Shadow
A shadow is a dark area on a bright surface. It is caused by something that is blocking a source of light. A shadow's outline, called a silhouette, will have the same shape as the object blocking the light. Shadows can't form when it's dark.
Depending on the light source, or sources, a wide range of effects can be produced. A point source of light casts only a simple shadow, called an "umbra". A "penumbra" is the region in which only a portion of the light source may be blocked. If there is more than one light source, there will be several shadows, with the overlapping parts darker, and various combinations of brightness or even colours. The more diffuse the lighting is, the softer and more indistinct the shadow outlines become, until they disappear. The lighting of an overcast sky produces few visible shadows.
Astronomical shadows are usually sharp. This is because in space the light usually does not go through an atmosphere.
The sun is the biggest and main light source in our solar system.
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Shadow Media
The shadow of a musician cast onto a brick wall
Park fence shadow is distorted by an uneven snow surface.
Shadows from cumulus clouds thick enough to block sunlight
Steam phase eruption of Castle Geyser in Yellowstone National Park casts a shadow on its own steam. Crepuscular rays are also visible.
Fog shadow of the south tower of the Golden Gate Bridge
Moonlight shadow of a photographer
Non-diffuse lighting in outer space causes deep shadows
British Library Gate
