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Young Earth Creationists arguing in circles

Relative dating from sedimentology dates back some 200 years, as beautifully explained here by my friend, field geologist and Anglican priest, Michael Roberts, with illustrations from what he has seen himself, while we have now had absolute radiometric dates for over a century. Index fossils are used only to establish that rocks are the same age, and the way creationists manage to forget this fact is indeed miraculous.

This piece gains added interest because of its first-hand accounts, both of geological exploration, and of attempts to persuade creationists to accept the results.

Peddling and Scaling God and Darwin

This incredibly duplicitous meme appeared on my twitter feed today. Fri 13th Jan 2017icrevolution

Evolution is wrong as it is a circular argument from the age of fossils worked out from evolution

Yes, it is the old chestnut of Young Earthers that the age of rocks is based on a circular argument from evolution. It took me back to 1971 when I made the felicitous mistake of going to L’Abri to sit at the feet of the evangelical guru Francis Schaeffer. I arrived ther all bright-eyed and bushy tailed thinking of all the wondrous things I would learn in the next four weeks. I learnt much but not what I had expected.

On my first morning i was sent to Shaeffer’s son-in-law Udo Middlemann to discuss what I would study. I explained that I was going into the Anglican ministry and had just returned from 3 years working as an…

View original post 1,825 more words

Homage to Jack Chick, (April 13, 1924 – October 23, 2016); repost of How to lie about radiometric dating, evolution, and even nuclear physics

Now that he is dead, let us play Jack Chick the compliment of treating his ideas as seriously as we did when he was alive. I am sure he would not have wished otherwise.

And so, in his memory (he died on Sunday) I am reposting my analysis of one of his pieces that I found particularly interesting [update: Americans United for the Separation of Church and State have also reviewed his life and work, here]:

How to lie about radiometric dating, evolution, and even nuclear physics

Have you heard the one about the live snail with a carbon-14 age of 3000 years? Or the lava erupted in 1800 in Hawaii with a potassium-argon age in the millions? It’s all true, true I tell you. But does this signify a major problem with radiometric dating?

Spoiler: no.

I don’t know who first dug up these examples, but they were popularised by the creationist comic-book writer Jack Chick, in a publication called “Big Daddy”. The first page, available here, shows a well-primed creationist student arguing with a singularly ill-informed biology professor. The professor has been leading such a sheltered life that he’s never met these creationist arguments before. And he doesn’t understand anything about evolution or dating of rocks or embryology or indeed anything else. Surprise! the student wins! A skilled cartoonist, Jack Chick manages to squeeze the largest number of fallacies into the smallest number of words. There is a crib sheet at the end of this post, listing all the fallacies I spotted myself; I just reached double figures but there may be more.

Evoa

dating

gillarch

vestigial

Of course, it doesn’t help that the Professor doesn’t know anything about whale ancestors:

WhaleAncestors

Or that the student is allowed to make the most absurd statements unchallenged, on the basis of a video by Kent Hovind:

evoc

But there’s more! At the end of page 1, which is also the end of your free sample I’m afraid, the student converts the Professor by pointing out that no one has ever actually seen gluons:

Gluons

Gluons2

But fear not; an answer is at hand, in the very next frame:

Gluons3
So Jesus must be the force that holds the atomic nucleus together. Convinced by this reasoning, the Professor accepts Jesus, announces that as a result he can no longer teach evolution, and is sacked.

Jack Chick, by the way, has just published another comic book at the age of 92. In it, a bright young man from a good Christian (i.e. creationist) home is seduced by Satan into believing in evolution, and when we last see him is heading straight for damnation. In the words of one of Satan’s many horned helpers, “Joe trusted evolution, not God, and became a jobless party animal.” And a criminal and a drug addict, and covered himself with tattoos, and died and went to hell. Tragic, and so easily avoidable.

I never managed to get to Page 13 of Big Daddy, which is what we really need; link (if it works for you) here. It didn’t work for me, but you’ll find a description of the contents by someone called Honus at talkorigins, and I’ve seen some of the relevant cartoons reproduced elsewhere. So you can either take Honus’s and my word for it, or go online to Chick Publications and buy 25 copies (minimum purchase) of the tract, which I am not about to do.

The really remarkable thing about the tract is that it actually gives the primary literature references to the results that is discussing. And the briefest perusal of this primary literature will show why the papers that Chick refers to, far from undermining radiometric dating, actually reinforce it.

That snail was not 3000 years old, but that really was its apparent radiocarbon age, because it was exchanging calcium carbonate in its shell with mineral calcium carbonate. And that makes all the difference, so you need to take such features of the environment into account.

Many readers will be familiar with the principle of carbon-14 dating. Carbon-14 decays with a half-life of 5730 years. Nonetheless, the fraction of carbon-14 in the atmosphere stays roughly constant (or did before we started adding to it by nuclear weapons testing, and diluting it with carbon dioxide from fossil fuels). That is because the upper atmosphere is bombarded with cosmic rays, which cause nuclear reactions that convert nitrogen-14 (stable) to carbon-14. Mixing distributes this radiocarbon through the atmosphere, where it is taken up by plants and, in due course, animals. As long as you are alive, you are part of the circulating pool of carbon, but as soon as you die, the carbon-14 in your body starts decaying. Of course, cosmic ray intensity is not really constant over a long period, but we can calibrate carbon-14 dates by comparison with carbon in tree rings (dendrochronology). The tree ring correction is small for most purposes, but matters for things like precise dating of Egyptian dynasties.

The point, of course, is that the carbon in the lettuce being fed to the snails is part of the general pool, but the carbon in calcium carbonate minerals is radiochemically dead, having been out of circulation for a long time. What the paper really showed was that the snail exchanges carbonate in its shell with carbonate from dissolved minerals, giving a spurious depletion of radiocarbon in the snail. You will find the story in Science, 1963, p. 637 (paywall, sorry, but summary here).

What about these rocks in Hawaii? Here again the paper is behind a pay wall, but if you follow this link it will take you to the title and abstract, which is all you need. In fact, the title alone is all you need: “Radiogenic helium and argon in ultramafic inclusions from Hawaii”. Inclusions. And in case that’s not clear enough, the abstract tells you that the work is all about the dating of xenoliths. Xeno- foreign, as in xenophobia; lith rock, as in monolith. Look at the paper in more detail, if you can get access to it, and you will find that the excess argon is only found in bubbles of fluid within the rock, that bits of rock that aren’t bubbly don’t show any, and that there is circumstantial evidence that the argon comes from deep within the Earth’s mantle, not radioactive decay in the lava itself.

Anomalies happen all the time in geology. They are, in the original sense of the expression, exceptions that prove the rule; if there were no rule, we would not consider them exceptional. Uranium-lead and potassium-argon dates of rocks usually agree, but not if the rock has been so strongly heated that argon gas can escape. Whole rock dates can be misleading, as in the example of the Hawaiian volcano, if the rock has been contaminated from some source, in this case fluid from the mantle. So far from undermining the method, these anomalies add further information about the sample. In much the same way, radiocarbon dates will be anomalous if some of the carbon comes from inorganic sources, as in the case discussed above, and the anomaly might even be used to tell us something about the specimen’s history and diet.

