The story of the greatest known explosion in the history of the world: on the morning of June 30, 1908, near the Stony Tunguska River in Central Siberia. A blinding ""pillar of fire"" visible 125 miles away, shock waves that went around the world twice, radiant burning and toppling of trees, a huge ""cloud of black smoke,"" and three days of ""black rain""--for years Soviet scientists were intrigued by what was assumed to be a highly peculiar meteor, so peculiar that the meteor itself was never found. Then came Hiroshima and Nagasaki, and the atomic nature of the explosion became apparent--later to be substantiated by evidence of radiation and genetic changes in the vegetation around the blast area, as well as the presence of extraterrestrial matter. But what kind of atomic blast? The authors convincingly disprove the ""anti-matter"" and ""black hole"" theories to arrive at the intriguing, currently prevailing, thesis: a spaceship, traveling slowly enough to be simultaneously visible and audible, overheated within earth's atmosphere until its fuel core melted and a nuclear explosion was triggered. An engrossing true-life intergalactic detective story.