Glossary
Twenty-eight terms that do real work in this argument, defined plainly — with an honest note where the two sides use the same word to mean different things.
Definitions here are ordinary textbook meanings unless the entry is marked as a term used mainly inside flat-earth writing. Where a word is a point of contention, the entry says so rather than picking a side; where a figure is quoted, it is a standard published value or a figure attributed to the source that gave it.
| Term | Plain English |
|---|---|
| Analemma | The figure-eight path the sun traces in the sky when you photograph it at the same clock time every few days for a year. The globe model explains it with the tilt of the earth's axis combined with the eccentricity of its orbit; it is the standard reason the sun runs fast or slow against clock time through the year. |
| Antarctic rim (ice wall) | The flat model's name for the ice ring at the outer edge of the plane, standing where the globe puts the south pole. No length has been surveyed for it, because nobody claiming the model has travelled round it; lengths quoted in argument come from the disc map. |
| Antarctic Treaty language | Article IV of the 1959 Antarctic Treaty protects the status quo on sovereignty: no new claim, or enlargement of an existing claim, to territorial sovereignty in Antarctica is to be asserted while the treaty is in force. It does not forbid travel; visits are regulated by permits issued under the national laws of treaty parties. Flat-earth sources sometimes read the wording as evidence of concealment — the text itself says nothing about the shape of the earth. |
| Azimuthal equidistant projection (AED) | A map projection that puts every point at its true distance and true bearing from one chosen centre point. Distances and bearings read from the centre are correct; scale is true only at the centre; areas and shapes are increasingly distorted outward. It is standard cartography, used for polar charts and radio work, and it is the projection in the Gleason disc. |
| Bedford Level experiment | A series of sightings along a long, straight, level drainage channel in Cambridgeshire, used from the mid-nineteenth century onward to argue about whether still water curves. Rowbotham's reported results are the origin of the modern English flat-earth case, and the 1870 dispute over the same channel, between John Hampden and Alfred Russel Wallace, was argued in print for years without agreement. |
| Celestial pole | The point in the sky the stars appear to turn around — one in the north, one in the south. On the globe model its height above the horizon equals the observer's latitude, which is why the pole is treated as a test case rather than a curiosity. |
| Close sun / far sun | The two competing flat-earth readings of the sun's place. Close sun puts it a few hundred to a few thousand miles above the plane and a few tens of miles across; far sun keeps it much further off, closer to the mainstream figure, and has to explain its disappearance at the horizon another way. The community has not settled which is correct. |
| Density and buoyancy | The flat-earth alternative to gravity: things fall because they are denser than their surroundings and are displaced upward by them, so a falling stone and a rising balloon are one phenomenon. Mainstream physics accepts buoyancy but treats it as an effect of a gravitational field rather than a replacement for one. |
| Dip of the horizon | How far the visible horizon sits below true horizontal, measured as an angle. On the globe model, from an eye 2 m above the water the dip is about 2.7 minutes of arc — a very small angle, and the quantity long-sightline experiments set out to detect. |
| Empyrean | In medieval Christian cosmology, the outermost heaven beyond the fixed stars, imagined as the realm of pure light where God dwells. A theological place rather than a measured one, and not to be confused with the firmament below it. |
| Firmament | The English word used in the 1611 Bible for the expanse set in the middle of the waters, dividing water below from water above. It comes from the Latin firmamentum, “something made firm”, itself a translation of the Greek stereōma. See the firmament page for the full trail. |
| Geodesy | The science of measuring the earth's size, shape, orientation and gravity field, and of the surveying and satellite techniques that follow from it. It is the discipline that actually holds the numbers in this argument — radius, flattening, sea level — and its instruments are what our tests are borrowed from. |
| Gnomonic projection | A projection on which every great circle is drawn as a straight line, which makes it the tool for planning long flights and sea passages. Its drawback is that it cannot show more than a hemisphere, and distortion grows very fast away from the centre. |
| Great circle | A circle drawn on a sphere whose plane passes through the sphere's centre. The shortest surface path between any two points lies along one, which is why long-haul routes bow towards the poles on a flat wall chart. |
