Where the Sky Fell

imagesFrom my column in the November issue of Madison Magazine:

In the hills of far western Wisconsin, there is a hole that, when first made, was four miles across and three quarters of a mile deep. It is called, in a somewhat understated way, the “Rock Elm Disturbance,” and it was made by a giant rock that hit the ground from outer space.

I drove there because I wanted to see an impact crater with my own eyes. It was something I’d wanted to do since a few years ago, when I was happily reading along in Bill Bryson’s witty and informative book, A Short History of Nearly Everything, when I came across some PIA02940_modest-1startling facts.

According to Bryson, some “two thousand asteroids big enough to imperil civilization regularly cross our orbit,” and as many as “millions” of smaller ones—big enough to destroy a city—do, too. The number of known “near-earth asteroids” has gone from ninety-seven in 1980 to 6,384 today. [updated numbers here] The first planet killer wasn’t even spotted until 1991, and near misses are thought to happen as many as two or three times a week.

Read the rest here.

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