The science of "fine-tuning"

[kevin]

In the set of all possible universes allowed by theoretical physics, the set that would provide conditions under which life could form is extremely small.

i atill dont understand how ^^^this is a problem. sure, the chances are small. but it only has to happen once, and it clearly did.

the chances of me winning the powerball lottery are i in 292,201,338.

thats a very small number. yet i have seen half a dozen people beat those odds in the last year or two.

there was no fine-tuning in any of those particular people winning the lottery. it's just that the lottery continues until somebody wins. a winner is inevitable.

if a universe that contains lifet occurs only once in 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 chances,

we would expect to see exactly what we see now-- a universe that contains life. we missed out on observing all the other possibilities because we did not exist.

[8livesleft]

Now, are we saying:

I think what we are saying is that this is science, just like all other science. Probably not as well based as the science that put men on the moon, but better based than much of evolutionary science which most of us accept. It is interesting to me to see people so willing to doubt this science while accepting most other science.

I'm not sure if we can put the theories here ahead of evolutionary science such as genetics, evolutionary biology. 

That said, again, it's not so much the science but the narrative which we seem to be arguing about. Of course, as a theist, you want to defend those theories that support your narrative that there is a god, that's only normal.

However, as much as we want these theories to prove our narrative, there's simply not enough data to do so. 

[8livesleft]

How do you know?  Using your 4 above questions, we can ask you the same kind of questions you've been asking.

Yes, that's right, I don't know. Nobody does. 

[unkleE]

The fine-tuning argument appears to fail on all counts - feasibility, motive, consistency.

Hi Novice, thanks for sharing your thoughts. But perhaps you should tell youir objections to the cosmologists, not to me. From what I can see, there are a number of errors in your post:

There are other theist positions

This has nothing to do with theism. Of the three authors of the two books I referenced, one is a theist, one is an agnostic and one is an atheist. THis means most of your comments are unfortunately not relevant to what I have posted.

One cannot define probability for an event AFTER the same event has occurred.

You and I may not be able to, but cosmologists have. Remember, Penrose was Professor of Mathematics.

The example of royal flush in poker is not making any sense to me.

It isn't an example of fine-tuning, but of probability.

[unkleE]

"Reason" has two definitions: it can be an explanation, or it can be a rational ground/motive.

Yes. And I clearly used it in the first sense.

You created a scenario with cards, said the intelligent agent exists, made an argument that we have to consider that intelligent agent's actions, and then are saying your own argument is unscientific?

It was an example of probability, not an analogy. Just pointing out that we would question blind chance when the odds are so much better than the odds of the universe by chance. I'm not sure if you or anyone else really gets how small Penrose's odds are. There are 10^80 baryons in the universe. We could write that number out with just 81 digits (1 followed by 80 zeros). If we wrote a zero on every baryon in the universe we would have a number 10^10^80, still way short of Penrose's 10^10^123. So if you'd be suspicious about chance for 1 chance in 3 X 10^77, how much more suspicious should you be of a 1 in 10^10^123 chance?

[unkleE]

i atill dont understand how ^^^this is a problem

Let me have one more go at it.

if a universe that contains lifet occurs only once in 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 chances,

First of all, this isn't right. If I counted right, you had 400 zeros = 4 x 10^2. That's a big number, but to get Penrose's odds, you'd have to have 10^123 zeros. If you understand exponents, as I imagine you do, you know that's a heap more. I think you'd need to write a zero on every one of the 10^80 baryons in 10^43 universe like ours to get the number we're talking about.

sure, the chances are small. but it only has to happen once, and it clearly did.

Two things wrong with this.

1. The lottery win happened because someone HAD to win. WE don't know that's the case with the universe, thought the multiverse hypothesis might provide that.

2. Lewis & Barnes say that coincidences are always worth investigating in science, because they may mean we have made a wrong assumption. In the case of the cards, how low must the chances be before the possibility of cheating is more reasonable? Imagine a paternity case where the accused father denies the genetic evidence by saying the close match happens by chance occasionally, so that's clearly what happened here. Should he be believed. Everyone on tis thread seesm to be sayin they'd believe the man rather than the DNA evidence!

[unkleE]

That said, again, it's not so much the science but the narrative which we seem to be arguing about. Of course, as a theist, you want to defend those theories that support your narrative that there is a god, that's only normal.

It is interesting that other people keep raising the theitic option, when I haven't. As I have said already, atheists and agnostics as well as theists accept the reaily of scientific fine-tuning, with very few if any exceptions among cosmologists. Makes me suspicious that people here allow their anti-theistic bias to be more important than the science.

