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:

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.





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


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


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:



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

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/

Clergy back call to remove unelected clergy from Council committees in Scotland

Petition “…to remove the constitutional anomaly that imposes unelected Church appointees on Local Authority Education Committees” (signatures still urgently needed; you can sign and comment here)


Image from Clergy Letter Project website home page

This just in, to the Public Petitions Committee, from Michael Zimmerman, Executive Director of the Clergy Letter Project, which exists to promote the acceptance and celebration of science among believers. It states, more clearly than I could ever do, the reasons theological, educational, and ethical for removing the existing power of the Churches to nominate three representatives to Scottish Local Authority Education Committees; a large enough bloc to swing the balance of power on 19 of Scotland’s 32 such Committees:

I am writing in reference to “PE01623: Unelected church appointees on Local Authority Education Committees” and in my capacity as the Executive Director of The Clergy Letter Project.  The Clergy Letter Project is an organization of more than 15,000 ordained members of the clergy who believe that religion and science can be fully compatible.  Additionally, our members believe that religious doctrine should not influence the content of secular education.    The underlying premises of The Clergy Letter Project are two-fold.  On the one hand, many of those who are promoting a religious presence in secular educational institutions are doing so on very narrow grounds.  In other words, in almost every case, the specific educational goals being promoted are completely at odds with the religious beliefs of many other individuals.  On the other hand, many who are promoting a religious presence in secular educational institutions believe that their religious beliefs trump science when they see the two in conflict.  The thousands of religious leaders who comprise The Clergy Letter Project understand that the importance of religion lies in its spiritual value rather than in any particular pronouncements about the material world.

Mandating that three religious leaders must be appointed to each Local Authority Education Committee privileges religion in a manner that is likely to do damage to the educational opportunities open to students.  Let me hasten to say that there is absolutely nothing wrong with any particular religious leader serving on a Local Authority Education Committee, if that is the will of the community.  As citizens, religious leaders should have all the rights that every other member of the community has.  But mandating seats on the Committees for religious leaders simply because of their religious beliefs is unfair and runs the risk of severely compromising the very nature of the education the Local Committees were established to protect.

I urge you to take this petition very seriously and take steps to ensure that Scottish students receive the highest quality of education possible.

Michael Zimmerman

Executive Director The Clergy Letter Project



Natural selection in our species during the last two millennia

Evolution science in action

Why Evolution Is True

A question I’m always asked in popular lectures on evolution is this: “Are humans still evolving?” The answer I give is “Yes, but we have good evidence for such evolution in only a handful of traits: evolution of earlier reproductive maturity in females, later menopause, and selection for reduced blood pressure and a few other traits related to heart disease.” That is based on longitudinal studies of human health over decades, observing changes in these traits and presumed estimates of the genetic basis of their variation.

Now, however, we can, by DNA sequencing, look at DNA directly, and with some fancy statistical footwork, get an idea of which genes have changed in frequency so fast that they must have been due to positive natural selection. That’s the subject of a new paper in Science by Yair Field et al. (reference and free download below).  The authors conclude that several…

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#ElectNotSelect; “Remove Church Appointees” makes front page of Herald


From front page, [Glasgow] Herald, 7 Oct 2016; click to enlarge

You can sign here: https://www.parliament.scot/GettingInvolved/Petitions/ChurchAppointees

And you can see a fuller version of the story in the Herald online here.

Why sign? For the moment, I’ll just repeat what I said yesterday:

Three of the full voting members of every Local Authority Education Committee in Scotland are unelected nominees of the Churches, whether the voters or their elected representatives want them there or not.

And because this is Scotland, a country that regards its people with respect, the petition process means something. Enough, in this case, to actually change things. The petition will be discussed by Holyrood’s Public Petitions Committee, who will, we hope, pass it on to the Education and Skills Committee, the Government will be asked to state its position, the Educational Institute of Scotland, the Consortium of Scottish Local Authorities, and other interested parties will be written to …

What happens then? That depends very much on you. Hierarchies never give up power without a struggle. There will be mobilisation in defence of the indefensible, and no Government, and very few individual MSPs, will be willing to stand up for change unless we have shown them that there is a real demand for it. That is why your signature matters.

