Today a historic and extraordinary event happened: A meteor exploded over the Russian city of Chelyabinsk, causing a shock wave that blew out windows in thousands of buildings, and injured more than 1,000 people, mostly from broken glass. (The meteor caused a tremendously bright flash of light, and people went to windows to see what was happening only to be hit by the shock wave.) This event was extraordinary because it is the largest known such event since the 1908 Tunguska event (a 5 megaton blast that flattened trees over an 800-square-mile region in a remote region in Siberia); no other similar event has caused this kind of damage. Because Russians often have dash cams in their car (to prove their innocence in accidents or road rage incidents), there was an abundance of spectacular video clips. These show the sudden appearance of a bright streak of light which quickly traveled across the sky and became much brighter---a parking lot security video showed the light overwhelming the sunshine and saturating the camera. Terrifying video clips show people looking at the sky at a huge trail of smoke and being surprised by a tremendous boom which blew out windows and set off car alarms.
The Russian authorities estimated that the meteor responsible for the event was 10 tons, which would produce about 1 kiloton of energy. This same number was repeated on NBC News and PBS News Hour this evening. However, NASA JPL and other experts said the meteor was 7000 or 8000 tons in size, and that it released 300-500 kilotons of energy, equivalent to 20 times the Hiroshima atom bomb (which was 15 kilotons). These estimates were based on an international network of infra-sound sensors intended to detect nuclear tests. (The Russian meteor also generated seismic signals; I read equivalent to a 2.7 magnitude earth quake; this should also allow a good estimate of the energy yield of the event, but I haven't seen anything specific about that.)
Early this evening, I was listening to an old CD while doing some housework, a collaboration by David Sylvian and Robert Fripp called The First Day. One song on this album contains the refrain "Heaven will stone you, but Jean the Birdman pulls it off!" I can't claim that my subconscious didn't direct me to select that album to listen to, but the coincidence surprised me.
Added at 2013-02-15 2200:
When I was a kid, I remember reading that comets were once an omen of terror in a pre-scientific world, a sign of coming calamity; but in the modern world, comets were known to be a harmless astronomical phenomenon. But this pleasant view of comets dissipated in the 1960s when it was realized that they are a real threat to Earth: a comet is essentially an asteroid largely composed of ice, and anything of that size (kilometers in diameter) contains an incredible amount of kinetic energy. Indeed, in the late 1970s came the discovery that an asteroid hit the Earth near Yucatan about 65 million years ago, killing off the non-avian dinosaurs and many other species. (This was very unsettling to geologists, who were reluctant to accept this discovery; it was too similar to the catastrophism geology overcame in the 19th century as it freed itself from old religious dogmas.) The problem with comets is this: Unlike asteroids, which can be detected and whose orbits can be mapped, comets regularly appear from the outer solar system with no warning. I recall the comet Hyakutake, which was discovered on January 31, 1996 and made a close pass to Earth in March of that year. Hyakutake was a beautiful sight--a bright cotton ball of light (visible even in a brightly-lit downtown city) which showed a long tail when viewed from dark rural skies. But there was no particular reason why it couldn't have hit the Earth, and we would have had less than 2 months of warning. The probability of such an even in any given year is very small, but a slogan that appeared on the internet is apt: Asteroids are nature's way of asking, "How's that space program coming along?"
By the way, it turns out that about 150 impact craters or structures have been found on the Earth's surface. Two of these are in Kentucky, one of which is a 6 km structure at Owensboro (the city is actually inside the structure), and the other is a 1.5 km structure near Versailles, about 20 km west of Lexington. The first is said to be less than 300 million years old; the other less than 400 million years old.
(2013-02-16: Edited to remove comments about reporters.)