Fine tuning: a discussion for the rest of us mortals

When we talk of the universe being fine-tuned, we are usually referring to the values of the fundemental constants. The fine-tuning is that which allows things like:- the universe to expand at a rate slow enough such that matter can gravitationally clump but not so slow that the universe recollapses before life has chance to appear.- heavy elements (as in > Lithium) to exist by virtue of Be/He/C resonanceAnother conundrum was "why is the universe so very very flat?"It doesn't have such an immediate application to the possibility/inevitability of life, but was still very mysterious until inflation provided a mechanism to naturally produce this fine tuning.However, I don't have any confidence that a similar mechanism will be found for the points above... the flatness problem is relatively very very simple.All fine-tuning problems can be circumvented by postulating that our universe is just one of an infinite number of universes. This is entirely plausible in a string/M-theory enhanced cosmologial scenario. However, many do not buy into this, mainly because it is not that aesthetic, and seems a bit of a cheat

It was finely tuned for the propensity/possibility of life. We are the proof of that. That is the universe's way of saying "get off of your collective arses and go explore!" Or as God put it, "go forth and multiply" Hmm, I used to think that way about my parents too... but I know better now.

Hi Omniv. If the constants were not much different from what they are, there wouldn't be time for life to evolve, or there wouldn't be any heavy elements out of which to create life. It is to this that the AP refers.

I appreciate this but in cosmological terms it just refers to the fact that a free parameter (in the current cosmological model) has a value essential to the existence of structure/complexity/life. It demonstrates a lack in the current model. Despite being theistic (and Christian) I would be most annoyed if the final TOE does not provide a naturalistic explanation to the values of all of the constants. Hmmm, I don't know... I've always liked the Strong Anthropic Principle. Not becasue of any religious leanings - indeed, inspite of them - but simply because of desire/perception of some connectedness. I think I should really be a Bhuddist Oh absolutely, but they go hand in hand with life... especially black holes. They are at the heart of much of the essence of reality/existence (black holes are more than just the end-points of stellar evolution, they play a MUCH larger role in everything). I think it's a nice concept. One place I do agree with the YECs is in describing everything - big bang to us - as an evolutiuon. Sentient - well, I think we provide that aspect. Personable - not sure, I don't (usually) equate this concept with my idea of God, but it really depends on the day of the week...

Hi Mick,Yeah, Gaia is a great mechanism for creating "fine tuning", although obviously wrt biological/chemical parameters rather than the fundemental constants (as you point out). Read about it and like it. If a bunch of prokaryotes can completely turn the atmosphere around (albeit taking 2,000,000,000 years to do it), then biosphere self-regulation doesn't look so incredible...Lovelock always comes across well. Interesting how recently he was reluctantly admitting the necessity for further fission power generation. That upset a few greens who thought he was on their side

Not at all. Some use it as a basis for teleology (Tipler to some extent) but this is not the case in general.The Weak AP is simply the observation that conditions in this universe must be such as to allow us to exist. It does not answer why those conditions have those values, only that they must have those values. Is this useful? Well, in some ways. It identifies those conditions that appear fine-tuned, and encourages further invetsigation to determine why they have those values. You are now moving into Strong AP territory. Slighter weaker than this is the point that for us to exist, you need the entire universe. The constants that give rise to our existence are the same constants that determine the size of the universe, its consituents, its age at our time of (first) observation, etc.The Design argument would be that, yes, everything that exists, exists for our existence. There's not much I can think of that you can remove from the universe without seriously impacting the possibility of intelligent life.If it has a religious connotation, I've always found the AP more Bhuddist in approach than Western religion.

Possibly, but this is not what the AP states. It does not talk in terms of probabilities, only necessities to life. It is about identifying those properties of the universe that have to be just so for us to exist. The question is then, what makes these properties take those values? Are they fine tuned by natural means (lack of spatial curavture via inflation) or are they free parameters (G, alpha, etc).The supposedly free parameters are where the probabilities possibly come in. If G falls outisde a critical range, universes fly apart and disperse before stars can coalesce or collapse far too soon. Change alpha and stars don't shine... Given enough trial universes, you will have a subset where the parameters are such that life can exist. If only one universe, then questions of design creep in. I'm not convinced of this. I think it's still wide open... I can certainly envisage the earth being the only life-abundant planet in the Galaxy.

First off, while we are sticking to weak AP concepts, there really is nothing metaphysical about all of this. I don't differentiate the two. The universe we see is one capable of bringing forth intelligent life (obviously) The vast stretches of inhospitable space are just as necessary to our existence as the oxygen in our atmosphere -it is very hard to imagine the latter without the former.

