Reality Conditions

Thursday, April 27, 2006

New Tangled Bank Episode, er, Carnival

I'm arriving late to this, but in case you haven't seen it yet go and check the latest Tangled Bank Science Carnival, which is hosted a long, long time ago on a weblog far, far away called The Inoculated Mind. And, as coturnix recommends, if you can better tilt the monitor away from you to see it...

Wednesday, April 26, 2006

Not fair!

Yesterday I played once more in a match for the University chess team, this time the Second team instead of the Third one. Playing with black on Board 5, the game started as a sort of Grunfeld but quickly left theoretical grounds. In a confused position my opponent blundered and lost a knight, with the possibility of getting the exchange as compensation (so he would end with rook against bishop and knight, a fightable situation). He chose instead to keep the bishop, capture a pawn and try for an attack. This proved to be a mistake as I easily parried the attack and recovered quickly the pawn winning an extra one, at which point with a piece and a pawn down and no compensation he could have resigned straight away. He continued to play for several moves, though, until we reached the following position:

As you see the position holds no hope for White. I have just played 25... Ne4, with the threat of Nf2+ followed by Nd3+ winning the exchange. My opponent replied 26. Qc4, at which my eyes boggled: he is allowing me to make Philidor's mate! I had never before had an opportunity to do Philidor's mate, which is by far the most elegant of the common and recurring patterns of checkmate. After looking once and again at the position to be sure there was no snare in it, I proceeded: 26... Nf2+ 17. Kg1 Nh3+ .......

And my opponent resigned. What a frustration! Not fair.

Monday, April 24, 2006

William Dembski's Theodicy

Followers of the controversy around Intelligent Design will recognize the name of Willam Dembski as one of the leading proponents of this "theory". His fallacious arguments challenging evolution, as well as his distortion of evidence and his deafness to criticsm, have been thoroughly documented in many places (just go to The Panda's Thumb or to Dispatches From the Culture Wars and search the sites for his name). Today I want to address a different aspect of his views. Yesterday I was having a look at the Philosophy Papers Blog and found that there was a new paper by him, entitled:

Christian Theodicy in Light of Genesis and Modern Science

Reading it has made me realize, more than any of the criticisms of him I had read before, how distant is Dembski's worldview from that of the average scientist. Of course Dembski is not a natural scientist by training (as his comrade Behe is) but a mathematician and philosopher. Nevertheless, I would have expected that his general vision of the world would be relatively close to the scientific one, only differing in the question whether examination of life can warrant an inference to a Designer. After all, he accepts the old age of the Earth and even, in some of his moods, common descent. I was wrong. Dembski's worldview is much more closer to that of a medieval theologist.

This article discusses that old chestnut, the problem of evil. My own opinion on the problem of evil is simple: For someone with no previous commitment to religion that examines impartially the evidence for and against it, it is pretty damming evidence against the existence of God. For someone who is already firmly religious, it is not a contradiction to his religion; the claim can always be made that there is a secret and unknowable divine purpose for all the evil and suffering in the world. I think that there is no more the theist can say. Any concrete, explicit rationalization offered for evil will be more or less easily refuted as implausible, and usually, as callous also. But let's not digress and see what rationalization for the evil of the world Dembski offers us.

Dembski's theodicy attributes evil to the Fall. And he is not using the Fall in a metaphorical sense. For Dembski, there was a literal original sin of mankind, in a literally existing uncorrupted enviroment, which is the explanation for all the evils in the world. That's what I meant with a worldview far away from that of a normal scientist! How can Dembski square this with his acceptance of the old age of the Earth and the reality of pain and death in the natural world before the appereance of humans? The story that emerges from his paper, as I understand it, is like follows:

God's original plan for creation is the one documented in Genesis 1, the creation of a perfect uncorrupted world. However God, in his omniscience, knows from before the creation of the world that Adam and Eve would, out of their own choice and with free will, disobey him and sin. So he creates instead a world with natural evil (diseases, death, natural catastrophes, etc):

God disorders the world not only as a matter of justice (to bring justice against human sin as required by God's holiness) but even more significantly as a matter of redemption (to bring humanity to its senses by making us realize the gravity of sin).

When the process of evolution reaches human-like creatures in this already corrupted world, God creates for them an artificial enviroment of apparent perfection (the Garden) and there gives them the magic spark (the Intelligent Designer at work!) that turns them into full human beings, made in God's image and capable of free decisions -and sinning. The Garden looks perfect and uncorrupted for the newly created humans, even though this is a sort of God-induced illusion. Of course, they sin, and after that they "come to their senses" realizing that they are in a corrupted world, and attribute this to their sinning. In a chronological sense they are wrong because the world already contained evil, but trascendentally they are right because the explanation for the evil is their choice of sin. (Dembski compares the situation to Newcomb's paradox).

I am very ignorant of the current state of theology, but it seems to me that this story is a regressive attempt of getting as much as possible in the Bible to be literally true, making the smallest possible concessions to science, even if this requires some weird logical tightrope balancing. I think that a lot of mainstream theology (Catholic, for example) sees the Genesis account as a man-made document, perhaps inspired by God and containing a spiritual message, but with no literal claim to veracity not even in the sense Dembski gives it. And how many theologists believe nowadays that there was an actual, pin-pointable moment of the Fall with cosmic significance? I don't know; perhaps Brandon can enlighten me here. But I hope they are few.

Dembski shows at many other points of the article his preference for a traditional religious stance over a scientific one. For example, he defends the idea that human actions, such as the original sin, can have cosmic consequences because we are "the crown of creation", "alone among physically embodied creatures made in the image of God", and makes the remark that the failure of SETI to detect any other intelligence supports this claim. Again, I believe that mainstream modern theology has no objection in principle to the possibility of extraterrestrial intelligent life, although I am ready to be corrected. (Oddly enough, the footnote for the SETI remark credits as source a public lecture by Michael Chrichton, which is only tangentially about aliens and centered on global warming bashing. Didn't Dembski have any more reputable source for the rather uncontroversial claim that we haven't detected aliens yet?)

