人类圈：地球轨道上的人造物质层

We’re putting more stuff into space than ever before. Here’s what’s up there. By Jonathan O’Callaghan Illustrations by John MacNeill Earth’s a medium-size rock with some water on top, enveloped by gases that keep everything that lives here alive. Just at the edge of that envelope begins a thin but dense layer of human-built, high-tech stuff. People started putting gear up there in 1957, and now it’s a real habit. Telescopes look up and out at the wild universe. Humans live in an orbiting metal bubble. In the last five years, the number of active satellites in space has increased from barely 3,000 to about 14,000—and climbing. …