Feeds:
Posts

## Is that really necessary? A Fine-Tuned Critique of William Lane Craig (Part 2)

Today, more on the work of William Lane Craig on the fine-tuning of the universe for intelligent life. The issue today is whether the laws/constants/initial conditions of the universe are, in some way, necessary. We think that the probability of a randomly chosen universe (with its laws, constants and initial conditions) being life-supporting is vanishingly small. We reach this conclusion by altering the laws/constants/initial conditions and predicting the outcome.

But perhaps when we have a deeper understanding of the laws of nature, we’ll realise that these constants couldn’t have been different. Or at least, we’ll realise that many of them are related, and thus cannot be altered independently. This would significantly reduce the probability of “getting the universe right”, as there are fewer dials to be tuned.

Let’s have a look at Craig’s response to this argument:

Physical necessity is the hypothesis that the constants and quantities had to have the values they do, so that the universe is of physical necessity life-permitting. Now on the face of it this alternative is extraordinarily implausible. It requires us to believe that a life-prohibiting universe is physically impossible. But surely it does seem possible. If the primordial matter and anti-matter had been differently proportioned, if the universe had expanded just a little more slowly, if the entropy of the universe were marginally greater, any of these adjustments and more would have prevented a life-permitting universe, yet all seem perfectly possible physically. The person who maintains that the universe must be life-permitting is taking a radical line which requires strong proof. But there isn’t any; this alternative is simply put forward as a bare possibility.

Sometimes physicists do speak of a yet to be discovered Theory of Everything (T.O.E.), but such nomenclature is … quite misleading. A T.O.E. actually has the limited goal of providing a unified theory of the four fundamental forces of nature, to reduce gravity, electromagnetism, the strong force, and the weak force to one fundamental force carried by one fundamental particle. Such a theory will, we hope, explain why these four forces take the values they do, but it will not even attempt to explain literally everything.

For example, in the most promising candidate for a T.O.E. to date, super-string theory or M-Theory, the physical universe must be 11-dimensional, but why the universe should possess just that number of dimensions is not addressed by the theory … All this has been said with respect to the constants alone; there is still nothing to explain the arbitrary quantities put in as boundary conditions.

Craig here is responding to some comments by Richard Carrier, some of which are pretty daft. Here’s Carrier: “in the 19th century there were some twenty to forty ‘physical constants,’ there are now only around six”. So Carrier’s physics credibility is non-existent.

Craig makes three main points:

1. These other universes seem to be possible.
2. A Theory Of Everything (TOE) won’t literally explain everything e.g the boundary conditions of the universe.
3. String theory is our best candidate TOE, and even it doesn’t uniquely predict the constants of nature.

My central criticism of Craig concerns his first point – it is far too weak. Scientific discoveries are surprising precisely because they are unexpected. Consider the following three constants: the electric constant, the magnetic constant and the speed of light. Prior to 1865, these constants seemed completely unrelated. Then Maxwell showed that light is an electromagnetic wave, and in so doing showed that these three constants are related.

So the constants of nature will always seem to be changeable. And, most importantly, no physicist believes that we have heard the last word on what we now think are the fundamental constants. To dismiss necessity, we need reasons to believe that, even as physics progresses, the laws of nature will still need to be fine-tuned for life.

Craig’s third point is similarly unconvincing. String theory is certainly a work in progress – we don’t even know the exact equations. The failures of string theory as a TOE should lead us to look for a better TOE, not conclude that no TOE will predict all the fundamental constants of nature.

Craig’s second point is starting to get somewhere. He is correct in that a TOE won’t explain literally everything. In particular, the initial conditions (or, more generally, boundary conditions) of the universe are a worry. Here’s a quote from John Wheeler that should keep cosmologists awake at night:

Never has physics come up with a way to tell with what initial conditions the universe was started off. On nothing is physics clearer than what is not physics: equation of motion, yes; initial position and velocity of the object which follows that equation of motion, no. (At Home in the Universe)

The problem is more general than just initial conditions. Even if the equations that describe our universe are unique, containing no free parameters, it doesn’t follow that the solution to the equation, and thus the universe itself, is unique. For example:

The equations of [string theory] have no adjustable constants, but their solutions, describing different vacuum states, are characterised by several hundred parameters-the sizes of compact dimensions, the locations of the branes, and so on. (Alex Vilenkin, “Many Worlds in One”)

The closest thing in physics to a “law of initial conditions” is the Hartle-Hawking no-boundary proposal. And if I had any idea what Hartle and Hawking were talking about, I’d tell you.

Craig’s objections aside, the idea that the fine-tuning of the universe can be explained by physical necessity hasn’t won many supporters. It’s not my preferred scenario. Let’s look at a few case studies to see what goes wrong.

A. An unknown physical process sets the constants/initial conditions to be in the life-permitting range. A good example here is inflation. In standard big bang cosmology, the matter density at early times needs to be fine-tuned to one part in $10^{55}$, otherwise it will be too dense (and recollapse into a big crunch) or not dense enough (and be unable to form galaxies/stars/planets/people). However, if the universe inflates (expands exponentially) in its early stages, then the density of the universe will be driven into the life-permitting range. Then we wouldn’t need special initial conditions – any old universe can be made to have a life-permitting density by inflation.

