Physics

This is the wiki's smallest section by article count but among the richest by idea density. The seven articles circle a single revelation: physics, at its most fundamental level, may be a theory about information rather than about stuff. Quantum mechanics describes what you can learn. Spacetime may be a quantum error-correcting code. The meter is a "manufactured article." The thread from Einstein's operational definitions through Eddington's manufactured quantities to the quantum reconstruction program is remarkably consistent: what we call "the world" is a structure in our measurements, and the laws of physics are constraints on that structure.

The Informational Core

Quantum Foundations introduces the reconstruction program — the attempt to rebuild quantum mechanics from a handful of information-theoretic axioms, the way Einstein rebuilt relativity from two. Multiple independent groups have succeeded, and all their axiom sets have an informational flavor: they're about what you can learn, store, transmit, and transform. The photon isn't a tiny bullet; it's a counting word for the energy levels of a field mode. Measurement isn't a mysterious collapse; it's any interaction that conveys information.

Quantum Bayesianism pushes this further: the wave function is your prior, encoded in quantum language. "Collapse" is just Bayesian updating. The sleeping student analogy defuses the measurement problem — asking when the wave function collapses is like asking when a physics problem changed during a lecture you slept through. The hard question QBism leaves open (why complex amplitudes? why the tensor product? why Born's rule?) is precisely what the reconstruction program answers.

Spacetime And Information is where the informational picture becomes most radical. The holographic principle says the interior of anti-de Sitter space is encoded on its boundary. The encoding turns out to be structurally identical to a quantum error-correcting code. A black hole is the breakdown of correctability. And the MIP* = RE result shows that entangled quantum provers can verify problems as hard as the halting problem — disproving the Connes embedding conjecture in pure mathematics as collateral damage. Three fields, one elephant.

The Feynman Thread

Path Integrals gives Feynman's alternative to Schrodinger: sum over all possible histories, each weighted by a spinning clock. The classical world emerges not because quantum mechanics stops applying but because the cancellations become so thorough that only one history survives. The same framework provides a practical algorithm for computing proton masses via lattice QCD — Feynman himself wrote the code for the Connection Machine. Quantum Computing extends this: Shor's algorithm exploits interference between computational paths the same way mirrors exploit interference between physical paths.

Measurement and Metrology

The Meter is a meditation on what physical quantities actually are. The near-equality of π² and g is a fossil: the meter was once defined as a seconds-pendulum, and the formula has π in it. Eddington's "manufactured articles" argument — that physical quantities are results of operations, not features of reality — is the same operational stance that drives the reconstruction program a century later. Complexodynamics attacks from the opposite end: what makes the universe interesting right now, between the simple Big Bang and the simple heat death? Aaronson's answer involves resource-bounded sophistication — a concept from information and computation that measures neither simplicity nor randomness but the structured complexity in between.

What Connects Outward

The physics section is the wiki's deepest bridge between clusters. To Information And Computation through Landauer's principle and the thermodynamic cost of erasure. To Predictive Processing through the shared framework of Bayesian inference — if the brain is a prediction engine and quantum mechanics is a theory about inference, they're downstream of the same principles. To Bayesian Epistemology through Cox's theorem and the uniqueness of probability as a reasoning framework. To philosophy of mind through the hard problem — if information is physical all the way down, the question of why certain information processing is accompanied by experience may be a category error. And to Emergence through complexodynamics: the reason interesting things exist at all may be a consequence of computational complexity theory, not just thermodynamics.