Tag: physics

The Genius of Marie Curie: The Woman Who Lit Up the World; Wild Shepherdess with Kate Humble

The Genius of Marie Curie: The Woman Who Lit Up the World is part of a loosely linked series of programmes that each examine the life & work of a pivotal figure in Western history of the last couple of centuries or so with an emphasis on science or invention. We’ve watched the Newton one recently (post) and the Turner one last week (post) and on Monday we watched the one about Marie Curie. And it was interesting, a look at both her life and the work that made her famous. But my enjoyment of it was tainted by the way they chose to frame it.

For the Newton programme the opening segment talked about how he wasn’t just interested in things we’d think of as scientific today, he also worked for several years on alchemical experiments and developed his own theological understanding of Christianity. For the Turner programme the opening segment talked about how he’d lived through the Industrial Revolution and painted works that were of that time – they talked about his painting of the Temeraire being towed by a steam tug to be broken up and how that symbolised so much about the age. So the focus in both is on the achievements of the man in question – intellectual or artistic.

For the Marie Curie programme it started off well enough – the opening segment runs through her achievements (2 Nobel Prizes, a woman who succeeded in a man’s world, someone who refused to conform to societal expectations etc). But then the voiceover said something akin* to “In every great life there’s a pivotal moment and the reaction to that is what comes to define their life”. And this moment that they chose to present as “defining” was the discovery of her relationship with a married man by the press & the resulting scandal. Rather than, say, her Nobel Prizes. Or if you’re after a human interest angle what about her work driving a mobile X-ray unit during the First World War, which they suggested later in the programme was what lead to her death. But no, they’d rather frame it as a woman who had a scandalous love affair (while doing science on the side). Gah.

*We’ve deleted the programme already so I can’t check the exact wording.

I hadn’t even heard of that before, I know of her as “Polish woman who discovered radium, married Pierre Curie, eventually died from radiation related disease” – so I don’t see that relationship as something that’s permeated into the zeitgeist as defining. Gah.

To be completely fair, they did later in the programme make the point themselves that the press & public interest was because she was a woman, and that this was sexist. Einstein had affairs & no-one talked about them instead of his physics, why should it be different for Curie. But that doesn’t let the programme off the hook for centring this scandal, and presenting it as at least as important as her work (if not more so).

Two other irritations before I talk about the interesting bits. Firstly, every time they showed us a photograph they did this jerky pan across & around it which was intensely distracting. And secondly, the soundtrack was very obtrusive and the choice of songs not nearly as funny as they thought it was.

So. Despite my irritation with the programme on a philosophical level and on a technical level it was still interesting. What I knew about Marie Curie before was fairly bare bones & it was nice to get that fleshed out a bit (even despite the above). She was born Maria Skłodowska in Poland and grew up in Warsaw during a period where it was ruled by the Russians. At that time there were supposed to be no schools or universities in Polish, no Polish music or dancing – basically the Russians were trying to wipe out Polish culture. Her mother died when Maria was 12, from tuberculosis. Her father was a teacher of physics & maths, and he taught his children these subjects. Maria and her elder sister Bronisława made plans to move to Paris to study at the Sorbonne. They had to move because the Russian run universities in Warsaw at the time would not admit women, whereas the Sorbonne did. The scheme was that Maria would work as a governess in Poland to earn money to support her sister at university, then once her sister was established Maria would move to France & her sister would support her at the Sorbonne. While working as a governess Maria fell in love with the eldest son of the family (not one of her charges) but his parents wouldn’t agree to the match because she wasn’t a suitable class of person – he was unwilling to go against his parents’ wishes and this rejection sent Maria into a depression.

She had at first given up the dream of studying at the Sorbonne, but she enrolled at the illicit “floating university” in Warsaw and studied chemistry (and other subjects?) there. This was a Polish run, Polish language, university and was forbidden by the Russian rulers – and they would teach any Pole who wanted to learn whether male or female. This rekindled her interest and she went on to join her sister in Paris. She excelled in her studies, graduating first in her class. And then she went to work in the lab of a man named Pierre Curie. Her first studies were on magnets – this was relatively lucrative work, because there were commercial interests that would pay for the development of new alloys to make better magnets for better electrical generators. Over time she & Pierre fell in love, and when the homesick Maria talked about returning to Poland he talked about following her there. However in the end they married & remained in Paris (I can’t remember if the programme said why – wikipedia suggests that Warsaw University wouldn’t have her as a PhD student because she was a woman, whereas she could do research in France).