What more can you do? Firstly, and most effectively in terms of return on time spent, pass it on. Use your social accounts, Facebook, Twitter, whatever. Next, let your own MSPs know how you feel; you can contact them at http://www.parliament.scot/msps/current-msps.aspx. And keep your eyes on the newspapers and their comments sections; write to them if you feel so moved. Never have concerned individuals had so many ways of making their voices heard. Use them.

#ElectNotSelect; Remove Church appointees imposed on Scottish Education Committees


Debating chamber at Holyrood. Photo Mogens Engelund via Wikipedia

Sign the petition here, and your signature will go straight to Holyrood, and help get rid of the absurd legal relic whereby

Three of the full voting members of every Local Authority Education Committee in Scotland are unelected nominees of the Churches, whether the voters or their elected representatives want them there or not.

The time is ripe for change. Our petition, Unelected church appointees on Local Authority Education Committees, has widespread cross-party support in principle among MSPs. But we need to show that there is public support for change, or timidity will triumph.

Click on link to see the full petition, and, if you agree, to sign. Remember that the Education Committees, on which these Church appointees sit, control a larger part of Council budgets than any other Committee. They are the ultimate employers of School Principals and teachers, as well as being represented on senior teacher selection panels.  They decide on the opening and closing of schools, and whether a school should be denominational or nondenominational, and control local practice in such matters as religious education, religious observance, and instruction about sex in human relationships. The Church appointees vote on these matters, and in addition discuss policy directly with Council officials. You will find a full listing of the appointees, how they came to be selected (e.g. only answer to a newspaper advertisement; nominated himself after losing an election), and which ones are known Young Earth creationists (half a dozen; many more probable) here.

Why are these appointees there? Because District Council Education Committees must, by law dating back to 1929, include three appointees of the Churches, nominated by Church hierarchies, and immune to the electoral process. These nominees actually hold the balance of power in 19 out of Scotland’s 32 Education Committees, whether anyone wants them there or not, and they don’t even need to declare their outside interests!

Who selects them? One is selected by the Church of Scotland, one by the Catholic Church, and one by a third religious organisation (it must be religious) chosen by the Council with regard to local demographics. Fringe creationist churches are overrepresented here, as are the Episcopalians, with a mere 25,000 communicants but ten allotted slots.

This blemish on our democracy is also a breach of our right to equal treatment under the law, because it creates positions of power within our system of government that are only open to certain believers. Believers, moreover, in dogmas no longer accepted* by most Scots young enough to have children within the school system.

Since we are dealing with the law on a devolved matter, education, the Scottish Parliament is the only body with the power to remove this constitutional anachronism, which is why the Scottish Secular Society is petitioning them to do so.

Our petition will initially be examined by the Public Petitions Committee, who are greatly influenced by the number of signatures, as well as by the content, and intellectual weight, of individual comments. They can close (i.e. kill) the petition, or write to interested parties, including the Scottish Government, and then forward it to the Education and Skills Committee. This latter Committee, on which we know we have support, can then require the Scottish Government to state and explain its policy.

This theocratic anachronism that has survived only because unexamined. Given the choice, we are sure that the present Scottish Government (any Government) would rather let sleeping dogs lie. Help us to deny them that choice.

Want to do more to help? Sign (obviously); showing professional titles and degrees will add weight, as will indicating if you have a special interest (e.g. parent, pupil, teacher, Minister).

Publicise on your social networks, using #ElectNotSelect, and sharing the petition link (here) and, if you like, the link to this blog post (here).

Write to your constituency and region MSPs. Keep it brief. The very fact of your writing is more important than the details of what is in your letter. Mention the petition by name and number, and the issue of democracy. Mention also any reason you may have for personal interest in the matter.

