Albert Einstein

The clerk who rewrote physics

In 1905, Albert Einstein was a twenty-six year old patent clerk in Bern, third-class examiner, no professorship, no laboratory. In a single calendar year he submitted four papers to Annalen der Physik that each, on their own, would have justified a career. Together they are remembered as the annus mirabilis.

The four were four assaults on four different problems. The March paper proposed that light came in discrete packets and used the idea to explain the photoelectric effect. The May paper used the random walk of pollen grains to settle the long-standing question of whether atoms were real. The June paper laid out the special theory of relativity, dissolving Newtonian absolute time and the luminiferous ether in one move. The September paper, almost an afterthought, derived E = mc² as a three-page corollary. He wrote them while stamping patents.

The leap nobody else would take

The photoelectric paper is the one that matters for this story. Planck in 1900 had been forced to quantize the energy of oscillators in the walls of a cavity, but he treated the move as a mathematical trick to make a sum converge. The radiation itself, he still believed, was a continuous classical wave.

Einstein refused the compromise. If the atoms in the wall could only emit in lumps of size hν, then perhaps the light itself was also lumpy. He proposed that a beam of frequency ν was a stream of discrete quanta, each carrying energy hν, and showed that this single assumption explained every puzzling feature of the photoelectric experiments: the threshold frequency, the linear dependence of electron energy on frequency, the independence from intensity.

It was the first time anyone had quantized a field. Planck called the idea reckless. Even a decade later, when Einstein was nominated to the Prussian Academy, his sponsors asked that his light-quantum work not be held against him.

Throughout his life, Einstein published hundreds of books and articles. He published more than 300 scientific papers and 150 non-scientific ones. On 5 December 2014, universities and archives announced the release of Einstein's papers, comprising more than 30,000 unique documents. In addition to the work he did by himself, he also collaborated with other scientists on additional projects, including the Bose–Einstein statistics, the Einstein refrigerator and others.

The Nobel Prize that wasn’t for relativity

Einstein received the 1921 Nobel Prize in Physics, but the citation named “his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect.” Relativity was not mentioned. Most people who know one fact about Einstein know it as “the relativity guy,” and most are surprised that the committee gave him the prize for the other thing.

There were two reasons. Relativity was still controversial, both philosophically and politically (Philipp Lenard’s “Aryan physics” faction was attacking it). And Robert Millikan’s experimental confirmation of the photoelectric law in 1916, after a decade of trying to prove Einstein wrong, had made the photon impossible to ignore. The committee chose the safer trophy.

”God does not play dice”

By the late 1920s the quantum mechanics Einstein had helped found had grown into something he could no longer recognise. Heisenberg’s uncertainty principle, Born’s probabilistic interpretation of the wavefunction, and Bohr’s complementarity together insisted that nature itself, not just our knowledge of it, was irreducibly statistical.

Einstein rejected this. A 1926 letter to Max Born contains the famous line: “He does not throw dice.” He spent thirty years arguing, mostly with Bohr, that quantum mechanics had to be incomplete: that beneath the probabilities sat hidden variables.

The Bohr-Einstein debates at the 1927 and 1930 Solvay conferences are among the most carefully recorded arguments in the history of science. Einstein would arrive each morning with a thought experiment designed to break the uncertainty principle. Bohr, after a sleepless night, would arrive the next with the resolution, often invoking Einstein’s own general relativity against him. Bohr won every round. Einstein was never persuaded.

EPR and the long shadow

In 1935 Einstein, with Boris Podolsky and Nathan Rosen, published Can Quantum-Mechanical Description of Physical Reality Be Considered Complete? The paper constructed a pair of entangled particles and argued that quantum mechanics, applied to them, led to consequences so strange that the theory must be missing something. Bohr replied within months, defending the orthodox view.

For thirty years EPR was treated as a philosophical curiosity. Then in 1964 John Bell turned it into a testable inequality. The experiments that followed (Aspect in 1982, Zeilinger in the 1990s) sided with quantum mechanics and against Einstein’s intuition. Nature really does play dice. But the EPR paper had named the phenomenon (entanglement) and forced the field to take it seriously. It is the cornerstone of quantum information science today.

Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist best known for developing the theory of relativity. Einstein also made important contributions to quantum theory. His mass–energy equivalence formula E = mc2]], which arises from special relativity, has been called "the world's most famous equation". He received the 1921 Nobel Prize in Physics for "his services to theoretical physics, and especially for his…

Flight, Princeton, the bomb

When Hitler came to power in January 1933, Einstein was visiting the United States. He never returned to Germany. His Berlin apartment was raided within weeks and the Nazis put a bounty on his head. He settled at the newly founded Institute for Advanced Study in Princeton, where he remained until his death in 1955.

In 1939 he co-signed the Szilárd letter to Roosevelt warning that Nazi Germany might be building a nuclear weapon. The letter helped catalyse the Manhattan Project, though Einstein himself was denied a security clearance and never worked on the bomb. After Hiroshima he became one of the loudest voices for disarmament. His last public act, days before his death, was signing the Russell-Einstein Manifesto calling for the abolition of war.

The paradox

Einstein is the founder of quantum mechanics who refused to live in the house he built. He gave the field its first quantum of a field, its first decisive break from classical continuity, and then spent half his life trying to prove the building structurally unsound. He was wrong about that. But his objections sharpened the theory in ways its more comfortable practitioners would not have. The questions he posed in 1935 are the ones being answered, eighty years later, in every quantum computer laboratory on earth.