No, it is everything. Alpha and G are critical to life, and are universals through-out the universe. They dictate whether stars are possible, or molecules. There is plenty of fine-tuning before we even get to the stage of asking what is needed to get a decent planet somewhere.But still you seem to think the AP (or WAP at least) is saying something it is not. The WAP is essentially: Properties of the Universe are such that allow the possibility of intelligent life (human terrestrial life). It's not really a big deal. It is used simply to draw attention towards those very properties for further investigation.Why is the universe 13.7 billion years old? It has to be around this age for us to observe it - any earlier and there hasn't been sufficient time for observers to arrive - auto-tuning. End of story.Why does alpha have its value? If it did not, there would be no observers - fine tuned. What has caused alpha to take this value? We don't know... yet.

No, becasue you are into serious metaphysics at this point. Exactly. Had. No more. It's not only the values you need but enormous external stability over a vast time. It took 2Gyears for the prokaryotes to transform our atmosphere to something viable for future evolution - half the age of the earth - almost a sixth the age of the universe!!! Well, you can't go back too far, as you run out of building materials. The future, on the other hand, is a better prospect. Wish I'd seen it, but then I have destroyed too many TV sets after watching bad science on Horizon I would be very interested in what they thought to change.

Not really. The universe appears exceptionally fine-tuned for our existence (and hydrogen, water, computers and Xboxes). The question is why does it appear so?You can claim that there is only one universe and we arrived simply by improbable chance in a universe with lots of room for improbable possibilites. That ignores the fact that no matter how large the universe, the global pararmeters are still mysteriously fine tuned to our existence.Obviously you can argue that it was designed that way by some intelligent designer, but that is rather unsatisfactory as it implies a bit of fudge to this otherwise incredible creation.You can claim that the parameters are randomly distributed, and given sufficient (infinite?) "universes", either sequentially or not, universes will arise that are suitably configured for human life and we are destined to observe such universes. I also find this a little unsatisfactory. Perhaps better to consider a larger universe with regions that span all possible values of the (now no longer) global parameters, such that some areas are life-possible.Where does that leave me? Well, I have some rather odd ideas about it all

You have a lot to learn about this universe Try altering alpha (the fine structure constant) by a touch and notice how all the stars go out - proton-proton chain is very dependent upon alpha. Shift G a bit (or lambda) and the universe flies apart so quickly stars don't even get chance to coalesce, or in the other direction all the matter quickly forms black holes.I'm not so interested in the Earth being compatible with life; rather the universe being compatible with stars and planets. This requires knowing why G and alpha have the values they do.

No, of course not. I'm a cosmologist/physicist and I want to know why the universe is the way it is. If I was happy to just say, oh that's the way it is, I wouldn't have devoted so much of my life to the pursuit of science. Welcome to theoretical phsyics... Possibly. The question is what is the space of all possible universes, and what sub-space is compatible with intelligent life? It appears that for most value of G and alpha, no structure (and hence probably life) at all would be possible.

A good way of putting it Well, that's not very GR. When I "step outside", I'm stepping outside time. That is how we study space-time. So I try to look at the universe as a whole unit, and ask what possible universes there could be. This is a very deep metaphysical point. I actually probably hold the opposite view. I would like to get to a point of seeing the universe "as is" as wholly necessary. This starts to verge towards something similar to strong AP, but I stay clear of any religious overtones. It depends what you mean by "this one". If you mean this exact one with Earth and you and me, then I think that's asking a bit much. But yes, I don't think we got these laws and this type of universe by chance. I think it was necessary. Not yet I have a strong inkling that existence and even life and conciousness are all tied up with mathematics in a semi/pseudo Platonic sense but I'm stil working on it. Only I don't get paid to work on it any more which is a bit crap...

I'm using it in a backwards mathematical sense: not necessary "for" anything in particular, but a necessary conclusion. Perhaps "inevitable" would be better, though that has time-related connections of which I try to stay clear.Perhaps you are familiar with fractals, and the Mandelbrot Set (MS)in particular? I see the universe as a kind of MS - a fixed ultra-complex entity. Our time-restricted view of reailty is simply moving slice by slice through a higher-dimensional MS. From this POV, the features that are observed look random and driven by chance, but when viewed from outside time, they are seen as fixed and "necessary" elements of the mathematical solution. I'm trying to push as far as possible. I understand mathematics and physics. I have no way of including theistic concepts other than "perhaps god did this here". It just isn't very satisfactory. I'm trying to understand god's creation, not just accept that he created it. Perhaps, but the meaning is purely in terms of the part life and conciousness plays in the mathematical solution of the universe.Perhaps something from Hitchhikers Guide to the Galaxy will help - paraphrasing DeepThought concerning the Earth - "a computer so complex that living creatures actually form part of its computational matrix"Substitute universe for Earth and you have an idea of the areas in which I muse. As important as every other element of the universe - and given the grandeur of the universe, I would say very important