The blackout that turned out the lights for millions of Americans and Canadians on Thursday once again showed how the interconnected engines of modern life are vulnerable to massive disruptions.
Nuclear plants stopped running. People were trapped in subways and elevators. Planes were grounded. Traffic lights went out.
And, until they learned otherwise, those caught in the steam of summer asked whether America had been attacked again.
"It shows us we have tied together so many systems to build a high quality life, and that creates its own vulnerabilities," said James Gilmore, the former governor of Virginia and chairman of a terrorism panel formed by Congress.
The electric grid is perhaps the most vulnerable of the country's critical systems. Grids are interconnected and, unlike natural gas that can be stored, electricity must be produced in real time, when it is needed.
"With electricity, if there's a loss of a major transmission line or generator, the system can come under an unstable situation where there's too much demand and too little supply," said Tony Anthony, spokesman for the Edison Electric Institute, an organization of shareholder owned electric utilities.
New Mexico Gov. Bill Richardson, energy secretary during the Clinton administration, said the blackout underscored the need for Congress to require national standards for the reliability of the electric power system.
"In my view we're the world's greatest superpower but we have a Third World electricity grid," Richardson said. "We have antiquated transmission lines. We have an overloaded system that has not had any new investments and we don't have mandatory reliability standards on utilities, which caused this problem."
National standards, Richardson said, "are needed to prevent utilities from having more power than they can absorb. It's as simple as that."
In a post-Sept. 11 environment, there clearly was a psychological effect.
"When something like this happens and you have to come down from the 37th floor it makes you wonder, was this terrorism or what?" said John Meehan, 56, who walked down that many stories in a Cleveland office building.
Larry Brown, one of the institute officials who advises the government on electric grid vulnerabilities, said there are three reasons that better facilities have not been built: the cost, environmental opposition and the unwillingness of communities to locate such facilities near homes.
Brown said the energy bill now before Congress would provide needed financial incentives. But that will not stop lawsuits by environmentalists or local opposition.
"Things like this can wake people up to the reality that society relies on electricity, and expects electricity to be reliable. But reliability depends on facilities," he said.
There was a bright spot Thursday: States and cities didn't seek federal help in the immediate aftermath of the outage.
As reports of the blackouts came in, the Homeland Security Department readied teams to respond to terrorist strikes, telecommunications outages and other problems that could be related to the outage.
As of 9 p.m., more than five hours after the breakdown, there were no requests for federal assistance, said Brian Roehrkasse, spokesman for the department.
Coupled with the lack of problems at facilities like hospitals and prisons, which ran from backup power, the response suggested many states and localities had good plans in place, he said.
"I think this situation indicates that technology is imperfect and at times will fail," Roehrkasse added. "This indicates the importance of having in place protections to guard our critical infrastructure as well as crisis plans for when the infrastructure becomes inoperable."