In 1900, Planck discovered a relationship between the energy and frequency of light: E = hv. The equation had revolutionary implications, but it took years for anyone to realize it. And when someone finally did stumble upon the true meaning of Planck's theory, it was not Planck, but another promising young German physicist: Albert Einstein.
In 1905, the young Einstein was working as a technical expert in a Swiss patent office, and he was also engaged in formulating a series of new theories that would transform twentieth century physics. That year he published three papers that would establish him as one of the foremost physicists of the new century. One of the papers addressed Brownian motion, the random motion of particles suspended in a liquid. One of the papers, his most famous, introduced the theory of special relativity, the theory that would elevate him to international fame. But when Einstein received his Nobel prize, it was not awarded for the ideas put forward in this paper. He received this highest honor for the theory propounded in the third paper of 1905: "Concerning a Heuristic Point of View about the Creation and Transformation of Light." In this paper, Einstein revealed the implications of Planck's equation, and he threw the order of classical physics into chaos.
The equation E = hv necessitated that light energy came in finite packets, or quanta, which directly contradicted everything scientists had previously believed. According to classical physics, light is a continuous wave – not a finite particle. Planck, and those who followed him, had taken this contradiction in stride by refusing to acknowledge it. The equation was nothing more than a mathematical construct, something with no manifestation in reality. But Einstein argued that this equation described reality and that despite all evidence to the contrary, light was in fact emitted and absorbed in finite packets, as if it were a particle.
This new understanding of light as quanta, and the new light it shed on questions of the interaction between energy and matter, was eagerly taken up by at least a few bright physicists. Quantum Physics, as it came to be called, soon became the most exciting and influential field of twentieth century physics, and the new quantum physicists were quick to acknowledge the debt they owed to the father of their new discipline, Max Planck.
Planck was less than eager to accept the title. A staunch supporter of classical physics and a devout believer in light as a continuous wave, Planck was reluctant to accept what his own theory told him. As his colleague James Franck later remembered, Planck "was a revolutionary against his own will."
In 1911, Einstein and some of his colleagues convinced Planck that it was time to hold a conference on the issue of radiation and quanta to finally discuss as a group the startling new problems of quantum physics. Planck was skeptical, but he eventually agreed. That year, twenty-one of the best European physicists, theorists, and experimentalists, met in Brussels for the first Solvay Conference on quantum physics. Although the conference failed to produce any solutions to the problems facing these scientists, it was a chance for them to define themselves as practitioners of a new discipline. It was also a chance for Planck to witness the materialization of a new scientific field for which he was partly to thank.