One summer afternoon in 2003, a sagging power line in Ohio touched an overgrown tree. About an hour later, roughly 50 million people across eight US states and Ontario were in the dark. This animated explainer follows the chain of small failures behind the biggest blackout in North American history.

Chapters:

0:00 Intro

0:26 Lights Out

1:22 Why Wires Sag

2:18 The Trees

3:23 The Silent Alarm

4:16 A Race Condition

5:28 The Cascade

6:37 Turning It Back On

7:37 Who Was to Blame?

8:41 The New Rules

• English AI voiceover

• Original synthesized music and sound effects, mixed to -14 LUFS

• Original vector animation in a clean neon style

• Fact-checked: the 14 August 2003 timeline, the frozen alarm software and its race-condition bug, the US-Canada task force findings and the mandatory reliability rules that followed

How one tree, one bug and one quiet control room switched off the lights for 50 million people.