Could this type of scenario be true for all the other constants/initial conditions? I don’t think so, for the following reason. Inflation makes the universe life permitting by driving the density towards the “critical density”. The critical density can be specified independently of the requirements for life – it is the density that makes the universe spatially flat. It is then a very fortunate coincidence that life-permitting universes need to be very close to spatially flat. If this were not so – e.g. if life permitting universes needed to be 100 times less dense than critical – then inflation would make every universe life prohibiting.

So the success of inflation in making the universe life permitting relies on a coincidence between a life permitting and an independently given physical parameter. This would seem to be true for any physical mechanism that hopes to make the universe life permitting. But for every physical constant/initial condition to have an explanation of this type would require a multitude of as yet unknown physical parameters, which by some coincidence happen to lie in the life permitting range, and a physical mechanism that drives the actual constant toward this new parameter. This seems incredibly unlikely, and even if it were true, it would simply be another astonishing example of fine-tuning.

B. A deeper understanding of physical laws reveals that many/most/all the constants are related. Perhaps there is only one constant of nature, which itself sets the scale of the universe and is thus unobservable. Other physical constants turn out to be mathematical constants. Let me make three quick responses.

1. Suppose string theory achieves this goal. Even if there no alternatives within string theory, there are alternatives to string theory. Paul Davies says it well: “I think [the idea that there is only one possible universe] is demonstrably wrong. There is not a shred of evidence that the universe is logically necessary. Indeed, as a theoretical physicist I find it rather easy to imagine alternative universes that are logically consistent, and therefore equal contenders for reality”.
2. The problem of parameters in the solution, noted above by Vilenkin. It could turn out that what we think of as parameters of the laws of nature are simply parameters of the solution that describes our universe. They would, then, remain fine-tuned, since other solutions would presumably not be life permitting.
3. It would be the mother of all coincidences that the only universe permitted by the laws of nature would happen to permit intelligent life. In their classic paper on fine-tuning in 1979, Carr and Rees comment that “even if all apparently anthropic coincidences could be explained [by deeper physical law], it would still be remarkable that the relationships dictated by physical theory happened also to be those propitious for life.”

Let’s sum up. I agree with Craig that necessity isn’t the right explanation for the fine-tuning of the universe for intelligent life. I have an issue, however, with some of his arguments is favour of this conclusion. In the end, the idea that life-permitting universes are in some sense not possible seems incredibly implausible. As Craig says, we would want some very good reason or believing that.

More of my posts on fine-tuning are here.

### 31 Responses

1. Richard Carrier’s physics credibility may be pretty low, but since when is William Lane Craig an authority?

2. Yeah, neither has any authority but I don’t think Craig has said anything as ridiculous as Carrier’s claim that there are only six constants of nature. There isn’t a physicist alive that believes that. At least Craig’s views on the beginning of the universe are held by *some* cosmologists:

“It is said that an argument is what convinces reasonable men and a proof is what it takes to convince even an unreasonable man. With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape, they have to face the problem of a cosmic beginning.” (From: Alex Vilenkin, Many Worlds in One)

3. […] Part 2 is here. Possibly related posts: (automatically generated)Is that really necessary? A Fine-Tuned Critique of William Lane Craig (Part 2)The Shrinking Quarter: A Fine-Tuned Critique of Fred AdamsLife in a fine-tuned universe – Video […]

4. […] article. [LB: the article was published in a philosophical journal of a humanist society. Fail again, Richard Carrier.]. Particle physicist Victor Stenger has shown that our universe isn’t finely tuned at […]

5. lukebarnes,

Physicists keep telling me that ‘fine-tuning’ situations have come upon physicists many times in the past – for example some situations in condensed matter physics were certain values were all lined up really, really closely with their critical values.

But of course when that happens physicsts don’t quit doing physics and say, “Well! It must be magic!” No, they keep proposing models and testing them and eventually figure out what it is that produces this apparent fine-tuning.

So it seems to me the fine-tuning argument is out of touch with the recent history of physics, and would only work if you add the assumption that our fundamental physical theories are finished. But that’s absurd, because we know they are wrong/incomplete.

(1) Is this roughly correct?

and

(2) Can you name any specific examples of where else physicists have encountered and overcome apparent fine-tuning?

6. Ah … It’s Luke from commonsenseatheism … I was just admiring your comments on “Bart Ehrman VS The Infidel Guy” today. I was planning to do a review of William Lane Craig’s debate but it would have been much the same as yours: http://commonsenseatheism.com/?p=392

I’d have put the Avalos one in the “Ugly” pile, and Atkins was merely “Bad”. And I agree with your summary of the Ayala debate: “good grief”.

Anyway:
1) Roughly, yes. I’m not familiar with the condensed matter physics episode you refer to. The problem is that fine-tuning isn’t really a scientific problem. All the data are accounted for – what’s the problem? There are no observations that contradict our theories. And yet …

The fine-tuning argument doesn’t need to add the premise that “our fundamental physical theories are finished.” It can get away with the much weaker premise “Non-life-permitting universes/laws/constants dominate the space of possible universes.” Then, the future advance of physics would seem to only add more possibilities. Working through Barrow and Tipler, for example, gives one the inevitable impression that there are oodles of ways to ruin a universe. It’s hard to even imagine how future physical laws could overcome this.