[8livesleft]

That said, again, it's not so much the science but the narrative which we seem to be arguing about. Of course, as a theist, you want to defend those theories that support your narrative that there is a god, that's only normal.

It is interesting that other people keep raising the theitic option, when I haven't. As I have said already, atheists and agnostics as well as theists accept the reaily of scientific fine-tuning, with very few if any exceptions among cosmologists. Makes me suspicious that people here allow their anti-theistic bias to be more important than the science.

Fine tuning isn't a reality.

It is an unproven theory, regardless of degree of acceptance, is it not?

Besides, I don't have a bias against the existence of god, I have a bias against sentiments which seem too quick to conclude it with absolute certainty (and this goes both ways).

[Novice]

Now, are we saying:

I think what we are saying is that this is science, just like all other science. Probably not as well based as the science that put men on the moon, but better based than much of evolutionary science which most of us accept. It is interesting to me to see people so willing to doubt this science while accepting most other science.

Hi UnkleE, it is not surprising to me. If someone says there were 1 in 10^10^123 possibilities and this universe was one of the possibilities, I would not have more than a cursory interest. But this extended to more than a scientific conjecture. (10^10^123 -> fine-tuning -> God -> change your belief) requires a non-theist to scrutinise this more than usual. This should not be unexpected. If I say there was an incident near my house, that would raise hardly any interest, but if I say there was an incident near my house that disproves God, wouldn't you be more than interested and scrutinise it more than any other random incident that you come across?

Also, the science part stops at 10^10^123. Extrapolating this to fine-tuning and eventually God is speculation. It is not science and the extrapolation seems mathematically and logically incorrect.

While ultimately with my limited knowledge, I cannot rule out fine-tuning and hand of God, the doubts that I have from different angles have not been sufficiently addressed. You have not made any serious attempts to address this other than brushing it off. So, I remain skeptical of fine-tuning.

[Novice]

The fine-tuning argument appears to fail on all counts - feasibility, motive, consistency.

Hi Novice, thanks for sharing your thoughts. But perhaps you should tell youir objections to the cosmologists, not to me. From what I can see, there are a number of errors in your post:

There are other theist positions

This has nothing to do with theism. Of the three authors of the two books I referenced, one is a theist, one is an agnostic and one is an atheist. THis means most of your comments are unfortunately not relevant to what I have posted.

One cannot define probability for an event AFTER the same event has occurred.

You and I may not be able to, but cosmologists have. Remember, Penrose was Professor of Mathematics.

The example of royal flush in poker is not making any sense to me.

It isn't an example of fine-tuning, but of probability.

Hi UnkleE, you have brushed off all the doubts without really addressing anything. Picked few lines here and there and tried to poke irrelevant and imagined holes. I would suggest you to rethink your arguments if you want it to stand up to more than 5 minutes of serious scrutiny. Thanks for your thoughts anyway.

[Kiahanie]

The universe is remarkably supportive of life on our little blue ball. There are a lot of universal constants that if significantly changed would make us impossible but create possibility for something else.

If that is all that is meant by "scientific fine-tuning" I do not see a problem with that. Unfortunately, the "fine tuning" argument was stained by theists trying to prove a creator god. Now we have a sanitized phrase. That is a good thing.

Where the water gets deep is when people use that alleged fact as a predicate for other arguments.

I strongly suspect that if there are other universes they will end up finely tuned to support whatever matter and energies may inhabit them.

[unkleE]

Hi UnkleE, you have brushed off all the doubts without really addressing anything. Picked few lines here and there and tried to poke irrelevant and imagined holes. I would suggest you to rethink your arguments if you want it to stand up to more than 5 minutes of serious scrutiny. Thanks for your thoughts anyway.

Hi Novice, I'm sorry if I have offended you in any way. But please note that:

• I placed this post in the Science section and said it was about the science, not a theistic argument.
• I have pointed out that the science of fine-tuning is NOT in itself a theistic thing - many of the cosmologists working on this are not theists.
• I am not making any argument as you suggest. I have specifically said I am not. I am merely trying to outline the science of fine-tuning in a quick summary form so people on this forum will understand it.

So it is up to you if you are interested or not.

[unkleE]

Fine tuning isn't a reality.

It is an unproven theory, regardless of degree of acceptance, is it not?

I'm sorry, 8lives, but this isn't factually correct. It isn't a theory, it's a set of results of observation and theoretical physics. These results show that if many cosmological parameters were even a little different, there's be no habitable universe. At present that is as much a scientific fact as anything else in cosmology and theoretical physics.

The explanation of why these results occur may be a theory, but that isn't primarily what I have been talking about.

