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Dr. Elwood Schapansky 1986 - 1987

Lecture Perspective

ALBERT EINSTEIN once noted that "my laboratory is in my mind." He is famous in scientific circles for his imagination and his convincing thought experiments. What he
and other great innovators did in their imaginations was nonetheless obscure to most laypersons . . . How has modern technology influenced the demonstration and teaching
of these great ideas?       

Einstein's Elevator:
Teaching & the Teaching of Science

Elwood Schapansky
Professor of Physics

I AM TRULY HONORED by the presence of so many colleagues, students and friends here today. Your presence makes this day unique and extra special for me-and I thank you for attending. I hope we have a good time together.

There is one couple here today that is more than special-my parents. It is also a significant day for them since it is their 53rd wedding anniversary. I'd like them to stand so I can introduce them. They have chosen to spend this day with me, and I'm proud to have them here.

I suppose all faculty lecturers have a story to tell about accepting this honor, and I am no exception. When past lecturers, Barbara Lindemann and Ray O'Connor, stopped by my office one morning last spring and told me of my selection, my first reaction was one of surprise and concern. What would I have to say to the community that would be meaningful and interesting?

My second reaction was to say, "I don't want the responsibility and work that goes along with the honor." I took a weekend to think about it and decided, happily, that I would use the lecture as a learning opportunity for myself and as an opportunity to create something for the college. I decided if I couldn't have fun creating this day, it wasn't worth it. So, I have had a good time learning new computer and video technology, building some new demonstrations to share with you and selecting some old demonstrations which I find especially enjoyable.

My presentation today will be made in four parts. First, I would like to use the latest in computer-coupled video technology to demonstrate the use of this new media in the presentation of a science-oriented lecture. Second, I would like to explain some aspects of what are called Lissajous figures, the beautiful figures seen both at laser light shows, as art, and in electronics laboratories, as measurement tools. Third, I will demonstrate some of the properties of liquid nitrogen and its use in the laboratory. Finally, at the request of my son, I will show how the common carbon dioxide fire extinguisher is a fantastic substitute for a rocket engine when demonstrating the principles of rocket propulsion.

One of the most exciting developments in educational technology is the videodisk which, coupled with the microcomputer, becomes a powerful and useful teaching tool. The educational impact of these devices, when joined, is just emerging. Exciting innovations are coming out weekly, and the technology is now ready for teachers to capitalize on it. Right now, there are only a dozen or so videodisks available in the physical sciences, most of them being produced by NASA and related to our space efforts and astronomy. Others are simply copies of classic films that were easy to produce.

These videodisks allow us to select from thousands of images and films in an instant. One can, with the touch of a button, look at earth from space, or see the surface of the moon and planets. Access is immediate and the images are the ultimate in video clarity. Lessons and lectures can be enhanced by actual pictures and demonstrations of physical phenomena.

It is my feeling that education and teaching can be revolutionized in the near future if enough effort is put into creating the proper video material. I envisage the creation of video textbooks and encyclopedias where the best teachers and most knowledgeable scientists are permanently recorded and made immediately available to all of us. Ideas will be presented at various levels of complexity by different teachers so that students will be able to select instantly and learn at levels appropriate to their backgrounds. They will be able to easily replay and review the material, since the videodisk allows immediate, pushbutton access and playback.

The title for my lecture came as a result of seeing a demonstration on videodisk. I would like to explain a little about videodisk technology and then demonstrate its power as a teaching aid.

This is a videodisk (Fig.1). It is the size of a 12-inch phonograph record, but its mode of information storage is completely different. On a phonograph. A videodisk looks much like a common phonograph record, but the differences are substantial. The grooves on a videodisk are so close together that they act like a diffraction grating. record there are 500 tracks where audio information is stored by varying the depth and width of a track. The phonograph record will play for approximately 15 minutes, using a total track length of approximately 350 yards. The videodisk on the other hand, has 54,000 tracks and a total groove length of about 20 miles! There are two formats used in recording information on the disks-constant angular velocity (CAV) and constant linear velocity (CLV). In the CAV mode, like the one I am using today, each of the tracks on the laser disk can store a complete digitized video image, which allows one to store 54,000 still pictures or a 30-minute movie that can be played back on a television monitor.

