In this guest blog post, my good friend Jason begins his fight to take back the phrase "quantum mechanics" from the humanities majors who have hijacked it.

At the foggy crossroads of pop-culture and pseudo-science the word “quantum” is used everywhere. In the New Age realm, hacks and charlatans with crystals and charts use the term to get noticed and to lend pretended credibility to their quackery. In cinema and television it’s used with reckless abandon on the sci-fi circuit and anywhere else where a string of technical jargon needs a little spicing up. The term has even worked its way into soft science contexts—most of which have little capacity to support the term or its original meaning in any serious way.

The result of this semantic molestation is that the word and anything it’s used with carries an almost mystic quality. And while the world’s best minds do indeed find quantum mechanics (in the original scientific meaning of the phrase) quite weird, there’s nothing mystical about it. It’s a theory that describes nature as it behaves, has always behaved, and will always behave. Sure, it’s fascinating, compelling stuff—but that only speaks to the fact that nature needs no embellishment, and that the natural world is more complex and beautiful than the archaic myths of Bronze Age mankind. Furthermore, to see good, genuine science grouped with the likes of astrology, Transcendental Meditation, and Deepak Chopra—now that is an abuse to which I will not stand an idle witness. Something must be done!

With that in mind, I think the best way forward is to provide very basic, heuristic descriptions of the physics of quantum mechanics in a way accessible to the average Joe (that is, not majoring in physics). Hopefully this will take away some of the subject’s mystical flavor and replace it with a level of comprehension that, while extremely basic, will at least be rooted in an attempt at honesty. I’ll begin in this post with the four-letter word itself—i.e. what the “quantum” in quantum mechanics actually means.

Before we truly get started, though, we need to know the physical definition of “energy.” Strictly speaking, energy in physics has one and only one definition, namely that given by its units, the Joule or Electron Volt. That said, it’s also one on the most fundamental concepts in nature; so fundamental, in fact, that there really isn’t anything simpler it can easily be described in terms of. In a physics class, the prof would most likely just write down the formal equation defining energy and call it good (which, for the record, is really how it ought to be done). For the sake of reaching a larger audience, however, I’ll attempt to give you and accurate-enough idea of what energy is without math, so you can understand the rest of what I say.

In the classical world (i.e., your everyday experience) there are two important types of energy: kinetic and potential. Kinetic energy is the energy associated with moving objects—a baseball, for example, has a certain energy associated with how fast it is pitched. Potential energy is a bit more abstract but still very tangible; generally speaking it’s the energy associated with something’s position in space. If you took that same baseball up to the top of a cliff five kilometers high it would have energy associated with its height (in this case five kilometers) off the ground.

Now suppose you threw your baseball off the aforementioned cliff. It would have some kinetic energy to start with depending on its mass and how hard you threw it and some initial potential energy since it was five kilometers above the earth to start with. As the ball fell to earth its potential energy would be converted into kinetic energy (as it lost altitude) until, in the instant before it hit the ground five kilometers below, its energy was completely kinetic.  

Depending upon how hard you threw the ball and from how far up it was thrown, the sum of its kinetic and potential energy could take on any real number. In other words, there’s no rule dictating what the total energy of the baseball could be. In classical physics this is generally true but in the quantum world things are very different.

On a quantum scale (around that of an electron) it actually isn’t possible for the energy of a particle to take on every real number in every physical situation. With our cliff example, if the ball were the size of an electron, depending upon its environment, it’s possible that the ball would only physically be allowed to take on certain discrete energy values. Its energy might take the values of the real numbers (1, 2, 3, ... etc) but not the rational (1/2, 1/3, 1/4, ... etc) or irrational numbers (√2, ℮, π, etc) if,  for example, it were confined to some region in space. This property of energy to be confined to discrete values on very, very tiny scales is called quantization (or more specifically, energy quantization) and it’s from this term that the “quantum” in quantum mechanics is derived.

One real world example of quantization is the Bohr Model of the atom—the molecular model that you likely learned in your junior high chemistry class. Because the atom's electrons are in some sense confined to the atom, their energies take on discrete values and thus exhibit energy quantization. Furthermore, because (as it so happens) an electron’s energy depends upon the radius of its orbit (think: the height of the ball off the ground), the electron’s orbit must only be capable of discrete positions in space. Hence, the quantized electron orbits of the Bohr Model of the atom.

Next, in part two, I’ll try to explain why confining an electron to a region of space in situations like those above, causes its energy to be quantized. The answer, as it so happens, follows from one of the greatest scientific discoveries of all time: that matter— electrons included—behaves like a wave. This leads further to the realization of other amazing phenomena like zero point energy and quantum tunneling; all of which, hopefully, I’ll be able to explain in some semi-coherent way.

Jason T. Martineau (The “T” is for “Thorgny") is a physics major and a member of the Class of 2011 at the University of Utah. His greatest dream is to witness the detonation of a nuclear weapon, before or when he dies.