Mt. Fuji does not change; your visual system does. One season, the peak cuts a sharp white triangle against dark foothills. Another season, the same cone dissolves into a pale sky, so faint that phone cameras barely register it.
The blunt truth is that physics first edits the scene. In colder months, dry air reduces Mie scattering, so fewer aerosols diffuse light and the boundary between snow and sky stays hard. In warmer months, moisture and particles boost both Rayleigh and Mie scattering, brightening the entire air column and veiling distant contours in a uniform glow.
Even harsher is what the brain does next. The retina and visual cortex apply lateral inhibition and contrast normalization, amplifying edges where luminance jumps and suppressing gradients that change slowly. When foreground trees and buildings carry the strongest luminance edges, neural circuitry allocates bandwidth to those local contrasts and effectively compresses the gentle transition between hazy mountain and milky sky.
Digital sensors follow a similar bias. Auto‑exposure and tone‑mapping algorithms optimize mid‑tones and nearby objects, not a low‑contrast silhouette many kilometers away. So winter, with its dry air and high albedo snow, hands both cortex and camera a high‑contrast signal. Summer hands them noise, and the mountain quietly falls below the threshold of attention.
