Perspective

As objects become more distant they appear smaller because their visual angle decreases. The visual angle of an object is the angle subtended at the eye by a triangle with the object at its base. The greater the distance of the object from the eye, the greater is the height of this triangle, and the less the visual angle. This follows simply from Euclidean geometry.

For example the Sun and the Moon appear to be roughly the same size because the Sun, although much larger, is also much farther away. The relationship between distance and apparent height of objects is an inverse-linear function: h={1\over d}*a
where h is the apparent height, d is the distance of the object, and a is the actual size of the object.

In a Father Ted episode , Father Dougal is bemused by the size of cows. Which brings me to my point. I have a large car and in this shot it looks small.