I think it is less 'symbolic' than you might think. Re-read Revelations... Christ doesn't come untill the begining of the seventh thousand years after much tribulation. We may very well be in the seventh seal now. By the way, just what does the half hour of silence mean? Half hour (21 years) of calm before the "stuff" hits the fan??? If that's the case we've used up half of our 'calm' time!