Using the CLV mode, there are from one to three images per groove, and twice the information can be stored. This latter system is more complicated though, since the speed of the disk must be varied, and it does not have the versatility of freeze-frame or single-frame operation.

Data is read from the disks using a low-powered helium-neon or diode laser; therefore, a single videodisk image can be played for long periods of time without degradation of picture quality. There is no physical contact between the disk and the reader, as in the case of phonograph records. The laser beam is focused onto the reflective surface of the videodisk, and the micro-depressions on the recorded surface produce a signal that can be processed to make it compatible with conventional television monitors and receivers. Most disk players offer the flexibility of playing forward, reverse, freeze-frame and slow and fast motion. Maximum time to scan the disk and select frames is less than three seconds, so branching and picture selection is extremely versatile.

The usefulness of the videodisk as a teaching tool came into its own as a result of being interfaced with the microcomputer (Fig. 2). As I will demonstrate today, one can now create a complete lesson, with demonstrations picked from videodisks, and store it on floppy disks. The computer program guides and controls the videodisk player through the sequence of frames and movies selected for the program. I would like to demonstrate this process by using our system to explain an idea in physics.

The idea is Einstein's Principle of Equivalence. Einstein was a man of fantastic insight into nature, and he had an imagination which propelled him into the forefront of scientific thought. His theories are famous both for their beauty and clarity-and he is renowned for possessing the creativity which generated them. What Einstein had to imagine, we can now demonstrate directly, using the medium of video technology!

One of the most fundamental concepts in science is that of a reference frame. A reference frame is the space in which the mathematical description of a problem takes place. How one perceives a physical interaction depends on the reference frame chosen to express the problem.

The concept of centrifugal force is one which depends on one's reference frame. You will commonly hear physics teachers admonish their students that "there is no such thing as a centrifugal force." However, every occupant of a turning car has experienced the sensation of sliding to the outside of a curve and being "pushed" against the door of the car.

Was there a force acting from inside the car to push one against the door, the so-called centrifugal force? Absolutely not. That was only a perception from the point of view of an observer in the reference frame of the car. What actually happened is that the observer's body, or anything else in the car for that matter, was obeying the law of inertia and was attempting to travel in a straight line, in the reference frame of the road. The car was turning and following the road, but, since the occupants were trying to travel in a straight line, it was actually the car, following the curve, that was moving toward them and pushing them with it. There is no force inside the car pushing outward on the occupants.

What happens, and how one describes it, depends on the reference frame chosen. Now this can be confusing. The laws of physics shouldn't give different answers in different reference frames. The laws of physics and the description of the world should be independent of any particular reference frame. The reference frame cannot, in itself, produce fictitious or imaginary forces.

There is a class of reference frames in which the classical laws of physics are all valid. These are called inertial reference frames, and they are the ones where the law of inertia remains valid. In general, these reference frames are ones that are stationary, relative to the fixed stars in the universe, or are moving at a constant speed in a straight line relative to a fixed reference frame.

If I do an experiment here in the theater, I am doing the experiment in an inertial reference frame. When I throw this ball straight up, the ball comes straight down along the same path. If I were in a Boeing 747, at 33,000 feet and traveling along at 600 miles per hour, I could do the same experiment and get the same result. The motion of the reference frame, the airplane, would not affect the results of my experiment. The airplane, moving at a constant speed, is an inertial reference frame.

Actually, I don't have to be in a jet to demonstrate this process. As I walk along, I am moving, as in the jet, and you can see, as I throw the ball up, it travels along with me and lands back in my hand, just as if I were standing still. The fact that I was moving along at a constant speed did not change the result of the experiment.

