Our moon was born too small to harbor life. It came from the collision of a Mars-sized world into the primordial Earth. From that colossal crunch spun a disk of rocks that condensed into a satellite.

The moon's closeness is a huge advantage: To make it habitable, we would first have to bombard it with water-ice comets, a tricky endeavor best attempted with the many resources waiting on and near Earth.

Terraforming our moon will take many decades and vast abilities. Before we can begin, we'll have to master the resources of our solar system - especially transporting raw masses over interplanetary distances.

This was the 1940s; there was no television. It was a different age - it was not swamped by media; it was swamped by reality, and storytelling was a very big art where I came from.

Will searching for distant messages work? Is there intelligent life out there? The SETI effort is worth continuing, but our common-sense beacons approach seems more likely to answer those questions.

Around 1930, a small new phenomenon arose in Depression-ridden America, spawned out of the letter columns in science fiction magazines: fandom.