History of Quantum Mechanics

Quantum mechanics is a branch of physics that deals with matter and light at an atomic scale, often contradicting our observations of large-scale phenomena in our daily lives.

Max Planck made a transformative suggestion in 1900 that revolutionized our understanding of matter and radiation: He suggested that energy could not only be released continuously but in discrete packets called quanta.

Max Planck

In the second half of the 19th century, laboratory discoveries that defied classical physics began emerging that contradicted its accepted view. These included findings such as heated objects emitting certain types of radiation when heated to certain temperatures, an increase in entropy with temperature, and that an atom’s charge could depend on its temperature – all things that seemed out of step with classical worldview and required explanations that fit within it. Physicists attempted to provide their answers.

Hermann Wenck and Robert Wilhelm Helmholtz conducted experiments pertaining to the emission of electromagnetic radiation by heated substances, led by Hermann Wenck’s studies and Robert Wilhelm Helmholtz’s investigations. Wenck demonstrated that radiation emitted by wild substances depends on its frequency rather than on wavelength or polarization; his work established E=hn (where h is Wenck’s value of Planck’s constant, now commonly referred to as Planck factor, while n is the frequency of electromagnetic radiation).

Planck’s derivation relied on the assumption that an atom or radiator emitting electromagnetic radiation could only assume specific energy values within an acceptable range; from this, he concluded that as the entropy of an atomic system depends solely on its temperature, any emission must occur at only one specific energy value.

He presented this derivation at a meeting of the German Physical Society in December 1900 without realizing he had introduced energy quantization, one of the cornerstones of quantum mechanics.

Quantum mechanics has been an enormously successful field, yet it still presents many issues which remain unanswered. One such issue is measurement; due to quantum physics, it is impossible to take measures without disturbing some part of a system in some way; we don’t fully understand what this disturbance entails, so in order to know its natural state, we must repeat measurements again and again in order to get accurate readings of where things stand.

Niels Bohr

Niels Bohr was mainly preoccupied with the philosophical questions raised by quantum mechanics during his later life. Although he never provided definitive answers, his insights have helped shape our understanding of this theory. According to Bohr’s philosophy, known as pragmaticism – which emphasizes practical application over ultimate ontological or epistemological meaning – physicists must use classical concepts like observations to connect mathematical formalism with a comment – quantum mechanics is inextricable from word; using such classical images would further facilitate connection. Bohr believed physicists must use classical ideas to connect mathematical formalism with observation in order to connect mathematical formalism with statements; this philosophy led him away from formal forms like quantum mechanics underlying it all.

But unlike some of his contemporaries, Bohr did not hold that quantum mechanical formalism was false in that it presented an inaccurate depiction of reality that deviated from that depicted by classical science. Instead, he opposed theory realism and held that an accurate description of experimental phenomena is what matters.

His ideas were heavily influenced by Rutherford and Heisenberg, in particular, their work concerning electron orbits around atom nuclei with both positive and negative electric charges; their energy levels determined the chemical properties of elements.

He developed a theory on how electromagnetic force works between particles, with his model explaining why particles in magnetic fields behave differently from those in electric ones, as well as predicting that specific protons would always possess equal mass and charge.

Erwin Schrodinger was an influential mentor to Werner Heisenberg. Additionally, he played an essential role in developing Copenhagen’s interpretation of quantum mechanics. In 1922, he received the Nobel Prize for Physics for his research into the structure of the atom.

Though Bohr’s views on quantum theory evolved over the years, he always held to the belief that classical concepts were necessary for creating clear communication about observations. According to him, these were necessary both to connect mathematical formalism with words and to explain non-separability and contextuality.

Werner Heisenberg

Werner Heisenberg was born into an upper-middle-class academic family in Germany on December 1901. A talented student, Heisenberg was known to pick up on the subject quickly – fascinated with mathematical problems, technical gadgets, and physics in equal measure. Starting his studies at Munich’s University of Munich in 1920 and after two years having published four physics papers under Arnold Sommerfeld’s encouragement, he met and became close with Wolfgang Pauli, who was one year his senior.

At that time, the dominant theory of the atom modeled electrons as moving in quantized orbits around its nucleus. While this worked well for hydrogen molecules, larger ones required something different, and so physicists recognized they needed a new theory.

Heisenberg created matrix mechanics (now wave mechanics), which allowed physicists to predict the properties of particles without needing visual models as had been used by previous theories. Heisenberg also introduced his uncertainty principle, which states that physical systems cannot be measured precisely due to factors other than mere measurement apparatus but the nature of their structure itself.

Heisenberg received the 1932 Nobel Prize in physics for his groundbreaking work in quantum mechanics. His theory, matrix mechanics, extended Bohr’s model by explaining quantum jumps. Additionally, Heisenberg described how energy changes depending on the momentum of an atomic system, as well as providing a formula calculating the probability for transition events to occur.

Heisenberg continued teaching at the University of Gottingen while spending some time in Copenhagen working with Niels Bohr on a Rockefeller grant. In 1937, he married Elisabeth Schumacher and had twins Maria and Wolfgang two years later; over time, they would go on to have five more children together over 12 years before his untimely death in 1948 from a heart attack was eventually laid to rest at Zentralfriedhof Vienna Austria he is most widely remembered today for his scientific contributions which often got interrupted due to travels or upheavals caused by war.

Erwin Schrodinger

Erwin Schrodinger stood out among his peers by his unique ability to quickly absorb teachings during lectures and apply them directly afterward, according to one of his classmates. According to her account, Erwin could “read a book without notes and, even after the lecture had finished, answer any question asked of him with playful ease.”

After graduating from the University of Vienna in 1906, he worked as an experimental physicist for four years before transitioning into theoretical physics. Applying Boltzmann-like statistical mechanical concepts to magnetic and other properties of bodies led to him earning his advanced doctorate or Habilitation degree.

He found experimental work unappealing, yet it helped him understand the nature of particles and waves. Through his work, he came to accept Louis de Broglie’s wave-particle duality concept – in which particles or other forms of matter behave both as waves and particles at various times depending on how they interact with their environment.

From 1924 to 1935, he dedicated himself to developing his theory of quantum mechanics. Among other contributions, he created his namesake equation and solved for energy eigenvalues of hydrogen atoms in their ground state – work which stands as one of the most significant contributions made to 20th-century physics.

Even with its impressive predictive power, the new theory does not come without issues. One major drawback of quantum mechanical models is their inability to reveal exactly what’s happening on a microscopic level; rather they offer only probabilistic predictions.

Another issue with theory is its potential to violate fundamental principles, as demonstrated by observations such as an electron in a hydrogen atom that cannot simultaneously exist as both particle and wave.

Quantum mechanics has had remarkable success despite these obstacles, contributing to lasers, light-emitting diodes, transistors, medical imaging, and electron microscopes, as well as many other technologies used across industries – even your cell phone may depend on this science! To learn more about quantum mechanics, visit DOE Explains.