In summary, my present impression of Dembski is that he is at heart and by essence a fundamentalist, who differs from young earth creationists in having reluctantly accepted the evidence for the old age of the Earth, but clings to every other element of the fundamentalistic world picture and sees then world much as he possibly can through Biblical lenses instead of through scientific ones.

Sunday, April 23, 2006

Chalmers, Dennett, and the Zombies

I have been rereading David Chalmers' The Conscious Mind, which puts forward the strongest possible case for mind-body dualism. I enjoy reading Chalmers more than any other contemporary philospher except for Dennett and Rorty, and greatly admire his intellectual honesty and clarity of thought. However, I find much more convincing Dennett's theory that consciousness is just a functional property of a highly complex information-processing system such as the brain, than Chalmers elegant defense of dualism. One thing I will try to do in this post is articulate why I am not persuaded by Chalmers.

The most striking thing about Chalmers' view of mind is how close to Dennett's it is in many respects. Contra Searle and other doubters, he argues for a strong form of AI in which any computer, what's more, every physical system that is an implementation of a suitable program (the one neurons in the brain implement, for example) will become conscious. The only point of disagreement with Dennett (except from some minor quibbles) is that for Dennett the conscoiusness is the information processing (IP), while for Chalmers consciousness is an extra fundamental feature of the world, correlated with the IP by contingent laws of nature akin to the fundamental laws of physics. This is the difference which Chalmers makes between "reductive" (bad) and "nonreductive" (good) functionalism.

But what is the cash value of the distinction? If it walks and quacks like a duck, it is a duck. If all and only all IP systems of a certain kind instantiate consciousness, the natural instinct of any scientist will be to apply Occam's Razor and say that consciousness just is the IP. It makes for a simpler worldview, makes science more unified (consciousness doesn't look like the kind of entity that appears in other fundamental physical laws), and dissolves all the paradoxes about epiphenomenalism and phenomenal judgements that trouble Chalmers.

Chalmers would protest that this is "not taking consciousness seriously". The connection between consciousness and IP is natural, not conceptual. One can imagine (concieve, in Chalmers' wording) beings with all the usual IP going on that a normal brain has but with no real, first-person point of view consciousness. This is the (in?)famous "zombie argument", which Chalmers coaches in a lot of modal terminology (possible worlds, primary and secondary intensions, and the like; Richard Chapell has a series of recent posts explaining these concepts). Dennett finds the argument ridiculous and preposterous, but his refutations are less than convincing, because he doesn’t touch what in my opinion are the deep sources of the disagreement between Chalmers and him.

Scientists would, in my opinion, not buy the zombie argument because they see little use for a distinction between a "conceptual" and a "nomological" necessitation of consciousness by physical facts. Is mass conceptually defined as a form of energy, or a distinct thing only nomologically correlated to it? It doesn't matter; as long as we agree in the pysical predictions made this is only a pragmatical question on how to axiomatize pysics. A 19th century pysicist would probably be able to "concieve" mass with no energy; does this prove anything? No; our concepts change and evolve with the growth of scientific knowledge; what is concievable now may become unconcievable later and vice-versa. Concepts are just tools for describing the world, and we can change them and reform them if we need to.

This picture of science, familiar since Quine, is pressupposed by Dennett, but implicitly rejected by Chalmers. When he talks of adding consciousness to the list of fundamental physical properties of the world, and adding the IP-consciousness correlation laws to the list of fundamental laws of nature, he overlooks that physics (despite common talk, even by physicists, even sometimes by me on behalf of convinience) does not provide a list of fundamental properties and a list of fundamental laws. It may provide a fundamental theory or a list of them (currently, they would be the Standard Model + Quantum Field Theory, and General Relativity, although we know that is not the end of the story as quantum gravity is left out) but not a list of fundamental entities the world is made of with a list of contingent laws of nature holding between them. What an entity such like the electromagnetic field is, is defined by what laws of nature it obeys and therefore by its relations with other entities. We can choose to make some features definitional and some others nomological, but that is mostly a matter of convinience and is subject to possible change in light of new knowledge. (This is, by the way, the reason I dislike the ubiquitous talk of “possible worlds” to frame philosophical questions. What counts as a possible world depends on the concepts used to describe them, which are subject to change with scientific progress.) Dennett himself makes the point when (addressing other thought experiments different from the zombie argument, but similar in style) he says:

Smiling demons, cow-sharks, Blockheads, and Swampmen are all, some philosophers think, logically possible, even if they are not nomologically possible, and these philosophers think this is important. I do not. Why should the truth-maker question cast its net this wide? Because, I gather, otherwise its answer doesn't tell us about the essence of the topic in question. But who believes in real essences of this sort nowadays? Not I.

I suspect Chalmers could agree with this with respect to all scientific concepts except consciousness. He would say that the concepts of phenomenal red or of pain cannot be subjected to the redefinitions possible for other scientific concepts. Our knowledge of them is by their intrinsic features (it is essential to pain, that it feels painful, while any functional properties of the state "being in pain" are not essential). This is the way Rorty characterizes the similar disagreement between Nagel and Dennett in his masterful essay "Holism, Intrinsicality, and the Ambition of Trascendence" (for Dennett and his critics). But this shows that all the zombie arguments are question-begging, because to carry any force they must assume that there is something very special about consciousness that distinguishes it from other subjects for science in the first place. A Dennettian would simply deny that the scientific description of consciousness requires concepts different in nature to those used in other areas.

To summarise, we can imagine a dialogue beetween Chalmers and Dennett to proceed like this:

C: We can concieve of zombies, therefore physics and IP do not conceptually entail consciousness, therefore consciousness is not identical to physical IP, even if it is universally correlated with it.

D: But if the correlation is indeed universal, then we better redefine our concept of consciousness to make it identical with physical IP and have a simpler scientific picture.

C: We cannot do that, because our present concept of consciousness captures intrinsic features of it, which cannot be done away with by redefinition.

D: This kind of intrinsic grasp on a concept does not exist anywhere else in science. To assume it does exist for phenomenal concepts is question-begging, because it makes from the start consciousness different from all other things.

Of course, this does not refute Chalmers' dualism; it merely shows that there is no non-circular agument for it. Dennett can still acknowledge the powerful tug of what he calls The Zombie Hunch as an "intuition", while going on to argue that reasons of scientific progress such as simplifying and clearing of "mysteries" our picture of the world speak in favour of not listening to that intuition.

