An Easter Friday Reminder of the Shroud of Turin

In 1960 Willard Frank Libby was awarded the Nobel Prize for his method of using carbon-14 to find the age of objects ranging from ancient bows and arrows to trees buried in glacial ice. Since then, the technique of radiocarbon dating has been improved so that it can be used with much smaller samples—fractions of milligrams instead of the original 8 grams. This has made it less intrusive when dealing with precious art and in trying to figure out the authenticity of artefacts like the Shroud of Turin. Whereas, Libby modestly assumed that radiocarbon dating’s upper limit was 20 000 years old, it can currently estimate the age of objects as old as 55000 years old.

Carbon has 15 isotopes, of which only 3 are natural: 12C, 13C, 14C. The superscript refers to the sum of neutrons and protons in each atom. Any atom is characterized by its number of protons, so the trio of carbon’s isotopes 12C, 13C, 14C, have 6 protons each, but they contain 6, 7 and 8 neutrons, respectively. That last number seems to be too much for a nucleus to handle. Every 5730 ± 40 years, in half of 14C nuclei, a neutron transforms into a proton, an antielectron neutrino and a beta particle, becoming 14N in the process, the common isotope of nitrogen in the air. A beta particle is a highly energetic electron and is a form of radiation identical to what old “cathode ray” television sets and computer screens emitted from their long bulky bodies; it was blocked by lead (Pb) in the glass screen. The reason some 14C exists on earth is that neutrons released from violent cosmic ray-collisions in the Earth’s upper atmosphere cause a small portion of 14N in the air to become hydrogen and 14C.

This property of 14C has been very useful in dating old samples of bones, charcoal, seeds, wall paintings and in just about anything containing carbon.  While plants are still alive, through photosynthesis, they continuously absorb 14C from the small fraction of carbon dioxide which contains the isotope. This was first realized by Libby. Whether carbon dioxide contains 14C or the common 12C doesn’t affect the chemical properties of the vital gas. So plants can still use it to make glucose.

After organisms die, after bacterial decomposition, whatever 12C that remains behind does not undergo radioactive decay. Unlike 14C, 12C is a stable isotope. But 14C keeps transforming back into 14N. So the longer something has been dead, the less 14C it contains. The most efficient carbon-dating technique is accelerator mass spectrometry (AMS).

The 14C content is directly measured relative to the amount of 12C and to 13C present, which, like 12C, is also stable. From these ratios, the age of an object can be calculated. Unlike other methods, AMS does not measure the amount radiation emitted but determines the number of carbon atoms present in the sample and the age-dependent ratios. The 55000-year upper limit of radiocarbon-dating has only been reached in the past 15 years. As recently as 2008, the limit was a little less than half of that because sunspot activity affects the rate of cosmic rays reaching the earth, and hence the amount of 14C-formation in the atmosphere has not been constant. A calibration curve based on tree rings and their analyses takes the fluctuations into account. The improvement of the curve and the use of the AMS technique have been mainly responsible for giving the method more historical scope.

The Shroud of Turin is a  linen  cloth that Christian tradition associates with the crucifixion and burial of Jesus .   In 1988, scientists at three separate laboratories used carbon-14  to date samples from the Shroud to be from 1260 to1390 AD, coinciding with the first verified appearance of the shroud in the 1350s. Given that the burial of Jesus was in 30 or 33 AD, the evidence strongly suggests that the Shroud is not the real McCoy. 

35 years later, the 1988 tests continue to be debated. Is it because the conclusion clashed with longstanding belief about the cloth? About 10 years ago, Professor Christopher Ramsey of the Oxford Radiocarbon Accelerator Unit, one of three labs which carried out the research, said, “We’re pretty confident in the radiocarbon dates. There are various hypotheses as to why the dates might not be correct, but none of them stack up.” More recently, in 2019, Phillip Ball, former chief editor of Nature, wrote, “Nothing published so far on the shroud, including this paper, offers compelling reason to think that the 1989 study was substantially wrong – but apparently it was not definitive either.” Given ever-improving techniques and rigorous statistical analyses, the bar can always be raised.  But so far, more radiocarbon testing has not been given the OK by the Church. As Ball said, “As it stands, reticence looks more like fear of what further studies might reveal.”

Sources:   2021

Nobel Prize Winners in Chemistry. Eduard Farber. Abelard-Schuman. 1962


Defying Stereotypes: Sir Humphry Davy

If a biographer of Humphry Davy wanted to reinforce the scientist-stereotype, he would emphasize how a young Davy was turned on to chemistry by reading Lavoisier’s book and how he was discharged from an apothecary for causing explosive reactions. He would mention his bad habit of inhaling gases, which probably helped shorten his life to 51 years.  Most importantly the biographer would highlight Davy’s discovery of seven chemical elements, more than anyone in history except for the discoverers of synthetic nuclear elements, which I find less exciting.


