Interstellar Galactic Federations and Empires not withstanding, Einstein’s Special Theory of Relativty still rules.
However, Paul Gilster posts on his blog Centauri Dreams that below light speed colonization of the galaxy can have a normal, more organic method of colonizing the galaxy by human, or alien intelligences:
Imagine a future in which we manage to reach average speeds in the area of one percent of the speed of light. That would make for a 437-year one-way trip to the Alpha Centauri system, too long for anything manned other than generation ships or missions with crews in some kind of suspended animation. Although 0.01c is well beyond our current capabilities, there is absolutely nothing in the laws of physics that would prevent our attaining such velocities, assuming we can find the energy source to drive the vehicle. And because it seems an achievable goal, it’s worth looking at what we might do with space probes and advanced robotics that can move at such velocities.
How, in other words, would a spacefaring culture use artificial intelligence and fast probes to move beyond its parent solar system? John Mathews ( Pennyslvania State) looks at the issue in a new paper, with a nod to the work of John von Neumann on self-reproducing automata and the subsequent thoughts of Ronald Bracewell and Frank Tipler on how, even at comparatively slow (in interstellar terms) speeds like 0.01c, such a culture could spread through the galaxy. There are implications for our own future here, but also for SETI, for Mathews uses the projected human future as a model for what any civilization might accomplish. Assume the same model of incremental expansion through robotics and you may uncover the right wavelengths to use in observing an extraterrestrial civilization, if indeed one exists.
Image: The spiral galaxy M101. If civilizations choose to build them, self-reproducing robotic probes could theoretically expand across the entire disk within a scant million years, at speeds well below the speed of light. Credit: STScI.
But let’s leave SETI aside for a moment and ponder robotics and intelligent probes. Building on recent work by James and Gregory Benford on interstellar beacons, Mathews likewise wants to figure out the most efficient and cost-effective way of exploring nearby space, one that assumes exploration like this will proceed using only a small fraction of the Gross Planetary Product (GPP) and (much later) the Gross Solar System Product (GSSP). The solution, given constraints of speed and efficiency, is the autonomous, self-replicating robot, early versions of which we have already sent into the cosmos in the form of probes like our Pioneers and Voyagers.
The role of self-replicating probes — Mathews calls them Explorer roBots, or EBs — is to propagate throughout the Solar System and, eventually, the nearby galaxy, finding the resources needed to produce the next generation of automata and looking for life. Close to home, we can imagine such robotic probes moving at far less than 0.01c as they set out to do something targeted manned missions can’t accomplish, reaching and cataloging vast numbers of outer system objects. Consider that the main asteroid belt is currently known to house over 500,000 objects, while the Kuiper Belt is currently thought to have more than 70,000 100-kilometer and larger objects. Move into the Oort and we’re talking about billions of potential targets.
A wave of self-reproducing probes (with necessary constraints to avoid uninhibited growth) could range freely through these vast domains. Mathews projects forward not so many years to find that ongoing trends in computerization will allow for the gradual development of the self-sufficient robots we need, capable of using the resources they encounter on their journeys and communicating with a growing network in which observations are pooled. Thus the growth toward a truly interstellar capability is organic, moving inexorably outward through robotics of ever-increasing proficiency, a wave of exploration that does not need continual monitoring from humans who are, in any case, gradually going to be far enough away to make two-way communications less and less useful.
Paul calls robotic networks “organic” in the way they might grow, but there is a commenter on the post who disagrees with it and I might agree with that.
But that doesn’t discount a more “cybernetic” approach in which the combination of machine with organic technology is the more “natural” extension or evolution of intelligent lifeforms.
I would look for rigidly constructed organic molecular structures in the interstellar medium as materials for Bracewell Probes.