canopus56 wrote:
What is the visible distance from the horizon on the Moon and Earth
and for any given planet of radius R, how can this be computed? -

For any airless, spherical world of radius R, an observer at altitude h
(h R) can see to a distance of sqrt(2Rh). Thus, for instance, the
Moon has a radius of 3,500 km, more or less. An observer at an altitude
of 10 m (that is, 0.01 km) can see to a horizon distance of

sqrt(2*3,500*0.01) = sqrt(70)

or about 8.3 km. On the Earth, atmospheric refraction extends this
distance, and per a suggestion from Andrew Young, the formula is closer
to sqrt(2.3Rh).

--
Brian Tung
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