Archive for the ‘fine tuning’ Category

I’ve spent a lot of time critiquing articles on the fine-tuning of the universe for intelligent life. I should really give the other side of the story. Below are some of the good ones, ranging from popular level books to technical articles. I’ve given my recommendations for popular cosmology books here.

Books – Popular-level

  • Just Six Numbers, Martin Rees – Highly recommended, with a strong focus on cosmology and astrophysics, as you’d expect from the Astronomer Royal. Rees gives a clear exposition of modern cosmology, including inflation, and ends up giving a cogent defence of the multiverse.
  • The Goldilocks Enigma, Paul Davies – Davies is an excellent writer and has long been an important contributor to this field. His discussion of the physics is very good, and includes a description of the Higgs mechanism. When he strays into metaphysics, he is thorough and thoughtful, even when he is defending conclusions that I don’t agree with.
  • The Cosmic Landscape: String Theory and the Illusion of Intelligent Design, Leonard Susskind – I’ve reviewed this book in detail in a previous blog posts. Highly recommended. I can also recommend his many lectures on YouTube.
  • Constants of Nature, John Barrow – A discussion of the physics behind the constants of nature. An excellent presentation of modern physics, cosmology and their relationship to mathematics, which includes a chapter on the anthropic principle and a discussion of the multiverse.
  • Cosmology: The Science of the Universe, Edward Harrison – My favourite cosmology introduction. The entire book is worth reading, not least the sections on life in the universe and the multiverse.
  • At Home in the Universe, John Wheeler – A thoughtful and wonderfully written collection of essays, some of which touch on matters anthropic.

I haven’t read Brian Greene’s book on the multiverse but I’ve read his other books and they’re excellent. Stephen Hawking discusses fine-tuning in A Brief History of Time and the Grand Design. As usual, read anything by Sean Carroll, Frank Wilczek, and Alex Vilenkin.

Books – Advanced

  • The Cosmological Anthropic Principle, Barrow and Tipler – still the standard in the field. Even if you can’t follow the equations in the middle chapters, it’s still worth a read as the discussion is quite clear. Gets a bit speculative in the final chapters, but its fairly obvious where to apply your grain of salt.
  • Universe or Multiverse (Edited by Bernard Carr) – the new standard. A great collection of papers by most of the experts in the field. Special mention goes to the papers by Weinberg, Wilczek, Aguirre, and Hogan.

Scientific Review Articles

The field of fine-tuning grew out of the so-called “Large numbers hypothesis” of Paul Dirac, which is owes a lot to Weyl and is further discussed by Eddington, Gamow and others. These discussions evolve into fine-tuning when Dicke explains them using the anthropic principle. Dicke’s method is examined and expanded in these classic papers of the field: (more…)

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It’s always a nervous moment when, as a scientist, you discover that a documentary has been made on one of your favourite topics. Science journalism is rather hit and miss. So it was when the Australian Broadcasting Corporation (ABC), our public TV network, aired a documentary about the fine-tuning of the universe for intelligent life as part of their Catalyst science series. (I’ve mentioned my fine-tuning review paper enough, haven’t I?).

The program can be watched on ABC iView. (International readers – does this work for you?). It was hosted by Dr Graham Phillips, who has a PhD in Astrophysics. The preview I saw last week was promising. All the right people’s heads were appearing – Sean Carroll, Brian Greene, Paul Davies, Leonard Susskind, Lawrence Krauss, Charley Lineweaver. John Wheeler even got a mention.

Overall – surprisingly OK. They got the basic science of fine-tuning correct. Phillips summarises fine-tuning as:

When scientists look far into the heavens or deeply down into the forces of nature, they see something deeply mysterious. If some of the laws that govern our cosmos were only slightly different, intelligent life simply couldn’t exist. It appears that the universe has been fine-tuned so that intelligent beings like you and me could be here.