Marie Curie started to work on radioactive materials not long after the initial serendipitous discovery of the phenomenon by Becquerel. She developed (and with Pierre’s help built) apparatus to measure the radioactive rays coming off a sample, and analysed a large number of different substances which was painstaking & tedious work. One sample, pitchblende (a uranium containing mineral), was more radioactive than anything she’d previous analysed including uranium itself. So she theorised that there must be some new element present – and set out to isolate it. This was a mammoth task, as the element was only present in trace amounts. They had some footage of her stirring a great vat of what I think was pitchblende & nitric acid. Eventually she and Pierre isolated and purified their new element – Radium. So called because it glows.

During this time period the Curies had two children. Marie Curie was more interested in her work than her children and they were mostly brought up by her father-in-law. This caused a rift in the family, although Curie and her eldest daughter reconciled by the time she grew up. Curie & her younger daughter didn’t reconcile until Curie was dying many years later. Both Marie & Pierre Curie suffered increasingly from ill health during this time – the effect of their work with radioactivity. Pierre tragically died – not as a direct result of his ill health, which I hadn’t realised. He was actually run over by a horse & carriage, the implication was that if he’d been in better health he might’ve got out of the way.

Curie’s first Nobel Prize was in 1903 for Physics – originally this had only been intended for Becquerel & Pierre Curie but Pierre complained and insisted that Marie’s name should be on the award too otherwise he wouldn’t accept it (good man!). The second one came in 1911, 5 years after Pierre’s death, in Chemistry. This came at the same sort of time as the scandal of her relationship with a married man broke – and the Nobel committee made noises about how if they’d known she was that sort of woman then they wouldn’t’ve given her the prize. Her displeasure with this broke her out of the depression she’d fallen into after the scandal and the end of the relationship*. (The man in question kind of didn’t quite fight a duel to restore his honour, and came away reputation intact, somehow *eye roll*)

*The programme spent more time on this, but I’m irritated by that so I’ve skipped the details here.

In the First World War Curie read that shortage of X-ray machines meant that the French army was losing soldiers who might’ve been saved – and she designed a mobile X-ray unit and drove one (of several?) herself. She and her elder daughter operated this unit for most of the war. There was still no idea at the time that X-rays or radioactivity were dangerous, so Curie didn’t have any protection from the X-ray machine. The programme later said that this is now thought to’ve lead to the aplastic anaemia that killed her (her body wasn’t radioactive enough for it to’ve been the radium).

After the war Curie continued with her work on radium, founding an institute for investigating the element. She was a respected scientist, attending invite-only conferences with other prominent physicists (like Einstein). And was the only one of them to have two Nobel Prizes in two different disciplines – an achievement that is still unique. Despite all this she still had difficulty securing funds for her research & at one point didn’t even have enough radium for her work to continue. This came to the notice of an American journalist (Marie Mattingly Meloney) who had written articles about her, and who organised a fundraising drive throughout the USA to buy Curie’s Institute a gram of radium. When the money was raised Curie visited the US and toured the country giving many lectures before being presented with the radium by the President in a White House ceremony.

Curie eventually died of aplastic anaemia, caused by exposure to radiation or X-rays, and was buried with her husband. In 1995 their bodies were exhumed (hence knowing how radioactive she was) and re-buried with a full state funeral in the Panthéon in Paris – she’s the first (and only) woman to be buried there because of her own achievements.

So, an interesting but flawed programme. But I did at least learn more about Marie Curie and her work.

Wild Shepherdess with Kate Humble is a new series about sheep farming. The hook for it is that Humble owns and lives on a sheep farm in Wales, and for this series she’s visiting sheep farmers in other countries. I think the three episodes will also roughly speaking cover past, present & future (the intro segment hinted at that) but I won’t know that for sure till I’ve seen them all!

