15-07-2021, 07:40 PM
11
Re: Carl Sagan
Originally Posted by Judd
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Same here. With basic tools and an enquiring mind - who would have thought that the bottom of a well to the south of Alexandria could be seen at midday and columns cast no shadows and cause Eratosthenes to do an experiment to see if the same applied at midday in Alexandria. It didn't, so he deduced that the Earth was curved and set out to prove it.
I would have thought that midday was kinda measured at both places as being the precise moment at which the sun was directly overhead and there were no shadows. To my knowledge, they didn't have phones nor indeed accurate watches back then, so how did he know at all, yet alone precisely, when "simultaneous" was??
15-07-2021, 08:28 PM
12
Re: Carl Sagan
Originally Posted by Dextrous63
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The only thing that I still don't get is how Eratosthenes knew when midday was in comparison to whatever distance it was away from the other place?I would have thought that midday was kinda measured at both places as being the precise moment at which the sun was directly overhead and there were no shadows. To my knowledge, they didn't have phones nor indeed accurate watches back then, so how did he know at all, yet alone precisely, when "simultaneous" was??
15-07-2021, 08:41 PM
13
Re: Carl Sagan
Originally Posted by Judd
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It was midsummer's day when the sun cast no shadow south of Alexandria because the sun was directly overhead, but cast a shadow on midsummer's day in Alexandria. If Alexandria and the other place were on the same latitude, no shadow would be seen at either location, but the other place was further south.
15-07-2021, 08:46 PM
15
Re: Carl Sagan
Originally Posted by Dextrous63
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Gotcha. He must have had a very good memory to remember that there wasn't a shadow in a place he'd been at exactly 365 days (or a multiple thereof) before. Guess that's one of the benefits of not having tv's to distract him.
15-07-2021, 08:56 PM
16
Re: Carl Sagan
Originally Posted by Judd
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He didn't need one, it was written on a scroll sent to the library.
15-07-2021, 09:03 PM
18
Re: Carl Sagan
Originally Posted by Judd
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It may be prudent. 
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