Shadow
A shadow is a region of
darkness where
light is blocked. A shadow occupies all 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.
Encyclopedia
A
shadow is a region of
darkness where
light is blocked. A shadow occupies all 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.
Features
The closer to 90 degrees the angle between an elongated object and the direction of the light it blocks, the bigger its shadow. The smaller the angle between the direction of the light and the surface on which the shadow occurs, the longer the shadow is. If the object is close to the light source, the shadow is large. If the surface is curved there are further distortions.
For a non-point source of light, the shadow is divided into the
umbra and
penumbra. The wider the light source, the more blurred the shadow.
If there are multiple light sources there are multiple shadows, with overlapping parts darker, or a combination of colors. For a person or object touching the surface, like a person standing on the ground, or a pole in the ground, these converge at the point of touch.
Colored shadows
If white light is produced by separate colored light sources, the shadows are colored.
Illuminate a room with a red light, and the shadows are exclusively gray, or dark. Illuminate the shadows with a white light, and the shadows are green. Where both lights are blocked, or in other words where the shadows intersect, the shadows are gray. Away from the intersection, where the red light is blocked the shadows are green, and where the white light is blocked the shadows are red. In other words, light colors shadows or brightens them, according to the complementary color of the light blocked to cast the shadow. In the case of white and red lights, the complement of white is red; with white and green lights, the complement of white is green.
In the absence of multiple light sources, colored lights illuminate spaces where other lights are not blocked. In the above example, the red shadow cast by blocking white light is not a shadow with the white light off, but it is illuminated in red.
In the absence of white light, colored lights blocked by an opaque surface cast shadows in the colors complementary to the lights blocked. For green light, red shadows, and vice-versa; blue, orange; yellow, purple; intermediate light, intermediate shadows.
Faster than light
For objects moving at every-day speeds , the shadow cast by an object will move faster than the object which casts it. A cross-section of a shadow is displaced by the motion of an object in front of a point source of light. The further the distance from the object blocking the light, the larger the silhouette and the greater the displacement by motion.
However, this simple relationship between speeds and distances becomes more complicated over vast distances for very fast moving objects due to the finite speed of light; the motion of an object may cut off the emission of light from a source to a surface, but the light that had already passed by the object will take some time before reaching the surface, and so there is some delay before the shadow on the surface reflects the updated position of the object. Thus while it is certainly possible to create shadows that move faster than light, this effect cannot be used to transmit information at superluminal speeds, because the motion of the shadow is being caused by the motion of the object in the
past, not the present.
Other notes
A shadow cast by the
Earth on the
Moon is a lunar
eclipse. Conversely, a shadow cast by the Moon on the Earth is a solar eclipse.
On satellite imagery and
aerial photographs, taken vertically, tall buildings can be recognized as such by their long shadows , while these also show more of the shape of these buildings.
A shadow shows, apart from distortion, the same image as the silhouette when looking at the object from the sun-side, hence the mirror image of the silhouette seen from the other side .
The term
shadow is also used with regard to other things than light, for example
rain: a
rain shadow is a dry area, which, with respect to the prevailing
wind direction, is beyond a
mountain range; it is dry because air masses lose part of their
water when they move over these mountains.
Furthermore, it is possible to see shadows by moonlight on clear evenings.
Fiction
- In Peter Pan the main character loses his shadow: it snaps off when he leaps out of the window, which is slammed closed behind him. It is put in a drawer and later sewed back on by Wendy.
- In many fantasy games, shadow is widely referred to as the source of dark arts and black magic. Shadows, mainly in this genre, are said to be the departed souls of people that have had their lives tragically cut short or did not receive acceptance in heaven or hell.
- In the Chronicles of Amber series of novels , Shadow is a metaphysical substance in which all possible universes can exist, if a person who meets certain criteria desires to go to them.
- In Final Fantasy VI, Shadow is the name of a mysterious assassin who joins up with the protagonists at various locations and times during the game. Little is known about the character within the main course of the game, however much of his story-line is revealed when and if certain circumstances are met.
- In ninja fiction, ninjas are supposedly able to become "one with the shadows" or, "a living shadow." In the manga Naruto, a special shuriken is named "The Windmill of Shadows." Also in Naruto, Shikamaru Nara possesses the technique to control a person's body movements once his shadow touches theirs. He can also manipulate his shadow into several shapes. This is known as Kagemane no Jutsu . Also, in the game Samurai Warriors, Hanzo Hattori Can reach a level named the shadow.
- In Slayers and an episode of InuYasha, throwing a knife onto the ground in a person's shadow would paralyze them, aptly named "Shadow Bind".
- In Kingdom Hearts the basic and most common heartless enemy are called Shadows.
- In Dungeons & Dragons, there is a class named "Shadowdancer" that supposedly draws on shadow powers to induce abnormal effects in combat.
- In many cartoons that are very loosely based in reality or comedy movies with roughly equal disregard for reality , it is possible for shadows to act completely independently of the person who is supposed to be casting them. This often ranges from a person's shadow fighting with them , or going the wrong way to shadow puppets running amok . It is also possible for people to make photorealistic shadow puppets in these mediums.
- In the Bionicle universe, Makuta is master of shadows. He use a Kanohi mask called Kraahkan, to allows he the shadows powers. Others beings control Shadows in Bionicle, like Roodaka and the Dark Hunter Kraata-Kal.
- In The Seventh Tower book series, creatures from a spirit-world are bound to people and become free-willed shadows.
- In , Shadow is a creature ability that results in the creature only being able to participate in combat with other creatures that also have Shadow.
- In , the Lasombra are a species of vampire that can manipulate shadows and darkness in general.
- in tales of symphonia and the rest of the tales series, shadow is the summon spirit of darkness
- in Legend of Zelda, Shadow Link is a recurring enemy the real Link must overcome.
Heraldry
In
heraldry, when a charge is supposedly shown in shadow , it is called
umbrated. Supposedly only a limited number of specific charges can be so depicted.
See also
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