This first episode was set in a very remote village in Afghanistan where they still farm in traditional ways dating back thousands of years. The people Humble visited live in the Wakhan Corridor which is part of Afghanistan due to European colonialism. To the north of this narrow strip of land is Tajikistan, once part of the Russian Empire, to the south Pakistan, once part of the British Empire. The Russians and British didn’t want their Empires to meet, so the borders are drawn so that a finger projects from the east of Afghanistan to separate the two countries. The programme opened with Humble travelling through Kabul (the most dangerous part of the whole trip) because this was the only place they could fly to the Wakhan Corridor from. After flying for 250 miles across the mountains they landed in the valley where the Wakhi people live in winter. During the summer months (Humble arrived towards the end of summer) half the population live here, and grow wheat & barley. The other half travel over the nearby mountains to a plateau called the Great Pamir where they graze their flocks of sheep.

After walking to the plateau, with the help of some locals & their yaks to transport their gear, Humble & her camera crew stayed in a couple of different villages to see how these shepherds live. In the first one they were made welcome immediately & encouraged to film whatever they wanted. Here Humble saw the everyday life of the shepherds – a routine of driving the sheep out to graze, bringing them back to be milked in the middle of the day and then at night to protect them from predators. The grazing here is better than in the home valley, and there’s not the space to both grow crops and graze sheep, so the increased risk of predators is worth it. Humble pointed out how the sheep didn’t look like her sheep in Wales – they have much bigger bottoms where they store fat for the winter ahead. They’re also tamer as they’re milked every day, unlike Humble’s sheep which are grown for meat and so not handled by people often. She also seemed envious of their good health, despite the harsh conditions – there are diseases sheep get in the damp climate of Britain that they don’t get in places like Afghanistan which are drier & more like where sheep evolved.

After a bit of time in this first village Humble moved on to another village, because she wanted to film the migrations that these people do as winter starts drawing in – they move progressively down the valley away from the winter. The first village was already quite low (relatively, a mere 4000 feet above sea level …), so they had to go elsewhere to film. This second village weren’t so keen to have foreigners come in & film, and negotiations were protracted. At first a faction among the men were refusing any access, but the women encouraged Humble to sneak a camera in & film them cooking food. The next day the overall chief turned up from the other half of their village (the wheat growing half) to supervise the impending move & he was happy for them to film & quashed the refusals.

Through the whole of the programme Humble showed us how these people lived, and how hard their life is. She talked in particular to one woman who listed the people in her family who had died – two brothers, two sister, her husband, and of her seven children only one was still alive. An appalling list of grief. Their diet is very basic, and mostly the stuff they produce themselves – bread and (buttery) tea for everyday. A sort of flour & butter porridge for more special occasions. And every once in a while they’ll eat meat – one sheep will be spread around the whole village (50 people or so in the second village). A lot of babies die – 1 in 5 before they’re one year old. Half of all the under-twos are malnourished. For the little that they don’t produce themselves they need to buy – and the only way they have of earning money is to sell off a yak. Humble filmed some traders who’d walked up the the Great Pamir to buy yaks, they said they came to the area because they would get good animals and a cheaper price than anywhere else. But while they were talking about how hard this subsistence farming is they were also talking about how they’re glad they’re not closer civilisation and to the war.

I like Kate Humble’s programmes – we saw the ones she did about the Frankincense Trail and the Spice Trail a few years ago. She’s got a knack of not ever making it seem like “look at these funny foreign people”. In fact in this one the sympathies of the narrative (so’s to speak) were clearly with the Wakhi people as they were vastly entertained by how this grown woman didn’t know how to do any of the basic necessities of life. One woman was consumed with laughter as Humble tried to milk a sheep – “what’s she doing? she’s just tickling it!”. Another got Humble to help her churn butter and then could barely believe how she wasn’t strong enough to really help out.

