The broken glass and burned wreckage are still being cleared in the wake of the riots that convulsed Baltimore's streets on 27 April. The final trigger of the unrest was the funeral of a 25-year-old African-American man who had died in police custody, but observers point to many other root causes, from income inequality to racial discrimination. But for a few researchers who are studying Baltimore's unrest, the question is not the ultimate causes of the riot but its mechanism: How do such riots self-organize and spread? One of those researchers, Dan Braha, a social scientist at the New England Complex Systems Institute in Cambridge, Massachusetts, has been collecting data from Twitter that spans the riot from buildup to aftermath, part of a larger study of social media and social unrest around the world.
Q: What can you learn about the Baltimore riots from social media?
A: The protesters are mostly teens who use social media routinely. The riots that started around 3:30 p.m.—ignited by messages on social media urging high school students to “purge”—spread within 3 hours around the city. It's interesting to see the pattern of spread, much like forest fires, spreading in clusters and locally. The riots, in my view, could easily spread also across other cities in the United States where racial tensions are high and are close to a tipping point.