Category Archives: Darwin autobiography
This from Matt Young on pandasthumb:
Does gold have a purpose? asks an unnamed author in Evolution News & Science Today. The author goes on to observe that there is more gold on earth than astrophysicists can account for and also that gold has risen to the surface of the earth faster than might be expected. They go on to note the “availability of many essential elements at the surface of the earth …” and also discuss the use of gold in medicine. They are somewhat breathless at the discovery that the body can metabolize gold:
Gold nanoparticles, which are supposed to be stable in biological environments, can be degraded inside cells, [boldface in original]
even though, as they note, gold salts have been used for decades in the treatment of rheumatoid arthritis.
At any rate, the article stresses the “mystery of biological gold” and claims several hints why gold may have a purpose: its abundance and seemingly unlikely transport to the surface of the earth, the ability of cells to “metabolize” [sic] gold, the fact that gold persists in the body, and the usefulness of gold for therapeutics. The conclusion of the article is Read the rest of this entry
Mike Pence is a highly intelligent and extremely able trial lawyer, and a committed creationist. As I write, he is one heartbeat (or should we now say one breath?) away from being President of the United States, and in the event that Donald Trump manages to retain power in November, will be his heir apparent. Here is what I wrote about his stated views on creationism and evolution not long after he was sworn in as Vice-President. I hope that four weeks from today all of this will be of historical interest only, and am reposting this in order to help make that happen.
Above: Donald Trump risen from his hospital bed to reveal himself to his followers (Getty Images via Business Insider)
The now Vice-President of the United States stands accused of having said that evolution is “just a theory”; see here and here. No he did not say that. What he did say (full text below, with notes) was far, far worse. Much more detailed, much more closely argued, and much more dangerous. Read the rest of this entry
The now Vice-President of the United States stands accused of having said that evolution is “just a theory”; see here and here. No he did not say that. What he did say (full text below, with notes) was far, far worse. Much more detailed and much more dangerous.
L: Pence being sworn in as a member of the House Education and Workforce Committee (CNN)
After reminding us that he was trained in law and history, he mangles the historical facts and legal significance of a key court case (the Scopes trial).
By quotemining a secondary source,* which he treats as if primary, he twists the then-recent discovery of Sahelanthropus into an argument against the underlying science. It is changeable, he argues, therefore it is uncertain.
He justifies this manoeuvre by harping on the ambiguous word “theory”, and making a falsely rigid distinction between theory and fact.
Below, R: Sahelanthropus tchadensis, photo of cast by Didier Discouens, via Wikipedia
And worst of all, he asks his colleagues to “demand [emphasis added] that educators around America teach evolution not as fact, but as theory”. The proponent, when it suits him, of small Government wants Washington to tell teachers how to teach.
Pence has been accused of stupidity because of the factual and logical errors contained in his speech. On the contrary, Read the rest of this entry
There is now a second edition of Evolution: Making Sense of Life, by Carl Zimmer and Douglas Emlen, one of the very few textbooks I have come across that can be read for pleasure. Much as I deplore the US textbook publishers’ practice of issuing a new edition every very few years, this means that the first edition, which came out in 2013, is going to be available very cheaply for all of us who aren’t using it for of course credit and can tolerate the occasional underlining. Carl Zimmer (whose formal university education was in English, at Yale) is one of our most engaging current writers on evolution, and if you have not yet subscribed to his blog, The Loom, I urge you to do so. Douglas Emlen’s lab website clearly shows his passion for sharing the excitement of evolution science, and I have already reviewed his award-winning book Animal Weapons.
For much younger readers, the PDF of Jonathan Tweet’s Grandmother Fish, which I have also reviewed, is available as a free download, which qualifies it for a mention here. The physical copy, beautifully produced and printed, is now available in the US from Amazon, and I have advised Jonathan to look for a UK distributor. Answers in Genesis concedes that “the author and illustrator do a good job of simplifying evolution through words and pictures and using terminology that is kid-friendly,” so that “it is exactly those points that make the book so deceptive.” As most readers will realise, “deceptive”, as used by Answers in Genesis, is a technical term meaning “a good argument against Young Earth creationism”. I congratulate Jonathan on having earned this accolade.
