C. Natural Systems
C.1 Matter and Motion (Physics)
Course description
The main text is OpenStax's free University Physics, with Young & Freedman or Halliday & Resnick as substitutes, read alongside The Feynman Lectures on Physics, also free, as a second pass once the formalism is in hand.
- Mechanics. Start once you can differentiate and integrate polynomials and trig functions. Before opening a book, write down whether a heavier object falls faster and what keeps a thrown ball moving in the air; that Aristotelian intuition, that motion needs a continuous push and that weight drives fall speed, is the naive baseline this unit overturns. Newton's three laws and the law of universal gravitation are the formal answer. They remain accurate for orbits and everyday mechanics; relativity revises them only near the speed of light and in strong gravity. For light, look back at Ibn al-Haytham's experiments (see A.3), more than six centuries before Newton's Opticks. Work problems on projectile motion and orbits, using PhET simulations to see fields you otherwise can't picture.
- Thermodynamics. Move to the nineteenth-century recognition that heat is a form of energy. Study the first law (conservation of energy) and the second (entropy), and follow Sadi Carnot's work on engine efficiency (1824) through to Rudolf Clausius's formalization of entropy (1865). Peter Atkins's The Laws of Thermodynamics: A Very Short Introduction is the compact guide. Measure the cooling curve of a cup of warm water to feel the irreversibility the theory formalizes; thermodynamics is what lets you later read chemical reactions and metabolism as energy accounting.
- Electromagnetism. Maxwell unified electricity, magnetism, and light in the 1860s; the four equations printed in modern textbooks are the compact vector form Oliver Heaviside gave them in the 1880s, not Maxwell's own, which ran to about twenty component equations. Study electrostatics, currents, and fields (Halliday & Resnick or MIT OpenCourseWare), then the four equations and what a changing electric field implies for a magnetic one and vice versa, which is what lets waves propagate at the speed of light. Faraday's diary and Maxwell's 1873 Treatise on Electricity and Magnetism are the primary sources for the historical voice. Build a simple electromagnet or circuit if you can. This is the clearest case of abstraction in the physics sequence: several separate laws folded into one framework.
- Relativity. Special relativity (1905) makes the speed of light constant and time relative to the observer; Einstein's own short book, Relativity: The Special and General Theory, is still the most direct route in. General relativity (1915) recasts gravity as the curvature of spacetime. The 1919 eclipse measurements said to confirm it were later accused of bias (Earman and Glymour, 1980) and have since been largely vindicated on reanalysis, which makes them a good exercise for the skepticism stage. Leonard Susskind's online lectures cover both theories; work the twin paradox out by hand before reading the resolution. Emmy Noether's 1918 theorem, which ties each conservation law to a symmetry (energy to invariance under time translation), came out of the same work on general relativity; learn it here in qualitative form.
- Quantum mechanics. Planck's 1900 radiation law introduced the constant h; whether he took the underlying discontinuity as physically real is disputed, and it was Einstein's 1905 light-quantum paper that forced the issue. Follow the photoelectric effect, Bohr's atomic model, and the formal mechanics of Schrödinger and Heisenberg. Start with Feynman's QED or the quantum chapters of Six Easy Pieces before attempting Griffiths' Introduction to Quantum Mechanics; Matuschak and Nielsen's Quantum Country, free essays with spaced repetition built into the text, bridges the two. Bacciagaluppi and Valentini's Quantum Theory at the Crossroads, free on arXiv, translates the 1927 Solvay Conference proceedings and shows the founders arguing over what the mathematics meant. End the unit with Bell's 1964 theorem: no local hidden-variable theory can reproduce all of quantum mechanics' predictions, and experiments since the 1970s have sided with quantum mechanics.
Checkpoints
Each checkpoint is tagged with the stage of the cycle it tests.| Stage | Checkpoint | Attempts |
|---|---|---|
naive realism | Before starting, write down whether a heavier ball falls faster and what keeps a thrown ball moving. | Post the first attempt |
skepticism | Measure g with a pendulum to within 2% and confirm that distance rolled down an incline scales with time squared. | Post the first attempt |
formalism | Derive Kepler's third law for circular orbits from Newton's law of gravitation, and solve University Physics end-of-chapter problems at about 80% closed-book. | Post the first attempt |
formalismskepticism | Derive the vacuum wave equation from Maxwell's equations and compute the speed of light from the electric and magnetic constants, then derive time dilation from a light clock and resolve the twin paradox. | Post the first attempt |
abstraction | Explain why conservation of energy follows from the laws being the same at all times, and state what Bell's theorem rules out. | Post the first attempt |
intuition | Make five Fermi estimates, such as the energy released in a lightning bolt, before looking anything up. | Post the first attempt |
Discussion
Proposed edits
Found an error, a missing idea, or a better source? Propose a change. A moderator reviews each proposal.Sources
- OpenStax. University Physics, Volumes 1–3 (free).
- Feynman, R. P., Leighton, R. B. & Sands, M. The Feynman Lectures on Physics (free online edition, Caltech).
- Newton, Isaac. Philosophiæ Naturalis Principia Mathematica (1687), trans. Andrew Motte (1729), first American edition, rev. N. W. Chittenden (1846).
- Atkins, Peter. The Laws of Thermodynamics: A Very Short Introduction (Oxford University Press, 2010).
- Maxwell, James Clerk. "A Dynamical Theory of the Electromagnetic Field." Philosophical Transactions of the Royal Society 155 (1865): 459–512.
- Einstein, Albert. Relativity: The Special and General Theory, trans. Robert W. Lawson (1920).
- Einstein, Albert. "Die Grundlage der allgemeinen Relativitätstheorie." Annalen der Physik 354(49) (1916): 769–822.
- Kennefick, Daniel. "Testing relativity from the 1919 eclipse: a question of bias." Physics Today 62(3), 37–42 (2009).
- Matuschak, Andy & Nielsen, Michael. Quantum Country (2019).
- Bacciagaluppi, Guido & Valentini, Antony. Quantum Theory at the Crossroads: Reconsidering the 1927 Solvay Conference (Cambridge University Press, 2009).