It began with a few small mistakes.

Around 12:15, on the afternoon of August 14, 2003, a software program that helps monitor how well the electric grid is working in the American Midwest shut itself down after after it started getting incorrect input data. The problem was quickly fixed. But nobody turned the program back on again.

A little over an hour later, one of the six coal-fired generators at the Eastlake Power Plant in Ohio shut down. An hour after that, the alarm and monitoring system in the control room of one of the nation’s largest electric conglomerates failed. It, too, was left turned off.

Those three unrelated things—two faulty monitoring programs and one generator outage—weren’t catastrophic, in and of themselves. But they would eventually help create one of the most widespread blackouts in history. By 4:15 pm, 256 power plants were offline and 55 million people in eight states and Canada were in the dark. The Northeast Blackout of 2003 ended up costing us between $4 billion and $10 billion. That’s “billion”, with a “B”.

But this is about more than mere bad luck. The real causes of the 2003 blackout were fixable problems, and the good news is that, since then, we’ve made great strides in fixing them. The bad news, say some grid experts, is that we’re still not doing a great job of preparing our electric infrastructure for the future.

Power was restored today in India, where more than 600 million people had been living without electricity for two days. That's good news, but it's left many Americans wondering whether our own electric grid is vulnerable.

Here's the good news: The North American electric grid is not likely to crash in the kind of catastrophic way we've just seen in India. I'm currently interviewing scientists about the weaknesses in our system and what's being done to fix them and will have more on that for you tomorrow or Friday.

In the meantime, I wanted to share a chapter from Before the Lights Go Out, my book about electric infrastructure and the future of energy. If you want to understand why our grid is weak, you first need to understand how it works. The key thing to know is this—at any given moment, in any given place, we must have an almost perfect balance between electric supply and electric demand. Fluctuations of even fractions of a percent can send parts of the system towards blackout.

More importantly, that careful balance does not manage itself. Across North America there are people working, 24-7, to make sure that your lights can turn on, your refrigerator runs, and your computer works. They're called grid controllers or system operators. Most utility customers have never heard of these guys, but we're all heavily dependent on them. They keep the grid alive and, in turn, they keep our lives functioning—all without the benefit of batteries or any kind of storage.

Joel Mickey has worked behind the curtain for twenty-five years, controlling the flow of electricity first for the Houston Light and Power utility company and now for ERCOT, where he’s the director of market operating systems ... Like a lot of controllers, he worked his way up the pole, literally, starting out as an eighteen-year-old lineman —one of the people who show up on your block whenever a rogue tree branch takes out an electric wire. On Mickey’s desk at ERCOT, there’s a black-and-white photo of a very young kid in a hard hat, with a leather harness cinched around his hips. Linemen are a noticeable part of the electric system, but, at least when Mickey started working, they weren’t considered terribly special. Along with maintenance workers at substations and power plant operators, entry-level jobs such as this were lumped together under one bad pun—“Plant Life,” the single- celled algae at the bottom of a Great Chain of Being, which regarded the wizards of system control as the epitome of creation. It was pos- sible to evolve your way up the chain, but it wasn’t easy.