I’ve been wondering this for a while. Why do things farther away appear smaller?
-Th’ JawaTrader
Hmmm, I’m not really sure I’m up to this but I’ll take a whack at it.
First, they don’t appear smaller unless you’re having some problems processing information. If I’m standing on the beach and an oil tanker comes down the ship channel and heads out to sea it gradually occupies less and less of my arc of vision as it approaches the horizon. But when it gets a ways out there, near the horizon, I don’t for one minute think that its gotten smaller, and maybe I could now fit it into my pocket.
As the ship recedes into the distance its image is focussed on proportionally smaller and smaller amounts of my retinas relative to the other objects in the scene. I’m having a mildly psychedelic moment trying to imagine visual perception without perspective.
You have a field of vision that takes in (what?) about 140-150 degrees (rough measurement made with outstretched arms). All the light that is reflected from objects that fall within that range reaches your retina (ignoring the blind spot for a moment) and you process that info and construct an image in your head. When your standing on the dock beside the ship looking at it, its hull occupies your entire field of vision. As it moves away, other objects begin to occupy parts of your field of vision and the ship’s proportional representation falls from 100% to less and then still less.
But you don’t for a minute think it’s shrinking.
Do you?
I don’t think I hit this one out of the park, but perhaps a starting point, TM?
I didn’t really bother w/binocular vision and depth perception because it didn’t really seem to apply.
Regards
Because the way you see things (esp distant things) is as if you are a point, and objects you see take up a certain angle in your vision.
Right now I’m looking out my window. The window is about 5 feet away from me. I would guess that the window takes up about 40 degrees in my field of view. Anything that also takes up that 40 degrees is going to appear to be the same size (because it *is[/is] the same size on my retina). In this case, that 40 degrees includes a whole house that it a few hundred feet away.
Try looking around at things and imagining angles between one side of an object and the other side of that object that come together at your eye. Then try to picture that angle going past the object and think about how much more space it takes up on the other side. That is the space that is blocked from your vision by the object, so naturally anything that can fit in that space behind will appear smaller.
And beatle makes the important point that yes, your brain is very effective at making you understand the difference between a small object and an object that is far away. So while we can be analytical and say that two objects appear to be the same size, on a gut, instinctual level, we generally know which is bigger.
Some of the methods your brain uses to tell you this:
overlap – an object that is partially obscured by another object must be farther away
parallax – when you are moving, close objects seem to move more quickly in your field of vision than do more distant objects
familiarity – if you are familiar with cars, you have some expectation of the size of a car
binocular vision – your two eyes have a slightly different view point which allows them to “triangulate” that distance to objects. This helps for very fine discrimination of distance at fairly close range, but isn’t necessary to get a basic idea
LOL! I was thinkin the same thing. If I said “doll house city” would it mean anything to you, beatle? 
oh, COME ON folks! You are all making this WAYYYY too complicated. See…it’s like this: If everything stayed the same size as it receeded from view, then the world would be overrun with HUGE things, and there would be no room left for us, and we would wind up living underground, like characters in a Robert Heinlein novel.
Therefore, things shrink as they go away, to make room for NEW and COOL things that only get bigger, and COOLER as they approach. Like Brittney Spears, or Gwynneth Paltrow <<sigh>>, or the 1980 Phillies.
I hope this has cleared things up. Please, let’s have no more of this unpleasantness, shall we? Here, have some banana bread 
Typer
" If you wanna kiss the sky, you’d better learn how to kneel "
If you wanna kiss the sky, you’d better learn how to kneel.
I think beatle did a great job, but if you want another take – one you can “wonder” for another while – try this:
If you look out there where things appear small, you’ll have to admit there’s a way lotta territory out there. In many cases you will see one heckova lotta things out there at that distance. Now, what if they all appeared as big as they do when they’re up close? That might be a bit disconcerting, confusing. . .and downright dangerous – like living in the middle of a heard of buffalo. Actually, you can approach this state of affairs by looking through a telephoto lens, where there is less perspective.
‘Why’ can ask for either of two types of answer: 1. What causes what is asked about, and 2. What is the reason for it. Since your question is really about your subjective impression, I think the latter is maybe more directly relevant.
When you drive on urban freeways, you have to read too many signs as it is. People definitely should not be born with telephoto lenses in their eyes. Photogs like to take pix of commericial sprawls with telephoto lenses, e.g.:
http://www.scenicflorida.org/slides/a30.jpg
http://www.scenicflorida.org/slides/a28.jpg
http://www.scenicflorida.org/slides/a23.jpg
http://www.scenicflorida.org/slides/a21.jpg
Clearly, much of our society should be taken in a great deal of perspective.
Ray (lost on the horizon)
UDD:
'fraid not. Interesting tale?
Well, not so much a specific story. Let’s just say that the idea of visual perception without perspective inducing a psychedelic moment is a somewhat reversible statement.
click click
On the topic of doll houses, why is it that closeups of scale models in films never look real? In some indefinable way, it looks like a closeup, not a picture of the real full-size thing. Does this have something to do with the focal length of the camera lens, or some such?
I think it’s often that the texture and behavior on materials appears wrong for the purported scale. The grain of the wood is not right, or the curtains don’t really hang right. I’ve noticed in movies where they’ve used really well done ship models, you still notice that the apparent viscosity of the water just doesn’t fit the scale you’re supposed to believe.