Caitlin from Colmesneil, TxI think this song could be interpretted as being about man's destruction of the enviroment. "The Silent Planet" could refer to earth, in much the same way as in the book "Silent Spring", the earth will be silent when we poison it and kill off all the life, and that's exactly what we're headed towards.
Fay from Seattle, WaOut of the Silent Planet is the name of a science fiction book by C.S. Lewis. The silent planet refers to Earth, which has isolated itself from God and the rest of the universe, making it a desolate place.