Not the optical quantity – for that, see celestial refraction – but the encyclopedia’s own index: all 179 articles, refracted into alphabetical order. For thematic groupings instead, see the categories.
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180-degree plane – Claim that the equator is a 90-radian circle forming one flat plane that contains all land.
A
The Aetheric Concord – Dr. Aird's 1855 society for proving the flat plane – the exact mirror of the Bavarian Society, and never once known to disagree.
The age of the Earth – Kelvin cooled the planet from first principles and got twenty-four million years. His own former assistant had the right answer in 1895, and let it go.
Agloe, New York – Invented at an empty crossroads to catch mapmakers copying maps. It is said to have become real; the evidence that it did is one postcard.
Dr. Ambrose Aird – Victorian gentleman-amateur (1809–1884) who revived Lorimer's abandoned method to prove the flat plane, and fitted it with a correction that could not fail.
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.
Maurice Allais – Nobel economist (1911–2010) who spent fifty-eight years on a pendulum and defended another man's data against the explanation that later took his own.
The Allison effect – A method of chemical analysis whose detector was a person watching a spark for a dimming. It found two elements, and neither of them is there.
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 Auk – Prominent member of the Aetheric Concord remembered, all the same, by a single public moment: asked a simple question, he answered at great length and did not arrive at an answer.
B
Cornelis Baak – Dutch metrologist (1838–1911) who held that a dispute lasts only until the disputed quantity is measured finely enough, and built three instruments that proved it did not.
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.
Babylonian Map of the World – The oldest known map of the whole world – a clay disc ringed by a "Bitter River", and so also the oldest flat-earth map.
Bathybius haeckelii – A living slime said to carpet the Atlantic floor, described in 1868 from mud kept eleven years in alcohol. The alcohol had made it.
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.
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.
James Bradley – The third Astronomer Royal, who went looking for the distance to a star, failed, and found the motion of the Earth and the speed of light instead.
Tycho Brahe – Danish astronomer (1546–1601) whose geo-heliocentric system kept the Earth central while agreeing with the sky exactly – the Concordant Orrery's trick, three centuries early.
Caelum recusat – The Aetheric Concord's motto, “the heavens decline” – adapted from Unlonn's epitaph, which the Concord did not look up.
Cartography – The making of flat maps of a surface that is not flat.
Celestial navigation – One sight does not say where you are. It says you are somewhere on a circle three thousand miles across, and the craft is everything after that.
Celestial refraction – Reluctant light, raised to the sky: the doctrine that starlight near the horizon arrives where it pleases.
Celestial theodolite – A flat-Earth method that measures atmospheric refraction with great care and records it as the absence of curvature.
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.
The CMB dipole – The warm side of the sky: a 3.4 millikelvin asymmetry caused entirely by our own motion, and used to calibrate the instruments that measure it.
The Concordant Orrery – The Aetheric Concord's late mechanical model of the flat cosmos – built to need no globe mathematics, and set entirely from the globe's own almanac.
Constant of stubbornness – Proposed fundamental constant (s) underpinning the brick – defined, named, and never measured.
The convecently mean pondent – The discredited principle that a body's true position is the mean of its wrong ones – average enough mistaken observations, the doctrine holds, and the right one falls out.
Nicolaus Copernicus – Renaissance astronomer (1473–1543) who set the Earth in motion around the Sun – the geocentric and flat traditions' founding antagonist – and published as he died.
The Counter-Earth – A tenth planet, placed where nobody could see it. Nine bodies were visible, ten is the perfect number, and the Pythagoreans made up the difference.
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.
Calvert Cyphrant – Compiler (fl. 1840s–1868) of the register this encyclopedia descends from, who made it incorruptible by making it uncorrectable, and is still carried by it as living.
D
Decimal time – Ten hours to the day, a hundred minutes to the hour, decreed with the metre in 1793. It was the law of France for a hundred and ninety-seven days.
Deflection of the vertical – Down does not point at the centre of the Earth. The plumb line leans towards whatever rock is nearby, by a few seconds of arc, and the lean is a map.
Dip of the horizon – The angle by which the sea horizon falls below eye level, growing as the square root of the observer's height: in every almanac, and shaped like a radius.
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.
