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Few areas seem as far removed as physics and classical ballet. And yet on closer examination they have certain aspects in common. Both require unusual and ceaseless effort. Both rely on a formal language difficult to acquire. And both contain a beauty that is powerful and abstract. Nevertheless most physicists know little of the ballet, and surely ballet fans and professionals have had little or no contact with physics - until Ken Laws came along.
Kenneth Laws is a professor of physics who became interested in classical ballet to a degree that led him to study it, teach it and eventually research it in physical terms. He has done much work in bringing these unrelated fields together. He has written three books on the physics of dance, and given talks and presentations to those involved in physics as well as dance. He is currently engaged in research on jumps, using quantitative measurements to determine the forces exerted on and transmitted through the body, which bring it to rest on landing from a vertical jump. A talk with Professor Laws provides remarkable insight into the world of ballet from the point of view of one who has made an unusual mesh between these ostensibly unrelated fields.
Judy Kupferman's Interview with Prof. Ken Laws:
J: What caused you to become interested in ballet in the first place? You were already working as a physicist at the time, right?
KL: Yes. In 1976, I had been teaching at Dickinson College for 14 years when my daughter Virginia, age 5, decided she wanted to start ballet classes. My son Kevin, age 7, didn't want to be left out of something his little sister was into, so he started also. Then their father didn't want to be left out, so, at age 40, I started! We were in the same classes for a while, since there were no adult classes at the time. I was about twice as tall as the next tallest person in the class. But that experience turned my life upside down! Kevin quit after about a year and a half. Virginia retired, after a long and illustrious career, at the ripe old age of 13. Now, almost 30 years after we all began, I am the only one in the family continuing with ballet!
J: Ballet is surely very different than physics. Can you tell us what it was about it that appealed to you?
KL: Well, I've always been involved in music -- jazz, mostly -- and there's something about music that reaches deep into my soul. I've also appreciated the beauty of the human form and the way it moves when pushed to its limits, but had never been exposed to ballet before. I've also been intrigued with theatre. When all of these aspects of life came together, I fell for it!
J: So at first your interest was as an amateur? How did you get into teaching it?
KL: Yes, at first I just took classes and learned the basics along with the other students. My understanding came a little more quickly than it did for those youngsters with less intellectual maturity, but then I reached my limit sooner -- my bones and muscles had had too many birthdays by then! But the fact that I was a full sized male in an activity that is 90% female meant that I had opportunities I would not have had otherwise. Early in my career I played one of the suitor princes in "Sleeping Beauty," and participated in the famous Rose Adagio with a future member of the New York City Ballet, Deborah Wingert. That was an unbelievable thrill!
At my peak (around age 50) I was taking eight to ten classes a week. That would have been impossible had I been full-time employed, but by then I had reduced my teaching load (and salary) to around 2/3 time. That was possible because my wife was also teaching in the Physics Department.
A couple of years after starting classes I realized that a ballet studio is a physics laboratory! As I was asked to do certain movements, I realized that there were physical principles involved that, if understood, would make the movements more effective, or easier, or less inclined to result in injury. Some principles, such as the conditions for static equilibrium, or the conservation of angular momentum, apply to many of the positions and movements in dance.
One early experience was doing tendus to the side at the barre - that's a movement of one leg to the side, to pointed foot in contact with the floor, while holding the barre with the opposite hand. We were expected to move only the working leg, with a hand lightly on the barre, and be able to lift the working leg from the floor without toppling. I thought, "This is impossible! The center of mass moves to the side when the leg moves in that direction, and the area of support at the floor is no longer directly below it. So we would have to topple." Well when I looked around, all the kids in the class were doing it! They somehow had figured out that they could "cheat" in little ways that allowed them to appear to meet the challenge. I doubt that they were thinking about where their centers of mass were, or where the forces and torques might come from to maintain a balanced static equilibrium, but their bodies, by trial and error or instinct, had figured out what to do! And one of the lessons I learned was that much of dance is illusion. There are indeed physical constraints that dancers appear to defy, some dancers more effectively than others.
I began to see more and more physics in the movements, and could feel the way those principles worked in my own body. And I thought "Why isn't everyone using this understanding to make ballet easier, more direct, and more effective?" I found that nobody was using these principles, so I jumped in to try to find a niche in that void.
I discovered one interesting aspect of the mental capabilities of young people. Vocabulary, not the difficulty of understanding the logic, is the main reason they find both ballet and physics challenging. My daughter, early in her ballet years, came home from class one day in tears. "Daddy, Marcia kept telling me to make my palms face forward." As I wondered why that was upsetting, she finally blurted out "Daddy, what's a palm?"
On the other hand, another current member of the New York City Ballet was in a partnering class I was teaching many years ago when I was repeating a movement (the "whip turn") that we had performed and discussed in the previous class. When the girls were making the same mistake they were making before, I said "Hey! Why is moving the leg front to side important at the beginning of this movement?" Ashley replied "It's so you can store momentum in that leg while the partner is still exerting forces on your waist; you get more rotational momentum that way." I saw about 40 jaws drop in unison! She used her own words, but clearly understood the principle. She was 11 years old at the time!
Partnering classes are what I have taught the most, having started in 1986 in the Central PA Youth Ballet's Summer Ballet Program. Why partnering? It is because I consider ballet partnering just about the epitome of human existence. It is incredibly appealing to combine the beauty of human body movement with music and with the necessary marriage of two minds thinking about coordinating their movements in order to make a whole imagery greater than the sum of its two parts.