Not bad, though I’m not sure why it needed to be accompanied by such ominous music. There is a possibility for misunderstanding, however. Fine-tuning is a technical term in physics that roughly means extreme sensitivity of some “output” to the “input”. For example, if some theory requires an unexplained coincidence between two free parameters, then the “fine-tuning” of the theory required to explain the data counts against that theory. “Fine-tuned” does not mean “chosen by an intelligent being” or “designed”. It’s a metaphor.

Ten minutes in, the only actual case of fine-tuning that had been mentioned was the existence of inhomogeneities in the early universe. Sean Carroll:

If the big bang had been completely smooth, it would just stay completely smooth and the history of the universe would be very, very boring. It would just get more and more dilute but you would never make stars, you would never make galaxies or clusters of galaxies. So the potential for interesting complex creatures like you and me would be there, but it would never actually come to pass. So we’re very glad that there was at least some fluctuation in the early universe.

Paul Davies then discussed the fact that there not only need to be such fluctuations, but they need to be not-too-big and not-too-small. Here’s the scientific paper, if you’re interested.

The documentary also has a cogent discussion of the cosmological constant problem – the “mother of all fine-tunings” – and the fine-tuning of the Higgs field, which is related to the hierarchy problem. Unfortunately, Phillips calls it “The God Particle” because “it gives substance to all nature’s other particles”. Groan.

Once we move beyond the science of fine-tuning, however, things get a bit more sketchy.

The Multiverse

Leonard Susskind opens the section on the multiverse by stating that the multiverse is, in his opinion, the only explanation available for the fine-tuning of the universe for intelligent life. At this point, both the defence and the prosecution could have done more.

Possibilities are cheap. Sean Carroll appears on screen to say “Aliens could have created our universe” and then is cut off. We are told that if we just suppose there is a multiverse, the problems of fine-tuning are solved. This isn’t the full story on two counts – the multiverse isn’t a mere possibility, and it doesn’t automatically solve the fine-tuning problem. (more…)

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A commenter over at my post “Got a cosmology question?” asks:

Someone told me “there is not a single paper which finds fine tuning that has allowed multivariation”. Can you please refute this?

Incidentally, cosmology questions are still very welcome over there.

“Multivariation” is not a word, but in this context presumably means varying more than one variable at a time. There is an objection to fine-tuning that goes like this: all the fine-tuning cases involve varying one variable only, keeping all other variables fixed at their value in our universe, and then calculating the life-permitting range on that one variable. But, if you let more than one variable vary at a time, there turns out to be a range of life-permitting universes. So the universe is not fine-tuned for life.

This is a myth. The claim quoted by our questioner is totally wrong. The vast majority of fine-tuning/anthropic papers, from the very earliest papers in the 70’s until today, vary many parameters1. I’ve addressed these issues at length in my review paper. I’ll summarise some of that article here.

The very thing that started this whole field was physicists noting coincidences between the values of a number of different constants and the requirements for life. Carter’s classic 1974 paper “Large number coincidences and the anthropic principle in cosmology” notes that in order for the universe to have both radiative and convective stars we must have (in more modern notation to his equation 15, but it’s the same equation),

\alpha_G^{1/2} \approx \alpha^6 \beta^2

where, in Planck units, \alpha_G = m_{proton}^2\alpha = e^2\beta = m_{electron}/m_{proton}, and e is the charge on the electron. (Interestingly, Barrow and Tipler show that the same condition must hold for stars emit photons with the right energy to power chemical reactions e.g. photosynthesis.) Similarly for cosmological cases: for the universe to live long enough for stars to live and die, we must have,

|\kappa| \lesssim \left( \frac{\eta^2}{m_{proton}} \right)^{1/3} m_{proton}^3

where \kappa is related to the curvature of space and \eta is roughly the baryon to photon ratio.

This continues in the classic anthropic papers. Carr and Rees (1977) show that to have hydrogen to power stars left over from big bang nucleosynthesis, and to have supernovae distribute heavy elements, we must have (in Planck units, rearranging their equation 61),

m_{electron}^{-3/2} \sim g_w

where g_w is the weak coupling constant.