But keep to the constitutional aspects. Attacks on religion in general, or broadening the discussion to include its role in the educational system, gives ammunition to our opponents. And we will have opponents; no one gives up power without a struggle.

You can also send a comment to the Committee. Keep it brief, and we would ask you to stick to the issues of democracy and equality; see preceding paragraph. If you belong to any relevant professional organisations (e.g. teachers’ unions, parent-teacher councils), write to them as well.

When? As soon as possible. The more immediate support we can show, the more organisations will be willing to support us.

Notes: We will be accused of attempting to drive the Churches out of public life. On the contrary, our petition, explicitly, would leave Local Authorities free to consult or co-opt church representatives, much as they can and do co-opt representatives of parents and teachers, if they choose to do so.


St Mary’s Edinburgh, seat of the Archbishop of Edinburgh and St Andrews. Photo Michael T R B Turnbull via Wikipedia

The Church appointees are non-party, but they are not non-partisan. Nor are they independent, since they owe their positions to their hierarchies.

The Churches have claimed that the system somehow broadens and strengthens the local roots of democracy. In reality, most Church appointments are made by remote hierarchies, with the Archbishop of Edinburgh and St Andrews making appointments from Highland to Dumfries and Galloway.

Scotland, we are often told, is a Christian country. To the extent that this is true, special representation of religion is unnecessary, because Christians vote, and are free to stand for election, just like everybody else.

The Scottish Secular Society is a faith-neutral body, and one of our Board members sits on Scotland’s Inter-Faith Council.

*Scottish Social Attitudes Survey 2014, Tabel 2.4, downloadable here, shows 68 percent of 18-24 -year-olds and 56 percent of 25-39 -year-olds describing themselves as “no religion”

You don’t really know your mind, or do you?

Reblogged from Plato’s footnote; a partial corrective to my own pessimism.

I commented, we ignore uncomfortable knowledge about our own minds, but then we ignore a lot of uncmfortable knowledge. But it is possible to be unconsciously influenced by a bias that one rationally reects, which is why orchestras audition beind screens to conceal the gender of the performer.

Footnotes to Plato

Recent psychological research has been interpreted as casting serious doubts on many crucial aspects of the human experience: that we have “free will” (it’s complicated, hence the scare quotes), that we are at the least capable of rational thinking, and even that we are conscious. Indeed, it has become both fashionable and a bit of a cottage industry to “show,” scientific data in hand, that all those facets of mentation simply do not exist, they are illusions, figments of our imagination (though nobody has really provided an account of why on earth we have them, as metabolically costly as the apparatus that makes them possible is). All of this, of course, despite the staggering crisis in the replicability of results from psychology, which ought to make anyone reading anything in that field a bit cautious before agreeing that we are lumbering rationalizing and self-deluded robots.

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Trump boasts of genetic superiority, German blood

I have great genes and all that stuff, which I’m a believer in


All men are created equal – that’s not true. When you connect two race horses, you usually end up with a fast horse. Secretariat doesn’t produce slow horses. I have a certain gene. I’m a gene believer. Do you believe in the gene thing? I mean I do. I have great genes and all that stuff, which I’m a believer in.

I have like a very very high aptitude


Trump shows us where his superiority is located (CNN)

Well I think I was born with a drive for success. I was born with a certain intellect. The fact is you have to be born and be blessed with something up there. God help me by giving me a certain brain. It’s this [tapping his head], it’s not my salesmanship. This – you know what that is? I have an Ivy League education [actually, he hasn’t Correction: he spent his last undergraduate year at Wharton, the business school of the University of Pennslyvania, whis is Ivy League], smart guy. I have like a very very high aptitude.


You know I’m proud to have that German blood, there’s no question about it. Great stuff

I mean, like, I’m a smart person. You’re born a fighter, and I’ve seen a lot of people who want to fight but they can’t. Some people cannot genetically handle pressure.

I always said that winning is somewhat, maybe, innate. Maybe it’s just something you have; you have the winning gene. Frankly it would be wonderful if you could develop it, but I’m not so sure you can. You know I’m proud to have that German blood, there’s no question about it. Great stuff.