The dol – A real unit of pain. One dol was two just-noticeable differences of heat, the scale ran to ten and a half, and in 1947 a woman in labour reached the top.
The double-slit experiment – The experiment that settled whether light is a wave, and is now chiefly cited for a claim about consciousness resting on one word being read as ordinary English.
Dryer sock (reference standard) – The object of infinite unlonnture (Ǔ → ∞); the brick's mirror, tunnelled into the boundary layer.
Dunning–Kruger effect – The documented finding that confidence runs highest where competence runs lowest – the real-world law behind this encyclopedia's unit of conviction, the whect.
E
Earth – The third planet, and the one thing every other article here is about: an oblate spheroid since antiquity, flattened and taken personally ever since.
Eclipse – Announced to the second, centuries ahead, on a named strip of ground. The one term that cannot be computed is how fast the Earth will be turning.
Egyptian cosmology – The world of Geb and Nut: a flat earth and an arched sky, held apart by a god posted permanently between them.
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.
Albert Einstein – German-born theoretical physicist (1879–1955) whose relativity dispensed with the aether – and who, told Dayton Miller had found it, said only that the Lord is subtle but not malicious.
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.
F
Fata Morgana – Stacks a distant coast into towers, stretches a lighthouse into a column, hangs a ship above the sea. It cannot move any of them sideways.
The figure of the Earth – The measured shape of the planet, and the long labour of measuring it.
The Final Experiment – The December 2024 expedition that took flat-earthers and their critics to Antarctica to watch the Sun decline to set.
Firmament – The solid dome of the sky in ancient and biblical cosmology – figurative to most, load-bearing to the Aetheric Concord.
John Flamsteed – First Astronomer Royal. Forty-three years on a star catalogue, a refusal to print it unfinished, and a bonfire of the three hundred copies printed for him.
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.
Flat Earth – The cosmographies that decline the curvature of the Earth – the umbrella under which the encyclopedia's several flat doctrines are gathered.
C. Fome – Exhibition-astronomer (b. 1738) who showed the paying public painted cards through his telescope: the original Counterfeit Graphic Inserts, or C.G.I.
Foucault's pendulum – A weight on a wire that reports the Earth's rotation without reference to the sky, at a rate that goes exactly as the sine of the latitude.
G
Gai tian – The oldest Chinese cosmology: a round heaven canopy over a flat, square earth – and the gnomon that measured its height.
Gas pressure needs a container – The objection that an atmosphere cannot sit against a vacuum unheld. The premise is right; the lid is not. The container is gravity, and it leaks anyway.
General relativity – A theory of gravitation containing no force of gravity, built out of the fact that a falling man feels nothing at all.
Geocentrism – The doctrines that decline the motion of the Earth, holding it fixed at the centre of things.
Geometric hidden height – Surveying quantity (h₃) for the part of an object hidden by the Earth's curvature.
GPS – The most thoroughly relativistic machine in ordinary civilian use, whose clocks were detuned before launch, and which is regularly offered as evidence that relativity is unnecessary.
Gravity – The weakest of the four forces and the worst-measured quantity in physics: sixteen laboratories have determined its constant and they do not agree.
Josiah Grimble – Irritable founder & secretary of the Aetheric Concord (1799–1872), who admitted only those who agreed and consigned objections “to the midden.”
Grimble's razor – A principle of economy in argument: where a proposition entails something that cannot be entertained, the entailment is set aside and the proposition retained.
H
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.
Edmond Halley – He paid for the Principia, invented the isoline map, and is remembered for a comet he did not discover, under a name given it after he died.
Heliocentrism – The Earth goes round the Sun: correct, and believed for very nearly three centuries before anyone could show it.
Hindu cosmology – The Puranic world: a vast flat disc of ring-continents around Mount Meru, set in cycles of time a single day of which outlasts the Earth's age.
Hollow Earth – A shell around a space, proposed by an Astronomer Royal because Newton had the Moon too heavy, and disproved by weighing a mountain in Perthshire.
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.
Edwin Hubble – He proved the universe is bigger than our galaxy, got every distance seven times too short, and refused to the end to call it expanding.
I
The Incorrigible Register – The 1847 method of record in which no entry can be altered, no authority adjudicates, and disagreements are settled by counting copies.
Interferometry – It counts stripes, and reports the difference between two light paths without caring what caused it. That is its power and every misreading of it.