If you want to know more about zombies and their use in philosophy, this resource page is the right place to go.

Thursday, April 20, 2006

The Movie Timeline

Via Pharyngula, I found this amazing project. It is perhaps overly ambitious; how can every single fact shown as true in every movie be recorded in the timeline? Just reading some bits here and there I found several omissions and inaccuracies. But how fun it is! See for example the first six entries:

In the beginning... God created the heavens and the earth (The Bible)

Shortly after the beginning... God subcontracts the fjords to Slartibartfast, a planetary construction engineer from Magrathea (The Hitchhiker's Guide To The Galaxy)

26,000,000,000BC Los Angeles (and everywhere else) - The Earth's crust begins to harden (Adaptation)

A long time ago... Luke Skywalker and Han Solo lead a rebellion against the evil empire(Star Wars)

1 zillion BC October 9: Cavemen discover fire, and the joys of eating dinosaur egg (Caveman, 1981)

65,000,000BC Pangea - A mosquito becomes irrevocably trapped in tree resin (Jurassic Park, 1993)
A meteor strike creates a parallel dimension in which dinosaurs evolve (Super Mario Bros)

Or all the things that happened the year of my birth:

1980 Air passengers are trapped after the pilot, co-pilot and navigator pass out due to poisoned food (Airplane)
USS Nimitz disappears through a temporal vortex, manifesting itself as a storm (The Final Countdown)
Superman throws a terrorist bomb from the Eiffel Tower into space, freeing General Zod from his glass prison (Superman II, 1980)
Richard Collier hypnotises himself in an attempt to travel back in time (Somewhere In Time, 1980)
February 22: US Men's Hockey team of amateur and collegiate players beats USSR no.1 team, is dubbed the 'Miracle On Ice' and goes on to win Olympic gold (Miracle)
May 18: Manchester, England - Joy Division singer Ian Curtis found hanged from apparent suicide in his flat, aged 26 (24 Hour Party People)
July 31: Harry Potter born (Harry Potter and the Chamber of Secrets)

So Harry Potter is only a few months younger than me? Who would have thought it...

Tuesday, April 18, 2006

Sokal must be either laughing or crying

Remember the Sokal affair? When Sokal made his hoax, he was not mainly interested in making the point that "postmodern" critical theory was full of pseudoscientific nonsense. His central aim was to serve as wake-up call for the academic political Left, telling them that endorsement of "relativism" about science was against all the best interests of the Left and robbed critics of the status quo of the weapons offered by fact-based knowledge.

Now, a decade later, sociologist of science Bruno Latour (who was one of the main targets of Sokal) is finally coming to his senses. Too bad it has required years of abuse and misrepresentation of science from the Bush administration to make him realize that:

And yet entire Ph.D programs are still running to make sure that good American kids are learning the hard way that facts are made up, that there is no such thing as natural, unmediated, unbiased access to truth, that we are always the prisoner of language, that we always speak from one standpoint, and so on, while dangerous extremists are using the very same argument of social construction to destroy hard-won evidence that could save our lives.

Sokal, and all the scientists that were on his side, can now say all with one voice: "I told you so!!!!"

You know what sucks?

Answer: To be sitting on my desk, in the middle of the Easter holiday which means all my friends have gone away and leaves me nothing better to do than coming to my empty office to work, with a rapidly growing pile of half-read papers on Quantum Field Theory in de Sitter space on said desk, and (to top it) with a runny nose that prevents all intents of concentrating in samesaid papers by eliciting continuous sneezing and grasping for napkins stolen from the tea room (because all my own Kleenex have long gone to fill the rubbish bin). That sucks.

Oh, but when I Googled "runny nose" to confirm that that was the correct way to spell it, I found this hilarious question among the first results. That almost compensates for it.

Sunday, April 16, 2006

Linking around

Noteworthy links of the week:

A paper contrasting different axiomatic reconstructions of quantum theory, found at the excellent Philosophy of Science Archive.

Week 229 of John Baez's "This Week's Finds in Mathematical Physics" is out.

Lubos Motl criticizes Rovelli et al. on the graviton propagator, making true the second of my three predictions.

If you know who Carl Friedrich Gauss was, the chances are you also have heard a story about how when he was a schoolboy he solved in a few moments a problem about summing an arithmetic progression. Where did this story come from, and is it true? Read here.

Turning to philosophy, a post by Richard of Philosophy, et cetera on Kirpkean semantics has turned into a discussion of David Chalmers' (in)famous "zombie argument" for dualism. (Veeeeery roughly, the argument states that given that we can concieve a physical duplicate of a human being that has no conscious experience, then counsciousness cannot be physical). Chalmers seems to me the most serious and clever defender of dualism in the current philosophical scene, but I don't think his arguments can sustain his conclusions. That, however, is a topic for another post or series of posts. In the menawhile, you can go check Chalmers' homepage, which is full of interesting stuff, including a list of philosophical humour links.

Language Log is collecting lists of "The Four Subjects of X". For example, The Four Subjects of Poetry are:

1. I went out into the woods today, and it made me feel, you know, sort of religious.
2. We're not getting any younger.
3. It sure is cold and lonely (a) without you, honey, or (b) with you, honey.
4. Sadness seems but the other side of the coin of happiness, and vice versa, and in any case the coin is too soon spent, and on what we know not what.

Challenge to my readers: what are The Four Subjects of Quantum Gravity?

My rock star friend points to this amusing animation detailing the differences between Italians and other Europeans; it could equally have been about Argentinians instead of Italians.

Finally, I could not leave without a link the blog post which is likely to become the most commented in all the history of blogging; it has already 835 comments and counting. And it consists in only one word...

Friday, April 14, 2006

Taking back my words

In my previous post, I described the relational interpretation of quantum mechanics and made a criticism to it. I have realized now that my criticism rested on a (rather elementary) mistake. I said:

One criticism that comes to mind is that the relational interpretation is not very clear on which events count as "interactions" or "measurements". In the situation described above, in which system B "measures" system A and changes its state relative to it, at what time does this change occur exactly? From the external point of view no change has occurred: relative to an external observer the whole state has evolved continuously into a superposition. So there is a question that seems real enough, "Exactly when did B's state relative to A change?" but to which quantum mechanics provides no answer and no experiment will ever shed light on. This seems strange; if Rovelli has a good answer to this question, I am not aware of it.

