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:
“We saw one schoolhouse in our walk, and listened to the sounds which issued from it; but it appeared like a place where the process, not of enlightening, but of obfuscating the mind was going on, and the pupils received only so much light as could penetrate the shadow of the Catholic Church.”
—Henry David Thoreau (1817–1862)
“Suddenly I’m not half the girl
I used to be.
There’s a shadow hanging over me . . .
From me to you out of my electric devil....”
—Anne Sexton (1928–1974)
“Yet there is a mystery here and it is not one that I understand: without the sting of otherness, of—even—the vicious, without the terrible energies of the underside of health, sanity, sense, then nothing works or can work. I tell you that goodness-what we in our ordinary daylight selves call goodness: the ordinary, the decent—these are nothing without the hidden powers that pour forth continually from their shadow sides. Their hidden aspects contained and tempered.”
—Doris Lessing (b. 1919)