Sinan Aral is a professor at MIT Sloan School of Management and directs its Initiative on the Digital Economy and the Social Analytics Lab. His major new book The Hype Machine, coming in September, explains how social media changes who we know, what we do, and even how we think. As the world relies even more heavily on social media during Covid-19 and the upsurge against racism and police violence, he will help us understand what it means, and what individuals, companies, and society should do differently.