On July 23, 2012, billions of tons of plasma exploded from the Sun and raced out into space in what was one of the most powerful solar storms ever recorded. And it's only by chance that Earth wasn't in the way of this gargantuan coronal mass ejection, or CME. "If it had hit, we would still be picking up the pieces," Daniel Baker of the University of Colorado told NASA. And that may be putting it mildly. A CME of the size that almost hit us in July of 2o12 would probably knock out satellites we depend on for modern telecommunications and also cause global blackouts lasting for months. Everything that plugs into a wall socket would be disabled. And as NASA puts it, "Most people wouldn't even be able to flush their toilet because urban water supplies largely rely on electric pumps." For a good overview of the solar storm that almost caused this kind of mayhem in 2012, and how it compared to the notorious Carrington event of September, 1859 (which set telegraph lines on fire and caused auroral displays as far south as Cuba), check out the video above. "I have come away from our recent studies more convinced than ever that Earth and its inhabitants were incredibly fortunate that the 2012 eruption happened when it did," Baker says. "If the eruption had occurred only one week earlier, Earth would have been in the line of fire." The cloud of particles, rocketing outward at 3,000 kilometers per second — more than four times faster than a typical CME — hit NASA's STEREO-A spacecraft. As a result of its design, and the fact that it travels in interplanetary space (a much safer place, it turns out, that inside Earth's magnetosphere), the spacecraft survived and transmitted valuable data and imagery back to Earth.
The NASA video above includes some of that imagery. Other spacecraft also captured direct and indirect evidence of the event, and you can see some of that in the video too. Earth stands about a 12 percent chance of actually being hit by material from a solar storm of this magnitude in the next decade, according to research by physicist Pete Riley published in the journal Space Weather. So it's not a question of if we'll be hit; it's only a question of when. And unfortunately, the world is woefully unprepared to deal with the consequences.