Quantum mechanics does indeed provide no answer for "when did B's state change?" but that is not a problem for the relational interpretation: it's just an ordinary example of the indeterministic nature of QM. Let's spell out more clearly what is going on here. At the beginning system A is (relative to B and to an external observer O) in a superposed state K1 Ia1> + K2 Ia2>. System B is before interacting with A in a state Ib0>, which we can interpret as the default state of a measuring device before a measurement. Now A and B start to interact. Relative to O who does not interact with them, the state of B evolves deterministically into:

IS(t)> = C0(t) Ib0> + C1(t) Ib1> + C2(t) Ib2>

This means that at each time t there is an amplitude C0 for the measuring apparatus B to have failed to detect anything, and amplitudes C1 and C2 for detecting the states<>Ia1> and Ia2>. If B is a "good" measuring device we should expect C0(t) to approach 0 fastly after the beginning of the interaction, and C1(t) and C2(t) to have, at least for large t, the same relative weight that K1 and K2.

According to the relational interpretation, the state of A relative to B will change either to Ia1> or to Ia2> at some time after the interaction started, and the state of B itself relative to A will also change either to Ib1> or to Ib2> at the same time. But we should not expect the relational interpretation to tell us at what time will that happen. We know, from quantum mechanics, what is the probability of the transition having taken place at each time t, as encoded in IS(t)>. And that is all we can know, and being the world indeterministic it is all we can expect to know.

In summary, the mistake I made in the last post was to forget that not only the resulting states of transitions are indeterministic in quantum mechanics, but also the times at which the transitions take place.

There is a thread going on on the Smerlak-Rovelli paper at Physics Forums, where Marcus has some flattering words of praise for this blog.

Thursday, April 13, 2006

Relational Quantum Mechanics

A very interesting paper on the interpretation of quantum mechanics has appeared yesterday:

Relational EPR
Matteo Smerlak, Carlo Rovelli

The article attempts to explain the EPR experiment using the relational interpretation of quantum mechanics championed by Rovelli (presented here and here). The main idea of the relational interpretation is that a quantum state is not an "absolute" description of a system, but only relative to a given observer, and that a same system may be described at the same time by many different states. For example, in the "Wigner’s Friend" version of the Schroedinger Cat paradox, one observer inside a box makes a measurement of a quantum system and sees a definite result, while for a second observer outside the box the whole system including the first observer is still in an indeterminate "superposition" state. The relational interpretation has a simple description of the situation: the state is collapsed relative to the first observer and superposed relative to the second observer. (In contrast, the better known "many worlds" interpretation would say that the "true" state is the superposed one and that the first observer’s impression is a kind of illusion produced by the "branching" of his consciousness. The relational interpretation is more "democratic"; none of the descriptions is privileged.) A key feature of the relational interpretation is that according to it any quantum system can be called an "observer"; counscious beings have no special status, and any interaction can be a "measurement". If system A is first in a superposition state Ia1> + Ia2> (with respect both to a system B and to an external system C) and then interacts only with system B, relative to C the global state may be now Ia1>Ib1> + Ia2>Ib2>, even though relative to B one of the options has “actualized” and the state is now Ia1>Ib1>.

I think this is a quite elegant solution to the measurement problem. It does not involve any change in the testable predictions of QM, unlike the models with a physical wavefunction collapse; it does not involve extra physical baggage like hidden variables models do, and it does not involve the extra ontological baggage of the many worlds interpretation. (From the point of view of the relational interpretation, the many worlds interpretation would seem to privilege as the only "true" state one which is not relative to any particular observer; God’s point of view, so to say. I think that the relationist should deny that there is any such state, like a "wavefunction of the universe". This should have implications for quantum cosmology.) Even more attractive, for me at least, is that the interpretation is not instrumentalistic: quantum mechanics is not merely a tool for calculating and predicting but a true description of how the world works; the description must be done from the "point of view" of some physical system, but there is no privileged choice for the reference system (much like the situation with reference frames in special relativity).

One criticism that comes to mind is that the relational interpretation is not very clear on which events count as "interactions" or "measurements". In the situation described above, in which system B "measures" system A and changes its state relative to it, at what time does this change occur exactly? From the external point of view no change has occurred: relative to an external observer the whole state has evolved continuously into a superposition. So there is a question that seems real enough, "Exactly when did B's state relative to A change?" but to which quantum mechanics provides no answer and no experiment will ever shed light on. This seems strange; if Rovelli has a good answer to this question, I am not aware of it.

As applied to the EPR experiments discussed in this paper, the apparent paradox in the usual formulation of quantum mechanics is that a measurement in system A (which "collapses" and changes its state) can produce an instantaneous change in the state of a system B entangled with A, even if B is spacelike separated from A and so no physical signal can carry the information of the collapse. The solution, using the relational interpretation, is explained in the article in the following way: If observer O makes a measurement on A, then the state of A relative to O changes, and ipso facto the state of B relative to O insofar as B and A are entangled, but this change in the state of B is not problematic as it only reflects the information available to O. The state of B relative to the observer O' who is measuring it remains uncollapsed when O measures A if O and O’'are spacelike separeted. But after O' measures B, when O and O’ meet to compare results (it is stressed that this comparison is also a physical interaction, involving a measurement), they are garanteed to find the correlations predicted by quantum mechanics. Relative to O, the measurement of O' (comparison of results with him) will always yield O' to be in the state of having measured the opposite spin to the one measured by O, if the original state was a singlet.

One noteworthy feature of the paper is that it quotes Wittgenstein! Propositions 1.1, 2.01, 2.011 y 2.0121 of the Tractatus. Not very common in your average physics paper! The reason for me remarking this is that I was fascinated by the Tractatus at one period of my life and organised a reading group for it with some friends. I'm sad to report it only lasted one meeting.

There is an ongoing discussion of this paper at Christine Dantas' blog.

