Imagine when thunder was the most mysterious, impressive, ear-splitting sound humankind knew? It is hard for us to imagine a world in which there is as much silence or quietness as there was in ancient times. It is hard for me to imagine how ancient peoples understood thunder. I’ve always grown up being taught to link thunder with lightning, but how early was it when that link became assumed? Lightning is sometimes too far away for its thunder to be heard, and oftentimes I miss the sight of distant lightning even when I hear its thunder. How would and ancient mind, without knowledge of speeds of light and sound, process their observations?
Thunder alone is not the only thing mysterious to the ancient mind, and Surah al-Ra’d (43 ayat) is going to point to many other at-that-time mysterious things and see the presence of God in them. In material this comes closer to the materials of some of the Psalms (I’m thinking particularly Psalm 19). Argument and didactic intent are still very clear in the ayat, but the surah does approach a more purely worshipful tone as it marvels at the world to find God.