Long-term thinking, so unusual in our era, was once commonplace, as the centuries-long construction of the great cathedrals of Europe reminds us. Or how about the remarkable Ise Shrine, a Shinto temple in Japan whose wooden structure is periodically rebuilt, and has been every twenty years for the last thousand. So the idea of constructing a star probe whose mission might last a century — or a thousand years — is not inconceivable, as long as we view it as a gift to the human future as much as a mission whose end we will see.
But projects with a focus on ‘the long now,’ as Stewart Brand calls this multilayered view of time, can be found even in our own frenetic culture. Brand’s book The Clock of the Long Now describes Danny Hillis’ idea of a timepiece that will last for ten thousand years, and the Long Now Foundation envisions a 10,000-year library along the same lines.
The most recent time-stretching project to come to my attention is the Deccan College dictionary of Sanskrit. Working in Pune, India the project has taken 55 years to get through just half of the entries in the first letter of the Sanskrit alphabet. No one knows how many volumes the dictionary will take, or how many decades (centuries?) will be required to complete it, but the work is invaluable to scholars because Sanskrit is the great scholarly language of the Subcontinent, with core works dating back to the 2nd Century BC in areas as diverse as medicine, philosophy and mythology. Twenty of the scholars working on the dictionary have already retired.
Now translate this into our idea of a robotic mission to another star. Voyager 2 took 12 years to reach Neptune, which is roughly thirty times the distance between the Earth and the Sun (30 AU). The nearest star, Proxima Centauri, is 260,000 AU. Voyager 2 is traveling at 3.3 AU per year as it moves toward the heliopause — you can see where the math is leading us. Even with huge increases in speed, getting there in mere hundreds of years, much less in decades, is a task that all but overwhelms the imagination.
At JPL last year, Hoppy Price (who studies solar sail technologies for future missions) told me that he thought our first interstellar probes might well take several centuries to reach their target. That will mean one generation of scientists handing off the probe to the next, and they to the one after. Do we have the discipline to make that kind of commitment to knowledge, and will we take a chance on such a mission when the technology becomes available to launch it? For that matter, what do we consider an acceptable time-frame? Some scientists say we’ll launch when the travel time to the nearest star can be kept within the lifetime of a scientist working on the project. Perhaps that’s a reasonable constraint, but the betting here is that we’ll put a robotic probe out there sooner than that.
PS: Voyager 2 is not, in any case, headed toward Alpha Centauri. In 296,000 years, it will drift into the neighborhood of Sirius. As for Voyager I, it will approach to within 1.6 light years of AC+79 3888, a star in the constellation of Camelopardalis, in some 40,000 years.