Now here’s the bit that I really don’t understand. What is going on in Jack Chick’s mind, when he gives us this stuff? I assume that he is an honest person of goodwill, who is doing his best. He really believes that because I and most readers here accept the fact of evolution, we are going to be punished in hell for ever. Being a kindly man, he really doesn’t want that to happen, so he is doing his very best to convince us of the error of our ways.

So why does he do it by pointing us towards papers that say the very opposite of what he says they say? I can only speculate that this is the result of what psychologists call confirmation bias, which leads to interpreting new information, however perversely, in a way that supports what you already think. And when we come to creationism, the motivation for bias is extreme. Remember that we are talking about people who really believe (a) that if you don’t accept salvation through Jesus you are going to go to hell, and (b) that the doctrine of salvation through Jesus only makes sense if the biblical Fall is a historical fact. The papers I’ve mentioned above show that under certain rather special circumstances, radiometric dating will give you the wrong answer unless you take those circumstances into account. Young Earth creationists, knowing that their entire worldview depends on refuting radiometric dating, pounce on these examples as evidence that the method is unreliable. Which of course it is, if you don’t do it right. So what?

All of which gives me uncomfortable pause for two reasons. If creationists are so blinded by confirmation bias, what hope is there of reasoning with them? And if I see my intellectual opponents displaying confirmation bias, completely oblivious to what they are doing, what makes me think that I am any different?

h/t Sensuous Curmudgeon for tip-off about Jack Chick’s latest. Whale ancestors illustrated (Ambulocetus and Pakicetus) copyright JGM Thewissen; may be reproduced for non-commercial educational purposes.

IncredibleCrib sheet: Definition as obfuscation. Misdefinition of science to exclude all indirect inference (although even Young Earth creationists accept the fact of an Ice Age on geological evidence). Macroevolution, if the word means anything, means major change, and this takes more time than we have been watching. So of course we’ve never seen it. Similar fossils do indeed imply similar ages, but the order of these ages has been known for nearly 200 years on the basis of stratigraphy, and absolute ages established for over 100 years now by radiometric dating. Polystrate fossils were explained in 1868; the explanation is much the same today. New Scientist really did point out in 1997 that it is silly to carry on using Haeckel’s highly questionable drawings, as some still do, when we now have a much more detailed information. But, as explained in Alice Roberts’s Incredible Unlikeliness of Being and many other places, the gill folds on the human embryo really are homologous to the folds on that of a fish. They just develop rather differently, explaining such oddities as the tortuous path of our vagus nerves. As for the whale’s pelvis having “nothing to do with walking on land”, by 1999 we already had extensive series of fossils linking whales to their terrestrial ancestors; there is an excellent review here by one of the scientists involved in Evolution Education and Outreach (free download), and whales evolution also features in an excellent video here . The development of secondary functions (exaptation) is commonplace. Thus mammals’ ear bones are vestigial relics of reptiles’ rear jawbones. Creationists often argue, as here, that natural selection can only remove, and not add. This riddle was solved 120 years ago, with the discovery of mutation. Mutations supply novelty; selection winnows it. Creationists agree in explaining away pre-modern human fossils, such as Lucy and numerous others already known by 1999, as being either apes, or humans. Unfortunately, they can never agree on which is which. And, something that I think believers in particular should find offensive, the theological absurdities of the final frame.

This post originally appeared here in January, at https://paulbraterman.wordpress.com/2016/01/08/how-to-lie-about-radiometric-dating-evolution-and-even-nuclear-physics/

Learning from creationists; radiocarbon dating

Radiocarbon dating only takes us back some 50,000 years. This makes it a much smaller threat to Young Earth creationists than, say, lead-uranium dating, which takes us back billions of years. So why do creationists single it out for attack? Because there are indeed problems with the most simple-minded application of the method, and it does not matter to the creationist that these problems have long since been solved. Creationists think, and argue, more like lawyers than like scientists. In the courtroom, changing your story under cross-examination will destroy your credibility, and yet this is what scientists do all the time. Scientists accept that even the most well-established findings are subject to revision and refinement; lawyers, like theologians, seek certainty whether the data justify it or not.

SymTalk

Leonard Sym’s presentation to Glasgow Skeptics in the Pub, 21 March 2016

This post is derived from a talk given by my friend Leonard Sym to Glasgow Skeptics in the Pub, and like Leonard I will follow Rapoport’s rules for debate, which specify that one should first summarise one’s opponents’ position in terms they would accept, next, list points of agreement, then point out what one has learnt from one’sopponents, and only at that stage embark on criticism.

I start with a simplified summary of the principles behind radiocarbon dating, without which the discussion would be meaningless. Most radiometric methods depend on measuring the amount of a parent radioactive isotope present in the sample, and the amount of the daughter into which it decays. Add up the amount of parent still present and the amount of daughter, and that gives you the amount of parent present initially.[1] If you know the rate constant for the decay, you now have enough information to work out how long has passed since the parent material was put in place. You can determine the rate constant by taking a known amount of parent, and counting the number of decays per second, as measured with a Geiger counter or a more reliable and up-to-date instrument such as fluorescence counter.

In the case of radiocarbon dating, the parent is carbon-14 and the daughter is nitrogen-14, which is lost from the sample.[2] So we can’t find the initial amount of parent in the way described above, because we don’t know the amount of daughter. This seems like a dead end, until we remember where carbon-14 comes from. Carbon-14 is formed in the upper atmosphere by the effects of cosmic ray bombardment on nitrogen, is rapidly converted to carbon-14 dioxide, and then mingles with the rest of the CO2 in the atmosphere (see Figure). If we assume a steady rate of bombardment, that means we will have a steady rate of production of carbon-14, and a steady state abundance of carbon-14 in the atmosphere, where the amount decaying each year is equal to the amount being formed.

Now consider what happens during the life of an organism, and after its death. As long as it is alive and metabolising, it will exchange carbon with its environment, taking it in directly as carbon dioxide by photosynthesis (for a plant) or indirectly as food (for an animal). At this stage, the proportion of carbon present as carbon-14 will be directly dependent on that in the atmosphere. But as soon as it stops metabolising, it stops exchanging, and the proportion present starts decaying according to the radioactive decay law, with a halflife of 5730 years. So it looks as if we can just use the proportion present in the atmosphere right now as a measure of the initial proportion, and compare it with the proportion remaining.

radiocarbon_sub1

Production and decay of carbon-14**

So far, so good. Now let me list the creationists’ objections:

1) As in all radiometric dating, the decay rate is assumed to be constant. What if this isn’t true?

