I agree it seems plausible SIA favours panspermia, though my rough guess is that doesn’t change the model too much.
Conditioning on panspermia happening (and so the majority of GCs arriving through panspermia) then the number of hard steps n in the model can just be seen as the number of post-panspermia steps.
I then think this doesn’t change the distribution of ICs or GCs spatially if (1) the post-panspermia steps are sufficiently hard (2) a GC can quickly expand to contain the volume over which its panspermia of origin occurred. The hardness assumption implies that GC origin times will be sufficiently spread out for a single to GC to prevent any prevent any planets with m<n step completions of life from becoming GCs.
Yes, if “GC can quickly expand to contain the volume over which its panspermia of origin occurred”, when we return to the model of intergalactic grabby aliens. But if the panspermia volume is relatively large and the speed of colonisation is relatively small, for each such volume there will be several civilizations which appear almost simultaneously. They will have age difference around 1 million years, the distance will be less than 100 kyl and they will arrive soon.
We will encounter such panspermia-brothers long before we meet grabby aliens from other remote galaxies.
I agree it seems plausible SIA favours panspermia, though my rough guess is that doesn’t change the model too much.
Conditioning on panspermia happening (and so the majority of GCs arriving through panspermia) then the number of hard steps n in the model can just be seen as the number of post-panspermia steps.
I then think this doesn’t change the distribution of ICs or GCs spatially if (1) the post-panspermia steps are sufficiently hard (2) a GC can quickly expand to contain the volume over which its panspermia of origin occurred. The hardness assumption implies that GC origin times will be sufficiently spread out for a single to GC to prevent any prevent any planets with m<n step completions of life from becoming GCs.
Yes, if “GC can quickly expand to contain the volume over which its panspermia of origin occurred”, when we return to the model of intergalactic grabby aliens. But if the panspermia volume is relatively large and the speed of colonisation is relatively small, for each such volume there will be several civilizations which appear almost simultaneously. They will have age difference around 1 million years, the distance will be less than 100 kyl and they will arrive soon.
We will encounter such panspermia-brothers long before we meet grabby aliens from other remote galaxies.