The situation is very different, however, if I change my speed while moving along, throwing the ball. Changing my speed means I am accelerating, and accelerating frames of reference are not inertial frames. In the accelerated frame of reference I will draw a different conclusion from my experiment of throwing the ball. Now when I throw the ball straight up, it does not come straight down into my hand. The ball falls behind my hand in this experiment, because the reference frame, me, moves faster than the ball and moves ahead of the ball while it is in the air.

The fact that the laws of physics are only valid in specific reference frames or coordinate systems was unsettling to Albert Einstein, and he devoted much time and energy to formulating the basic laws of physics so that they could be expressed and understood in any arbitrary reference frame, accelerated or not. This search led him to the General Theory of Relativity and a new theory of gravitation. One of the thought experiments used by Einstein in reaching his conclusions is the source of my lecture title today.

Einstein imagined himself inside an elevator, far away from gravitational influences (Fig. 3). Nowadays, we would imagine ourselves in a spaceship somewhere in outer space. In such an elevator, or spaceship, at rest or in uniform motion relative to the distant stars, everything within the elevator would float freely. There would be no up or down. However, Einstein now asks us to imagine a rope attached to the elevator which is capable of pulling on the elevator and accelerating it. This is equivalent to firing rockets on the modern spaceship.

Now everything inside the ship behaves differently and a sensation, similar to gravity, would be experienced. The wall near the rocket motors would push up against any occupants and become the floor, while the opposite wall would become the ceiling. Occupants of the ship would be able to stand on the "floor" and even jump-as on earth. If the acceleration of the elevator, or spaceship, were exactly "g", the acceleration of a falling body on earth, the occupants would not be able to distinguish their position and could well be convinced they were at rest, in an elevator, on the surface of the earth.

The effect of acceleration would be equivalent to the effect of gravity on earth. Objects released from the hands of a passenger would "fall" to the floor and behave exactly as they would in a stationary elevator or the surface of the earth. The acceleration of the elevator, or rocket, due to the pull of the rope or thrust of the rocket motors, would create an effect inside the vehicle identical to gravity!

Einstein reasoned that a generation of people born and raised in the elevator, or spaceship, would believe themselves to be in an inertial system and would refer all laws of nature to their elevator. It would be natural for them to assume their elevator to be at rest, and their reference frame an inertial one. For them, objects would fall and move just as if they were on earth, experiencing the actual effects of gravity.

Einstein concluded that it would be impossible to distinguish the difference between the effects caused by the accelerating rocket and the effects caused by the force of gravity. Each point of view would yield the same results and could be equally valid. Observations made in a gravitational field and in an accelerated frame of reference are indistinguishable and the descriptions are equivalent. This fact is now known as Einstein's Principle of Equivalence and was demonstrated by the shuttle astronauts during an orbit adjustment which required a small rocket thrust.

Einstein incorporated this equivalence, or impossibility of distinguishing between gravitation and acceleration, in the foundation of his general theory of relativity. This equivalence would be relatively unimportant if applied only to the mechanical world, but Einstein went much farther! He reasoned that the principle applied to all phenomena, including electromagnetic radiation, or light, and that light would be deflected toward the "floor" of the accelerated spaceship and would also be attracted by the gravitation of massive bodies, like the sun or stars.

Einstein proposed this drastic departure from conventional thought in the early 1900s, and it led us to what is now known as Einstein's General Theory of Relativity which, in reality, is a new theory of space, time and gravity. Using a somewhat different idealized experiment with the accelerated elevator, he imagined a beam of light, like a laser beam, projected horizontally through a window on one side of the elevator. After a short time, the beam of light would reach the other side of the accelerating elevator, but the elevator moves upward during this time and the beam would strike a point not exactly opposite its point of entrance, but a little below. The occupant of the accelerating elevator, not knowing of its acceleration and thinking he is in a gravitational field, would conclude that the beam was bent by the action of the gravitational field!

