Planck's Natural Units and Planck Time

On May 18, 1899, German physicist Max Planck published a paper introducing natural units of measurement based on universal physical constants. In "Über irreversible Strahlungsvorgänge," Planck proposed units for time, length, mass, and temperature independent of human constructs, defining them through fundamental constants of nature. Among these was Planck time (approximately 5.39×10^-44 seconds). Planck stated these units would have universal meaning "for all times and for all civilizations, even extraterrestrial and non-human ones." This work contributed to the foundations of quantum mechanics and relativity theory.