When and how did humans first realize that it was darker/lighter on other parts of earth at the same time?

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I get how time zones were established, and I get how people knew the earth was round thousands of years ago, so I assume that it was hypothesized that some areas of earth were darker/lighter than others at the same time. I feel like it was kind of unprovable though due to limitation. At what point did we actually confirm that it was indeed night time somewhere else when it was daytime on the opposite side of the world? And how was the found out?

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Anonymous 0 Comments

There were a lot of early observations.

Like u/Xemylixa says, the “proof” is that a solar eclipse would occur nearly simultaneously in Anatolia and India, but one would report it at sunset and the other says it happened at noon.

But you dont need rare events to make an educated guess. The ancients had calculated that the earth was round by measuring shadows at noon in Egypt and Greece on the same day and getting different angles. They also knew that the days were much longer in the winter in Egypt than they were in the barbarian lands to the far north.

From this they correctly guessed that the Earth was a sphere illuminated from a distant light source and even attempted to calculate the “height” of the sun by triangulation of the sun’s rays at different locations, but it’s so unfathomably far that they could never measure angles accurately enough to estimate the distance beyond “really, really high”

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