Planck’s Second Quantum Theory

Abstract

The notion of a zero-point energy is a result of quantum theory and has no proper counterpart in classical physics. It was introduced by Planck in 1911, more than a decade before the emergence of modern quantum mechanics. Planck’s so-called second quantum theory, on which the zero-point energy was based, was discussed for a brief period of time, but by 1920 at the latest it was abandoned by most physicists. On the other hand, although Planck’s theory was dismissed, the idea of a zero-point energy lived on. No one could tell whether it was more than just an idea.