lol...
the earth is a sphere... because during a moon eclipse... displaying a line between the sun... the earth and the moon in this order...the earth shadow curvature on the moon doesn't change...
if the earth was a disc... this shadow shape would change with time during the eclipse...
indeed... if it is supposed that the moon turns around the earth... as strongly suggested by its phases... such phases that suggest the sphericity of the moon as well, it seems to me...
and if it is supposed that the earth itself has some motion during the eclipse...
during these 2 motions... the earth shape seen from the moon would loose its circular presentation to get a more elongated shape... and this would have been somewhat showed on the eclipsed moon in the sky...
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lol...
the sphericity of the earth has been imagined... with its dimension even calculated with a good precision since the antiquity... with the famous measures of the shadow of an obelisk in alexandria, egypt, the day of the june sostice at noon... while the sun was at a zenithal position in aswan, hundreds kilometers to the south of this city... under the tropic of cancer...lol
indeed... the dimension of the shadow of the obelisk allows to calculate the height of the sun in the alexandria sky... and therefore the angle between this city and aswan... if it is supposed that they are on a same line... meridian... along a spherical earth...
once this angle is associated with the distance between the two locations... the circumference of the earth can be deduced by a proportionnality rule...
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these two points above have been noticed during the antiquity...
well before fernando magellan... who demonstrated by his trip what humans imagined centuries before him...
well before galileo...who clearly observed turning motions of the jupiter moons around their planet... and the phases of venus... observations implying that all these worlds should be spherical and not like discs...
well before the effective observation of neptune by an astronomical instrument... while the very weak magnitude of this planet makes it almost impossible to discern with human eyes... and that the ideas provided by the gravitation largely helped to discover... another clear proof of the general sphericity of the planets... included the earth...
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now... meat rod... indeed... everything is not a sphere around us... lol... like the asteroids for example...
but for the earth... yes... according to the previous points... it is a sphere...
lol