Gmontag is right. Anybody wanting to read more about the subject I would recommend this book.
http://www.amazon.com/exec/obidos/tg...glance&s=books
It's really good at explaining the concepts behind relativity and then goes on to look at relativity itself and scenarios like you mentioned.
Also light is self propogating because a moving electric field creates a magnetic field and a moving magnetic field creates an electric field.