< Previous Episode | Next Episode >

In Our Time: Absolute Zero

Absolute zero, or 0°K is the minimum possible temperature, and there has been a race of sorts over the last couple of centuries to reach that temperature in the laboratory. The experts discussing it on In Our Time were Simon Schaffer (University of Cambridge), Stephen Blundell (University of Oxford) and Nicola Wilkin (University of Birmingham).

The programme started with the Greeks (as a sort of in-joke I think) and mentioned their idea of cold as being radiated in the same way heat is. And then we fast-forwarded through a couple of millennia to the 17th Century when Boyle (amongst others) was speculating about the existence of a supremely cold body which was in effect the essence of cold. And in the 18th Century a French man (Guillaume Amontons) was measuring temperature by means of an air thermometer. He saw this as the effects of heat on the “springiness” of air which increased as the temperature went up. So he postulated that at some low temperature there would be no springiness left in the air and so this must be the lowest possible temperature. In the 19th Century this was taken further, by Kelvin, who used thermodynamics to calculate the lowest possible temperature and set this as the zero point on his temperature scale which is still used by physicists today. 0°K is -273°C, and Bragg unfortunately kept misspeaking through the programme and saying “-273°K” when he meant absolute zero.

By the end of the 19th Century (i.e. before quantum mechanics was thought of) there was a theoretical consensus that temperature could be measured by the energy of atoms of the substance. As the temperature increases the atoms move around more, as it decreases the atoms move around less. Absolute zero is the point where the atoms and their electrons etc. have stopped moving, everything is fixed in place.

And so practical physicists started to try and reach this temperature. The first experiments were done by Faraday, who used pressure to liquify chlorine. The principle behind this is the same was why tea made up a mountain doesn’t really work – as the pressure lowers (because you’re up high) then the water for the tea boils at a lower temperature and so boiling water is no longer hot enough to make tea properly. So in these experiments Faraday increased the pressure that the chlorine was under until the boiling point of it was above room temperature, so the chlorine liquefied. They didn’t spell out the next bit, so I’m guessing here – but I think it’s that once you return the pressure to “normal” then you end up with very cold chlorine liquid (-30°C). He liquefied several gases, but regarded the noble gases as being “impossible” to liquefy, this became the next goal for physicists interested in absolute zero.

At this point in England (which was at the forefront of such research) there were two main players, James Dewar and William Ramsay. Both Scots working in London, and they loathed each other. Which was a shame, as that meant they didn’t work together instead trying put the other one down or prevent him from getting hold of reagents for experiments. Both were interested in liquefying the gases thought to be impossible – as a side-effect of building his research equipment Dewar invented the thermos flask, and Ramsay discovered (and liquefied some of) the noble gases. Ramsay had control of the country’s supply of Helium, which was one of the newly discovered gases (first seen in the sun before being discovered on Earth, hence the name), and prevented Dewar from getting enough to be able to try liquefying it. So instead this was left to a German scientist called Heike Kamerlingh Onnes to achieve. Helium liquefies at about 4°K so we’re down to pretty close to absolute zero here.

Onnes also started to investigate the properties of materials at these low temperatures. In particular he looked at electrical resistance in mercury as you lowered the temperature – one major theory had been that as you reduced the temperature then the electrons would slow down, so resistance would increase. However Onnes found the exact opposite – mercury at the temperature of liquid helium had no measurable resistance at all. He set up an experiment with a loop of mercury at this low temperature and introduced a current to it, after a year the current was still flowing just the same as it had been to start with.

This superconductivity was the first quantum mechanical property to be seen at a macro scale – normally you don’t see quantum mechanical effects at this scale because the jittering around of the atoms disguises and disrupts it. Superfluids are the other property seen at these low temperatures – this is where a liquid has no viscosity.

One other effect of quantum mechanics on the story of absolute zero is that it has changed the understanding of what it actually is – the 19th Century understanding was that everything had stopped moving, there was no energy. However this cannot be the case because the Heisenberg Uncertainty Principle states that you can either know where a particle is or how it’s moving but not both. And if everything has stopped moving then you’d know both, so this can’t be the case. So now there is a concept of “zero point energy” for the energy that remains at absolute zero.