[kevin]

i atill dont understand how ^^^this is a problem

Let me have one more go at it.

if a universe that contains lifet occurs only once in 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 chances,

First of all, this isn't right. If I counted right, you had 400 zeros = 4 x 10^2. That's a big number, but to get Penrose's odds, you'd have to have 10^123 zeros. If you understand exponents, as I imagine you do, you know that's a heap more. I think you'd need to write a zero on every one of the 10^80 baryons in 10^43 universe like ours to get the number we're talking about.

unkle E, 4 x 10^2 is 400. what i wrote out was 1 x 10^400, vastly larger than 1 x 10^123. in fact, its 1 x 10^277 times as large. my number was huge compared to penrose. 1 x 10^277 is  one times 10 followed by 277 zeroes. one billion is only 1 x 10^9.

but it doesnt affect the argument. doesnt matter how rare a particular combination is-- we beat the odds, because we're here. no matter how rare it is, it happened.

where do the cosmologists suppose these alternate realities come and go from?  do they suppose universes are being created and destroyed out of a random vat of physical and mathematical constants, each of which has an equal chance of occurring? how do they justify that idea?

im questioning that there are all these alternative universes in the first place, and that they all have an equal chance of being here,. it must be possible for them to be created in order for us to count them. who or what is doing the creating? when and where does it happen? is it happening now?

since penrose asserted that there were 1 x 10^23 possible universes that could have occurred,  he must be able to answer thse questions. what does he say?

sure, the chances are small. but it only has to happen once, and it clearly did.

Two things wrong with this.

1. The lottery win happened because someone HAD to win. WE don't know that's the case with the universe, thought the multiverse hypothesis might provide that.

if someone didnt win, we wouldnt be talking about it. someone HAS to win, in order for the conversation to take place.

2. Lewis & Barnes say that coincidences are always worth investigating in science, because they may mean we have made a wrong assumption. In the case of the cards, how low must the chances be before the possibility of cheating is more reasonable? Imagine a paternity case where the accused father denies the genetic evidence by saying the close match happens by chance occasionally, so that's clearly what happened here. Should he be believed. Everyone on tis thread seesm to be sayin they'd believe the man rather than the DNA evidence!

^^not my discussion point, so i dont have anything to offer.

[8livesleft]

Fine tuning isn't a reality.

It is an unproven theory, regardless of degree of acceptance, is it not?

I'm sorry, 8lives, but this isn't factually correct. It isn't a theory, it's a set of results of observation and theoretical physics. These results show that if many cosmological parameters were even a little different, there's be no habitable universe. At present that is as much a scientific fact as anything else in cosmology and theoretical physics.

The explanation of why these results occur may be a theory, but that isn't primarily what I have been talking about.

Apologies. I'm clearly quite dense on the subject...

I get caught up on the term "fine tuning" which clearly implies a tuner.

Anyway, what you're saying sort of reminds me of numerology. You know that thing where they count how many letters are in your name and then add up your birthday in order to get you a kind of horoscope?

The computations in numerology are all completely sound mathematics but the interpretation is theoretical.

Going back to the maths and observations of this concept, I agree that it is indeed sound (given the known parameters and observational data). But, it simply points to unlikelihood but not that intervention is necessary, imo.

[Francis]

.

[unkleE]

unkle E, 4 x 10^2 is 400. what i wrote out was 1 x 10^400, vastly larger than 1 x 10^123. in fact, its 1 x 10^277 times as large. my number was huge compared to penrose. 1 x 10^277 is  one times 10 followed by 277 zeroes. one billion is only 1 x 10^9.

Sorry Kevin, Penrose's number is 10^10^123, vastly, vastly larger than your number.

but it doesnt affect the argument. doesnt matter how rare a particular combination is-- we beat the odds, because we're here. no matter how rare it is, it happened.

The first thing to recognise, which I'm struggling to get across, that our universe beat the odds as you put it. Am I assuming you now accept that?

where do the cosmologists suppose these alternate realities come and go from?  do they suppose universes are being created and destroyed out of a random vat of physical and mathematical constants, each of which has an equal chance of occurring? how do they justify that idea?

This is the natural question that arises once we accept that the universe is indeed "fine-tuned", i.e. that small changes in parameters make the universe unfit for life or anything interesting. But please note that the questions about causes are separate from the near unanimity about the fact.

The cosmologists (some, probably the majority) believe there is a larger reality they call the multiverse. They beleve it occasionally "bubbles" out a region that becomes another universe and exists in a separate space-time continuum so we can't ever observe the multiverse or other universes. The idea that each one takes on a separate set of values, so making a life-friendly universe quite possible has no basis that I have seen, but I'm guessing they think all the values are random, so why not.   

