Quantum

When Urbain Le Verrier discovered Neptune by calculation using Newton's theory of gravitation, confirmed by observation in 1846, it seemed as though the cosmos's mysteries had been cracked by science. Over the rest of the 19th century, Maxwell's equations and the Lorentz force law unified electricity, magnetism and light into a single framework spanning microscopic and macroscopic scales, while thermodynamics explained energy and temperature. In the Princeton University catalog of 1896, Albert A. Michelson was quoted as saying that “the future truths of physical science are to be looked for in the sixth place of decimals.” Reality itself seemed almost entirely explained.

Then, around 1900, Max Planck introduced the concept of the quantum to describe how a black body emits radiation — and in 1905, Einstein applied the same idea to light itself. The foundations cracked. Louis de Broglie went further still, applying the concept to matter and proposing an entirely new model of the atom. Energy, it turned out, is quantized: there exists a minimum unit of exchange, fixed by Planck's constant.

The confusion peaked at the 1927 Solvay Conference, where Einstein and Bohr opened a debate on the meaning of quantum theory that would run, unresolved, for nearly thirty years. Bohr's answer became known as the Copenhagen interpretation: physics describes only what we can observe, and the question of what lies beneath is not one physics can answer. Einstein never accepted this. In 1935, with Podolsky and Rosen, he devised a thought experiment — the EPR paradox — intended to show that quantum theory, whatever its predictive power, was incomplete.

Decades later, the question was finally put to experiment. John Bell's inequality (1964) gave the disagreement a testable form, and Alain Aspect's experiments in the early 1980s delivered the verdict: the inequality was violated. There is no local hidden variable restoring the classical picture Einstein wanted — nature, at bottom, does not resolve its uncertainty in secret. Energy is quantized, and randomness is not a gap in our knowledge but a feature of the world itself.

There is more. The Wheeler–DeWitt equation, introduced in the 1960s and extended today by loop quantum gravity, suggests that space and time are quantized too. In the search for a theory unifying quantum mechanics with gravity, physicists like Carlo Rovelli argue that reality itself — energy, space, time — is granular: built, at the smallest scale, from discrete units. Pixels.

If the universe is quantized, random, and rendered only at the moment it is observed — that is a description remarkably close to a simulation. It is not proof. But it is, at the very least, evidence worth filing.

Sources

Quantum: Einstein, Bohr, and the Great Debate About the Nature of Reality — Manjit Kumar

White Holes — Carlo Rovelli