We’ve all learned the value of covering up or turning away when we sneeze over the last year or so. Water droplets can carry viruses, so a sneeze can be a big problem.

Fortunately for us, the Sun usually turns away when it sneezes — but not always. The sneezes that aim at Earth can cause big problems — perhaps even catastrophic ones.

A solar “sneeze” is known as a coronal mass ejection. It occurs when there’s a big magnetic storm on the surface of the Sun. The storm can trigger an outburst of charged particles — billions of tons of them. The cloud of particles races through the solar system at millions of miles per hour.

Most of the time, such clouds are directed away from Earth. Sometimes, though, they take dead aim at our planet. When they hit, they cause brilliant displays of the northern and southern lights. More ominously, they can damage or destroy satellites, disrupt communications, and knock out power grids.

An event in 1859 — the most powerful yet seen — knocked out most telegraph service. Another, in 1921, burned down buildings and disrupted train service; more about that tomorrow.

We haven’t been hit by anything that big since then. But it’s almost certain that we will be — whether it’s this year or a hundred years from now. And the effects could be devastating. Powerful impacts could destroy much of the power grid, leaving parts of the U.S. and other countries in the dark for months — blacked out by a “sneeze” from the Sun.

Script by Damond Benningfield