The truth of the Tunguska incident

In 1908 in the forested wastes of Siberia in Russia there was an unusual event that is still raising questions today. A bright light was seen travelling across the sky at high speed, witnessed by several local herders and hunters and people in two local villages. Shortly after the light passed over the horizon there was a large flash followed by a tremendous sound of thunder. On following the path that the light had travelled the first people to reach the site discovered a large area of forest where trees had been blasted flat in a roughly butterfly shaped pattern. There was no clear evidence of burning and no obvious impact crater, although it should be noted that the area is highly swampy in nature and pock-marked with small pools and sink holes. It also has an underlying volcanically active geology. Within six months expeditions were carried out to the region from institutes in Moscow and St Petersberg but any reports from these expeditions have been lost through the Russian revolution and the first and second World Wars.

The first reported expedition was in 1921 by Leonid Kulike and even this late after the event the area was still widely devastated, with photographs still showing the trees blown flat. Analysis of the blast pattern, the damage to the trees, the impressions on the ground and the witness reports suggested that the event had been caused by a meteorite exploding in the atmosphere above the region. The only problem is that this leaves one or two questions unanswered, and doesn't entirely satisfy all of the researchers. The first key question is the size of the explosion. Based on reconstructions using both physical and computer models the blast has been estimated at 10-15 megatons of TNT or approximately 1,000 times more powerful than the bomb detonated over Hiroshima in 1945. In order to create such a blast the meteorite would have to be in the order of 100 tons in weight and approximately 10 metre cube in size. These are uncommon meteorite sizes and some have questioned whether a rock of this size could have detonated as an air burst. Then there is the question of a complete lack of debris of any sort. It has been suggested that even if a meteorite was completely vaporised in the atmosphere there would be some trace element precipitated to the ground. The composition of space based meteorites is distinct from terrestrial rocks in terms of isotopes and this should have been detected.

With little, if any physical evidence Tunguska is an interesting example of scientific analysis prematurely dismissing possible solutions to unusual phenomena. A computer model of this case demonstrated that a meteorite of the correct size at the correct angle would create the destruction pattern demonstrated. It was duly reported that the case had been solved, and the ead scientist appeared ona number of news shows and documentaries announcing this conclusion, right up until the point that a journalist asked the question “So, professor, if you are putting all the numbers into the computer, if you used different numbers could you get the same result another way?” To which the answer was of course, “Well yes, I guess you could”. Just because a computer model says it is so, that doesn't make it so. Worth remembering.