Thursday, June 29, 2006
The Tunguska Explosion, June 30, 1908
Today in 1908, an enormous explosion occurred near the Tunguska River in Siberia. Nearly a century has gone by without any conclusive proof being brought forward showing what caused the explosion, but most researchers agree that the blast had the equivalent energy of between 10 and 15 megatons of TNT.
Central Siberia was a remote, hard-to-reach wilderness in 1908, but even so, there were witnesses to the event. Near Lake Baikal, villagers saw a bluish light move across the sky at 7:15AM; they described it as being brighter than the sun. 10 minutes later, there was a bright flash and a sharp noise that sounded like artillery fire. When the shock wave arrived, it knocked people off their feet and broke windows. It was so strong that people felt it’s force hundreds of miles away. In England, barographs, used to measure atmospheric pressure, showed fluctuations from the explosion. That night, and for weeks thereafter, night skies in the northern hemisphere contained a strange glow so bright it allowed people to read outside.
The remoteness of the Tunguska area and the chaos present in Europe before and after World War One and during the Russian revolution meant that a scientific expedition did not study the explosion site until 1921. What they found was astonishing. At what should have been the impact point for whatever fell out of the sky, a stand of trees stood with their branches and bark stripped. Outward from there, for a distance of nearly 40 miles, every tree was laid flat. Aerial photos made of the area in 1938 showed that the trees were knocked down in a sort of butterfly-shaped pattern. Still, there was no crater to be seen. Whatever came to earth that day seemed to have exploded in mid-air.
Further expeditions to the site found tiny glass spheres embedded in the soil. The spheres were found to contain iridium and nickel in close proportion to the concentrations found in some meteorites. These findings led scientists to conclude that the most likely cause of the explosion was a meteorite which exploded several miles above the Earth’s surface. This would explain the lack of a crater and the upright trees found at ground zero. Model testing concluded that the butterfly-shaped damage pattern could have been caused by an object approaching the Earth at a 30 degree angle.
Of course, not all researchers agree on what happened at Tunguska. One competing theory states that the object was a comet. Comets are composed mainly of dust and ice, so one exploding high in the atmosphere would leave no trace and would help explain the bright night sky observed after the explosion. Geologists have discovered that the region in question was once very volcanic. Therefore, a theory has been put forward stating that nothing fell from the sky, but rather a large pocket of methane from the Earth exploded. This type of explosion has happened on a smaller scale at other locations around the globe, so it is not completely implausible.
From there, the hypotheses grow more and more incredible. Two researchers put forth a theory in 1973 that a small black hole passed through the Earth and caused the damage. If true, then there would have to be an “exit wound” on the other side of the Earth; none has been found. Three scientists hypothesized in 1965 that the explosion was caused by a chunk of anti-matter. What the scientists failed to explain was how the anti-matter got so close to the Earth without being annihilated by regular matter higher in the atmosphere. Ufologists have long theorized that a UFO could have caused the incident by losing control of it’s propulsion system and exploding mid-air. Let’s hope they did some re-design work after that.
Although any number of things may have happened at Tunguska in 1908, the meteorite theory makes the most sense. If a giant rock from space did, indeed, cause the explosion, then the site serves as a reminder to us that our tiny blue sphere is fragile and unprotected and that, eventually, something like this will happen again.