There are apparently aspects of string theory and other physics that suggest this might happen, though other cosmologists believe that isn't the case, and most accept that we can probably never verify (or falsify) the idea by observation. There are serious problems with the multiverse idea, but it remains the only scientific explanation available at present. There are a few cosmologists who believe the apparent fine-tuning is not the true picture and they hope to find some theoretical reason why the values couldn't have been much different, but these just seem to be ideas at present.

since penrose asserted that there were 1 x 10^23 possible universes that could have occurred,  he must be able to answer thse questions. what does he say?

Just repeating that it was 10^10^123. I don't know what he thinks about the multiverse. I have just read a few pages of his book where he does this calculation and he doesn't say how he thinks it occurred, though he speculates that there may be some theoretical reason related to The Weyl Curvature Hypothesis,whatever that might be. (He actually talks about "the creator's aim" and has a little sketch of a person pointing at a dot in a large space, but as far as I know he is agnostic about God and only used those words as a figure of speech.)

if someone didnt win, we wouldnt be talking about it. someone HAS to win, in order for the conversation to take place.

Sure, but why? A detective finds a body with a shot in the back and concludes there must have been a murder because there is a body. But he/she still needs to ask who and why? Same here.

[unkleE]

I get caught up on the term "fine tuning" which clearly implies a tuner.

It may imply this to you and I can understand why, but not (apparently) to a physicist. Here's a quote from Wikipedia:

"In theoretical physics, fine-tuning is the process in which parameters of a model must be adjusted very precisely in order to fit with certain observations."

Going back to the maths and observations of this concept, I agree that it is indeed sound (given the known parameters and observational data). But, it simply points to unlikelihood but not that intervention is necessary, imo.

That is a separate question. There are three possible steps in any argument about "intervention":

1. Fact: small changes in about a dozen universal constants would change the universe immensely and make it unfit for life or anything. MOst cosmologists accept this, but a small minority do not.

2. Scientific explanation: the odds of this happening by chance are so small as to require another explanation. The most favoured explanation, even though quite speculative, is the multiverse. A small number of physicists believe or hope that a theoretical reason will be found, and some think they may be on the track of finding it.

3. Theistic argument: granted all this,  does this make it more probable that God exists?

In this discussion I have explicitly said I am not talking about #3. My main aim was to clarify #1 so at least we could all be on the same scientific page, but of course #2 comes into it.

[Novice]

Hi UnkleE, you have brushed off all the doubts without really addressing anything. Picked few lines here and there and tried to poke irrelevant and imagined holes. I would suggest you to rethink your arguments if you want it to stand up to more than 5 minutes of serious scrutiny. Thanks for your thoughts anyway.

Hi Novice, I'm sorry if I have offended you in any way. But please note that:

• I placed this post in the Science section and said it was about the science, not a theistic argument.
• I have pointed out that the science of fine-tuning is NOT in itself a theistic thing - many of the cosmologists working on this are not theists.
• I am not making any argument as you suggest. I have specifically said I am not. I am merely trying to outline the science of fine-tuning in a quick summary form so people on this forum will understand it.

So it is up to you if you are interested or not.

Hi UnkleE, you have been polite and civil in the discussions, probably more than me, so I have no reason to be offended. I was rather frustrated. I realise this is probably the wrong section for me to share my thoughts, but then you restricted the discussion in the other thread as well. In any case, I will bow out of this discussion and let you continue the conversation with this final thought. You can ignore it if you feel like it does not fit your expectations. I will not be offended :).

Do you think deserts are fine-tuned for desert lizards, do you think our polar regions are fine-tuned for polar bears? Or is it the other way around, did these animals evolve thanks to the conditions of their location? Scientifically speaking, the earth's tilt contributed to the creation of deserts and hence desert lizards. Was the earth's tilt fine-tuned so that desert lizards can come into existence?

[Dexter]

Hi everyone, it seems you are all repeating all the standard azrguments by non-cosmologists to the science of fine-tuning.

Kevin: you are more or less arguing for the multiverse - zillions of universes, so sooner or later one will likely support life. As I have said, that is the most popular scientific response. But it is unproven, likely unprovable and much disputed.

