Intrigued by the phenomenon, Eratosthenes decided make an observation in Alexandria, located about 800 kilometers north of Siena. There, on the same day and at the same time, he noticed that a vertical stick did cast a definite shadow. The discrepancy led him to a fundamental question: how was it possible that in one place there was no shadow and in another there was, at the same time? Eratosthenes deduced that the only explanation was that the earth’s surface was curved.
A lot of time has passed since then, but the flat earthers are still among us.
The home experiment. For centuries, the idea of a flat Earth has outlived telescopes, satellites and lunar missions. Despite the overwhelming evidence, from the images taken from space and the established physical principles from Aristotleflat earthers have continued searching for the edge of the planet, organizing expeditions to Antarctica or navigations to the supposed “end of the world” that invariably end with the same discovery: that the edge does not exist.
Be that as it may, an anonymous Reddit user has dismantled once again his entire creed without leaving home. Armed only with a security camera, the shadow of his garage and the patience of an entire year, he managed to record a test as simple as it was incontestable: the movement of the Sun drawing a figure of eight perfect on the ground.
The footprint of the Sun. Between March 2024 and March 2025, this user (under the alias RedditorofReddit07) marked daily, at the same time, the position of the end of a shadow cast by a corner of his garage. After twelve months, the yellow dots traced on the cement an asymmetric curve in the form of infinity: an analemma.
This phenomenon, documented by astronomers for centuriesis the direct result of the 23.5 degree tilt of the Earth’s axis and the planet’s elliptical orbit around the sun. In the summer months, the star reaches the highest point of the analemma; in winter, the lowest; and during the intermediate seasons the rest of the figure is drawn. Each latitude generates a slightly different shape, but they all share the same essence: an Earth that moves, rotates and tilts, not a motionless disk under a celestial lantern.
The physics of time. The analemma not only reveals the movement of the planet, but also the difference between solar time and time measured by clocks. In theory, noon always occurs at 12 o’clock, but the Sun does not reach its highest point at exactly the same time every day. This variation, a consequence of the inclined axis and the unequal speed with which the Earth travels its orbit, is the reason why the analemma adopts a figure-eight shape.
Science sums it up in a formula called the “Equation of Time,” an adjustment that explains why solar days vary in length and why the apparent position of the Sun advances or lags throughout the year. This mismatch is as predictable as it is beautiful, and can only be explained by a spherical planet that orbit a starnot by a flat disk with a wandering Sun that rises and falls without altering its size.
The impossible refutation. In the flat earth modelsthe Sun moves on a plane, like a lamp on a table, projecting its light in circles on the surface. If that were true, the end of a shadow always observed at the same time should remain fixed throughout the year. However, the garage experiment shows exactly the opposite: a harmonic displacement that only fits the heliocentric model.
Reproducing this effect in a flat world would require, in addition to an act of faith without a network, that the Sun change its trajectory, height and speed in an absurd way, violating the very laws of optics and gravity that its alternative model allows. The flat earthers themselves, faced with such evidence, barely manage to develop new explanations that are more imaginative than scientific.
The method. He merit of the experiment It lies not in its complexity, but rather in its humility. Without telescopes or laboratories, a simple fixed camera and a daily routine were enough to record the annual dance of the Earth in front of the Sun. Each shadow point marked on the cement is a slap to the conspiratorial noise that floods the internet.
In times when science is forced to defend the obvious, an ordinary garage has become an observatory and an anonymous user a popularizer. He already said it Carl Sagan himselfalthough he only needed a stick to dismantle conspiracies.
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