Robert W. Wood: Photographing the Invisible, Debunking the Incredible

Robert Williams Wood was born in 1868, much too late to be the inventor of photography, an honor shared between Nicéphore Niépce, who produced the first surviving photograph in 1826, and Louis Daguerre, who subsequently collaborated with Niépce and sold the process rights to France after Niépce's death in 1833, who in turn donated them "Free to the World."

What Wood invented was in a way even more spectacular: whereas Niépce and Daguerre merely photographed the visible, Wood was the first to photograph the invisible images obtained via illumination with ultraviolet and infrared light. In the process he invented Wood's glass, which blocks visible light while passing ultraviolet light, thereby making possible today's blacklight lamps obtainable in hobby and novelty stores and used for Halloween parties and indoor blacklit miniature golf links.

Besides photography Wood worked on many other aspects of experimental optics, joining the faculty of Johns Hopkins university in 1901 where he remained for over half a century until his death in 1955.

At the start of his academic career Wood had already developed something of a reputation as a debunker of crackpot science. In 1903 physicist Prosper-René Blondlot, a corresponding member of the French Academy of Science working at the Université de Nancy in the west of Alsace-Lorraine, announced a novel form of radiation that he named N-rays after his institution. Some 120 researchers subsequently confirmed Blondlot's discovery. However a few of the most famous ones such as Lord Kelvin, William Crookes (of the Crookes radiometer one sees spinning in novelty science store windows), Otto Lummer and Heinrich Rubens were inexplicably unable to duplicate Blondlot's results.

Wood was one of these latter, complaining that he'd "wasted a whole morning" trying to duplicate Blondlot's result. The journal Nature, knowing of Wood's predilection for debunking, prevailed on him to sail for France in 1904 and visit Blondlot's lab.

Blondlot's demonstration entailed darkening the room in order to see the effect. Under cover of this darkness Wood removed a crucial prism from the experiment and asked Blondlot whether the effect was still visible, which Blondlot cheerfully confirmed. Wood then covertly replaced a metal file allegedly emitting the N-rays with a wooden object that had been asserted previously by Blondlot not to emit N-rays. Again Blondlot blithely confirmed the presence of N-rays.

Wood published his experiences in Nature and the jig was up for Blondlot. This was a most unfortunate blot on his thus-far highly distinguished career in which Blondlot had been the first to experimentally confirm in 1891, to within a precision of one percent, that radio waves traveled at the speed of light, having earlier confirmed that the speed of electricity in a conductor was not that much slower.

Since N-rays had consumed the scientifically minded public's interest for the preceding year every bit as much the cold fusion debacle fascinated it nearly a century later, Wood's reputation with the public as a debunker of scientific nonsense was cemented forever, quite apart from all his other many accomplishments.

But no great scientist has made his or her professional reputation on debunking, any more than Ghandi can be said to have liberated India via hunger strikes alone. After the N-ray exposure Wood returned to his more staid research into optical phenomena.

It seems however to be human nature to revisit one's more successful ventures whatever their nature. And so it was, perhaps, that in 1909 Wood took on two phenomena that he felt were being improperly explained by his fellow physicists.

One of these was what we call nowadays the greenhouse effect, which even in those days was well understood as the blocking of heat by optically transparent materials. Such materials may be solid, for example glass as first pointed out in 1767 by Swiss physicist Horace de Saussure (great-grandfather of the philosopher Ferdinand de Saussure), and nowadays most forms of transparent plastic such as acrylic and polyethylene, though not TXP which is relatively transparent to infrared. They may also be liquids such as water, and gases such as carbon dioxide, methane, and perfume as shown by noted English physicist John Tyndall during the early 1860s, who invented the now universally used spectrophotometer for this purpose and who remarked that the planet's liquid water would be frozen if the atmosphere consisted only of oxygen and nitrogen, without such infrared-blocking gases as atmospheric water vapor.

