If Max Planck hadn’t ignored some bad advice, he would never have started a revolution. The pivotal moment happened in 1878, when young Planck asked one of his professors whether to continue pursuing a career in physics. Herr Professor Philipp von Jolly told Planck to find another line of work.
All the important discoveries in physics had already been made, the professor assured his young protégé. As Planck later recalled, von Jolly told him, “[Physics] may yet keep going in one corner or another, scrutinizing or putting in order a jot here and a tittle there, but the system as a whole is secured, and theoretical physics is noticeably approaching its completion.”
Putting one of those jots in order, it turned out, eventually won Planck a Nobel Prize — and led to the birth of quantum mechanics. The troublesome trifle concerned a very ordinary phenomenon: Why do objects glow the way they do when heated? All materials, no matter what they’re made of, behave the same way with increasing temperature: turning red, then yellow, then white. Yet no physicist in the 19th century could explain this seemingly simple process.
The problem came to be called the ultraviolet catastrophe, because the best theorem of the day predicted that objects heated to very high temperatures should spew infinite amounts of short-wavelength energy. Since we know a strong current doesn’t turn light bulbs and toasters into energy-spewing death rays, 19th century physics clearly wasn’t the last word.
Planck found an answer in 1900 with what amounted to a modern-day hack. He proposed (guessed, really) that energy could only be absorbed or emitted in discrete packets, or quanta. It was a radical departure from so-called classical physics, which held that energy flowed in smooth, continuous streams. At the time, Planck had no theoretical justification — but it turned out to work anyway. His quanta effectively capped the amount of energy that heated objects could release at any temperature. No more death rays.