Tuesday, April 11, 2006

Gravitons from LQG

A paper that seems groundbreaking in Loop Quantum Gravity has appeared today:

Graviton propagator in loop quantum gravity
Authors: Eugenio Bianchi, Leonardo Modesto, Carlo Rovelli, Simone Speziale

They claim to compute some components of the graviton propagator from LQG. If the calculation is solid then this makes a big step towards the main problem haunting LQG, the mysterious low energy limit of the theory. I haven't read yet most of the paper, but the list of open issues in the conclusions is huge, so there is still a lot of work to be done.

I make the following predictions: a) Christine will link to the paper in the following hours; b) Lubos will do the same, perhaps a bit later, with a long explanation on how this paper and the whole of LQG are wrong, unphysical, pseudo-scientific, and perhaps even liberal and pro-global warming; c) perhaps Peter will link to it also, even later, gleefully commenting that LQG is doing more progress than string theory and that Lubos is becoming crazy becasue of that.

Quite a book review of A Devil's Chaplain, by Richard Dawkins

So, finally, here is the book review that I failed to compose last week.

A Devil’s Chaplain is the third complete book by Dawkins I have read, after The Selfish Gene and Unweaving the Rainbow, plus some scattered articles and pieces. It does not reach the superb quality of TSG, but I enjoyed it more than UTR. It is a collection of 32 essays divided in 7 sections, originally published over a long period of time and covering a wide range of subjects. The quality ranges from the “pretty averagely good” to the “amazingly outstanding”.

The first section, entitled “Science and Sensibility”, has pieces which can broadly be defined as “philosophical”, or better, “meta-scientific”. Dawkins lampoons relativism about truth, warmly reviews Sokal’s Fashionable Nonsense, ridicules the pseudoscience of crystals, and reflects on some issues relating science and ethics, like animal rights. These essays are generally good and worth reading for Dawkins elegant style and wit, but do not make any remarkable original points. An exception for me was the piece on trial by jury, which makes a good case that the procedure is flawed; although perhaps all the arguments he uses are in fact old and trite, and it’s just that I had never read or reflected on the topic before.

The second section, ”Light Will Be Thrown”, groups five essays on Darwin and evolution, some of which are among the best in the book. The essay that gives its title to the section is a foreword to an edition of The Descent of Man highlighting many interesting aspects of the book and how “alive” it still is. The next essay “Darwin Triumphant” is a brilliant summary of what Dawkins calls “core Darwinism” and defines as

the minimal theory that evolution is guided in adaptively nonrandom directions by the nonrandom survival of small random hereditary changes

Dawkins explores the huge power of this simple idea, explaining how it implies gradualism and how it can give an explanation for evolution when Lamarckism cannot –the refutation of Lamarckism by pure a priori reasoning without mentioning the particular facts about genetics is a beautiful tour de force. Another essay in this section “Son of Moore’s Law” contains the exciting argument that I outlined at the end of my previous post on this book.

The third section “Virus of the Mind”, is –as you might guess from its title- on memes. Dawkins gives the expected clear and entretaining explanations of what memes are, expresses his pleasure at the popularity of the idea and the uses Blackmore, Dennett and others have made of it, but without endorsing their particular theories, something wise in my opinion; I am a geat fan of Dennett but find his reliance on “memes” as explanatory devices in philosophy of mind one of his weakest points. The section also contains a couple of strong attacks on religion, one of them blaming it for 9/11 and other calamities, and one taking issue with Stephen Jay Gould’s conciliatory “nonverlapping magisteria” position on religion and science. I would like to digress into an exposition and evaluation of these opinions (you know how much I like to reflect on the subject) but to keep this review at readable length I resist the temptation and leave it for another day.

Next comes the section “They told me, Heraclitus” with four eulogies on dead people: two on Douglas Adams, a great friend of Dawkins, one on the biologist W.D. Hamilton and one on journalist John Diamond. It is followed by one of the great treats of the book: “Even the Ranks of Tuscany”, a whole section dedicated to reviews of books by Stephen Jay Gould. They show Dawkins’ admiration for Gould’s qualities as a scientist and a writer, together with his merciless criticism of those places where he thought Gould was wrong –most noticeably in the review of Wonderful Life. It also contains the story of the project for signing a joint letter against creationism that they were planning when Gould sadly died.

At the end of this section there is a summary of the disagreement between them on their interpretation of evolution: Dawkins focused on gene selection as the only kind of selection that has explanatory power, while Gould rejected this “reductionism” and emphasized selection and other mechanisms operating at many levels. From my outsider to biology and probably misinformed position, I would like to see the disagreement as more of perspective than substantial. I would like to think that Gould was fascinated by the actual living beings in their wonderful complexity, seeing them as the true subject of study of biology, which led him to speak of genes as mere “book-keeping” devices; while Dawkins feels more the fascination of the explanatory power of the concept of natural selection, and saw that literally it only can be explanatory when applied to genes, thereby viewing Gould’s talk of “book-keeping” as getting things backwards as the “primary movers” are the genes. Perhaps someone with more knowledge of biology can tell me if this interpretation of the controversy is viable, or if there was a more substantial disagreement?

After this climax the next two sections are something of a disappointment. The sixth one, “There is ll Africa and her Prodigies in Us” contains essays on Africa and Dawkins’ relation to the continent, including one with memories of the Leakeys. The last section consists of only one piece, a letter called “Good and Bad Reasons for Believing” that Dawkins wrote for his ten-year old daughter and explains in simple terms the scientific method contrasting it to belief based on authority, tradition or revelation, with the expected examples taken from religion. The girl is twenty-one years old now; I wonder if she has become religious or has followed his father’s exhortations? Dawkins doesn’t say.

In summary, I strongly recommend the book for the second and fifth sections, and mildly recommend it for the rest of them. If you are reluctant to buy the book, many of the essays can be found online here.

Sunday, April 09, 2006

Some things

I have been having problems with my server at home and cannot log into Blogger from there. This explains the scarcity of posting, since I generally try not to blog from my office in the University where I am supposed to be working. If this problem continues I will start to write the posts at home and then post them here at uni.

