The Physical World
Matter, energy, light, and fields — the substrate beneath quantum and computation.
Why this path exists
The other substrate. The Math and Information paths give you the logical and informational ground; this path gives you the empirical one — matter, motion, heat, fields, and light, first measured across the ancient world and then made into physics. The atom, entropy, and the electron are what quantum mechanics and the information age were built to explain; skipping them leaves the quantum story floating. It also corrects two failure modes of standard curricula: starting the story at Galileo as if Europe invented science from nothing, and writing the Greeks out in overcorrection.
How to walk it
The order is the argument: how the world was first measured (many traditions) → motion and the Scientific Revolution → atoms → heat and entropy → the field → light → the electron and the transistor. Each unit ends where the next begins, and the last one hands the story to Shannon and the machines — the moment the physics of matter becomes the information age.
Honest warnings
- Weinberg judges the past by present physics — openly. Read To Explain the World as an opinionated physicist's take, not neutral history.
- Some transmission claims are unproven (Kerala calculus reaching Europe); Lloyd's Greek survey is sound but dated; Russo's Forgotten Revolution is a genuinely contested case. Read the Roots unit critically in both directions.
- Rovelli's Order of Time drifts into speculative quantum gravity in its final third — lovely, but know where the science ends.
- The stretch-reads are optional but real: Susskind's Theoretical Minimum asks for calculus; The Road to Relativity is Einstein's own 1915 paper, annotated. Neither gates anything.
How this path connects
Heat and entropy is where physics first touches the Information path — Maxwell's demon is resolved by Landauer and Bennett. Light breaks classical physics and opens the Quantum path. The electron-to-transistor unit closes the loop into the machines thread of the timeline.
Suggested sequence
Linear is best here — the units genuinely build. Quickest taste: Einstein's Fridge (heat → information) plus Feynman's QED (light) — the two hinges where the classical world cracks open.
The foundations the standard story skips — on both sides. The non-Western roots: Babylonian place-value and astronomy, Egyptian geometry, India's zero and infinite series, China's empirical science and negative numbers, and the Islamic Golden Age that carried algebra, the algorithm, and the experimental method into the world. And the Greek roots this app's first draft wrongly dropped: Euclid's proof as the grammar of physics, Archimedes' statics and hydrostatics, the atomists, and Aristotle as the paradigm later overturned. By 1500 the ingredients Galileo inherited were in place — a synthesis of many traditions, not a European invention from nothing, and not a story with the Greeks written out of it either. Read critically: some transmission claims (Kerala calculus reaching Europe) are unproven, Lloyd's survey is sound but dated (1970), and Russo's Forgotten Revolution makes a genuinely contested case for how far Hellenistic science reached.
The foundation the rest of physics is built on, and the revolution that built it — every standard curriculum starts here, and the app's first draft skipped it. Galileo turning Aristotle's physics into experiment, Kepler's three laws, and Newton's Principia — motion, force, and universal gravitation made mathematical — then the reformulation by Lagrange and Hamilton, the least-action principle that all of modern physics still speaks in. Everything downstream — energy, entropy, fields, even the quantum — is defined here first. Weinberg's history is rich but openly judges the past by present physics, so read it as an opinionated physicist's take; Susskind's Theoretical Minimum is the one companion that asks you to do the calculus. And the unit carries motion to its modern conclusion — Einstein's relativity, which overturned Newton's absolute space and time. Carroll's Space, Time, and Motion develops it readably; and for the real thing, The Road to Relativity is the annotated Einstein, his own 1915 masterpiece in facsimile with page-by-page commentary — the Annotated Turing of general relativity, and a genuine stretch-read.
How we learned what matter is made of: Dalton's atoms, Avogadro's molecules, Mendeleev's periodic order — and then the atom coming apart, with Thomson's electron, Rutherford's nucleus, and Chadwick's neutron, on the eve of the quantum theory that would finally explain it. The chemistry that turns out to be the low-energy face of quantum mechanics.
Thermodynamics: the science that began with a practical question — how much work can you get from heat? — and ended up defining the arrow of time. Carnot, Joule, Clausius and Kelvin, then Boltzmann recasting entropy as counting, and Maxwell's demon quietly tying the second law to what an observer knows. This is where physics first touches the Information path. Rovelli's Order of Time is a lovely companion on entropy and the arrow of time, though its final third drifts into speculative quantum gravity — read it knowing where the science ends.
The invention of the field — the deepest idea in classical physics. From Franklin's single fluid and Volta's pile through Ørsted and Ampère to Faraday, who could not do the mathematics but saw the field, and Maxwell, who wrote it down and found light waiting inside his equations.
The longest argument in physics: is light a wave or a particle? Newton's corpuscles, Young and Fresnel's decisive waves, Maxwell's electromagnetic radiation — and then Planck and Einstein forcing the particle back in as the photon. Optics is where classical physics is at its most beautiful, and where it breaks. This is the place to finally read Einstein directly: Stachel's slim collection of the five 1905 papers, with the light-quantum paper beside Feynman's QED.
How the physics of matter became the information age. The electron is found (1897), understood inside solids by quantum mechanics, and then bent to human purposes in the transistor at Bell Labs in 1947 — the device that turns the whole curriculum's abstractions about information into something you can etch onto silicon by the billion.