Tree Trunk Illusion: Does it Disappear Over the Horizon?

[Ryan Bruch]

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?

 

[Doug Huffman]

No. Why would it?

 

[Ryan Bruch]

A person claimed that it does and that he had observed it before, on Earth though. These are his illustrations:

 

[Doug Huffman]

Earth is curved, an oblate spheroid.

 

[gsal]

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.

 

[Doug Huffman]

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.