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, at the speed of light), a shadow that projects over a surface of large distances (light years) cannot give information between those distances with the shadow's edge.
Read more about this topic: Shadow
Famous quotes containing the words shadow and/or speed:
“A beautiful person among the Greeks, was thought to betray by this sign some secret favor of the immortal gods; and we can pardon pride, when a woman possesses such a figure that wherever she stands, or moves, or leaves a shadow on the wall, or sits for a portrait to the artist, she confers a favor on the world.”
—Ralph Waldo Emerson (1803–1882)
“No speed of wind or water rushing by
But you have speed far greater.”
—Robert Frost (1874–1963)