Sign into an existing account

The size of a shadow depends on the size and distance of the object casting the shadow. The further the distance between the object and the shadow surface, the larger the shadow.

In three-dimensional space, a sphere has a point that is closest to the object casting the shadow. From that center point there is a gradient of distance outward to the edge of the sphere from the relative position of the object casting the shadow.

This will cause a shadow to gradually expand over a sphere. If the shadow itself is crescent, then the crescent shape will appear as a straight line do to the shadow stretching out as it travels a further distance on the sphere.

Anyone can do an experiment that will show these results. A flashlight and two balls. Use the flashlight to cast a shadow of one ball onto the other ball, covering half of it's surface. Is the ball split with a crescent or a straight line?