This guest post from A. Douglas Stone is part of our celebration of all things Einstein, pi, and, of course, pie this week. For more articles, please click here. Please join Prof. Stone at the Princeton Public Library on March 14 at 6 PM for a lecture about Einstein’s quantum breakthroughs.
Thanks to RealClearScience for posting about this article!!
Albert Einstein never cared too much about receiving awards and honors, and that included the Nobel Prizes, which were established in 1901, at roughly the same time as Einstein was beginning his research career in physics. In 1905, at the age of 25, Einstein began his ascent to scientific pre-eminence and world-wide fame with his proposal of the Special Theory of Relativity, as well as a “revolutionary” paper on the particulate properties of light, his foundational work on molecular (“Brownian”) motion, and finally his famous equation, E = mc2. In 1910, he was first nominated for the Prize and was nominated many times subsequently, usually by multiple physicists, until he finally won the 1921 Prize (awarded in 1922). Surprisingly, he did not win for his most famous achievement, Relativity Theory, which was still deemed too speculative and uncertain to endorse with the Prize. Instead, he won for his 1905 proposal of the law of the photoelectric effect—empirically verified in the following decade by Robert Millikan—and for general “services to theoretical physics.” It was a political decision by the Nobel committee; Einstein was so renowned that their failure to select him had become an embarrassment to the Nobel institution. But this highly conservative organization could find no part of his brilliant portfolio that they either understood or trusted sufficiently to name specifically, except for this relatively minor implication of his 1905 paper on particles of light. The final irony in this selection was that, among the many controversial theories that Einstein had proposed in the previous seventeen years, the only one not accepted by almost all of the leading theoretical physicists of the time was precisely his theory of light quanta (or photons), which he had used to find the law of the photoelectric effect!
In keeping with his relative indifference to such honors, Einstein declined to attend the award ceremony, because he had previously committed to a lengthy trip to Japan at that time and didn’t feel it was fair to his hosts to cancel it. Moreover, when the Prize was officially announced and the news reached him during his long voyage to Japan, he neglected to even mention the Prize in the travel diary he was keeping. He had taken one practical note of it however, in advance. When he divorced his first wife, Mileva Maric in 1919, he agreed to transfer to her the full prize money, a substantial sum, in the form of a Trust for the benefit of her and his sons, should he eventually win.
However, while Einstein himself barely dwelt at all on this honor, it is an interesting exercise to ask how many distinct breakthroughs Einstein made during his productive research career, spanning primarily the years 1905 to 1925, that could be judged of Nobel caliber, when placed in historical context and evaluated by the standards of subsequent Nobel Prize awards. Admittedly, this analysis has a bit in common with fantasy sports, in which athletes are judged and ranked by their statistical achievements and arguments are made about who was the GOAT (“greatest of all time”). Well, why not spend a few pages on this guilty pleasure, at least partly in the service of illuminating the achievements of this historic genius, even if Einstein would not have approved?
Let’s start with the Prize he did receive, which was absolutely deserved, if the committee had had the courage to write the citation, “for his proposal of the existence of light quanta.” The law of the photoelectric effect, which they cited, only makes sense if light behaves like a particle in some important respects, and that is what he proposed in 1905. This proposal came at a time when the wave theory of light was absolutely triumphant and was even enshrined in a critical technology: radio. Not a single physicist in the world was thinking along similar lines as Einstein, nor were all of the important theorists convinced by his arguments for two more decades. Nonetheless, the photon concept was unambiguously confirmed in experiments by 1925, and now is considered the paradigm for our modern quantum theory of force-carrying particles. It is the first in a family of particles known as bosons, most recently augmented by the (Nobel-winning) discovery of the Higgs particle. So the photon is a Nobel slam dunk.
