My Goal in Life
SHADOW
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 spacebehind 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.[1] 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.
[edit]Variation with time
Shadow length when caused by the sun changes dramatically throughout the day. The length of a shadow cast on the ground is proportional to the cotangent of the sun's elevation angle.
Shadow propagation speed
The farther the distance from the object blocking the light to the surface of projection, the larger the silhouette (they are considered proportional). Also, if the object is moving, the shadow cast by the object will project an image with dimensions (length) expanding proportionally faster than the object's own rate of movement. The increase of size and movement is also true if the distance between the object of interference and the light source are closer. This, however, does not mean the shadow may move faster than light, even when projected at vast distances, such as light years. The loss of light, which projects the shadow, will move towards the surface of projection at light speed.
The misconception is that the edge of a shadow "moves" along a wall, when in actuality the increase of a shadow's length is part of a new projection, which will propagate at the speed of light from the object of interference.
Since there is no actual communication between points in a shadow (except for reflection or interference of light,
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 spacebehind 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.[1] 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.
[edit]Variation with time
Shadow length when caused by the sun changes dramatically throughout the day. The length of a shadow cast on the ground is proportional to the cotangent of the sun's elevation angle.
Shadow propagation speed
The farther the distance from the object blocking the light to the surface of projection, the larger the silhouette (they are considered proportional). Also, if the object is moving, the shadow cast by the object will project an image with dimensions (length) expanding proportionally faster than the object's own rate of movement. The increase of size and movement is also true if the distance between the object of interference and the light source are closer. This, however, does not mean the shadow may move faster than light, even when projected at vast distances, such as light years. The loss of light, which projects the shadow, will move towards the surface of projection at light speed.
The misconception is that the edge of a shadow "moves" along a wall, when in actuality the increase of a shadow's length is part of a new projection, which will propagate at the speed of light from the object of interference.
Since there is no actual communication between points in a shadow (except for reflection or interference of light,