An outside observer, knowing of the accelerated motion of the elevator, would understand that the beam was displaced as a result of the movement of the elevator during the time it took the beam to travel the width of the elevator, a normal expectation for one observing the accelerated elevator.

How does one resolve these two different points of view? In brief, the dilemma was resolved by Einstein in predicting the bending of light in gravitational fields. This bending is far too small to observe in the earth's gravitational field, but can be observed in starlight passing near huge masses, like the sun and stars. In 1911, Einstein predicted that starlight passing near the sun would be deflected by an angle of 1.75 seconds of arc. In 1919, at Los Angeles' Wilson Observatory, Einstein's theory was verified during a total eclipse of the sun, a practice which is now standard at virtually every solar eclipse.

Light is deflected near large masses due to the action of gravity. This is now fact. If we could place mirrors several hundred miles apart and shine a laser beam between them so that the beam would reflect back and forth, the beam would fall exactly the same distance between the mirrors as a ball would fall in the same time. That is, if I dropped a ball at the same instant I turned on a horizontal laser beam, the ball and the leading edge of the light beam would hit the floor at the same time!

Several months ago, I was having dinner with friends. Included in the group were several math teachers and, as expected, the discussion turned to math? and physics-oriented topics. We were talking about concepts that were common to both math and physics and, somehow, the discussion turned to parametric equations and their use. I mentioned the use of Lissajous figures and discovered that they were not familiar to everyone present. That leads me to today and this lecture. I now have an opportunity to demonstrate something which is both beautiful and useful in math, science and art.

Lissajous figures occur when two harmonic motions that are perpendicular to each other are combined. They were first demonstrated in 1855 by Jules Antoine Lissajous, a French physicist who used the figures to demonstrate the vibrations which produce sound waves. If I attach a pencil to the top end of a pendulum (Fig. 4) and allow the pendulum to oscillate, the pencil draws a straight line. If I now pull the paper at a constant velocity while the pencil oscillates, I generate the familiar sine or cosine graph which describes the location of an object, executing what is called simple harmonic motion. The same graph can be generated by moving a laser beam up and down with simple harmonic motion, while also moving the beam horizontally at a constant speed, or by causing the electron beam in an oscilloscope to oscillate up and down while also moving the beam horizontally (Fig. 5). These are all familiar examples of sinusoidal motion.

The exciting Lissajous figures occur when these sinusoidal motions are combined at right angles. The simplest figures are generated from harmonic motions that have the same frequency and amplitude (Fig. 6). In this situation, one gets straight lines, ellipses or circles. This is easiest to demonstrate with the oscilloscope, where one has complete control of all these variables. Figure 4. The most primitive apparatus for demonstrating Lissajous figures is a pair of pendulums, coupled perpendicu- lar to each other and attached to a pen.

When the frequency of one of these signals is changed slightly, a completely different pattern results. The trace does not repeat itself, and a complex, but mathematically describable, figure results (Fig. 7). On occasion, devices like these coupled pendulums are seen at county fairs, where one of these beautiful figures can be purchased.

To me, the fascinating thing about these figures is their artistic appeal. If you travel to the Griffith Observatory in Los Angeles to see a laser light show, you are really seeing Lissajous figures, generated by several lasers, and controlled by an operator to change according to the beat of different kinds of music. The same sort of entertaining display was a highlight of Expo '86 in Vancouver, British Columbia, where lasers generated Lissajous figures that were displayed on smoke generated by fireworks. The commercial operators of laser light shows have developed sophisticated techniques for generating the Lissajous figures. They are computer-controlled and are capable of even generating line drawings.

I spent a considerable amount of time, along with Pat Therien, the Physics Department's lab technician, trying to duplicate the commercial systems, and I must admit that I failed in this venture. The best I could do was to generate lines, circles and ellipses, using mirrors attached to tuning forks (Fig. 8), much the same as used by Lissajous more than 150 years ago. Even so, they are still fun to watch.