I went to the theatre to see Lady Windermere's fan a couple of days ago. Though it was the play by Wilde I liked most in reading them, seeing a representation of it has made me change my mind. The funny bits and examples of Wildean wit in it are great; it has one of his most famous lines, "I can resist everything except temptation", as well as one of my own favourites, "Experience is the name everyone gives to their mistakes". But most of the dramatic parts felt hollow and unreal, at least until the last act. Perhaps it was a problem with the production, which was an amateur one, instead of with the play itself. However, I suspect that Wilde as playwright is at his best in comedy and not in drama, much better in producing laughter than emotion. This would make The importance of being Earnest his best play, as seems to be the general opinion.

On the cathegory of "weirdest searches leading people to this blog" we have a new contender, though I don't like it as much as the classic chess entropy search. Someone came here hours ago from a Google search for:

duke + rape + einstein + blogspot

In case you haven't hear about the shocking Duke rape case, you can read all about it here (also lots of discussion here). But what has poor old Al to do with it???

Thursday, April 06, 2006

From my Mailbox

You see, I don't look for nerdy mathematical humour, it comes to me. (That is the difference between me and Gauss; cf. the eleventh of the following lines.)

Gauss didn't discover the normal distribution, nature conformed to his will.

Gauss can construct transcendental numbers only using a compass.

Parallel lines meet where Gauss tells them to.

Some problems are NP because Gauss doesn't like computers.

Gauss never runs out of room in the margin.

Gauss can write irrationals as the ratio of 2 integers.

Gauss never needs the axiom of choice.

Gauss can square the circle and then transform it into the hyper-sphere.

The location and momentum of a particle are what Gauss say they are.

An elegant proof is one line long. Gauss' elegant proofs are one word long.

Gauss doesn't look for roots of equations, they come to him.

There are no theorems, just a list of propositions Gauss allows to be true.

When Gauss integrates he doesn't need to add a constant.

Hilbert put forward 23 unsolved problems because he hadn't properly read Gauss' notebooks.

Gauss knows the topological difference between a doughnut and a coffee cup.

Gauss can divide by zero.

Gauss would never ever have a badbox error.

Primes that aren't Gaussian primes get teased.

If Gauss had to walk 100 metres, and half the remaining distance, then half the remaining distance again, and so on, he'd get there.

Erdos believed God had a book of all perfect mathematical proofs. God believes Gauss has such a book.

UPDATE: Only after recieving a follow-up email I realized that this list is inspired on the famous list of Chuck Norris Facts.

Report on BritGrav 6

Two days of conference. 29 talks. 2 lunches, 1 drinks reception, and 4 coffee breaks. (Actually, the afternoon coffee breaks are called "tea breaks". These British...) A brief summary of the highlights:


Day dedicated to classical General Relativity. Many talks on neutron stars, mostly about modelling which gravitational wave signatures do different processes in neutron stars leave. The talk that won the "Best student talk" prize was in this section, being by Brynmor Haskell of Southampton on the possibility of detecting "mountains" (large assymetries) in neutron stars. By the way I learnt that LIGO has reached its designed sensitivity already. Also today were some talks on conformal analysis techniques, numerical relativity (Carsten Gundlach from Southampton explained how the problem of modelling numerically black hole merging has been solved recently) and one on the Einstein-Cartan theory (gravity with torsion) as a possible explanation for inflation.

On the evening there was a drinks reception with free drinks and food :-), over the course of which I explained to Kirill Krasnov's girlfriend what blogging was about.


Day dedicated to black holes, quantum field theory in curved spacetime, and quantum gravity. More things of interest for me today, so the report is longer and more complete. All our research group gave talks.

Sam Dolan from Cambridge talked on wave scattering by a Schwarzschild black hole, considering scalar and fermion fields and results for wavelength comparable or much larger than the black hole radius. Gabor Kunstater, who is visiting our group from Winnipeg, talked about highly damped quasinormal modes of black holes, the famous "log 3" factor which may or may not signal a connection with quantum gravity, and the differences of the Reissner-Nordstrom case with the Schwarzschild one. (In RN the asymptotic behaviour for high frequency replaces the log 3 by log 5, but there is an intermediate regime where perturbations see only one horizon and there the behaviour has a log 3). Elisabeth Winstanley gave a talk with a title that at first glance could pass by a shampoo advertisement: "Abundant, stable EYM hair for black holes in AdS", in which she showed that there is no upper bound for how much "hair" an Einstein - Yang-Mills black hole in AdS can have.

Lutz Osternbrink from York derived averaged energy inequalities for the nonminimally coupled scalar field, which is atyipical in that it violates the pointwise energy conditions even at the classical level. These averaged energy conditions resemble those that apply for quantum fields in general as discussed in Chis Fewster's seminar.

Edward Anderson from Cambridge gave a talk on "The problem of time", the first transparency added below the title: " about a conceptual problem in reconciliating General Relativity and Quantum Mechanics, and not about why this talk is handwritten and monochromatic". He started by saying "let's take General Relativity seriously" and put on a transparency full of complicated-looking handwritten equations all in red, provoking widespread laughter. He discussed four possible ways of understanding the "problem of time" that the Hamiltonian of GR vanishes so in the corresponding "Schroedinger equation" there is no time evolution: 1) find a way to rewrite the equation so a "hidden time" appears; 2) the entire universe is indeed timeless, but in a semiclassical approximation an emergent time appears with respect to a background; 3) reality is truly timeless, and we must rethink the basis of dynamics to make it a theory of "being" and not of "becoming"; 4) GR is not the correct classical theory to quantize.

Now for the talks of us locals, starting with the research students. George Kottanattu talked on an axisymmetric SU(2) geon black hole solution he is constructing, with the intention of studying its thermodynamics. It is a generalization of the solution found in this paper; the study of Hawking radiation for geons was kicked off several years ago by this paper. Richard Johnson talked on mappings between spaces of functions arising from the Lorentz group, in particular the mapping of Conformal Field Theory correlation functions to Twistor space. Ileana Naish-Guzman talked about problems in the regularization of the Ponzano-Regge model for 3+0 quantum gravity, showing that the conventional regularization is ill-defined for many observables. And I talked about the particle detector model I have described here. My talk went quite well, by the way, thanks for asking. Chris Fewster was nice enough to tell me afterwards that on occasions during the talk he had thought of questions to ask, finding only that my next transparency always answered them.