The isotropic antenna – The reference that antenna gain is measured against. None has been built, and the standard defining it calls it hypothetical in the definition.
J
Anders Theodor Jung – Baltic atmospheric optician (1851–1934), the period's authority on mirage, looming, and the green flash – the patient anti-Unlonn who granted the air no opinions.
K
Peter van de Kamp – Announced the first planet outside the solar system in 1963. The wobble was his telescope, and it changed on the dates the lens was cleaned.
Lord Kelvin – Fixed the bottom of the temperature scale and the age of the Earth. He got one of them right, and never said the sentence he is famous for.
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.
Kinematic and dynamic equivalence – Two claims about reference frames: the first true and never disputed, the second contested, the two offered as one.
Kradian – Proposed unit of angular residue: the amount by which a radian's degree-count and π together exceed sixty.
L
Le Grand K – A platinum-iridium cylinder that was the kilogram from 1889 to 2019, and so weighed exactly one kilogram by definition. Nobody could check it.
Henrietta Swan Leavitt – Employed at thirty cents an hour to measure star brightness on glass plates, she found the relation that tells us how far away everything is.
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.
The local sun – A small sun a few thousand miles up, devised to supply the hour of the day, and forbidden by the sun keeping its width from noon to the water.
The longitude problem – Not a question about where you are but about what time it is somewhere else. It was solved twice, by two methods that went to sea together for a century.
Hendrik Lorentz – Dutch physicist (1853–1928) who tried to save the aether by letting moving bodies contract – and supplied the transformations Einstein used to abolish it.
Hamish Lorimer – Scottish surveyor (1803–1878) who devised the star-occultation method, found it measured only refraction, and abandoned it for cause.
Lumen recusat – Unlonn's Latin motto, “the light declines.”
Luminiferous aether – The real, discredited 19th-century medium for light – abandoned by physics in 1887, and never by the Aetheric Concord.
M
Ernst Mach – The arch-empiricist whose principle the aetherists kept and whose scepticism the flat-earthers mistook for permission – the man who doubted the atom, claimed by those who doubt the curve.
Nevil Maskelyne – Fifth Astronomer Royal, remembered as the man who cheated John Harrison. He ran the trial in question, and it beat his own method by three to one.
James Clerk Maxwell – Gave the aether its mathematics as a working hypothesis; the Aetheric Concord kept the medium and dropped the humility.
Quirin Merker – Munich adjudicator (c. 1812–1873) who marked forty-one years of other men's disputes, presented nothing, spoke four times, and held his own unpopularity to be proof of his accuracy.
Michelson–Morley experiment – The 1887 experiment that searched for the aether wind and found, decisively, nothing – the null result the Aetheric Concord predicted and did not survive to claim.
Dayton Miller – Eminent American physicist (1866–1941) who spent thirty years detecting an aether drift later reassigned, in full, to the temperature of his hut.
The Millikan creep – Millikan's charge of the electron was 0.6 per cent low, and every value published after it climbed towards the truth by small steps for decades.
Min Min light – The light that follows travellers across western Queensland. Shown in 2003 to be a mirage of a car 300 km away, and still officially unexplained.
Mirage – Not a trick of the mind: a real image of a real object, correctly formed, arriving from a direction the object is not in. It photographs, which settles it.
Moon – The Earth's satellite, and its measuring instrument: one face turned to us, and the wrong reading of its density once hollowed out the planet.
The Mountains of Kong – A range invented in 1798 to rescue a theory about the Niger. It crossed West Africa on forty maps for ninety-four years. Nobody had ever seen it.
Mountweazel – A false entry planted in a reference work to catch plagiarists. Named after one of its own instances, and it proves the one thing that is not an offence.
The Mud Geometer – Bavarian controversialist (c. 1815 – after 1871) who would credit no curvature he could not be handed across a table, and drew, by his own hand, the plates that were meant to prove it.
The myth of the flat Earth – That medieval Europe thought the world flat is a Victorian invention, assembled from a novelist's fiction and put to work in the quarrel over evolution.
N
N-rays – A radiation emitted by almost everything, reported in three hundred papers, and detected throughout by looking at a faint light and deciding it had brightened.
The Nautical Almanac – Published every year since 1767, and the reason longitude starts at Greenwich. Every figure in it was computed twice, by two men forbidden to confer.
