Sound vs. Light: Exploring Speed Limits

As it has with so many other trends, the pandemic has hastened the decline of democracy and human rights; covid-19 provides autocrats with perfect cover. The plummeting price for the cobalt that powers electronics has upended lives and driven crime in the Democratic Republic of Congo. And how physicists found an upper bound for the speed of sound. For full access to print, digital and audio editions of The Economist, subscribe here www.economist.com/intelligenceoffer