Spanno

Meet Spanno, a crate who looks smaller the farther away he is.

How big something looks depends on both its real size and its distance. Its angular size is the angle it covers in your view. For small angles, the angular size in radians is the real size divided by the distance, θ ≈ D/d.

A person 1.8 m tall standing 100 m away covers θ ≈ 1.8 / 100 = 0.018 rad, about 1.0°. Move the same person to 200 m and θ ≈ 1.8 / 200 = 0.009 rad, about 0.52°. Doubling the distance halves the angular size.

This is why two identical objects at different distances look different in size, and why artists draw distant things smaller to show depth.

The shortcut θ ≈ D/d only works for small angles. For something very close and wide, the exact relation θ = 2 arctan(D/2d) is needed. At these small angles the shortcut is very accurate: for the person 100 m away, the exact formula also gives 0.018 rad.