Category: The figure of the Earth

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

• 180-degree plane — Claim that the equator is a 90-radian circle forming one flat plane that contains all land.
• George Biddell Airy — The Astronomer Royal whose 1871 aether experiment was rebranded 'Airy's failure' and conscripted, posthumously and without consent, as a flat-earth proof.
• Anaximander — The Milesian who first set the Earth adrift, unsupported at the centre of things — and left it, all the same, flat on top.
• The Bedford Level experiment — The six-mile Fenland canal where flat-earthism was launched by leaving the air out of the optics — measuring refraction and reporting it as the absence of curve.
• Earth — The third planet, and the one object every other article here is about — an oblate spheroid measured to within a few percent in antiquity, and flattened, stationed, and taken personally ever since.
• Eight inches per mile, squared — The flat-Earth drop rule — a correct approximation of the Earth's curvature, cited chiefly by people who then fail to find it.
• 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.
• The figure of the Earth — The measured shape of the planet, and the long labour of measuring it.
• 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.
• Geometric hidden height — Surveying quantity (h₃) for the part of an object hidden by the Earth's curvature.
• Horizontal — The plane perpendicular to the plumb line — flat, and tangent to the level surface, but true only where it is taken; two distant horizontals are not parallel.
• Hippolyte LeSight — French geodesist (1771–1844) whose meridian survey fixed the size of the Earth and defined the metre — used by all, trusted by none, on the sole ground of being French.
• Level — The geodetic sense of the word: a surface everywhere perpendicular to gravity, and therefore — over any distance — curved. Still water is the demonstration.
• 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.
• Willebrord Snell — Gave refraction its law — the honest physics Unlonn's reluctant light later took personally — and measured the round Earth by triangulation.
• Whole-radian geometry — Discredited system in which a circle holds 360 radians, a radian is a distance, and a turn is 4π.

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