In the year 1900, the large majority of scientists regarded the atomic hypothesis as a useful model. Yet, only few attached reality to atoms. These were convenient quantities for chemical reactions or relating electric currents to metal deposits in electrochemistry. Electricity could still be regarded as a well-behaved continuous fluid, why bother with quantized electrons? Fearful apprehensions arose against anything discrete and quantized; the beautiful mathematics of differential equations with continuous, differentiable functions seemed jeopardized. Get a glimpse of this apprehension by reading Max Planck’s textbooks on theoretical physics.

Quantum theory changed everything. Spectroscopy, an experimental method of extreme sensitivity, provided immense detail about the isolated atoms, its electrons around its nucleus. The interpretation of the emission from hydrogen was a stunning success that allayed all doubts about the new mechanics of the atom. Chemical binding became understood, and on the other hand the relativistic nature of the atomic nucleus was so well ascertained that nuclear energy indeed played a major historical role in ending the Second World War.

Rise of Semiconductor Science
The Allies spent more on radar and its semiconductor detectors than on the atomic bomb. This effort helped solids to start their phenomenal rise after the war. The transistor invention in 1949 was a bugle signal not to be overheard. Semiconductor physics began in earnest and with a truly scientific foundation; this discipline became the largest, most effective branch of physics by century’s end. Initial plans once again shied away from discreteness: polycrystalline semi-conductors seemed the only economically feasible mate-rial. Yet, the orderly, unbelievably pure and highly perfected spatial arrangement of atoms in the regular three-dimensional array of a single crystal eventually won out. The silicon crystal has become the domineering symbol of the second half century, donating us the wealth of modern computing and telecommunications.

Silicon and its related semiconductor materials will also continue to provide scientific challenges as well as economic marvels. The novel tools for lithography, deposition, doping, testing must further rely on solid scientific backgrounds. Atomic resolution in the now broad variety of electron microscopes will carry us further in the future. The huge accumulated knowledge of inorganic solids will gradually be utilized in organic and biological matter. The successful mathematical principles of understanding solidly bound atoms will continue their avenues. Geometry reduction will reveal the quantum nature of our world more clearly yet and might provide new device technologies, although the one-electron-transistor will be a difficult proposition and will require clever ideas towards technological and economic realization.

Silicon will remain for a long time the material of microelectronics, no successor is in sight, except for special applications, such as compound semiconductors in optoelectronics. But silicon will be surrounded and assisted by many other materials, cleverly applied to silicon chips. Materials with very high and very low dielectric constants are urgently needed. The dilemma of the long and sluggish metal interconnects calls for solutions; here the recent IBM technology of using the once dreaded copper is proof for the novel ideas still arising today. This trend will strongly continue, especially because of massive economical considerations.

Materials, and here most dramatically the solids, will persevere as the vital objects of scientific analysis and the source of new progress.