Barrow and Tipler’s “The Anthropic Cosmological Principle” shows that, for carbon and larger elements to be stable, we must have:

\alpha_s \lesssim 0.3 \alpha ^{1/2}

where \alpha_s is the strong force coupling constant (evaluated at m_Z, if you’re interested).

The whole point of these relations and more like them, which the early anthropic literature is entirely concerned with, is that they relate a number of different physical parameters. There are approximations in these calculations – they are order-of-magnitude – but this usually involves assuming that a dimensionless mathematical constant is approximately one. At most, a parameter may be assumed to be in a certain regime. For example, one may assume that \alpha and \beta are small (much less than one) in order to make an approximation (e.g. that the nucleus is much heavier than the electron, and the electron orbits non-relativistically). These approximations are entirely justified in an anthropic calculation, because we have other anthropic limits that are known to (not merely assumed to) involve one variable – e.g. if \beta is large, all solids are unstable to melting, and if \alpha is large then all atoms are unstable. See section 4.8 of my paper for more information and references.

More modern papers almost always vary many variables. Examples abound. Below is figure 2 from my paper, which shows Figures from Barr and Khan and Tegmark, Aguirre, Rees and Wilczek. (Seriously, people … Wilczek is a Nobel prize winning particle physicist and Martin Rees is the Astronomer Royal and former president of the Royal Society. These people know what they are doing.)

figure2 from my paperThe top two panels show the anthropic limits on the up-quark mass (x axis) and down-quark mass (y axis). 9 anthropic limits are shown. The life-permitting region is the green triangle in the top right plot. The lower two panels show cosmological limits on the cosmological constant (energy density) \rho_\Lambda, primordial inhomogeneity Q, and the matter density per CMB photon. Tegmark et al. derive from cosmology 8 anthropic constraints on the 7 dimensional parameter space (\alpha, \beta, m_{proton}, \rho_\Lambda, Q, \xi,\xi_{baryon}). Tegmark and Rees (1997) derive the following anthropic constraint on the primordial inhomogeneity Q:

equation for Q(1)

Needless to say, there is more than one variable being investigated here. For more examples, see Figures 6, 7 (from Hogan), 8 (from Jaffe et al.) and 9 (from Tegmark) of my paper. The reason that the plots above only show two parameters at a time is because your screen is two dimensional. The equations and calculations from which these plots are constructed take into account many more variables than can be plotted on two axes.

This myth may have started because, when fine-tuning is presented to lay audiences, it is often illustrated using one-parameter limits. Martin Rees, for example, does this in his excellent book “Just Six Numbers“. Rees knows that the limits involve more than one parameter – he derived many of those limits. But equation (1) above would be far too intimidating in a popular level book.

My paper lists about 200 publications relevant to the field. I can only think of a handful that only vary one parameter. The scientific literature does not simply vary one parameter at a time when investigating life-permitting universes. This is a myth, born of (at best) complete ignorance.


Postscript: The questioner’s discussion revolves around the article of Harnik, Kribs & Perez (2006) on a universe without weak interactions. It’s a very clever article. Their weakless universe requires “judicious parameter adjustment” and so is also fine-tuned. Remember that fine-tuning doesn’t claim that our universe is uniquely life-permitting, but rather that life-permitting universes are rare in the set of possible universe. Thus, the weakless universe is not a counterexample to fine-tuning. There are also concerns about galaxy formation and oxygen production. See the end of Section 4.8 of my paper for a discussion.


1. Even if fine-tuning calculations varied only one parameter, it wouldn’t follow that fine-tuning is false. Opening up more parameter space in which life can form will also open up more parameter space in which life cannot form. As Richard Dawkins (1986) rightly said: “however many ways there may be of being alive, it is certain that there are vastly more ways of being dead, or rather not alive.” For more, see section 4.2.2 of my paper.

