My friend was explaining to me once how the only faster then light is shadow. It was very odd. He said that if we have a star being orbited by a planet with a period of one days and surronding this system is a "wall", upon which to cast a shadow, 1 light year away. So, if the planet circles the sun in a year, then so must its shadow. So if the radius of the circle is 1lty, the the circumference is Pi lty! Meaning the shadow is going ~3.1415x faster then the speed of light? This doesn"t seem to make sense to me... In the same way a person running around a light bulb in a circular room will have a shadow going faster the them. To the same degree a moon orbiting a planet in a circular "room" which has light emitting walls will have a shadow going slower then it, because it will cover less distance in the same time. This seems illogical to me! There must be some kind of contradiction... obviously the time it takes for the light to reach the wall will make the shadow lag behind the planet to an observer infinite metres away, who can somehow see this... but that won't make the shadow any slower... I'm trumped. Anyone have anything to add?