It's happened before and it could happen again.
Roughly 2,700 years ago, an unusually powerful solar storm swept past the Earth, scientists announced in a new study. Though it had little to no impact on people in that long ago, pre-industrial and pre-technological world, such an event today would cause widespread power outages along with potentially disastrous communication and navigation failures.
The solar storm, which was in 660 B.C., was about 10 times stronger than any known event in the past 70 years, study lead author Raimund Muscheler said.
A solar storm of that strength would be "a threat to modern society in terms of communication and navigation systems, space technologies and commercial aircraft operations,” the study said.
Scientists studied ancient ice in Greenland to uncover clues about previous solar storms. Looking at an ice core that dated as far back as 100,000 years, researchers found radioactive isotopes that indicated a very powerful solar storm 2,700 years ago.