Davy’s early electrolysis equipment Credit: J & J Marshall

And the details of Davy’s discoveries are indeed stimulating for aficionados of chemistry. He first attempted to obtain elements by decomposing saturated alkali solutions. It’s easy for us to understand why such an attempt was in vain. But the concept of ions was almost a century away, so he could not have possibly foreseen that water  generates hydrogen ions, which attract electrons better than any alkali ion. Yet he was clever enough to then try it without water, to use the solid salts themselves, exposing them to air just enough to make their surface conduct.  Instead of failing like others who had heated the solids as if they were akin to oxides of mercury, Davy applied a battery’s current to potash. And it worked! Even when he switched the wires around,  he would always observe effervescence at the positive pole. and at the opposite pole, pearls of metal briefly appeared. Then some globules tarnished while others exploded in the air.  If water was added to the metal, the result would be just as dramatic:  he would get hydrogen gas, which in the presence of potassium, burnt with a lovely lavender light.

Of course there are other positive characteristics associated with the scientist-stereotype. The biographer would have to not only outline his discoveries but discuss how Davy  considered the possibility that he was wrong, just in case his substances weren’t new elements. Indeed Davy did switch his platinum electrode with other materials to check if the material itself was involved in the reaction. But copper, gold, silver and lead alloys all yielded the same result. When others like Gay Lussac had suspected that the hydrogen was coming out of the potassium, so named because it came from potash, Davy revealed that in the absence of water, no gas could come out of potassium or sodium. He really had discovered new elements. Eight years later, in 1815, Davy saved lives by inventing a miner’s safety lamp. Its gauze’s holes let oxygen in, and when they were of the right size, the metal surface cooled and blocked the spread of the flame, preventing the ignition of explosive methane from deep coal mines.


On the left is Davy’s lamp. On the right is a an earlier prototype that did not work so well. From the Royal Institution’s archives. Photo by Paul Wilkinson.

M0004638 Portrait of Sir Humphry Davy, 1st Baronet, FRS (1778 – 1829),

Humphry Davy from Wikimedia Commons

So what should a biographer add about Davy, so as not to reinforce the common image the public has of scientists: Davy’s enthusiasm for fishing? A mention of his good looks, the reason that some ladies attended his public lectures? The most pronounced atypical characteristic about Davy is that he wrote poetry throughout his life. J. Z. Fullmer writes ,

In his science, he had searched into the hidden and mysterious ways of
nature. In his poetry he had truly worshiped and adored Nature’s
“majesty of visible creations.” He was Philosopher, Sage, and Poet.

In one of his notebooks Davy recorded the following. It’s not verse but certainly prose of a poetic nature:

To-day, for the first time in my life, I have had a distinct sympathy with
nature. I was lying on the top of a rock to leeward; the wind was high, and
everything was in motion; the branches of an oak tree were waving and murmuring to the breeze; yellow clouds, deepened by grey at the base, were rapidly floating over the western hills; the whole sky was in motion; the yellow stream
below was agitated by the breeze; everything was alive, and myself part of the
series of visible impression. I should have felt pain in tearing a leaf from one of
the trees.                                                     Memoirs  Volume 1 p113

If such an experience is the exception, it begs the question, is such a perception of the world among scientists any more rare than it is in the rest of the population? Poetry aside, the thing that scientists have in common is an above average interest and devotion to science. But like any other group, there are more differences within their kind than there are between them and other people.


The discovery of the elements. IX. Three alkali metals: Potassium, sodium, and lithium. Mary Elvira Weeks  J. Chem. Educ., 1932, 9 (6), p 1035.

The Poetry of Sir Humphry Davy. J. Z. Fullmer.  Chymia, Vol. 6 (1960), pp. 102-126
University of California Press.  :

Asimov’s Biographical Encyclopedia of Science and Technology. Second edition Isaac Asimov.


Choices in the Aftermath of Society’s Commitments

I was struck by the following blog entry from an inorganic chemistry enthusiast:

I couldn’t help reading another article on Fritz Haber today. Like every person, he had a personal life and he made choices. All I am interested in is his science, and I admire his science.

It’s a common attitude among students and professionals. Scientists’ biographies are perceived to contain irrelevant details that get in the way of learning science. Particularly, when the details are negative, an enthusiast will likely dismiss them because it conserves mental energy. But is it a responsible attitude?

The 2004 film about Fritz Haber written by Ragussis. The actor portraying Haber in the picture is Christian Berkel. source imdb

The 2004 film about Fritz Haber written by Ragussis. The actor portraying Haber in the picture is Christian Berkel. (source: imdb)

The biographical essay in question, Fritz Haber, the damned scientist, emphasizes not only Haber’s personal life and choices, but it examines his status, social context and the choices that his country and its opposing countries were making before, during and after World War I. We can neither ignore history and contemporary events nor pretend that science is a process independent of all other forces in society. It would be like trying to understand a forest without learning about the geochemistry and climate that partially determine its fate. It is very easy to quickly judge individuals, but their social context cannot go unexamined. In fact, in a previous blog, in comparing different attitudes of the Via Panispernia Boys towards the applications of nuclear science, I was guilty of overfocusing  on scientists’ decisions and not on the commitments of society and the contingencies that lead to new dilemmas for individuals.  Such an approach is counterproductive if we are to learn from the past.

