For years now, social media has been where people go to find out what’s happening during a crisis; even aid agencies and emergency managers have come to rely on hashtags and live video to form a picture of how an event is playing out on the ground. But the hail of updates can be rapid and incoherent. ... sometimes there’s no information coming out of a disaster zone—because the internet has gone down, as happened in large parts of New York and New Jersey when Hurricane Sandy landed in 2012. This is another fundamental problem that Facebook is, almost by coincidence, working to solve. For the past two and a half years, the company has been developing a program to deliver the internet via drone to parts of the world that don’t have it. The business reason for this fanciful-sounding project is pretty straightforward: It will speed up Facebook’s efforts to expand globally and serve ads to even more people in what is already the world’s largest audience. But the team has always had the idea that the same technology could be vitally important in, say, an earthquake zone. ... This new incarnation of Safety Check begins with an algorithm that monitors an emergency newswire—a third-party program that aggregates information directly from police departments, weather services, and the like. Then another Safety Check algorithm begins looking for people in the area who are discussing the event on Facebook. If enough people are talking about the event, the system automatically sends those people messages inviting them to check in as safe—and asks them if they want to check the safety of other people as well.