It was one hundred years ago today that the Tunguska Event happened.
For those of you who haven't yet been introduced to this happening, here's a brief description: One hundred years ago today, way off in the wilds of Siberia, some kind of meteor (most likely; although there are those who think it was a comet nucleus) came streaking down, exploding as it entered the lower atmosphere. The meteor itself was probably about sixty meters across, according to the best modern estimates--think that it was about the height of a fifteen-story building. The explosion probably would have measured 5.0 on the Richter scale, except that this scale hadn't been invented yet. Measured in terms of nuclear weapons, Wikipedia reports that it had a blast most likely similar to a 15 or 20 Megaton bomb--about a thousand times more energetic than the one we dropped on Hiroshima, and roughly a third as powerful as the biggest three-stage thermonuclear warhead tested by the Soviet Union. The blast knocked down trees for several tens of miles from the blast point; it broke windows for hundreds of miles around; and, according to one school of thought, it produced an impact crater which is now a lake.
It was very fortunate that the blast was in such a remote location; but there were eyewitnesses who survived to tell the tale. Also from Wikipedia:
"We had a hut by the river with my brother Chekaren. We were sleeping. Suddenly we both woke up at the same time. Somebody shoved us. We heard whistling and felt strong wind. Chekaren said, 'Can you hear all those birds flying overhead?' We were both in the hut, couldn't see what was going on outside. Suddenly, I got shoved again, this time so hard I fell into the fire. I got scared. Chekaren got scared too. We started crying out for father, mother, brother, but no one answered. There was noise beyond the hut, we could hear trees falling down. Chekaren and I got out of our sleeping bags and wanted to run out, but then the thunder struck. This was the first thunder. The Earth began to move and rock, wind hit our hut and knocked it over. My body was pushed down by sticks, but my head was in the clear. Then I saw a wonder: trees were falling, the branches were on fire, it became mighty bright, how can I say this, as if there was a second sun, my eyes were hurting, I even closed them. It was like what the Russians call lightning. And immediately there was a loud thunderclap. This was the second thunder. The morning was sunny, there were no clouds, our Sun was shining brightly as usual, and suddenly there came a second one! "Chekaren and I had some difficulty getting out from under the remains of our hut. Then we saw that above, but in a different place, there was another flash, and loud thunder came. This was the third thunder strike. Wind came again, knocked us off our feet, struck against the fallen trees. "We looked at the fallen trees, watched the tree tops get snapped off, watched the fires. Suddenly Chekaren yelled 'Look up' and pointed with his hand. I looked there and saw another flash, and it made another thunder. But the noise was less than before. This was the fourth strike, like normal thunder. "Now I remember well there was also one more thunder strike, but it was small, and somewhere far away, where the Sun goes to sleep."Anyway, this event has become somewhat legendary among certain nerd circles. It's not something that happens every day, after all! And that's a good thing. The trouble is, if this had happened--say--thirty years ago instead, it would have been mistaken for a nuclear first strike, and the results would likely have been very, very bad.
But this is nevertheless a totally natural occurrence, and it's going to happen again at some point. While a space rock sixty meters across seems pretty big to us--especially when compared against human-sized structures--it really is too small for our astronomers to reliably detect and track. We can detect much bigger objects, and there are a bunch of these in Earth-crossing orbits; judging from how many of those we know about, it's likely there are many, many more out there of the Tunguska-sized variety.
But! Despite the depressing and dangerous nature of this threat to our comfortable existence, this event still rates really, really high on the "That's just freakin' cool" meter. At least it does for me, and I suspect I'm not the only one. "The universe is throwing really big rocks at us? That is just totally freakin' awesome!"
I'm not the only one who thinks this, right?
Anyway, happy Tunguska Day. Many happy returns. Or not, as the case may be.