Was Christopher Columbus acting on any tips from prior travellers?

Factual Questions
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[quote=“md-2000, post:7, topic:939123”]
It was one of life’s happy coincidences that he ran into the Americas. The intelligentsia of Europe believed the original Greek number of 8,000 miles in diameter, making China over 12,000 miles west - way too far for the ships of the day. This is why he had a hard time selling his idea to the courts of Europe - until Portugal was monopolizing the route sailing around Africa, so

I was just reading about the Voyage of Magellan.

Magellan was acting was acting on the very best "science’ of his day, he even used a early globe (which is a marvel as it seems to show Antarctica). But the best mapmakers and globe makers of the day also got the size of the Earth wrong- Magellan was sure the Spice islands were only a few days, maybe a week from the tip of South America. He was terribly wrong.

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I’m also surprised that by Magellan’s time there would be any dispute about the size of the earth. By 1500 Europeans regularly could travel from the south shore of the Mediterranean to Britain and Scandinavia. they had a widespread scientific community which shared information. They knew how the stars changed when travelling north. Repeating the Greek experiment with a much wider north-south angle was probably something easy to do, and could be done measuring stars, instead of waiting by a well. .

I suspect Magellan’s failing was not imagining that you could travel well over the 3,000 miles Columbus did, and not regularly encounter some sort of landfall.

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Slightly off topic: Glad to see this in the SDMB again because I posted in late spring 2021 (thought it was this thread but I guess it was another) about research being done to determine Columbus’ ancestry through DNA testing, the results of which were to be released in late 2021 or shortly thereafter. There’s only a brief mention of the research in the related Wikipedia entry.

So, just a reminder to Dopers to keep an eye out for this. I’ve been looking forward to it and the release of Peter Jackson’s Let It Be as the highlights of an otherwise uneventful year (for me).

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No, he clearly expected the Spice islands themselves to be close to the Straights, and he was working with the best data at the time.

So the size of the Earth wasn’t some crazy idea just by Columbus. It was the prevailing concepts in Western Europe at that time.

And sure Eratosthenes had different figures but few knew of him. Ptolemy, instead- was well known and highly regarded.

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But Columbus’ other failure (or wishful thinking) was to grossly overestimate the distance to Cathay based on Marco Polo’s memoirs, thus significantly reducing the distance to travel. (IIRC, 12,000 miles instead of 6,000) Did Magellan rely on this fallacy also?

(Columbus also fudged his numbers by assuming a different definition of a stadia so his earth diameter was even smaller than Ptolemy’s number)

Google maps tell me the distance from the longitude of Venice to Indonesia is about 7,000 miles.

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No, but Columbus apparently relied on other data that showed Japan to be much further off the coast. Early maps show it like that.

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Unlike Columbus, Magellan didn’t sail west toward Asia because he thought it was closer than sailing east. He sailed west because the Portuguese threatened Spanish ships sailing east.

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To clarify - Columbus also exaggerated the distance Marco Polo travelled east as 10,000 (or 12,000?) miles instead of 6000.
He claimed the earth to be 4500 miles in diameter using a different definition of a stadia, about 14,000 miles in circumference. Plus the distance Venice to Spain, and voila - Japan and Cathay should be just over 3,000 miles west.

All the educated court scientists at the time noted he was fudging these numbers, his choice for global diameter was too small, and Asia was well beyond capability of vessels of the time. Magellan almost proved them right trying to cross the Pacific.