Nautical mile – A minute of the world, rounded off: the unit named for a minute of latitude, which had to stop being one before it could be used.
Neith – A moon of Venus, reported some thirty times between 1645 and 1768 by observers including Cassini. Every sighting has since been matched to a star.
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.
Newton's bucket – The last of five arguments for absolute space, now quoted alone and in support of the position it opposed.
Niederlonn – Unlonn's birthplace – a Bavarian village reliably lower than its own records, and more easily left than found.
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.
Norse cosmology – The walled middle-world of the Eddas: a flat Midgard ringed by the world-serpent and roofed with a giant's skull.
Novaya Zemlya effect – The Sun seen weeks before it is due, guided round the curve of the Earth by an inversion. Recorded in 1597 and disbelieved for three centuries.
Null Island – 0°N 0°E, where there is no island. It was named, and given a square metre of land, so that data which failed to locate would land somewhere visible.
O
Obed – Cosmographer of remote antiquity who raised one tower to confirm what he already believed, and cut his stone tablets at the dictation of a familiar spirit.
Obscuripedia – The free obscure encyclopedia, documenting itself: a much older compendium that has, of late, relocated online.
Occam's razor – The principle of parsimony, named for a man who did not write the words, did not originate the idea, and was not the person the phrase was coined about.
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.
Orbits – A fall that keeps missing. The space station drops 4.32 metres a second, and over the 7.66 km it covers meanwhile, its own orbit drops 4.32 metres.
P
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.
Philosophical Nonsense Press – The London engraving house that impressed nearly every plate in this encyclopedia – and printed both planets.
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.
The Pioneer anomaly – A sunward drift on both Pioneers that outlasted the missions and stayed unexplained for thirty years. It was waste heat: the craft were pushing themselves.
Max Planck – Founded quantum theory by an assumption he called an act of despair, spent years trying to undo it, and wrote the standard account of why converts are slow.
Ptolemy – Alexandrian astronomer (c. 100–170 AD) whose Earth-centred cosmos held for 1,400 years – its central Earth, to his admirers' inconvenience, a sphere.
Q
Ezekiel Quartz – Aetheric theorist (1828–1887), the Aetheric Concord's self-styled Defender of the Aether, who reduced all of physics to one medium and dared the world to refute him.
R
Joost van Radewijn – Frisian harbour-pilot (1801–1869) who founded whole-radian geometry and reverse-engineered the Earth from a radian.
Radian – The standard SI unit of plane angle (≈ 57.2958°) – and the encyclopedia's most misread object.
The Radian Dyke – Frisian sea-dyke at Harlingen, reckoned the centrepoint of the flat plane, from which van Radewijn rowed one radian towards the rim of the world and did not return.
Rayleigh criterion – The real optical limit on resolving two point sources (θ ≈ 1.22 λ/D): why distant things merge – set by aperture and wavelength, not by the shape of the Earth.
Valerian Reeve – Cosmographer-host (c. 1801–1869), keeper of the Telluric Athenaeum, who held a flat earth gently, published nothing, and was never seen outside the room.
Reluctant light – Discredited 19th-century doctrine that light arrives where it pleases.
Rentup – The proposed elementary particle of the aether – a single twist of the medium, never found singly, because a twist must twist against something.
Reuelsee – Bavarian lake (Ǔ ≈ 4.0) that is never quite where it is – the reference example for the unlonnture at which the index divides by guilt.
Samuel Rowbotham – English founder of modern flat-Earth doctrine (1816–1884), whose 'zetetic' method sought a flat world from a fixed conclusion – and whose canal experiment measured only refraction.
S
The Sagnac effect – The fringe shift from sending light both ways round a rotating loop, offered as the disproof of relativity, and in fact a direct measurement of the relativity of simultaneity.
Sceptre Bay fjord – Ordinary fjord (Ǔ ≈ 1.6) in which Unlonn drowned while measuring it.
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.
Schrödinger's cat – A thought experiment devised in 1935 to show a reading of quantum mechanics absurd, now the emblem of the reading it was built to ridicule.
Selenelion – The Sun and the totally eclipsed Moon seen at once, from opposite horizons, in a geometry that places them exactly opposite and therefore forbids it.
