The day of the Boston Marathon was the saddest day in nearly 5 years of observations by a team of scientists from the University of Vermont and The MITRE Corporation. Their on-line "hedonometer"—an online sensing device—shows a drop in global happiness associated with the bombings at the race. For the first time, results from the hedonometer are being made available to the public for free at a new website,www.hedonometer.org. The technique is a bit like a global microscope that draws in millions of words in English from around the world—using Twitter and, soon, sources like CNN transcripts, Google Trends data, New York Times stories and others—and that lets the scientists, and now the public, view the aggregate mood reflected by all these words. These happiness trends can be observed over time and different locations can be compared.