A map of the four voyages of the Italian navigator, Christopher Columbus. Crucially, he claimed that when the explorer told Spanish geographers the earth was not actually flat, they refused to believe him, even questioning his faith and endangering his life. And when his book became a runaway bestseller, the supposed confrontation between the rational explorer and the dogmatic official was accepted as truth.
Over the years—and with the help of Antoine-Jean Letronne , a French author—the legend took hold. Though Columbus never proved Earth was round, he did manage to upset long-held dogma in another way when he ran across a continent nobody in Europe even knew was there.
But if you see something that doesn't look right, click here to contact us! But how do you know the shape of the Earth is curved? What piece of knowledge convinced you of this fact? The likely answer is that we have pictures of the Earth from outer space showing its curvature did the trick. But this was a fact that was known long before we had any cameras in space.
In fact, without this knowledge, we would have never made it to space. I know not everyone was taught this, but many were, myself included, and he is still credited by some for this discovery.
This is simply not true. In fact, as an aside, Columbus did not even fully circumnavigate the Earth, he was simply the first modern European to land in the Americas. Much farther. In fact, they almost never are. The heliocentric model was proposed by Copernicus, and proven by several other scientists, Galileo included. Atoms were proposed by Democritus and proven much later. Evolution was known prior to Darwin, but he showed a mechanism through which it could happen natural selection.
In short, science is a process that takes ideas through a very long period — sometimes centuries — of proposal, study, and questioning.
The idea of a spherical Earth is no different. So I cannot drop the name of a super-genius who came up with, and proved, a spherical Earth all on his own, but I can give you the names of its contributors.
The initial assertion is often credited to ancient Greek philosophers, such as Pythagoras and Aristotle. They cited simple observations, such as the changing position of stars as you travel north or south, the sinking of ships below the horizon, and the shape of the moon. Most of their observations are ones you can make on your own as well. But one of the more noteworthy early contributors to the shape of the Earth would be Eratosthenes. He made many contributions to science and the understanding of the universe, but here I wish to tell you about his measurement of the circumference of the Earth.
Known as one of the foremost scholars of the time, Eratosthenes produced impressive works in astronomy, mathematics, geography, philosophy, and poetry. Eratosthenes was especially proud of his solution to the problem of doubling a cube, and is now well known for developing the sieve of Eratosthenes, a method of finding prime numbers.
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 was fascinated with geography and planned to make a map of the entire world. He realized he needed to know the size of Earth. 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. He realized that if he knew the distance from Alexandria to Syene, he could easily calculate the circumference of Earth. But in those days it was extremely difficult to determine distance with any accuracy. Some distances between cities were measured by the time it took a camel caravan to travel from one city to the other.
But camels have a tendency to wander and to walk at varying speeds. So Eratosthenes hired bematists, professional surveyors trained to walk with equal length steps. They found that Syene lies about stadia from Alexandria.
Eratosthenes then used this to calculate the circumference of the Earth to be about , stadia. Modern scholars disagree about the length of the stadium used by Eratosthenes.
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