Dr. Karl Trappe, a professor at the University of Texas at Austin, is lying down in front of a group of students. His assistant places a board with 169 nails against his chest. Then the assistant piles 80 pounds of concrete blocks on top of the board and hits it with a sledge hammer.
Dr. Trappe emerges from this ordeal unscathed.
A miracle? A trick? Neither. It's science; it's the Circus of Physics. Dr. Trappe uses ''tricks'' with balloons, bicycle wheels, marshmallows, soda fountain stools, building blocks, to spur young people's imagination - and improve their understanding of basic concepts in physics.
Dr. Trappe explains the scientific bases of why the 169 nails didn't stab him.
''If you have that many points,'' he tells the young scientists, ''you invoke the 'distribution function,' that is, you distribute the weight of the 80 pounds of concrete blocks, and the slam of the sledgehammer and the nails don't hurt.''
He explains also that the mass of the concrete blocks buffers the blow from the sledgehammer (''the bigger the mass, the less acceleration'').
Twenty-five years ago when Sputnik shook the educational world and an impetus toward scientific and mathematical education was born, Karl Trappe was in the fifth grade. His interest in science grew, particularly in physics, and in 1972 he was awarded the doctor of philosophy degree in physics from the University of Texas (Austin). He immediately went to work for UT as director fo the Physics Lecture Demonstration Center.
''Physics is a demonstration science,'' Dr. Trappe says. ''At the same time, the university is a research institution, with a faculty committed to spending time in research. Thus, teachers of undergraduates have little time to prepare the demonstrations so necessary to illustrate the concepts of physics. The lecture demonstration center provides this teaching support.''
Dr. Trappe got into the circus business by way of the film business - showing scientific films on the campus at night. Then he held several physics circuses to provide undergraduates with insights into physics phenomena. The first audience was mostly physics majors; then they began to bring their dates. ''It snowballed; students came from all over the campus. Then came the general public ,'' Dr. Trappe recalls.
In recent months the interest in the physics circuses has gone beyond the campus to elementary schools in the area, with parents and teachers concerned that their children aren't receiving the scientific education the times demand.
To Dr. Trappe, remembering Sputnik, it's deja vu.
The audiences for the Circus of Physics now number about 500 each.
Last summer Dr. Trappe had solid bookings for his circuses with special guests at the university - for the Texas Energy Science Symposium, the conference for high school counselors, and the Junior Honors Colloquium (for gifted high school juniors).
He believes he is restoring curiosity to young people and introducing them to physics in their world. He says many common tools of physics aren't available on a day-to-day basis anymore.
''Remember the fun of soda fountain stools or piano stools?'' he asked. ''We got on those stools and whirled around and around, pushing our arms in and out to go faster or to slow down. But when have you seen such a piano stool recently?''