regardless of what speed they traveled while moving between stars
Adding to my other reply to your other comment I just made, let me just clarify that the model I’m working with is the “fast colonization” model from 25:20 of this Stuart Armstrong FHI talk, in which von Nuemann probes are sent directly from their origin solar system to each other galaxy, rather than hopping from galaxy to galaxy (as in the “slow colonization” model used by Sagan/Newman/Fogg/Hanson according to Stuart’s slide).
So if >0.99c probes are possible, then I think the hypothesis I described is at least plausible, since civilizations indeed wouldn’t see other expanding civilizations until those civilizations reached them.
Adding to my other reply to your other comment I just made, let me just clarify that the model I’m working with is the “fast colonization” model from 25:20 of this Stuart Armstrong FHI talk, in which von Nuemann probes are sent directly from their origin solar system to each other galaxy, rather than hopping from galaxy to galaxy (as in the “slow colonization” model used by Sagan/Newman/Fogg/Hanson according to Stuart’s slide).
So if >0.99c probes are possible, then I think the hypothesis I described is at least plausible, since civilizations indeed wouldn’t see other expanding civilizations until those civilizations reached them.