In this solo monologue, Lois Letchford reads a section about the ancient astronomer and geographer Ptolemy, emphasizing his role as a compiler of existing knowledge and the lasting impact of his errors. She critiques the historical tendency to treat ancient texts as immutable authority, illustrating how Ptolemy’s underestimated Earth diameter, transmitted through the Geographica, misled Christopher Columbus into under‑estimating the distance to the Indies. Letchford reflects on the nature of assumptions, the value of being wrong as a learning step, and notes Ptolemy’s other works in optics, astrology, music, and mathematics. The video concludes with a call to action for viewers to engage with historical content.
Chapters
Hello, I'm Lois Letchford, author of the book Reversed: A Memoir and literacy problem solver, reading about Ptolemy, Ptolemy number 2. And I'm not going to read the whole chapter but just section of it. Ptolemy's great contribution to the world of his time was to gather existing knowledge and present it in in works of encyclopedic scope. Today we accept that human knowledge is in a constant state of flux, with old ideas being revised in favor of new ones. Our ancestors didn't have that attitude. Ptolemy's countless errors were the errors of his era. The blame for the fact that this world— his works misled Western thought for so very long lies with the human tendency to regard ancient texts as sacrosanct just because of their ancientness. Centuries after Ptolemy's time, people could face persecution or even death if they disagreed with the version of the way the universe operated. Galileo was one to bear the brunt of this. The lessons to be learned from centuries-long Ptolemy fiasco is that we must recognize that while the ancients very often had wisdom, they grievously lacked information and their ideas were limited accordingly. It's thus foolhardy to see them as unchangeable authorities on Any aspect of knowledge. And that causes me to think about even knowledge today. You know, is it all unchangeable? How do we go about finding it? These people were making assumptions at the beginning, and that's what happens when you make an assumption. You have to make an assumption, then you have to prove it. Sometimes you will be right, but sometimes you will be wrong. But just because it's wrong doesn't mean it's worthless. You've ruled out one option, and that's the starting point. We get things wrong, and guess what? It's okay to get things wrong because you're learning. And that's my point. It's okay to get things wrong. Ptolemy did, and he influenced the world. And one of the biggest influences, which I didn't read here to you, But I will now was on Christopher Columbus. The Geographica was translated from Arabic. This is the Geographica from Arabic into Latin in 1406, and had a profound effect on the thinking of Christopher Columbus. Unfortunately for Columbus, in deciding on a figure for the Earth's diameter, Ptolemy chose the estimate. Produced by Posidonius, about 5,725 miles, rather than the far more accurate one derived a century earlier by Eratosthenes, about 7,960 miles, nearly 8,000 miles. Thus Columbus thought the westward distance from Europe to the Indies was a lot shorter than it actually was. He had realized— had he realized the true figure, he may never have set off because he had known he couldn't take sufficient supplies to last the voyage. Luckily for him and his crew, he discovered the West Indies instead. Ptolemy wrote further treatises One on optics was, in the Arabic translation, very influential on the work of Alhazm. The latter considerably revised it. Then there's the four books on astrology. He wrote music, maths, and other topics. So that's the guy Ptolemy. Know it. It's a name. It's unusual spelling because it's P T, and we don't. P-T-O-L-E-M-Y. Ptolemy. Thank you. Enjoy. Hit like, hit subscribe, and share, and find out about the history of the ancient world and scientific discoveries.
