Eratosthenes Measures the Earth. ca. June, 240 B.C.
By the 5th century B.C., it was widely accepted that the Earth is a sphere. This is a critical point, as there is a widespread misconception that ancient peoples thought the Earth was flat.
Eratosthenes’ most famous accomplishment is his measurement of the circumference of Earth. He recorded the details of this measurement in a manuscript that is now lost, but his technique has been described by other Greek historians and writers.
Eratosthenes had heard from travelers about a well in Syene (now Aswan, Egypt) with an interesting property: at noon on the summer solstice, which occurs about June 21 every year, the sun illuminated the entire bottom of this well, without casting any shadows, indicating that the sun was directly overhead. Eratosthenes then measured the angle of a shadow cast by a stick at noon on the summer solstice in Alexandria, and found it made an angle of about 7.2 degrees, or about 1/50 of a complete circle. By knowing the distance between Syene and Alexandria through the help of professional surveyors, he was able to report that the circumference of the earth was 250,000 stadia or between 24,000 and 29,000 miles.
Carl Sagan
"It's the most natural thing in the world to think that Earth is not only the center of the solar system, but the universe-put there for our edification or amusement. That has been the view of people all over the world, all through human history. And even today, even this minute, it is still with us. We talk about the sun rising and the sun setting. There's nothing in our language to indicate that it is, in fact, the Earth that's turning.
I think that while most people had been taught that the Earth is round, in their heart of hearts they didn't believe it. And it was only after the advent of space exploration and in particular, the early photographs of Earth-mainly from manned missions looking back and seeing it as a beautiful blue-white jewel set against the black velvet background of space, that people suddenly got a sense of where we are." [Carl Sagan (NASA Magazine 1992)]
AI and SVP explores the Flat Earth Myth and Misbelief
Summary
The Earth is spherical because gravity, or the force of convergence, pulls everything toward the center of the planet. This creates a surface that appears flat locally (like standing on a vast plain) but curves globally, like a ball. A gyroscope, which resists changes in its orientation, will naturally align its spinning axis with gravity’s pull, always pointing to the Earth's center. This shows that gravity acts consistently toward a single point, supporting the Earth's round shape.
All the molecules on Earth behave like tiny gyroscopes, locked into the same gravitational pull and rotational motion. They act as one unified system, responding together to the forces of gravity and inertia caused by Earth's spin and movement through space. This unified behavior keeps everything aligned toward the Earth's center, demonstrating the natural harmony of its spherical structure. Simply put, the shape of the Earth and the behavior of its materials all confirm it’s a globe.
Read more here: ChatGPT and SVP explores the Flat Earth Myth and Misbelief [1/14/25]: https://chatgpt.com/share/67866a8e-6788-800d-90f4-ae7cb551f0bb
See Also