My next example of the use of technological advances in the teaching of science has its roots in a very practical human need, breathing. Modern technology has made oxygen cheap and readily available. The most modern way that it is stored and delivered is in its liquid state, in cryogenic containers. The process of getting liquid oxygen involves cooling normal air, like the air in this room, until it turns into a liquid.

Since air contains both oxygen and nitrogen, a useful byproduct of oxygen production is an even colder liquid, nitrogen, which is used extensively in scientific research, where cold temperatures are required. It is cheap and easy to obtain, which allows a small school, like Santa Barbara City College, to demonstrate its properties.

One of the most fascinating topics in physics is the behavior of matter as it changes temperature. Water is common to all of us. We take for granted its behavior and it is natural for us to see it in each of its three phases on an everyday basis. That is, water occurs naturally as a solid in the form of ice, as a liquid in the form of drinking water, and as a gas in the form of vapor or steam. What we often don't realize is that almost all matter exists in one of these common phases or forms at some temperature.

What is interesting about this is our perception of temperature as it relates to the gaseous state. For humans, if something is steaming, very hot and dangerous, and we tend to think that, indeed, it must be hot. This is not the case for all materials. It is all relative and some materials that are steaming, like boiling lead or iron, are extremely hot, while other materials can be steaming and be very cold.

For example, in this container I have nitrogen in its liquid phase, and, as you can see, it is steaming! It is not hot, however, by human standards. In fact, it is 195 degrees below zero on the centigrade scale, and that is 78 degrees above absolute zero, the coldest temperature attainable. At this temperature, the heat from the room is all that is needed to keep the liquid boiling. As far as the liquid nitrogen is concerned, it is sitting on a hot stove and is boiling, just like a pot of water would be boiling on a burner in your kitchen. What is fun to think about is the fact that boiling liquid nitrogen occurs at a temperature far below the temperature that we humans think of as extremely cold. Compared to the temperature of liquid nitrogen, the 70 degrees below zero temperature of an Alaskan winter is hot, and liquid nitrogen would boil at that temperature, just as it does here.

Another interesting property of liquid nitrogen is that it is colder than liquid oxygen. If we were to put a roomful of common air into one of the modern refrigerators used to liquify air, we would find that, as the air cooled, the water vapor in the air would condense first. Then, as we continued to cool, carbon dioxide would condense and, just a little before the nitrogen would turn to liquid (about 12 degrees before), the oxygen would condense.

This is fun to watch, and I can demonstrate the process by filling this common balloon with air and placing it into my vat of boiling nitrogen. The nitrogen will cool the air, just as a refrigerator would. First, we see that, as the air cools, the pressure in the balloon drops as the molecules slow down. After a bit, the balloon is completely collapsed and, inside, we see a glob of liquid oxygen and nitrogen. If I hold the balloon out in the heat of the room, the liquid turns back into a gas and its pressure increases until the balloon returns to its original full state.

It's about this time in a lecture that one gets a very dry throat and a refreshing drink is in order. This glass of liquid nitrogen looks like it will do the job. Aaah, delightful! About as cool a drink as one can imagine, even though it is boiling! Actually, this is just another demonstration of relative hotness and coldness. What we humans perceive as cold is only relative. To the liquid nitrogen, my mouth is white hot. To my mouth, the liquid nitrogen is unbelievably cold, yet my mouth isn't frozen or damaged. I can do this only because my mouth is so hot, compared to the liquid nitrogen that the heat from my mouth instantly vaporizes. The nitrogen, in contact with my mouth, forms an insulating barrier of nitrogen gas. As long as I don't attempt to hold the liquid in my mouth too long-so that my mouth cools down, I can safely be in contact with it.

