Flat Earth Society

A vintage-style emblem with the words Flat Earth Society framed by little stars, around a flat, disc-shaped Earth with green continents, blue seas and a rocky underside floating in space. It looks like a sincere club badge – which is exactly what makes it funny.

The old line goes – the Flat Earth Society has members all around the globe. The sentence refutes itself, which is the best kind of irony. Wearing the badge is a deadpan way of taking a side for evidence, reason and a sense of humour, without having to say so.

Yes. Samuel Shenton founded the International Flat Earth Research Society in England in 1956, building on the 19th-century ideas of Samuel Rowbotham, whose Bedford Level experiment (1838) claimed to show that water stays flat over long distances. A new Flat Earth Society was relaunched online in 2004. Its claims have been refuted by every kind of measurement since antiquity.

No – that is a modern myth. Educated medieval scholars, from Bede to the widely used textbook De sphaera by Sacrobosco (c. 1230), took the Earth to be a sphere. The idea that Columbus had to prove it round was popularised by Washington Irving's Columbus biography of 1828 and later by 19th-century writers on the supposed war between science and religion.

Greek thinkers. The idea is attributed to Pythagoras and Parmenides in the 6th–5th century BC, and Aristotle gave the first surviving arguments in On the Heavens (c. 350 BC) – the Earth's shadow on the Moon during a lunar eclipse is always curved, and travelling north or south changes which stars you can see.

Around 240 BC Eratosthenes, librarian in Alexandria, learned that at noon on the summer solstice the Sun stood directly overhead at Syene, while in Alexandria a vertical stick cast a shadow of about 7 degrees, or a fiftieth of a circle. Multiplying the distance between the cities by 50 gave a circumference of about 250,000 stadia – remarkably close to the real value.

Philosophically it is a lesson in epistemology. Flat-earthers trust what their own eyes show – a flat horizon – over the testimony of experts, and explain away every counter-evidence as a conspiracy. That makes the belief unfalsifiable in Karl Popper's sense (Logik der Forschung, 1934; in English The Logic of Scientific Discovery, 1959) – no possible observation is allowed to count against it, which is exactly what marks it as unscientific.

For science teachers, physics and philosophy students, sceptics and anyone who enjoys irony delivered with a straight face. The design is available as a sweatshirt, premium hoodie, classic t-shirt, women's t-shirt, mug and sticker.