Van Gogh painted this night scene without a single stroke of black, and that choice is exactly why a 6-year-old watched the night get darker in real time.
Café Terrace at Night builds its darkness entirely from blues and violets. Van Gogh wrote to his sister that he wanted to paint night using no black at all. So every ounce of darkness you see comes from how light bounces off colored paint, which means the darkness depends on where you stand.
Here's the mechanism. Van Gogh laid paint on in thick ridges, sometimes millimeters tall. Each brushstroke is a tiny 3D structure with a lit face and a shadowed face. Museum lights hang above the canvas. At adult height, straight on, light scatters off the top facets of those ridges into your eyes. The yellows glow. The sky stays luminous.
Drop to a child's eye level and look up, and the geometry flips. You now face the underside of every ridge, the surfaces the overhead light never touches. Thousands of micro-shadows tilt toward you at once. Blues deepen, the café's yellow halo shrinks, and the painted sky reads hours later.
Oil adds a second effect. The surface is partly glossy, so reflections shift with viewing angle. A printed poster of this scene looks the same from every direction. The original behaves like a relief sculpture wearing an image.
The kid said "the night I saw was much later." He was describing impasto self-shadowing, the exact phenomenon optics researchers measure with goniophotometers. He found it by being three feet tall.