I can be persuaded to forgive President Obama when he invoked a mythcal past filled with people who believed in a flat earth. He is, after all, not trained in history or science or history of science. And he doesn’t pretend to have any expertise in history of science. It is more difficult to forgive SPACE.com for invoking the same myth. SPACE.com purports to be “the world’s No. 1 source for news of astronomy, skywatching, space exploration, commercial spaceflight and related technologies” and to have a “team of experienced reporters.” Such aspirations and the standards they imply should prevent SPACE.com from publishing any reference to a flat-earth past. Alas, those implicit standards seem to have had no effect on the historical accuracy of a recent article. In what can best be described as selective genealogy, Nola Taylor Redd claims that in the third century BCE “[w]hen most people believed the world was flat,” Eratosthenes measured its circumference:
When most people believed the world was flat, the notable Greek mathematician, astronomer and geographer Eratosthenes (276 BCE- 195 BCE) used the sun to measure the size of the round Earth. His measurement of 24,660 miles (39,690 kilometers) was only 211 miles (340 km) off the true measurement.
This paragraph is alternately wrong and misleading. It is wrong to claim that during Eratosthenes life “most people believed the world was flat.” While it’s hard to know what “most people believed,” certainly most people whom we might call astronomers understood the earth was spherical. They could and did put forward compelling arguments for the earth’s sphericity, often grounding those arguments in philosophical assumptions or empirical observations or both. A century or so earlier Aristotle had already reported that certain mathematicians had calculated the size of the earth. When Eratosthenes devised a way to calculate the earth’s circumference, he was not unusual in his convictions. He calculated that the earth’s circumference was 252,000 stades, a number he probably rounded up from 250,000 so that it was divisible by 60. How long a stades was remains an open question. Most likely, Eratosthenes’ value would convert to something between 24,663 and 27,967 miles.
It is regrettable when a source like SPACE.com propagates myths like this. Even in a genealogical article, there is little reason to traffic in obvious historical myths.
[Reposted at PACHS.]