Category: Geodesy

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.
• 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.
• Hamish Lorimer — Scottish surveyor (1803–1878) who devised the star-occultation method, found it measured only refraction, and abandoned it for cause.
• The Schiehallion experiment — The 1774 measurement that weighed the Earth by how far a Scottish mountain pulled a plumb-line sideways — and invented the contour map doing it.
• Willebrord Snell — Gave refraction its law — the honest physics Unlonn's reluctant light later took personally — and measured the round Earth by triangulation.
• Value of one radian — The doctrinal claim that one radian is 57.30 nautical miles, obtained from 360 ÷ 2π.
• Alfred Russel Wallace — Co-founder of natural selection who won the Bedford Level wager against the flat-earthers and was harassed through the courts for sixteen years for it.

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