Sten Odenwald has had lots of practice educating novices about astronomy. The Harvard Ph.D. handles public outreach for NASA’s IMAGE satellite program and has written for Sky & Telescope and Astronomy magazines, as well as for the now-defunct Horizon section of the Washington Post. But he is perhaps best known for his Web site,, whose “Ask the Astronomer” section has received thousands of queries. In 1998, Odenwald culled the 365 best questions for The Astronomy Cafe, a book that has subsequently been published in several languages, including Japanese and Chinese.

Odenwald’s latest astronomical contribution is The 23rd Cycle: Learning to Live With a Stormy Star, which explains how storms on the sun can wreak havoc here on earth.

Appropriately enough, Columbia University Press released Odenwald’s book in February, at the peak of our solar system’s current sun-storm cycle. Sun storms wax and wane in periods that tend to last roughly 11 years; the current one is the 23rd since astronomers first noticed the cyclical nature of these disturbances in the mid-1700s.

Three types of solar events can cause problems for the Earth. Small-scale solar flare-ups produce powerful bursts of X-rays that zoom toward the earth at the speed of light; when they arrive, 8.5 minutes later, they can disrupt radio signals. Solar proton events travel more slowly but produce hailstorms of particles that can damage satellites. The third—and potentially most serious—type of event is coronal mass ejections, which can spew billions of tons of plasma into space. Because coronal mass ejections are so enormous, they tend to significantly interfere with the Earth’s magnetic fields.

Not every consequence is bad; auroras, such as the northern lights, are one gorgeous result of coronal mass ejections. And the earth’s atmosphere—to our good fortune—acts as a protective blanket, preventing these storms from causing any direct damage to humans and other life forms. (You’re likelier to pick up radiation from eating bananas or handling clay, Odenwald notes.) The real danger is to the advanced technologies—from communications networks to the electric power grid—that define our society. If Odenwald is correct, these complex systems may be at greater risk from unseen bombardments than most of us realize.

The most dramatic illustration of Odenwald’s thesis came in 1989, when a sun storm caused such a powerful magnetic disturbance in Quebec that the region’s entire power grid experienced a cascade of problems that culminated in a total blackout. The dominoes fell so fast that no one could have done anything about it; from start to finish, the system went from hunky-dory to total darkness within a mere 90 seconds. Fortunately, the Quebec outage didn’t spread widely, but given how intertwined North America’s regional power systems are, Odenwald says, a single, well-placed sun storm could plunge wide swaths of the United States into a blackout. And, he adds, getting out wouldn’t be easy. A really bad surge could fry more transformers than there are ready spares to replace them—and if new transformers had to be built, he warns, electric-power shortages could linger for months.

Drawing direct cause-and-effect connections between sun storms and technological failures requires investigative legwork; indeed, Odenwald debunked fallacies about a number of adverse incidents that initially appeared to have been caused by sun storms. Still, Odenwald says, “Once I started getting into the numbers—the satellites killed and pagers shut down and shortwave blackouts—I realized it was a wild and woolly story. It had very human anecdotes.

“As [an astronomer], you usually don’t think about the things you’re studying having an immediate impact—something that can sneak up and clean your clock.” —Louis Jacobson