2) The production rate is assumed constant. But this is unrealistic, since the intensity of cosmic ray bombardment is known to change over time

3) For 150 years, and especially in the last 50 years, we have been adding carbon dioxide from fossil fuels to the atmosphere, diluting the radiocarbon since all the radiocarbon in the fossil fuels will have long since decayed

4) Considerable amounts of carbon-14 were added to the atmosphere by nuclear testing in the 1950s, further undermining the assumptions

5) What if carbon-14 is less readily taken up than carbon-12 by plants? Won’t this undermine the reasoning?

6) We can check the method by applying it to materials whose age we know, but this will only serve where we have a good historical record, and this record only goes back, at best, some 5000 years

7) The Genesis flood, which in Young Earth accounts is responsible for the formation of our fossil fuel deposits, would have further upset the clock by burying huge amounts of carbon-12. Moreover, it could have been associated with an increase in the rate of carbon-14 production, making pre-flood specimens look much older than they really are.

LibbyBookWith the exception of the first and last, all these objections have some degree of plausibility, but unfortunately for the creationists they have all long since been answered, many of the answers being set out by Willard F. Libby, inventor of the method, in his 1955 book on the subject.

1) Radiometric decay constants are just not the kind of thing that could change, unless everything else changes at the same time. We have known since the work of George Gamow in 1928 that radioactive decay is what is known as a quantum mechanical tunnelling effect, and that its rates depends on such things as the strength of nuclear and electrical forces, the mass of fundamental particles, and Planck’s Constant h, which gives the scale for all quantum mechanical phenomena. If any of these had been different, we would not have had the same kind of physics and chemistry that we have today. But we know from their structure that ancient rocks were formed under the same rules as we have today, because they contain the same kinds of elements combined to make the same kinds of minerals. The creationists have published theoretical curves for changes in decay constants, but these have no basis in science, and are generated merely to make observations fit the biblical timeline.

2) From the outset, radiocarbon dating has relied on calibration, using objects for which dates were known from historical records, then tree ring counting extending back 10,000 years. This method works because all but the outermost layers of a tree are metabolically inert, and out of circulation. The most recent calibration comes from organic debris in varves (annual layers of sediment) deposited in a lake (Lake Suigetsu, in Japan) that happens to be free of turbulent inflows. This has made possible the establishment of a calibration curve going back 52,800  years.

Radiocarbon_bomb_spike.svg

Near doubling of atmospheric C14 in the Southern hemisphere, as the result of nuclear testing

3) and (4) There have indeed been major disruptions since 1950, but no one uses radiocarbon dating for such recent material. The situation in 1950 is regarded as a baseline, material from that year is the standard for comparison, and 1950 is the “present” in conventional dating of “years before present”

5) It will surprise many people to learn that plants really do take up carbon-14 less readily than carbon-12. One of the lies you were probably told at school is that all isotopes of the same element have precisely the same chemical properties. This is not true, and generally speaking, heavier isotopes are slightly more sluggish in their chemical reactions. this gives rise to the process known as isotopic fractionation.

NorthRonadsaySheep

These North Ronaldsay sheep, which feed on seaweed, will show different isotopic fraction from sheep fed on grass

This effect has been measured for photosynthesis. In addition to very small amounts of radiocarbon, atmospheric carbon dioxide contains roughly 1% of the stable isotope carbon-13, the remainder being carbon-12. Carbon dioxide in plants is, as expected, slightly depleted in carbon-13 relative to carbon-12, and the effect is far from trivial; around 27 thousands of carbon-13 abundance for most kinds of plant. We expect the effect to be twice as large for carbon-14, which, using the known 5730 year halflife of carbon-14, corresponds to 435 years; not trivial when dating historical artefacts. However, exactly the same effect will apply to the material used to set up the calibration, and the errors will systematically cancel out. Ideally, the fractional abundance of carbon-13 should be measured, as well as that of carbon-12, to calibrate out any minor fractionation effects, and this is less arduous than it sounds because nowadays carbon-14 abundance is measured by direct counting in a mass spectrometer rather than, as in the original studies, indirectly inferred from sample radioactivity.

For plants, it is straightforward to match like with like. Not so for material derived from animals, where the total amount of isotopic fractionation will depend on their diets, and also on what they have been eating.

6) This objection would have had some force in 1946, when the method was newly developed. However, as already explained, we now have direct calibration back to 52,800 years before present, beyond which the amount of remaining carbon-14 is so small that using current techniques the method becomes useless.

7) This is pure special pleading. If carbon-12 had been buried in the flood, the appropriate amount of carbon-14 would have been buried with it. And the ideas of a changed rate of production or decay have been dealt with under (1) and (2) above.

There are other “objections” based on the obvious fact that organisms like cave water snails, alive right now but deriving their carbon from limestone, will have radiocarbon apparent ages measured in thousands of years. I have discussed this before. And marine specimens will always contain less carbon-14 than terrestrial specimens of the same age, because of the time it takes for mixing between the atmosphere and surface waters, and again between surface waters and the depths.

So how should we respond to the self-styled “creation scientist”? The first, and most difficult, thing is to realise that he is been perfectly sincere. He is certain that his reading of the Bible is true; but the facts of geology are also true; and it is therefore his mission to create an account that reconciles the two. If this means the mountains must have skipped like rams, then that is how they must have skipped. He will feel no more absurd at this point, than the cosmologist feels in invoking a time when our Universe was smaller than a tennis ball and its temperature was trillions of degrees. Counter-arguments will be dismissed as so many minor anomalies that will no doubt be explained away in due course. If the creationist repeats long-refuted claims, that is because he believes that there are refutations of the refutation, even if he cannot immediately call them to mind, or does not have time to explain them properly. He will remember the weaknesses of his opponents’ arguments, and attack them, while suppressing the recollection of their strengths, and in the process he will create, and then triumphantly destroy, a series of straw men. You and I of course would never do such things, but your friends might when it comes to defending emotionally precious but logically fragile beliefs; consider, for example, what passes for political discussion in your favourite pub or chatroom.

And what does this mean for debating with creationists? Simply this: don’t do it. Such a debate, unlike a discussion between people willing to learn from each other, is a zero-sum game. He will project simplicity, sincerity, and certainty, and when you come to reply, you will sound as if you are making excuses. He will present anomalies (did I mention those 2000-year-old water snails?), and when you explain the special circumstances, you will be the one who seems guilty of special pleading. His followers will end up confirmed in their convictions, as will yours, and those in the middle will come away confirmed in their own initial conviction that there are two sides to the story, both worth hearing. Which there aren’t.

But does that mean that we can learn nothing from the creationists? Not at all. In terms of Rappaport’s rules of debate, the scientific community had already come up with arguments (1) through (6), and taken the necessary countermeasures, and so cannot be said to have learnt from the creationists. But both Leonard and I have learnt a great deal from examining the creationist claims. Be smart, and learn from everyone.*

1] It is of course necessary to eliminate errors caused by the movement of material, or the presence of daughter in the initial material. There are standard techniques for doing this, for instance by measuring non-radiogenic isotopes of the daughter material, and, these days, by microsampling of single crystalline grains

2] Even if it is not lost as N2 gas, it will be undetectable against the background of organic nitrogen compounds already present

*Ben Zomah, Mishnah Pirkei Avot 4a

** extra credit for spotting (a) the misleading labelling in the diagram (h/t John Gribbin), (b) the reference in the text to Psalm 114

There are other creationist objections to radiocarbon dating, based on sample contamination or simple misinterpretation of data, but these have been discussed elsewhere  and need not detain us.

