One important factor that emerged was that the visitor should be able to relate the exhibits as much as possible to real life. Several years ago, when I was preparing the Royal Institution Christmas Lectures, I wanted to have a demonstration involving, ingeniously as I thought, a loo-roll tube and ping-pong balls. The idea was to show how brain cells generated a voltage, and how this voltage could be changed so that the cell discharged a brief electrical signal. The loo roll would serve as one of the tiny pores that perforate the outer wall of brain cells, through which charged atoms, "ions", of sodium and potassium can traffic back and forth. The ensuing change in the distribution of the charge carried by the ions causes a change in the existing potential difference, the voltage in the brain cell. My idea was that the colour-coded ping-pong balls could be used to reveal the different conditions under which such traffic in and out of the brain cell took place. Hence people would be able to understand the essence of the electrical signal that enables communication to be initiated from one brain cell to the next, and so have a grasp of brain function.
"No; too boring," said the producer, dismissing what is, incidentally, my life's work. "People must be able to relate to what you are showing." I have remembered his wise words ever since. After all, who cares about voltage changes, ions, and the vagaries of those ions unless it is placed in the context, say, of how anaesthetics might work. Paradoxically, however, it is also important for people to have a sense of awe. The South American arrowhead, dipped in curare and thus capable of inducing almost instant paralysis, the true-to-life dinosaur model, and the rocket engine, are all exciting precisely because they are not seen every day at home. But, then again, such objects, unlike my loo-roll model, are easy to set against established experiences, albeit fantasy ones.
However, one of the biggest problems that was raised by the professionals, concerned how to explain seemingly complex concepts. Again, there had been a further trick up the sleeve of the producer of the Christmas Lectures - this time it was to find a good metaphor. For example, the constant, steady voltage generated in all brain cells all the time they are not sending signals, is a process that, nonetheless, depends on a ready supply of energy. By contrast, the electrical signal that lasts for a 1,000th of a second when sodium and potassium ions flow into and out of the cell, paradoxically, requires no energy. A hard concept: how much simpler to say that the situation resembles an archer shooting with a bow. The "resting" potential that actually requires energy, is comparable to the archer pulling taught on the bow string, while the dynamic event, where no energy is required, is analogous to the arrow being unleashed.
The secret is to find a metaphor that has nothing in common whatsoever with what it is describing, save the one critical, vivid similarity. Hence computers, that have now been so frequently equated with the brain, are poor metaphors compared to, say, spaghetti, for describing the seemingly jumbled, intertwining connections between brain cells. Some detail and scientific precision will be lost by homing in on a single, powerful image: but surely if the basic message can be conveyed, the finer tuning can follow once the person is sufficiently hooked to pursue the subject.
How can museums help in dangling that initial carrot? One of the greatest thrills of science is the practical aspect, the excitement that comes from designing an experiment to answer a question and obtaining an answer, often one that no-one would have predicted. In the familiar media of television, books and even CD-ROM, the otherwise scientifically curious might simply feel confronted with a fact or an object rather as the Israelites were by Moses with his tablets. If interactive exhibits could be developed where the outcome was uncertain, then the basic thrill of finding something out for oneself might touch an otherwise hardened heart.
Museums are the only places for a hands-on, interactive experience. Not only do they transcend the two-dimensionality of all the other avenues available to the general public for learning more about science: in addition, visitors can progress at their own pace and form their own priorities of interest. The more funds available, therefore, the better: this invaluable resource can then develop as effectively as possible whatever ploys and tricks might capture the imagination of those who had previously disregarded scientific knowledge as irrelevant, abstract, and set in concrete.
Susan Greenfield is a neuroscientist at the University of Oxford, and Gresham Professor of Physic, London