(What more is there to say?)

US absentee election registration made easy: tell US expat friends

trumpI don’t think this man wants you or your friends to see this: absentee voting in US election is easy now, even for expats. My own absentee ballot just arrived by email. I can return it on line as well. I needed social security number, and address of last US voter registration: details at https://register.avaaz.org/vote/VoterInformation.htm

Spread the word

Atoms Old and New, 2: From Newton to Einstein

Part 1 of this series, “Atoms Old and New: Atoms in Antiquity” can be read here.

The transition to modern thinking

“It seems probable to me, that God in the beginning formed matter in solid, massy, hard, impenetrable, movable particles… even so very hard, as never to wear or break in pieces; no ordinary power being able to divide what God Himself made one in the first creation.” So wrote Sir Isaac Newton in his 1704 work, Opticks. Apart from the reference to God, there is nothing here that Democritus would have disagreed with. There is, however, very little that the present-day scientist would fully accept. In this and later posts, I discuss how atoms reemerged as fundamental particles, only to be exposed, in their turn, as less than fundamental.

The scientific revolution and the revival of corpuscular theory – 1543–1687

DeRevolutionibusIn 1543, on his death-bed, Nicholas Copernicus received a copy of the first edition of his book, On the Revolutions of the Heavenly Bodies, in which he argued that the Sun, not the Earth, was thecentre of what we now call the Solar System. In 1687, Isaac Newton published his Mathematical Principles of Natural Philosophy, commonly known as the “Principia”. With hindsight, we can identify the period between these events as a watershed in the way that educated people in the West thought about the world, and number the political revolutions in America and France, and the economic revolutions in agriculture and industry, among its consequences.

Before this scientific revolution, European thinking about nature still followed that of Aristotle. The Earth lay at the centre of the Universe. Objects on Earth moved according to their nature; light bodies, for instance, containe, air or fire in their makeup, and these had a natural tendency to rise. Earth was corrupt and changeable, while the heavens were perfect and immutable, and the heavenly bodies rode around the centre on spheres within spheres because the sphere was the most perfect shape. By its end, Earth was one of several planets moving round the Sun in elliptical orbits, the movements of objects were the result of forces acting on them, the laws of Nature were the same in the heavens as they were on Earth, and all objects tended to move in straight lines unless some force deflected them from this path. The Universe ran, quite literally, like clockwork. This mechanical world-view was to last in its essentials until the early 20th century, and still remains, for better or worse, what many non-scientists think of as the “scientific” viewpoint.

Galileo_manuscriptLeft: manuscript where Galileo records his observations of the motion of the moons of Jupiter, dethroning Earth from its special position as centre of celestial motion. Below right, Gallileo demonstrates the telescope to the Doge of Venice, fresco by Bertini. Click to enlarge

Bertini_fresco_of_Galileo_Galilei_and_Doge_of_VeniceIn 1611, Galileo turned the newly-invented telescope on the heavens, discovered sunspots, and moons round Jupiter, and realised that the belief in a perfect and unchanging1 celestial realm was no longer sustainable. Earlier, he had studied the motion of falling bodies. In work that he started in 1666, Newton showed how the laws of falling bodies on Earth, and the movement of heavenly bodies in a Copernican solar system, could be combined into a single theory. To use present-day language, the Moon is in free fall around the Earth, pulled towards it by the same force of gravity as a falling apple. This force gets weaker as we move away from Earth, according to the famous inverse square law, which says that if we double the distance, the force falls to a quarter of its value. Then with a certain amount of intellectual effort (involving, for example, the invention of calculus), Newton was able to work out, from the acceleration of falling bodies on Earth, and from the Earth-Moon distance, just how long it should take the Moon to go round the Earth, and came up with the right answer. He was also able to work out just how long it would take satellites at different distances to go through one complete orbit. Of course, at that time, Earth only had one satellite (the Moon), but six were known for the Sun (Mercury, Venus, Earth, Mars, Jupiter, Saturn), and his theory correctly predicted how the length of the year of these different planets would vary with their distance from the Sun (the answer is a 2/3 power law; an eight-fold increase in distance gives a fourfold increase in time). Celestial and terrestrial mechanics were united.