Lecture scene from Glasgow Skeptics in the Pub Facebook page. Atmospheric carbon-14 diagram public domain, by Hokanomono via Wikipedia. North Ronaldsay sheep by Liz Burke, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=3499298. Radiocarbon cycle schematic from ANU Radiocarbon Dating Lab materials

How to lie about radiometric dating, evolution, and even nuclear physics

Have you heard the one about the live snail with a carbon-14 age of 3000 years? Or the lava erupted in 1800 in Hawaii with a potassium-argon age in the millions? It’s all true, true I tell you. But does this signify a major problem with radiometric dating?

Spoiler: no.

I don’t know who first dug up these examples, but they were popularised by the creationist comic-book writer Jack Chick, in a publication called “Big Daddy”. The first page, available here if you’re lucky (the links to Chick Publications only seem to work at random), shows a well-primed creationist student arguing with a singularly ill-informed biology professor. The professor has been leading such a sheltered life that he’s never met these creationist arguments before. And he doesn’t understand anything about evolution or dating of rocks or embryology or indeed anything else. Surprise! the student wins! A skilled cartoonist, Jack Chick manages to squeeze the largest number of fallacies into the smallest number of words. There is a crib sheet at the end of this post, listing all the fallacies I spotted myself; I just reached double figures but there may be more.

Evoa

dating

gillarch

vestigial

Of course, it doesn’t help that the Professor doesn’t know anything about whale ancestors:

WhaleAncestors

Or that the student is allowed to make the most absurd statements unchallenged, on the basis of a video by Kent Hovind:

evoc

But there’s more! At the end of page 1, which is also the end of your free sample I’m afraid, the student converts the Professor by pointing out that no one has ever actually seen gluons:

Gluons

Gluons2

But fear not; an answer is at hand, in the very next frame:

Gluons3
So Jesus must be the force that holds the atomic nucleus together. Convinced by this reasoning, the Professor accepts Jesus, announces that as a result he can no longer teach evolution, and is sacked.

Jack Chick, by the way, has just published another comic book at the age of 92. In it, a bright young man from a good Christian (i.e. creationist) home is seduced by Satan into believing in evolution, and when we last see him is heading straight for damnation. In the words of one of Satan’s many horned helpers, “Joe trusted evolution, not God, and became a jobless party animal.” And a criminal and a drug addict, and covered himself with tattoos, and died and went to hell. Tragic, and so easily avoidable.

I never managed to get to Page 13 of Big Daddy, which is what we really need; link (if it works for you) here. It didn’t work for me, but you’ll find a description of the contents by someone called Honus at talkorigins, and I’ve seen some of the relevant cartoons reproduced elsewhere. So you can either take Honus’s and my word for it, or go online to Chick Publications and buy 25 copies (minimum purchase) of the tract, which I am not about to do.

The really remarkable thing about the tract is that it actually gives the primary literature references to the results that is discussing. And the briefest perusal of this primary literature will show why the papers that Chick refers to, far from undermining radiometric dating, actually reinforce it.

That snail was not 3000 years old, but that really was its apparent radiocarbon age, because it was exchanging calcium carbonate in its shell with mineral calcium carbonate. And that makes all the difference, so you need to take such features of the environment into account.

Many readers will be familiar with the principle of carbon-14 dating. Carbon-14 decays with a half-life of 5730 years. Nonetheless, the fraction of carbon-14 in the atmosphere stays roughly constant (or did before we started adding to it by nuclear weapons testing, and diluting it with carbon dioxide from fossil fuels). That is because the upper atmosphere is bombarded with cosmic rays, which cause nuclear reactions that convert nitrogen-14 (stable) to carbon-14. Mixing distributes this radiocarbon through the atmosphere, where it is taken up by plants and, in due course, animals. As long as you are alive, you are part of the circulating pool of carbon, but as soon as you die, the carbon-14 in your body starts decaying. Of course, cosmic ray intensity is not really constant over a long period, but we can calibrate carbon-14 dates by comparison with carbon in tree rings (dendrochronology). The tree ring correction is small for most purposes, but matters for things like precise dating of Egyptian dynasties.

The point, of course, is that the carbon in the lettuce being fed to the snails is part of the general pool, but the carbon in calcium carbonate minerals is radiochemically dead, having been out of circulation for a long time. What the paper really showed was that the snail exchanges carbonate in its shell with carbonate from dissolved minerals, giving a spurious depletion of radiocarbon in the snail. You will find the story in Science, 1963, p. 637 (paywall, sorry, but summary here).

What about these rocks in Hawaii? Here again the paper is behind a pay wall, but if you follow this link it will take you to the title and abstract, which is all you need. In fact, the title alone is all you need: “Radiogenic helium and argon in ultramafic inclusions from Hawaii”. Inclusions. And in case that’s not clear enough, the abstract tells you that the work is all about the dating of xenoliths. Xeno- foreign, as in xenophobia; lith rock, as in monolith. Look at the paper in more detail, if you can get access to it, and you will find that the excess argon is only found in bubbles of fluid within the rock, that bits of rock that aren’t bubbly don’t show any, and that there is circumstantial evidence that the argon comes from deep within the Earth’s mantle, not radioactive decay in the lava itself.

Anomalies happen all the time in geology. They are, in the original sense of the expression, exceptions that prove the rule; if there were no rule, we would not consider them exceptional. Uranium-lead and potassium-argon dates of rocks usually agree, but not if the rock has been so strongly heated that argon gas can escape. Whole rock dates can be misleading, as in the example of the Hawaiian volcano, if the rock has been contaminated from some source, in this case fluid from the mantle. So far from undermining the method, these anomalies add further information about the sample. In much the same way, radiocarbon dates will be anomalous if some of the carbon comes from inorganic sources, as in the case discussed above, and the anomaly might even be used to tell us something about the specimen’s history and diet.

Now here’s the bit that I really don’t understand. What is going on in Jack Chick’s mind, when he gives us this stuff? I assume that he is an honest person of goodwill, who is doing his best. He really believes that because I and most readers here accept the fact of evolution, we are going to be punished in hell for ever. Being a kindly man, he really doesn’t want that to happen, so he is doing his very best to convince us of the error of our ways.

