Bill Gates thinks the world is heading into a rough stretch, and he has put a number on it. The Microsoft co-founder said in an interview that people should get ready for 20 years of turbulence driven by artificial intelligence. His argument is that the technology will change how people work and live faster than societies can adjust. Gates has long balanced excitement about AI with warnings about its side effects. He points to possible gains in medicine and productivity, but he insists preparation matters as much as the breakthroughs. His remarks land in the middle of a running debate over how fast AI should be reined in. When a man who helped build the software era sounds an alarm like this, plenty of people listen.