|
|
     |
|
|
|
by Rachel Covault
In even most intriguing physics lectures, the mind tends to wander. The ears filter out the sound of the professor's voice as if it were no more than background noise. The eyes drift from the equation-riddled blackboard and across the backs of the heads in the front row to settle on the unusually wide door in the front of the room.
It is through this door, with its small porthole window, that the professor makes his entrance before class. Occasionally it is propped open with a chipped hunk of steel, allowing a few students who sit at just the right angle get a peek into a tantalizingly mysterious back room.
What could possibly be kept behind that door? A five-star teacher's lounge? A top-secret laboratory for highly controversial experiments, complete with Frankenstein's monster?
Then, as class is dismissed, a shadow appears in the doorway. It moves into the classroom.
It is the Demo Guy, Brian Andersson, and the enigmatic back room--formally known as the George D. Freier Lecture Demonstration Facility--is his domain.
The facility--3,500 square feet of space hidden in the center of the Tate Laboratory of Physics--is dedicated to building, storing, and repairing the contraptions teachers use to prove the laws of physics during lectures. The three-room complex opens onto the building's five largest lecture halls, providing easy access to large courses.
Near one of those doors sit two rows of carts, waiting to transport requested demonstrations into the lecture halls.
Much of the space is taken up by drawers, counters, and pegs on the walls that at first glance seem cluttered with strange antiques, children's toys, and random spare parts. However, an underlying organization can be discerned, and each crazy contraption has a purpose.
There are shelves for mechanics demonstrations like low-friction carts and pulley systems; cabinets dedicated to electricity and magnetism demonstrations like the Van de Graf towers that make students' hair stand on end; and tables for optics demonstrations, where lasers and funhouse-style mirrors are kept.
These gadgets and contraptions are an important part of physics education, says Andersson. Visual aids, especially those that move or make noise, awaken interest, pique curiosity, and make potentially tedious lessons memorable. Laws of physics that look impossibly complicated when expressed in numbers and Greek letters gain more meaning when a real-life application of those laws can be seen, heard, smelled, or felt.
Within easiest reach are the "PIRA 200," the 200 demonstrations deemed essential by the Physics Instructional Resource Association (PIRA). They are relatively inexpensive, easy to make, and clearly exhibit some fundamental principle.
Among them is "Monkey and Hunter," in whicha gun is fired at a stuffed monkey that is dropped from the ceiling at the moment the trigger is pulled. The projectile hits its target anyway, showing how gravity pulls equally on both the projectile and the stuffed toy.
"Bed of Nails" displays the effect of distributing weight (specifically, the weight of a physics professor) over a large area (a bed of nails); this effect is contrasted with the result of placing that weight on a small area, like the tip of just one nail.
To ensure that every student in a large lecture hall can see the demonstrations, "bigger is better," says Andersson. For instance, the strength of vacuums can be introduced by pumping the air from inside an O-ring sandwiched by two Plexiglas plates, attaching one plate to a cable hung from the ceiling, and swinging across the room by a handle on the other plate.
When a demo is too difficult to enlarge or too dangerous to angle toward the audience, video and computer simulations offer an alternative, he says.
Unfortunately, bigger does not always translate to safer. One infamous example is the "Nose Basher," which involves a bowling ball suspended from the ceiling. The professor is supposed to pull the ball away from its rest position until it reaches nose height, then let go. The ball should swing back and forth, stopping just short of the professor's nose upon its return.
According to Andersson, there are many stories of professors who unknowingly leaned forward into the ball's path or gave it a push instead of simply releasing it. When this happens, the ball makes contact, often with enough force to break a nose or, as in one case, crack the blackboard behind a professor who dodged out of the way.
The task of making the demonstrations and their components safe also falls on Andersson, the building's research safety officer. A few weak sources of radiation are kept in a shielded case, but Andersson is eliminating demonstrations that include toxic compounds like mercury and lead as he sifts through storage cabinets stacked by his predecessors with unidentifiable devices coated with a fuzzy layer of dust.
In the deepest reaches of the demo room, overseen by a rickety human skeleton, shelves of contraptions from past eras wait. Most are either broken beyond repair or obsolete, and many have no immediately recognizable purpose. Andersson has posted photos of some of the most puzzling ones on the web in the hope that someone can help identify their purpose.
Andersson is only the latest in a lineage of dedicated Demo Guys. George Freier, for whom the demonstration facility was named, lived by the motto "You should never put something in a textbook that you can't demonstrate." Accordingly, the textbook he wrote, University Physics: Experiment and Theory, was filled with examples, illustrations, and demos.
He later supplied other textbooks with the same material in the form of A Demonstration Handbook for Physics, a 211-page list of every demo available at the University facility, complete with hand-drawn illustrations, brief discussions, and set-up instructions. This first effort at organizing the University's demonstrations helped instructors find out what was available to them.
"There was [no organization system] before George," says Professor Emeritus Hans Courant, who led the effort to have the facility renamed in Frier's honor.
Phil Johnson, another influential Demo Guy, helped keep the University's facility the top in the nation by acquiring equipment and devising new and better demonstrations. One of his biggest accomplishments was the creation of a classification scheme for demonstrations that took him and two colleagues five days to construct. Today, that classification system is the accepted standard of PIRA.
The University boasts one of the largest collections of physics demonstrations anywhere. Although the University of Maryland has surpassed it in the number of available demonstrations, many of its demos are variations on the same theme, says Andersson, who focuses on demo quality instead of quantity.
His goal is summarized in another demo room motto: "The unofficial motto of the demo room is to break up the monotony of lectures."
