Original post here. The following belief is probably one of my weirdest ones but I'm confident in it and would like to test it. Still it's unlikely that we'll have evidence for or against in my own lifetime. Consequently I went to Longbets.org to post my prediction but learned only at the end that there's a fifty dollar publishing fee. No deal.
So here's what I was going to enter.
SUMMARY: By the time we have surveyed the surfaces of 1% of asteroids and comets in the Solar System, we will have found definitive evidence of extrasolar replicators, von Neumann probes or otherwise.
SUPPORTING ARGUMENTS: The argument has been made by Tipler that the absence of von Neumann probes is in fact much more damning to the prospect of extrasolar life than the absence of signals as observed by Fermi. That we, in the infancy of space exploration, have as yet an absence of evidence of von Neumann probes is certainly not evidence of absence; this is rather like a Roman orator having claimed that there are definitely no continents besides Europe, Africa and Asia. In fact there are good reasons why the Earth's surface would not be a good place for space-traveling replicators, the economics of gravity wells among them. Using the self-indication assumption and the explosion of our knowledge about nearby planetary systems, it is becoming increasingly unreasonable to suppose that there are no other replicators (planet-bound or otherwise). This means that if space-borne replicators are possible, they are probable, and we should look for evidence associated with comets and asteroids. I make this prediction contingent on exploration because I'm not nearly as confident about when that will happen. I do appreciate that 1% is still a massive number of bodies, so I don't realistically expect this to occur within the next two centuries.
[Added later: Japan is about to test solar sail technology which is one passive way that replicators could diffuse. The design is engineered to get to Venus, on the way accelerating to 100 m/s over six months, which translates to a Sun-to-Alpha Centauri crossing in a little over five millennia, a reasonable scale even for biological diffusion on Earth.]