What Is Quantum Mechanics?

As ironic as it is, Quantum Mechanics in some ways began with Albert Einstein when he revealed his theory of relativity in the early years of the 20th century. The irony comes from the fact that Einstein was forever at odds with the emerging discipline of physics, causing him to erupt in one of his famous quotes, “God does not play dice with the universe!” To which his opponent replied, “Don’t tell God what to do!”

Quantum mechanics focuses on the atomic level of reality. Even beneath that, the quantum realm includes within in the scale of reality that deals with atomic and subatomic particles. The mathematics of quantum mechanics allow us to calculate probabilities of the microscopic level of reality, which led to strange conclusion about the physical world. A challenging new perspective on reality. At the level of atoms and electrons, many of the equations of Classical Mechanics break down. Yet the equations of Quantum Mechanics are correct, and are proven to be every day in modern technological and scientific applications where their predictions and equations are used.

Over decades, a group of several disputable mathematical explanations of experiments arose, which the mathematics of classical mechanics was unable to explain. This resulted in the development of Quantum Mechanics. [1] In classical mechanics — dealing with motion of objects on the scale of our size up to cosmic scale, from bullets and baseballs to planets and beyond — all objects have perfectly definable positions and speeds and such. However, when we get to the quantum level of reality, electrons and other particles and subatomic particles all exist in a state of probability, where they have an exact possibility of being in one state A, versus being in another state B. [1]

In contrast to scientific revolutions like General Relativity, Astronomy, and even Classical Mechanics which were created by one single person, the foundation of Quantum Mechanics were the result of the contribution of a number of physicists over some 30 years between 1900 and 1930. Modern Astronomy may have been founded by the work of Nicolaus Copernicus, where he proved the heliocentric model of the “universe” (well at least of the Solar System revising the dynamic of Earth and Sun, putting both the Earth and the Sun towards a proper understanding of their place in the galaxy, and eventually, the universe). Classical Mechanics may have been founded with the Three Laws of Motion of Isaac Newton, along with Newton’s introduction of Calculus. Einstein with his introduction of General Relativity. All theories being contributed to and better understood over the work of every scholar and scientist since.

Multiple physicists contributed to the development of Quantum Mechanics, which arose organically under the weight of irrefutable conclusions of the nature of matter. Three principles confirmed and verified experimentally over decades:

1. That matter is quantized on a fundamental level. Properties like speed, mass, position and color seemed to be set in specific levels, quantized into predictable, known, universally defined amounts. In quantized units. This contradicted core assumptions of classical mechanics, that these properties could distributed along a continuous spectrum of possible values.
2. Particles of Light. It was found also that light was quantized into specific fundamental units, broken into discrete — specific and finite — units of light that we call a photon of light. Light also is quantized into a fundamental piece. The idea that we could consider a Particle of Light ran contrary to previous beliefs about light, because in hundreds of years of experience, light had proven itself to behave as a wave. Yet it was found to behave as a wave, with peaks and troughs on its path as an electromagnetic wave. More wave crests creates brighter light, but two light waves that are deconstructive interference to one another, annul one another to create darkness.
3. Waves of Matter. Matter can behave as a wave, which contradicts all known experiments until recent years that show that matter (such as an electron) exists as particles.

These ideas — the Quantization of Matter, Particles of Light, and Waves of Matter — coalesced into the understanding of Quantum Mechanics over the 30-or-so years from 1900–1930.

Notes

Resources

1. Quantum Physics for Beginners. Michael Rutherford.