Further, there can be positive (if tentative) reasons to suspect that the future advance of physics will not affect some fine-tuning cases. Consider point A in my post, and apply it to the proton mass. For a physical mechanism to explain the fine tuning of the proton mass, there must be a parameter in the theory with a value in or very near the life permitting range, and a mechanism that sets the proton mass near the new parameter. Now, this could be viewed as simply another astonishing fine-tuning. But more importantly, if such a mass scale existed, then surely we would have seen evidence of it. Particle accelerators can probe these mass scales quite easily. This mass scale isn’t there (unless it’s hidden, somehow). The fundamental mass scale in physics is the planck mass, which is 19 orders of magnitude away from the proton mass.

2) I think inflation is the best example. The rest of the examples in Barrow and Tipler still remain after 2 decades, though researchers like Fred Adams have done some good work in exploring parameter space more thoroughly (see my post on his work). I would bet my iPod that future physics will have something interesting to say about the cosmological constant…

7. Hmmm..interesting…But let me ask a simple question Mr. Barnes…

Can you name one logically possible thing that can explain our supposedly fine-tuned world NOT being FINE TUNED ITSELF…either physical phenomenon or “metaphysical” something….

Cause I think you’ll fail to do this……
You see, we can put it quite simple: every specific fact can be explained only by proposing other specific facts which also beggs the question as its precedent. We may think of explanation process as of infering particular, specific content (explanandum) from other content (explanans). And good explanans cannot be trivial i. e. entail everything. Hence it must entail specific content only (certain sentences AND not the others) The problem is that the meaning of sentence or set of entences is established by set of its/their consequences. These consequences are in fact that meaning. So the meaning of explanans is explandum itself along with other its consequences….. Hence, if explanandum is specific -particularly puzzling -the same can presumably be asserted about explanans…

Now , please, let me explain -what the problem is…
of course the stance above has absurd consequences….cause if consequence is inherent to premise then any inference is trivial and uninformative When I infer B from A I simply analyse A -and indeed true and correct inference is considered trivial by logicians….(paradox of analysis)

Also problem arises with respect to explanation – IF premise INHERES conclusion then VALID Explanans has always either the same or RICHER content than explanandum. In both cases explanans consist of explandum which, technicallly.. makes the explanation tautological -idem per idem…Each explanation, from that point of view is equivalent to explaining red rose by red rose or red rose by a bouquet of rose….

Now here comes the problem, such a dictum makes any rational inquiry (including scientific one) ridiculous..So it is important to avoid formulating our problems in a way that permit such a paradox…AND my Objection to you is as follows: YOU formulate the fine -tuning problem in a way that permits such a paradox, THUS making the problem NOT SOLVABLE AT ALL.

How Come?

Let me show you……

You say:

<>

Now look, what does that mean: Suppose you reduced all physical world to one physical law or one constant. Now, acording to what is written above and in preceding part of your post -this is still not enough……’Cause we can still ask: why that particular constant exist, and not the other? Why that constant has THIS particular value and not the other?

But the problem is that you can always ask these questions regarding ANY proposed explanation… Whatever you postulate as a explanation: multiverse, wave function, physical law or supernatural personal entity: All of these could not exist, or be different….

Consider “single-constant scenario” once again – when you ask about its value, your question is equivalent to asking: “Why does my proposed explanation of fact is such that it is capable of explaining that fact?”. But the purpose of explanation is ,actually, to posses a content allowing to do so. Every explanation is such. Because inference is equivalent of analysis, inferring the fact from its explanation is equivalent to analysing the content of explanation. Hence, if the constant (or anything else) explains the world it has to entail it as a conclusion, an to do this it has to be “tuned” to the conclusion. So to explain “fine-tuning” you have to use another fine tuning. But this is logical circumstance so this is true for ANY explanation. Metaphysical, as well as physical.

Consider, the last mentioned hypothesis: suppose you propose a deity as a world maker. But to make that hypothesis explaining anything you have to make him/her/it disposed to create sentient beings. Deity can not be free -at least not with the respect of life creation -cause free being can choose to do something or not. And we cannot even estimate the probability of him/her/it/ whatever creating the world if deity can do this but is not obliged/required/determine to do this. So god has to be determined to create life.-he/she/it has to be conceived as mind with CERTAIN will to create sentient beings…Or something, that is ,one way or the other inclined to create life………

To put it using terminology from your critique of Ikeda and Jefferys -If you subscribe to “logical possibility” then nearly everything is possible, and you can always propose an alternative for any life-permitting explanations and probably many of them….Which makes your I entailing F…….and because L entails I it also entails F which may affect your critique of Ikeda and Jefferys……

To avoid this -you HAVE to determine what kind of explanation do you consider as satisfactory and WHY? Strictly speaking if you define fine tuning as “determination of something to be directly of indirectly sentient- life-bringing” then FT problem is UNSOLVABLE, because of reasons above. But if you restrict that not all explanations are fine-tuned or at least not to the same degree….then you can choose some explanation……But, you need to specify these restrictions……I would be glad to know what are they…….

Also i would like to point several additional things….

1. Formulation of the fine tuning problem and the question of likelihood of life-friendly-universe

You said on one occasion, that – FT problem is present every time when only small subset of possible universes is life -friendly…..But first off all -what limits of possibility do you propose? Logical? But why? And how will you be able to COUNT the probability?

