Another run-through on the greatest explosion in human history--the fireball that struck Tunguska, an isolated Siberian forest region, at midnight June 30, 1908. Nobody knows what caused the explosion, which lighted up faraway London so brightly at midnight that fine print could be read without artificial aids. The mysteries only deepen the more you read. Devastated trees fall away concentrically (a long oval) from ground zero--but there's no crater! So how could it be a meteor? It was apparently an aerial explosion of some atomic nature, since the flash effects, genetic plant mutations, and fantastic abundance of subsequent vegetation were similar to the Hiroshima blast's effects. Stoneley suggests some far-out hypotheses to see how they hold up: a pinpoint-sized black hole that struck Tunguska, passed through the earth, and came out through the Atlantic trench; ball lightning larger than any known; a tennis ball of antimatter (ahh!); some kind of nuclear reactor on an exploration vehicle from. . . or a ""Brain"" that died after sending signals to--oh, say, Alpha Centaurus; an alien space ship that ruptured; and so on. He also pads shamelessly by rehearsing the horrors of Krakatoa, Vesuvius, and similar vast calamities and he includes the possible incineration of London or New York by meteor. Thin fact thickly marbled with fantasy.