标题: 《Periodic Table Iridium 》作者：- Michael Swanwick 【EPUB】 [打印本页] 作者: zaq 时间: 2013-8-19 10:03 标题: 《Periodic Table Iridium 》作者：- Michael Swanwick 【EPUB】 Michael Swanwick's Periodic Table of Science Fiction 77 Ir Iridium 192.22 Don't Look to the Skies! I stared out into the cloudless blue Cretaceous sky. "I don't see anything coming." "I wanted to get here early," Rachel said. "There'll be more time travelers soon, though. The last day of the Age of Dinosaurs has got to be a hot-ticket destination." "No, I mean I don't see any sign of the Chicxulub impactor?the comet or meteor or whatever it is that's supposed to be about to smash into the Earth. Shouldn't we be able to see it from here?" Rachel squinted into the sky. "You'd think. It certainly is a mystery." "So how do we know we came to the right time?" "Stratigraphy, old son. Way back in the twentieth century Alvarez p??re et fils realized that a thin boundary of clay marking the boundary between the Cretaceous and the Tertiary was unnaturally rich in iridium, no matter where in the world you examined it. Iridium is a lot more common in comets and asteroids than it is on Earth. So they postulated something big hit the planet, burned the forests, and killed the dinos?probably in the long nuclear winter afterwards." "Sounds dangerous." "No need to worry. We'll only be here long enough to snap a few photos. We'll cut out before the destruction actually reaches us." "Good. Hey! Isn't iridium the same stuff that's used to power our time machines? You don't suppose??" "No, no, of course not," Rachel said dismissively. "Oh, yes, certainly, there's a chance