More of my posts on fine-tuning are here.

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Beginning with Hugh Ross, I undertook to critique various articles on the fine-tuning of the universe for intelligent life that I deemed to be woeful, or at least in need of correction. A list of previous critiques can be found here. I generally looked for published work, as correcting every blog post, forum or YouTube comment is a sure road to insanity. I was looking to maximise prestige of publication, “magic bullet” aspirations and wrongness about fine-tuning. I may have a new record holder.

It’s an article published in the prestigious British Journal for the Philosophy of Science by a professor of philosophy who has written books like “Introduction to the Philosophy of Science”. It claims to expose the “philosophical naivete and mathematical sloppiness on the part of the astrophysicists who are smitten with [fine-tuning]”. The numbers, we are told, have been “doctored” by a practice that is “shrewdly self-advantageous to the point of being seriously misleading” in support of a “slickly-packaged argument” with an “ulterior theological agenda”. The situation is serious, as [cue dramatic music] … “the fudging is insidious”. (Take a moment to imagine the Emperor from Star Wars saying that phrase. I’ll wait.)

It will be my task this post to demonstrate that the article “The Revenge of Pythagoras: How a Mathematical Sharp Practice Undermines the Contemporary Design Argument in Astrophysical Cosmology” (hereafter TROP, available here) by Robert Klee does not understand the first thing about the fine-tuning of the universe for intelligent life – its definition. Once a simple distinction is made regarding the role that Order of Magnitude (OoM) calculations  play in fine-tuning arguments, the article will be seen to be utterly irrelevant to the topic it claims to address.

Note well: Klee’s ultimate target is the design argument for the existence of God. In critiquing Klee, I am not attempting to defend that argument. I’m interested in the science, and Klee gets the science wrong.

Warning Signs

Klee, a philosopher with one refereed publication related to physics (the one in question), is about to accuse the following physicists of a rather basic mathematical error: Arthur Eddington, Paul Dirac, Hermann Weyl, Robert Dicke, Brandon Carter, Hermann Bondi, Bernard Carr, Martin Rees, Paul Davies, John Barrow, Frank Tipler1, Alan Lightman, William H. Press and Fred Hoyle. Even John Wheeler doesn’t escape Klee’s critical eye. That is quite a roll call. Eddington, Dirac, Weyl, Bondi, Rees, Hoyle and Wheeler are amongst the greatest scientists of the 20th century. The rest have had distinguished careers in their respective fields. They are not all astrophysicists, incidentally.

That fact should put us on edge when reading Klee’s article. He may, of course, be correct. But he is a philosopher up against something of a physicist dream team.

Klee’s Claim

The main claim of TROP is that fine-tuning is “infected with a mathematically sharp practice: the concepts of two numbers being of the same order of magnitude, and of being within an order of each other, have been stretched from their proper meanings so as to doctor the numbers”. The centrepiece of TROP is an examination of the calculations of Carr and Rees (1979, hereafter CR79) – “[this] is a foundational document in the area, and if the sharp practice infests this paper, then we have uncovered it right where it could be expected to have the most harmful influence”.

CR79 derives OoM equations for the levels of physical structure in the universe, from the Planck scale to nuclei to atoms to humans to planets to stars to galaxies to the whole universe. They claim that just a few physical constants determine all of these scales, to within an order of magnitude. Table 1 of TROP shows a comparison of CR79’s calculations to the “Actual Value”.

Klee notes that only 8 of the 14 cases fall within a factor of 10. Hence “42.8%” of these cases are “more than 1 order magnitude off from exact precision”. The mean of all the accuracies is “19.23328, over 1 order of magnitude to the high side”. Klee concludes that “[t]hese statistical facts reveal the exaggerated nature of the claim that the formulae Carr and Rees devise determine ‘to an order of magnitude’ the mass and length scales of every kind of stable material system in the universe”. Further examples are gleaned from Paul Davies’ 1982 book “The Accidental Universe”, and his “rudimentary” attempt to justify “the sharp practice” as useful approximations is dismissed as ignoring the fact that these numbers are still “off from exact precision – exact fine tuning”.

