This time the trumpet blast announced judgment on a third of the heavenly bodies. Darkness is a common symbol of judgment in the Old Testament, and the day of the Lord was to be a time of darkness (Amos 5:18; cf. Isa. 13:10; Joel 2:2; Mark 13:24). The darkening of the heavenly bodies predicted in this verse also serves to warn of more judgment to come. Evidently God will cut off light from the sun, moon, and stars from the earth by one-third (cf. Exod. 10:21-23). The text seems to imply that God will reduce the intensity of light from these sources by one-third (cf. Matt. 27:45). Perhaps a partial eclipse or pollution in the atmosphere is in view. Such a reduction in light, and consequently temperature, would have a devastating effect on the earth.