So why does he do it by pointing us towards papers that say the very opposite of what he says they say? I can only speculate that this is the result of what psychologists call confirmation bias, which leads to interpreting new information, however perversely, in a way that supports what you already think. And when we come to creationism, the motivation for bias is extreme. Remember that we are talking about people who really believe (a) that if you don’t accept salvation through Jesus you are going to go to hell, and (b) that the doctrine of salvation through Jesus only makes sense if the biblical Fall is a historical fact. The papers I’ve mentioned above show that under certain rather special circumstances, radiometric dating will give you the wrong answer unless you take those circumstances into account. Young Earth creationists, knowing that their entire worldview depends on refuting radiometric dating, pounce on these examples as evidence that the method is unreliable. Which of course it is, if you don’t do it right. So what?

All of which gives me uncomfortable pause for two reasons. If creationists are so blinded by confirmation bias, what hope is there of reasoning with them? And if I see my intellectual opponents displaying confirmation bias, completely oblivious to what they are doing, what makes me think that I am any different?

h/t Sensuous Curmudgeon for tip-off about Jack Chick’s latest. Whale ancestors illustrated (Ambulocetus and Pakicetus) copyright JGM Thewissen; may be reproduced for non-commercial educational purposes.

IncredibleCrib sheet: Definition as obfuscation. Misdefinition of science to exclude all indirect inference (although even Young Earth creationists accept the fact of an Ice Age on geological evidence). Macroevolution, if the word means anything, means major change, and this takes more time than we have been watching. So of course we’ve never seen it. Similar fossils do indeed imply similar ages, but the order of these ages has been known for nearly 200 years on the basis of stratigraphy, and absolute ages established for over 100 years now by radiometric dating. Polystrate fossils were explained in 1868; the explanation is much the same today. New Scientist really did point out in 1997 that it is silly to carry on using Haeckel’s highly questionable drawings, as some still do, when we now have a much more detailed information. But, as explained in Alice Roberts’s Incredible Unlikeliness of Being and many other places, the gill folds on the human embryo really are homologous to the folds on that of a fish. They just develop rather differently, explaining such oddities as the tortuous path of our vagus nerves. As for the whale’s pelvis having “nothing to do with walking on land”, by 1999 we already had extensive series of fossils linking whales to their terrestrial ancestors; there is an excellent review here by one of the scientists involved in Evolution Education and Outreach (free download), and whales evolution also features in an excellent video here . The development of secondary functions (exaptation) is commonplace. Thus mammals’ ear bones are vestigial relics of reptiles’ rear jawbones. Creationists often argue, as here, that natural selection can only remove, and not add. This riddle was solved 120 years ago, with the discovery of mutation. Mutations supply novelty; selection winnows it. Creationists agree in explaining away pre-modern human fossils, such as Lucy and numerous others already known by 1999, as being either apes, or humans. Unfortunately, they can never agree on which is which. And, something that I think believers in particular should find offensive, the theological absurdities of the final frame.

Evolution and creationism; a valuable new resource

The Science Meets Religion website, by the information scientist David Bailey, has a Q&A page that addresses the most common and most plausible scientific objections raised by creationists to the science of evolution. Twenty-six specific questions are chosen, and answered in a series of brief essays on such topics as complexity, information theory, radiometric dating, fossils, speciation, and thermodynamics. For each of these, Bailey gives a straightforward statement of the creationist arguments, and then succinctly lays out the evidence for the contrary viewpoint. The rebuttals of creationism are all the more crushing for being written with judicial dispassion.

HumanEvolution

Our family tree, since we parted company with other chimpanzees

The style is accessible enough for a high school student to read with enjoyment, but the scholarship behind it is impressive. For example, the discussion of alleged missing links between humans and non-human apes gives fourteen separate references to discoveries in the last eventful half dozen years. The essays on dating methods list, and refute, nine separate creationist claims, and refer to numerous scientific sources. These include authoritative on-line reviews such as Wiens and Dalrymple on radiometric dating and Dalrymple on the fallacies in the “creation science” arguments for a young Earth, as well as some key papers fron the primary research literature. The bibliography has (at present) 764 entries, more than 50 of them from 2015, refers to the scientific, creationist, and theological literature, as well as human behaviour and its link (or not) to religious belief, and is regularly updated (most recently last September). You will find here articles on everything from the latest word on Homo naledi to the microwave spectra of distant galaxies to divorce rates.

Bailey is himself a committed Christian, and joins other Christian writers such as Dennis Venema at Biologos and Roger Wiens (whose web page on radiometric dating I cite above) in showing that the “controversy” between evolution and creationism is not so much a conflict between science and religion, as a battle within religion itself. As the Scopes trial anniversary reminded us, this civil war in its current form dates back a century, to the conflict between Modernists and Fundamentalists. (The underlying issues, of course, are far older, and Bailey’s bibliography gives three references to Augustine.)

Some of my fellow unbelievers think the best way to advance the cause of enlightenment is to attack religion. I regard this course as mistaken, psychologically, philosophically, historically, educationally, and tactically. I think that the followers of any religion face major problems, but they are their problems, and it is not my place to lecture them on how they should be resolved.

In addition, affirmations of the validity of evolution and Old Earth geology have far greater power when they come from within the body of believers. Anyone who chooses to be misled by the claim that evolution is uncertain because it is a theory, or who prefers the absurdities of Flood Geology to the evidence of their own eyes, is in need of intellectual liberation, but such liberation can only come from within, and will come far more readily given the encouragement of members of their own faith community.

I conclude by illustrating this point with a paragraph from Bailey’s critique of Intelligent Design:

One overriding difficulty with both the creationist and intelligent design movements is that invoking a Creator or Designer whenever one encounters a difficult question is a “thinking stopper.” Such an approach places numerous grand questions of our existence off-limits to human investigation, buried in the inscrutable mind of a mysterious supreme Being: “Why was the earth (or the universe in general) designed the way it was?” “How did the design and creative processes proceed?” “What physical laws were employed?” “Why those particular laws?” “What prompted the creation?” “Have other earths or universes been designed or created?” “Where are they?” Surely there is a more fruitful avenue for finding a harmony between science and religion than just saying “God created and/or designed it that way” and then deeming it either unnecessary or inappropriate to inquire further.

Here we have a powerful statement, far more powerful because it comes from a committed believer,  of why such doctrines are not merely stupid irrelevancies, but active obstacles in the search for religious, as well as scientific, understanding.

David Bailey’s professional website is here; his professional homes are Lawrence Berkeley Laboratory and (current primary affiliation) University of California, Davis. I learnt of his work through a post on Scott Buchanan’s Letters to Creationists. David uses the hominin evolutionary tree that I show here (taken from Scientific American’s September 2014 special issue on evolution) to illustrate what we do and do not know about our species’ grandparents and great-uncles.

Coral reefs are too old to be young!

