ABSTRACT
Chapter 29 revealed that at a finite time in the past (about 13.7 billion years ago) the universe was infinitesimally small. A compression of the material of the universe into an infinitesimal volume will surely result in extreme conditions of heat, pressure, density, and energy. At a mere 20 million ◦K in the core of a star, already novel physical processes such as nuclear fusion take place. The early universe with temperatures running into hundreds of billions of degrees (and more!) must have been the arena of some of the most spectacular physical phenomena. To understand such breath-taking happenings, we need to go back to the early twentieth century and follow two developments seemingly unrelated to the early universe, one in the experimental investigations of the nucleus, the other, in the theoretical attempts at combining relativity and the quantum theory. This chapter is devoted to the experimental front.
