Tree Trunk Illusion: Does it Disappear Over the Horizon?

AI Thread Summary
The discussion centers on the perception of a tree's trunk as an observer moves away from it on a flat plane. It argues that the trunk does not disappear below the horizon, contradicting a claim made by another participant. The conversation highlights the importance of defining conditions accurately, particularly whether the surface is flat or spherical. It references Nathaniel Bowditch's work, which provides a method for estimating horizon distance based on eye height. Ultimately, clarity in the initial problem statement is emphasized to avoid confusion in such discussions.
Ryan Bruch
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Supposed there is a tree on a perfectly flat plane. If an observer in front of that tree moves further and further away from the tree, the tree would look smaller and smaller. When the observer moves further and further away, would the lower part of the tree's trunk seem to disappear as if sinking below the horizon?
 
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No. Why would it?
 
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A person claimed that it does and that he had observed it before, on Earth though. These are his illustrations:

fig74.jpg


fig76.jpg


fig78.jpg


fig79.jpg


fig80.jpg
 
Earth is curved, an oblate spheroid.
 
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In more words, what Doug is telling you is that YOU were the one that specified a condition of a perfectly flat surface, thus, there is no such thing as a horizon. So, what is it? a flat surface or an sphere...please state your problem correctly and fully form the beginning.
 
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In Nathaniel Bowditch's American Practical Navigator is listed a most useful thumb-rule for estimating the distance to the horizon for practical heights of eye.
 
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