Extraterrestrial Life
Having now officially completed my astronomy course (i.e. received final grades and all) I can now post the second and final dissertation I wrote for the course (I posted the first one some months ago). Given the theme, this time it was much harder for me to ‘keep the philosophy at bay’ and to write a proper scientific review. Together with theoretical cosmology (and in some ways even more than that) astrobiology is a field which is very much open to cooperation between scientists and philosophers. So again, I hope someone might find it interesting.
Fabio Cunctator
Yes, this looks very interesting, a topic of study for many years. I will be giving over about half a chapter to the Fermi Paradox, Great Silence and Doomsday Argument in the book that I am currently working on, so this is very useful. Given your interest in religion too, have you seen Steven Dick’s edited volume Many Worlds: The New Universe, Extraterrestrial Life and the Theological Implications? It has some good articles.
Thanks for the really enjoyable read, especially since I’ve had very little exposure to astrobiology.
I’m still a bit confused by the connection drawn between the (weak) anthropic principle and the probability of intelligent life. It seems like there are two separate issues here.
First, in the context of actually finding life in our region of space (i.e. life located within ~ 1 million light years), the anthropic principle doesn’t seem as important. Just take the physical parameters of the universe as a given and estimate the probability of intelligent life arising (which, granted, is nearly impossible as you point out in the paper).
The second issue is different: In the multiverse/Universe, what is the probability of life arising? In this case, one has to take into account why the parameters are the way they are in our Universe, and what values they may take on in separate universes. Thus, this more general question does not concern itself with the “practical” question of whether or not there is life in our local Universe (whose parameters have been measured and should be taken as a given), but considers the existence of life in the multiverse or a hypothetical ensemble of universes like our own (in order to calculate the probability of intelligent life arising in our Universe).
Grad Student,
yes I don’t think there is really any connection either. I do not find anything controversial in the use of a weak anthropic principle even though it could be argued that the anthropic lanscape *includes* habitable zones. Which means that there can be regions of the universe which humans cannot inhabit (non-HZ) but which could in principle give rise to intelligent observers (which is why the term *anthropic* is wrong).
As I say in that essay, ultimately the problem is simple: we do not have a clear and secure enough definition of ‘life’ and of ‘intelligence’ (yet?) to assure astrobiology to be an ‘exact science’ and to allow us to discriminate once and for all what set of cosmological parameters can or cannot allow the emergence of observers.