oid—troy a city. tive tiddlers in Earts isalmost certainly in to track.
t one spotted until 1991, and t er it iced as it sailed past us at a distance of 106,000 miles—in cosmic termst of a bullet passing t toucer, anot larger asteroid missed us by just 90,000 miles—t pass yetrecorded. It, too, seen until it warning.
According to timoting in times a iced.
An object a be picked up by any Eartelescope untilit a fe is only if a telescope o be trained on it,. ting analogy t is al tively searceroids is feaff of a typical McDonald’srestaurant. (It is actually some mucrying to get people galvanized about tential dangers oftem, anot——lyunfolding in Italy from t Doy Laboratory atColumbia University. In ter Alvarez taccione Gorge, near to divided t layers of limestone—onefrom taceous period, tertiary. t knoo geology ast boundary,1and it marks time, sixty-five million years ago, wly vanishe fossil record.
Alvarez a ter of an inc could account for sucic moment in Eartory.
At time tional tinction ury earlier—namely t t overmillions of years. But ted t in Umbria, if1It is Kt rat because C ed for Cambrian. Depending on a or German Kreide. Botly mean “c Cretaceous means.
noely in tests existed for determining migaken to accumulate.
In t certainly t, but luckily ion to someone outside nuclear p;tac to rocks, but trigued occurred to t lie in dust from space.
Every year tes some ty tric tons of “cosmicsp in plainer language— if you s it intoone pile, but is infinitesimal ingare exotic elements not normally muc iridium, in space t (because, it ist, most of to t was young).
Alvarez kne a colleague of tory in California,Frank Asaro, ecion of clays using a process called neutron activation analysis. trons in a small nuclear reactor and carefully counting t ted; it remely finicky tery, but Alvarez reasoned t if tof one of tic elements in s annual rateof deposition, t aken to form. On an Octoberafternoon in 1977