And there it is …

I’ll catalogue some of Klee’s mathematical, physical and astrophysical blunders in a later section, but first let me make good on my promise from the introduction – to demonstrate that this paper doesn’t understand the definition of fine-tuning. The misunderstanding is found throughout the paper, but is most clearly seen in the passage I quoted above:

[Davies’] attempted justification [of an order of magnitude calculation] fails. 10^2 is still a factor of 100 off from exact precision – exact fine-tuning – no matter how small a fraction of some other number it may be [emphasis added].

Klee thinks that fine-tuning refers to the precision of these OoM calculations: “exact precision” = “exact fine-tuning”. Klee thinks that, by pointing about that these OoM approximations are not exact and sometimes off by more than a factor of 10, he has shown that the universe is not as fine-tuned as those “astrophysicists” claim.

Wrong. Totally wrong. (more…)

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Let’s begin by quoting from Radford Neal:

There is a large literature on the Anthropic Principle, much of it too confused to address.

I’ve previously quoted John Leslie:

The ways in which ‘anthropic’ reasoning can be misunderstood form a long and dreary list.

My goal in this post is to go back to the original sources to try to understand the anthropic principle.

Carter’s WAP

Let’s start with the definitions given by Brandon Carter in the original anthropic principle paper:

Weak Anthropic Principle (WAP): We must be prepared to take account of the fact that our location in the universe is necessarily privileged to the extent of being compatible with our existence as observers.

Carter’s illustration of WAP is the key to understanding what he means. Carter considers the following coincidence: (more…)

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I recently posted on Arxiv a paper titled “The Fine-Tuning of the Universe for Intelligent Life”. A slightly shortened version has been accepted for publication in Publications of the Astronomical Society of Australia. The paper is primarily a review of the scientific literature, but uses as a foil Victor Stenger’s recent book “The Fallacy of Fine-Tuning: Why the Universe Is Not Designed for Us” (FoFT). Stenger has since replied to my criticisms. The following is my reply to his reply to my article criticising his book which criticises fine-tuning. Everybody got that?

A few points before I get into details:

  • There isn’t much in this post that wasn’t in my original article. I write this to summarise the important bits.
  • “Barnes does not challenge my basic conclusions.” Not even close. Re-read.
  • “Barnes seems to want me to reduce this to maybe 1-5 percent.” Nope. I didn’t say or imply such a figure anywhere in my article. On the contrary, the cosmological constant alone gives 10^{-120}. The Higgs vev is fine-tuned to 10^{-17}. The triple alpha process plausibly puts constraints of order 10^{-5} on the fine-structure constant. The “famous fine-tuning problem” of inflation is 10^{-11} (Turok, 2002). The fine-tuning implied by entropy is 1 in 10^{10^{123}} according to Penrose. For more examples, see my article. Or just pull a number out of nowhere and attribute it to me.
  • “He fails to explain why my simplifications are inadequate for my purposes.” Red herring. My issue is not oversimplification. I do not criticise the level of sophistication of Stenger’s arguments (with one exception – see my discussion of entropy in cosmology below). Stenger’s arguments do not fail for a lack of technical precision. Neither does the technical level of my arguments render them “irrelevant”.

Point of View Invariance (PoVI)

A major claim of my response (Section 4.1) to FoFT is that Stenger equivocates on the terms symmetry and PoVI. They are not synonymous. For example, in Lagrangian dynamics, PoVI is a feature of the entire Lagrangian formalism and holds for any Lagrangian and any (sufficiently smooth) coordinate transformation. A symmetry is a property of a particular Lagrangian, and is associated with a particular (family of) coordinate transformation. All Lagrangians are POVI, but only certain, special Lagrangians – and thus only certain, special physical systems – are symmetric. Stenger replies:

“PoVI is a necessary principle, but it does not by itself determine all the laws of physics. There are choices of what transformations are considered and any models developed must be tested against the data. However, it is well established, and certainly not my creation, that conservation principles and much more follow from symmetry principles.”

