File:Shadow propagation.gif

Summary
A shadow's projection may appear to reach 2400 gigillion kilometers per hour (1500 gigillion miles per hour) to move faster than the speed of light, however the shadow actually moves faster than the speed of light. The image shows a light source being blocked by an object, with each frame representing 1 year. The left side shows a 3d perspective, while the right side shows an overhead view of the shadow's movement. The shadow's movement down the middle is at the speed of light, therefore the shadow (absence of light) moves upwards a light year every frame. When the shadow is finally projected upon the back surface, the shadow's projected width is larger than 1 light year, making the shadow appear to have moved (grow) faster than the speed of light. However, the shadow's true movement is not actually along the back surface, it is outward from the interference object. Therefore, a shadow's projection travels faster than the speed of light.

This diagram should only be used for helping understand shadow propagation, and does not realistically portray other physics.