I can add little to this excellent piece. however variable growth rate may be, total height divided by maximum growth rate gives a *lower limit* the age, which is enough to refute the Young Earth creationist. There was at one time hope that fine structure of coral growth bands would give information about the lengths of the day and the month in the Proterozoic, but because laboratory studies showed these structures to be sensitive to accidents of time and tide, their place has now been taken by rhythmites, variations in the fine structure of the annual banding of sediments (Proterozoic and Precambrian day and month lengths are now studied using rhythmites, fine structure in the annual banding of sediments; Williams, Reviews of Geophysics 38, 1, 2000).  234U-230Th dating is one of the best methods available for carbonate rocks in the 10,000 year range, and the creationist claim that decay rates could have been different in the past ignores the fact, known since 1928, that these rates are the inevitable consequence of time-dependent quantum mechanics and the fundamental constants of nature.

Age of Rocks

Corals are among the most valuable indicators of past climate conditions, due to their sensitivity to water depth, temperature, and acidity. We can infer from the age and depth of ancient reefs, for example, how global sea level has varied in response to past intervals of warming and cooling. Since reefs are formed by organisms secreting calcite, moreover, their isotopic and elemental chemistry is directly related to the temperature and salinity of the water in which they lived. But best of all, reefs form in the tropics (30°S – 30°N), which means that the researchers studying them do so while scuba diving in warm seas along pristine beaches. Perhaps it’s time for a career change?

Despite that corals can provide a wealth of information to geologists and climatologists studying the past, these data are useful only if we know the precise age of the sample! How then do we date…

View original post 1,306 more words

100 Reasons the Earth is Old (reblogged from Age Of Rocks)

I am posting this page from Jonathan Baker’s Age of Rocks here for several reasons. It is an extremely useful resource, well researched and well-written; the author addresses creationists with humanity and respect, even as he demolishes their position; and the author himself is a committed Christian (why that should matter to me, a free-thinking atheist, is something I explain below).

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Siccar Point. Horizontal Devonian sandstone over uptilted Silurian greywacke. Click and re-click to enlarge

The evidence presented ranges from tree rings to topography to sedimentology to physical geography to archaeology and anthropology to geochemistry to the fossil record to radiometric dating to astrophysics. Many of these are topics I have touched on, for example in my discussions of the unconformity at Siccar Point, and the slowly cooled multiple lava flows and palaeosols of the Giants’ Causeway.

In each case, the reasoning is briefly described, with links to more detailed discussions, many framed specifically to refute creationist claims. By relegating those claims to second place, the author avoids the common mistake of teaching the very error that he is warning against. At the same time, he pays a respectful attention to his opponents, for reasons that he explains elsewhere in his blog, even as he dismantles their arguments.

Like the authors of EvoAnth  and Leaving Fundamentalism, the author is at present a graduate student; welcome examples of how the web is democratising discourse, and how young scientists and educators are using the opportunity.

I commend this piece to all those who have to deal with creationism in schools and elsewhere, alongside such classics as 29+ Evidences for Macroevolution and Index to Creationist Claims, and hope that the author will continue to update and add to it as his own career progresses.

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Giants’ Causeway: interbasaltic laterite palaeosol between lava flows at The Chimneys. Click and reclick to enlarge

Like Dennis Venema at Biologos and Robert Wiens at Radiometric Dating – A Christian Perspective, the author is a committed Christian, thus helping to give the lie to the claim Read the rest of this entry

Glasgow’s Intelligent Design Director has ”open mind” on age of Earth

Al Furqan Mosque, Glasgow, in whose Community Hall Dr Noble spoke last Friday (November 28) on ‘Intelligent Design: Myth or Reality?’

See how many errors of fact and logic you can find in what Dr Noble, Director of Glasgow’s own Centre for Intelligent Design, said when my friend and Scottish Secular Society colleague, Garry Otton, asked him about the age of the Earth. This was on the occasion of his visiting a mosque as part of the activities of Scotland’s Interfaith Council, which receives £9,000,000 a year of taxpayer money. I offering him  space to reply, but he tells me that “I really don’t think this kind of speculative trivia deserves a considered response.”

Dr Noble said that the scientific consensus is about 3 billion years old, but there is a lot of uncertainty about all scientific things and some think the Earth’s only thousands of years old. He thinks the Earth might be old, but human beings might be “much younger than most scientists would accept”. A geologist has shown him a piece of rock, dated as 300 million years old, but containing a seam of coal carbon-14 dated at 40,000 years. And carbon dating only goes back to around 50,000 years, so [he said with heavy emphasis] “the error is not in the date of the coal.” All methods depend on judgements about initial conditions that we have no way of knowing. The scientific consensus can be very arrogant, so he doesn’t have a serious problem with an old Earth, but is not completely convinced.

Here is my list of errors; let me know if you spot others:

First, and least important, that number, 3 billion years. It should of course be around 4. 5 billion years.

From the fact that carbon-14 is useless beyond 50,000 years, Dr Noble infers that the error is “not in the date of the coal.” The exact opposite is true. The 50,000 limit is the limit of the method, showing that it cannot be used for more ancient deposits.

Actually, it has long been known that ancient coal cannot be dated by carbon-14, because it gives spurious and erratic young(ish) ages, between 20,000 and 50,000 years. This has thwarted attempts to use it as a standard background (see e.g. this 1939 paper). One percent contamination by contemporary material of the area sampled will reduce the apparent age to less than the 40,000 years that Dr Noble quotes, and other potential problems include the presence of modern bacteria (well established by 1931) and carbon-14 generation in the coal from the nitrogen-14 present, as an indirect effect of the radioactive decay of heavy elements in the coal.

I don’t know where Dr Noble got his numbers from, but they are identical with those quoted in a 2002 Talkorigins article, which discusses and dismisses the alleged anomaly. A fuller and more recent critical analysis of claims of detecting carbon-14 in ancient materials  can be found at http://www.asa3.org/ASA/education/origins/carbon-kb.htm#22 (ASA in this address stands for American Scientific Affiliation, an organisation of Christians who reject attempts such as Dr Noble’s to discard the plain science of evolution and an ancient Earth; the author, Kirk Bertsche, holds a Ph.D. for his work on radiocarbon methods, and an MA in Exegetical Theology from Western Seminary, Portland, Oregon).

As for our judgments about initial conditions, we can check these in at least four separate ways. Firstly, careful mineralogy, picking out well isolated samples or even well-defined individual crystallites. Secondly, available since the 1940s, what are known as isochron methods, which use non-radiogenic isotopes as internal markers. Thirdly, SHRIMP (sensitive high resolution ion microprobe) methods, available since 1980, which allow assessment even of selected regions within crystallites, giving valuable information about thermal history and element mobility; I have a friend who does this for a living. Finally, the good agreement of disparate methods (this was mentioned to Dr Noble) provides cross-validation, and the rare occasions when this does not occur (for example in rocks with anomalously young potassium-argon ages) are themselves highly informative (in this example, regarding subsequent heating episodes). Radiometric Dating, A Christian Perspective, by Roger Wiens,  principal investigator of the Mars Curiosity Rover’s chemical laser analysis team, gives an excellent perspective on this and other alleged problems.

