[aprssig] Re: Metric [[furlongs per fortnight]]

Steve Dimse steve at dimse.com
Fri Sep 7 13:57:24 CDT 2007

On Sep 7, 2007, at 1:05 PM, Mark Fellhauer wrote:

> You follow a celestial reference point.   Um, that would be a star.

In an imprecise sense you are right, in that the sun is a star. The  
first known measurement of the earth's diameter was calculated using  
the angle of the sun during the summer solstice. In Egypt it was  
known to be 90 degrees, because the sun shone on the bottom of deep  
well (by coincidence along the Tropic of Cancer) but in Greece  
Hipparcos measured a smaller angle, and from that he calculated the  
value of the earth's diameter with less than 5% error.

An interesting aside, the Romans "improved" the calculation to an  
error of almost 40%, and this erroneous value was believed for a long  
time. Despite what you may have heard in grade school, no one, not  
even the lowest sailor with Columbus, believed the earth was flat in  
1492. However, because they thought the earth was much smaller than  
it really was, they expected to hit the orient long before they  
landed in the Bahamas. It was this unexpected delay in landfall that  
nearly led to the mutiny we were told about. I think the truth is a  
far more interesting story, but for some reason people prefer the  
earth is flat story...

Steve K4HG

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