Modern physicists are still trying to reach as close to absolute zero as possible, but it is now thought to be a limit in the mathematical sense – they can tend towards it but not reach it. Part of the reason for this is Zeno’s Paradox – any cooling method cools a body by a fraction, say half. So you can halve the temperature, and halve it again, and halve it again and so on, but if you do that then you never reach your goal. But they’ve got within a billionth of a degree.

This has all been very blue skies – science for the sake of curiosity alone. But along the way there have been inventions and engineering solutions that have had significant practical applications. I mentioned the thermos flask above, but the much more significant invention is the fridge which relies on principles and apparatus designed in this quest for absolute zero and now underpins modern civilisation (think of a world where we couldn’t freeze or refrigerate our food).

And right at the end Bragg flung in a “rabbit out of the hat” question, as he called it. A group of German scientists have managed to get a substance to below absolute zero. Wilkins answered this with one of those physics explanations that makes it all seem like black magic to me – whilst it has a negative temperature in one sense it will be hotter than absolute zero in another sense. And even tho that temperature was reached it won’t’ve been reached by going via absolute zero. She didn’t have a chance to expand before they were out of time, but I rather suspect it would require both high level mathematics & a strong grasp of quantum mechanics to understand!

Wonders of Life; Brazil with Michael Palin

Well, Brian Cox’s Wonders of Life series really didn’t start how I expected it to do. I suppose in retrospect it should’ve been obvious that a physicist would talk about the physics & chemistry of life rather than the biology! This first episode was asking the question “What is life?”. He made a brief detour to mention that this question is typically answered by reference to a soul or other supernatural cause, but then started to talk about the laws of physics and how life exists as a result of the ways these laws work (in the same way that a star exists because of how the laws of physics work).

Life probably got started in hydrothermic vents in the ocean – which are alkaline environments. The ocean of the time (3.5 or 4 billion years ago, or so) was slightly acidic, so there was a proton gradient set up between the alkaline waters of the vent & the acidic waters around about it. The protons moving along this gradient releases energy. This is the same mechanism by which batteries work – in this case the heat of the earth’s core drives the setting up of the gradient, and because of the first law of thermodynamics (conservation of energy) all of this energy must be released when the protons move down the gradient. The hydrothermic vents are also rich in organic molecules, and the energy drives the chemical reactions between these molecules. And the first life arises from that chemistry. All life uses proton gradients to get its energy – he showed us pictures of mitochondria from a variety of animals, but the same is also true of prokaryotes (which have no mitochondria).

At first glance life violates the second law of thermodynamics – that the universe tends towards disorder. Living things are obviously complex and over the last few billion years they’ve got more rather than less complex. I never quite follow this argument (physics really isn’t my thing) but I think what it boils down to is that whilst an organism is more complex it’s achieved that in a way that disorders its surroundings more than they would otherwise be. So yes living organisms are localised pockets of complexity but the universe as a whole is still more disordered than before.

He then moved on to talk about how come life isn’t still just chemical soup in rocks. And what keeps organisms the same as their parent organisms. The answer is DNA – the instruction set for making an organism. I was much amused by his DNA precipitation experiment – take cheek cells, add detergent, salt and alcohol, and hey presto! you have white strands of precipitated DNA in the alcohol layer in your test tube. That’s pretty much the basis of a lot of molecular biology labwork – only you don’t use fairy liquid or vodka. He then ran through the basic high level structure of DNA and talked about how it codes for proteins. And then proteins are both the building blocks & machinery of cells and organisms. The great thing about DNA as a molecule to store the instructions is how stable it is – he quoted 1 error per billion bases (I think) when duplicating DNA which is a pretty low error rate. And relatively small differences in the instruction set are enough to generate very different organisms – he pointed out we’re only 1% different from chimpanzees, 1.6% different from gorillas etc.

