Planck

Planck refers to a surname associated with the German physicist Max Planck (1858–1947), who is widely regarded as the founder of quantum theory. In 1900 he proposed that electromagnetic energy is emitted or absorbed in discrete units called quanta, with energy proportional to frequency via the constant h. This idea initiated quantum mechanics, and the Planck constant remains a fundamental parameter in modern physics. The reduced Planck constant, ħ = h/(2π), appears in many quantum equations, such as E = hν = ħω.

Planck units are a system of natural units defined from fundamental constants, including the Planck length, Planck time, Planck mass, and Planck temperature. The Planck length is about 1.616×10^-35 meters, the Planck time about 5.39×10^-44 seconds, the Planck mass around 2.18×10^-8 kilograms, and the Planck temperature near 1.42×10^32 kelvin. These scales are used to discuss physics at the intersection of quantum mechanics and gravity, where conventional theories may require unification.

Planck’s work established the quantization of energy and laid the groundwork for quantum theories that describe atomic and subatomic systems. His insights underpin quantum mechanics, quantum electrodynamics, and many aspects of modern physics, influencing fields from spectroscopy to condensed matter physics.

The Planck satellite is a separate use of the name in astronomy. Launched by the European Space Agency in 2009, it mapped the cosmic microwave background with high sensitivity and resolution, providing data that tightened constraints on cosmological parameters and models of the early universe.