Read about the 7 Most Critical Space Missions here.

USA And Canada, 2003

The world's most technologically advanced country is hardly one you'd expect to see on a list like this! On August 14, 2003, USA witnessed the largest blackout in its history when a series of power line failures began to snowball, eventually leaving over 50 million people in the dark--some for over 24 hours! This one affected Canada as well.

The series of failures was eventually traced back to Ohio after a seriously lengthy and detailed investigation. Of course, given the heightened state of paranoia the country was in after the 9/11 attacks, it makes sense that they immediately connected the unexpected power shortage with the possibility of a looming terrorist attack. Today, the Americans seem to have learned their lesson for being over-dependent on power and even mark something called the 'blackout challenge' in a few states on August 14!