Hmmm, seems a little extreme, having to kill everyone to rediscover the roots of a belief ... still, maybe the Renaissance might have been better killing every faith leader, so that the subsequent ones might learn anew what their faiths stood for, rather than just having the tame Germanic Reformation and Spanish Counter Reformation ... "
Sure it does, if there is some medium for the radiated waves to travel through. Granted, if the water falls in a vacuum, then it's silent (though electromagnetic radiation certainly needs no medium), but in an atmosphere, well, the sound certainly travels, even if there's no-one there to hear it ...