ananyo writes "Facebook can lose a few users and remain a perfectly stable network, but where the national grid is concerned, simple geography dictates that it is always just a few transmission lines from collapse, according to a mathematical study of spatial networks. The upshot of the study is that spatial networks are necessarily dependent on any number of critical nodes whose failure can lead to abrupt — and unpredictable — 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. The authors say that this outage is an example of the inherent instability the study describes. But others question whether the team's conclusions can really be extrapolated to the real world. 'The problem is that this doesn't reflect the physics of how the power grid operates,' 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."