The Dice Letter at 100: How One Sentence Shaped a Century of Physics

On 4 December 1926, Albert Einstein sent his friend Max Born a short letter that began with news about a play. Then he turned to the new quantum theory. He was convinced, he wrote, that “the Old One” does not throw dice. That sentence became the banner for a hundred-year argument: is chance built into nature, or does quantum physics leave something out?

Here is how one sentence shaped a century. Einstein’s doubt pushed others to sharpen the question until it could be tested. Experiments began in 1972, and by 2015 they had closed the main loopholes. The results went against the kind of hidden, local explanation Einstein hoped for, and in 2022 three of the experimenters shared the Nobel Prize in Physics. What those results mean for chance itself is still argued.

What had Max Born proposed?

In 1925 and 1926, physicists built a new theory of atoms called quantum mechanics. In 1926 Erwin Schrödinger wrote an equation for a “wave function,” a mathematical wave that goes with each particle. But what was this wave? That same year, Max Born, a professor at the University of Göttingen in Germany, gave the answer that stuck. The wave does not show where the particle is. Its size, squared, gives the probability of finding the particle in each place when you look (Stanford Encyclopedia of Philosophy).

Think of a forecast that says “70 percent chance of rain.” We usually assume the forecast is fuzzy only because nobody knows every detail of the air. Born’s rule hinted at something stranger. For a single atom, the odds might be the whole story. The theory could predict patterns over many events, but not always the result of one. Born later shared the 1954 Nobel Prize in Physics, cited especially for this “statistical interpretation of the wavefunction” (NobelPrize.org).

What did Einstein actually write on 4 December 1926?

The letter opens with news about a play by Born’s wife, Hedwig. Einstein assured Born that his son-in-law, the writer and critic Rudolf Kayser, would read it (Physics Today). Then he turned to physics. He called quantum mechanics impressive, but said an inner voice told him it was not yet “der wahre Jakob.” That German idiom means “the real thing.” The theory, he went on, brings us hardly any closer to “dem Geheimnis des Alten,” the secret of the Old One. Then came the line that became famous:

“Jedenfalls bin ich überzeugt, daß der nicht würfelt.”

In our own translation: “At any rate, I am convinced that He does not throw dice.” After one more short remark about quantum waves, the letter turns to Einstein’s own work on general relativity.

Two details matter. First, “der Alte,” the Old One, was Einstein’s playful name for God, which for him meant the deep order of nature. He did not mean a personal God who steers human lives. In 1929 he told a New York rabbi that he believed in Spinoza’s God, revealed in the lawful harmony of all that exists, not a God concerned with human fates and actions (Jewish Telegraphic Agency). Second, the little word “der” in the famous line just points back to the Old One, like “that one” or “he.” So the letter does not literally say “God does not play dice.” That short form is a later compression, though Einstein did use God-language for the same idea on other occasions. Our article on what Einstein meant explores his view.

Born took the letter hard. He later wrote that Einstein had rejected the theory by appeal to an “inner voice,” not for a definite reason, and that the split came from a deep difference in philosophical attitude (Physics Today).

How did one sentence grow into a thirty-year debate?

Less than a year later, from 24 to 29 October 1927, leading physicists met in Brussels for the Fifth Solvay Conference, on electrons and photons (conference proceedings). The Danish physicist Niels Bohr, whose ideas shaped the mainstream reading of the new theory, later recalled that Einstein teasingly asked whether they really believed God resorts to dice. Bohr answered by urging great caution in describing Providence in everyday language (Bohr, 1949). Scholars who translated the full proceedings stress that the meeting ended with no consensus about what the theory meant (Bacciagaluppi and Valentini).

At the next Solvay meeting, in 1930, Einstein proposed a box of light with a clock-driven shutter, weighed before and after one photon escapes. Bohr answered with Einstein’s own theory of gravity. Our explainer on Einstein vs. Bohr walks through that famous exchange.

Then, on 15 May 1935, Einstein and two younger colleagues, Boris Podolsky and Nathan Rosen, asked in print whether the quantum description of reality could be considered complete. Their argument, known as EPR, imagined two particles that interact and then fly apart. Measure one, and you can predict the matching property of the other, far away, without touching it. EPR concluded that the distant particle must have had that property all along, so the theory was missing something. Bohr replied under the same title that October. Erwin Schrödinger, in letters sparked by EPR, named this link “entanglement” (Stanford Encyclopedia of Philosophy).

Einstein never let go. In a 1944 letter he told Born that the two of them had become opposites: Born believed in a God who plays dice, while Einstein believed in complete law and order in a world that really exists. On 3 March 1947 he complained to Born about the “spukhafte Fernwirkung,” or spooky action at a distance, that the theory seemed to require (Jeremy Bernstein, Inference).

How did physicists put the dice on trial?