We can move next to two more “no-brainers,” the two theories of relativity, the Special Theory, proposed in 1905, and the General Theory, germinated in 1907 and completed in 1915. These are quite distinct contributions. The Special Theory introduced the Principle of Relativity, that the law of physics must all be the same for bodies in uniform relative motion. An amazing implication of this statement is that time does not elapse uniformly, independent of the motion of observers, but rather that the time interval between events depends on the state of relative motion of the observer. Einstein was the first to understand and explain this radical notion, which is now well-verified by direct experiments. Moreover, Einstein’s concept of “relativistic invariance” is built into our theory of the elementary particles, and so it has had a profound impact on fundamental physics. However, here it must be noted that the equations of Special Relativity were first written down by Hendrik Lorentz, the great Dutch physicist whom Einstein admired the most of all his contemporaries. Lorentz just failed to give them the radical interpretation with which Einstein endowed them; he also failed to notice that they implied that energy and mass were interchangeable: E = mc2. There are also a few votes out there for the French mathematician, Henri Poincare, who enunciated the Principle of Relativity before Einstein, but I can’t put him in the same category as Lorentz with regard to this debate. Einstein would have been happy to share Special Relativity with Lorentz, so let’s split this one 50-50 between the two.
General Relativity on the other hand is all Albert. Like the photon, no one on the planet even had an inkling of this idea before Einstein. Einstein realized that the question of the relativity of motion was tied up with the theory of Gravity: that uniform acceleration (e.g. in an elevator in empty space) was indistinguishable from the effect of gravity on the surface of a planet. It gave one the same sense of weight. From this simple seed of an idea arose arguably the most beautiful and mathematically profound theory in all of physics, Einstein’s Field Equations, which predict that matter curves space and that the geometry of our universe is non-Euclidean in general. The theory underlies modern cosmology and has been verified in great detail by multiple heroic and diverse experiments. The first big experiment, which measured the deflection of starlight as it passed by the sun during a total eclipse, is what made Einstein a worldwide celebrity. This one is probably worth two Nobel prizes, but let’s just mark it down for one.
Here we exhaust what most working physicists would immediately recognize as Einstein’s works of genius, and we’re only at 2.5 Nobels. But it is a remarkable fact that Einstein’s work on early atomic theory, what we now call quantum theory, is vastly under-rated. This is partially because Einstein himself downplayed it due to his rejection of the final version of the theory, which he dismissed with the famous phrase, “God does not play dice.” But if one looks at what he actually did, the Nobels keep piling up.
The modern theory of the atom, quantum theory, began in 1900 with the work of the German physicist, Max Planck, who, in what he called “an act of desperation,” introduced into physics a radical notion, quantization of energy. Or so the textbooks say. This is the idea that when energy is exchanged between atoms and radiation (e.g. light), it can only happen in discrete chunks, like a parking meter that only accepts quarters. This idea turns out to be central to modern atomic physics, but Planck didn’t really say this in his work. He said something much more provisional and ambiguous. It was Einstein in his 1905 paper—but then much more clearly in a follow-up paper on the vibrations of atoms in solids in 1907—who really stated the modern principle. It is not clear if Planck himself accepted it fully even a decade after his seminal work (although he was given credit for it by the Nobel Prize committee in 1918). In contrast, Einstein boldly applied it to the mechanical motion of atoms, even when they are not exchanging energy with radiation, and stated clearly the need for a quantized mechanics. So despite the textbooks, Einstein clearly should have shared Planck’s Nobel Prize for the principle of quantization of energy. We are up to 3.0 Nobels for Big Al.
The next one in line is rarely mentioned. After Einstein proposed his particulate theory of light in 1905, he did not adopt the view that light was simply made of particles in the ordinary sense of a localized chunk of matter, like a grain of sand. Instead, he was well aware that light interfered with itself in a similar manner to water waves (a peak can cancel a trough, leading to no wave). In 1909, he came up with a mathematical proof that the particle and wave properties were present in one formula that described the fluctuations of the intensity of light. Hence, he announced that the next era of theoretical physics would see a “fusion” of the particle and wave pictures into a unified theory. This is exactly what happened, but it took fourteen years for the next advance and another three (1926) for it all to fall into place. In 1923, the French physicist Louis de Broglie hypothesized that electrons, which have mass (unlike light) and were always previously conceived of as particles, actually had wavelike properties similar to light. He freely admitted his debt to Einstein for this idea, but when he got the Nobel Prize for “wave-particle” duality in 1929, it was not shared. But it should have been. Another half for Albert, at 3.5 and counting.