Mooby: hi mate, nice to see you again! This is the anthropic principle. Yes, if there weren't observers like us, no-one would know our universe existed. True. But it still doesn't explain why it happened - which is what science is all about. Imagine this hypothetical. You and I play poker. I get a royal flush and so win 10 games in a row. The odds of this are approx 6 x 10^-39. And so you begin to wonder if I am cheating. By I reply "but  these hands are as likely as any other, and these odds are way, way better than the odds of fine-tuning by chance, which you've said is quite OK." Would you be convinced? Say you are convinced, because, after all, you've explained away much much longer odds, so we play another 10 games & I get another 10 royal flushes. Odds of approx 3 x 10^-77. Do you get suspicious, or do you remain convinced that, since the odds are still way, way better then the fine-tuning by chance, you keep playing (if you have any money left!)?

I wonder if a young earth creationist has ever visited this forum, and any of you criticised him/her for not accepting the science?

Fine tuning is nonsense. You are tying yourself up in knots on the flimsiest hope of even providing 1 argument. We exist because the laws of the universe are what they are. The universe doesn't exist because it was fine tuned to suit our existence. 

[Mooby the Golden Sock]

I'm not sure if you or anyone else really gets how small Penrose's odds are[. . .]if you'd be suspicious about chance for 1 chance in 3 X 10^77, how much more suspicious should you be of a 1 in 10^10^123 chance?

Penrose published his book with that estimate in 1989.  Given 1-2 year publishing times, that makes it a 35 year old estimate.  Now, I'll be the first to admit that this is not my field; however, I was taught that when doing a literature review of a very active field, you really want to be looking in the last 5 years of research.  By comparison, the second superstring revolution and the development of M theory happened 5-10 years after that book was published, and further development has continued since then.

Poking around online, I found this article from Fred Adams.  It's 4 years old, so likely much closer to where the current science actually is.  I won't pretend I've read the whole document in its entirety, but I'll point out some quotes I think are relevant with my emphasis added in bold:

The first step in determining the degree of fine-tuning of our universe — and others — is to delineate the range of parameter space for which observers can arise. This issue is made difficult because we have no definitive determination of what parameters are allowed to vary and what requirements must be enforced to ensure habitability. For this latter issue, this treatment considers a universe to be viable if it can successfully produce complex structures, including composite nuclei, planets, stars, and galaxies. The genesis of these entities puts additional constraints on the universe itself.

The allowed parameter space is large. Most of the relevant parameters can vary by several orders of magnitude and still allow for the development of complex structures, from atoms to stars to galaxies[. . .]

Our universe does not lie at the center of parameter space. The ranges for viable parameters are often asymmetric and are sometimes constrained in only one direction[. . . .]

Universes have multiple pathways. Viable universes are not required to be exactly like our own — they can in principle achieve habitability through alternate routes: Although our universe has β << 1, so that the electron mass is much smaller than the proton mass, the opposite ratio β >> 1 could also allow for working atoms[. . . .]With sufficiently large departures of dark matter properties and gravity, other universes can generate enough energy to sustain habitable planets through dark matter annihilation or even black hole radiation (Section 9). These alternate pathways expand the range of parameter space for viable universes[. . . .]

Myths and unnecessary constraints: A number of constraints that are often enforced on viable universes are not as severe as some previous work suggests[. . .]The relaxation of these unnecessary constraints results in a significantly larger parameter space for working universes.

Discussions of fine-tuning often implicitly assume that our universe is optimized for the development of observers [341]. However, it is interesting to revisit this panglossian assumption [38] and ask if different choices for the fundamental constants or the cosmological parameters could lead to universes that are even more favorable to the development of life, or at least the production of complex cosmic structure (see also [393]). In the realm of extra-solar planetary systems, researchers are now considering whether or not Earth is the best prototype for a habitable planet [275, 428]. Asking the same question on a cosmic scale, we find that several parameter choices could lead to possible improvements of the universe:

He goes onto list 6 examples of universe changes that could potentially make the universe much more suitable for life.

Granted, he does acknowledge some factors that are indeed non-negotiable: for example, he states, "Even if the parameters of physics and cosmology can deviate from their values in our universe by orders of magnitude, 'unnaturally small' ratios are still required: For example, the cosmological constant can vary over a wide range, but must be small compared to the Planck scale (Section 10.2)." However, overall his estimates allow for a multitude of possible viable universes, which challenges the notion that the existence of a universe that supports life must be a near-impossibly low probabilistic event.  It certainly seems to challenge Penrose's assumption that the parameters of the universe must fall within a 1 in 10^10^123 window.

Despite us bickering over the exact application of the "deck of cards" analogy, I believe we at least broadly agree that a true random shuffle is a routine, unremarkable low-probability event, but that shuffles that consistently produce the best hand are unusual low-probability events that warrant investigating an alternative explanation. So the crux of the question is whether our universe is just a routine cosmic shuffle, or a shuffle that produces a suspiciously good hand.