At one time, I got interested in the seemingly simple question (to which I might well return one day) of whether zebras are horses that have acquired stripes, or horses are zebras that have lost them. Stephen J Gould, it turned out, had written a perceptive essay on this very topic in Hen’s Teeth and Horse’s Toes. When I went looking for this volume, I found out to my surprise that I could get hold of it, and many others in Gould’s magnificent series of essays, for pennies plus postage. (Here, one good search strategy is to start with Amazon, look for the “From” options, and then, where possible, contact the sellers directly. That way, I help the independents stay independent. For UK readers, I would also recommend searching Abe Books, although I was saddened to learn that they too are part of Amazon; I would be happy to learn of other equivalents).
Finally, most obviously, and still greatly underused even by professionals, the huge reservoir of literature available for free download in a wide variety of formats. This resource could be, and should be, even more valuable, but is limited by outrageous copyright restrictions; for no reason I can tell other than the special interest of Disney Corporation, the copyright on a work now only lapses 70 years after its creator’s death. So JBS Haldane’s seminal 1929 article The origin of life will not be out of copyright until 2034 (though if you can find it online, here for instance, you can get away with downloading a copy for individual study). And for Ernst Mayr’s 1923 paper on birds in Saxony, instrumental to his crucial redefinition of the species concept, you will have to wait until 2075, However, we have all the published works and much of the voluminous correspondence of Charles Darwin, to say nothing of TH Huxley, Charles Lyell (for all his writings, and for other seminal works on geology, many of them also available for free, see the Geological Society’s Lyell Collection), James Hutton, and even William Jennings Bryan. Legal proceedings are also in the public domain, regardless of time. So what shall we say of scholars and commentators earnestly debating Darwin’s own views on religion, in evident ignorance of what he himself tells us on the subject, in his freely available and beautifully written Autobiography?
Look, see , enjoy.
h/t reader Gordon Drumond, for disillusioning me about Abe Books
Summary: a doctrine that doesn’t deliver, the usual rhetorical tricks, begging the question, ignoring the evidence, distorting the science, and leaving all the work still to do.
I promised friends I would review this, so here it is. Fortunately, a paragraph by paragraph review has already been carried out by my BCSE colleague, Dr Robert Saunders, Reader in Molecular Genetics at the Open University, so I can be brief.
A doctrine that doesn’t deliver
This pamphlet is indeed a worthy introduction to what now goes by the name of Intelligent Design. Quote mining, baseless claims, ignoring of established facts, repetition of long exploded arguments, and, at the heart of it all, a purported explanation of phenomena that proves on examination to explain nothing. All as a thinly disguised excuse to discard what we actually know about deep evolution and, in the ID movement on this side of the Atlantic at least, about deep time.
Now to detail. First, the virtues of this pamphlet. It is short; the text runs to less than 16 pages. It clearly and undeniably exemplifies the logic, and rhetorical devices, of the contemporary Intelligent Design movement. despite a £2 pricetag, it cost me nothing, having been given away at Dr Noble’s recent talk at Al’ Furqan Masjid Community Hall in Glasgow, organised through Scotland’s Interfaith Council (a charity that receives public funds). And it contains three arguments with which, as Dr Noble might be surprised to learn, I agree. I agree with his claim that we do not know the origin of life. I also agree that that science should not restrict itself a priori to natural causes. In my only professional level publication on the philosophy of science, I argue that, on the contrary, our preference for natural causes is based on experience. And I also agree with Dr Noble that the multiverse hypothesis is highly speculative, that we lack the means to test it, and that fine tuning continues to present an interesting challenge.
Next, everything else. Note that what follows applies to the 2013 print edition. Online and earlier versions may differ; I have not checked.
The usual rhetorical tricks
Problems start in the first paragraph. About the Author describes Dr Noble as “a professional adviser to secondary school teachers.” This is disingenuous. He is the Director of the Centre for Intelligent Design, not a disinterested author. But that’s a small matter.