Note how a discussion of PoVI segues into a discussion of symmetry with no attempt to justify treating the two as synonymous, or giving an argument for why one follows from the other.

Of course conservation principles follow from symmetry principles – that’s Noether’s theorem. It’s perfectly true that “if [physicists] are to maintain the notion that there is no special point in space, then they can’t suggest a model that violates momentum conservation”. The issue is not the truth of the conditional, but the necessary truth of the antecedent. Physicists are not free to propose a model which is time-translation invariant and fails to conserve energy1. But we are free to propose a model that isn’t time-translation invariant without fear of subjectivity.

And we have! Stenger says: “But no physicist is going to propose a model that depends on his location and his point of view.” This is precisely what cosmologists have been doing since 1922. The Lagrangian that best describes the observable universe as a whole is not time-translation invariant. It’s right there in the Robertson-Walker metric: a(t). The predictions of the model depend on the time at which the universe is observed, and thus the universe does not conserve energy. Neither does it wallow in subjectivity.

Watch closely as Stenger gives the whole game away: (more…)

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I’m a great fan a popular science books, particularly when the topic is cosmology or fundamental physics. Susskind’s “The Cosmic Landscape” was particularly enjoyable, though I will take issue with a few things in later posts. For now, here are a few highlights:

I love a good illustration:

A rocket-propelled lemon moving away from you might have the color of an orange or even a tomato if it were going fast enough. While its moving toward you, you might mistake it for a lime.

This is simply the Doppler effect, which we’ve all observed for sound as an ambulance drives past. It works for light as well, but you have to be going close to the speed of light. Using the right formula from Einstein’s special relativity, we find that you must fire a lemon at a tenth of the speed of light to make it look red. About the same speed, but moving toward you, will make it look green.

Susskind gives an excellent account of the fine-tuning of the universe for intelligent life.

[T]he Laws of Physics may not only be variable but are almost always deadly. In a sense the laws of nature are like East Coast weather: tremendously variable, almost always awful, but on rare occasions, perfectly lovely. … One theme has threaded its way through our long and winding tour from Feynman diagrams to bubbling universes: our own universe is an extraordinary place that appears to be fantastically well designed for our own existence. This specialness is not something that we can attribute to lucky accidents, which is far too unlikely. The apparent coincidences cry out for an explanation.

In particular, he takes the discussion to the cutting edge of particle physics, discussing the gauge hierarchy problem:

Physicists puzzled for some time about why the top-quark is so heavy, but recently we have come to understand that it’s not the top-quark that is abnormal: it’s the up- and down-quarks that are absurdly light. The fact that they are roughly twenty thousand times lighter than particles like the Z-boson and the W-boson is what needs an explanation. The Standard Model has not provided one. Thus, we can ask what the world would be like is the up- and down-quarks were much heavier than they are. Once again – disaster!

… the cosmological constant problem:

Throughout the years many people, including some of the illustrious names in physics, have tried to explain why the cosmological constant is small or zero. The overwhelming consensus is that these attempts have not been successful.

… fine-tuning of cosmic inflation needed to give the universe the right amount of lumpiness:

A lumpiness of about 10^-5 is essential for life to get a start. But is it easy to arrange this amount of density contrast? The answer is most decidedly no! The various parameters governing the inflating universe must be chosen with great care in order to get the desired result.

