Iron is a great material for making tools. But the oldest known iron artifacts were actually intended for decoration :nine Egyptian beads that date back to 3200 B.C. And now we know that this ancient jewelry has an even more impressive origin-the iron out of which it was crafted came from space. The metal cylinders were discovered in Egypt in 1911. To analyze the structure and chemical composition of the beads ,researchers bombarded them with neutrons and gamma rays. The tests revealed that the jewelry contained trace elements not present in Earthly ores-but that are found in iron-rich meteorites. The meteoric metal was hammered flat and rolled into beads more than 5,000 years ago. This date is some 1,500 years before the invention of smelting. That technique made it possible for terrestrial iron tobe shaped into tools ,and to supplant copper and brone as civilization's metal of choice. The new finding shows that long before smelting revolutionized tool use, some humans were already rion men.
网友评论