A shadow is an area where direct light from a light source cannot reach due to obstruction by an object. It occupies all of the space behind an opaque object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the light. The sun causes many objects to have shadows and at certain times of the day, when the sun is at certain heights, the lengths of shadows change.
An astronomical object casts human-visible shadows when its apparent magnitude is equal or lower than −4. Currently the only astronomical objects able to produce visible shadows on Earth are the sun, the moon and, in the right conditions, the planet Venus.
Read more about Shadow: Variation With Time, Non-point Source, Shadow Propagation Speed, Color of Shadow On Earth, In Photography, Fog Shadows, Other Notes, Mythological Connotations, Heraldry
Famous quotes containing the word shadow:
“I have often told you that I am that little fish who swims about under a shark and, I believe, lives indelicately on its offal. Anyway, that is the way I am. Life moves over me in a vast black shadow and I swallow whatever it drops with relish, having learned in a very hard school that one cannot be both a parasite and enjoy self-nourishment without moving in worlds too fantastic for even my disordered imagination to people with meaning.”
—Zelda Fitzgerald (1900–1948)
“It is the same for all men. None of us can escape this shadow of the father, even if that shadow fills us with fear, even if it has no name or face. To be worthy of that man, to prove something to that man, to exorcise the memory of that man from every corner of our life—however it affects us, the shadow of that man cannot be denied.”
—Kent Nerburn (20th century)
“At middle night great cats with silver claws,
Bodies of shadow and blind eyes like pearls,
Came up out of the hole, and red-eared hounds
With long white bodies came out of the air
Suddenly, and ran at them and harried them.”
—William Butler Yeats (1865–1939)