We rapidly move on to the now traditional list of Great Scientists who believed in an Almighty Creator. And so they did. So, as I have explained here and here respectively, did James Hutton, originator of our modern concept of deep time, and, at the time when he wrote On the Origin of Species, Charles Darwin (Autobiography p. 93). So do many distinguished contemporary evolutionary biologists, ranging from the Evangelical Francis Collins to the Catholic Ken Miller, whom I will be mentioning again in this review. I wonder why the ID crowd never talk about any of these.
Then the next traditional feature, the Mined Quote. So we have Einstein, although Noble is surely aware that Einstein regarded belief in Noble’s kind of God as infantile. We even have what Michael Denton wrote in 1985, ignoring the fact that his views had changed dramatically by 1998. And of course the claim, which has been around since the 1920s, that more and more scientists are abandoning naturalistic evolution in favour of supernatural processes.
Next, the key assertions, on which the entire theory (if that is not too kind a term) depends. The first assertion is that complexity is evidence of design; the second and third, discussed below, are that information can only arise through the operation of an intelligence, and that some biological functions are “irreducibly complex” and thus could not have arisen through evolution. The first assertion runs something like this: we accept that complex artefacts are designed, and hence can infer that biological complexity likewise involves design. Expressed as a syllogism
Safety razors (Noble’s example) are complex, well adapted to function, and designed.
Living things are complex and well adapted to function.
Therefore living things are designed.
This is essentially Paley’s argument, which Darwin himself found impressive as an undergraduate (Autobiography, pp. 59, 87). However, the entire point of natural selection is that it explains how living things can become well adapted to function, without the intervention of a designer, and the entire history of life is a story of how this has happened. ID’s immediate appeal to a principle of design rules out at a stroke everything that has been gained by two centuries of investigation.
Begging the question
To bolster his claim, Noble repeatedly asserts that random change cannot generate what William Dembski has called “complex specified information”, and even goes so far as to say (p. 9) that “We know that information can only arise from prior intelligence”. He admits that evolution can function up to a point, which he calls “microevolution”, but (p. 28) makes a bizarre assertion that “Microevolution necessarily involves an overall reduction in the amount of genetic information.” This is false. Some information may be lost when less fit variants within a population tend to die out, but we know that information content is being continuously replenished by mutation, at the same time that it is being winnowed by selection. All this was worked out almost a century ago, with the development of population genetics, while Dembski’s specific probability arguments crumble in the face of a recent theoretical analysis of the time required for complex information to evolve under natural selection.
Ignoring the evidence
Next, the appeal to specified, or even irreducible, complexity, and Noble asks us to consider the eye, the ear, and that old standby the bacterial flagellum. Here, Noble actually states that ID would fail if “there is a clear step-by-step evolutionary pathway with all the intermediary stages to a bacterial flagellum or similar irreducibly complex structure which can be generated by mutations alone.” If by “mutations alone” he means mutations without selection, he is asking for something that reality does not offer. If he means an account of how the bacterial flagellum could have emerged from earlier structures, this was famously presented at the Kitzmiller v. Dover Area School Board trial, where Ken Miller testified on this very point (here, pp. 12 on; for more on Miller on the flagellum see here). If Noble then complains that that account does not include a historically reliable account of all the intermediate stages, he has missed the entire point of his own argument. Irreducible complexity, if it means anything, means that the structure could not possibly have emerged through naturalistic evolution, and Miller’s testimony readily explains how it could.
Distorting the science
There are other minor absurdities. Noble suggests that the fact that water is a liquid depends on tiny variations over and above the general rules of chemical bonding. As a chemist, he should know better, since the “hydrogen bonding” that holds H2O in the liquid state is a consequence of the same set of rules that makes the closely related substance H2S a gas. He also claims that complex life requires the moon to be exactly the right size and right distance, otherwise Earth’s axis would become unstable. I am mystified, unless he is running together two separate claims, one (plausible) regarding the stabilising effect of a satellite, and the other (ridiculous, but taken seriously within the ID community) that regards us as privileged because we are on a planet where we can observe both total and annular eclipses. And like the rest of the ID community, he misinterprets the ENCODE project, which showed that 80% of the human genome is biochemically active. We are invited to infer that DNA is perfectly designed and free of junk. But consider the “onion test“; in brief, an onion contains five times as much DNA in each cell as a human; does anyone imagine that it contains five times as much complexity?