Physically, the same process occurs when you test a hot iron with a wet finger. You hear it sizzle, but feel no pain, since the hot iron vaporizes the moisture and creates an insulating gas barrier between finger and iron, which protects you. The skidding and sliding of a drop of water on a hot frying pan is caused by the same process. The hot pan vaporizes some of the water droplet, forming a layer of water vapor that the rest of the droplet rides around on.

There are numerous other fascinating tricks that one can do with liquid nitrogen. I'll demonstrate a couple.

A common tennis ball dropped into liquid nitrogen will freeze so hard and the rubber will become so brittle that it will shatter like glass when dropped.

A piece of lead sheeting, which is soft and pliable at room temperature, will change to stiff and solid, like steel, and will ring like steel when you strike it.

A lovely rose, when cooled to liquid nitrogen temperatures, will shatter like glass.

It's getting close to the time when I must bring this lecture to a close, but, before I do that, I have to satisfy a request from my son to do one of his favorite demonstrations.

When we demonstrate conservation of momentum and how rockets work we are able to use a modern carbon dioxide fire extinguisher as an exciting aid. You've all seen one and have probably used one, but it is unlikely that you have removed the spreader nozzle so that the full pressure of the CO2 tank is available to eject carbon dioxide from the hose (Fig. 9). The pressure of the gas is like that of a filled scuba tank, about 2,000 p.s.i. When it is allowed to blow out of the hose at full pressure, it is just like the hot gas being spewed from a rocket engine. The molecules of carbon dioxide stream out in one direction at very high speed. When they do this, they push on the tank. The molecules go one way and the tank goes the other, an example of Newton's Law of action and reaction.

I've had a wonderful time here today, sharing with you. I am truly honored to have been selected to give this annual lecture and I am delighted that so many of you chose to spend some time with me.

I would like to complete this lecture by sharing several ideas and feelings-and a little personal philosophy.

Being a teacher has provided a full and rewarding life for me. It has been a life of giving, taking, learning and sharing. I have had a chance to do things and think things with a great deal of personal freedom. I have learned so much from my students and from my colleagues. An idea has grown in me over the years that has guided me and my interaction with other people. That idea starts from the modern, scientific theory of the origin of the universe. If you read of this theory, you will find that scientists have reached back in time and traced the growth of our expanding universe back to what was a single cataclysmic explosion referred to as the "Big Bang." At this instant of time, all the matter in the universe, as we know it, was created and started on its present journey.

All the atoms and components of matter, as we find it now, started at that single moment. That means that the atoms that make up your body, my body and all the bodies in the universe had a common origin. We are all truly connected. We are from the same source. Not only that, these same atoms are being continuously recycled. We share the same air and the atoms of our predecessors. There are enough atoms in a single human body that there is a finite probability that your body and my body contain some of the very atoms that were once in the bodies of Newton, Galileo, or, even, Einstein.

The point is, we are all connected. In a real sense, we are of the same family. We are all leaves of the same great tree and what we do as individuals affects each member of the family-or leaf of the tree. If we hurt someone else, we hurt ourselves, and, if we hurt ourselves, we hurt someone else.

Because of this idea, I have found considerable peace in my life and in my dealings with other human beings. We are all truly connected, each of us having the same value. We are all in the process of growth and development. We each play different roles, but we are all of the same family, regardless of our origin or place of birth. My students are as important as I am. I am as important as my students. What I do well, someone else cannot do well-but that someone does something of equal importance, better than I do. We learn from each other and we share with each other. It is not important who is better; it is only important what is better. It is not important who is right; it is only important what is right.

As I grow older and reap the benefits of my life experiences, I have come to believe in the reality of universal knowledge and its impact on human behavior. I feel that mankind is in the most difficult and turbulent of times. I fear for the future of my children and their children to come. It is my hope and my prayer that you, me and mankind, collectively, can develop a universal consciousness of peace.

It is my firm belief that the prospects of peace on earth and a life without war and human suffering depends on how soon we, as individuals, consciously decide to think and act positively in our relationships with our fellow man. We are family. Let's start the process now.