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Published on Oct 7, 2012
The animation shows how our scientific survey spread in Facebook. The survey is a Facebook app that people can share with their friends (https://sns.it.helsinki.fi/?sref=yt). The nodes (red and blue dots) represent people and the links between them are friendships. They light up as a new person joins the survey. The video shows what happened after we sent out invitations to students at the University of Helsinki. The red dots are women and the blue dots are men.
The network was drawn using the Fruchterman-Reingold algorithm, which puts friends close together and tries to spread out the network evenly. People are in the center if they have lots of friends or friends of friends in the sample.
Because people tend to have more of same sex friends, you can see that the colors tend to cluster in groups. Also it seems like there are more men (blue) in the most central core of the network.
You can see three big pulses in the animation. The first pulse in the beginning resulted after we sent out invitations to students at the University of Helsinki. The second, smaller pulse, came after we sent a reminder to the students. The third pulse two days later was caused by the Finnish public broadcaster Yle writing a news story about our research.