THE FIRE CAME BY: The Riddle of the Great Siberian Explosion by John Baxter and Thomas Atkins (Doubleday & Co., N. Y., 1976 165 pp., 39 illus., $7.95) Reviewed by FREDERIC B. JUENEMAN director/research INCA Shortly after quarter past seven, on Tuesday, June 30, 1908, as the Earth turned its Asiatic face to the morning sun, a bolide streaked into our atmosphere. Seconds later it exploded over the Siberian taiga, near the headwaters of the Podkamennaya (stony) Tunguska river, in one of the most spectacular displays in modern history. The fiery "chariot," carving a thick dusty path in its wake, came in from the southeast at a low angle, and was viewed by passengers on the Trans-Siberian railroad as well as local inhabitants. The flash of the explosion was seen in Kirensk 400 kilometers away, and the shock wave was heavily felt in Vanavara 60 km from the blast area. (Impact was estimated at oh 17m 11S Universal Time.) Halfway around the world sensitive seismographs recorded an event, and barometric recorders took note of an atmospheric wave which passed twice around our planet, while unsophisticated electromagnetic devices sensed an unusual electric phenomena. Not until 19 years later did the world-at-large begin to know or piece together the bizarre events which occurred in the remote Siberian taiga. Headed by Leonid A. Kulik, of the Soviet Academy, a small expedition laboriously made its way to the site of the explosion in the Kimchu-Khushmo tributary basin (60° 55' N, 101° 57' E). And they found the tops of trees snapped off nearly 60 km from ground-zero, while as they approached the epicenter they saw fallen trees radially uprooted away from the blast area. Directly underneath, a stark, leafless forest greeted their eyes, as those trees still left standing told of a firestorm which man himself wouldn't create for almost another two decades. But no fragments of this bolide were ever found. Because the nights were so bright for nearly two months after the Tunguska fall that one could read a newspaper unaided at midnight, it was conjectured that a comet had collided with the Earth, and that its tail had preceded the nucleus in dissipating in our atmosphere. Since the coefficient of transparency of the atmosphere had measurably decreased after the fall, similar to the effects after the Rakata eruption on Krakatoa in 1883, it was estimated that several million tons of cosmic pollution had been dumped into our air-mass. Yet, as more expeditions converged on the Siberian wastes, where fearful Tungus tribes said, "The fire came by," fewer and fewer answers were forthcoming and more questions were generated. It became as a strange puzzle, enshrouded in mystery, and wrapped in an enigma. The comet hypothesis became less tenable on mechanistic grounds, which also ruled out a train of meteorites, as the path of the object, as described by observers in villages and communities along its course, delineated an erratic trajectory. Finally, in 1961 and 1963 two fully instrumented Soviet Academy expeditions found something else: background radioactivity was substantially higher than normal, there was evidence of heat-flash damage everywhere, and secondary radiation shadows were found 200 km from the epicenter of the blast -- virtually identical to those observed at Hiroshima. Apparently an unmistakeable thermonuclear explosion had taken place in 1908. When news of this broke on a bemused world, a rash of speculations attempted to explain the anomalous phenomenon. Usually conservative scientists searched into the more arcane frontiers of theoretical physics for evidence of antimatter, which annihilates energetically any normal matter with which it comes in contact. They discussed black holes, or collapsars, coming in contact with Earth, which can distort the very fabric of space, while inexorably pulling any nearby substance within itself, screaming its agony throughout the spectrum of radiation. Science fiction writers suggested that intelligent beings tried to communicate by laser, or that a nuclear mishap took place on a super-technology spacecraft. Baxter and Atkins, against a background of contemporary knowledge, trace the history of investigation of the Tunguska fireball, showing the 3000 square kilometers of leveled forest, the eyewitness descriptions of the searing heat-wave and series of explosions, followed by the rising, boiling cloud of incandescence, and the subsequent black rains. We are shown the line of reasoning by ballistics experts, who explain the radical difference between the expected shape of the devastated area from the supersonic path of the object as compared to the damaged taiga caused by the shock-wave of the detonation. We are gradually led, almost unsuspectingly, to the conclusion that the most incredible explanation for the Tunguska event is, through the weight of evidence, the most credible of all. At the end of this fascinating tour, in a final recounting of the fateful event, we are told: "A towering primordial fire, hotter than the interior of a star, splits the sky in two and sears the landscape below for more than 30 miles. "Then the great fire is gone, leaving behind only a massive column of black clouds that will remain for days in the atmosphere and a scarred, shattered taiga that will forever hide its secret." But for whatever secrets are hidden in the Siberian Steppes, we are not left free from conjecture, for in the penultimate conclusion we are asked momentarily to consider that we have been visited. But with a sobering measure of skepticism, one might equally consider that nature has shown us another phenomenom which has not begun to be characterised. Indeed, it appears that we have not begun to exhaust the storehouse of nature's phenomenal riches. Yet, we have to occasionally, almost compulsively, indulge ourselves in such speculations, for even as no man is an island unto himself mankind cannot be all alone in such a vast universe. _________________________________________________________________ \cdrom\pubs\journals\kronos\vol0202\104fire.htm