The Boston Marathon bombings triggered Twitter's saddest day in five years, according to a group of scientists who track emotionally loaded tweets. The team's "hedonometer" scours the microblogging service for words with negative or positive emotional connnotations and uses them to compute a "happiness index" for users as a group.
According to the Washington Times, the team found that words like "explosion" and "kill" dropped the hedonometer down to the notable low, despite the fact that positive words like "love" and "prayers" were trending as well. "If we remove 'prayers', 'love', and 'families' it's not going to change the day's overall deviation from the background because of all the other words," said Chris Danforth, a mathematician from the University of Vermont who co-developed the system.
Other low points on the hedonometer in the past several years include the Newtown shootings in 2012, the Tohoku earthquake in 2011, and Michael Jackson's death in 2009.