And leaving all the work still to do
Finally, my most severe criticism of ID, which I have already stated here very briefly. It doesn’t answer the question. For a safety razor to come into existence, we need, not only design, but fabrication. And when we come across any natural feature that requires explanation, invoking ID merely leaves us two (or, if the use of ID involves rejecting naturalistic evolution, three) problems for the price of one. We have the problem of accounting for all the evidence for evolution by trial and error tinkering, combined with natural selection and genetic drift, ranging from biogeography to developmental embryology to anatomical (and now molecular) phylogeny, and much much more. We have the problem (although I suspect that for Dr Noble this is not a problem at all) of specifying the nature, provenance, and motivation of the designer (or Designer). And finally, worst of all, we still don’t know how it happened. Paley’s watch implied, not just a watch designer, but a watch assembler, a parts manufacturer, a toolmaker, a metallurgist… Unless the Designer just wills complete structures into being, in which case there’s no point even trying to do the science.
In short, this pamphlet delivers what it promises to, but the doctrine that it is promoting does not. Dr Noble repeatedly and sincerely asks us to open our minds; he is unaware that ID is an invitation to close them.
The spectacles are not mine, but those of my good friend Michael Roberts. For what it’s worth I think he underestimates Darwin’s attachment to religion. In his Autobiography (not intended for publication) Darwin says that when he was writing On the Origin of Species, he considered it impossible to conceive of this woderful Universe as the product of mere chance, writing “I feel compelled to look to a First Cause having an intelligent mind to some degree analogous to that of man, and I deserve to be called a Theist.” And he attributed his later agnosticism to doubt as to whether a mind evolved through natural selection was capable of grasping such lofty matters. (A doubt shamefully misrepresented by Plantinga, as I have shown elsewhere, for his own self-serving reasons)
CHARLES DARWIN (1809-1882)
February 12th 2009 saw the bicentenary of Darwin’s birth. Along with Isaac Newton he was one of the greatest British scientists, though his science is still controversial. To some he was a great scientist and to others the devil incarnate!
He was a quiet family man, whose life was marred by illness. He was born into an affluent home in Shrewsbury and went to Cambridge to study for the Anglican ministry. In 1831 he was invited to join the Beagle to sail round the world. That changed his life and the course of science. On that voyage he was more interested in geology and only later “moved” over to biology.
Darwin learned his science at both Edinburgh and Cambridge and some of his student notes survive. His family was scientific and as a teenager he had a well-equipped chemistry lab in an outhouse at the Mount
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[E-mailed and snail-mailed to Tron Church; no reply received as of 4 weeks later. If I ever get one, I’ll give it its own post and publicise] Dear Dr Philip; You are misleading your congregation on a matter of fact. I address you both publicly and privately, and promise to publicise your reply.
In a recent web post, entitled “The Inhumanity of Humanism,” you say [a reader points out that these words and the others I cite below are not the Rev’s own, but his father’s, embedded and quoted at length with approval] I am not human because I have not been saved by Jesus. You are entitled to that opinion. But you are not entitled to the manipulative misrepresentation of a distinguished evolutionary scientist, on which you base your completely unwarranted claim that the science of evolution is based on a decision to exclude God. You seem unaware of the long array of distinguished evolutionary scientists who have believed in God, including Charles Darwin at the time when he wrote On The Origin Of Species, but let that pass.
It [humanism] does not start with scientific evidence; it starts with an objection to God, and by a process of rationalisation transfers the antipathy towards God to so-called scientific arguments against his existence. This is what I meant earlier by saying that as an argument this is not very scientific, any more than another noted scientist, Professor D.M.S. Watson, is, when he says: “Evolution itself is accepted by zoologists not because it has been observed to occur, or….can be proved by logically coherent evidence to be true, but because the only alternative, special creation, is clearly incredible”. Well, well! So this is science. This is keeping God out with a vengeance! It scarcely commends “the scientific attitude” however, to thinking people, and it gives us leave to question whether the “assured results” of modern science are always as assured as they might be.