Look, consider only of universes defined by specific value of one constant ( It is simplified model of any universe “ruled” by finite amount of constants). Logically, or a priori (it is better term here) you can therefore ascribe any value from the range of minus infinity to the range of plus infinity to that constant…….So you can imagine infinitely many universes defined by value of JUST ONE constant. So assuming logical possibility you will always operate on infitely (uncountable infinity) set of universes. Now the problem arises -what is the probability of life-friendly universes? If we name “uncountable infinity as UI and the number of li-fe friendly universes as L, we can define probability of choosing a LF universe from infinite set as L / UI.
Now the problem arises, cause probably….L= UI !!!!!!…….I am not sure but as far as I remember Cantor’s diagonal method applies to uncountable infinite sets and the for any two real numbers R1 And R2 (R1 not equal to R2) there are infinitely (uncountably) many x-es so that R1<x <R2……If I am correct about these (please correct me if i am wrong) then we can argue that if universe is LF at particular spectrum of constant however tiny, then we can think of UI number universes that are LF….For instance, giving example of our universe-even if strong force cannot be 2% more strong for universe to harbor life still between current value of it, and value 1% bigger there is UI of possible particular values of constant…..Given the fact then presumably at least one fine tuning example is such like that we can infer that ther is UI number of life friendly universes hence L=UI. And now comes the problem:

To formulate fine tuning problem you have to determine L/UI , and to establish it as very small <<1. But if L=UI then L/UI= UI/UI…and dyvision infinity per infinity is mathematically forbidden as far as I can remember……You cannot assign ANY value to it….Hence you cannot determine the value L/UI and establish it as low…..So , by definition above you cannot even FORMULATE fine tuning problem……This problem is not only unsolvable -it is unspeakable…….at least unless you provide some mathematical background that avoids or denies my assumptions……

2.Last remark….this time concerning metaphysical themes….Mr. Barnes the fact that certain problem seems to be profound and was analyzed by great minds does not prove its soundness…..Really!….Question "Why there is something rather than nothing?" may sound good but important metaphysical statements must be proved to justify its soundness. Specifically one must prove that there is a possibility of nonexistence of anything i. e. That there is a possibility that set of existent things is empty…..Such a possibility may be disputed, given its presumed internal, performative contradictions ( If nothing exists then there exists the fact that nothing exists, so something exists, so…reductio ad absurdudum)….Also, even if we agree that it is possible that anything does not exists, then why exactly is this possibility preferable to existence of something? Cause nonexistence is simpler? Why? Also one can explaining existence of one thing only proposing existence of the other thing…so existence in general cannot be explained……also using a deity……

To sum up, I believe that you have to formulate the problem of FT in a language of physics, using some mathematical apparatus……..without this…everything you say is of some heuristical value…..but cannot be regarded as a serious attempt to analyze the problem…..You should also address somehow directly or indirectly, problems submitted above…… So define the problem as a physicist, and give up metaphysics…'Cause I can tell you as a philosopher ;D, metaphysics IS SHIT….A noble Shit with important impact on culture but nevertheless shit :D…..When you attempt to operate on extremely abstract ideas with infinite extension, in natural language, then the confusion is very likely to occur……History of metaphysics is set of such attempts, hence it is full of confusions, which makes it full of problems unsolvable by definition…..Hence it is shit ;D

8. ERRATA…I mssed your quotation!!!!

There should be the following text of yours…

<>

9. Dang sorry one more time this time without

“It would be the mother of all coincidences that the only universe permitted by the laws of nature would happen to permit intelligent life. In their classic paper on fine-tuning in 1979, Carr and Rees comment that “even if all apparently anthropic coincidences could be explained [by deeper physical law], it would still be remarkable that the relationships dictated by physical theory happened also to be those propitious for life.”

10. You say:

“It would be the mother of all coincidences that the only universe permitted by the laws of nature would happen to permit intelligent life. In their classic paper on fine-tuning in 1979, Carr and Rees comment that “even if all apparently anthropic coincidences could be explained [by deeper physical law], it would still be remarkable that the relationships dictated by physical theory happened also to be those propitious for life.”

However, if the physical constants were necessary, it would not be a coincidence that this universe contained life, In other words, it would not be possible to have these constants but not life.

But I agree it is weird to suppose that the physical constants can be dictated by logical necessity (this applies to the existence of God too).

Any critique of Smolin multi-verse hypothesis coming? That would be interesting.

11. on June 11, 2012 at 5:18 pm | Reply Brent Meeker

Luke, you quote Vilenkin:

““It is said that an argument is what convinces reasonable men and a proof is what it takes to convince even an unreasonable man. With the proof now in place, cosmologists can no longer hide behind the possibility of a past-eternal universe. There is no escape, they have to face the problem of a cosmic beginning.” (From: Alex Vilenkin, Many Worlds in One)”

but if I’m not mistaken he is referring to a quasi-classical analysis that shows that almost all (in the measure sense) world lines are past incomplete. Which actually provides two escapes. First, even a set of measure zero may be significant in supplying an origin. Second, why would anyone accept as ‘proof’ an analysis that was not based on a quantum theory of spacetime.

12. 1. If a past eternal universe is a set of measure zero, then it would require an infinite amount of fine-tuning. The probability of a past eternal universe is then exactly zero.
2. Some have tried to argue that the Borde-Guth-Vilenkin theorem would still apply in the quantum regime. I can’t really comment on that. The point is that all the evidence points to the universe having a beginning. A quantum theory of gravity has a lot of work to do to save us from a beginning.

