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AllanCrossman comments on The Sin of Underconfidence - Less Wrong
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I don't think this is good enough. There seem to be several physical constants that - if they had been slightly different - would have made any sort of life unlikely.
That part can be deproblematized (if you will forgive the nonce word) by the anthropic principle: if the universe were unsuited for life, there would be no life to notice that and remark upon it.
True. But since a universe unsuitable for life seems overwhelmingly the more probable situation, we can still ask why it isn't so.
(My own feeling is that the problem has to be resolved by either "God" or "a multiverse". The idea that there's precisely one universe and it just happens to have the conditions for life seems extraordinary.)
My understanding (I'd have to dig out references) is that the fine tuning may not be as fine as generally believed. Ah, the wikipedia page on the argument has some references on this: http://en.wikipedia.org/wiki/Fine-tuned_Universe#Disputes_on_the_existence_of_fine-tuning
In addition to the anthropic type arguments, some theoretical work seems to suggest that the fine tuning isn't. ie, that we don't even need to invoke anthropic reasoning too strongly. Heck, supposedly one can even have stars in a universe with no weak interaction at all.
So it may very well be that, even without appealing to anthropic style reasoning in multiverses (which I'm not actually opposed to, but there's stuff there that I still don't understand. Born stats, apparent breakdown of the Aumann Agreement Theorem, etc... so too easy to get stuff wrong) anyways, even without that, it may well be that the fine tuning stuff can be refuted by simply pointing out "looking at the actual physics, the tuning is rather less fine than claimed."
I agree, but the anthropic principle has always seemed like a bit of cheat -- an explanation that really isn't much of an explanation at all.
I don't accept that form of the anthropic principle. I am on a planet, even though planets make up only a tiny portion of the universe, because there's (almost) nobody not on a planet to remark on it. The anthropic principle says that you will be where a person is. However, it can't change the universe. The laws of physics aren't going to rewrite themselves just because there was nobody there to see them.
That being said, if you combine this with multiple universes, it works. The multiverse is obviously suitable for life somewhere. We are going to end up in one of those places.
Even in the case of a single infinite universe, the anthropic principle does help - it means that any arbitrarily low success rate for forming life is equally acceptable, so long as it is not identically zero.
In that case, it would look like the universal constants don't support life at all, but you somehow managed to get lucky and survive anyway, rather than the universal constants appearing to be fine-tuned.
If the "universal constants" are different in different areas, then it would basically be a multiverse.
As i understand it, it's possible to pick out even better constants than what we have. For instance, having a fine structure constant between 6 and 7 would cause all atoms with at least 6 protons to be chemically identical to carbon due to 'atomic collapse'. That would probably help life along noticeably.
As things stand, we're pretty marginal. There's a whole lot of not-life out there.
It would probably also completely screw up the triple-alpha process, so that much less carbon will be produced in stars -- assuming stars would be possible in that situation in the first place.
Would that help really? Most life requires all of CHNOPS. And pretty much all complex life requires at least a few heavier elements, especially iron, copper, silicon, selenium, chlorine, magnesium, zinc, and iodine. Life won't do much if one can't get any elements heavier than carbon.
It obviously wouldn't be life exactly as we know it, no! I'm pretty confident that if you replaced all the elements heavier than carbon with carbon, some form of life would be able to emerge. Carbon is where the complexity comes from - everything else is optimization.
Seriously, that's the most blatant case of the failure of imagination fallacy I've seen since I stopped cruising creationist discussion boards.
I'm substantially less convinced. While carbon is the main cause of complexity, that's still carbon with other elements. Your options in this hypothetical are hydrogen, helium, lithium, beryllium, boron and carbon and that's it. Helium is effectively out (I think, I don't know enough to be that confident that basic bonding behavior will be that similar when you've drastically altered the fine structure constant.) The chemistry for that set isn't nearly as complicated as that involving full CHNOPS. And the relevant question isn't "can life form with these elements" but rather "how likely is it?" and "how likely is complex life to form"?
As I understand it, the vast majority of constants are worse than what we have now. You might be able to find something better, but if this was just chance, we're very lucky as it is. Since you're not usually that lucky, it probably wasn't chance.