Re: Why do distant objects appear smaller to the observer than nearby ones?

The concept of being "small" or "big", for the human eye, is a matter of 
angular extension. And this angular extension is a very few degrees for a 
big tree far away from your eye and many degrees if the same tree is near 
you (almost ten times bigger if the distance of the tree is divided by 
ten).
The complete answer is also that our mind mades some kind of "automatic 
compensation" when we have some idea of the distance of the object and/or 
of it's height. In that case, we correct the natural answer of our eye to 
a better accuracy in determinig the reality of the dimension of the 
observed object