Advances in miniaturization have made smaller spacecraft more plausible. The Starship Enterprise of “Star Trek” is roughly the size of an ocean liner. In real life, proponents of interstellar spaceflight are dreaming of something more like the Cellphone Enterprise: a small, speedy spacecraft, crammed with nanotechnology and capable of beaming snapshots back home.

Perhaps the first probe would be the size of a sewing needle, says Paul Gilster, author of “Centauri Dreams” and of a Web site devoted to interstellar travel. The needle probe might be capable of carrying out elaborate auto-assembly instructions, building a research station using natural resources on that distant world. The spacecraft would be like the seed of a machine, rather than the machine itself.

“I’m certain we’re going at some point,” Gilster said. “We’re not only going to get probes out there, we’re going to get people out there someday. It might take centuries for the people.”