It’s finally summertime and while that doesn’t mean it won’t snow again, with summer comes all kinds of fun stuff to do. There’s music, art, all matter of outdoor activities, and intellectual pursuits. Over in the West End on Gillespie Street, right next to the place where the Aspen Institute hosts its renowned Ideas Festival, sits a small enclave of buildings where every summer, some of the world’s smartest people quietly contemplate ideas that are often times really big, and really small, at the same time. The Aspen Center for Physics shares its work with the public through the Heinz R. Pagels series of free public lectures which started last Thursday and runs weekly through the end of August. The dates, times and subject matter for these lectures are easily discovered online.
I am no physicist, that’s for sure, but in my relatively simplistic pursuit of understanding, I recently became re-acquainted with one of the cornerstones of quantum mechanics, the Heisenberg Uncertainty Principle. Quantum mechanics is the mathematical study of the motion and interaction of subatomic particles, and subatomic particles are particles of matter smaller than an atom, Heisenberg’s work in the early part of the 20th century shook the foundations of classical physics. He showed how the more certain you become about the precise location of a single particle, the less you know about its momentum, and vice versa.
In demonstrating this theory, he discovered that you cannot ever really know the precise location of a subatomic object. It is the unintuitive, unpredictable behavior of these objects that caused Heisenberg to conclude that they have characteristics of both particles (physical structure and location) and waves (movement, or momentum).
This discovery became known as “wave-particle duality,” the simultaneous reflection of characteristics of both waves and particles. The more that physicists are able to quantify (quantum) the probable location of a particle, the less they are able to know about its probable momentum (wave behavior). The word “probable” is key, because you see, we cannot predict or know either a particle’s location, or its momentum with complete certainty.
Meaning, at the subatomic level, particles are potentially lots of places at the same time. Or maybe they are no place. But that can’t be right — the subatomic particles comprising the superatomic world must be somewhere, otherwise how would we be here? In the early 20th century world of physics, which liked to arrive at absolute answers to foundational questions about reality, this was an earth-shattering, as well as a particle moving, discovery.
One simple experiment demonstrating this principle is to shine a bright light against a wall. Place a dark cover over the light’s lens with only a long thin slit in the middle through which light can pass. As you narrow the slit, restricting the space through which the light can pass, the beam of light reflecting off the wall also becomes narrower, copying the long narrow shape of the slit, but only to a point. When the slit becomes narrow enough, the reflection on the wall starts to diffuse, and spread back out, and rather than appearing as a long narrow, focused reflection of the slit, the reflecting light begins to take the shape of a wave.
When the slit is wider, and the majority of light passes cleanly through the slit without bouncing off the sides of the filter, the light acts more like particles, reflecting predictably off of the wall in the shape of the slit. As the slit narrows and more of the light passing through the filter bounces off the sides of the slit, it becomes harder and harder to predict the reflective location of each individual particle against the wall, and the light’s reflection begins to morph from the shape of the slit to the shape of a wave.
There are lots of sources available for the lay person such as myself to learn about Heisenberg’s principle, ranging from the very simplistic, to the very complex explanations. In reviewing a few of them online, I was inspired to invent the “Menter Uncertainty Principle”, which states as follows:
The more complex the explanation about Heisenberg’s Uncertainty Principle, the more likely it is to be accurate, and the less likely I am to understand any of it.
To me, the uncertainty principle is the physicist’s version of the old saying, “the more I see, the less I know”, except only for subatomic particles, not for things that mere intellectual mortals think about. This saying, of course, reverses to “the less I see the more I know”, which illustrates why learning seems so optional these days. I mean why let a few facts interfere with an invalid but perfectly comfortable world view?
I guess for me it’s intriguing that such a well-known scientific principle might reinforce the notion that knowledge is relative, and outcomes unpredictable. The difference being of course that humans are not subatomic. Physicists can, in fact, measure where we are. So, if you find yourself randomly traveling through time and space, it’s not because of the Heisenberg Uncertainty Principle. On the other hand, when faced with an idea that threatens our world view, unlike the particles of light randomly slamming against the wall as their filtered vision narrows, we can all choose to read and think, and talk to each other, and who knows? Maybe some of us will even learn something.