… and even supersymmetry:

The biggest threat to life in an exactly supersymmetric universe [has to do] with chemistry. In a supersymmetric universe every fermion has a boson partner with exactly the same mass, and therein lies the trouble. The culprits are the supersymmetric partners of the electron and the photon. These two particles, called the selectron (ugh!) and the photino, conspire to destroy all ordinary atoms. … in a supersymmetric world, an outer electron can emit a photino and turn into a selectron. … That’s a big problem: the selectron, being a boson, is not blocked (by the Pauli exclusion principle) from dropping down to lower energy orbits near the nucleus. … Goodbye to the chemical properties of carbon – and every other molecule needed by life.

Susskind is also clear to distinguish between the landscape of string theory and a multiverse (or megaverse):

The two concepts – Landscape and megaverse [a.k.a. multiverse] – should not be confused. The Landscape is not a real place. Think of it as a list of all the possible designs of hypothetical universes. Each valley represents one such design. … The megaverse, by contrast, is quite real. The pocket universes that fill it are actual existing places, not hypothetical possibilities.

All in all, the Susskind’s book is highly recommended.

Part 2 of my review is here.

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I was just re-reading this post over at Cosmic Variance about a paper by Sean Carroll, which he summarises as:

Our observed universe is highly non-generic, and in the past it was even more non-generic, or “finely tuned.” One way of describing this state of affairs is to say that the early universe had a very low entropy. … The basic argument is an old one, going back to Roger Penrose in the late 1970′s. The advent of inflation in the early 1980′s seemed to change things — it showed how to get a universe just like ours starting from a tiny region of space dominated by “false vacuum energy.” But a more careful analysis shows that inflation doesn’t really change the underlying problem — sure, you can get our universe if you start in the right state, but that state is even more finely-tuned than the conventional Big Bang beginning. We find that inflation is very unlikely, in the sense that a negligibly small fraction of possible universes experience a period of inflation. On the other hand, our universe is unlikely, by exactly the same criterion. So the observable universe didn’t “just happen”; it is either picked out by some general principle, perhaps something to do with the wave function of the universe, or it’s generated dynamically by some process within a larger multiverse. And inflation might end up playing a crucial role in the story. We don’t know yet, but it’s important to lay out the options to help us find our way.

It’s a very nice paper and Sean’s post is also worth a read. What I didn’t notice before was this comment from Peter Coles:

I remember having a lot of discussions with George Ellis way back in the 90s about this issue. I strongly agree that what inflation does is merely to push the fine-tuning problems back to an earlier epoch where they are effectively under the carpet (or beyond the horizon, if you prefer a different metaphor). In fact we were planning to write a sort of spoof of Galileo’s “Dialogue concerning the Two Chief World Systems” featuring characters with names like “Inflatio” and “Anthropicus” …. but never got around to it.

Dear Peter Coles, Please write that paper!!! I’ve been looking through the inflation literature lately and there seems to be an uncomfortably large portion of it devoted to propaganda, arguing that inflation is inevitable and the only possible solution to the problems of the standard hot big bang. A good example is this exchange of papers (one, two and three), where Hollands and Wald face off against Kofman, Linde, and Mukhanov on the issue of whether inflation can explain the low entropy of our universe. The question of whether inflation can be the last word in cosmology (and initial conditions) is in need of clarification.

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A few quick things from around the internet.

1. Our favourite Welsh astrophysicist and supervisor, Geraint Lewis, has been keeping himself busy. He’s appeared on Wikipedia, and even has his own blog: Cosmic Horizons. And he’s presented a lecture titled “The Life of Galaxies on ABC Radio National as part of their Music and the Cosmos event, which manages the most depressing end to a public lecture ever:

They have fuel in their cores which is slowly being used up, and eventually stars will start to turn off. Once they’ve used up all their fuel, they can’t burn any more, they will turn off, they will become black, they will emit no light. At some point in the very dim and distant future there will be one remaining star in our Milky Way galaxy, and at some point that too will run out of fuel and it will become dark and the Milky Way will enter into a night and the night will go on forever.

Well worth a listen.

2. A set of three excellent lectures on gravitational waves from Kip Thorne were delivered as the Pauli Lectures at ETH. Video and audio are available here. The first lecture was for the general public and shows some wonderful recent simulations of colliding black holes. Later lectures were more technical but no less fascinating. I’d almost forgotten how much I like General Relativity.