It was around this time that a Dutchman, Anthony van Leeuwenhoek, began an extensive series of microscope studies, using single lens instruments of his own devising. Among the first to observe spermatozoa, he also described bacteria, yeast, the anatomy of the flea, and the stem structure of plants. He communicated his results to the Royal Society in London. Formally established around 1660, under the patronage of Charles II, this was and remains

Illus from Arcana after p.356

             Image from Arcana Naturae Detecta, 1695, Leeuwenhoek’s collected letters              to The Royal Society. Click to enlarge

among the most prestigeful of learned societies. Here they caught the attention of Robert Boyle (of Boyle’s Law for gases). Boyle tried to explain such properties of matter as heat, and the pressure of gases, in terms of the mechanics of small particles, or “corpuscles”, and hoped that the other aspects of matter could be explained in the same kind of way. This was, after all, simply an extension downwards of the mechanical system that Newton had so successfully extended upwards. It is instructive to consider how far this hope was fulfilled. Atoms and molecules are in some ways similar in their behavior to small objects obeying the everyday laws of mechanics, but in others they are very different, and it is these differences that must be invoked if we are to understand the forces involved in the chemical bonding.

Early modern theory – 1780-1840

Between 1780 and 1840, chemistry underwent a revolution, that transformed it into the kind of science that we would recognise today. It is no accident that this was the same period as the beginning of the industrial revolution in Europe. Materials were being mined, and iron and steel produced and worked, on a larger scale than ever before. By the end of the period, mineral fertilisers were already in large scale use to feed the growing population. Demand for machinery led to improvements in engineering, and this in turn made possible improvements in the precision of scientific instruments. Much of the new interest in chemistry grew out of mining, mineralogy, and metallurgy, while improvements in manufacture and glass-blowing led to the precision balance, and to new apparatus for handling gases.

Here I will summarise some of the most important discoveries, as seen from our present point of view, and using today’s language. This means running the risk of creating a misleading impression of smoothness and inevitability. Inevitability, perhaps yes; the world really is what it is, and once certain questions had been asked, it was inevitable that we would eventually find the right answers. Smoothness, no; the very concept of atoms, let alone bonding between atoms, remained controversial in some circles way into the 20th century. Outsiders sometimes criticise scientists for taking their theories too seriously, but more often they are reluctant to take them seriously enough.

Overall, mass is conserved; the mass of the products of a reaction is always the same as the mass of the reactants. This is because atoms are not created or destroyed in a chemical reaction.2 Single substances can be elements or compounds, and the enormous number of known compounds can be formed by assembling together the atoms of a much smaller number of different elements. We owe our distinction between elements and compounds to Lavoisier (“The banker who lost his head“). Boyle had come close a hundred years earlier, but was so taken with the transformations of matter that he rejected the notion that its fundamental constituents were immutable.3

The combustion of carbon (its reaction with oxygen) gives a gas, the same gas as is formed when limestone is heated. But there is no chemical process that gives carbon on its own, or oxygen on its own, by reaction between two other substances. So we regard carbon and oxygen as elements, whereas the gas formed by burning carbon (what we now call carbon dioxide) is a compound of these two elements. The production of this same gas, together with a solid residue, by the heating of limestone, shows that limestone is a compound containing carbon, oxygen, and some other element.4 To us, using today’s knowledge, limestone is calcium carbonate, and decomposes on heating to give carbon dioxide and lime (calcium oxide). In Lavoisier’s time, there was no way of breaking down calcium oxide into simpler substances, so he considered it to be an element.

