The sky split open. The forest exploded. Millions of trees fell in a single instant. But when scientists finally reached the blast site, one thing was missing that shouldn't be. On the morning of 30 June 1908, a fireball lit the sky above the basin of the Podkamennaya Tunguska River in central Siberia. An eyewitness, quoted by the Royal Observatory Greenwich, described the moment: “the sky split in two and fire appeared high... [5654 chars]