A. 1. GARRATT Festival of Britain Office, London, England
ANEXHIBITIONof
Science at South Kensington,London, forms part of the Festival of Britain this summer. Science, of course, appears in its "user setting" in almost all of the festival exhibitions, as well as occupying a unique place in the giant "Dome of Discovery" on the South Bank. In the Exhibition of Science, however, it is considered in its "pure" sense, i. e., man's quest for knowledge into the structure of matter, both inanimate and biological. In common with all the scientific displays in the festival, accuracy of presentation and thematic balance have been assured by very close collaboration with almost all the leading scientists in Britain. In order to introduce the public to the idea that matter consists of molecules and atoms, a novel entrance sequence has been designed; this is contained in five rooms with interconnecting corridors. In the first room there is a pencil-lead writing on a piece of paper, a11 a t natural size. Leaving this the public passes through a corridor in which they are told by loudspeakers that they are entering a wonderland where things grow larger and larger. To heighten the effectthe ceiling rises and stripes on the walls get wider and diverge. The second room contains the pencil-lead and paper magnified by a factor of ten-this scale increase being chosen to condition the public to what follows. In the next corridor, which is fairly dark, the loudspeakers explain that the factor of magnification is now a thousandfold, i.e., lo4 times life size. The paper appears exceedingly rough and the tip of the pencil lead is seen with flakes of graphite sliding from it. The speech in the third corridor is somewhat inhuman, an effect obtained by using a mixture of straight speech and speech in which the vocal chord sounds have been replaced by organ chords by means of a Vocoder. The public is prepared for another thousandfold scale increase and the fourth room shows the crystal structure of the graphite. This, of course, no longer resembles the original lead, hut appears as the familiar hexagon pattern. Peaks and valleys in the structure signify the rough surface of the graphite. The speech in the final corridor is as inhuman as ie compatible with intelligibility, and it explains that the final room is at a magnification of 10.'O To heighten the effect of unreality, the floor is covered with "Dunlopillo" (rubber mattress material) and the room is in total darkness except for the actual display. This is a wave-mechanics representation of a carbon crystal, in which the probability of finding an electron a t any place is translated into light intensity. The atomic
nuclei appear as bright white spots in space; symmetrically round them are the spherical K shells shown as somewhat fuzzy clouds of blue light. The trigonal bonds connecting the appropriate nuclei are green clouds of light, while the a orbitals, protruding forward and backward, normal to the nuclear planes, are yellow clouds. Behind the first nuclear plane other nuclear planes can be seen stretching hack to an apparent infinity. The dimensions of this display are 17 ft. by 7 ft.. surely the largest wave-mechanics atom in the world. The techniques used to produce the effects in this sequence have been the result of considerable research and development, and they represent a great advance on the usual ball and spoke models. The display in the fourth room showing the crystal structure of graphite consists of a number of parallel sheets of plate glass normal to the observer. The crystal pattern, including the peaks and valleys, is built up by etching the atoms on the glass which is edge-lit. The atoms thus appear as tiny points of light, the stmcture being seen in three dimensions. The final room, with the wave-mechanics crystal, is somewhat similar in construction. Instead of glass, "Perspex," the British trade name of transparent acrylic resin, is used. Twenty parallel sheets, each 17 ft. by 7 ft. are placed between a semisilvered mirror at the front and a fully silvered mirror a t the rear-these parallel mirrors producing the repeating pattern of nuclear planes. The nuclei consist of small hemispheres cut in the Perspex and filled with white phosphors. The "probability clouds" are sprayed onto the sheets in colored phosphors, the multiplane construction permitting any three-dimensional pattern to be built up. The entire display is illuminated from the top with ultraviolet light-thus producing the glowing clouds of color. Perspex is used instead of glass on account of its high transparency to ultraviolet light, any fire risk being minimized by the fitting of automatic sprinklers in the ceiling. The rest of the exhibition following this initial sequence demonstrates, in as dynamic manner as possible, our present knowledge of stmcture. Starting with change of state and Brownian motion as commonsense evidence of the existence of molecules, it continues with the breakdown of everyday objects into elements and then into atoms. The main circulation shows how the concept of stable electron shells explains how compounds are built up; this theme is carried through to more complicated organic chemistry including synthesis. The chemistry of proteins forms the
JUNE, 1951 link to biological structure. Supplementary circulations trace the structure of light, of crystals, and of metals, while another section is devoted to atomic physics from the discovery of the electron to nuclear fission. The biological section, "Living Structure," shows how the cell is the fundamental unit and how cells are put together to form the most complicated organisms. Reproduction and genetics form part of this story, as well as examples of cells that have "gone wrong" and resulted in cancer.
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The final part of the exhibition, called "Stop Press," deals with some of the latest research that is engaging the attention of scientists. The subjects chosen for this section are: sensory perception, electrons in crystals, the physical and chemical approach to the problem of life, electronic computers, cosmic rays, and the formation of the universe. This last subject, which forms the finale of the exhibition, demonstrates the Hoyle theory by means of five dynamic models, ending with the expanding universe and continuous creation of matter-a fitting climax to the exhibition.
