uni'wissen 01-2016_ENG

Scientists will never be capable of predicting precisely how fast a freshly sent tweet on Twitter or a new message on Facebook will spread and how far it will travel, of that junior professor Dr. Peter Fischer is certain. But there’s another prediction the Freiburg computer scientist and his colleagues can make: Once a message has been circulating on social media for a certain period of time, they can say with relative precision how long it will continue to spread in the same way – in terms of speed as well as the number of people it will reach. “We have man- aged to reach 85-percent accuracy on this point,” says Fischer. Confirming Rumors Nowadays, social channels catapult informa- tion to all corners of the earth at the blink of an eye – from breakfast in Japan to dinner in Canada, from mountain climbing in Norway to surfing in South Africa. It’s not possible to reconstruct this dissemination process, much less control it. Some find this idea disturbing, while others find it fasci- nating. Peter Fischer is of the latter sort. The junior professor at the University of Freiburg’s Department of Computer Science is interested in the logic of the World Wide Web, especially the question of how and in what form information spreads. At the same time, he wants to find out what role users play in disseminating information and whether some people have more influence on the process than others. And if this is indeed the case, how can one find them? “Once we have reached a better understand- ing of how information spreads on social media, it will be possible to identify the source of a piece “We leave the content out of our analyses.” of information in a matter of seconds,” says Fischer. This would benefit journalists, enabling them to confirm the truthfulness of rumors spread online more quickly, but it would also allow all other users to determine where a piece of information originated. Another thing Fischer finds fascinating is our subjective perception of how frequently particular information appears on social media. Journalists cite well-known hashtags like #auf- schrei or #einearmlaenge – both referring to the topic of sexism and sexual assault in the wake of the incidents during the 2016 New Year’s Eve celebrations in Cologne – and then use them to piece together a story to show that this is a topic of great concern on social media and is therefore important for society. “The amazing thing is that these hashtags usually aren’t nearly as wide- spread as we would think they should be,” reports Fischer. Big Data Where does information come from? Who spreads it? Whom does it reach? In their quest to find answers to these questions, Fischer and his team deal with the bread and butter of com- puter scientists: big data. Twitter has more than 300 million users who post over 500 million tweets a day. Facebook has more than a billion users worldwide. That’s a lot of data. Under normal circumstances, a couple of thousand messages flow through the veins of the social networks each second. When there’s something important to commu- nicate, for instance when a celebrity dies or a terrorist attack happens somewhere, the net- work’s heart rate skyrockets to around 150,000 13uni wissen 01 2016 13 13uni wissen 01201613

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