This web page describes observations that show the earth is a sphere and the history of these observations. The round shape of the Earth may be inferred from the existence of a horizon at sea. Ancient Greeks deduced it from the shape of the Earth's shadow when the Moon is eclipsed and from stars visible only in southern countries. Eratosthenes accurately estimated the size of the Earth, but Columbus based his plans on an incorrect value, by which India would be much closer to Spain. This is part of a large web site, "From Stargazers to Starships" the presents physics concepts using space science and an historical perspective. Spanish, French, and Italian translations are available, as well as links to lesson plans for teachers.
%0 Electronic Source %A Stern, David %D December 12, 2004 %T The Round Earth and Christopher Columbus %V 2015 %N 24 November 2015 %8 December 12, 2004 %9 text/html %U http://www.phy6.org/stargaze/Scolumb.htm
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