I gave up on dreams of interstellar travel a long time ago. I outgrew them, just as I outgrew the Tooth Fairy and the Easter Bunny. And then last month, along came this paper by Philip Lubin from the University of California at Santa Barbara, claiming that interstellar travel is feasible with existing technology.
Lubin's scheme involves powerful ground-based lasers blasting a sail connected to a small wafer of computer chips and sensors. He argues that such a device could accelerate to 1/4 of the speed of light, reaching the nearest start in only 20 years. It's a remarkable idea. Shortly afterwards, the billionaire Yuri Milner announced the "Starshot Project" to build just such an interstellar probe. (This was no coincidence -- Lubin is on the board of the project). If I were experimentally inclined (which I'm not) and 20 years younger (also not), I think this is what I'd want to be working on today. What could be more exciting?
Of course this idea was anticipated by science fiction writers -- it plays the central role in the recent David Brin novel, Existence. (SPOILER WARNING)
In Brin's novel, alien civilizations across the galaxy have downloaded their personalities into small space probes and hurled them across the galaxy using enormous lasers. But in Brin's conception, these probes function very much like viruses -- their first goal when they encounter a new civilization is to convince that civilization to make and shoot into space more duplicates of themselves, even if the enormous effort actually destroys the host civilization.
But to get back to the original point, maybe, as Lubin suggests, we've simply been thinking about interstellar travel all wrong. Huge chemical rockets crawling to the stars might appear just as silly to our descendants as an ancient galley trying to row across the Atlantic. We'll just have to wait and see where the Starshot Project leads. But I wish them well.