You have likened our universe to a royal flush, which implies its uniqueness and rarity.  But if Adams is right, our universe may just be a regular flush, or two pair, or maybe even just a high card.  After all, 95% of our universe appears to be completely empty, we currently know of only a couple places in our universe where life is even possible, and only one place where it actually exists. And that one place has had 5 mass extinction events (in addition to mention regular extinctions that happen constantly), and possibly is heading into a 6th one.

It's very well possible that our universe is not finely-tuned for life: rather, it's quite inhospitable to life, and life exists in spite of that.  If any other universes exist out there, it very well could be that we're in the bottom tier of universes that support life, and that other universes out there are much better at it than ours is.  So this notion at the crux of the argument--that our universe is unique and noteworthy--is itself a bit spurious as current observation suggests we are probably in one of the more unremarkable ones.  So, to answer your question, I am not suspicious about our universe's existence, because I'm not convinced that it's anywhere near as remarkable on the cosmic probability scale as your posts imply.

[8livesleft]

I get caught up on the term "fine tuning" which clearly implies a tuner.

It may imply this to you and I can understand why, but not (apparently) to a physicist. Here's a quote from Wikipedia:

"In theoretical physics, fine-tuning is the process in which parameters of a model must be adjusted very precisely in order to fit with certain observations."

Going back to the maths and observations of this concept, I agree that it is indeed sound (given the known parameters and observational data). But, it simply points to unlikelihood but not that intervention is necessary, imo.

That is a separate question. There are three possible steps in any argument about "intervention":

1. Fact: small changes in about a dozen universal constants would change the universe immensely and make it unfit for life or anything. MOst cosmologists accept this, but a small minority do not.

2. Scientific explanation: the odds of this happening by chance are so small as to require another explanation. The most favoured explanation, even though quite speculative, is the multiverse. A small number of physicists believe or hope that a theoretical reason will be found, and some think they may be on the track of finding it.

3. Theistic argument: granted all this,  does this make it more probable that God exists?

In this discussion I have explicitly said I am not talking about #3. My main aim was to clarify #1 so at least we could all be on the same scientific page, but of course #2 comes into it.

1 & 2 are related to me as both are related to unlikelihood (again, given the limited understanding we currently have).

I still don't see how unlikelihood would point to anything other than unlikelihood. I agree that the chances are infinitely small but not zero. It occured and that's a fact too.

As for the reasons for this unlikelhood, yes, multiverse is one possibility, and it's even alluded to by religions when they describe other worlds such as heaven or hell or some eternal elsewhere or even some place where their gods come from.

Another possibility for me, is simply an eternal cyclical universe which penrose himself proposed.

God or maybe gods are another possibility. Personally, however, I don't see the logic in proposing yet another unlikelihood to explain another. We might as well just make anything up if that's the case.

[unkleE]

Penrose published his book with that estimate in 1989.  Given 1-2 year publishing times, that makes it a 35 year old estimate.

Yes, that's true. But Paul Davies and others have referred to it since, and Lewis and Barnes refer to it in their 2016 book. No-one seems to have refuted it.

Poking around online, I found this article from Fred Adams.

Yes, I have said all along that there is a minority of cosmologists who contest the broad consensus, and Adams is notable here. I have compiled a bunch of references to post here, and Adams is on that list. But as far as I can tell:

• his views are very much in the minority. Lewis and Barnes refer to over 200 papers in support of fine tuning.
• Lewis and Barnes discuss his ideas but they don't change the overall picture, though they may become more mainstream, who can tell?
• Barnes says Adams assumes what appear to be wide ranges for some parameters (several orders of magnitude), but since some of the parameters can differ by 40 orders of magnitude, he has made very limiting assumptions, and
• his work only relates to one aspect of fine-tuning, so that Adams still says "Even if the parameters of physics and cosmology can deviate from their values in our universe by orders of magnitude, "unnaturally small" ratios are still required"

So I think I have presented the current science fairly, though of course it can always change, as all science can.

So, to answer your question, I am not suspicious about our universe's existence, because I'm not convinced that it's anywhere near as remarkable on the cosmic probability scale as your posts imply.

I don't think you are accurately reading the current state of play, but that is up to you.

[unkleE]

I started this thread to offer a brief outline of the science of "fine-tuning". I think I have done that, and it is probably a good time to leave the topic be. So here is a list of a few representative papers and articles for those who want to read up more.