3. I was recently sent this and I loved it. From herePlan of the City is a new animated film, conceived and directed by Joshua Frankel, about the architecture of New York City blasting off into outer space and resettling on Mars. The film’s visuals are an animated collage combining live action footage, animated elements, illustrations and treated photographs, including photos taken by the Mars rovers Spirit and Opportunity made available to the public domain by the NASA Jet Propulsion Laboratory. Plan of the City was created in collaboration with composer Judd Greensteinand NOW Ensemble, an acclaimed “indie classical” chamber ensemble; the ensemble, including Greenstein, feature prominently in the film as live actors set inside the animated framework.

4. If you’re a sucker for punishment … I was recently invited to give four lectures on the fine-tuning of the universe for intelligent life at the St. Thomas Summer Seminar in Philosophy of Religion in Minnesota. The first and second lectures attempt to cover all of modern physics, astrophysics and cosmology in 2 hours, from the structure of atoms and molecules to planet, star and galaxy formation. The third lecture considers what would happen if we changed the laws of nature. In particular, we find that in many cases, the universe would not be able to evolve and sustain complex, intelligent life. The fourth lecture discusses the multiverse – the idea that the universe that we observe is just one of many, each different. I discuss the most popular multiverse today – the inflationary multiverse – and the challenges that the multiverse faces. The talks are on youtube.

5. Aesop himself couldn’t have invented a fable as obvious as this.

6. If you can get a hold of it, Andy Fabian has written an excellent article titled The Impact of Astronomy, which “assesses the variety and scope of the impact astronomy has on science, technology and society – and why it is so hard to measure”. It describes a number of cases in which astronomy has lead to important advances in other areas, including the development of WiFi and digital cameras.

7. Look at this! And also, a wonderful bit of Fry & Laurie.





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I’ve just finished listening to a debate between philosopher William Lane Craig and cosmologist Lawrence Krauss on the debate topic “Is there evidence for God?”. I have a load of these on my iPod – some are very good (Craig vs Austin Dacey is probably the best), while some represent 2 hours of my life that I’ll never get back. They get a bit repetitive after a while. The debate with Krauss was somewhere in the middle. Craig was polished and concise, presenting the same 5 arguments (contingency, Kalam, fine-tuning, moral, resurrection of Jesus) he’s presented for decades. Krauss was less organised and much less focussed. I’ve responded to some of Craig’s claims elsewhere. I’ll focus on some of what Krauss said.

First and foremost, I’m getting really rather sick of cosmologists talking about universes being created out of nothing. Krauss repeatedly talked about universes coming out of nothing, particles coming out of nothing, different types of nothing, nothing being unstable. This is nonsense. The word nothing is often used loosely – I have nothing in my hand, there’s nothing in the fridge etc. But the proper definition of nothing is “not anything”. Nothing is not a type of something, not a kind of thing. It is the absence of anything.

Some of the best examples of the fallacy of equivocation involve treating the word nothing as if it were a type of something:

  • Margarine is better than nothing.
  • Nothing is better than butter.
  • Thus, margarine is better than butter.

We can uncover the fallacy by simply rephrasing the premises, avoiding the word nothing:

  • It is better to have margarine than to not have anything.
  • There does not exist anything that is better than butter.

The conclusion (margarine is better than butter) does not follow from these premises.

Now let’s look at Krauss’ claims again. Does it make sense to say that there are different types of not anything? That not anything is not stable? This is bollocks. What Krauss is really talking about is the quantum vacuum. The quantum vacuum is a type of something. It has properties. It has energy, it fluctuates, it can cause the expansion of the universe to accelerate, it obeys the (highly non-trivial) equations of quantum field theory. We can describe it. We can calculate, predict and falsify its properties. The quantum vacuum is not nothing. (more…)

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