He can dig through his file of ISPP Reminders and sharpen his memory. The name of the person who presented the idea is usually mentioned, and the telephone allows us to get still more information. Over the years we have received requests from friends to put them on the mailing list, and they are usually kind enough to send us two or three dollars to cover mailing costs. As a result, the ISPP Reminder is now mailed to people all over the country, and it is gratifying to know that they too find it useful.
One parting thought. Most of us tend to assume that our colleagues are familiar with the ideas we use everyday in our classes. It usually comes as a surprise that more than half the people at a meeting have not seen what you take for granted! If they are familiar with the basic idea, they have not experienced the particular strategies you have developed around that idea which are uniquely your own. So --- don't be shy about bringing something in to show everyone else.
Well, our "conversation" has rambled on long enough. I guess the message is, "If we can do it, you can do it." You don't have to wait until the next AAPT or other professional meeting to re-charge your enthusiasm. Start your own group and live it up! You will find your repertoire of "instant ideas" will grow; if your students begin to lose interest or fail to understand a concept, one idea after another will pop into your head to meet the challenge. It obviously doesn't happen overnight, but it will not happen at all unless you act now. You've got The Physics Teacher in your hands, and it is filled with many new ideas that you and others can do. Go ahead! Call a friend!
I thank all the teachers of ISPP for being the wonderful people that they are, and for having taught me (and each other!) so much. Special thanks to Ed Schillinger, Joe Meyer, Miller Clarkson, and Bill Blunk for their help with this article. And we all give special thanks and recognition to the people and institutions who have served as ISPP hosts over the years:
|Fig 1 on left - Lee Slick (left, Morgan Park High School) looks on as one of his students advertises a fascinating variety of physics "buttons" to the delight of Joe Meyer (right, Oak Park-River Forest High School) and the rest of us. We have learned that fun and fascination are helpful and not antithetical to learning, both for students and teachers. Relax and enjoy the physics, and your students will too! The reverse also works.|
|Fig 2 on right - Bob Pasquesi (January, 1979, Lake Forest High School) of Loyola Academy is measuring the tensile strength of ticker tape. This idea was "stolen" from The Physics Teacher by our host, Bill Conway, and although some of us had read about it, most of us had not experienced it. A serious and at the same time exciting and fun part of our meetings is learning from each other how live physics may be used to stimulate our students to learn. At this meeting we worked in groups of two or three, vying with each other to see who could get the highest value for tensile strength. In the process we learned how "cracks" and other imperfections in boundary conditions on our specimen tapes could act to focus stress and lead to low values of tensile strength.|
|Fig 3 on left - At our December, 1978 meeting at Roosevelt University we needed a thermometer but could not quickly find one. Jim Williams (Bremen Township High School) improvised one using a semi-conductor diode connected to a digital Voltmeter. He is blowing at the thermometer (diode) through the barrel of a disassembled ball point pen, first from the large opening and then from the small opening, in order to see if the temperature depends on which opening the air comes from. Do you think it makes any difference? The temperature sensation produced on the palm of one's hand does depend on which opening you blow from! Use a four-color ball point barrel, or simply "whistle" or "yawn" the air from your mouth at your palm.|
|Fig 4 on right - Harald Jensen (June, 1973, Lake Forest College), our host, shows us how to make something exciting out of the three-dimensional phase diagram for carbon dioxide displayed on the table. Always start with the phenomenon! He has filled a thick, glass bottle about one-half full of dry ice "pebbles," stoppered it very tightly, and placed it in a Plexiglas shield for safety.|
|Fig 5 on left - At our first meeting of the academic year (October, 1978, IIT) Roy Coleman of Morgan Park High School shows us the Free Giveaway, a 5 x 5 set of foam blocks, each bearing a red and blue number pair. At Roy's direction we team up in groups of two or three, and each group receives a foam block. Our challenge is to determine the significance of the number pairs on all the blocks. We busily weigh the blocks and begin to see a pattern of mass quantization emerge as we enter our data on a grid placed on the blackboard by Roy. We also investigate the way in which the mass is distributed (without taking the blocks apart!). After perhaps 25 minutes, the complete picture unfolds, and we finally see the logical significance of the number pairs. This neat exercise to sharpen observational and analytical skills was "stolen" from Chirold Epp.  Each of us left the meeting with his own set of foam blocks, quantized masses, and a copy of Chirold's article.|
|Fig 6 on right - At Lake Forest High School, Bill Conway, our host, shows us the results of an experiment conducted by his students with balloons. He filled a green balloon with carbon dioxide, a pink balloon with air, and a yellow balloon with helium, so that all the balloons initially were the same size. They were then tied to a rod for observation. The next day it was found that the balloon filled with carbon dioxide had lost the most volume. Is this to be expected? We hypothesized that the color of the balloon might have something to do with it, but Bill's students had already thought of that. The experiment was repeated with the same gases in balloons of different colors, but the results were the same. Try this one for your group and let us know what you discover!|