A short philosophical digression (and every scientist has a working philosophy, whether they realise it or not): Lavoisier could make as much progress as he did because he had introduced an operational definition of an element, referring not to some inner essence but to observationally defined properties. And implicit in this was the principle of fallibilism; conclusions are always in principle revisable in the light of further observation, as the example of calcium oxide shows.

Air is a mixture, and burning means reacting with one of its components, which we call oxygen. Metals in general become heavier when they burn in air. This is because they are removing oxygen from the air, and the weight (more strictly speaking, the mass) of the compound formed is equal to that of the original metal plus the weight of oxygen. (Mass is an amount of matter; weight is the force of gravity acting on that matter. Atoms are weightless when moving freely in outer space, but not massless.)

Different elements combine with different amounts of oxygen; these relative amounts are a matter of experiment. In modern language, when some typical metals (magnesium, aluminium, titanium, none of which were known when Lavoisier was developing his system) react with oxygen, they form oxides with the formulas MgO, Al2O3, TiO2.

About one fifth of the air is oxygen, and if we burn anything in a restricted supply of air, the fire will go out when the oxygen has been used up. Nothing can burn in (or stay alive by breathing) the remaining air. Some materials, like wood and coal, appear to lose weight when they burn, but this is because they are in large measure converted to carbon dioxide and water vapour, which are gases, and we need to take the weight of these gases into account.

It was also shown during this period that the relative amounts of each element in a compound are fixed (Law of Definite Proportions). For instance, water always contains 8 grams of oxygen for each gram of hydrogen. Moreover, when the same elements form more than one different compound, there is always a simple relationship between the amounts in these different compounds (Law of Multiple Proportions). Thus hydrogen peroxide, also a compound of hydrogen and oxygen, contains 16 grams of oxygen for each gram of hydrogen. Similarly, the gas (carbon dioxide to us) formed by burning carbon in an ample supply of oxygen contains carbon and oxygen in the weight ratio 3:8, but when the supply of oxygen is restricted, another gas (carbon monoxide) is formed, in which the ratio is 3:4. Carbon monoxide is intermediate in composition between between carbon and carbon dioxide, but it is not intermediate in its properties. For a start, it is very poisonous; it sticks to the oxygen-carrying molecules in the blood even more strongly than oxygen itself, thus putting them out of action. It is formed when any carbon-containing fuel, not just carbon itself, burns in an inadequate supply of air, That is why car exhaust fumes are poisonous, and why it is so important to make sure that gas-burning appliances are properly vented. It is also one of the components of cigarette smoke, which helps explain why cigarettes cause heart disease and reduce fitness.

JdsymbolsLeft: Dalton’s table of the elements, with relative weights, based on H = 1. The correct value for oxygen is 16. Dalton’s value is based on an assumed formula HO for water, together with experimental error; likewise for other elements

All these facts can be explained if the elements are combined in molecules that are made out of atoms, the atoms of each element all have the same mass,5 and each compound has a constant composition in terms of its elements. For instance, each molecule of water contains two atoms of hydrogen and one of oxygen (hence the formula H2O); hydrogen peroxide is H2O2; carbon dioxide is CO2; carbon monoxide is CO; and the masses of atoms of hydrogen, oxygen, and carbon are in the ratio 1:16:12. Using these same ratios, we can also explain the relative amounts of the elements in more complicated molecules, such as those present in octane (a component of gasoline), C8H18, and sucrose (table sugar), C12H22O11. Why C8H18 and not C4H9, which would have the same atomic ratio? This can be inferred from the density of the vapour, using Avogadro’s hypothesis (see below).

Thus, by the early 19th century, chemists were in the process of developing consistent sets of relative atomic weights (sometimes known as relative molar masses). However, there was more than one way of doing this. For instance, John Dalton, the first to explain chemical reactions in terms of atoms, thought that water was HO and that the relative weight of hydrogen to oxygen was one to eight. This uncertainty even led some of the most perceptive to question whether atoms were real objects, or merely book-keeping devices to describe the rules of chemical combination.