J: What spurred you into writing your first book? What's it about?
KL: I started writing articles about the movements that I found analyzable by straightforward applications of physics, and came to that fateful moment when I thought: "I have enough stuff to put in a book!" About a year and 21 rejections later, I found an editor willing to take a chance on this book. I owe an enormous debt of gratitude to Maribeth Payne and Schirmer Books for going out on a limb with "The Physics of Dance." The hardback (1984) and paperback (1986) sold a total of over 10,000 copies, which was a thrill to me!
J: Your recent book, Physics and the Art of Dance, sold over 2,000 copies as of last March. Can you tell us something about that?
KL: I felt that many of the explanations in the first book could be improved, some new features added, and some of the material from the second book (Physics, Dance, and the Pas de Deux) incorporated with less emphasis on the pas de deux. One of the added features that I really like, is the collection of puzzlers that appear at the beginning of every chapter. Those puzzlers are intended to draw the reader into the substance of the book by describing an anecdotal situation that can only be solved by the principles found somewhere in that chapter. Of course the photographs by Martha Swope, a combination of those found in the first two books plus many new ones from her collection, are an outstanding feature of the newest book. Like the first two books, the latest one is aimed at people with some knowledge of dance and little physics. But there is enough physical and mathematical rigor (mostly in the extensive appendices), to make it interesting for physics-oriented readers.
J: Your latest research project involves jumps. Tell me something about that. I gather you and your students have been collecting data and trying to find the total tension force in the Achilles tendon upon landing from a vertical jump.
KL: That's right. We can find the magnitude of the maximum force as a function of variables including whether the heel has contacted the floor when the force is maximum, what effect the degree of turnout has, whether the dancer has primarily modern or ballet experience,his age, gender, years of training, and such.
Then we have an orthopedist who is interested enough in the project he's working with us. He and I will primarily be working on the effect of turnout on creating a dangerous magnitude of lateral force on the patella, which often gives rise to dislocated kneecaps. For that, we're going to be trying to use indirect means to find that force. We determine the deceleration of the center of mass of the body above the knees to determine the total vertical force acting on that part of the body at the knees. Then, from the location of that center of mass, we can determine the torque in the knee joint that provides for that vertical force. Then measurements of the knee when in the decelerating landing position will allow us to measure the "Q-angle" between the lines of action of the patellar tendon and the quadriceps tendon, which then will give us the lateral force on the patella! Simple, right?! It will be a miracle if all of that works with reasonable accuracy! But it's fun stuff!
J: Along with your work in ballet I understand you've continued teaching physics. Have you found any conflict or problems in jumping from one world to the other? And do you find in any way that your work in one affected or influenced your work in the other?
KL: I've found other "niches" in the world of science teaching. I taught an introductory course in meteorology for almost 30 years, and a course in electronics for almost as long. Did they become drudgery? No! The meteorology course quickly evolved to become one with no fixed syllabus; the ordering of subject matter was driven totally by current weather. So the course was never the same twice. And the Electronics course always involved student projects that were often very creative and interesting.
I also taught a freshman seminar for several years on "Science and the Performing Arts," dealing with the physics of dance and musical acoustics. That was always an enjoyable experience, in that it combined my three loves -- physics, music, and dance, and that it attracted students who were interested in the performing arts and were not afraid of science.
Besides teaching those and other courses, I have supervised research in everything from physics of dance and musical acoustics to light transmission through a forest canopy! I continue to supervise physics student research projects and contribute to the College and the Department in various other ways.
J: Sometimes people in the sciences tend to look down on those in the arts, whereas people from the humanities find science boring or hard. What kind of reactions have you gotten from people in the physics world about your other occupation? And from the ballet about physics?
KL: Trying to cross borders is always a challenge. I have often heard the comment from ballet teachers, "Don't think about it, just do it!" Or "You remove the art if you analyze it too much." Or "This is an art, not a science. We think subjectively and in images, rather than in cold, hard, mathematical facts and formulas."
But those comments come mostly from the older tradition-bound practitioners of classical ballet. Young people are the ones who crave explanations for why they do things the way they do. They are no longer satisfied with answers like "Do that this way because it's the right way!" Or "because I said so." Or "because that's the way it's been done for 300 years!"
These dancers who crave physically valid reasons for performing movements the way they do may not realize it, but they have the potential to follow science as an interest if not a career. They have the advantage of exposure to physics before they have learned from the adult world that science is to be feared. The common barriers have not risen yet in their minds!
When I first started speaking on "The Physics of Dance," I would ask the audience how many were involved with science, and how many involved in dance. Then how many consider themselves involved in both? Twenty-five years ago, the third category was empty. Now perhaps a quarter of a general audience will respond that they are involved in both! I consider that a triumph. Dancers realize that understanding the physics can genuinely help their technical facility; science folks enjoy seeing physics applied to the human body moving in impressive ways that most of us can enjoy only vicariously. But we all have bodies, so there is an inherent curiosity.
I have found that physicists enjoy this activity because it's a relief from the more common physics research that today deals mostly with abstract ideas about invisible subjects. It is a joy to encounter the insights about human body movement that can come quickly when the physics principles behind those movements are understood.
J: Ken, this has really been a pleasure. Thank you very much for your time.
KL: It's been a pleasure for me as well!
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