• The Fine-Tuning of the Universe for Intelligent Life. Luke Barnes, 2011. A summary paper that has a similar basis to the Lewis & Barnes book. I suggest you read the text and skip over the mathematics.
• A Natural Introduction to Fine-Tuning. Julian De Vuyst, 2020. A more recent summary paper.
• Fine tuned universe, Wikipedia. A useful broad layperson's summary.
• The Universe Really Is Fine-Tuned, And Our Existence Is The Proof. Ethan Siegal, Forbes, 2019. Another "popular" summary.
• Is the universe fine-tuned for life? Universe Today, 2021. More or less a review of the Lewis & Barnes book.
• Our Universe Is Finely Tuned For Life, And There's an Explanation For Why That Is So. Science Alert, 2021. One attempt to explain the fine-tuning.
• A Third Way to Explain Fine Tuning. APS Physics, 2021. And another.
• Is the fine-tuned universe an illusion? Physics.org, 2022. A bunch of sceptics including Fred Adams & David Sloan.
• Is our universe "fine-tuned" for life? Physics Reports, 2021. More on Fred Adams.

So I think a fair summary is this: 50 years ago, cosmologists discovered that as they built mathematical understanding of the universe, about half a dozen or a dozen parameters had to be in a very narrow range to allow the universe to have structure and support life. This became cosmological orthodoxy, and many of the biggest names in cosmology (Barnes names about 20, including Hawking, Davies, Rees, Susskind, Smolin, Vilenkin, etc) supported this. As time went on, the details were further investigated and the models further developed. Most of the identified fine-tuning remained, but a few aspects have been found to be problematic. (Fred Adams and the evolution of stars is one such case, apprently.) There are a few cosmologists who dissent, but the consensus hasn't been overturned yet.

[8livesleft]

I started this thread to offer a brief outline of the science of "fine-tuning". I think I have done that, and it is probably a good time to leave the topic be. So here is a list of a few representative papers and articles for those who want to read up more.

• The Fine-Tuning of the Universe for Intelligent Life. Luke Barnes, 2011. A summary paper that has a similar basis to the Lewis & Barnes book. I suggest you read the text and skip over the mathematics.
• A Natural Introduction to Fine-Tuning. Julian De Vuyst, 2020. A more recent summary paper.
• Fine tuned universe, Wikipedia. A useful broad layperson's summary.
• The Universe Really Is Fine-Tuned, And Our Existence Is The Proof. Ethan Siegal, Forbes, 2019. Another "popular" summary.
• Is the universe fine-tuned for life? Universe Today, 2021. More or less a review of the Lewis & Barnes book.
• Our Universe Is Finely Tuned For Life, And There's an Explanation For Why That Is So. Science Alert, 2021. One attempt to explain the fine-tuning.
• A Third Way to Explain Fine Tuning. APS Physics, 2021. And another.
• Is the fine-tuned universe an illusion? Physics.org, 2022. A bunch of sceptics including Fred Adams & David Sloan.
• Is our universe "fine-tuned" for life? Physics Reports, 2021. More on Fred Adams.

So I think a fair summary is this: 50 years ago, cosmologists discovered that as they built mathematical understanding of the universe, about half a dozen or a dozen parameters had to be in a very narrow range to allow the universe to have structure and support life. This became cosmological orthodoxy, and many of the biggest names in cosmology (Barnes names about 20, including Hawking, Davies, Rees, Susskind, Smolin, Vilenkin, etc) supported this. As time went on, the details were further investigated and the models further developed. Most of the identified fine-tuning remained, but a few aspects have been found to be problematic. (Fred Adams and the evolution of stars is one such case, apprently.) There are a few cosmologists who dissent, but the consensus hasn't been overturned yet.

I don't think there's much disagreement that the odds are slim. But odds are odds and we have proof it isn't zero.

The question is, does it matter if the odds were 1:1 million, 1:1 trillion, 1:1 zillion¹⁰⁰⁰⁰⁰?

[unkleE]

Do you think deserts are fine-tuned for desert lizards, do you think our polar regions are fine-tuned for polar bears? Or is it the other way around, did these animals evolve thanks to the conditions of their location? Scientifically speaking, the earth's tilt contributed to the creation of deserts and hence desert lizards. Was the earth's tilt fine-tuned so that desert lizards can come into existence?

No, I don't think those things are fine-tuned. They are adaptations or evolution to suit the environment. But I don't think, and neither do the cosmologists, that a similar process is happening with the universe. If there were absolutely minor changes to universal constants, the universe ight still be suitable for life, but the changes were are discussing here are major changes, like the universe composed of only Hydrogen atoms, or only Helium atoms, or only lasting a ery short time before it collapsed in on itslef, or being so far-flung that particles would only "meet" another particle very rarely. In such universes, there's be no solid matter (or nor for long), no chemistry, no complexity, and hence nothing interesting, and certainly no life (except if we mean non-physical life!).