Here you have moved from an attack on Humanism to one on the science of evolution. In order to do so, you are putting into Watson’s mouth the claim that evolution is accepted without evidence merely because special creation is ruled out in advance as incredible. You then use his alleged position to launch a broad attack on those who claim to be embracing “the scientific attitude,” whatever you imagine that to be (in my experience, there are as many attitudes as there are scientists), and specifically to call into question the assured results of evolutionary science. I do not know why you do this, since I see nothing in evolutionary science that conflicts with your own Church’s statement of faith.
I will be charitable, and assume that you are unaware of the fact that you are echoing a well-known misrepresentation of Watson’s position. Indeed it is so well known that it has its own Wikipedia link. I have checked, as you evidently have not, the actual quotation, publicly accessible here (p. 95, halfway down), and find that it does indeed speak of “the Theory of Evolution itself, a theory universally accepted, not because it can be proved by logically coherent evidence to be true, but because the only alternative, special creation, is clearly incredible.” However, this is a partial recapitulation of the fuller statement on p. 88, which reads:
Evolution itself is accepted by zoologists not because it has been observed to occur or is supported by logically coherent arguments, but because it does fit all the facts of Taxonomy, of Palaeontology, and of Geographical Distribution, and because no alternative explanation is credible.
But whilst the fact of evolution is accepted by every biologist the mode in which it has occurred and the mechanism by which it has been brought about are still disputable.
Watson, remember, was writing in 1929, when the evidence available was far scantier, the interrelationship between genetics and evolution still being worked out, the nature of the genetic material unknown, and the very existence of the gene as a material entity the subject of controversy. What he is doing is stating the inadequacy, in 1929, of biologists’ understanding of the mode and mechanism of evolution. He refers correctly to evolution as a fact even then established by the evidence, and rejects alternatives because they give no credible explanation of the data. In the rest of his article, he goes on to ask good questions about the process by which evolution occurs, questions that have received good answers aplenty in the intervening 85 years (some of them ably expounded by Dennis Venema, himself an evangelical Christian, here). D. M. S. Watson most emphatically does not do what you accuse him of doing, namely ruling out creationism because he wishes to exclude God. I have no idea what his views were on the existence of God, nor do I see how they are relevant once his words are honestly examined in their actual context.
I hope you will disabuse your congregation of the error that you have, no doubt I unknowingly, helped propagate, and I undertake to publicise any reply you make as extensively as I am publicising this letter.
Prof Paul S. Braterman, MA, DPhil., DSc.
 The actual words are: “It is not possible to be human (or humanist, rightly understood) without being saved into humanity by the God Who gave Himself for us in Jesus Christ.” It has occurred to me, since sending this piece to the Reverend, that he may be a Universalist who believes I have been saved despite my lack of belief, but I do not think this likely.
Lord Kelvin (Smithsoinian Instituion Libraries collection)
Kelvin calculated that the Earth was probably around 24 million years old, from how fast it is cooling. Rutherford believed that Kelvin’s calculation was wrong because of the heat generated by radioactivity. Kelvin was wrong, but so was Rutherford. The Earth is indeed many times older than Kelvin had calculated, but for completely different reasons, and the heat generated by radioactive decay has nothing to do with it.
Disclosure: in my introduction to the Scientific American Classic, Determining the Age of the Earth, and elsewhere, I have like many other authors repeated Rutherford’s argument with approval, without paying attention to Rutherford’s own warning that qualitative is but poor quantitative, and without bothering to check whether the amount of heat generated by radioactivity is enough to do the job. He thought it was but we now know it isn’t. It was only when chatting online (about one of the few claims in the creationist literature that is even worth discussing) that I discovered the error of my ways.
On the face of it, things could not be plainer. Kelvin had calculated the age of the Earth from how fast heat was flowing through its surface layers. An initially red hot body would have started losing heat very quickly, but over geological time the process would have slowed, as a relatively cool outer crust formed. His latest and most confident answer, reached in 1897 after more than 50 years of study, was in the range of around 24 million years.
