Tag Archives: Solvay Conference

In Living Color

by Shane L. Larson

I don’t often talk to people for great lengths of time on airplanes. I’m kind of shy around people I don’t know.  But on a recent long flight home from the East Coast, I found myself sitting next to a wonderful woman, 75 years young, and we talked for the entire 5 hour flight.  Stefi was a gold- and silversmith from Vermont, and a German immigrant.  Our conversation ranged from the art of jewelry making, to winters in Vermont, to her grandchildren whom she was going to visit in Utah.

But at some point, the conversation strayed to her childhood in Berlin, where she lived as a young girl during the closing days of World War II.  There, sitting right next to me on the plane, was a living, breathing soul who had lived through the heart of World War II.  Not a soldier, not a support person who worked the fronts or factory lines, but a person caught in the middle of the war itself. From vivid memory, she recounted tales of what she saw, living huddled in a basement with her mother and sisters as the end of the War approached.  She was there as the Red Army advanced toward the Battle of Berlin, and saw the Russian occupation of the city.  In her mind’s eye, she could see it all in living color again.  But my vision was only pale black and white; the only images of the War that anyone in my generation has ever seen are stark black and white images.

In the days after the flight, long after Stefi and I had gone back to our respective lives, I was thinking about the differences between memory and historical record. In physics, we have similar historical records of our distant past, also preserved in stark, black and white images.  One of the most famous images in my field, is of the Fifth Solvay Conference on Electrons and Photons, held in the city of Brussels in October of 1927.  The reason this particular conference is so well known is the iconic black and white photograph captured of the participants.

The participants in the 1927 Solvay Conference on Electrons and Photons, in Brussels.

Scanning through the photograph, or running your finger down a list of names, one encounters names that are completely synonymous with the development of modern physics. Of the 29 participants, 17 went on to win Nobel Prizes; included among them is Marie Curie, the only person who has ever won two Nobel Prizes in different scientific disciplines!  This single image captured almost all of the architects of modern physics.  These are the minds that seeded the genesis of our modern technological world.  The conference itself has passed into the folklore of our civilization, as this was the place that Einstein expressed his famous utterance, “God does not play dice!”  Neils Bohr famously replied, “Einstein, stop telling God what to do!”

For many of us in this game called physics, the people in this image are icons, idols, and inspirations.  We know their names, we know their stories, and we can pick them out of pictures as easily as we can pick friends out of modern pictures.  But always in the dull and muted grain of black and white photographs. I’ve never met a person (that I know of) that met Einstein, or Bohr, or Heisenberg, or Curie; no one to recount for me the vivid colors of these great minds in their living flesh.

It is an interesting fact that all of these historical images are black and white. Color photography was first demonstrated some 66 years earlier at the suggestion of another great mind in physics, James Clerk Maxwell.

The first color photograph ever taken, by Thomas Sutton in 1861 at the behest of James Clerk Maxwell. The image is of a tartan ribbon, captured by a three-color projection technique.

The process worked by taking three black and white pictures through colored filters — red, green and blue — then reprojecting the black and white pictures through the filters again to produce a colored image.  This is more or less the same principle that is used today to generate color on TV screens and computer monitors.  If you look very closely at the screen you are reading this on, you will see that the pixels are all combinations of red, green and blue.

An example of RGB image construction. The three black and white images on the left were taken through Red (top), Blue (middle) and Green (bottom) filters. When recombined through those colored filters, they produce a full color image (right).

The famous tartan picture was generated for a lecture on color that Maxwell was giving.  Maxwell’s interest in light and color derived from the reason he is famous  — Maxwell was the first person to understand that several different physical phenomena in electricity and magnetism are linked together.  His unification of the two is called electromagnetism.  One consequence of that unification was the discovery that the agent of electromagnetic phenomena is light.  Today, the four equations describing electromagnetism are called the Maxwell Equations.

As with all things in science, the elation of discovery is always accompanied by new mysteries and new questions. One of the central realizations of electromagnetism was that light is a wave, and that the properties of the wave (the wavelength, or the frequency) define what our eyes perceive as color.

The electromagnetic spectrum — light in all its varieties, illustrated in the many different ways that scientists describe the properties of a specific kind (or “color”) of light. What your eye can see is visible light, the small rainbow band in the middle.