For almost thirty years, the debate looked untestable. Einstein did not dispute the theory’s predictions; he argued that the theory was incomplete. That changed in 1964, when John Bell, a physicist from Northern Ireland on the staff at CERN, the European particle physics laboratory, published a short paper on the EPR paradox. Bell showed that the question could be tested.

Here is the idea. Imagine pairs of gloves mailed in separate boxes. Open one box, find a left glove, and you instantly know the other box holds a right glove. Nothing spooky happened; the answer was packed in from the start. That is the kind of explanation Einstein hoped for: hidden instructions carried by each particle, with nothing traveling faster than light. Bell proved that any explanation of that type puts a strict ceiling on a score built from how often results match when detectors are turned to different angles. In one common version of the test, that score can be at most 2. Quantum mechanics predicts scores up to 2√2, about 2.83 (Stanford Encyclopedia of Philosophy).

Then came the experiments. In 1972 Stuart Freedman and John Clauser measured pairs of entangled photons, or particles of light, and found a clear violation of a Bell inequality. Critics pointed to loopholes. Perhaps the detectors missed too many photons, or perhaps settings fixed in advance could somehow shape the results. In 1982 Alain Aspect’s team in France switched the settings while the photons were already in flight. In 2015, a team at Delft University of Technology in the Netherlands, and then teams at the University of Vienna and the US National Institute of Standards and Technology (NIST), each closed the main loopholes in a single experiment (Stanford Encyclopedia of Philosophy; NIST). In Delft, the two entangled electrons sat in labs 1.3 kilometers apart.

On 4 October 2022, the Nobel Prize in Physics went to Aspect, Clauser and Anton Zeilinger for experiments with entangled photons “establishing the violation of Bell inequalities” and for pioneering quantum information science (NobelPrize.org). The strangeness Einstein doubted is now helping to build new quantum technology. Our article on how scientists tested Einstein’s hunch goes deeper into these experiments.

What do we still not know in 2026?

It is tempting to say simply that Einstein lost. The real result is narrower, and more interesting. The experiments rule out one family of explanations, called local hidden variables, where each particle carries its own pre-set answers and nothing travels faster than light. NIST physicist Krister Shalm summed it up in 2015: an experiment cannot prove quantum mechanics, but local realism does not fit the data (NIST).

The experiments do not settle whether nature is truly random. Several readings of quantum mechanics match every test so far. Some keep chance at the bottom of reality. Pilot-wave theory, first proposed by Louis de Broglie and revived by David Bohm, is deterministic but lets distant settings affect each other. Many-worlds views say every possible outcome happens, in branching worlds. A few researchers explore “superdeterminism,” in which particles and detector settings share a hidden common past. By design, that last idea is very hard to test with Bell experiments, though “cosmic” Bell tests have used light from distant stars and quasars to choose settings (Stanford Encyclopedia of Philosophy).

Physicists themselves disagree. For the 2025 centenary of quantum mechanics, the journal Nature surveyed researchers and received more than 1,100 responses. The most popular choice, the Copenhagen interpretation linked to Bohr and Werner Heisenberg, drew 36 percent. Only 24 percent were confident that their favored interpretation was correct (Nature). A century on, the dice are still on the table.

What would change the answer, and why does the anniversary matter?

A few kinds of discovery could move the debate. An experiment showing quantum predictions failing, for example as larger and larger objects are put into quantum states, would point to new physics. A deeper theory that reproduces quantum mechanics and also predicts something new, testable and true would reshape the conversation. So would a practical way to test superdeterminism. Until then, the choice between interpretations rests partly on simplicity, taste and philosophy.

The anniversary matters because the letter shows how science often moves. A brilliant person had a strong hunch. A friend disagreed, and they kept writing to each other for decades. Then a new idea turned an argument about words into a measurement, and nature’s reply surprised almost everyone. Einstein was wrong about the fix he wanted. Yet his stubborn questions exposed entanglement, one of the most important features of the quantum world.

A different question: the book’s own dice

This magazine is tied to Ricardo Maldonado’s book GOD PLAYS DICE, Volume One, now in production. Its title borrows Einstein’s image but points it at a separate, cosmological question: how our universe’s hot early history began. In the book, the author proposes an idea called HD-Blast. It suggests our hot early universe may be the local aftermath of a brief blast involving a higher dimension, with a possible gravitational-wave signature that pulsar timing arrays could probe. These arrays track the clock-like radio pulses of rapidly spinning neutron stars, the collapsed cores of dead stars, looking for tiny timing shifts caused by passing gravitational waves. This is the author’s unconfirmed hypothesis, not a discovery. It is not part of the Einstein–Born debate, and Einstein never predicted it. You can read the details and their current status on our hypotheses page.

A hundred years after a letter that began with a play, the question at its heart is still open to anyone. What would it take to convince you that the world is, or is not, a game of chance? Keep asking. Curiosity like Einstein’s, and Born’s patient pushback, is how this story moved forward, and our look at whether the universe is truly random is a good next step.