The Nobel Prize in Physics 1901-2000 by

5. Physics and Technology

Many of the discoveries and theories mentioned so far in this survey have had an impact on the development of technical devices; by opening completely new fields of physics or by providing ideas upon which such devices can be built. Conspicuous examples are the works of Shockley, Bardeen, and Brattain which led to the transistors and started a revolution in electronics, and the basic research by Townes, Basov, and Prokhorov which led to the development of masers and lasers. It could also be mentioned that particle accelerators are now important tools in several areas of materials science and in medicine. Other works honored by Nobel Prizes have had a more direct technical motivation, or have turned out to be of particular importance for the construction of measuring devices for the development of communication and information.

An early Physics Prize (1912) was given to Nils Gustaf Dalén for his invention of an automatic "sun-valve," extensively used for lighting beacons and light buoys. It was based on the difference in heat radiation from reflecting and black bodies: one out of three parallel bars in his device was blackened, which gave rise to a difference in heat absorption and length expansion of the bars during sunshine hours. This effect was used to automatically switch off the gas supply in daytime, eliminating much of the need for maintenance at sea.

Optical instrumentation and techniques have been the topics for prizes at several occasions. Around the turn of the century, Gabriel Lippmann developed a method for color photograhy using interference of light. A mirror was placed in contact with the emulsion of a photographic plate in such a way that when it was illuminated, reflection in the mirror gave rise to standing waves in the emulsion. Developing resulted in a stratification of the grains of silver and when such a plate was looked at in a mirror, the picture was reproduced in its natural colors. The Physics Prize in 1908 was awarded to Lippmann. Unfortunately, Lippmann's method requires very long exposure times. It has later been superseded by other techniques for photography but has found new applications in high-quality holograms.

In optical microscopy it was shown by Frits Zernike that even very weakly absorbing (virtually transparent) objects can be made visible if they consist of regions with different refractive indices. In Zernike's "phase-contrast microscope" it is possible to distinguish patches of light that have undergone different phase changes caused by this kind of inhomogeneity. This microscope has been of particular importance for observing details in biological samples. Zernike received the Physics Prize in 1953. In the 1940s, Dennis Gabor laid down the principles of holography. He predicted that if an incident beam of light is allowed to interfere with radiation reflected from a two-dimensional array of points in space, it would be possible to reproduce a three-dimensional picture of an object. However, the realization of this idea had to await the invention of lasers, which could provide the coherent light necessary for such interference phenomena to be observed. Gabor was awarded the Physics Prize in 1971.

Electron microscopy has had an enormous impact on many fields of natural sciences. Soon after the wave nature of electrons was clarified by C. J. Davisson and G. P. Thomson, it was realized that the short wavelengths of high energy electrons would make possible a much increased magnification and resolution as compared to optical microscopes. Ernst Ruska made fundamental studies in electron optics and designed the first working electron microscope early in the 1930s. However, it would take more than 50 years before this was recognized by a Nobel Prize.

Ruska obtained half of the Physics Prize for 1986, while the other half was shared between Gerd Binnig and Heinrich Rohrer, who had developed a completely different way to obtain pictures with extremely high resolution. Their method is applicable to surfaces of solids and is based on the tunneling of electrons from very thin metallic tips to atoms on the surface when the tip is moved at very close distance to it (about 1 nm). By keeping the tunneling current constant a moving tip can be made to follow the topography of the surface, and pictures are obtained by scanning over the area of interest. By this method, single atoms on surfaces can be visualized.

Radio communication is one of the great technical achievements of the 20th century. Guglielmo Marconi experimented in the 1890s with the newly discovered Hertzian waves. He was the first one to connect one of the terminals of the oscillator to the ground and the other one to a high vertical wire, the "antenna," with a similar arrangement at the receiving station. While Hertz' original experiments were made within a laboratory, Marconi could extend signal transmission to distances of several kilometers. Further improvement was made by Carl Ferdinand Braun (also father of the "Braunian tube," an early cathode ray oscilloscope), who introduced resonant circuits in the Hertzian oscillators. The tunability and the possibility of producing relatively undamped outgoing oscillations greatly increased the transmission range, and in 1901 Marconi succeeded in establishing radio connection across the Atlantic. Marconi and Braun shared the 1909 Nobel Prize in Physics.