The second episode was all about senses. After a bit of scene setting he talked about paramecium, which are single celled organisms that swim about using wee hairs (cilia) in their cell membrane. When it bumps into something in the water the little hairs reverse direction and it moves away again. It does this using proton gradients – normally there’s a difference between inside & outside the cell, and when the paramecium touches something the membrane deforms & this opens channels in the membrane and the proton gradient equalises. The energy generated by this is used to switch the direction of the cilia and to open more channels (I think) which means the change in direction propagates right round the cell. This is the basis of how all our senses transmit the information back to the brain – this is how nerve cells work.

Cox then spent a bit of time talking about how different animals have different senses (and different dominant senses). Different species therefore sense the world differently to us – our dependence on sight & hearing, and our ranges of sight & hearing, aren’t some objective way of detecting the world. Like all other animals we have the senses that we need for our evolutionary niche. In this bit I was particularly amused by the footage from some experiments on frogs – if a small rectangle is move past a frog in a horizontal orientation it goes nuts trying reach it & eat it. If the same thing is moved past in a vertical orientation, the frog doesn’t even seem to see it. When it looks like a worm, then it’s detected, when it doesn’t look like lunch it’s not worth wasting energy paying attention to.

He then talked about human hearing while sat on a boat near some alligators. The point of the segment was that despite the little bones in our ears looking like they’re designed for the purpose, actually they’re re-purposed gill arches. And part way through this long process of re-purposing the bones are the reptiles, whose jaw bones are also re-purposed gill arches. So the alligators were illustration …I still wouldn’t’ve got that close to them myself!

And obviously he talked about sight. Rhodopsin, a pigment that reacts to light, has been around in organisms for a long time – way back to cyanobacteria which have existed for a couple of billion years. And Cox demonstrated how simple a basic eye actually is – even a “camera eye” like ours (retina which does basic light detection, some sort of case with a hole in in front, then a lens in the hole. Obviously the devil is in the details, but one thing Cox didn’t mention explicitly is that eyes are believed to have independently evolved several times (the figure I remember is at least 40 times, but I don’t know if that’s right). He then went diving to see an octopus in its natural environment – which is another animal with a camera eye like ours (and it evolved independently). Octopuses are pretty intelligent, and Cox speculates that perhaps intelligence is driven by the need to process the complex images that our sophisticated eyes produce. I’m not sure what I think of that, in the same programme Cox also showed us a mantis shrimp that sees more colours and detects distance more precisely than people – but there was no talk about them being particularly intelligent.

As I said, not quite what I expected from the name of this series, but that makes it more interesting I think 🙂

< Previous Episode | Next Episode >

We also started watching a series about Brazil with Michael Palin. I tend to be a bit wary of travelogues like this – sometimes the bits where the presenter joins in can cross the line between funny & cringe-making for me. Palin normally stays about on the right side of the line, but only just. But it’s still interesting to see the places & people.

The first episode was about the north-east of the country & was titled “Out of Africa”. A lot of people in this region have African ancestry – a lot of the slaves brought from Africa to the Americas ended up in Brazil. Palin quoted a statistic of 40%, and said this was more than ended up in the USA, which I was startled by. This has noticeable influences on the art & culture of the region – one notable example is the religion of Candomble which mixes African and Christian elements.

Palin visited a few different places in the region & a variety of different sorts of groups & events. The ones that particularly stick in my mind were the cowboys who were participating a race to catch bulls. And the national park that consists of a region of sand dunes that are blown miles inland to an area with heavy enough rainfall that there are lakes in the middle of the dunes – which looks pretty surreal.

< Previous Episode | Next Episode >

In Our Time: Crystallography

Crystallography is a technique that uses the diffraction patterns created by passing x-rays through a crystallised substance to determine the structure of the substance. It was first described in 1912 & has become very important to many scientific disciplines since then. The experts who discussed it on In Our Time were Judith Howard (University of Durham), Chris Hammond (University of Leeds) and Mike Glazer (University of Oxford and University of Warwick).

