In the mid-1980s I was teaching science in its social context as a new faculty member at a non-traditional undergraduate college. I began an ecology course with a brief review of our place in space before I asked students to map their geographical positions and origins. One student, "K," did not come back to earth with the rest of us, but remained off in her own thoughts. Some minutes later she raised her hand: "I always knew the sun, not the earth, was the center of the solar system, but do you mean to say..." K paused, then continued. "I'd never thought about the sun not being the center of the universe." From K's tone, it was clear that she was not simply rehearsing a new piece of knowledge. She was also observing that she had not thought about the issue but now she saw as obvious that the universe was not sun-centered. What other retrospectively obvious questions had she not been asking? What other reconceptualizations might follow? These questions pointed her along the path I hoped my students would take as critical thinkers-grappling with issues they had not been aware they faced, generating questions beyond those I had presented, becoming open to reconceptualization, and accepting that their teacher should not be at the center of their learning.
Since childhood star gazing in rural Australia I had known about the sun's marginal place in the Milky Way so I felt some superiority when K admitted that she had not realized this. To my chagrin, I subsequently discovered my own retrospectively obvious question about our place in space. I was reading Sally Ride's 1986 book on the space shuttle to my child, when I came to her description of astronauts regaining weight as they descended. The idea conveyed was that weightlessness was a result of distance from the earth. Yet the space shuttle orbits only 300 kilometers up where the earth's gravity is still 90% of its strength down on the surface. So I started thinking about how to explain weightlessness correctly in a children's book. Try this-think of swinging an object around on the end of a piece of string. To make it go faster, you have to pull harder; if you do not hold on tight, the object flies off into the neighbor's yard. Astronauts travel around the earth fast-at 7.5 kilometers per second. They feel weightless because all of the earth's gravitational attraction on them goes to keep them from flying off into space. The earth's pull on the astronauts is like your pulling on the string-but, while you may let go, gravity never stops acting. When the space shuttle slows down on its return to earth, less of gravity's force goes to keeping the astronauts circling the earth and what is left over is experienced as weight regained.
After rehearsing this explanation a few times, another kind of weightlessness occurred to me. The sun's gravitational attraction is keeping me circling around it-at 30 kilometers/second I figured out. On the earth I feel weightless with respect to the sun's gravity, but that force is acting nevertheless. I had never thought about this; I had considered myself a passenger on the earth, which the sun's gravity was keeping in orbit around it. I then realized that I am also zooming around the Milky Way galaxy, not as a passenger in the solar system, which the galaxy's gravitational attraction was keeping in orbit around it, but because the galaxy's gravity is keeping me orbiting around its center. It made me feel woozy to think of the sun and the rest of the galaxy "paying attention to me" all the time, keeping me circling at enormous speed through space-at over 200 kilometers/second, I soon learned. I wondered if every molecule in the galaxy was attracting every molecule of my body every moment. Was there some other way to think about gravity? Perhaps a further radical reconceptualization awaited me, possibly involving wooziness-inducing Einsteinian concepts such as curved space-time.
Since childhood star gazing in rural Australia I had known about the sun's marginal place in the Milky Way so I felt some superiority when K admitted that she had not realized this. To my chagrin, I subsequently discovered my own retrospectively obvious question about our place in space. I was reading Sally Ride's 1986 book on the space shuttle to my child, when I came to her description of astronauts regaining weight as they descended. The idea conveyed was that weightlessness was a result of distance from the earth. Yet the space shuttle orbits only 300 kilometers up where the earth's gravity is still 90% of its strength down on the surface. So I started thinking about how to explain weightlessness correctly in a children's book. Try this-think of swinging an object around on the end of a piece of string. To make it go faster, you have to pull harder; if you do not hold on tight, the object flies off into the neighbor's yard. Astronauts travel around the earth fast-at 7.5 kilometers per second. They feel weightless because all of the earth's gravitational attraction on them goes to keep them from flying off into space. The earth's pull on the astronauts is like your pulling on the string-but, while you may let go, gravity never stops acting. When the space shuttle slows down on its return to earth, less of gravity's force goes to keeping the astronauts circling the earth and what is left over is experienced as weight regained.
After rehearsing this explanation a few times, another kind of weightlessness occurred to me. The sun's gravitational attraction is keeping me circling around it-at 30 kilometers/second I figured out. On the earth I feel weightless with respect to the sun's gravity, but that force is acting nevertheless. I had never thought about this; I had considered myself a passenger on the earth, which the sun's gravity was keeping in orbit around it. I then realized that I am also zooming around the Milky Way galaxy, not as a passenger in the solar system, which the galaxy's gravitational attraction was keeping in orbit around it, but because the galaxy's gravity is keeping me orbiting around its center. It made me feel woozy to think of the sun and the rest of the galaxy "paying attention to me" all the time, keeping me circling at enormous speed through space-at over 200 kilometers/second, I soon learned. I wondered if every molecule in the galaxy was attracting every molecule of my body every moment. Was there some other way to think about gravity? Perhaps a further radical reconceptualization awaited me, possibly involving wooziness-inducing Einsteinian concepts such as curved space-time.
The Authors:
Peter Taylor:
Peter Taylor is a Professor at the University of Massachusetts Boston where he directs the Graduate Program in Critical and Creative Thinking and the undergraduate Program on Science, Technology and
Values. His research and writing links innovation in teaching and interdisciplinary collaboration with studies of the complexity of environmental and health sciences in their social context. This combination is evident in his 2005 book, Unruly Complexity: Ecology, Interpretation, Engagement (University of Chicago Press).
Values. His research and writing links innovation in teaching and interdisciplinary collaboration with studies of the complexity of environmental and health sciences in their social context. This combination is evident in his 2005 book, Unruly Complexity: Ecology, Interpretation, Engagement (University of Chicago Press).
Jeremy Szteiter:
Jeremy Szteiter is a 2009 graduate of the Critical and Creative Thinking program and now serves as the Program's Assistant Coordinator. His work has centered around community-based and adult education and has involved managing, developing, and teaching programs to lifelong learners, with an emphasis on a learning process that involves the teaching of others what has been learned and
supporting the growth of individuals to become teachers of what they know.
No comments:
Post a Comment