Re: AT WHAT POINT ABOVE THE EARTH'S SURFACE DOES IT'S CURVATURE BECOME APPARENT

Hi Larry,

Actually, the Earth's curvature is apparent from ground level! Imagine standing on the beach, looking at a sailing ship that's coming towards you. You see the mast first, then the rest of the ship, and that's because the round Earth means the distance to the horizon is finite. If the Earth were flat, the horizon would be an infinite distance away, and we'd be able to see "to the edge of the Earth".

There are some more MADSci answers that talk about this:
What would the horizon look like on a very large planet?
How far can you see, horizon-to-horizon, from an airplane at 37,000 feet?
(try doing a search on 'Earth horizon' for more info)

Pauline