A Facebook intern interested in seeing how political borders affect friendships around the globe has created a map of the world by sampling data from the social network's 500 million user base.

The map displays friendships as lights on a deep blue background. The eastern half of the United States and Europe shine the brightest, while China, Russia and central Africa, where Facebook has little presence, are mainly dark.

"I was interested in seeing how geography and political borders affected where people lived relative to their friends," said Paul Butler, an intern on Facebook's data infrastructure engineering team.

"I wanted a visualization that would show which cities had a lot of friendships between them."

More details on how he crafted the map are at www.facebook.com/note.php?note_id=469716398919.