3:05 PM > In northeastern Ohio, a line carrying 345,000 volts touches a tree limb the utility company had neglected to trim. After a flash of sparks, safety equipment automatically kills the electricity.  3:39 > The first of 16 high-voltage lines in the Akron area trips. Since electricity can’t be turned off like water from a spigot, lines overheat, sag, then hit more branches and trip.  4:05:57 > The Sammis-Star high-voltage line outside Cleveland shuts down. This is, a later report explains, the “last point at which a cascade of line trips could have been averted.”  4:07:00 > Four of the five Handsome Lake turbines in Western Pennsylvania go offline. Within the next several minutes, more than 500 generating units in the United States and Canada, including at 10 nuclear facilities, shut down.  4:10:37 > Four units at a power plant near Detroit go off. When a subsequent run on gas leaves some stations dry, Michigan’s governor signs an order rushing nearly a million gallons of fuel into the area.  In our wired society, surviving even a day without electricity can be a hardship. But thanks to the combination of freak storms and a groaning grid, darker days may still be ahead.  4:10:38 > A huge power surge sweeps across Pennsylvania, New Jersey, and New York, through Ontario, and into Michigan. As the blackout grows, the Air Force scrambles jets, in case the blackout is part of a terrorist attack.  4:10:46 > When Cleveland’s electricity shuts down, so do the pumps supplying 1.5 million people with drinking water from Lake Erie. The mayor declares a state of emergency and calls in the National Guard to help.  4:10:48 > As power drops in New York and New Jersey, subway and commuter trains stop dead. One spends nearly two stifling hours beneath the East River. Traffic jams grow dozens of miles long.  4:10:54 > The last of more than a dozen lines connecting New York to New England trips, creating a surge that threatens part of Vermont. Amtrak rolls to a stop, stranding as many as 18,000 people. At Six Flags in Agawam, a roller coaster freezes mid-ride and passengers need to be walked off.  4:12 When the cascade finally ripples to a close, 50 million people are without power. Although most will see it restored within hours, parts of Manhattan remain dark for days and Ontario has a week of rolling blackouts. The price tag? An estimated $10 billion.
Just how interconnected is our grid? Interconnected enough that the largest blackout in North America’s history – one that left 50 million people without power – could essentially start when a single tree branch touches a single power line.