At this stage, it was not understood how radio waves could reach distant places (practically "on the other side of the earth"), keeping in mind that they were known to be of the same nature as light, which propagates in straight lines in free space. Sir Edward V. Appleton finally proved experimentally that an earlier suggestion by Heaviside and Kennelly, that radio waves were reflected between different conducting layers in the atmosphere, was the correct explanation. Appleton measured the interference of the direct and reflected waves at various wavelengths and could determine the height of Heaviside's layer; in addition he found another one at a higher level which still bears his name. Appleton received the Physics Prize in 1947.

Progress in nuclear and particle physics has always been strongly dependent on advanced technology (and sometimes a driving force behind it). This was already illustrated in connection with the works of Cockcroft and Walton and of Lawrence, who developed linear electrostatic accelerators and cyclotrons, respectively. Detection of high energy particles is also a technological challenge, the success of which has been recognized by several Nobel Prizes.

The Physics Prize in 1958 was jointly awarded to Pavel A. Cherenkov, Il'ja M. Frank and Igor Y. Tamm for their discovery and interpretation of the Cherenkov effect. This is the emission of light, within a cone of specific opening angle around the path of a charged particle, when its velocity exceeds the velocity of light in the medium in which it moves. Since this cone angle can be used to determine the velocity of the particle, the work by these three physicists soon became the basis for fruitful detector developments.

The visualization of the paths of particles taking part in reactions is necessary for the correct interpretation of events occurring at high energies. Early experiments at relatively low energies used the tracks left in photographic emulsions. Charles T. R. Wilson developed a chamber in which particles were made visible by the fact that they leave tracks of ionized gas behind them. In the Wilson chamber the gas is made to expand suddenly, which lowers the temperature and leads to condensation of vapour around the ionized spots; these drops are then photographed in strong light. Wilson received half of the Physics Prize in 1927, the other half was awarded to Arthur H. Compton.

A further step in the same direction came much later when Donald A. Glaser invented the "bubble chamber." In the 1950s accelerators had reached energies of 20-30 GeV and earlier methods were inadequate; for the Wilson chamber the path lengths in the gas would have been excessive. The atomic nuclei in a bubble chamber (usually containing liquid hydrogen) are used as targets, and the tracks of produced particles can be followed. At the temperature of operation the liquid is superheated and any discontinuity, like an ionized region, immediately leads to the formation of small bubbles. Essential improvements were made by Luis W. Alvarez, in particular concerning recording techniques and data analysis. His work contributed to a fast extension of the number of known elementary particles then known, in particular the so-called "resonances" (which were later understood as excited states of systems composed of quarks and gluons). Glaser received the Physics Prize in 1960 and Alvarez in 1968.

Bubble chambers were, up to the end of the 80s, the work horses of all high energy physics laboratories but have later been superseded by electronic detection systems. The latest step in detector development recognized by a Nobel Prize (in 1992) is the work of Georges Charpak. He studied in detail the ionization processes in gases and invented the "wire chamber," a gas-filled detector where densely-spaced wires pick up electric signals near the points of ionization, by which the paths of particles can be followed. The wire chamber and its followers, the time projection chamber and several large wire chamber/scintillator/Cherenkov detector arrangements, combined into complex systems, has made possible the selective search for extremely rare events (like heavy quark production), which are hidden in strong backgrounds of other signals.

The first Nobel Prize (2000) in the new millennium was awarded in half to Jack S. Kilby for achievements that laid the foundations for the present information technology. In 1958, he fabricated the first integrated circuit where all electronic components are built on on single block of semi-conducting material, later called "chip." This opened the way for miniaturization and mass production of electronic circuits. In combination with the development of components based on heterostructures described in an earlier section (for which Alferov and Kroemer shared the other half of the Prize), this has led to the "IT-revolution" that has reshaped so much our present society.

 

6. Further Remarks

In reading the present survey, it should be kept in mind that the number of Nobel awards is limited (according to the present rules, at most 3 persons can share a Nobel Prize each year). So far, 163 laureates have received Nobel Prizes for achievements in physics. Often, during the selection process, committees have had to leave out several other important, "near Nobel-worthy" contributions. For obvious reasons, it has not been possible to mention any of these other names and contributions in this survey. Still, the very fact that a relatively coherent account of the development of physics can be formulated, hinging as here on the ideas and experiments made by Nobel Laureates, can be taken as a testimony that most of the essential features in this fascinating journey towards an understanding of the world we inhabit have been covered by the Nobel Prizes in Physics.

 

*Now published as a chapter of the book: "The Nobel Prize: The First 100 Years", Agneta Wallin Levinovitz and Nils Ringertz, eds., Imperial College Press and World Scientific Publishing Co. Pte. Ltd., 2001