(December 16, 2011 at 4:29 pm)TheDarkestOfAngels Wrote: I find it difficult to swallow that this universe is fine-tuned for life when almost all of it is uninhabitable to known life.
Fine tuning is not talking how much of our universe happen to be habitable to known life given the current circumstances. It is talking about what range of values the fundamental dimensionaless constants of the laws of physics must fall into in order for it to even be theoretically possible for known life to exist at all at anywhere, during any part of universe's existence.
The behavior of the laws of physics are governed by a number of fundamental dimensionless constants - coupling constant of electromegnetic interaction, gravitational coupling constant, strong force coupling constant, and proton electron mass ratio constant. The value of these constants can be measured, but they can not be derived from any known fundamental principle. So why they are the value they are is not known. Although repeated experiments in our universe has never shown that these values has, will, or can change, or can be different from one place to another, There is no known principle that says they can't.
So one school of thought is these constants in fact are not constrained to have the value we observe. Working out the consequences of these constants having a different value reveals that any one of them really has to change only very little for it to be impossible, even theoretically, for known life to ever exist anywhere in the universe.
The fine tuning question deals with the statistical unlikelihood of several theoretically freely variable physical properties to all assume precisely the right value to make life possible.
Of course one could immediately challenge whether these fundamental constants are in fact not constrained by some even deeper principle. Perhaps these values has to be the values they are. In which case there is no issue of fine, or even coarse, tuning of any kind. It is the way it is because it can't be any other way. We just haven't found out why yet.
