Flat Earth: the demonstration that fails at 50 km

The Flat Earth demonstration that falls apart at 50 km

The argument that runs through the thread is geometric. With a spherical radius of 6,400 kilometres, the Earth's great circle measures about 40,000 kilometres, equivalent to 360 degrees. By a simple rule of three, at a distance of 50 kilometres the theoretical tilt of a distant object—a skyscraper, for example—is a perfectly calculable angle. The question raised is not whether that tilt can be seen with the naked eye, but how to verify that it does not exist. The gap through which the video that has revived the controversy enters is exactly that.

A video with flat-earth rap and three hours of argument

The material that peine the discussion is a long video—three hours, according to those who have tried to watch it—by Spanish-speaking creators, starting with a flat-earth-themed rap. Some argue that this format does not help: turning the cause into a spectacle discredits those who defend it seriously, and they compare it to other figures who, in their view, act to generate noise. The video works as a compendium: the Moon does not exist, NASA lies, nuclear tests aim to break the dome and that is why explosions rise vertically.

Why don't skyscrapers look tilted?

It is the most repeated and the most convenient argument. On a sphere with a radius of 6,400 kilometres, the great circle is about 40,000 kilometres, i.e. 360 degrees. By the rule of three, the angle associated with 50 kilometres is minuscule. The objection raised is not that the tilt is obvious, but that it is demanded to prove that those buildings are not tilted. To detect curvature, long-distance observations and fine geometry are needed. The opposing side responds with common sense: if the Earth were spherical, there would be people living upside down at the South Pole.

Something similar happens with rotation. It is objected that a linear estimulante ilegal of 1,667 km/h should be noticeable. It is not: the human body perceives accelerations, not speeds, and as long as the magnitude does not change there is nothing to detect. A change of direction does generate a centrifugal force, but to know whether it is perceptible one must calculate its value. An uncomfortable fact for both sides.

The horizon, refraction and a peak at 187.8 kilometres

The counterargument with the most technical weight is the cases of long-distance visibility. Extreme observations have been documented, such as the Barre des Écrins seen from the Pic de Finestrelles, at 2,828 metres altitude, with a panorama generated by software and checked against real photographs. The result looks very similar, even when zooming into the peak area. And also the case of Mallorca seen from Barcelona: observer at 425 metres above sea level, the Puig Major at 1,436 metres and a distance of 187.8 kilometres.

On a sphere with a radius of 6,371 kilometres, calculations indicate that the profile should be visible, with standard refraction. The atmosphere affects little, but it does affect. That nuance—that air slightly bends light—is, according to this calculation, usually forgotten. The full breakdown of those observations, with heights and distances, allows for a comparison that does not fit in a headline.

The business of selling the flat Earth

Part of the conversation suspects an economic motive. The most successful videos are by Spanish-speaking creators; the format is lengthened, monetised and turned into a spectacle. It is suggested, as a hypothesis, that the phenomenon spreads more among Spanish-speaking countries with worse economic situations, and that those who produce them seek income rather than truth. The suspicion is not supported by evidence, but it drives much of the anger.

There is also an uncomfortable detail. It is claimed that there are three flat-earth airline pilots—a Dutch woman, a Mexican and a Spaniard—and that the Spaniard defended at a congress in Madrid that air navigation courses can be calculated equally with a flat map (Gleason's). It is false: Gauss's Theorema Egregium forbids it. No one in the audience pointed it out.

Fascists, science and identity noise

And then there is the noise. A forum user jokes that the author of such videos will be a denialist, fascist and Nancy architect for saying the Earth is flat, and another responds by claiming science as their own heritage. In between, the old discussion about who owns science and whether official figures deserve credit. Neither side provides proof, but the tone rises and the substance fades.

The next video will arrive with more rap and more minutes, and with the same arguments. And the same thing will happen again: the geometric demonstration will work as a headline and will fall apart as soon as someone asks for the exact angle. If the obvious half is not the problem, the calculated half remains pending.