[unkleE]

The question is, does it matter if the odds were 1:1 million, 1:1 trillion, 1:1 zillion¹⁰⁰⁰⁰⁰?

If an event or fact is unusual, we look for explanations. Scientists noticed that light from a distant star appears to bend around the sun, so they asked why. Einstein answered the question. Meteorologists noticed that the world was getting hotter and so asked why, and the answer (already known but not fully appreciated) was carbon emissions, the trapping of heat and hence global warming. It is human to ask for explanations, and often it is life-saving.

So if the universal parameters are very unlikely by chance and very favourable to life, then asking why might tell us something.

[Kiahanie]

"Why" frames the issue incorrectly.

Asking "why" is probably a metaphysical question. Physicists and cosmologists deal with "how."

[Kiahanie]

I started this thread to offer a brief outline of the science of "fine-tuning". I think I have done that, and it is probably a good time to leave the topic be. So here is a list of a few representative papers and articles for those who want to read up more.

• The Fine-Tuning of the Universe for Intelligent Life. Luke Barnes, 2011. A summary paper that has a similar basis to the Lewis & Barnes book. I suggest you read the text and skip over the mathematics.
• A Natural Introduction to Fine-Tuning. Julian De Vuyst, 2020. A more recent summary paper.
• Fine tuned universe, Wikipedia. A useful broad layperson's summary.
• The Universe Really Is Fine-Tuned, And Our Existence Is The Proof. Ethan Siegal, Forbes, 2019. Another "popular" summary.
• Is the universe fine-tuned for life? Universe Today, 2021. More or less a review of the Lewis & Barnes book.
• Our Universe Is Finely Tuned For Life, And There's an Explanation For Why That Is So. Science Alert, 2021. One attempt to explain the fine-tuning.
• A Third Way to Explain Fine Tuning. APS Physics, 2021. And another.
• Is the fine-tuned universe an illusion? Physics.org, 2022. A bunch of sceptics including Fred Adams & David Sloan.
• Is our universe "fine-tuned" for life? Physics Reports, 2021. More on Fred Adams.

So I think a fair summary is this: 50 years ago, cosmologists discovered that as they built mathematical understanding of the universe, about half a dozen or a dozen parameters had to be in a very narrow range to allow the universe to have structure and support life. This became cosmological orthodoxy, and many of the biggest names in cosmology (Barnes names about 20, including Hawking, Davies, Rees, Susskind, Smolin, Vilenkin, etc) supported this. As time went on, the details were further investigated and the models further developed. Most of the identified fine-tuning remained, but a few aspects have been found to be problematic. (Fred Adams and the evolution of stars is one such case, apprently.) There are a few cosmologists who dissent, but the consensus hasn't been overturned yet.

You claim support from a variety of scientists who have very different takes on cosmology, and who have significant disagreements with each other. I think it is about time you are specific about this "consensus" that you are claiming, because I do not see a general consensus. Some overlap, some agreement between individuals, some specific agreements, some disagreements.

What are your specific claims of "consensus"?

[Mooby the Golden Sock]

• his views are very much in the minority. Lewis and Barnes refer to over 200 papers in support of fine tuning.
• Lewis and Barnes discuss his ideas but they don't change the overall picture, though they may become more mainstream, who can tell?
• Barnes says Adams assumes what appear to be wide ranges for some parameters (several orders of magnitude), but since some of the parameters can differ by 40 orders of magnitude, he has made very limiting assumptions, and
• his work only relates to one aspect of fine-tuning, so that Adams still says "Even if the parameters of physics and cosmology can deviate from their values in our universe by orders of magnitude, "unnaturally small" ratios are still required"

So I think I have presented the current science fairly, though of course it can always change, as all science can.

The above list sounds a lot like, "He says, she says" to me.  You do say later that there is a majority consensus, and I'll defer to you on that because again it's not my field, but at least as you're presenting it, nothing sounds settled.

Even if it is the case, what value does labeling the universe "fine-tuned" actually give us?  The mechanisms given on the Wikipedia page you linked are underwhelming at best: several of them are just some variation of "God/aliens/our future great grandkids made the universe/another universe from somewhere else in the multiverse/a computer simulation:" in other words, "turtles all the way down."

The two that seem viable are the multiverse and top-down cosmology, both of which I alluded to in Reply #17.  But without any hard evidence, they're merely conjectures that we have no way of turning into a falsifiable hypotheses.

It seems to me, at least from what you've posted in this thread, that this is a "check back in 30 years and see how the research has changed" situation.