- A depiction of various atomic - http://www.matfys.lth.se/Thomas.Guhr/horbitale.gif
The group of theories in physics which have collectively become known as “Quantum Mechanics” certainly seems quite imposing on the surface. These theories deal with elements of the natural world which are far too small to ever see with the naked eye (and even with the fanciest microscopes, but for a few exceptions). They have been developed to describe the behavior of the smallest particles known to man, and have done so with a very surprising degree of accuracy.
These theories, along with Einstein’s theories of Relativity, have become truly fundamental to almost all of physics today. The entirety of particle physics is founded on the ideas which began in the first decades of the twentieth century under the earliest quantum physicists such as Max Planck, Werner Heisenberg, Niels Bohr, Max Born and Erwin Schrodinger. The theories of these great scientists were able to usher in an entirely new era of scientific research.
And what has been gained from such studies? What is now known about these particles? How well can we predict the movements and interactions of particles?
These are all very complicated questions; for according to the fundamental rules of quantum mechanics, it is possible for physicists to understand the behaviors of particles on a statistical level – that is, large groups of particles interacting with each other can be well defined, for they tend to follow the same statistical rules. However, on an individual level, quantum mechanics theorizes that exact predictions simply cannot be made.
A Quick Summary of Quantum Mechanical Principles
Quantum mechanics on its most fundamental level can be understood by even a layperson if they become familiar with a few key subjects:
1) Wave-Particle duality. Isaac Newton theorized that light consisted of particles. In the 19th century Thomas Young overturned this theory with his belief that light consisted of waves. With the onset of quantum mechanics, it became clear that light consists, oddly enough, of both.
2) The observation that light exists as particles is where the term “quanta” comes from – for these individual particles of light are known as “quanta” of light – they are the smallest portions of energy that can possibly exist. With this theory it finally became clear the relationship between the color of light and the emission of radiation.
3) These particles move in a “wave-like” manner – which explains Thomas Young’s experimental results which concluded that light behaves as a wave. According to quantum mechanics, however, these waves are not actual, physical waves, but waves of probability, defining the chances of finding each individual quanta (or “photon” as they are more commonly called) at any given moment.
4) The Heisenberg Uncertainty principle defines the notion that a “photon” cannot be observed as both a particle and a wave at the same time when undergoing measurement. In other words, the “wave” qualities (which define the particle’s momentum) and the “particle” qualities (which define the particle’s exact position) can never be known at the same time. Thus, one can measure either a photon’s position or its momentum, but never both. Thus, each photon individually is more or less impossible to fully define (hence, uncertainty)
5) Any of these first four points hold true not only for electromagnetism (light and energy) but for all objects. These quantum mechanical properties, however, are only measurable when dealing with individual subatomic particles. As objects get larger, the quantum mechanical properties diminish rapidly. In any visible object, therefore, while each individual atom may be impossible to define, as a collective entity they obey statistical laws, and are thus both predictable and tangible.
Final Observations on Quantum Mechanics
While mere summaries of these five points may not make quantum mechanics clear to anyone, they at least begin to demonstrate exactly what quantum physicists have gone up against – defining the inherently indefinable; measuring the almost infinitely small.
And the story behind the formulation of these theories is one of incredible scientific and historical interest. The men and women who were instrumental in developing this new field are some of the greatest minds the world has produced, and a look at who they were is incredibly beneficial to anyone with even a passing interest in science.
Finally, it should be noted that physicists themselves recognize just how difficult quantum mechanics truly is to fully comprehend. In fact, nearly any popular physics book ever written possesses a new way of explaining the fact that, in fact, no one understands quantum mechanics. It is just one of those things that has to be accepted on a certain amount of faith.
Niels Bohr once said that, “Anyone who is not shocked by quantum theory has not understood it.” Similarly, John Gribbin wrote that, “As long as you avoid asking what it means, there are no problems.” And Richard Feynman, that master of taking difficult science and humanizing it somewhat, said this:
“There was a time when the newspapers said that only twelve men understood the theory of relativity. I do not believe there ever was such a time. There might have been a time when only one man did, because he was the only guy who caught on, before he wrote his paper… On the other hand, I think I can safely say that nobody understands quantum mechanics.”
Indeed, this seems exactly to be the case.
References:
Gribbin, J. (1994). In Search of Schrodinger's Cat: Quantum Physics and Reality. New York, NY: Bantam Books.
Gribbin, J. (1995). Schrodinger's Kittens and the Search for Reality: Solving the Quantum Mysteries. New York, NY: Time Warner Book Group.
Kl-Khalili, J. (2003). Quantum: A Guide for the Perplexed. New York, NY: Weidenfield & Nicolson.
Feynman, R. P. (1985). QED - The Strange Theory of Light and Matter. Princeton, NJ: Princeton University Press.
Isaac M. McPhee - Isaac McPhee was born as a human child in Mt. Vernon, WA, c. 1982; he currently resides in the bustling heart of New York City where he ...