Yet on May 20, 1904, there was Rutherford, at the lectern of the Royal institution, talking about a piece of Cambrian rock, and announcing, on the basis of how much of its uranium had decayed to give lead and helium, that its age was some 500 million years. We even have Rutherford’s much quoted account of what happened next:
I came into the room which was half-dark and presently spotted Lord Kelvin in the audience, and realised that I was in for trouble at the last part of my speech dealing with the age of the Earth, where my views conflicted with his. To my relief, Kelvin fell fast asleep, but as I came to the important point, I saw the old bird sit up, open an eye and cock a baleful glance at me.
Then a sudden inspiration came, and I said Lord Kelvin had limited the age of the Earth, provided no new source [of heat] was discovered. That prophetic utterance referred to what we are now considering tonight, radium! Behold! The old boy beamed upon me.
This all seems clear enough. Rutherford is referring to Kelvin’s cooling argument. But this argument is invalid, because it assumes no new source of heat, and such a source exists, namely radioactivity.
The process that was overlooked in Kelvin’s calculations was also, indirectly, responsible for producing these folds.
Or so says the popular myth. The truth is more complex, and more interesting. For a start, Kelvin’s “prophetic utterance” did not refer to the Earth at all, but to a separate calculation of the age of the Sun. We know how brightly the Sun shines, and hence how rapidly it emits energy. If we knew how much energy it had to start with, and assumed that it wasn’t being added to, we could simply divide the initial amount by the rate of depletion, to estimate how long it would be able to shine. Kelvin performed such a calculation many times. As source of energy, he invoked the most intense source known to him, namely the gravitational energy released when the Sun collapsed from a diffuse cloud of gas to its present size. This led him to conclude in 1862 that the age of the Sun was in the range of 10 million to 100 million years (subsequently refined to around 20 million), and that “inhabitants of the earth can not continue to enjoy the light and heat essential to their life for many million years longer unless sources now unknown to us are prepared in the great storehouse of creation [emphasis added].” These are the prophetic words that Rutherford was referring to.
If Rutherford thought that the energy of radioactive decay was fuelling the Sun, he was greatly mistaken. The philosopher Auguste Comte had written in 1835 that we would never know the internal composition of the heavenly bodies. He was wrong. Pass electricity through a gas or vapour, and it will emit light at specific frequencies that depend on the elements present (one familiar example is the sodium yellow of street lights). There are dark lines in the solar spectrum, and by 1860 the German chemist Kirchoff had shown that their frequencies match these characteristic emission lines. So the chemical composition of the Sun’s outer layers was already well-known, and the fractional abundances of the heaviest elements, including almost all those that exhibit radioactivity, are quite negligible. And we now know, as Rutherford could not, that radioactive decay does not generate enough energy. Even if abundant supplies of the radioactive elements were concealed within the Sun’s interior, they would not suffice to fuel the Sun for Rutherford’s 500 million years, let alone the 4,500 million years, with as much still to come, required by current estimates. It was not until 1920 that the source of the Sun’s energy was correctly identified as the fusion of hydrogen to helium, and while this was soon generally accepted, quantitative confirmation by measurements on the neutrinos produced had to wait until 2001. Using Einstein’s famous mass/energy equation and the masses of the isotopes involved, it is easy for us to calculate that the fusion of hydrogen to helium is some thirty times more productive of energy than the decay of the same mass of uranium to helium and lead; but Rutherford in 1904 could not have known of the relationship between mass and energy, or the precise masses of the relevant isotopes, or even that such things as isotopes existed.
But what about the age of the Earth itself, and Kelvin’s cooling calculation? This is what I had for many years assumed that Rutherford was talking about, and it turns out that radioactive decay is no real help here either. Measurements on granite in the early years of the 20th century suggested that radioactivity could fully account for the amount of heat being radiated out to space, and that the Earth might even be heating up. But we now know that granite is not representative of the Earth as a whole. The total rate of heat production by radioactive decay is currently estimated at around half the amount that the Earth emits to space, so simplemindedly we might imagine that this extends Kelvin’s calculation by a factor of two. Maybe a bit more, since by their nature radioactive materials would have been more abundant in the remote past, but this will not make much difference over the few tens or even hundreds of millions of years then under discussion. And even this grossly exaggerates the potential significance of radioactive heating, since all we need to consider is the heat generated in the outermost layers, from which heat has had time to diffuse the surface.