It is just not true that there is a lot of uncertainty about all scientific things. There is no real uncertainty about the age of the Earth, any more than there is real uncertainty about the existence of the atoms of which it is composed. Dr Noble himself would be very upset if I were to allege that there is a lot of uncertainty about the abstruse area of inorganic chemistry in which he obtained his own Ph.D. over 40 years ago.[1] And yes, we should keep an open mind, but not so open that our brains fall out.[2]

So how did Dr Noble, who evidently still thinks of himself as a scientist, come to make such a concatenation of elementary errors? I would suggest confirmation bias, selecting evidence that supports a view already adopted for very different reasons. And in this case, that view is identified by his wish to take seriously the possibility that human beings might be “much younger than most scientists would accept”. Dr Noble belongs to a church that believes in the “entire trustworthiness” of Scripture, and perhaps he looks kindly on the idea that human beings were specially created in the past few thousand years. But if this is the case, the biological science that shows we are sister species to chimpanzees, and the Earth science that dates undeniably human skulls back to more than 100,000 years ago, must be denounced as unreliable. The rest follows.

Added note: Some commentators have inferred that Dr Noble is a six-day creationist. I, however, interpret his careful distinction between the age of the Earth and the age of humanity a showing a more broad-minded perspective than that, one which also grants credibility to day-age and gap versions of creationism.  Here day-age accepts the order of events in Genesis, but allows that each “day” may refer to an era. “Gap” allows geological tme in between Genesis 1:1 and Genesi 1:2. Both were originally attempts by conservative theologians to accommodate biblical literalism to early 19th century geology, and both, crucially, accept a historical Eden a few thousand years ago, and separate creation of kinds. I deliberately chose impeccably Christian sources for the geological background, to highlight the possibility that Dr Noble’s hermeneutics may be as selective as his geology.

1] The Preparation and Properties of Tungsten Hexafluoride Derivatives, Glasgow, 1970.

2] For the history of this phrase see here.

Antifragility and Anomaly; Why Science Works

Scientific theories are antifragile; they thrive on anomalies.

Some things are fragile – they break. Some are robust – they can withstand harsh treatment. But the most interesting kind are antifragile, emerging strengthened and enriched from challenges. Whatever does not kill them makes them stronger. Science is as successful as it is, because science as a whole, and even individual scientific theories, are antifragile.

AntifragileWe owe the term “antifragile” to the financier and thinker Nassim Nicholas Taleb, author of Fooled by Randomness and Black Swan. Taleb describes his latest book, Antifragile; Things that Gain from Disorder, as the intellectual underpinning of those earlier works, since it formalises his earlier reflections. Antifragility is the true opposite of fragility. Unlike mere robustness, it is the ability to actually profit from misadventure. A porcelain cup is fragile, and shatters if dropped. A plastic cup, being robust, will not be any the worse for such an experience, but it will not be any the better for it either. Contrast the human immune system. Being antifragile, it is improved by stresses. Having been challenged by an infection, it will be primed to respond more effectively to similar challenges in the future, because it has learned to recognise the infection as an invader. There are deep connections between randomness, uncertainty, novelty, information, and learning, and natural selection in an uncertain world favours antifragile systems because they learn from experience [1].

Good safety systems are antifragile. Accidents will happen, and of their nature cannot always be foreseen, but each accident can be analysed retrospectively and procedures adjusted to anticipate similar challenges in the future. Moreover, experience shows that experience is more persuasive than foresight, even when the mishap itself has actually been foreseen.

This may not be the very best moment to mention the fact, but air transport safety systems are antifragile. Air travel is far safer than it was a generation ago, because we have learned from past mistakes. The mistakes were part of the process, if only because brutal reality is more effective than prediction at promoting change. Thus locking off the cockpit door securely from the cabin had been discussed earlier, but only became standard practice after the 9/11 hijackings, and after the recent Malaysian Airlines case we can expect the obviously overdue checking of passports against the Interpol list of those stolen.

Number of deaths from airline accidents per year (red line is rolling 5-year average); note steady decline since the 1970s, despite greatly increased traffic. From http://aviation-safety.net/statistics/period/stats.php?cat=A1

Among the things that Taleb lists as fragile are scientific theories. Scientific theories are indeed vulnerable to disproof, since they must be tested against reality. The simplest way to describe this is to say that they must be falsifiable by experience, a criterion associated with the name of Karl Popper. In the popular imagination at least, however well established the theory may be from past experience, it could at any time be refuted in the future by a single observation that differs from what is theoretically predicted. If so, scientific theories would indeed be fragile, since they could not survive a single shock.

But that is not what really happens. Well-established theories have already explained a wide range of observations, and will not readily be destroyed by a single counterexample. On the contrary, they usually emerge all the stronger for accommodating to it. If the theory already has a great deal going for it, we do not regard the counter-example as a refutation, but rather as an anomaly. It is a deviation from regular behaviour (Greek: an-, negation, homalos, even) but not necessarily a sufficient reason to deny that the regularity exists. Although the anomaly seems to be an imperfection, we may still be able to interpret it in a way that deepens and extends our understanding of the theory, and our knowledge of the world itself. When we can do this, the theory has not been damaged by being challenged; quite the reverse. It has emerged stronger, and our confidence in it is enhanced. New challenges cannot be foreseen, whatever scientists may have to pretend when writing their funding proposals, but for that very reason, in the process of responding to them, the theory generates new information. This is exactly the kind of behaviour that Taleb calls antifragile.

A few examples will illustrate the point. Scientists themselves have long recognised the importance of anomalies in discovery; as Isaac Asimov put it,

The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’, but ‘That’s funny …’

Take for instance Newton’s theory of planetary motion (I owe this example to Philip Kitcher’s book, Abusing Science). In this theory, to a first approximation, planets orbit the Sun in elliptical orbits, under the influence of the Sun’s gravitational attraction. But this is not quite what happens, because the planets also exert gravitational attraction on each other. A more exact description of their motion needs to take this additional effect into account, and the theory tells us how to do this, using the inverse square law for gravitational attraction. The orbit of Uranus, for example, is measurably perturbed by the gravitational influences of Jupiter and Saturn. But calculations on this basis did not lead to accurate predictions of its path. A direct conflict between theory and observation, but did this destroyNewton celestial mechanics? Did people throw up their hands in despair and abandon the attempt to predict the next lunar eclipse? Of course not. There was indeed an anomaly, but this was hardly sufficient reason to discard a theory that tied together the motions of the moon, the planets, and even the proverbial apple. Indeed, the theory itself told astronomers what to look for; another planet waiting to be discovered, whose position could itself be calculated from the “error” in the calculated orbit of Uranus. And there it was, a new planet, which we now call Neptune. This was not a refutation of the theory, but a further confirmation. The theory, in other words, emerged stronger from the challenge posed by the deviation from its initial predictions. It had displayed antifragility. The Newtonian description of the planets and their motions had survived, and had gained further information – the existence of a major new planet, no less – in the process. Taleb himself mentions this case, but dismisses it as untypical. Ironically, since the importance of the untypical is central to his own thinking.

