Max Karl Ernst Ludwig Planck is most known for his discovery of Planck's constant. In a paper in 1900 he explained how the energy emitted by a resonator could only take on discrete values or quanta.
The energy for a resonator of frequency v is h multiplied by v, where h is Planck's universal constant. This discovery is considered to be a crucial point in the history of physics, as it accounted for many of the discrepancies between observed phenomena and current physical laws. Max Planck also researched thermodynamics. Later in his career he studied quantum theory. Planck died at Göttingen on October 4, 1947.