The programme opened with a brief description of crystallography & its wide-ranging uses in the sciences and then moved on to discuss the history of the technique. X-rays were discovered by chance at the end of the 19th Century, and were given the name “x-ray” because they were unknown rays. One of the questions physicists were trying to answer about these new rays was “are they particles or waves?”. As I understand it the modern physicist’s answer to this would be “yes.” but at the turn of the 20th Century they were still trying to categorise things as one or the other. A German physicist called Laue figured out an experiment to look at this – light waves split and are diffracted if passed through a diffraction grating, but the holes in these are far too wide to do the same at the sorts of wavelengths that x-rays have. So when he learnt about crystals – that they are regular arrangements of atoms or molecules – he realised these might act as diffraction gratings for x-rays. As he was a theoretician he got his students to do the actual experiment (I thought Hammond was quite sarcastic about this as he was telling us about it) – which neatly showed both that x-rays act like light waves when you use a fine enough diffraction grating and that crystals have this regular structure.

The next step on the way to using crystallography to determine the structures of molecules was done by a father & son team called William Henry Bragg & William Lawrence Bragg. Glazer told us a bit about the family – that they came from Wigton, Cumbria (just like Melvyn Bragg, in fact) and William senior moved out to Australia where he met his wife & had children (including William Lawrence). The family moved back to England, where William senior became a professor of physics at Leeds University & Lawrence became a student at Cambridge University. And they both worked on x-rays & x-ray diffraction through crystals. It was Lawrence who figured out the formula (Bragg’s Law) that describes the way that x-rays pass through the crystal structure & how the interactions between the different wavelengths and the differing spaces between the parallel planes of atoms produce a particular configuration of spots on the photographic plate. This formula is now used to work out the structure of a molecule from knowing the wavelengths of X-rays that are put in, and analysing the diffraction patterns that come out.

William senior in parallel was developing the X-ray spectrometer which provides a quantitative measure of the diffraction patterns. The original set up for these experiments was to shine a beam of X-rays through a crystal onto a photographic plate, and then look at the intensities of the spots to work out what structure would’ve generated that pattern. And for simple structures this works out OK, but as it gets more complicated you have a much more complex pattern where differing dots of differing densities might be hard to tell apart. So William developed a technique & machine that shone different wavelengths of x-rays through the crystal at a variety of angles sequentially rather than simultaneously, and then passed the diffracted beam into an ionising chamber to measure the intensity. This was initially a slow & laborious process, but essentially the same principle is used in today’s crystallography experiments – just the advent of computers & more refined technology has made the whole process much easier.

The first structures solved were simple ones – the very first was that of salt, NaCl. People then moved on to slightly more complex molecules (such as the benzene ring). And from there to much more complicated things, like proteins which consist of hundreds of thousands of atoms. The first of these to be published was the structure of haemoglobin, which was solved by Max Perutz – I think I once went to a lecture given by Perutz (but about 20 years ago so I can’t really remember it). The most famous is the structure of DNA, the discovery of which was published by Watson & Crick but relied heavily on data from Rosalind Franklin (which she wasn’t aware had been given to the other two, and she wasn’t credited for her work at the time).

During the programme the conversation went off on some interesting tangents. The first of these was that there is a relatively large number of women working in crystallography at all levels, and has been since the early days of the science. Howard said that this was down to both the newness of the field (relatively speaking) and the attitudes of the initial founders. Both Braggs welcomed anyone who could do the work into their groups, and didn’t discriminate based on gender, and there weren’t previous entrenched attitudes about the “place of women” in the field to overcome.

They also briefly discussed the way that modern science funding would’ve stifled some of the pioneering work in the field. I shan’t get up on my soapbox here, but it’s something I’m in agreement with. The examples from this discussion include the discovery of both x-rays themselves, and the technique of crystallography, which revolutionised several scientific fields and wouldn’t’ve happened if the scientists had had to figure out in advance why it was worth spending the money on that research. And some of the initial work solving structures was incredibly long term by modern standards – it took Perutz 25 years to be able to publish the structure of haemoglobin, no direct pay off in a 3 year project that’s easy to point to when you’re writing a grant application. You need some blue skies research and long term projects, as well as the more directed and more obviously relevant stuff – that’s how you expand the boundaries of knowledge & find out truly new things.

And they discussed how crystallography is a multi-disciplinary field – and that’s one of it’s strengths. People come from different scientific backgrounds, and collaborate across the boundaries of these fields.