For readers unfamiliar with Fritz Haber, he was a German-Jewish chemist born in 1868 and famous for a number of achievements. He sparked another stage in the “agricultural revolution” by laying the groundwork for the production of ammonia (NH3) from atmospheric nitrogen and hydrogen. He recirculated the reactants,  found the right catalysts and controlled temperature and pressure. With the help of others such as engineer Carl Bosch, a large scale process was then developed, and the NH3 was converted to nitrates, which supplied an essential element to crops. Prior to that, countries were relying heavily on imports of South American guano, which contains uric acid (has nitrogen) as well as phosphates and potassium. Today, it is estimated that more than 50 per cent of the nitrogen atoms in the average human body derive from the Haber-Bosch process.

Some writers have unfairly used the negative consequences of large scale fertilizer-production as more ammunition against Haber’s character. But his contemporaries also had no idea that eutrophication could arise. And few predicted that 40 years later,  the Haber process would combine with other inventions, medical advances and attitudes to produce a sharp growth-spike in population.


from Wikipedia:

The Haber process is yet another tool, which despite good intentions at the onset, becomes more likely to have serious complications in a society devoted far more to blind economic growth than to setting up adaptive cycles.

But why was Haber harshly judged even by his contemporaries? Although the value of his discovery was recognized by the Nobel Committee in 1919, many scientists did not show up for the presentation of the award presumably because of the role that Haber played in developing poison gas in the first World War. The committee officially dubbed it the “1918” prize, but it was actually handed out in 1919, after the armistice. According to W.A.E. Mc Bryde of the University of Waterloo, Haber’s use of chlorine as a weapon was not their focus.

In America a swarm of editorials and letters challenged the suitability of the award to Haber; the point was not the gas warfare, but the extended duration of the war made possible by the manufacture of nitric acid from synthetic ammonia.

If both reasons provided grounds for protesting the award,  those who condemned Haber’s role as “Doctor Death” ignored Grignard’s subsequent use of phosgene (COCl2 ) in the war. Grignard, also a Nobel Prize recipient for chemical synthesis that was unrelated to wartime exploits, was of course working for France. Their soldiers had been the first victims of the chlorine attack. But France had used either xylyl bromide(methylbenzyl bromide) or ethyl bromoacetate as a tear gas before Haber had proposed chlorine as a death agent. Both sides believed that the shocks of chemical warfare would end the war quickly (a cynic would say, to win it promptly). Of course, that did not happen. The perception of Haber as the callous scientist was reinforced by the fact that his wife was ardently opposed to his use of chemical weapons, and after Haber let his plan materialize on the battlefield, she fatally shot herself .

But as in many suicides, there were other factors at play. For instance, she was intellectually frustrated by being a PhD in chemistry but never being able to practice it. Her only contribution to the field involved translating Haber’s work into English. Contemporary women in Germany, regardless of their education-level, were still expected to serve exclusively as housewives. Yet Haber wasn’t callous to her depression. He had tried to get her a university teaching position, but she froze in front of her first class and gave up.

Let’s now examine the resentment towards Haber for making nitrates for ammunition. As Dunikowska and Turko point out, even before the alliances had brought Germany into the war, the government and most of industry had committed themselves to building a war machine, one that was opposed not only by humanists and social democrats but by some business people. Once engaged in militarization, inevitably, any country’s scientific research will be focused on the awful business of death, and scapegoating one individual is mostly an emotional response that won’t later serve as a preventative strategy. While so much hatred towards Haber and fellow Germans persisted after the end of World War I, the unfair Treaty of Versailles was signed. The exaggerated burden placed on the defeated country led to widespread instability, eventually facilitating the Nazis’ rise to power. Their new war machine soon led to an even more pernicious world war.

Haber’s response to the Treaty was to focus only on his country’s gargantuan debt. His simplistic approach was to mine the oceans for gold. Eventually after a costly 8-year project, he realized the concentration of gold in the sea was too low. For his unsuccessful hypothesis, he became vilified by his own country men. Professionally, however, he made important contributions in areas of pure science such as chemiluminescence and the formation of radicals in combustion. Unfortunately, some sloppy journalism has recently claimed that Haber when on to discover Zyklon B (an HCN-based gas used in concentration camps). In fact his institute developed it as a pesticide, and he was not its individual discoverer.

In April of 1933, three months after Hitler came to power, laws were passed, forbidding Jews to occupy government positions. Although still working for the government, Haber, was exempt from the law, despite being born Jewish. He and some of his colleagues were conscientious enough to oppose the law on principle, and later in the summer of that year, he left the country for London. There he continued to be scorned by scientists like Ernest Rutherford. Eventually he settled in Basel, Switzerland, where he soon died of a heart attack.

Haber made wrong ethical choices during the war, there’s little doubt. But he had plenty of company since the probability that anyone in such a position behaved likewise was highly increased when government and industry had already surrendered intellect, spirit, economy and technology to nationalism and militarism. It’s something to bear in mind when analyzing our current society. We have to deconstruct mechanisms that are committed to an illusive growth that that does not factor in social and environmental expenses. At the same time, we have to reinforce policies and strategies that value modesty and stability.