What is Quantum Theory for Non Physicists

The Quantum Revolution for Non-Physicists


If you ask most physicists and scientists about the pivotal events in natural philosophy at the turn of the past century, you’ll invariably receive two answers: Einstein’s Special Theory of Relativity and the Theory of Quantum Mechanics. Although both are highly-involved descriptions of the true nature of reality, their mathematical underpinnings are responsible for nearly all the technology you see around you today: before quantum theory, in particular, was understood, cell phones and televisions weren’t possible.


What is Quantum Theory?


Quantum theory deals with a surprising duality of an aspect of nature; simply put, light functions as both a particle and a wave. Before this, everyone thought of light as purely a wave (or a beam). The fact that whether light manifests itself as a particle or a wave depends on how you measure it has astounding revelations that are largely beyond the scope of this article. These attributes, however, can be seen in the way beams of light function as wide-beam flashlights, or tight, potentially deadly lasers.


Quantum theory is the discovery that all of the variables that provide a description of nature, which were previously thought to be continuous, are actually discrete. Matter, energy; everything; you just have to look closely enough. At the very smallest scales, reality exists as particles that can be numbered, and quantum theory deals with how these particles interact with each other to foster the picture of the universe we see before us. It is the only way that we can understand the behavior of electrons, photons and physical quantities like angular momentum and force.


Who Started the Quantum Revolution?


A veritable laundry list of physics superstars contributed in some way to quantum mechanics in the early years of the 20th century. Even the greatest of them all, Albert Einstein, played an absolutely significant part with his Nobel Prize winning photoelectric effect, which was the discovery that metallic surfaces emit electrons when struck by photons. Prior to this, light was viewed as either a continuous wave or a particle; this proved that light is comprised of discrete particles that can bump other particles out of place, like a billiard ball, when it comes into contact with them. Other experiments, such as the Michelson-Morley experiment, would prove that light behaves as both.


Other luminaries that played pivotal roles in the emergence of a theory of quanta are Werner Heisenberg, Wolfgang Pauli, Ludwig Boltzmann, Arthur Holly Compton, Robert Millikan, and the Father of the Atom himself, Niels Bohr. All these physicists and quite a few more developed the mathematical theory that describes how particles interact.


Quantum physics solved many problems that were outstanding at the time, and would give rise to solutions that weren’t even being looked for prior to the 20th century. Simply put, you cannot understand the world of the atom using the old classical methods, and Niels Bohr was the primary person responsible for bridging the gap between the atomic and macroscopic worlds with his rectification of the energy states of the hydrogen atom.


One of the biggest masterstrokes of quantum theory may very well have been the Uncertainty Principle discerned by German physicist Werner Heisenberg. It provides a natural limit beyond which nature can give you no information on two complementary variables. In English, it basically says you cannot know the position of a particle as well as its speed completely; there’s always give-and-take at the smallest levels. The more you know one, the less information is available for the other. And to sum it all, there are several other variables like this, such as energy and time.



quantum mechanics
quantum mechanics (Photo credit: Plucker)