From the Editor

Lists, which are a staple of publishing because readers like them, also serve this purpose: they express what a publication thinks is important. Our annual list of 10 breakthrough technologies is a celebration of technological advances, but it’s also a map of our emphases.

Sometimes we care about a technology because it offers new conveniences. “Tesla Autopilot” describes how the carmaker sent its vehicles a software update that made autonomous driving a commercial reality. In “Conversational Interfaces” we report how Baidu’s voice recognition and natural language software provide Chinese mobile-device users with practical speech interfaces. In “DNA App Store” we write about a democratic approach to DNA sequencing in which consumers will share their genetic information to a common database and app developers will create products that use that information. Our profile of Slack accounts for the popularity of the workplace collaboration software by observing that the “ambient awareness” of an organization fostered by Slack’s single stream of short, casual messages “creates the perception that keeping in touch with coworkers is effortless.”

Sometimes we care about a breakthrough because new efficiencies significantly reduce the costs of a technology. The reusable rockets of SpaceX and Blue Origin will transform the economics of spaceflight, encouraging unimagined innovations. At ­SolarCity’s gigafactory in Buffalo, New York, the largest solar manufacturing facility in North America will make as many as 10,000 highly efficient solar panels every day. Efficiency matters because the panels themselves represent only 15 to 20 percent of the cost of installing a residential solar array. Much of the rest comes in what’s known as balance-of-system costs. ­SolarCity’s installation, says the company, will require one-third fewer panels to produce the same amount of electricity as conventional installations. Thus, according to Peter Rive, SolarCity’s chief technology officer, the gigafactory “sets us up for a future where solar plus batteries is cheaper than fossil fuels.”