Fake news is enemy No. 1 right now. Companies and governments are trying to figure out who should be in charge of spotting misinformation and getting rid of it. MIT researcher Sinan Aral has found that the not-true stuff, what he calls “false news,” is not only hard to stop, but also really effective. A study published last spring found that false news travels way more efficiently and much farther than the truth. In a recent article in the Harvard Business Review, Aral said misinformation can come at a real cost. (This interview originally aired Aug. 27.)