So how could Kelvin’s cooling argument be refuted? The correct argument had been put forward a decade earlier, before radioactivity had even been discovered, by John Perry, one of Kelvin’s own former pupils, and Kelvin had partly accepted the principle of Perry’s reasoning.
To understand what is really happening, we need to consider the different ways in which heat can be transferred. You may remember from school that there are three processes available; radiation, conduction, and convection. Radiation is the process by which the Sun, or the filament of an incandescent light bulb, glows yellow hot; or at lower temperatures the embers of a fire or the coals of a barbecue glow red hot; or, at yet lower temperatures, the Earth loses energy to the coldness of outer space by glowing in the infrared. It is not really relevant to the transmission of energy through opaque material such as rock. Conduction is simply the diffusion of heat through material, as the faster moving atoms of the hotter region jostle against, and share their energy with, their cooler neighbours. The third, and most efficient, heat transfer mechanism is convection. This is the physical movement of hotter material, carrying its heat with it, as in the roiling that takes place in the water when you boil an egg on a stove, or the pattern that forms in the film of oil in the pan if you prefer your eggs fried. Hotter material expands, making it less dense, so it rises to the surface, bringing cold material closer to the heat source.
Convection in a pan over a heat source. Warm (red) material is less dense and rises, allowing cold (blue) material to sink. Image by Eyrian through http://en.wikipedia.org/wiki/File:ConvectionCells.svg
Radiation is only relevant when we are talking about the transfer of heat through empty space, or through some transparent medium. Diffusion is simply the statistical spreading out of the extra heat in the hotter material, and is an inefficient process over long distances. By far the most efficient heat transfer mechanism is convection, but this can only take place in a fluid, where hotter and colder material can physically change places.
Back to Kelvin’s cooling rate calculation. This depended, among other things, on assuming heat transfer by conduction, and the rate of conduction was determined by actual measurements on rocks. Now imagine what would happen to Kelvin’s calculation if the actual heat transfer process were more efficient than this. The effect is the opposite of what you would at first imagine. Commonsense suggests that more rapid heat transfer would imply more rapid cooling. Not so. If heat transfer is limited, only a relatively shallow layer near the surface will have had time to contribute. If heat transfer turns out to be more efficient, the cooled layer will be correspondingly thicker, heat will have been conveyed from greater depths, and the total amount of heat conducted through the surface and lost to space will be correspondingly greater. But we know the total rate at which heat is being transferred, from the conductivity experiments and the rate at which temperature increases when we go down a mine, and this acts as a constraint on the calculation. Fixed rate, but a greater total amount because of more efficient heat transfer, implies a longer time. The cooling calculation can therefore be brought into line with Rutherford’s results, and indeed with the even longer times that we now know to be involved, if heat at depth is sufficiently more mobile than Kelvin had imagined.
In 1894, Kelvin’s former pupil and protégé, John Perry, had suggested higher heat transfer as a way of reconciling Kelvin’s age estimates with the hundred million years or so then required by the geologists. Kelvin, rather grudgingly, agreed in principle, and undertook to examine whether the thermal conductivity of rocks did increase as required at high temperature.  Within a few months, Kelvin reported a colleague’s response to this question; they did not. Indeed, Kelvin took the opportunity to review the entire question in the most extreme possible light, triumphantly lowering his best estimate of the age of the Earth to around 24 million years, noting that this was in good record with his estimates for the age of the Sun, and claiming that the burden of proof was now back with the geologists. Perry, in reply, drew attention to the fact that Kelvin had totally ignored the possibility that the Earth’s interior was or had been fluid enough to support convection, but Kelvin seems to have passed over this suggestion in silence.
A pity. Convection in the mantle, as we now call the region between the solid crust and Earth’s metallic core, is a cornerstone concept of modern geology. The implications of this, together with an explanation of why Perry waited until 1894 to challenge Kelvin’s calculations (which went back, as we have seen, to 1862 and earlier), and how I belatedly stumbled upon this story as a result of chatting online about the creationist literature, will be the subject of further posts.
An earlier version of this post was published in 3 Quarks Daily
 Comte, Positive Philosophy, Bk II Ch 1
 Annalen der Physik 185, 148–150, 275-301 (1860).