The other effect to whose explanation Wood took exception was a far more obscure phenomenon associated with the so-called Talbot effect, in which a diffraction pattern interferes with a finely ruled optical grating to produce a fascinating array of repeated images at various periodicities. In the course of studying the Talbot effect, noted English optical physicist Sir Arthur Schuster had found that the effect disappeared when a mask was introduced from one side of the apparatus but not the other. Schuster offered an explanation for this asymmetry, which as the author of the textbook "An introduction to the theory of optics" several years earlier he was as well qualified as anyone in optical physics to do.

Wood published two papers offering alternative explanations of each of these effects, which he published in respectively the February (#98) and November (#107) issues of the London and Edinburgh Philosophical Magazine, or Phil. Mag. as it is affectionately called.

The first of these, amounting to a page and a half describing a casually performed and documented experiment, is conveniently reproduced at William Connolley's website, to whom I am indebted for drawing my attention to Wood's paper on this subject. The second, a much more carefully reasoned nine-page article, can be seen at Issue 107 of Phil.Mag. via any library with the requisite access privileges.

Wood found no support whatsoever for either of his theories, quite the opposite in fact. Both were repudiated in the same journal, in respectively the July and November issues.

The first was carefully dissected by no less than Charles Greeley Abbot, then director of the Smithsonian Astronomical Observatory and later secretary of the Smithsonian Institute from the onset of the Great Depression to the end of World War II. Abbot's rebuttal, which can be seen here, was more than twice the length of Wood's note, describing the observatory's confirmation of de Saussure's experiment 142 years earlier showing that three glass plates could produce temperatures 18 degrees above boiling in a "hot box," and reconciling theory and experiment for all experiments, both Wood's and the Observatory's, with calculations that the more experimentally oriented Wood had shown no interest in carrying out himself.

The second was more quickly disposed of by Schuster, who merely had to point out in much less space than Wood had needed that the latter had failed to distinguish coherent from incoherent superposition of light. This was an easy mistake to make in those days that would however earn marks off today for any freshman physics student.

Actually it is not entirely true that Wood found no support for his alternative explanations. After nearly a century during which physicists and botanists alike continued to teach that trapping infrared radiation contributed to the heating of greenhouses, climate historians M.D.H. Jones and A. Henderson-Sellers ran across Wood's February 1909 paper and notified the climate research community. Finding Wood's short paper completely plausible as far as they were concerned, climate scientists proceeded from that point on to teach that the greenhouse effect for the atmosphere had nothing to do with greenhouses, which they insisted worked entirely in the manner proposed by Wood, namely by restricting air circulation. Questions about the rigor of Wood's work or its subsequent acceptance or rejection went unraised.

As I wade now through the many Wikipedia pages concerning facets of climate change---the articles, the talk pages where questions about the articles are raised, and the administrative pages where judgment is passed on incivilities---I am struck by a major war and a minor battle.

The war is with the completely understandable vested interests of those protesting any interference with the ongoing addition of carbon dioxide to the atmosphere. Those interests have a fiducial duty to their stockholders to preserve the value of their investments, without which their companies' stock is put at risk.

The less understandable battle is between the climate scientists who band together to defend themselves from these vested interests and the physicists and mathematicians who routinely make minor corrections to the physics and mathematics of everyone including their own, not out of any sense of fiducial duty but simply from a distaste for inaccuracy in science.

In so banding together against the vested commercial interests, the climate scientists have developed a mentality in which any criticism of their work, whether motivated by fiducial duty or scientific rigor, is perceived as an assault on their integrity as climate scientists.

My concern is that the failure of the climate research community to draw this distinction puts their credibility at risk and makes them that much more vulnerable to the energy industry and its stockholders, whose complaints about climate research have been increasing both monotonically and shrilly for quite some time now.

When the physicists and mathematicians cannot get a fair hearing from the climate scientists, the future of the planet is put at serious risk.