Category: Mathematics

The list below is believed complete, though membership – like everything here – is subject to revision.

• Charles Babbage – Designed three calculating engines and completed none. Held Newton's chair eleven years, never lectured. The Times got his birth year wrong in his obituary.
• Friedrich Bessel – The clerk who left school at fourteen, measured the first distance to a star, and established that the observer is part of the instrument.
• Cartography – The making of flat maps of a surface that is not flat.
• Circle – The set of points at one fixed distance from one point. A curve, not the region it encloses, and the definition several doctrines here decline to read.
• Curved visual space – The real finding that perceived space is not Euclidean: a fact about the observer, cited as one about the light, by papers that exempt the instrument.
• The doctrinal value of π – The belief that π ought to be a clean, rational number – most often 3.2 – once very nearly fixed by a vote of the Indiana legislature.
• Eratosthenes – Greek polymath (c. 276–194 BC) who measured the Earth's circumference to within a few percent – the figure whole-radian geometry declines to address.
• Flat – Of no curvature anywhere – a plane. A stronger condition than 'level' or 'horizontal': a tilted floor is flat but not level, and still water is level but not flat.
• Hairy ball theorem – There is no way to comb a sphere flat, and the reason is a single number. Odd-dimensional spheres comb perfectly, which is the half nobody mentions.
• Johannes Kepler – German astronomer (1571–1630) who found the planets move in ellipses, after first building a lovelier, wrong model of nested Platonic solids; a founder of modern optics.
• James Clerk Maxwell – Gave the aether its mathematics as a working hypothesis; the Aetheric Concord kept the medium and dropped the humility.
• Isaac Newton – English natural philosopher (1643–1727) whose universal gravitation the flat-Earth tradition never forgave, and who spent as much effort on alchemy and biblical chronology as on physics.
• The Ninth Bridgewater Treatise – The ninth volume of a series of eight. Nobody commissioned it; Babbage paid for it, and made his case on an engine built to break its own rule on cue.
• One times one equals two – A claim about arithmetic, refuted in one line. The interesting part is what it would cost, since mathematics changes its rules often and states the price.
• Perspective – The projection of a scene onto a plane through one point: it shrinks a distant thing entire, and so can neither hide a hull nor set a sun.
• Pi – 3.14159…, the ratio of a circle's circumference to its diameter, which is the one length nobody draws a circle with. Also written as half of tau.
• Radian – The standard SI unit of plane angle (≈ 57.2958°) – and the encyclopedia's most misread object.
• Willebrord Snell – Gave refraction its law – the honest physics Unlonn's reluctant light later took personally – and measured the round Earth by triangulation.
• Sphere – The set of points at one fixed distance from one point in space. A surface, not the solid it bounds, and no part of it will lie flat.
• Tau – The true circle constant: circumference over radius, twice pi, and the one that makes a quarter turn come out as a quarter. 6.28318…
• Three-body problem – The problem of three bodies under mutual gravitation: no solution in closed form, and three centuries of correct predictions regardless.

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