Not so long ago, scientists could not bring themselves to believe stones could fall from the sky. In 1795 the French chemist Lavoisier, who had become famous for his discovery of oxygen, declared it was impossible. Then in 1811, near the village of La Leigle, hundreds and hundreds of stones were found scattered over an area of several square miles. Detractors had a bit of a problem dismissing that so lightly, and before long it became accepted wisdom.
4000 years ago, in the high Altiplano of northern Argentina, 50 tons of iron rocks fell in a place which the Indians named "Campo del Cielo"- the field of the Sky. In 1576 the conquistadors heard of it and used some to repair their equipment. Then in the 90s, a Brit called David Bryant was given permission to go there and take everything he could pack into his Land Rover. And last week I bought a piece of that fall from him. Fitting comfortably in the hand, but weighing a chunky 2 kg, it bears the "sculpting" marks from its journey through the atmosphere, as well as a small impact crater which probably formed while it was in deep space. 92% iron, 7% nickel and 1% cobalt, iron meteorites are believed to come from the iron cores of large planetoids which existed in the early life of the solar system about 4.2 billion years ago, but then collided in cataclysmic explosions, showering fragments throughout local space. There, some of them formed into "rubble piles", collections of stones kept together by gravity, orbiting the sun for billions of years before being perturbed in some way, and beginning their slow spiral towards Earth- and me.
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