Probing von Neumann Expansion - by centauri_dreams
be aware that it’s out there – it’s getting good reviews, and given the impact of this remarkable figure on everything from programmable computers to game theory and the interstellar dispersion of civilizations, it’s a book you’ll at least want to stick on your reference list.
It’s a good time for this book to come out, because von Neumann isn’t exactly in the spotlight these days. In a review in Science, Dov Greenbaum and Mark Gerstein note that he seems to have dropped out of public view: Most of those exploring this space have been what Milan Ćirković calls ‘contact pessimists,’ who point out that if von Neumann probes could visit all stars with habitable planets in an entire galaxy, and do this within a small fraction of the galaxy’s age, their existence should be obvious. A more subtle school of thought holds that 1) dispersion need not be uniform and 2) a von Neumann probe may already be in our own Solar System, much less others, for we have only begun to explore deep space.
Either way, we have a method to move human technologies out into the galaxy once our engineering is up to the challenge – the physics behind the project do not preclude this. So let’s imagine that we or some other civilization reach a stage in which we can build von Neumann probes and set them on their journeys. Matloff develops a conservative estimate of the expansion rate of a civilization using such probes.
This approach is only an approximation; not all stellar systems will be suitable for occupation by von Neumann probes, and some close stellar encounters will be repeated. But it does indicate that not many long-lived space-faring civilizations that deploy von Neumann probes are required to occupy the galaxy.