A Stick in the Sand

I haven’t been much on EVE this past week. Reason for that being that first I was abroad, and then my wife broke her arm (she fell, slipped on ice, I’m not to blame here, but why do I feel the need to point that out?) so she’s now at home with me for four weeks, meaning I can’t just log in, undock and tune out.

In the meantime, we’ve been watching a few episodes of Cosmos: A Personal Voyage, and I must say I recommend it. It’s old, so the special effects in use aren’t exactly up to date. And there’s a certain hippieness about it, a bit more Dharma than Greg, if you will, something that I guess will alienate some, and intrigue others. Carl Sagan is, however, king, and some of the anecdotes he tells throughout the programs are memorable beyond compare. Thus I will now retell the story of one guy called Erastosthenes. I will of course make errors and changes, all in the sake of improving the story rather than diminish it.

Erastosthenes lived in Alexandria, back in the day when the Great Library was still around. In a scroll he read how there in one town further south, at a certain date and at a certain time, the sun was at such a position in the sky that there were no shadows cast by objects on the ground. This intrigued the man, so he decided to check if that was true. Thus he put a stick in the sand and waited for that same date and time to arrive. Lo and behold, the day came and went, and the damn stick still cast a shadow.

How could this be? It was an accepted truth at this time that the earth was flat, and the sun was at an infinite distance from the earth. But then how could it seem that the sun was at different positions, and thus causing objects to cast different lengths of shadow, at the same time?

The conclusion of course was that the Earth was round. However, this isn’t the astonishing thing about Erathosthenes. Anyone can deduct the roundness of the earth merely from observing a ship going over the horizon. That’s kid’s stuff. No, what mr. E here did was to first measure the distance between his stick in Alexandria and Swenet (as it was then called) by having some poor sod walk the distance. And then through the use of some basic geometry he calculated the circumference of the earth.

He got it wrong, of course.

By 1%.

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~ by Shaun Livingstone on March 27, 2009.

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