Evidence from the behavior of gases (to around 1860)

A French chemist, Joseph Gay-Lussac, noticed that the volumes of combining gases and of their gaseous products, were in simple ratios to each other. In 1811, the Italian Count Amadeo Avogadro explained this by a daring hypothesis, that under the same conditions of temperature and pressure equal volumes of gases contain equal numbers of molecules. We now know this to be (very nearly) true, except at high pressures or low temperatures.

Avogadro’s Hypothesis, as we still call it, gives us a way of directly comparing the relative weights of different molecules, and of inferring the relative weights of different atoms. For example, if we compare the weights of a litre of oxygen and a litre of hydrogen at the same temperature and pressure, we find that the oxygen gas weighs sixteen times as much as the hydrogen. (This is not a difficult experiment. All we need to do is to pump the air out of a one litre bulb, weigh it empty, and then re-weigh it full of each of the gases of interest in turn.) But Avogadro tells us that they contain equal number of molecules. It follows that each molecule of oxygen weighs sixteen times as much as each molecule of hydrogen.

One litre of hydrogen will react with one litre of chlorine to give two litres of the gas we call hydrogen chloride. Thus, by Avogadro’s Hypothesis, one molecule of hydrogen will react with one molecule of chlorine to give two molecules of hydrogen chloride. So one molecule of hydrogen chloride contains half a molecule of hydrogen, and half a molecule of chlorine. It follows that the molecules of hydrogen and of chlorine are not fundamental entities, but are capable of being split in two. Making a distinction between atoms and molecules that is obvious to us now but caused great confusion at the time, each molecule of chlorine, must contain (at least) two separate atoms.6 By similar reasoning, since 2 litres of hydrogen react with 1 litre of oxygen to give 2 litres of steam, water must have the familiar formula H2O, and not HO as Dalton had assumed for the sake of simplicity.

Avogadro’s hypothesis was put forward in 1811, but it was not until 1860 or later that his view was generally accepted. Why were chemists so slow to accept his ideas? Probably because they could not fit it into their theories of bonding. We now recognise two main kinds of bonding that hold compounds together – ionic bonding and covalent bonding. Ionic bonding takes place between atoms of very unlike elements, such as sodium and chlorine, and was at least partly understood by the early 19th century, helped by the excellent work of Davy and Faraday in studying the effect of electric currents on dissolved or molten salts. They showed that sodium chloride contained electrically charged particles, and inferred, correctly, that the bonding in sodium chloride involved transfer of electrical charge (we would now say transfer of electrons) from one atom to another. But, as we have seen, Avogadro’s hypothesis implies that many gases, hydrogen and chlorine for instance, each contain two atoms of the same kind per molecule, which raises the question of what holds them together. These are examples of what we now call covalent bonding or electron sharing, a phenomenon not properly understood until the advent of wave mechanics in the 1920s.

Physicists, meanwhile, were developing the kinetic theory of gases, which treats a gas as a collection of molecules flying about at random, bouncing off each other and off the walls of their container. This theory explains the pressure exerted by a gas against the walls of its container in terms of the impact of the gas molecules, and explains temperature as a measure of the disorganised kinetic energy (energy of motion) of the molecules. The theory then considers that this energy is spread out in the most probable (random) way among large numbers of small colliding molecules. It can be shown that molecules of different masses but at the same temperature will then end up on average with the same kinetic energy, and it is this energy that at a fundamental level defines the scale of temperature. This is a statistical theory, where abandoning the attempt to follow any one specific molecule allows us to make predictions about the total assemblage.

The kinetic theory explains the laws (Boyle’s law, Charles’ law) describing how pressure changes with volume and temperature. Avogadro’s hypothesis can also be shown to follow from this treatment. Many other physical properties of gases, such as viscosity (which is what causes air drag) and heat capacity (the amount of heat energy needed to increase temperature), are quantitatively explained by the kinetic theory, and by around 1850 the physicists at least were fully persuaded that molecules and, by implication, atoms, were real material objects.

