Why was there silence in heaven?

Revelation 8:1 tells of the opening of the 7th seal and there was silence in heaven for 1/2 hour. This half hour could be bible time which would equate to 1 week here on earth. The opening of the 7th seal is a last chance for all humans to make their decision, rebuke Satan, or embrace the Lord. The half hour may mean that all in heaven were 'holding their breath' waiting to see who could be saved. Up to that point humans have the choice.