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rfmcdonaldMultiple people on my friends list have observed that today, the 30th of June 2008, marks the one hundredth anniversary of the Tunguska event.
William K. Hartmann's attempted reconstruction of the event and David Darling's encyclopedia entry are both worth reading. Each comes to the same conclusion: The Tunguska event was not the product of the collision of a black hole and/or an alien spacecraft with the Earth, but almost certainly the product of the collision of some sort of cometary fragment with north-central Siberia.
Some sources suggest that, had the object arrived 4h47m later, it would have collided with St. Petersburg, destroying that city with very major consequences for world history.
At around 7:17 a.m. local time, Tungus natives and Russian settlers in the hills northwest of Lake Baikal observed a column of bluish light, nearly as bright as the Sun, moving across the sky. About 10 minutes later, there was a flash and a sound similar to artillery fire. Eyewitnesses closer to the explosion reported the sound source moving east to north. The sounds were accompanied by a shock wave that knocked people off their feet and broke windows hundreds of miles away. The majority of eyewitnesses reported only the sounds and the tremors, and not the sighting of the explosion. Eyewitness accounts differ as to the sequence of events and their overall duration.
The explosion registered on seismic stations across Eurasia. Although the Richter scale was not developed until 1935, in some places the shock wave would have been equivalent to an earthquake of 5.0 on the Richter scale[citation needed]. It also produced fluctuations in atmospheric pressure strong enough to be detected in Great Britain. Over the next few weeks, night skies were aglow such that one could read in their light, from dust suspended in the stratosphere by the explosion. In the United States, the Smithsonian Astrophysical Observatory and the Mount Wilson Observatory observed a decrease in atmospheric transparency that lasted for several months, also from the suspended dust.
William K. Hartmann's attempted reconstruction of the event and David Darling's encyclopedia entry are both worth reading. Each comes to the same conclusion: The Tunguska event was not the product of the collision of a black hole and/or an alien spacecraft with the Earth, but almost certainly the product of the collision of some sort of cometary fragment with north-central Siberia.
To many, this event - the biggest space impact of modern times - serves as a reminder of the continuing threat posed to our planet by objects from space.
If the Tunguska "impactor" had exploded over a major city such as London, the death toll would have been up in the millions.
"Everything within the M25 would have been wiped out," Dr Mark Bailey, director of the Armagh Observatory in Northern Ireland, told BBC News.
The effects of Tunguska were not limited to Siberia. In London, it was possible to read newspapers and play cricket outdoors at midnight. This is now thought to have been due to sunlight scattered by dust from the fireball's plume.
The Russian mineralogist Leonid Kulik visited the region in 1921, interviewed local eyewitnesses and soon realised that a meteorite must have been the cause.
Some sources suggest that, had the object arrived 4h47m later, it would have collided with St. Petersburg, destroying that city with very major consequences for world history.
