Paul Butler, who was an intern with Facebook’s data infrastructure engineering team, plotted the friendship networks using current city locations listed on people’s profiles.
“When the data is the social graph of 500 million people, there are a lot of lenses through which you can view it. One that piqued my curiosity was the locality of friendship,” Paul Butler writes on the company’s blog.
“I was interested in seeing how geography and political borders affected where people lived relative to their friends. I wanted a visualization that would show which cities had a lot of friendships between them.”
Applying longitude and latitude coordinates for each city, he then added curved connecting lines between friends to create a unique visualisation of the world. In areas with more friendships he increased the brightness.
“I defined weights for each pair of cities as a function of the Euclidean distance between them and the number of friends between them.”
“Then I plotted lines between the pairs by weight, so that pairs of cities with the most friendships between them were drawn on top of the others.”
“I used a color ramp from black to blue to white, with each line’s color depending on its weight. I also transformed some of the lines to wrap around the image, rather than spanning more than halfway around the world.”
Remarkably, the placing of continents and country boundaries is fairly accurate although some areas are noticably missing.
The areas with the most friendship connections are primarily within Western Europe and North America. China and most of Asia are absent from the map as well as most of central Africa where Facebook has little presence.
“After a few minutes of rendering, the new plot appeared, and I was a bit taken aback by what I saw. The blob had turned into a surprisingly detailed map of the world.”
“Not only were continents visible, certain international borders were apparent as well. What really struck me, though, was knowing that the lines didn’t represent coasts or rivers or political borders, but real human relationships.”
“Each line might represent a friendship made while travelling, a family member abroad, or an old college friend pulled away by the various forces of life.”
“Later I replaced the lines with great circle arcs, which are the shortest routes between two points on the Earth. Because the Earth is a sphere, these are often not straight lines on the projection.”
“When I shared the image with others within Facebook, it resonated with many people. It’s not just a pretty picture, it’s a reaffirmation of the impact we have in connecting people, even across oceans and borders.” [via The Telegraph (UK)]