Quantum_ Einstein, Bohr and the Great Debate About the Nature of Reality - Manjit Kumar [7]
With the creation of a unified Germany in the wake of the Prussian-led victory over France in the war of 1870–71, Berlin became the capital of a mighty new European nation. Situated at the confluence of the Havel and the Spree rivers, French war reparations allowed its rapid redevelopment as it sought to make itself the equal of London and Paris. A population of 865,000 in 1871 swelled to nearly 2 million by 1900, making Berlin the third-largest city in Europe.15 Among the new arrivals were Jews fleeing persecution in Eastern Europe, especially the pogroms in Tsarist Russia. Inevitably the cost of housing and living soared, leaving many homeless and destitute. Manufacturers of cardboard boxes advertised 'good and cheap boxes for habitation' as shanty towns sprung up in parts of the city.16
Despite the bleak reality that many found on arriving in Berlin, Germany was entering a period of unprecedented industrial growth, technological progress, and economic prosperity. Driven largely by the abolition of internal tariffs after unification and French war compensation, by the outbreak of the First World War Germany's industrial output and economic power would be second only to the United States. By then it was producing over two-thirds of continental Europe's steel, half its coal, and was generating more electricity than Britain, France and Italy combined. Even the recession and anxiety that affected Europe after the stock market crash of 1873 only slowed the pace of German development for a few years.
With unification came the desire to ensure that Berlin, the epitome of the new Reich, had a university second to none. Germany's most renowned physicist, Herman von Helmholtz, was enticed from Heidelberg. A trained surgeon, Helmholtz was also a celebrated physiologist who had made fundamental contributions to understanding the workings of the human eye after his invention of the ophthalmoscope. The 50-year-old polymath knew his worth. Apart from a salary several times the norm, Helmholtz demanded a magnificent new physics institute. It was still being built in 1877 when Planck arrived in Berlin and began attending lectures in the university's main building, a former palace on Unter den Linden opposite the Opera House.
As a teacher, Helmholtz was a severe disappointment. 'It was obvious,' Planck said later, 'that Helmholtz never prepared his lectures properly.'17 Gustav Kirchhoff, who had also transferred from Heidelberg to become the professor of theoretical physics, was so well prepared that he delivered his lectures 'like a memorized text, dry and monotonous'.18 Expecting to be inspired, Planck admitted 'that the lectures of these men netted me no perceptible gain'.19 Seeking to quench his 'thirst for advanced scientific knowledge', he stumbled across the work of Rudolf Clausius, a 56-year-old German physicist at Bonn University.20
In stark contrast to the lacklustre teaching of his two esteemed professors, Planck was immediately enthralled by Clausius' 'lucid style and enlightening clarity of reasoning'.21 His enthusiasm for physics returned as he read Clausius' papers on thermodynamics. Dealing with heat and its relationship to different forms of energy, the fundamentals of thermodynamics were at the time encapsulated in just two laws.22 The first was a rigorous formulation of the fact that energy, in whatever guise, possessed the special property of being conserved. Energy could neither be created nor destroyed but only converted from one form to another. An apple hanging from a tree possesses potential energy by virtue of its position in the earth's gravitational field, its height above the ground. When it falls, the apple's potential energy