Last Friday, February 15: a date that will remain in history books forever. Before that day began, there’d only been a single authenticated instance of a person injured by a meteor – in all of human history.
Remember, records have been kept for millennia. Historical events have been carefully chronicled by the Chinese, the Romans, the Egyptians, and none had ever mentioned injuries caused by the kind of event that tore through the skies over Siberia last week. So we went from a single minor injury – when Ann Hodges of Sylacauga, Alabama was struck in the thigh by a meteorite in 1954 – to a thousand people cut and bleeding, with two in serious condition as of last weekend.
That this should have happened on the same day that the largest asteroid in memory was scheduled barely to miss Earth, at the paltry distance of 17,000 miles, makes it beyond astounding. Naturally, the first question is: Were the two events related?
Not at all. 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 ten or 12 miles per second. Various experts estimate its size from that of a car to that of a locomotive.
There’s more. Friday’s airburst meteor explosion was the largest since June 30, 1908, which also occurred over Siberia. I mean, is all this just a little freaky or what?
I’m just grateful that it didn’t happen last December 21, on the Mayan calendar date. If it had, there’d be no convincing anyone that the Mayas didn’t have the gift of prophecy. In fact, I think that I would have gotten over to the other side and joined them.
Interestingly, almost all of the injuries happened because of normal human behavior. After the flash, with a huge, weird, smoky streak now filling the sky, everyone went to the window to watch. When the shock wave struck – from two to five 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” this event as being not extraordinary. All astronomers have witnessed exploding or brilliant meteors, called bolides. This one just happened to be bigger. Obviously we collide with space debris all the time, and the rarity is merely a function of size. Six apple-seed-sized meteors streak visibly across your sky per hour, every single night. If you’re waiting for one that can 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. And those that almost wipe Earth clean, like the Permian event 251 million years ago? Maybe a few times per billion years.
As for the smaller meteor impacts, we’d been lucky until last week. A home is penetrated every one-and-a-half 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 a roof. It has been enough to penetrate the roof and the ceiling below, but rarely an additional floor.
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, many other instances. But people have been spared – until now.
As for terminology, the bright streak in the sky is a meteor. If it makes it to the ground as a stone, it’s then a meteorite. In space, dark and unseen before it hits our atmosphere, it’s a meteoroid. The ones that do make it all the way are nearly always asteroid pieces. By contrast, meteor showers are almost always comet fragments made of fragile ices that never survive their visit into the atmosphere.
In the course of a lifetime, the odds are with us, even if my old alma mater Discover Magazine predicted that each of us is 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 that you’ll be done in by cholesterol or a nicotine addiction. Still, if you ever do see a flash of light, don’t check it out through a closed window.