Flat Earth
The Earth's shape was measured to within a few percent in the third century BC and has been confirmed by every method since. Modern flat-Earth belief is not a survival of ancient cosmology; it is a twenty-first-century community built on distrust of institutions.
Why this verdict
Debunked continuously since antiquity, and most decisively by flat-Earth believers' own experiments — including a 2018 ring-laser gyroscope test that detected Earth's rotation and was rejected by the people who ran it.
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01The claim
That the Earth is a flat disc with the Arctic at the centre and a wall of ice at the rim, that the sun and moon are small local objects circling above it, that gravity is an invention and objects simply fall, and that space agencies worldwide fabricate imagery to conceal this.
02Where it came from
The modern version begins with Samuel Rowbotham, who in 1838 conducted an experiment on the Old Bedford River in Cambridgeshire and claimed to see a boat six miles away that curvature should have hidden. He published under the name 'Parallax'. The experiment was repeated by Alfred Russel Wallace in 1870 with a corrected method that accounted for atmospheric refraction, and produced the opposite result; Rowbotham's followers refused to accept it. The belief persisted through the Flat Earth Society and then, from about 2014, expanded enormously through YouTube's recommendation system.
The medieval part of the story is itself a myth: educated Europeans had known the Earth was a sphere throughout the Middle Ages, and the tale that Columbus's contemporaries feared sailing off the edge was popularised by Washington Irving's 1828 fiction.
03What the record shows
✕ DEBUNKED — Investigated and refuted. Here is what actually happened.
Eratosthenes measured the Earth's circumference around 240 BC by comparing shadow angles at Syene and Alexandria, obtaining a figure within a few percent of the modern value. The method requires only a stick, and it fails on a flat Earth: the sun's rays would not arrive at different angles at different latitudes under a local sun.
Evidence available to anyone: ships disappear hull-first over the horizon in every direction; the timing of lunar eclipses differs by longitude and the Earth's shadow on the Moon is always circular; the constellations visible from Sydney are not the ones visible from Reykjavík, and the southern sky rotates in the opposite direction; long-haul flights between southern-hemisphere cities take routes that are absurdly indirect on any flat map; the Coriolis effect must be corrected for in artillery and in weather models, and works in opposite senses in the two hemispheres.
The most telling evidence came from believers. The 2018 documentary Behind the Curve records two experiments run by flat-Earth advocates. One used a ring-laser gyroscope to look for rotation and detected a 15-degree-per-hour drift — exactly Earth's rotation rate. The other used two men, three posts and a light, and produced a result requiring the light to be raised to account for curvature. In both cases the experimenters treated the outcome as an artefact to be explained away. This is the clearest available demonstration that the belief is not evidentiary.
04What it cost
Direct harm is limited — one self-taught rocket builder died in 2020 attempting to reach altitude to see for himself — but the community functions as an entry point. Its epistemics generalise: all institutions lie, personal perception outranks measurement, and anyone who disagrees is either fooled or paid. Researchers studying radicalisation pathways repeatedly find flat-Earth content as a gateway rather than a terminus.