 by Preston MacDougall April 14, 2005
April 18th marks the fiftieth anniversary of his death, and an Austrian physicist has planned a day-long, once around the world, wave of light to salute the man who quantized it. To honor his life, a committee of physicists has compiled year-long plans for 2005, the World Year of Physics and the centennial of his annus mirabilis, or miracle year. In 1905, Einstein, a patent clerk in Switzerland, must have been burning the midnight oil while working on his doctoral dissertation for the University of Zurich. It was titled "A New Determination of Molecular Dimensions". His dissertation was eventually published in the premier physics journal of the time, Annalen der Physik, but not until 1906. I feel confident speculating about his night-life, because he then submitted four additional manuscripts (without the aid of White Out, let alone a word processor), all of which were published in 1905. The impact of these ideas outshines that of any patent issued before or since, and this is reflected in the ongoing evolution of his status, from icon to myth. The equation commonly associated with Einstein, whether on TV or T-shirts, has become something of an icon itself. It was introduced, rather matter-of-factly, in a three-page supplement to a preceding paper titled "On the electrodynamics of moving bodies", better known as his special theory of relativity. In this theory Einstein really made some waves. Laws being laws, one expects them to be upheld, especially when they are "universal". The trouble with Newton's Universal Law of Gravitation, however, was that it wasn't universal enough. It depended on whether the observer and the observed were at rest, or moving. Experiments say otherwise, particularly when the motion approaches the speed of light. Einstein resolved the discrepancy by famously proposing that "everything is relative." This phrase is another icon, and may not mean much to you. But if you have ever wondered "Where did all the time go?," Einstein took all of it in 1905. He didn't eliminate time, but he said that it was elastically interwoven with the three dimensions of space. There is only spacetime, which may, or may not, be unimaginably tightly-packed balls of string. It gets weirder. Also in 1905, Einstein resolved another discrepancy between our familiar conception of nature, this time of light itself, and experiments on the interaction of light and matter. Again so-called "classical laws" had reached their limit. By treating light as a wave, classical laws of optics gave us the tools to design cameras, and the insight to understand rainbows. To follow Einstein's style and use a made-up example, or gedanken experiment, classical laws could explain how light, entering my eye, travels through the cornea, the lens and the vitreous cavity to form an image on the retina, but not how the molecules that make up the rods and cones in the retina convert light of different wavelengths into electrical signals that can be interpreted by my brain as a colorful image, such as a rainbow. Einstein proposed that light is composed of energy quanta, and that these "atoms" of pure energy can behave both as a wave, that can be bent by a lens, and as a particle, that may fit one molecule in the retina, but not another. It all depends. Long after 1905, it became the orthodox interpretation of quantum theory that this uncertainty in the nature of light, and all other submicroscopic particles, is embedded, and cannot be removed by closer inspection with more advanced technology, such as lasers (which, by the way, are another example of Einstein's predictions bearing fruit). In fact, the mere act of observing changes reality. This is where Einstein got spooked. He famously chided the faithful: "Do you really think the Moon is not there when you're not looking?" His remaining 1905 paper sought to heal a schism in the physics community over the reality of atoms, which chemists had been happily tinkering with for the preceding century. He predicted the effect that randomly colliding sugar molecules, dissolved and invisible even with microscopes, would have on observable particles, such as pollen. When these statistical predictions were later shown to be quite accurate, most physicists concluded that chemists weren't simply imagining things. Beginning on the evening of Monday, April 18, human particles around the globe will shine a light at their instructed times, forming a wave of light to honor one who shone so brightly.
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