Effects of the shadow of a city in the sky?

If there was a city using antigrav to maintain a position over Kolkata, and it had approximately the area of New York City (roughly 300 square miles, or 780 square kilometers), what altitude would it have to hold to avoid detrimentally shading the land below? For reference, the city must be high enough to function as a spaceport. It is roughly circular, with a radius of around 16 kilometers and a thickness of 5 kilometers at the edges, tapering at the planet-side and the space-side for an "axial" height of 10 kilometers.

Detrimental, in this context, means uncomfortably noticeable and/or effecting everyday life; think "partial solar eclipse."

posted over 5 years ago

G. B. Robinson‭

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