Local Projects

President Obama joined thousands today in marking the 10th anniversary of the September 11 attacks at the World Trade Center site in New York, laying his hands on a bronze memorial engraved with names of victims--a list arranged with the help of an algorithm.

The 2,983 names on 76 bronze panels surround two cascading pools of water where the towers stood, in architect Michael Arad's design "Reflecting Absence." In seemingly random fashion, the panels list those who died on September 11, 2001, as well as in the WTC bombing of February 26, 1993.

But the carefully thought-out memorial reflects the victims' complex web of relationships to one another--professional, social, and accidental. This was accomplished thanks to an algorithm created by data artist Jer Thorp working with New York design firm Local Projects.

Arad rejected arranging the names alphabetically or chronologically. The best way to set the names seemed to be one that wouldn't favor some people over others, so they're arranged according to groups and their relationships with one another.

National September 11 Memorial & Museum

The memorial's planners asked the families of victims for "meaningful adjacencies" showing friendships and other relationships among the victims. The roughly 1,200 responses, combined with formal affiliations and multiple requests per victim, represented an enormous puzzle for planners. Some computer scientists who were consulted said it couldn't be done, according to The New Yorker.

Some obvious group adjacencies, such as for investment bank Cantor Fitzgerald, which lost 658 employees, were complex. Others reflected chance encounters on 9/11 that ended in a shared place of death such as an elevator.

The algorithm, created in the open-source Processing language, first placed the victims in clusters and subclusters of related names according to groups and adjacency requests. They were then arranged according to the place of death, such as the north or south tower, the Pentagon, or United Airlines Flight 93, which crashed in Pennsylvania.

This led to about 99 percent of the requested adjacencies being honored. In addition, the system tackled problems such as name length, spacing between lines and potential interference between letters, and other aesthetic challenges--such as the fact that 12 panels are irregularly shaped. The designers worked with the output to produce the tribute.

"It would be misleading to say that the layout for the final memorial was produced by an algorithm," Thorp writes. "Rather, the underlying framework of the arrangement was solved by the algorithm, and humans used that framework to design the final result."

Finding a name on the memorial is straightforward. There are nine primary groups (including first responders, towers, and flights) divided into two tower pools. Each name has a code consisting of N for North Pool or S for South Pool, as well as a panel number. Names can be quickly located on this site.

The National September 11 Memorial opens Monday.

(Via Scientific American)