Beginings of Quantum Mechanics
The Blackbody Radiation Problem
Hot objects radiate both heat and light energy, heating an iron bar gradually increases its temperature until it starts glowing in a red color that gradually transitions to a white glow at its hottest. In the early days, iron-smelters, potters, and glass-smelters were familiar with this glow during their daily workings with furnaces. The relation between the temperature of an object and the color of light it produced was high on several scientist’s minds who were actively researching the then-emerging field of Thermodynamics. The glow didn’t seem to depend on the type of material used since different furnaces of iron, clay, and glass had the same color at similar temperatures. Kirchhoff, by studying the problem using a perfect black body, found that the glow did not depend on the size or mass of an object. The relation between temperature and color (frequency) of light was a problem that lingered during the 19th century and was termed the black body problem.
The advent of long-distance electricity transmission meant cities could light up their streets and homesteads alike. Light bulbs in the century were made from a heating filament that would glow inside a vacuum. The German Institute of physical sci ordered for the research of more efficient bulbs. This task would fall onto Max Planck, then a newly appointed Professor of Physics at the University of Berlin.
Max Planck's involvement in solving the blackbody radiation problem marked a crucial turning point in the history of physics and led to the development of quantum theory. Planck approached the problem by reconsidering the fundamental assumptions of classical physics, particularly the prevailing theory of electromagnetism.
Classical physics, based on the work of scientists like James Clerk Maxwell, assumed that energy is emitted or absorbed continuously, without any quantization. However, Planck introduced a revolutionary idea that energy is quantized, meaning it can only exist in discrete packets or quanta. He proposed that the energy of electromagnetic radiation is quantized in multiples of a fundamental unit, which he called the quantum of action.
Planck's groundbreaking insight allowed him to derive a formula that accurately described the spectrum of blackbody radiation. This formula involved a constant, now known as Planck's constant (h), and it marked a departure from classical physics. The quantization of energy resolved the long-standing problem of the temperature-dependent color of emitted light, explaining the observed spectrum of blackbody radiation.
In 1900, Planck presented his findings in a groundbreaking paper, and the concept of quantization laid the foundation for quantum theory. Planck's work not only solved the blackbody radiation problem but also had profound implications for the understanding of the behavior of matter and energy at the atomic and subatomic levels.
The significance of Planck's quantum theory became even more evident with the work of later physicists, including Albert Einstein and Niels Bohr, who built upon and expanded these ideas. Quantum mechanics, as a new branch of physics, emerged, revolutionizing our understanding of the microscopic world and leading to a host of technological advancements in the 20th century.
Max Planck's contributions to the field earned him the Nobel Prize in Physics in 1918, and his work remains a cornerstone of modern physics. The transition from classical to quantum physics represented a paradigm shift in scientific thinking, challenging long-held assumptions and opening up new avenues for exploration in the fascinating realm of quantum mechanics.