David, would you agree that the discovery of the existence of sentient life in our galaxy would be damning to the theory of an old earth/universe?

In particular, I am thinking of the Fermi Paradox (not sure how that relates to the puddle analogy).

Thanks!
nedbrek | Homepage | 07.03.08 - 10:13 am | #

Ned,

I would not agree. Now, I don't believe in other sentient life in our galaxy. Still, one could easily imagine that even with an old universe we have not encountered any because:

1) Nobody knows about us. We haven't been sending out radio signals for even 100 years yet, and the galaxy is about 100,000 lightyears across.

2) Even technologies much more advanced than ours may not have solved, or survived long enough to solve, the technical, political, and cost problems that would be associated with traveling hundreds or thousands of lightyears. And if some did, they would then have to pick us from a large number of places to visit.
heddle | 07.04.08 - 11:29 am | #

Do you guys see any theological reasons that would prevent sentient life out there?
Mike R. | 07.05.08 - 11:11 am | #

I find the implications of fine tuning absolutely fascinating, and I learn a little more every time you post about it, but it still seems to be based on the flimsiest of foundations. At it's core it seems to be a probability argument; the 'something of a razor's edge' that was referred to in the post.

We don't know what the probability is of any of the fine tuned constants being any particular value. We don't know if they can have any other value, what the range of values for each are, and we have no evidence of them varying in our own universe. If they are variable, we don't know if or how altering them may change the equation or other variables.

We don't know how life on Earth appeared. We seem to know that life is most likely on planetary bodies, and we've surveyed roughly half a solar system, if I'm generous.

Our own theories for the physics of this universe conflict or are incomplete (if what I've gleaned about the cosmological constant problem is correct). The latest thinking, I believe, is that the majority of the stuff in the universe is made up of dark matter/dare energy, about which we know little.

Without knowing anything about the variability of these constants, we have no clue whether they are on a razor's edge or not. With an incomplete understanding of our own universe and with a sample size of 1, saying much about what can and cannot be in another universe with different constants and possibly natural laws is quite a stretch. "Any life requires heavy elements which require stars" appears to be true for universes with our exact same physical laws.

I disagree, because of the probability problems, that anything's on a 'razor's edge', but you are still right in a way: it's virtually undisputed that cosmological fine tuning is, I don't know if I'd say 'serious problem', but is a subject that is definitely taken seriously. There seems to be quotes from all the physicists a layman might know concerning it, and although they skip the probability thing that causes me trouble, they address possible solutions which would imply that there's a phenomenon needing an explanation. The only explanation I've heard referred to Bayes theory as far as the probability issue, but it is definitely not virtually undisputed that that is applicable to fine tuning.
Dave L | 07.05.08 - 11:22 pm | #

Mike R,

I can just speak for myself. I think it is hard to read the bible an not conclude than man is the center of creation. I would probably struggle with the discovery if other intelligent life.

Dave L.

The razor's edge aspect is independent of probabilities. It is a statement that if you tweak this or that constant, life could not exist. Fine tuning refers to sensitivity, not improbability. It makes no claim about the probaility of the constants. Only afterwards do people try to make metaphysical mileage from the probablilities. As I have harped about many times, IDists make exactly the wrong metaphysical argument. It is not the small probability case that points to design--no, the small probability case is exactly what anti-design multiverse theories predict. It would be the large probability (P=1)case that would be a stronger metaphysical feather in the design cap--if habitability is sensitive to the constants (and it is)and the constantns have probability one, because they come from a fundamental theory, we would be in a situation where habiltability was built into the fabric of spacetime. That would be a big plus for the IDers and a minus for the multiversers. Weirdly, The IDers continue to drone on and on about low probabilities and continue to think a fatuous and ad hoc "universal probability bound" has significance.
heddle | 07.07.08 - 8:17 am | #

"It is a statement that if you tweak this or that constant, life could not exist. Fine tuning refers to sensitivity, not improbability. It makes no claim about the probability of the constants."

That is an interesting distinction, but I've always assumed, probably mistakenly, that we are still saying some unspecified things about 'life', such as it's remarkable or unexpected. I know you've moved it back a bit and referred to the sensitivity of the formations of stars and galaxies to these constants also (which I thought you did to get past the 'we don't know what other types of life there can be' objection), but that seems to make the point easier to refute (and now I'm the one assuming that a star is 'less sensitive' than life). Who knows how many universes with different configurations have structures that are very sensitive to those particular configurations?

I guess I also don't see that it means much to say how sensitive life is to these constants if they are invariable and can't be tweaked. Every reaction is highly sensitive to it's causing action, but I've never taken that as a phenomenon requiring an explanation. Fine tuning in no way says or takes as a given, given our understanding of physics, that life is unexpected or remarkable?

Concerning your large and small probability examples, I was a little confused on why your examples only refer to the multi-verses. If there is a small probability of habitability and one universe, then that would seem to bolster the fine tuning argument. If there is a large probability and one universe, I don't see why you couldn't also say that that strengthens the ID argument, although it seems that it could equally support the naturalistic position; if this was the case, would fine tuning disappear? Are their observations or discoveries we could make that would lead you to believe that fine tuning is an illusion?

I think also implicit in this is an assumption being made by physicists that a very large number of the universes they envision with tweaked constants would essentially be structureless (to me, a gigantic assumption). If probability is truly divorced from this then of course we should expect some things in a universe to exist that are highly sensitive to the laws/constants, but that alone doesn't cause any serious problems and is not noteworthy no matter how many universes there are.
Dave L | 07.07.08 - 6:57 pm | #

David

I have a physics question for you, related to the fine-tuning argument. I have a second-hand citation for which I'd like to know if there is a primary citation to back it up.

Apparently in his 1995 book, The Unconscious Quantum: Metaphysics in Modern Physics and Cosmology, physicist Victor Stenger ran a computer simulation. He simulated putative universes where 4 basic physical constants (proton mass, electron mass, strength of the electromagnetic force, strength of the strong force) were varied by 10 orders of magnitude. In more than half of these theoretical universes, stars exist for at least a billion years. In some cases they exist for far longer (6-8 billion years).

He argues that this is long enough for planet formation, heavy element formation, etc. He argues that the notion of cosmological fine-tuning is thus much less tenable; many combinations of physical constants give universes that are theoretically capable of generating the materials and conditions needed for life.

So my questions are

1) Is there a primary source for this work, and if so, what is the citation?

2) How did other physicists view this work? Was it accepted, rejected, expanded, or ????

thanks
Albatrossity | 07.08.08 - 3:03 pm | #

Albatrossity,

My answers, are:

1) I know of no primary source, that is I am not aware of Stenger's work being published in peer-reviewed literature.

2) Anecdotally speaking, I have never heard any professional physicist say or write that fine tuning is not a real problem and then, as way of explanation, refer to Stenger's work. Again, anecdotally, if Stenger’s work was ready for prime time, you would not expect someone like Susskind to say (paraphrasing, from memory) that "if there is no multiverse then we have no good answer to the (cosmological) ID guys." Instead he would have said: "If there is no multiverse, then we still have Stenger's argument to rescue us."

Having said that, I'd say that Stenger's approach is sensible. In a way it even seems more laudable than appealing to a multiverse.

I hope that answers your question.
heddle | 07.08.08 - 3:42 pm | #

Thanks!

I did search in Web o'Science for a citation, but didn't come up with one. It's nice to have some corroboration that I probably wasn't doing that wrong!

It does seem like a sensible approach to me too. I hope that he publishes it, or that someone else follows it up.
Albatrossity | 07.08.08 - 3:52 pm | #