HOUSE OVERSIGHT 019419 published today in Nature Physics, is that spatial networks are necessarily dependent on any number of critical nodes whose failure can lead to abrupt— and unpredictable — collapsel The electric grid, which operates as a series of networks that are defined by geography, is a prime example, says Havlin. "Whenever you have such dependencies in the system, failure in one place leads to failure in another place, which cascades into collapse." The warning comes ten years after a blackout that crippled parts of the midwest and northeastern United States and parts of Canada. In that case, a series of errors resulted in the loss of three transmission lines in Ohio over the course of about an hour. Once the third line went down, the outage cascaded towards the coast, cutting power to some 50 million people. Havlin says that this outage is an example of the inherent instability his study describes, but others question whether the team's conclusions can really be extrapolated to the real world. "I suppose I should be open-minded to new research, but I'm not convinced," says Jeff Dagle, an electrical engineer at the Pacific Northwest National Laboratory in Richland, Washington, who served on the government task force that investigated the 2003 outage. "The problem is that this doesn't reflect the physics of how the power grid operates." Critical order Havlin and his colleagues focused on idealized scenarios. They found that randomly structured networks — such as social networks — degrade slowly as nodes are removed, which in the real world might mean there is time to diagnose and address a problem before a system collapses. By contrast, the connections of orderly lattice structures have more critical nodes, which increase the instability. The problem is that such orderly networks are always operating near an indefinable edge, Havlin says. To reduce that risk, he recommends adding a small number of longer transmission lines that provide