Only last Saturday, an asteroid barely missed hitting Earth — meaning, it came closer than the Moon. And the preceding Thursday another one zoomed by. Making the threat more vivid, we just had, on June 30, the anniversary of the 1908 Tunguska Event, when an exploding asteroid above Siberia flattened every tree for 50 miles in all directions. Imagine if that had been a city below the incoming intruder. As it was, the sparsely inhabited area resulted in only three deaths in the tree-fall zone. The most vivid eyewitness account came from a local farmer, Semen Semenov, who the blast hurtled 50 yards across his yard, where he escaped with scratches and minor burns. He described the sudden brilliance as rivaling the Sun and emitting so much heat he was unsure whether or not to take off his shirt to prevent it from bursting into flame.
The next bruise from a space event happened in 1954 in Sylacauga, Alabama, where Ann Hodges, relaxing on her sofa, watched a meteorite burst through her ceiling and strike her on her upper thigh.
But the most injuries — over a thousand — happened back in Siberia again. This is one you may recall since it was just a dozen years ago. On Friday February 15, 2013, a space object came in from the Sun’s direction and exploded 18 miles above the city of Chelyabinsk, Siberia on the very same day that a known, expected asteroid, the largest in memory, was scheduled to barely miss Earth at the paltry distance of 17,000 miles.
The bigger asteroid, about half the size of a football field, loped its way past Earth at the slow speed of 4.8 miles per second. It approached us from the south. By contrast, the meteor that exploded over Siberia came from the northeast. Moreover, it was traveling at 10 or 12 miles per second, which matters because it’s speed that mostly determines the explosive force an object will deliver. Various experts estimate its size from that of a car to a locomotive.
Interestingly, almost all of the injuries in Chelyabinsk happened because of normal human behavior. After the flash, with a huge, weird, smoky white streak now filling the sky, everyone went to their window to see it. When the shock wave struck — between one and three minutes later, depending on the observer’s distance from the explosion — these windows couldn’t withstand the pressure and blew inward, showering everyone with glass. People described the shock as “hot air” which is how the 1908 airburst was characterized as well.
It was really a form of sound, like a souped-up version of thunder, which can also rattle windows if very nearby. That is, air pressure changes.
Now, one can also “play” these event as being not terribly extraordinary. All astronomers have witnessed exploding or brilliant meteors, called bolides. Obviously we collide with space debris all the time, and the rarity is merely a function of size. Six apple-seed-sized meteoroids streak visibly across your sky per hour, every single night after midnight, when your home has rotated to be on the forward-facing side of Earth. If you’re waiting for one that could destroy a city, well, figure once every one to four centuries. If you’re looking for an event that can wipe out half the animal species on the planet, figure maybe one impact every 100 million years.
As for the smaller meteor impacts, a home is penetrated every 1 1/2 years in North America alone. An asteroid fragment in the one to 100 pound range, if it doesn’t burn completely to dust or explode in the air, is slowed by air friction to a terminal speed of around 250 miles per hour. That’s the speed at which it hits the ground. It’s been enough to penetrate the roof, the ceiling below, but rarely an additional floor of homes.
So people, startled by a loud crash, have discovered a hole in the ceiling, damage within the room, and a black stony or metallic (and valuable) meteorite somewhere on the floor. This scenario repeated on March 26, 2003 in a Chicago suburb (when the meteorite hit a printer and just missed a teenager by a few feet), in Wethersfield Connecticut in November, 1982, in Lorton, Virginia in January 2010, and many other instances.
In the course of a lifetime, the odds are with us, even if my old Alma Mater, Discover Magazine, predicted that each of us are six times more likely to die in a meteor impact than in a commercial airliner crash.
That’s because when a truly big one does happen, we could all go at once.
Lest we leave this on such a dramatic note, however, remember that it’s infinitely more likely you’ll be done in by cholesterol or nicotine. Still, if you ever do see a flash of light, don’t check it out through a closed window.
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