13. on June 12, 2012 at 7:44 am | Reply Big Blue Bump

It seems you only comment on string theory as a model for quantum gravity. Are you not familair with other approaches? I would reccomend Ashketar ? http://arxiv.org/pdf/0812.4703v1.pdf
:

“The big bang and the big crunch are naturally replaced by quantum bounces. On the ‘other side’ of the bounce there is again a large universe. General relativity is an excellent approximation to quantum dynamics once the matter density falls below one percent of the Planck density. Thus, LQC successfully meets both the ‘ultra-violet’ and ‘infra-red’ challenges. Furthermore results obtained in a number of models using distinct methods re-enforce one another. One is therefore led to take at least the qualitative findings seriously: Big bang is not the Beginning nor the big crunch the End. Quantum space-times are vastly larger than what general relativity had us believe!
How can the quantum space-times of LQC manage to be significantly larger than those
in general relativity when those in the WDW theory are not? Main departures from the
WDW theory occur due to quantum geometry effects of LQG. There is no fine tuning of
initial conditions, nor a boundary condition at the singularity, postulated from outside.
9
Furthermore, matter can satisfy all the standard energy conditions. Why then does the
LQC singularity resolution not contradict the standard singularity theorems of Penrose,
Hawking and others? These theorems are inapplicable because the left hand side of the
classical Einstein’s equations is modified by the quantum geometry corrections of LQC.
What about the more recent singularity theorems that Borde, Guth and Vilenkin [34] proved in the context of inflation? They do not refer to Einstein’s equations. But, motivated by the eternal inflationary scenario, they assume that the expansion is positive along any past geodesic. Because of the pre-big-bang contracting phase, this assumption is violated in the LQC effective theory.
While the detailed results presented in section III are valid only for these simplest models, partial results have been obtained also in more complicated models indicating that the singularity resolution may be robust.”

14. Response to Part One:
It seems to me you CAN explain away anything using multiverse cosmology. What’s so wrong with saying the watch I found on the heath of the forest was the product of random chance? After all, if it is possible, it must happen SOMEWHERE in the multiverse, right? You can’t tell me that the probability is very low (in this universe), that’s not the point; I can still explain the watch without an intelligent designer. The multiverse can hand-wave anything!
The WAP is also a brain fart, in my opinion. It’s obviously true, but even with the multiverse, it does nothing. When somebody uses it to wave away fine-tuning, I respond, “So God DOES exist; we wouldn’t be here if He didn’t.” My point when I say that, of course, is that the other person is begging the question.

Response to Part Two:
Just a piece of trivia here: Inflation doesn’t help the fine-tuner-denier here: Roger Penrose discovered that the chances of the universe being flat WITHOUT inflation are actually BETTER than with inflation, by a factor of (10^10)^100. If I properly understood your point up there, this actually strengthens Dr. Craig’s argument.
Hmm. I’d think that there is at least one factor that needs to be fine-tuned (to have a universe like this one), that is obviously not related to the others: the low entropy condition at the big bang.
But let’s go deeper: it seems valid to ask why the conditions would be related, rather than otherwise. So we just find ourselves with what I, as a theist, find far more satisfying: the constants are related because this is the most elegant configuration God could organize them in. No, I don’t care for the fine-tuning argument, it is seems too problematic.

15. Part one. As always, the question is not “what can I believe?” but rather “what should I believe?”. The goal of any intellectual inquiry is to find the most likely hypothesis. The fact that a watch would arise by chance somewhere in the multiverse doesn’t change the fact that any rational observer, faced with a watch on a heath, should conclude that the best explanation is a watch maker. If by “explain” we mean “find a highly probable explanation of”, then we can’t explain the watch with a multiverse, since the multiverse doesn’t change the fact that the most likely explanation is a watch-maker. WAP is a selection effect, and is thus *always* relevant to any appraisal of the probability of a hypothesis. https://letterstonature.wordpress.com/2012/08/04/the-traps-of-wap-and-sap/

Part Two. I’ve discussed inflation and entropy at length in my FIne-tuning paper. See http://arxiv.org/pdf/1112.4647v2.pdf , pg 23-32.

The difference between the multiverse and god from a scientific perspective is that the multiverse is a sort of a direct result of a reasonably well tested theory of cosmology and god is not. Inflation has survived every test thrown it so far. It may well fail future tests (the primordial gravitational wave spectrum) but so far it’s well verified by the data. . Inflation is not one theory but a class of theories. According to Guth any successful model of inflation has to have a certain feature, the inflation field must exponentially expand, fast than it decays. If this is so a multiverse is the result. Given that we have multiple tests of inflation and it has passed these tests it looks better than other models including Penrose own model which guess what? results in a cyclic universe which you could consider a multiverse, with the different universes separated in time rather than space.He’s even admitted this is several interviews. In fact as I can see all models of early universe cosmology currently being discussed in conferences are either
multiverse models or cyclic models. But for the purpose of WAP these don’t need to be different.
See here for example Perimeter Institute’s challenges for the early universe;
http://pirsa.org/C11008
I hope anyone interested in the current state of the art will find these videos interesting although I think if you go to other conferences such at the one i.e. NORDITA
this month
http://www.nordita.org/timetables/index.php?confid=2998
You will see that other cyclic models such as LQC or Horava gravity getting more airplay.

