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Tunguska Blast Was a Small Asteroid
malachiorion writes "The Tunguska event, an explosion on June 30, 1908, cleared an 800-sq.-mi. swath of Siberian forest. Was it a UFO crash? An alien weapons test? Now, Sandia National Laboratories has released its own explanation for the Tunguska event. Using supercomputers to create a 3D simulation of the explosion, the Department of Energy-funded nuke lab has determined that Tunguska was, indeed, the explosion of a relatively small asteroid. The simulation videos are well worth checking out — they show a fireball slamming into the earth from the asteroid's air burst. The researchers caution that we should be keeping watch for many more small, potentially earth-impacting asteroids than we are currently tracking."
...how the populations (including the military) in some of the more... nervous areas of the globe would react to a suddden blinding light in the sky followed by an enormous blast wave.
"None are more hopelessly enslaved than those who falsely believe they are free." -- Goethe
Perhaps these dramatic presentations aren't really that helpful. It could be that volcanoes won't erupt under Los Angeles, ice hurricanes won't hit New York, and 10.0 earthquakes won't toss Los Angeles into the Pacific Ocean (and why isn't Chicago or London ever destroyed?). It might be helpful for you to calculate the area that the Tunguska Blast caused devastation, divide by the surface area of the earth, multiply it by the surface area of our major population centers, and then multiply it by the probability of this type of event occurring in the next 50 years. But this is boring and lacks the 'scary thinking' and drama, right?
A 3-5 megaton blast over the Atlantic wouldn't cause so much as a rough surf advisory in Key West. In comparison, the USA built a 45 megaton bomb and the USSR's fission-fusion-fission Tsar Bomba would have been 100+ megatons had they not taken the sensible precaution of replacing the final fission stage with inert lead. If a mere 5 megaton warhead could cause such worldwide devastation, I'm pretty sure someone would have mentioned it before now (and trust me, I've read just about every far-fetched doomsday scenario imaginable.)
As for the possibility of similar-sized asteroid impacting the ocean instead of exploding above it--well, the article only says that the asteroid is now thought to be "only a fraction as large as previously published estimates". That doesn't tell us anything. The Tunguska asteroid may or may not have been large enough to trigger a tsunami had it impacted an ocean instead of exploding over land. I'm going to assume that an impact will usually be less energetic (though perhaps more concentrated) than a heat-induced explosion, in which case no, the Tunguska asteroid never posed a significant threat to the world as a whole.
That said, the Tunguska explosion is still fascinating as hell. I know that there's a lot of very strong evidence pointing to the asteroid theory, but it's still fun to toy with conspiracy theories. The atomic bomb was first being conceived of, Tesla's Wardenclyffe Tower was being tested (by some accounts, it was brought online the day before the explosion)... it's all absolute rubbish, to be frank, but it's very entertaining rubbish.
It is worth reading the article. An asteroid impact is sexy, but the alternative explanation fits with the data much better. And how does a natural gas explosion leave the nickel and iridium deposits that were found at the site? An asteroid impact is not the accepted theory because it is "sexier", but because of Occam's razor.