Our supervisors: Jorma Louko talked about group averaging techniques for quantizing gauge systems and a particular example he has worked on with a previous research student here, Alberto Morgado. John Barrett and Kirill Krasnov both talked on 3D quantum gravity as Ilenana did; John gave a more technical talk describing the Turaev-Viro model (which unlike the Ponzano-Regge includes a cosmological constant, which is key for eluding regularization problems) and Kirill gave a more conceptual presentation on how 3D quantum gravity arises naturally from starting with Feynmann diagrams for particles and "dressing" them with extra geometrical structure, basically via making the momenta group-valued.

On the whole, a nice experience, although it is more fun when the conference is elsewhere and we get to travel. Next time that will happen for me is in July, going to the Marcel Grossmann Meeting in Berlin. Looking forward to it...

Sunday, April 02, 2006

Not quite a book review of A Devil's Chaplain, by Richard Dawkins

I started to write a book review of this book for posting it, but when I picked it up to refresh some details I was startled to see that I haven't really finished it! It is a collection of 32 essays and articles, and I have been reading them in disorder, so it's not so weird that I could think I had read them all and realize now I am still missing a few. Or well, perhaps it is. Anyway, that's what happened, but I will still write a post on a few isolated facts I learnt from the book that I found interesting or even thrilling:

- There are in Britain two well-differentiated species of gulls, with different colours and no interbreeding, but such that if you take one of them and track it round the world through North America, Alaska and Siberia, at each point round the way it is only one species, but it changes its colour gradually and when you are back in Britain it is the other species! The possibility of these "ring species" should not be a surprise for those who have absorbed the anti-essentialistic message of Darwin, but I had never thought of the possibility and was thrilled by reading about it.

- Darwin came tantalizingly close to completing his theory with the discoveries in genetics usually attributed to Mendel. He wrote to Wallace: "I crossed the Painted Lady and Purple sweet peas, which are very differently coloured varieties, and got, even out of the same pod, both varieties perfect but none intermediate". He is knocking at the doors of genes as discrete heredity units here.

- A quote Dawkins makes from a zoology book that creates an eerie image: "If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable ... we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes ... Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficent knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasits."

- Dawkins was an excellent personal friend of Douglas Adams, as well as a huge fan of his books.

- Though he created the concept, Dawkins is not quite as enthusiastic on "memes" as some of his succesors, in particular Dennett, have been. He is delighted that they have taken up his suggestion, but does not commit himself to endorse any of the particular uses "meme theorists" have made of it. He put forward the idea of memes just as a cultural analogue of genes on which a kind of Darwinian selction also acts, but wasn't intending them to play a founding role in theories of human mind or culture.

- Claude Shannon, father of information theory, had a strange sense of humour that led him to construct an "Ultimate Machine" that Arthur C. Clarke described in the following way: "Nothing could be simpler. It is merely a small wooden casket, the size and shape of a cigar box, with a single switch on one face. When you throw the switch, there is an angry, purposeful buzzing. The lid slowly rises, and from beneath it emerges a hand. The hand reaches down, turns the switch off and retreats into the box. With the finality of a closing coffin, the lid snaps shut, the buzzing ceases and peace reigns once more. The psychological effect, if you do not know what to expect, is devastating. There is something unspeakably sinister about a machine that does nothing -- absolutely nothing -- except switch itself off."

- When Stephen Jay Gould died, he had pending for revision a letter to the New York Review of Books that Dawkins had written for them to sign jointly, denouncing creationism and explaining why scientists should not debate with creationists in an academic context like a university (it gives them the respectability they are searching for and gives the public the impression that there is a real "scientific controversy" going on). Despite their known disagreement on many matters concerning evolution, Gould and Dawkins were firmly on agreement on this matter.

- And finally, the most exciting thing I read in the book. Dawkins makes the deduction from Moore's Law that the increase in DNA sequencing power grows exponentially (because it is driven mainly by computer processing capacity). Extrapolating this, he concludes that by the year 2050 we should be able to seqence a complete human genome for a trivial cost of £100. The same would be true of course for any animal species. By comparing the full genomes of humans and chimpanzees, we should be able to reconstruct the genome of the antecessor we share with them, that lived 5 to 8 million years ago. Comparing in turn this genome with ours, we may be able to recreate the genome of an intermediate species between us and the common ancestor -perhaps an Australopithecus. And if we have its genome, we may be able to bring the creature itself back to life...
The same game can be played with birds. Birds descend from dinosaurs that descend from ancient reptiles from which also modern reptiles are descended. Comparing the genome of birds and of modern reptiles might give us the possibility of reconstructing their last common ancestor, and afterwards an intermediate stage between it and a modern bird... in other words, a DINOSAUR!!
So even if the exact plot of Jurassic Park is impossible because no DNA is preserved in amber fossils and there is no original dinosaur DNA left in the world now, by intelligent examination of the DNA of the modern grandsons and second cousins of dinosaurs we may be able to reconstruct it and bring them back to life anyway. May that happen in our lifetime, amen!

My work (2): the technical details

This second post on my work is addressed primarly to readers with a background in physics. Read it at your own risk…

The transition rate at proper time t of a particle detector moving along the trajectory x(t) can be calculated by integrating over the detector’s trajectory the correlation function or Wightman two-point function of the field W(x(t), x(t-s)), times an oscillating function exp^(-i E s), where E is the energy gap of the transition. (t is proper time "tau", not coordinate time; it's just that Greek letters are not displayed). This integral done naively gives an infinite answer, as so many do in quantum field theory; the coincidence limit of the two-point function needs to be regularized to get a finite answer. The traditional way of doing this is adding a small imaginary part to time and the taking it to zero at the end of the calculation. However this procedure for regularization has been shown to give wrong answers in this paper by S. Schlicht. A different regularization procedure is introduced there, that uses a rigid spatially extended detector and "smeares" the field over it, taking the limit of a point-like detector at the end. This procedure, unlike the traditional one, preserves Lorentz covariance at each stage.