• I think that we’re talking past each other, like how I explained, when I first posted here, “Don’t say that it’s improbable to find a watch that was produced by accident, that isn’t the point.” My point was that if it is possible, it is an explanation, plausible and warranted or not.

Another important difference is that this type of multiverse (I was not addressing any particular kind) has a beginning. Why not instead focus on the implications I pointed out, with how inflation must itself be fine-tuned to an even greater extent? In my mind, you’re making a bait-and-switch, and then using that as a spring-board for a false-dichotomy that I poked at the first time I posted.

I understood you correctly, I hope?

17. Luke, I suspect Richard Carrier got his 6 parameters from Martin Rees book entitled “Just 6 numbers”. Here’s the blurb “Just six numbers govern the shape, size and texture of our universe. If their values were only fractionally different, we would not exist; “I believe you said Rees wrote one of the c classic papers on WAP

18. An explanation, maybe, but not an excuse. Rees has picked six of the most important parameters, but they are not the only parameters, not the only important parameters, and most aren’t fundamental. For example, epsilon (helium binding energy as a fraction of rest mass energy) and N (“strength” of gravity) aren’t fundamental constants. Q, Omega and Lambda are cosmological constants, and so usually thought of as initial conditions rather than fundamental parameters of the laws of nature. These are very good examples of parameters that illustrate fine-tuning, and Rees says *just* six numbers to emphasise the remarkable fact that so few parameters are needed to describe many of the gross features of our universe.

Rees did write some of the classic papers on WAP and fine-tuning:

I had the great privilege of meeting him just a few weeks ago. A living legend.

19. George Ellis (http://en.wikipedia.org/wiki/George_Francis_Rayner_Ellis): “A multiverse is implied by some forms of inflation but not others. Inflation is not yet a well defined theory and chaotic inflation is just one variant of it. . . . the key physics involved in chaotic inflation (Coleman-de Luccia tunnelling) is extrapolated from known and tested physics to quite different regimes; that extrapolation is unverified and indeed unverifiable. The physics is hypothetical rather than tested. We are being told that what we have is “known physics -> multiverse”. But the real situation is “known physics -> hypothetical physics -> multiverse” and the first step involves a major extrapolation which may or may not be correct.”

http://arxiv.org/pdf/1112.4647v2.pdf , pg 57 ff.

20. Luke I see a number of problems;’ of what you linked to (page 57 of your paper).
“Even their most
enthusiastic advocate isn’t as certain about the existence of a multiverse as Stenger suggests.”
I’m not quite sure how certain Stenger is suggesting. But Andre Linde said he would bet his life on it, how much more certain can one be? If you’ve met Martin Rees I’d be amazed that you don’t know this, its one of his funniest stories (and he has many). When asked how confident they were of a multiverse, Martin Rees said he’s confident enough to bet his dogs life on it, Andre Linde said he was so sure he’d bet his own life on it and Steven Weinberg said he was confident enough to bet Martin Rees’s dog and Andre Linde’s life.
Another example Leonard Susskind said of the landscape
http://www.edge.org/discourse/landscape.html
“The level of confidence that string theorists have for their theory is based on a web of interconnected pieces of evidence that is so compelling that genuine mathematicians have no doubt about it’s validity… As for Smolin’s speculations about the evolution of the universe, let me say that almost all cosmologists would agree that the universe is reproducing.”
Of course this has no bearing on whether the multiverse is real or not but it does show you claim above is not correct.

The quote form Ellis has the appearance of 2 of serious errors. Perhaps this appearance is due to not showing the full quote, I don’t know. But what I can say is that seems to imply that a multiverse is generated from inflation by assuming the chaotic inflation model is correct. Whilst it’s true that chaotic inflation leads to a multiverse, it is not true that only chaotic inflation leads to an inflationary multiverse, so suggesting that chaotic inflation requires hypothetical physics to give you a multiverse is totally irrelevant.
Chaotic inflation is a model of inflation whereby the initial value of the inflaton field (hopefully Ill spot my spell check changing inflaton field to inflation field this time) is significantly different from one place to the other. Eternal inflation is less to do with how inflation starts but with how inflation ends.
Eternal inflation and chaotic inflation are not the same thing, it’s a common mistake and it appears that Ellis keeps on making it. In fact I think Vilenkin even named Ellis as an example of someone getting this very thing wrong years before your quote , but I don’t recall the reference off the top of my head; ill try and find it later.

As I’m sure you know the original version of inflation “old inflation” proposed by Guth did not work, this was replaced by “new inflation” which was agreed by the community did work. According to Guth:

“Steinhardt [24], and later
that year Vilenkin [25] showed that new inflationary models are generically eternal “
This is important: if new inflation models are generically eternal then a multiverse results, whether chaotic inflation is true or not.
Guth goes on to say : “In fact, in any successful inflationary model the rate of exponential expansion is always much faster than the rate of exponential decay. Therefore, even though the false vacuum is decaying, it never disappears, and in fact the total volume of the false vacuum, once inflation starts, continues to grow exponentially with time, ad infinitum” In his conclusions he states “Next I turned to the question of eternal inflation, claiming that essentially all
Inflationary models are eternal. In my opinion this makes inflation very robust: if it
starts anywhere, at any time in all of eternity, it produces an infinite number of pocket
universes.”
I hope you can see can see that the multiverse is not dependant on chaotic inflation but eternal inflation and the standard model of inflation(new inflation) is according to Guth generically eternal. If you watch the videos form the PI conference it seems to be that both the critics of inflation (Turok, Steinhardt and the supporters Guth, Aguirre, Susskind etc) seem agreed that the multiverse is a consequence of inflation.