 Some radioactive elements, such as the newly discovered radium that Rutherford was referring to, do generate heat quickly, but that is because of their rapid decay rate, which implies short half-lives and rules them out as candidates.
 Perry, Nature 51, 224-227 (1895); Kelvin’s acknowledgement is at p. 227, his dismissive rebuttal at p. 438, and Perry’s final attempt at persuasion at p. 582.
Darwin thought the parallel “Roads” of Glen Roy represented vanished marine shorelines, one above the other as the result of vertical movement. Agassizexplained them, rather, as successive shorelines of a glacial lake, now vanished because the retaining glacier has melted away. If so, and if global warming is real, we might expect to see vanishing lakes today, as the glaciers retreat. We can, and we do, as a recent blog post by my friend Peter Hess explains.
Glen Roy is a valley in the Western Scottish Highlands, just south of the Great Glen (home to Loch Ness), and draining through Glen Spean to Loch Linnhe, an inlet of the Atlantic. It is remarkable for the presence of the Roads, a series of parallel, almost horizontal, grooves in the hills on the sides of the glen. Clearly shorelines; but of what body of water? And why are there more than one of them?
From Darwin, C. R. 1839. Observations on the parallel roads of Glen Roy, and of other parts of Lochaber in Scotland, with an attempt to prove that they are of marine origin. Philosophical Transactions of the Royal Society 129: 39-81, through Darwin Online
Charles Darwin visited the area in 1838, two years after his return from his round the world voyage on the Beagle. During that voyage, he had examined the geology as well as the plants and animals of the places he visited, and among them was the coastal area of Chile. This is marked by raised beaches inland where once had been shoreline, and Darwin correctly described these as the effects of uplift, which we now know to be driven by plate tectonics. So it was natural thatDarwin should have applied a similar explanation to the Roads, suggesting that the Cairngorms, like the Andes, were a zone of uplift, and that the Roads were ancient beaches of the Atlantic, now some ten miles away. The alternative theory, that they represented shorelines of an ancient lake, ran up against a seemingly conclusive objection; such a lake could only have formed if there had been a barrier across the valley, but there was no trace of this.Only a year later, shortly after going public with his Ice Age theory, the naturalist Louis Agassiz visited the area. In the Highlands he found plenty of evidence to support his idea; scratches on bedrock caused by the passage of glaciers, erratics (boulders far from their parent rock formations), and moraines (piles of rock rubble that had been carried by glaciers, left in place when the glacier melted). He considered the Roads further evidence of this; yes, there had been a lake, and yes, the roads did represent the shorelines at different times, carved into the sides of the valley by fierce freeze-thaw cycles. As for the barriers holding the lake in place at different levels over the course of time, they were a series of long vanished glaciers.
We now know that Agassiz was basically correct, although we now speak of a series of glaciations rather than a single Ice Age, and although Darwin was right in this; that the area has in addition experienced uplift, as the weight of ice above it has melted away.
Later Darwin was to write of this as his greatest blunder, describing in his Autobiography how in Wales he had missed the evidence of glaciation all around him, and generously acknowledging Agassiz for having come up with the correct explanation.
Agassiz rejected Darwin’s concept of evolution when it was published twenty years later because he believed in the fixity of species, but this does not seem to have diminished Darwin’s respect for him. What is now nothing but a deliberately cultivated ignorance was then, with so much less evidence available, no more than an understandable conservatism.
The overflow channel through which the vanished Loch Roy must have drained can still be detected as an abrupt narrow valley in the surrounding hillsides. The draining of the vanished lake in South America sent a surge through its own channel, down Chile’s main river, and caused giant waves as far as the Pacific Ocean, 60 miles away.
Lake to sandy valley overnight (from Peter Hess posting on NCSE blog site)
The glaciers of Switzerland are receding. Those of the southern Andes are receding even faster. Since Agassiz and Darwin examine the roads of Glen Roy, the earth’s mean surface temperature has increased by roughly 1oC, with another 0.5oC in the pipeline even if emissions were to be stabilised at the same levels as in the year 2000.
Which, of course, they won’t be.