Some meandering thoughts on:
A Simple Model of Grabby Aliens, Robin Hanson, Daniel Martin, Calvin McCarter, Jonathan Paulson
Disclaimer: this is some meandering thoughts and only vaguely about the paper. (Really I should say this before I say anything)
This was a very interesting paper. I myself have often that it was curious that the ratio of earth's age to the universes was so small and that life has been present on Earth basically since the beginning. I think Age of Earth - Age of Life is only provably smaller than 200 million but absence of evidence is not evidence of absence. I guess the reason those two facts surprise me is because of the opposite facts that I am very young in the context of history, humans are very young in the context of mammals and mammals are very young in the context of life.
I'm not sure I totally understand the thesis of the paper or the supporting model but it's something like: A universe in which many alien civilizations evolve vaguely analogously to us and then develop the ability to travel across space at some fraction of the speed of light settling planets on their way in an externally visible way eventually filling most of the universe's volume is consistent with the available evidence. The available evidence being a universe which hasn't been observably changed by intelligences and a look back at some of the difficult things life and humans had to overcome to get to our present state of development.
They have a model which takes in parameters like number of planets per unit volume, the number of 'hard steps' life has to overcome to become multi-planetary and the fraction of the speed of light civilizations eventually expand at.
What I love about this paper is this vision of a future where the best way to understand the large scale phenomena in the universe isn't by understanding physics but by understanding the intelligent civilizations which fill its volume. Already it seems more productive to analyze the behavior of humans to predict what will happen here on Earth than physical phenomena. Though maybe that's an illusion caused by me just being much more interested in people than other things.
The predictions of the paper seem somehow quasi-religious. And I don't mean this as an insult. I remember once watching a talk by a futurologist science fiction writer type (I really wish I could find and link it. My apologies) who said something like 'The singularity (in the sense of evil AI?) as a belief is isomorphic to some christian eschatology so can be dismissed outright' and I remember thinking it was such a lazy dismissal. At the end of the day, at the end of the world, it will be the case that humanity will increase in power until we barely recognize it, it will destroy itself, or it will reach some sort of steady state. And maybe the sober minds will say 2100 will be like today but 50% better or worse. But somehow that doesn't seem more likely than the extreme outcomes to me.
I had a thought recently that religion is all the most important questions which one can never answer. (Actually religion is probably more of a practice and a community and not constant rumination on the end of oneself and the world. But at this point I wouldn't really know) I was discussing aliens with a friend and he said that ultimately the existence of aliens wasn't a scientific question because one couldn't test it with experiments. That perspective made me so sad. We can still have discussions and weigh evidence in matters we'll never be able to conclusively settle. We'll just probably be wrong.