Planets2013.jpg

The Sun and planets of the Solar System. Sizes are to scale, distances and illumination are not
(source: Wikipedia)

Now contrast this with the problem posed by the orbit of the planet Mercury. Again, the orbit deviated from the Newtonian prediction. But this time, the search for a new planet to account for the discrepancies was unsuccessful. It was only after the development of Einstein’s general theory of relativity that it became possible to explain the planet’s motion.

So what follows from this latter case? Do we say that Newton’s theory was wrong? No. We say that it was incomplete. It provides an adequate description of celestial mechanics, provided speeds are not too high (compared with the speed of light) and gravitational fields are not too strong. When we say this, we have not subtracted from Newton’s theory. On the contrary, we have added to it, by describing the conditions under which we can expect it to break down, and by subsuming it in a larger, more general, theory. It has been enhanced, as a jewel is enhanced by its setting.

Actually, if we are looking for extreme accuracy, we need to take into account relativistic refinements to Newton even when discussing everyday objects. Otherwise, we could not have a global positioning system good enough to guide a tractor without steering it into a ditch.

My next example comes from chemistry. Put together Lavoisier’s theory of chemical elements with Dalton’s theory of atoms, and you would expect that all the atoms of a particular element, wherever they were found, would have exactly the same properties. In particular, the density of the gas nitrogen, which depends on the mass of the individual nitrogen atoms, should be exactly the same whether the nitrogen is extracted from the atmosphere, or is chemically prepared by the decomposition of a nitrogen-containing compound, such as ammonia.

The densities of some gases, such as nitrogen and oxygen, are tantalisingly close to being whole number multiples of the density of hydrogen, and it was suspected (correctly) that there was a fundamental reason for this. That is why the physicist Lord Rayleigh, in the early 1890s, decided to re-measure the density of nitrogen as accurately as possible. Yet, however much care he took, he found that the density of the gas that he prepared from air was always measurably greater than that of the gas prepared from ammonia. In predicting the densities to be the same, Rayleigh had clearly made a mistake of some kind, but, as Taleb points out,mistakes contain information, which is why they are valuable. The mistake in this case is the assumption that once you have removed oxygen, water vapour, and other minor components from air, nitrogen is the only thing you are left with. The chemist William Ramsay realised that “atmospheric nitrogen” must also contain something else, and that something else turned out to be very interesting indeed. It was the gas argon, which actually makes up 1% of our atmosphere, but had hitherto escaped detection because of its lack of chemical reactivity. And not only was argon a new element, but it was a representative of an entire group of new elements, the noble gases, whose inertness provides a clue to the very nature of chemical bonding.

A further anomaly was discovered in the early years of the 20th century. Different chemically pure samples of one particular element, lead, really did have different densities, depending on the source of the ore. Facts like this were involved in the discovery of isotopes, versions of the same element with different numbers of neutrons in the nucleus, and therefore different atomic mass. We now know that contrary to classical atomic theory, the different isotopes of an element have very slightly different chemical reactivities, and that by examining the isotopic composition of a mineral, with the high accuracy possible in modern mass spectrometers, we can draw inferences about its geological history.

Finally, an example from geology, and more specifically from the radiometric dating of rocks. I chose this example because the anomaly is discussed and explained in the original scientific literature, despite which creationists shamelessly use it as a reason for rejecting the very science that it extends and validates.

The principle of radioactive dating is simple. Some elements are radioactive. They decay at a known rate, and by comparing the amount of decay product in a mineral grain with the amount of parent material remaining, we can infer how long the process has been going on, and hence the time since the formation of that particular grain. This method has been in use for over a century. Since many rocks contain more than one radioactive isotope, it is often possible to obtain more than one date for the same sample, and the fact that such dates are generally in excellent agreement enhances our confidence in the technique. In its simplest form, the method requires that both parent and daughter have been immobile, but more refined arithmetical techniques using non-radiogenic isotopes as internal standards can correct for such movement, and have been in use since the 1940s.

Cardenas basalt, at bottom of Grand Canyon. Photo Don Searls via Wikipedia

Now considers the Cardenas basalt, near the base of the Grand Canyon. This has been carefully dated using two distinct methods, rubidium-strontium (Rb/Sr), and potassium-argon. Rb/Sr is an excellent method for older rocks, because the rubidium parent has a long half life, and because both elements will be firmly bound in their mineral matrix. Potassium-argon is in this latter regard at the other extreme. Potassium occurs in rocks as a component of aluminosilicate minerals, which hold it firmly in place. Argon, on the other hand, is as we have already seen an unreactive gas. When rock is chemically reworked or melted, the argon is able to escape, and as we have seen the argon so formed makes up 1% of our atmosphere.

Heat a rock sufficiently, and some of the argon will be able to escape between the grains, while its parent potassium, like most other components including rubidium and strontium, remains firmly in place. So if we now apply potassium-argon dating, we will get an underestimate of the true age because we will have retained all of the parent, but lost part of the product. By contrast, the Rb/Sr dating is unaffected because both parent and daughter are immobile. This is exactly what was found in the case of the Cardenas basalt. Rb/Sr tells us that this basalt represents a lava flow some 1100 million years ago, and dating by various methods of the rocks above and below, and through which is has penetrated, confirms this. The potassium-argon dates are younger; how much younger depends on the exact chemical composition of the part of the rock sampled, and hence on its viscosity during later heating (see here, p. 255, for details). The Grand Canyon has exposed these ancient rocks, buried elsewhere beneath a mile of sediments, and their detailed examination continues to yield new information about the tectonic forces at work in the distant past.

The elegant ellipses of planetary orbits are perturbed by their mutual interactions, The identical atoms of the early modern atomic theory turn out to be to a mixture of different isotopes. The single date for the formation of a rock must at times be supplemented by other dates from its history. T. H. Huxley may have spoken of “The great tragedy of Science — the slaying of a beautiful hypothesis by an ugly fact,” but mature theories are in general neither as elegant nor as vulnerable as newly coined hypotheses. They will have undergone mutation and Darwinian evolution in the marketplace, and demonstrated their ability to survive, warts and all.

[1] Such is the central theme of this meandering, often insightful, and frequently infuriating book; for the review that most closely matches my own opinion, see here. Ironically, I found it more convincing at the level of general understanding than at the level of specific application, in direct contrast to the author’s own view of how ideas shape up.

An earlier version of this post was published at: http://www.3quarksdaily.com/3quarksdaily/2014/03/antifragility-and-anomaly-why-science-works.html

Kelvin, Rutherford, and the Age of the Earth: I, The Myth

File:Lord Kelvin photograph.jpg

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.[1]

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.[2] 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.[3] 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.[4] 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.

File:ConvectionCells.svg

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. [5] 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

[1] Detailed (and sometimes mildly discordant) scholarly studies hereherehere and here, and references therein.

[2] Comte, Positive Philosophy, Bk II Ch 1

[3] Annalen der Physik 185, 148–150, 275-301 (1860).

[4] 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.

[5] 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.

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