Because the Sun—and, to a lesser extent, the Moon, stars, fire, and artificial lighting—has the property of casting shadows, landscape design, in placing trees, structures, and other elements on the land, must always take into consideration the light and shade resulting from such placement. Light and shade are not the same in all parts of a country or the world. Light is welcome in cool, gray, northern climates, shade in hot, bright, desert or tropical regions. In the clear air of unspoiled deserts, one can see so far that all sense of size, scale, and distance is lost; in the foggy humidity of the western coasts of Europe and North America, distances seen and objects perceived change from day to day, sometimes from hour to hour, so that one lives with a continuing sense of mystery and variety. Landscape design must, ideally, remain sensitive to and work carefully with the light and shade relations that are most desirable in each different region or subregion.