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:
“The vanishing volatile froth of the present which any shadow will alter, any thought blow away, any event annihilate, is every moment converted into the Adamantine Record of the past.”
—Ralph Waldo Emerson (1803–1882)
“Race prejudice is not only a shadow over the colored—it is a shadow over all of us, and the shadow is darkest over those who feel it least and allow its evil effects to go on.”
—Pearl S. Buck (1892–1973)
“Mark where the pressing wind shoots javelin-like
Its skeleton shadow on the broad-backed wave!
Here is a fitting spot to dig Love’s grave;”
—George Meredith (1828–1909)