From 1911 to 1915 Einstein took a vacation from the quantum to invent General Relativity, which we have already counted, so his next big thing was in 1916 (he didn’t leave a lot of dead time in those days). That was three years after Niels Bohr introduced his “solar system” model of the atom, where the electrons could only travel in certain “allowed orbits” with quantized energy. Einstein went back to thinking about how atoms would absorb light, with the benefit of Bohr’s picture. He realized that once an atom had absorbed some light, it would eventually give that light energy back by a process called spontaneous emission. Without any particular event to cause it, the electron would jump down to a lower energy orbit, emitting a photon. This was the first time that it was proposed that the theory of atoms had such random, uncaused events, a notion that became a second pillar of quantum theory. In addition, he stated that sometimes there was causal emission, that the imposition of more light could cause the atom to release its absorbed light energy in a process called stimulated emission. Forty-four years later, physicists invented a device that uses this principle to produce the purest and most powerful light sources in nature, the LASER (Light Amplified by Stimulated Emission of Radiation). The principles of spontaneous and stimulated emission introduced by Einstein underlie the modern quantum theory of light. One full Prize please—now at 4.5.
After that 1916-1917 work, Einstein had some health problems and became involved in political and social issues for a while, leading to a Nobel batting slump for a few years. (He did still collect some hits, like the prediction of gravitational waves (a double) and the first paper on cosmology and the geometry of the Universe using General Relativity (a triple)). But he came out of his slump with a vengeance in 1924 when he received a paper out of the blue from an unknown Indian, physicist Satyendranath Bose. It was yet another paper about particles of light, and although Bose did not state his revolutionary idea very clearly, reading between the lines, Einstein detected a completely new principle of quantum theory, the idea that all fundamental particles are indistinguishable. This is the standard terminology in physics, but it is actually very misleading. Here, indistinguishability is not the idea that humans can’t tell two photons apart (like identical twins); it is the idea that Nature can’t tell them apart, and in a real sense interchanging the two photons doesn’t count as a different state of light.
When Bose applied this principle to light he didn’t get anything radically new; it was just a different way of thinking about Planck’s original discovery in 1900. But Einstein then took the principle and applied it to atoms for the very first time, with amazing results. He discovered that a simple gas of atoms, if cooled down sufficiently, would cease to obey all the laws that physicists and chemist had discovered for gases over the centuries, and to which no exception had ever been found. Instead, all gases should behave like a weird liquid or super-molecule known as a Bose-Einstein condensate. But remember, Bose had no clue this would happen; he didn’t even try to apply his principle to atoms. It turns out that Einstein condensation underlies some of the most dramatic quantum effects, such as superconductivity, which is needed to make the magnets in MRI machines and has been the basis for five Nobel Prizes. No knowledgeable physicist would dispute that Einstein deserved a full Nobel Prize for this discovery, but I am sure that Einstein would have wanted to share it with Bose (who never did receive the Prize).
So we are at 5.0 “units” of Nobel Prize but seven trips to Stockholm. And this leaves out other arguably Nobel-caliber achievements (Brownian motion as well as the Einstein-Podolsky-Rosen effect, which underlies modern quantum information physics). And wait a minute—when someone shares the Nobel Prize do we refer to them as a “half- Laureate”? No way. Even scientists who get a “measly” third of a Prize are Nobel Laureates for life. Thus by the standard we apply to normal humans, Einstein deserved at least seven Nobel Prizes. So next time you make your fantasy scientist draft, you know who to take at number one.
A. Douglas Stone is author of Einstein and the Quantum: The Quest of The Valiant Swabian.