OUR FIRST LINE OF DEFENSE: I haven’t read the book in question, but this review makes Timothy Ferris’s Seeing in the Dark: How Backyard Stargazers Are Probing Deep Space, and Guarding Earth from Interplanetary Peril sound pretty cool. And it’s certainly true that amateur astronomers (whose operations are in some ways as sophisticated as the professionals’) are the ones most likely to spot some dangers, such as an asteroid or comet aimed at Earth.

If Ferris makes one point, he makes it again and again: Don’t overlook “the backyard stargazer who searches with a telescope for previously undiscovered asteroids and comets.”

These thought adventurers gazing up at the night sky from backyards all over the world are “simultaneously engaged in two missions — a study of our origins and a reconnaissance that just might bear on our survival.”

There have even been some efforts to harness these amateurs in a more organized fashion, via prizes for discovering earth-crossing asteroids. As individuals get richer, and as technology extends their capabilities, informal groups of interested amateurs are likely to become the main means of addressing some important problems. In fact, as this example makes clear, they already have.