So it seems to me there are stronger arguments to suggest inflation leads to a multiverse than simply relying on chaotic inflation, certainly when we survey the literature and look at what’s being said at conferences that is what we find. Does that it make a fact? Certainly not. I’m not saying the multiverse is a fact, but what I am saying is that it cannot be treated equally as god as a scientific idea. The multiverse arises from inflationary theory and inflationary theory is well verified. Sure inflation might fail future tests, maybe Guth and the others have it wrong on the way inflation evolves, perhaps its not generically eternal, that’s possible too. But it’s clear that there is a far more direct route from current physics to a multiverse then there is to god.

Another thing that might be an error in the quote from Ellis is when he says the extrapolation is unverifiable. As I don’t have the full quote I don’t want to say it’s definitely an error. But it is possible to physically test for eternal inflation, see here:
http://arxiv.org/abs/0712.3038
Now perhaps Ellis wasn’t referring to the multiverse in general but some special mechanism in chaotic inflation in which case he might not be in error, but if that’s so, then its irrelevant to the argument about the multiverse, as we’ve seen the inflationary multiverse does not depend upon chaotic inflation.
Lastly the inflationary multiverse (although nto all versions of the multiverse) is falsifiable. If wee detected a blue shift in the power spectrum or a gravitational wave spectrum that had big deviation from scale invariance or if the universe had high positive curvature, I think inflation and the inflationary multiverse with it would collapse. Can’t think of a similarly set of falsifiable predictions from the god camp.
Perhaps you could answer the key question Luke, do you agree or not the multiverse is more grounded in current cosmology than god is? Yes or no?

21. Paradox, you seem to be stating the multiverse has a beginning as an unambiguous fact. As far as I can see we have a number of claims in the literature that are conflicting. There’s BGV which states eternal inflation can’t avoid singularities, but of course that says nothing about whether singularities are real or as many would state an artifact of applying GR in a realm way beyond what is justified. Quantum theorists such as Ashekatr have pointed out BGV is violated in LQC.
http://arxiv.org/abs/0812.4703

Others such as Nomura argue the multiverse can not have a beginning or end.

http://arxiv.org/abs/1205.5550
Note Guth was consulted on this paper which came out a few months ago.
It seems to me if we are going to be doing science we should certainly pay attention to theorists, and we may call one idea more plausible than another based on theory. But we need some sort of empirical test to say something as unambiguous as the multiverse has a beginning and at the moment the only thing I can think of is the phenomenological programme for a matter bounce http://www.researchgate.net/publication/45885346_Loop_quantum_gravity_and_the_CMB_toward_pre-Big_Bounce_cosmology
This if confirmed would if anything would show that any beginning that we get from general relativistic theories such as BGV is not to be trusted. If it is falsified then we are back to the drawing board and still unclear how to treat singularities.
Note also in LQC any initial condition leads to inflation which is not true in GR. I believe example the difference in prior probabilities for inflation are 10^85 against in GR but 1/1 in LQC.

• Your comment described the Multiverse proposed by Alexander Vilenkin, which falls under the BGV Theorem. If we live in his multiverse, it had a beginning.
Try to stay on topic, and remember that when I said “I was not addressing any particular kind,” I was talking about how any given multiverse requires that it be possible for a watch to exist without a Designer, even if we consider it unlikely.

Now why not to address my comment on the implications of inflation?

22. AN interesting paper just out here: “We found that soon after the onset of the inflation, the total entanglement entropy rapidly decreases to a minimum, and after that it rises monotonically throughout the remainder of the inflation and the radiation epochs. This indicates that the universe does not need to begin with an extremely low entropy; its smallness can be naturally induced by the dynamics of inflation itself.”
http://arxiv.org/abs/1212.1087

23. Paradox, since Luke moderates his comments and there can be a while between a comment is made and it appearing on the blog. I’m going to presume you didn’t read my comment dated Dec 5th, because your reply doesn’t address anything I said in it. Perhaps you could take a read and you’ll see my comments do respond to what you said.
Moreover perhaps you could respond to the more general point, being made on my post Nov 30th rather than simply ignoring it.

• I did reply to your Dec.5th post, and I did give comment on what you said. You complained that “I claim that the beginning of the multiverse was an indisputable fact,” and I explained that I said no such thing. The LQC is not Vilenkin’s multiverse, so commenting on that was irrelevant (it has nothing to do with what you described in your first reply), as I was not talking about THAT kind of multiverse. The model that you first described was an “Eternal Inflation” proposed by Alexander Vilenkin (though by his own admission, it is a type of Chaotic Inflation), the LQC was not. Your accusation is completely inaccurate.
Again, why not stay on topic with what I first brought up? What did I first bring up? How inflation must be fine-tuned to an even greater extent than what people have attempted to use it to avoid: the fine-tuning of dark energy.

