The Tunguska incident, June 30, 1908: a blast, a meteorite, a comet, or a threat from space

Almost 115 years ago, the very powerful explosion occurred at 7:17 AM in the morning of June 30, 1908 in Central Siberia, 800 km NNW from Lake Baikal and Irkutsk near Podkamennaya Tunguska River. It devastated the forested area of 2150 km2, flattening and scorching some thirty million trees. The object that flew that morning over Siberia is usually designated the Tunguska meteorite or – more cautiously – the Tunguska space body. Certainly, this body was dangerous: the taiga was levelled over an area twice as large as New York City. The whole number of explosion hypotheses reaches a hundred, or so. But few of them have been built according to the standards of science and with consideration of empirical data. The scientific interest stimulated by the Tunguska explosion of 1908 has produced enormous speculation and controversy as to its origin. The theories offered by those who have studied the event range from the realm of science (a meteorite, comet, or nuclear explosion) to the realm of science fiction (a black hole, anti-matter rock, or an alien spacecraft). Each theory has protagonists promoting and defending their point of view considering the evidence. However, because the scientific community did not view the actual event, but only observed the devastating results (it was 19 years after the explosion before the first scientist arrived on the scene), each theory contains speculation. Therefore, before delving into the specifics of each theory, it is important to review the facts of the event.