## Max Planck and the quantum nature of energy

*"A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it." Max Planck (1858-1947).*

Coming from an academic background --- his father being a professor of Law, while grandfather and great-grandfather both professors of Theology --- it was no surprise that Max Planck would continue in their tradition. Although an average student in school, his brilliance came to the fore during his tenure as professor in the University of Berlin. Popular for his outstanding lectures, he was particularly drawn to thermodynamics and the distribution of energy according to wavelength. Putting together the laws developed by Wien and Rayleigh, Planck developed what is now referred to as Planck's radiation formula. He soon followed up with a theoretical derivation supporting his formula that renounced classical physics.

He published several papers on thermodynamics, and was interested in radiation processes, which he propounded to be electromagnetic in nature. This led him to study the distribution of energy in the spectrum of full radiation. Planck was able to deduce the relationship between the energy and the frequency of radiation. This formed the basis for what is now called Planck's constant. The quanta of energy or the quantum theory of energy had thus come into being. Planck was awarded the Nobel Prize in 1918 in recognition of his outstanding contribution to Physics through his quantum theory of energy.

Planck took little part in the further development of quantum theory, this being left to Paul Dirac and others and turned towards administrative duties as Secretary of the Mathematics and Natural Science Section of the Prussian Academy of Sciences and later as president of the Kaiser Wilhelm Gesellschaft, Germany's premier research organization.

Max Planck remained in Germany through the World Wars during which he experienced terrible personal tragedy; his second son was executed for conspiring to kill Hitler. He had lost his eldest son in the earlier war. He openly opposed the policies of the Nazi regime, particularly the persecution on of the Jews. He died on October 3, 1947 in Göttingen, Germany.

**Max Planck and the Quantum Theory**

"The outside world is something independent from man, something absolute, and the quest for the laws which apply to this absolute appeared to me as the most sublime scientific pursuit in life"- his reasons for opting to study physics

The quantum theory and the theory of relativity together form the theoretical basis of modern physics. While the theory of relativity comes into play in the special situation where large speeds are involved, the quantum theory is necessary when very small quantities are involved, i.e., on the scale of molecules, atoms, and elementary particles. Some aspects of quantum theory have also provoked theories of uncertainty principle and predictions theories in particular the statistical nature of it.

Classical physicists treated energy as continuous phenomenon, while matter assumed a specific region in space. But according to the quantum theory, energy is regarded as something, which is emitted and absorbed in tiny amounts. A packet of energy is termed quantum, this packet has a dual nature, and it sometimes behaves as energy and sometimes as particles of matter. The particles of energy exhibit certain wavelike properties when in motion.

The quantum theory was the collective development of several scientists over a period of time. However the groundbreaking contribution was given by Planck in his explanation of black body radiation in 1900. The final mathematical formulation of the quantum theory was developed during the 1920s.

Planck like many of his colleagues was steeped in traditional physics but he had an extremely open mind. He changed one basic assumption, energy instead of being continuous, comes in distinct packets or quanta. While studying black body radiation, Planck discovered that at very short wavelengths it did not obey the distribution laws given by Wilhelm Wien. In stead, a black body gave off an infinite amount of energy at the ultraviolet end of the spectrum. Planck mulled over this problem for several years and finally in 1900, he cautiously proposed that contrary to classical wave theory, matter emits and absorbs radiation in tiny discrete packets or bundles called "quanta" - not continuously, as everyone had assumed.

Planck later explained that energy radiated from a heated body is proportional to the wavelength of its radiation, in that respect, a black body would not radiate all frequencies equally. As temperature goes up, energy increases and it's more likely that quanta with higher energy will be radiated. So, for a body, which heats up, it first gives off an orange light, then yellow and eventually bluish. The wavelength emitted is a function of the energy times a constant (h), now known as Planck's constant.

In 1905, Albert Einstein used this theory to accurately describe the photoelectric effect. In 1913, Niels Bohr incorporated Planck's idea into his revision of model of the atom, resolving inconsistencies that classical physics could not.

Offshoots of quantum mechanics include the uncertainty principle, developed by Heisenberg; quantum statistics, presented by Einstein and S. N. Bose - the Bose-Einstein statistics and by Dirac and Enrico Fermi - the Fermi-Dirac statistics; quantum electrodynamics, concerned with interactions between charged particles and electromagnetic fields; quantum field theory; and quantum electronics.