Angles of a Hack

The idea of “hacking” has changed a lot from the days when it meant nosing around the phone system. Today computer hacking poses a strategic threat. But what about biohackers, who experiment with implanted electronic devices, or “hacking the climate” though geoengineering? In this second of two episodes, modern varieties of “hacking” and their consequences. Plus: when does hacking a system improve it?