In Schlicht's paper a specific Lorentzian profile function is used to model the spatially extended detector. In my work I have adressed the question of whether the results obtained by this kind of regularization procedure are at the end independent of the profile function used or not. I have found that, under not very restrictive assumptions, they are indeed independent and there is a single expression for calculating the transition rate of a particle detector regularized with any profile function, and moving in any trajectory. (Perhaps I should say "we have found" because my supervisor Jorma Louko has played a very helpful role in the proof of this result). Our formula applies in particular to the uniformly accelerated case, in which it recovers the thermal result found by Unruh. It also applies to many "nonstationary" trajectories which can have arbitrarily varying acceleration, leaving out only a few trajectories that are
"too pathological" in a special sense that we define. In summary, we now have a crisp, simple expression for calculating how many particles from a quantum field in its vacuum state will be detected by an observer moving in an almost arbitrary way (in flat space; one of our main future goals is to extend this to curved spaces in the future).

And this is, more or less, what I shall say to the audience in the BritGrav 6 meeting this Wednesday, and what you shall be able to read in full detail when we have completed our paper on this subject, which hopefully shouldn’t take more than a few weeks from now.

Saturday, April 01, 2006

My work (1): Particle detectors and the Unruh effect

I had promised that I would post something on my work, and this is it. I decided to start with a general explanation of my area of research for nonphysicist (but patient and curious) readers, followed by a more precise explanation of my own work for the physicists among you.

The area in which I work is particle detectors in quantum field theory. What is this about? The basic entities that make up Nature (in our best current theories, setting aside General Relativity) are quantum fields. These fields, unlike classical fields, have a "complementary" (in the famously obscure words of Niels Bohr) particle description; the electromagnetic field, for example, can be described as well as a bunch of photons, which "carry the field" in discrete lumps. How are the two descriptions related? There are many ways of describing the relation, ranging from the very philosophical to the extremely mathematical and technical, some of them better for some situations and some for others. The "particle detector" approach is a simple, clear-cut, no-nonsense way of describing it: according to it, fields are the fundamental entities, and particles are defined in an operational way by the dictum "a particle is what a particle detector detects".

We start with the equation for a quantum field, which is actually the same as the equation for the corresponding classical field; for example, the Maxwell equations for the electromagnetic field. We add to the equation a small term representing a weak interaction between the field and a simple, well understood quantum system that has discrete energy levels: for example an hydrogen atom. This atom will be our "detector". We set the initial condition as the atom being in a particular energy level E0 and the field in some state [A> at some time t0. (For physicists: I apologize for this horrible way of representing a ket, and promise to try to get some math displaying package). Quantum mechanics allows us to calculate the probability that the atom would have, due to the interaction with the field, changed its energy level to E1 at some time t > t0. This change is interpreted as the atom having absorbed or emitted a "field quantum" or particle (e.g. a photon, if the field is the electromagnetic one). If E1 > E0 the atom has absorbed a particle of energy E1 - E0; if E1 < E0 it has emitted one of energy E0 - E1.

Suppose we have a very large number of identical atoms interacting with the field in this way (the technical word is "ensemble"). Then the probability of transition we have calculated is the fraction of atoms that have made the transition at time t. The time derivative of this probability is proportional to the number of atoms that are getting excited at t. (Suppose for simplicity that E0 is the lowest energy level so there is no de-excitation). We use this quantity to define the number of quanta (particles) present in the field at time t. Skipping over some proportionality constants and technicalities, the central idea is to define the answer to the question "how many particles does the field have at time t if it is in state [A>?" as being the same as the answer to the question "how many transitions per unit time are being registered in the particle detector (the ensemble of atoms) at time t when the atoms interact with with the field at state [A>?" This is a question quantum mechanics allow us to calculate an answer to.

This approach, though perhaps insufficiently fundamental and therefore insatisfactory from a philosophical point of view (after all, the atom with its discrete energy levels is taken by granted here) is very convinient in practice, gives sensible answers to many questions, and in particular can be used to shed light on an important and fascinating aspect of quantum field theory: the Unruh effect.

To explain the Unruh effect, I have to give some explanations on what are the states [A> a field can have. The lowest energy state of a quantum field is called its "vacuum" and represented by [0>; as you might have guessed, in the particle description this corresponds to "zero particles", and in the particle detector approach one can find that an atom interacting with a field in this state does not get excited (although more on this later!!) . Then there are states called [n>k, with n an integer, which are interpreted as "n particles with momentum k", and combinations of them like [n>k [m>q ("n particles with momentum k and m with momentum q"). But these states represent at the same time just certain wavelike vibrations of the field; the interpretation as particles comes (in the approach I am describing) via the interaction with particle detectors and the effect these vibrations produce on them. There are also approaches to quantum field theory in which particles are ontologically fundamental and fields are mathematical devices; whether the choice between both approaches is a matter of pragmatical convinience or has physical content is a philosophical question I shall not discuss in this post.

The relations described above between states of the field and particle content as measured by particle detectors, however, hold only when the detector is at rest or moving with uniform velocity (states physically indistinguishable according to the Special Theory of Relativity). If the detector is not moving uniformly, then a strange thing starts to happen: the detector starts to click even if the field is in the vacuum state! The detection of particles by an accelerating detector moving through a space that to an observer at rest appears as a perfect vacuum is one of the most surprising facts predicted by quantum field theory; it implies that contrary to all physical intuition, the notion of particles is relative to the observer. But what happens in the particular case of the detector moving with exactly constant acceleration is even more surprising. Bill Unruh proved in 1976 that in this case the particles detected will have a very peculiar pattern: the number of particles detected as a function of their energy is exactly that of a gas of normal, "real" particles at a certain temperature T equal to the acceleration of the detector divided by 2 Pi (in natural units). This is called the Unruh effect, and can be summarised as follows: the vacuum state of a quantum field appears to a uniformly accelerating observer as a thermal state with temperature proportional to the acceleration. For more info, see the Wikipedia entry.

I see that this post is already much too long, and I have not even started to describe my own work! (all the things I have explained are known since the mid 1970s). So I better stop here and leave the rest for one or two following posts. I just add here, to keep your interest alive, that the Unruh effect is intimately related to the famous discovery made by Stephen Hawking that black holes evaporate via a quantum radiation of particles. I will elucidate this on the following post on this topic. Meanwhile, I'll be more than happy to answer questions on the points covered on this post.