Structural chemistry, 1870 on

Isomerism.svgKinds of isomer. The nature of optical isomers was established by Pasteur. Simple rotamers, such as the pair shownbottom right in diagram, readily interconvert at room temperature, giving an equilibrium mixture. The other kinds shown generally do not

Chemists were on the whole harder to convince than the physicists, but were finally won over by the existence of isomers, chemical substances whose molecules contain the same number of atoms of each element, but are nonetheless different from each other, with different boiling points and chemical reactivity is. This only made sense if the atoms were joined up to each other in different ways in these different substances. So atoms were real, as were molecules, and the bonding between the atoms in a molecule controlled its properties. This is what we still think today.

Einstein and Lucretius The piece of evidence that finally convinced even the most skeptical scientists came from an unexpected direction, from botany. In 1827, a Scottish botanist called Robert Brown had been looking at some grains of pollen suspended in water under the microscope, and noticed that they were bouncing around, although there was no obvious input of energy to make them do so. This effect, which is shown by any small enough particle, is still known as Brownian motion. Brown thought that the motion arose because the pollen grains were alive, but it was later discovered that dye particles moved around in the same way. The source of the motion remained a mystery until Albert Einstein explained it in 1905. (This was the same year that he developed the theory of Special Relativity, and explained the action of light on matter in terms of photons). Any object floating in water is being hit from all sides by the water molecules. For a large object, the number of hits from different directions will average out, just as if you toss an honest coin a large number of different times the ratio of heads to tails will be very close to one. But if you toss a coin a few times only, there is a reasonable chance that heads (or tails) will predominate. and if you have a small enough particle there is a reasonable chance that it will be hit predominantly from one side rather than the other. Pollen grains are small enough to show this effect. But this is only possible if the molecules are real objects whose numbers can fluctuate; if they were just a book-keeping device for a truly continuous Universe, the effects in different directions would always exactly cancel out. And if molecules are real, then so are atoms. It is just as Lucretius said, looking at dust in the air two thousand years earlier:

So think about the particles that can be seen moving to and fro in a sunbeam, for their disordered motions are a sign of underlying invisible movements of matter.

1 In fact (see earlier post), the Arabs had already recognized the variability of the star Algol

2 We cheat. There are, of course, processes (radioactive decay, nuclear fusion) where the number of atoms of each kind is not conserved because one element is transformed into another. We simply decide to call these physical processes, so that our statement remains true by definition. Nonetheless, it is useful, because it is usually pretty obvious whether a process should be called “chemical” or “physical”, on other grounds, such as whether or not it involves the formation of new bonds between atoms.

3 The Architecture of Matter, S. Toulmin and J. Goodfield, Hutchinson, 1962

4 In present-day notation,

C + O2 = CO2 and CaCO3 = CaO + CO2

5 This is not quite true. Most elements are a mixture of atoms of slightly different mass but very similar properties. The relative atomic masses of the elements as they occur in nature are an average of the masses of these chemically identical isotopes

6 So we can write the reactions as H2 + Cl2 = 2HCl and 2H2 + O2 = 2H2O

An earlier version of some of this material appeared in my From Stars to Stalagmites, World Scientific. Leeuwenhoek material via Buffalo Library. Dalton’s table of elements and their symbols via Chemogenesis. Isomers image by Vladsinger via Wikipedia

This post originally appeared on 3 Quarks Daily.

My fellow ex-pat Americans … easy link to register

global_temperature_anomaly-svgYes, I am a US citizen, and right now this is a responsibility that I feel I must take seriously.

One US political party, from its Presidential candiate on down, is dedicated to the denial of global warming and the headlong exploitation of fossil fuels. For me, this issue eclipses all others.

I therefore urge you: if you think that global warming is not a problem, and that fossil fuels should be exploited as fully and as quickly as possible, vote Republican.

If you think otherwse, vote Democrat.

But vote. Here’s the link. The form will take no longer to fill out than it took you to read this: https://secure.avaaz.org/en/globalvote_ph/?aAcyEab

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