Ralph Gibson: Scientific sorcerer

Grinning like Merlin the wizard, Ralph Gibson quotes the stage magician's chant: "Nothing hidden, both my hands are in plain view, what you see is what there is."

It is Gibson's job to give Dartmouth physics students "demonstrations they'll never forget" - to make concrete and tangible the theories and principles propounded in physics classes. The slight, dark-haired man of 39 holds sway over a cluster of small rooms between the two physics department lecture rooms on the first floor of Wilder Hall, where he prepares the demonstrations the professors ask for. All of that comes under the official title of Manager of Lecture-Demonstrations, Department of Physics.

Perhaps his most spectacular display is the mousetrap/Ping-Pong ball extravaganza, though Gibson decries the experiment as not being either scientifically accurate or realistic.

But the recipe is simple: Take 180 mousetraps and an equal number of Ping-Pong balls. Arrange the traps in a square, with all traps touching. Set each trap and carefully place a Ping-Pong ball on each, balancing it between the bait hook and the rectangular metal bail. "It's hard to describe just where you put the Ping-Pong ball," Gibson says, "but you'll find the right place. It's the only place it will stay put."

Now drop a Ping-Pong ball anywhere in the assemblage of traps. And wham, zap, wow, you get a mad commotion of leaping balls, jumping traps, and - probably - screaming observers. It all happens so fast you can't really see the sequence of events, Gibson notes, but he has a videotape of the demonstration which he runs in slow motion. "You can see the disturbance propagate," he explains.

The mousetrap/Ping-Pong ball performance is an approximate demonstration of what happens in a nuclear chain reaction, though Gibson warns that the experiment is mostly for show. "It is fun to see and it does make an impression on the audience" he says.

Less spectacular than the mousetraps and Ping-Pong balls but more bewildering is Gibson's version of the Kelvin generator, a device that has doubtless baffled many budding Dartmouth physicists. "We sometimes set it up in the hall, let it run, and let them try to figure out how it works," he says.

It looks simple enough at first glance. A glass jug of water is inverted at the top of a rack of parallel sets of tubes, wires, and cylinders made of perforated metal. The water descends through a series of plastic tubes and on through the perforated cylinders to two catch-pails at the bottom. Gibson turns the valve on the jug, releasing the water, and for a moment or two the water does nothing more than what you'd expect - it runs into the first set of cylinders, dribbles on into the second set, and winds up in the little pails.

However, Gibson is not trying to convince the spectator that water runs downhill. Suddenly, something's happening droplets of the water are leaping out in a,, fine circular spray between the top and bottom cylinders on both sides. At the same time, two telephone bells rigged side-by-side near the center of the apparatus begin chiming as a thumbtack suspended from a string swings back and forth between them, touching each bell lightly as it oscillates.

What's causing all this action? Gibson explains: "A drop of water carries a slight electrical charge, either positive or negative. When the first drop hits the first cylinder, the drop charges that cylinder, either positive or negative."

The four cylinders, two to a side, are wired crossways - the top cylinder on the right to the bottom cylinder on the left, and vice versa. If the righthand top cylinder happens to pick up a positive charge from its initial drop of water, the wire carries that positive charge to the lefthand bottom cylinder, while the top cylinder on the left becomes negatively charged. As the water continues to run, the amount of electricity in the cylinders builds. The negative and positive charges are transmitted to the bells, which are wired to the cylinders, and the tack begins to swing, first attracted and then repelled as it picks up negative and positive charges from the bells.

Students are not the only ones enthralled by Gibson's ability to build such displays.

"He puts on a good show for the visiting parents of the freshmen," says John Walsh, physics professor. Gibson's creativity has added a great deal to the department, notes Walsh.

Such highly graphic exhibitions of basic principles of physics are a tradition at Dartmouth, Walsh says. A former long-time physics professor, the late Francis Sears, often piqued his students' interests with his demonstrations. "Sears would have 200 students at his lectures," Walsh says. "After he retired, the rest of us just sort of struggled along with demonstrations the best way we could until Ralph came along."

Many colleges and universities have dispensed with the tradition of physics demonstrations such as the Kelvin generator because there is no one in the department able to build the necessary apparatus. "There are few talents like Ralph's," Walsh says.

Demonstrations like the Kelvin generator or the mousetrap/Ping-Pong ball chain reaction take more than just showmanship. It requires a knack at putting things together, engineering skill, and a thorough knowledge of the many facets of the physics field - the science that deals with matter and energy and their interactions in the fields of mechanics, acoustics, optics, heat, electricity, magnetism, radiation, atomic structure, and nuclear phenomena.

Gibson, a University of Vermont graduate who got his master's in physics at Dartmouth, originally intended to be a mechanical engineer. But he had taken physics at UVM as a required subject, and he became caught up in it, eventually getting his master's degree in plasma physics.

Plasma, in the physics sense, has nothing to do with blood but is a term for ionized gas. It is a huge field in which physicists have been working for the past 20 or 30 years. One of the possible benefits of their research might be a new energy source, fusion power. Unlike fission power, derived from splitting the hydrogen atom (as in the original atomic bomb or in nuclear generating plants), fusion would produce a clean, almost limitless power, Gibson says. "The hydrogen atoms are squeezed together to produce helium. It is extremely difficult to do, but it would give us an energy source that would be virtually unlimited. No radioactive waste, no disposal problem but if fusion is ever done, the technology would be infinitely more complex than the present-day fission reactors."

He admits that a description of fusion power sounds much like the glowing forecasts for nuclear power 40 years ago, when the first nuclear generators were being built. But he points out that there is a major difference between fusion and fission. Fusion power produces no radioactivity and no waste - only helium, an inert, non-flammable gas. "They use it to fill party balloons," Gibson says by way of explaining the byproduct's innocuousness.

Gibson's niche in life, however, proved to be not fusion research but the physics department job he has held for the past 14 years. "Whatever the faculty asks for in the way of physics demonstrations, I set up for them. If we don't have what I need, I buy it or make it."

He enjoys putting together things like the Kelvin generator or the mousetrap demonstration. It challenges his ingenuity. Gibson is a meticulous, skilled craftsman whose experiments demonstrate his engineering skills as well as his knowledge of physics.

As he puts away his mousetraps and Ping-Pong balls, Gibson smiles. "I bought the traps at Dan and Whit's, the store in Norwich," he says. "Can you imagine what they must have thought when I came in and ordered 200 mousetraps and told them to charge it to Dartmouth College?"

Ralph Gibson has perplexed many a physics student with his demonstrations of scientificprinciples. Here he shows off one of the more mystifying pieces of apparatus he's constructed— a Kelvin generator.

Janice Aitken, a former staff reporter for The Valley News, is now a free-lance writer basedin South Royalton, Vt.