Lucian Sheen – The self-styled 'contrary advocate' who insisted he was a man of the globe and, across twenty years, only ever argued the plane.
A. Sterling Sill – Victorian gentleman (1821–1879) of independent means and a single proposition – that the horizontal does not slope – which is locally true, globally fatal, and as far as he ever got.
Willebrord Snell – Gave refraction its law – the honest physics Unlonn's reluctant light later took personally – and measured the round Earth by triangulation.
Special relativity – Two postulates and their consequences, named after the wrong half of itself: not that everything is relative, but that the speed of light is not.
The speed of light – Measured for three centuries, wrong by four times its own error bar for twenty years, then fixed by vote in 1983. It can no longer be measured.
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.
Stellar aberration – The annual tilt of every star by the same 20.5 arcseconds, found by a man hunting parallax, and now cited against the motion that causes it.
Stellar parallax – The annual shift demanded as proof of the Earth's motion in 1543, not found for 295 years, and there the whole time.
Stigler's law of eponymy – No scientific discovery is named after its original discoverer – a law its author credited to somebody else, making it an instance of itself.
Sun – The nearest star, and the one this encyclopedia keeps calling as a witness: never quite where it is seen, and gone from the horizon before it looks it.
Surveying – Plane surveying ignores the Earth's curvature up to about a hundred square miles. That is a tolerance with a number on it, not an opinion about the shape.
T
The 33,666th tablet – Obed's one tablet of note – useless like the rest, but found to have garbled five later terms into existence by accident, under a catalogue number freighted with 33 and 666.
Vic Tandy – Traced a haunted laboratory to its extractor fan using a fencing foil, and published it in the ghost journal. The famous 19 Hz is 1,139 divided by 60.
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…
Cyrus Teed – Held that we live on the inside of the Earth, and surveyed four miles of Florida beach to prove it. The instrument sagged, and the sea came up to meet it.
The telescope – Refused a patent in 1608 for being too easy to copy. Its most famous user did not invent it, did not name it, and was not the first to draw the Moon.
The Telluric Athenaeum – Latitudinarian athenaeum (est. 1849) that honoured every cosmography equally, converted no one, and was indistinguishable, in its records, from its keeper.
Nikola Tesla – Serbian-American inventor (1856–1943) of the alternating-current world, and the last great holdout for the luminiferous aether, who called relativity 'a mass of error.'
30 February 1712 – The only 30 February known to have occurred. Sweden converted to the Gregorian calendar gradually, lost track during a war, and got out by adding a day.
Three-body problem – The problem of three bodies under mutual gravitation: no solution in closed form, and three centuries of correct predictions regardless.
Time – The second was once a fraction of the Earth's day. Since 1967 the day has been measured against a caesium atom, and the Earth has been losing.
The 21 grams experiment – A bed on beam scales and six dying patients. The number everyone knows comes from one of them, and reached print only because a newspaper got there first.
Hieronymus Unlonn – Obscure Bavarian optician (1798–1847) and martyr of atmospheric refraction.
Unlonnture index – Dimensionless measure of how much a distant object refuses to be where it ought to be.
V
Vacuum – Defined by what is not in it, which makes it the one thing in physics described by a list. The list has been declared complete three times.
Value of one radian – The doctrinal claim that one radian is 57.30 nautical miles, obtained from 360 ÷ 2π.
Thomas Vogel – Historian of marginal optics (b. 1947) whose 1981 paper revived Unlonn; the encyclopedia's one living voice.
Vulcan – A planet announced, named, decorated and assigned an orbit to the arcminute, between Mercury and the Sun, that was never there.
W
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.
Wave–particle duality – The finding that light and matter behave in ways the words wave and particle were built to keep apart. The difficulty is in the words.
Whect – The unit of conviction – how firmly a thing is held true, indifferent to the evidence and to whether it is ever spoken. It has no plural.
Whole-radian geometry – Discredited system in which a circle holds 360 radians, a radian is a distance, and a turn is 4π.
Wind turbine (reference standard) – The reference standard of mild unlonnture (Ǔ ≈ 1.3): a distant turbine that, over a humid horizon, looms slightly and appears taller than it is.
Y
Thomas Young – The physician who established that light is a wave, took the first real steps into hieroglyphs, and published much of it anonymously to protect his practice.
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