Ghostly geometeors

Andrei Ol'khovatov's geometeor hypothesis is definitely not voodoo science; however, some of his ideas seem ahead of their time. Ol'khovatov, formerly of the Soviet Radio Instrument Industry Research Institute and now an independent researcher based in Moscow, is a popular figure in the large Tunguska cyberspace community, as well as in the small but real community of Tunguska scientific researchers. His website and discussion forum keep the Tunguska debate alive and up to date.

Ol'khovatov became interested in the Tunguska event when in the late 1980s he read about earthquake lights, a glow that sometimes occurs before a large earthquake. He immediately associated these lights with the Tunguska eyewitness accounts. The similarity between accounts of earthquake lights and those of Tunguska led him to believe that there might be some link between the two. He first published his hypothesis in the journal of the Izvestia Academy of Science of the USSR in 1991, but an updated English version appears on his website and in the proceedings of many scientific conferences attended by him. Like all those who reject a cosmic impact, he wants to know where the remnants are. 'Nowhere', he says, 'nothing after decades of detailed research'.

He believes that the explosion was caused by a strong coupling between some unknown subterranean and atmospheric processes. This coupling formed meteorlike luminous objects but of terrestrial origin. For want of a better word he calls these objects 'geophysical meteors' or 'geometeors'. A geometeor resembles a highspeed ball lightning. 'Similar events occur in association with earthquakes (earthquake lights) and in association with a thunderstorm (ball lightning)', he says.

According to Ol'khovatov, the Tunguska region is right in the middle of an ancient volcanic crater. There are many other prominent geological faults, circular structures and other geological formations in the region. Several tectonic faults intersect near the Tunguska explosion centre. There is evidence of increased seismic activity in the region before the explosion. Simultaneously, there was also an increase in anomalous meteorological phenomena: increased sunspot activity; strong increase in thunderstorms; the change in Tunguska region meteorological stations' forecast for 30 June 1908 from 'good weather' to 'bad weather' because of the possibility of a cyclone; and a strong upsurge in atmospheric pressure soon before the event.

This rare combination of large-scale geophysical and meteorological disturbances manifested itself as follows. First, there was luminous activity in the atmosphere in southern Siberia, which was like falling meteors. At about the same time, a swarm of shallow earthquakes started, which were accompanied by brontides (thunderlike sounds of short duration believed to be of seismic origin). Then, at the vent of the crater, there was a large geometeor explosion.

Ol'khovatov believes science is not yet ready to explain the exact mechanism of geophysical and meteorological interactions. However, in his paper he describes in detail how a geometeor can explain various eyewitness accounts and the natural phenomena associated with the event. Ol'khovatov quotes Russian researchers who in 1988 analysed eyewitness accounts of the Tunguska object and found the following descriptions for the shape of the object:

The shape of the Percentage of

Tunguska object eyewitness was like a ... accounts ball

12.1

cylinder cone star tail snake lightning strip of light pillar of fire flame sparks other shapes

He points out that these descriptions hardly conform to a meteorite fall. He also explains the 'three trajectories of the Tunguska meteorite fall' drawn up by researchers from eyewitness accounts by saying that all three trajectories are above the main tectonic faults and they intersect at a point near Vanavara. Does it mean that witnesses saw more than one luminous phenomenon or geometeor? Ol'khovatov says: 'I'm inclined to think that there were several low-altitude fireballs, and that's why there are no reports of two or more fireballs seen simultaneously. The low altitude of fireballs explains why nobody in Vanavara saw a fireball or its trail. Besides the fireballs, evidently there were other typical earthquake lights.'

The three trajectories, according to Ol'khovatov, vary from south-southeast to east-northeast, that is, by up to 90 degrees. These trajectories were drawn from the accounts of eyewitnesses who were 500 kilometres away from the epicentre. 'If it were a meteorite most of the witnesses from the west of the trajectory would say that it flew from the east, while most of the witnesses from the east of the trajectory would say that it flew from the west', he says. 'There would be some witnesses who would say it flew overhead. So, we should have a well-defined trajectory. But there was no such situation in Tunguska. The advocates of the asteroid/meteorite impact choose just a small part of the eyewitness accounts and then announce other eyewitness accounts as "unreliable". As there are several trajectories, so each trajectory has its "reliable witnesses" (a minority), and its "unreliable witnesses" (a majority). A witness for one trajectory could be "reliable" and "unreliable" for all other trajectories.'

At a qualitative level, says Ol'khovatov, his geometeor hypothesis can explain all known facts about the phenomenon. For example, a few years ago several articles appeared in scientific journals stating that about a day or less before an earthquake, the cloudiness level sharply decreases above tectonic faults in the area that will become the epicentre of the earthquake. 'So I studied data from nine meteorological stations within 1,000 kilometres of the Tunguska epicentre (the closest is 500 kilometres away)', Ol'khovatov says. 'I averaged the data from all stations. And indeed, the average daily cloudiness level shows an extremely deep drop on 29 June 1908!'

Ol'khovatov estimates the diameter of the largest ball to be about 1 kilometre. 'But it is just a guess', he adds. He also stresses that the luminosity of the fireball reported was rather weak, while according to the meteorite theories it must be as bright as the Sun, and much brighter near the epicentre - with no persistent trail. He has not estimated the energy of the fireballs: 'The question is still open: Is energy deposited by a lightning ball inside it, or does it also include energy around it? In ball lightning, what we actually see is a tip of the iceberg. I believe science is not yet ready to give a final answer to this question.'

We shall wait. But for many other explanations for the Tunguska mystery we do not have to wait. Science is ready right now to judge them. Whenever the word 'mysterious' is attached to a natural scientific phenomenon that lacks a beyond-a-reasonable-doubt explanation, it becomes a fertile ground for the imagination of those who love outlandish ideas. There is no shortage of eccentric theories for the explanation of the Tunguska event. Let's open the X-files.

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