In 1879, most physics was experimental, and Max Karl Ernst Planck, Ph. D. in physics, found himself the only theorist in the Berlin Physical Society. A principle or finding that was first predicted mathematically was consid­ered “spooky” in this German gathering, and purely theoretical studies had yet to achieve their full recognition as an essential part of the advance­ment of science. Still, in 1899, Planck won some funding from a consor­tium of electrical companies to discover how to derive the most light from lightbulbs using the least amount of power.

The problem to be solved boiled down to a central question: How does the intensity of the light emitted by a heated “black body,” or a perfect light-absorber, depend on the frequency, or color, of the light and the tem­perature of the body? There had been unsuccessful explanations of black — body radiation, and many experimental results had been accumulated. Approaching the problem from a mathematical end, Planck found, to his despair, that the possible explanations for an energy-frequency relation­ship all seemed to center on the statistical mechanics studies of an Aus-

trian physicist named Ludwig Boltzmann (1844-1906). Planck and many of his fellow physicists at the time held a strong aversion to these proba­bilistic, statistics-based interpretations. Deeply suspicious of the philo­sophical and physical implications of his own work, Planck sacrificed his convictions and derived an important equation:

E = hv

E is the energy of a photon, which is directly proportional to the fre­quency, v, of the photon. A constant, h, completes the conversion. The energy of light is dependent only on its frequency. The startling implica­tion is that a light beam of a given frequency, v, cannot be divided down

any lower than hv. Any further division, and the beam is no longer light. An inten­sity, or quantity, of light is simply an inte­ger multiple of hv, but h is so small we do not normally notice any digital jump in brightness. The constant, h, became known as Plancks action quantum, or simply Planck’s constant. The equation proved accurate in all experimental confirmations.

Although he received the Nobel Prize in physics in 1918 for having derived this formula, Max Planck had a difficult time believing in his own work. The concept of quantized energy destroyed his under­standing of classical theory, and he was never able to accept it as a reality. Other stubborn, traditional physicists simply gave Planck’s constant a value of zero and continued as if nothing had changed. Albert Einstein (1879-1955), a forward- thinking theoretical physicist in Germany, would explain the equation in his 1905 paper as an expression of light quanta, or photons, which were tiny, discrete par­ticles of light. To the unending despair of both Einstein and Planck, quantum mechanics was born.

Although Einstein was disturbed by quantum mechanics, he gave birth to it with his Nobel Prize-winning theory of the photoelectric effect in 1905. (Popperfoto/Getty Images)