Why should I have replied to Nov.30, when that one was for Luke? I will intentionally act thoughtless about this, as these points that I picked up are probably not what you were talking about. But let me see if I understand what you are saying:
1- How confident cosmologists are about the multiverse is not what I was touching down on, and has no concern for me. If the theses that (i) an infinite past is logically impossible, and (ii) material reality is contingent are correct, the god-hypothesis goes on unscathed by the multiverse hype the bouncing universe hype having been eliminated. As I am undertaking the project, this is irrelevant.
2- Eternal inflation, as in future-eternal, or past-eternal? If past-eternal, the question falls onto the to theses I proposed at problem #1. Vilenkin’s model falls under his theorem, and I was not attempting to address other models. So what?
3(?)- You imply here that the inflation models actually do have beginnings, even though they never end. That isn’t my problem. I think I have the right to ask what caused inflation in the first place? We come to an Uncaused First Cause, but the question of whether it is an intelligent thing or not has yet to be resolved. Unless you deny causality (inflation is uncaused), you’ve acknowledged that God exists, you are now only disputing that God has a mind. If the pseudo-vacuum that inflation starts in is the Uncaused First Cause, then the pseudo-vacuum is God.
4- The God-hypothesis is not a scientific proposition in the first place! We need a falsification based on other things that cannot be tested by science, if we want to falsify it. The Argument from Evil is a preferred one.

24. Pareadox I think you have the impression that either eternal inflation is true or LQC is true but I don’t see that. Ive even discussed this with Martin Bojowald personally and he doesn’t see why that would be the case either. The fact is if eternal inflation has a singularity at the beginning then that still needs to be addressed in quantum gravity, its not as if quantum gravity can simply be forgotten amount because of the BGV. In fact the BGV paper specifically states the boundary of the inflating regime needs some other physics to describe it.
Are you suggesting that inflation was created to deal with the value of dark energy? Maybe I have misunderstood your comment. But ff so this is clearly false , inflation was invented to deal with the magnetic monopole problem only. This was at a time when there was no knowledge of dark energy. Moreover LQC predicts inflation so even had it not been invented by Guth or if dark energy hadn’t been discovered it seems we stil would have found ourselves confronted with this phenomenon.
I have provided a link to paper that gives a possibility to explain the low entropy issue you raise purely through inflationary dynamics. Penrose himself has his own suggestion of how to do this so I don’t see nay reason to suggest these problems are insoluable. Also you should read this paper in nature from Rovelli arguing there is no need for any fine tuning of lambda.
http://www.nature.com/nature/journal/v466/n7304/full/466321a.html
So it doesn’t seem the situation is as clear cut as people like Susskind suggest.

The idea that the cause of inflation has to be some kind of god, if that’s what you are implying seem absurd to me. Inflation arises naturally out of a quantum bounce. No fine tuning needed, this is the conclusion of the paper is referred to above. Of course they may be wrong and LCQ could be dead end, but to suggest that it has to be a god seems not justified to me.

• I have no such impression of the sort! I referenced the LQC model to make the point that my first comment had nothing to do with any PARTICULAR kind of multiverse; my first comment was that a multiverse allows us to claim that nothing is designed.
My second comment was on the implications inflation, which requires a greater degree of fine-tuning than some people attempt to explain-away with it. If your author is right, you can forget the second comment.
My third comment references both the LQC and the Eternal Inflation model because you decided to bring up how inflation has “more evidence than the god-hypothesis”, to which I returned, “under the ALEXANDER VILENKIN MULTIVERSE, we need an external cause, and something to fine-tune inflation (implying that the cause is intelligent).”
My fourth comment was an attempt to 1) Clarify what I had said, since you thought that my reply to your post of December Fifth had nothing to do with what you said; 2) See if I could understand the perspective that you leveled with Luke, which you asked for a response to; and 3) Explain how your perspective relates to what I have been arguing for.
So, I referenced the LQC and Eternal Inflation hypotheses, but I do not act like they are the only theories in town; they are representatives of the Multiverse and Bouncing Universe models.
The BGV paper states that the only important factor is that the universe has an expansion-rate of greater than zero for the average of its history. The need for “other physics” so to speak, is necessary in order to avoid a beginning. (“Thus, we need physics other than inflation in order to describe the past boundary of the inflating region of space time.” [bold mine.] If I am interpreting this correctly, inflation itself has a beginning, but anything before that might not, if there IS something “before”.)

No, you misunderstood. It was also purposed to help explain the flatness problem and the horizon problem, but those are irrelevant. What I was saying is that some theorists have attempted to use inflation in order to do away with the apparent fine-tuning of Lambda.

If an infinite past is logically impossible, then even if inflation is demanded by the LQC (and not-fine-tuned), and this model is correct, it still follows that there is an external cause of the universe (back to the God-hypothesis). I don’t use the BGV Theorem to prove the logical impossibility of this thesis either, so please don’t think I’m over-using it!
Now, this is bi-faceted. The first facet was the one I originally brought up, which was focusing exclusively on the Eternal Inflation model proposed by Alexander Vilenkin. If we live in a universe based on Alexander’s model, the BGV applies, and the universe had a beginning, even if it is logically possible for the past to be infinite.
The second facet was raised by you, in your latest comment, and involves both models. You say that inflation might naturally arise from a quantum bounce. There are some big problems in what you are saying. First, is quantum mechanics the Uncaused First Cause, or does quantum mechanics have a beginning (you can see where I am going)? Second, is quantum mechanics Hidden Variable, Many-World, Copenhagen, or what? Each model has important implications for your proposed explanation.

Is there any reason you continue to add more and more subject matter? Most of what I said after the end of my first post here should tell you that I wouldn’t give a notice if the Fine-Tuning argument were to disappear over night.