A relatively straightforward speculative article. The Physics of Extra-Terrestrial Civilizations
A couple of quibbles. When you read old speculative articles they often seems a bit quaint, as the then-current latest technology is given more emphasis than later seems warranted.
Paul Davies speculates that a space-faring civilization could use nanotechnology to build miniature probes to explore the galaxy, perhaps no bigger than your palm. Davies says, “The tiny probes I’m talking about will be so inconspicuous that it’s no surprise that we haven’t come across one. It’s not the sort of thing that you’re going to trip over in your back yard. So if that is the way technology develops, namely, smaller, faster, cheaper and if other civilizations have gone this route, then we could be surrounded by surveillance devices.”
Simply put - smaller things tend to be shorter lived. Patterns printed on silicon smear over time (very quickly in the time frames of the article), and cosmic rays zap through smashing very small things. Assuming no radical changes in the physics of materials, to make a small probe long-lived you would have to make the design either enormously redundant, self-repairing, or self-reproducing.
Furthermore, the development of biotechnology has opened entirely new possibilities. These probes may act as life-forms, reproducing their genetic information, mutating and evolving at each stage of reproduction to enhance their capabilities, and may have artificial intelligence to accelerate their search.
This sounds a lot like biology - in fact I do not see a distinction - this is biology. In very short time (in these time scales) we will have complete mastery over the design and construction of new carbon and DNA based living things. Since we are able to do this as a “Type 0” civilization, surely the older civilizations will be at least as capable.
Put differently - perhaps we are the probes, or the products of probes. Of course, non-carbon based life forms may be far more suitable - though we are not nearly far enough along to make that sort of judgement.
Then of course there is the question of why. Why would an advanced civilization choose to expand? Is expansion a purpose in itself? Should it be?
This leads us to the speculation that some advanced civilizations will largely lose interest in expansion at some point. Since a nearby expansion-oriented civilization could pose a threat, we have a basis for conflict. Conflict on this scale could absorb a great deal of energy that might otherwise go into expansion. Perhaps some civilizations cannot coexist peacefully with others on any basis.
Von Neumann probes need to be smart and adaptable. Over the scale of galaxy-wide space stretched over thousands or millions of years, the chance of mutation has to be considered. Could these probes turn out to be a threat to the civilization that originated them? Could one civilization re-purpose the probes sent out by another? Could probes prove a threat or provocative to other civilizations - even accidentally?
This all starts to look something like an ecosystem. Some may choose to remain hidden. Some may choose strong defenses. Some may choose flight. Some may choose aggression.
Perhaps enlightened older civilizations will all learn to get along in harmony - we all like this assumption, but it is an assumption. Perhaps this is not always or often possible. We simply do not know and have no basis to judge.
Perhaps sending out a massive wave of probes is not a good idea. If probes are sent out, stealth is probably a good idea. If there are probes here or nearby, we should not expect to find them easily.