The realization that the color of light could be defined by a measurable property was a tremendous leap forward in human understanding of the world around us, and it naturally led to the idea and discovery that there are “colors” of light that our eyes cannot see!  Those kinds of light have often familiar names — radio light, microwave light, infrared light, ultraviolet light, and x-ray light.  But knowing of the existence of a thing (“Look! Infrared light!”) and being able to measure its properties (“This radio wave has a wavelength of 21 centimeters.”) are not the same thing as knowing why something exists.  How Nature made all the different kinds of light and why, were mysteries that would not be solved until the early Twentieth Century, by many of the great minds who attended the Solvay Conference.

Einstein famously discovered the idea that there is a Universal speed limit — nothing can travel faster than the speed of light in the vacuum of space.  Max Planck postulated that on microscopic levels, energy is delivered in discreet packets called quanta — in the case of light, those quanta are called photons.  Neils Bohr used the Planck hypothesis to explain how atoms generate discrete spectral lines — a chromatic fingerprint that uniquely identify each of the individual atoms on the periodic table. Marie Curie investigated the nature of x-ray emission from uranium, and was the first to postulate that the x-rays came from the atoms themselves — this was a fundamental insight that went against the long held assumption that atoms were indivisible, leading to the first modern understandings of radioactivity.  Louis deBroglie came to the realization that on the scales of fundamental particles, objects can behave and both waves and particles — this “duality” of character highlights the strangeness of the quantum world and is far outside our normal everyday experiences on the scales of waffles, Volkswagens and house sparrows.  Erwin Schroedinger pushed the quantum hypothesis on very general grounds, developing a mathematical equation (which now bears his name) that gives us predictive power about the outcome of experiments on the scales of the atomic world — his famous gedanken experiment with a cat in a box with a vial of cyanide captures the mysterious differences in “knowledge” between the macroscopic and microscopic worlds.  And so on.

The visible light fingerprints (“atomic spectra”) of all the known chemical elements. Each atom emits and absorbs these unique sets of colors, making it possible to identify them.

It is fashionable in today’s political climate to question the usefulness of scientific investigations, and to ask what benefit (economic or otherwise) that basic research investment begets society. Looking at the picture of the Solvay participants and considering their contributions to the knowledge of civilization one very rapidly comes to the realization that their investigations changed the world; in a way, their contemplations made the world we know today.  The discovery of radiation led directly to radiological medicine, radiation sterilization, nuclear power, and nuclear weapons.  The behaviour of atoms and their interactions with one another to generate light leads to lasers, LED flashlights, cool running lights under your car or skateboard, and the pixels in the computer screen you are reading from at this very moment. The quantum mechanical beahviour of the microscopic world, and our ability to understand that behaviour leads directly to integrated circuits and every modern electronic device you have ever seen.  That more than anything else should knock your sense of timescales off kilter; at the time quantum mechanics was invented, computers were mechanical devices, and no one had ever imagined building a “chip.”  The first integrated circuit wasn’t invented until 1958, when Jack Kilby at Texas Instruments built the first working example, 31 years after the Solvay Conference; the first computer using integrated circuits that you could own didn’t appear until the 1970s, and smartphones showed up in the early 2000’s.  The economic powerhouses of Apple, Microsoft, Hewlett-Packard, Dell, and all the rest, are founded on basic research that was done in the 1920s and 1930s.

Which brings me back to where we started — pictures from those bygone days.  After the first tri-color image of Maxwell’s tartan, the development of color photography progressed slowly. The 1908 Nobel Prize in Physics was awarded for an early color emulsion for photography, but the first successful color film did not emerge until Kodak created their famous Kodachrome brand in 1935.  Even so, color photography was much more expensive than black and white photography, and was not widely adopted until the late 1950s.  As a result, our history is dominated by grainy, black and white images.

So it was a great surprise last week when the Solvay Conference picture passed by in one of my friend’s Facebook stream, in color!  Quite unexpectedly, it knocked my socks off. I spent a good long time just staring at it.  Never before had I known of the flash of blue in Marie Curie’s scarf, Einstein’s psychedelic tie, or Schroedinger’s red bow tie (is Pauli looking at that tie with envy?).  But more importantly, the people were in color, as plain as if they were sitting across the table from me. It’s a weird twist of psychology that that burst of color, soft skin tones of human flesh, suddenly made these icons all the more real to me.

Colorized version of the famous 1927 portrait of the Solvay Conference participants [colorized version by Sanna Dullaway].

No longer just names and grainy pictures from history books, but rather remarkable minds from our common scientific heritage, seen for the first time in living color by a generation of scientists long separated from them.