Faraday’s “Intuitive” Calculus: A lecture at SJCA
| in: Biology
In a stimulating and spell-binding lecture on a number of papers by Michael Faraday Friday, Ryan Tweney, emeritus professor of psychology at Bowling Green State University, led the audience in an exciting journey covering acoustic surprises, optical illusions, excruciating experiments and thrilling conjecture. It was difficult to gather, except on rare occasions of lucidity, until the end of the talk what the connection was between the seemingly disparate phenomena being related. I’ll relate these parts in summary, before exploring the conclusions suggested.
Since the lecture was at St. John’s College, an introduction to Faraday’s work, and to the man himself, was unnecessary. Nevertheless, first a review of contemporary work involving field theory, as well as experiments involving color, light, and matter, was given. Next three papers by Faraday were examined. The first two were published in 1831, early on in Faraday’s career, before he had gained widespread fame through his work on field theory. The final paper was delivered in 1857, near the end of Faraday’s working years.
“On a curious acoustic phenomenon”, the first of the 1831 papers, was an exploration and explanation of what I find to be a very peculiar and unexpected occurrence. If a fine powder, or alternately sand, is placed on a flat metal plate which is then bowed, the particles collect into particular and constant geometric arrangements! When I first saw them, I was reminded of some of the visual patterns displayed in the first sections of Disney’s 1940 Fantasia. The lines and curves on the plates quite closely resembled the bright colors splashed in representation of sound waves from the percussion instruments as the orchestra was warming up. Through a serious of ingenious experiments, Faraday attempted to explain why such patterns occur. His approach relied upon the effects of areas on the plate which experienced more and less vibration due to the bowing. The effects of these influences were made clear by extending the experiment to additional plates, whereby particles were observed to migrate from the placid to the more active plate or vice versa (depending on their granularity, oddly enough!). The image Faraday used by the end was that of a grid of vector forces, causing the curious patterns to be made manifest.
Next a paper entitled “On a curious optical phenomenon” was presented. This examined the patterns that appear to emerge when two structures such as carriage wheels or cogs are rotated, placed one behind the other, relative to a human observer. Because of the delays in human optical response, darker and lighter bands appear in certain places where the two structures overlap over time. A geometrical illustration attempting to explain this effect was an admirable act of abstraction. This point was made much of by Professor Tweney throughout the lecture. He praised Faraday for his lifelong bridging of the physical and the invisible by means of the infinitesimal. His earlier drawings are actual copies of iron filings about magnets. Later, these shift into the more mathematical “lines of force”. By the end of his life, after the influence of James Clerk Maxwell, his illustrations were completely abstract, consisting of single circles representing electric and magnetic force.
The final experimental work imparted involved techniques that Faraday mastered without peer. Even modern scientific facilities have only managed ugly replicas of this work. What motivated Faraday so much? When light is reflected off large masses of gold, it appears, well, gold-colored to our eyes. But when light shines through extremely thin sections of gold, one instead observes a green light on the opposite side! This conundrum pestered Faraday throughout his career. He eventually referred to it as his “old problem”, and devoted substantial experimental energy and time to its solution. For quite some time, historians didn’t fully appreciate his work during this period, as all that was left were his voluminous journals. While otherwise quite illuminating, those of this period were “confusing”. It was in fact Professor Tweney that found the key to understanding his work. In a museum reproducing Faraday’s electromagnetic lab, a number of boxes discreetly sat on a shelf, left unexamined until 1972. Professor Tweney asked one of historians about their contents, and found no one seemed to know. Upon examining them, it was found they contained hundreds of microscopic slides of gold specimens, with numbers corresponding to the “confusing” journal! Faraday was able to manufacture large quantities of gold leaf, far thinner than commercial quality leaf, even of today.
Perhaps to the lecture’s detriment, but much to my curiosity’s delight, Professor Tweney explained the process of its manufacture by Faraday, as well as his efforts to reproduce this. It involved forming gold chloride, which was placed in a watch glass and covered with a glass Petri dish. The remaining phosphorus from its creation reacted with the atmospheric oxygen, after which the extremely thin layers of gold were deposited on the bottom of the Petri dish. This was then lifted off and placed in a bowl of water, in which the gold layers would float off and could be placed on a slide. These deposits were then subjected to a wide range of stimuli, such as heat, mechanical, and chemical pressures. The effects of these changes on transmitted and reflected light were then carefully noted. A number of other amazing extensions of these experiments were also explored. Some historians consider this to be the first beginnings of nanoscience, especially in the accidental creation of gold colloids, another first by Faraday.
Now after all this, you are likely wondering, as was the audience, what the connection was between these various curiosities. Faraday’s conclusion was that they all illustrated that effects such as color and the patterns of particles aren’t due to properties inherent in the objects themselves, but were only made manifest when two or more of the objects acted in concert. In other words, the idea of force was behind these separate occurrences. By this time, Faraday and Maxwell’s work on field theory was fully blossomed. While time did not permit these conclusions to be even partially explored or proven, my curiosity at least was piqued.
One application which I considered after the lecture concerned artificial intelligence, specifically the development of artificial means of visual recongition and understanding. If sight, and a deeper understanding of characteristics such as color and sound, were emergent phenomena, requiring more than an elementary understanding of the components at work, but also their behavior in combination, then this might provide valuable guidance in programmatic manifestations of human visual cognition, even a beginning of an understand of the world as humans experience it. But for now, I too lack time to explore my conclusions.
Posted: 12 Apr 2009 08:24 am by Samuel Huckins 0 comments
