In 1957, a beach-ball-shaped satellite hurtled into the sky and pierced the invisible line between Earth and space. As it rounded the planet, Sputnik drew an unseen line of its own, splitting history into distinct parts—before humankind became a spacefaring species, and after. "Listen now for the sound that will forevermore separate the old from the new," one NBC broadcaster said in awe, and insistent that others join him. He played the staccato call from the satellite, a gentle beep beep beep.

Decades later, we are not as impressed with satellites. There have been thousands of other Sputniks. Instead of earning front-page stories, satellites stitch together the hidden linings of our daily lives, providing and powering too many basic functions to list. They form a kind of exoskeleton around Earth, which is growing thicker every year with each new launch.