One physicist's 'act of desperation' invented the quantum

To explain why hot objects don't radiate infinite energy at short wavelengths, Max Planck proposed in 1900 that energy is emitted only in discrete packets, or 'quanta', rather than a continuous stream. He later called it an act of desperation, a mathematical trick he didn't fully believe. It became the founding equation of quantum physics.

— Max Planck, On the Theory of the Energy Distribution Law of the Normal Spectrum — Verhandlungen der Deutschen Physikalischen Gesellschaft, 1900