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It is known that a shadow can travel faster than the speed of light and break no known laws of physics, because it is not an actual thing. A shadow is just the blockage of light. However in the following statement "Maximum speed is finite: No physical object, message or field line can travel faster than the speed of light in a vacuum.", my questions concerns the message portion of this statement. Why can't a shadow be a message? Batman gets his messages from shadows i.e. the bat signal, all the time. I'm not a scientist, obviously, so I know there is something I am missing here?