Grabby aliens theory of Robin Hanson predicts that the nearest grabby aliens are 1 billion light years away but strongly depends on the habitability of red dwarfs (https://grabbyaliens.com/paper).
In this post, the author combines anthropic and Fermi, that is, the idea that we live in the universe with the highest concentration of aliens, limited by their invisibility, and get an estimation of around 100 “potentially visible” civilizations per observable universe, which at first approximation gives 1 billion ly distance between them.
“That civilisations appear once every 10power20 stars implies that there should be about 100 civilisations in the observable universe.”
This is approximately the same as what is predicted by Grabby Aliens by Hanson.
So the question is why the two theories give similar results.
Basically, it is because they both have the same structure: first, anthropic argument, and second update based on Fermi.
But anthropic arguments in them are different. In Hanson’s Grabby Aliens case, it is our early location in time and in the second case, it is Self-Indication Assumption, which implies that we live in the universe with the highest spatial concentration of aliens (with some caveats).
The second part of the argument in both cases is basically based on the idea of grabbiness: quick space exploration with near-light speed and preventing of earth-like civilizations’ existence by grabby aliens.
Grabby aliens theory of Robin Hanson predicts that the nearest grabby aliens are 1 billion light years away but strongly depends on the habitability of red dwarfs (https://grabbyaliens.com/paper).
In this post, the author combines anthropic and Fermi, that is, the idea that we live in the universe with the highest concentration of aliens, limited by their invisibility, and get an estimation of around 100 “potentially visible” civilizations per observable universe, which at first approximation gives 1 billion ly distance between them.
This is approximately the same as what is predicted by Grabby Aliens by Hanson.
So the question is why the two theories give similar results.
Basically, it is because they both have the same structure: first, anthropic argument, and second update based on Fermi.
But anthropic arguments in them are different. In Hanson’s Grabby Aliens case, it is our early location in time and in the second case, it is Self-Indication Assumption, which implies that we live in the universe with the highest spatial concentration of aliens (with some caveats).
The second part of the argument in both cases is basically based on the idea of grabbiness: quick space exploration with near-light speed and preventing of earth-like civilizations’ existence by grabby aliens.