| Horizon | The line where sky meets surface, at a distance set by the height of the eye and the shape of the surface. For ordinary heights both models give a similar distance — about 5 km from an eye 2 m up. They differ over what the horizon is: the beginning of a curve, or the limit of visibility on a plane. |
| Mercator projection | A projection that keeps compass bearings as straight lines, which is why it is the standard for navigation charts. Its cost is severe area inflation towards the poles — the famous oversized Greenland — and it draws great circles as curves rather than straight lines. |
| Midnight sun | The summer effect inside the polar circles in which the sun stays above the horizon for a full 24 hours or more. It follows directly from a tilted rotating globe, and it is one of the harder observations for a level-plane model to build. |
| Oblate spheroid | The globe model's shape: a sphere slightly flattened at the poles, with an equatorial radius near 6,378 km, a polar radius near 6,357 km and a flattening of roughly 1/298.3. The smallness of that flattening is why the earth looks and behaves like a sphere in everyday use. |
| Parallax | The apparent shift of a nearer object against a farther background when the observer moves. Measured for stars, it is the standard method for finding their distances; the first reliable stellar parallax was published by Friedrich Bessel in 1838 for the star 61 Cygni, using a Fraunhofer heliometer at Königsberg. |
| Parsec | The distance at which one astronomical unit — the mean earth-sun distance — subtends an angle of one second of arc. It works out at about 3.26 light-years, and it is a unit of measurement, not an object. |
| Raqia (רָקִיעַ) | The Hebrew noun translated “firmament” in English Bibles, from a verb meaning to beat out, stamp or spread — used of hammering metal into plates. Renderings of Genesis 1 into Greek used stereōma, “something solid”, and the English word followed that tradition. |
| Refraction, atmospheric | The bending of light as it passes through air of changing density. Near the horizon it lifts the apparent position of the sun by about 34 minutes of arc — roughly the sun's own apparent width — so the sun can be seen while it is geometrically below the horizon. Both sides of this argument accept refraction; they disagree over how much of a wide level sightline it can explain. |
| Selenelion | An eclipsed moon visible while the sun is also above the horizon, which on the geometry alone should not be possible. It is a real, photographed observation and atmospheric refraction is the mainstream explanation: both bodies are lifted in apparent position at the same time. |
| Spotlight effect | A term used mainly inside flat-earth writing for the reading in which sunlight falls on one circular patch of the plane at a time, giving daylight in one region and darkness elsewhere without the sun ever passing below the surface. |
| Stereōma (στερέωμα) | The Greek word the Septuagint uses for the firmament of Genesis 1, built on stereos, solid. It is the step that gives the English “firmament” its sense of something hard rather than something merely spread out. |
| Vanishing point | The point in a perspective drawing where parallel lines appear to meet. Flat-earth writing leans on the term when arguing that distant objects disappear through distance and the convergence of sightlines rather than by passing below a curved horizon. |
| Zetetic method | From the Greek zetein, to seek. Rowbotham's name for reasoning from direct observation and experiment rather than from an assumed system, which he contrasted with what he called the theoretical method. The Universal Zetetic Society, formed in England after his death, kept the term and published a magazine edited by Lady Elizabeth Blount. |
| Level (spirit level) | An instrument in which a bubble in liquid marks a horizontal line. It is the flat-earth case's core tool, on the argument that a level line over still water should stay level — and the globe model's answer is that a level line is a tangent, touching the surface at one point and rising away from it. |
Where these terms are used
Most of this list appears in three places on the site. The model page uses the structural vocabulary — plane, rim, dome, spotlight, close and far sun. The map page uses the projection vocabulary — azimuthal equidistant, great circle, gnomonic, Mercator. The firmament page uses the textual vocabulary — raqia, stereōma, firmamentum, empyrean. The measurement terms — refraction, dip of the horizon, level, oblate spheroid — belong to Try it yourself, where they are used against actual observations, and to Objections, answered, where they are used against us.
This page presents the flat-earth interpretation as its subject matter. It is a belief-based reading of the observations, not a scientific finding — see About for how we frame claims and for the mainstream sources.