Tag: Bragg, Melvyn

In Our Time: Cosmic Rays

We’re back to listening to episodes of In Our Time on Sunday mornings. The one we listened to this week was about that staple of 1930s science fiction – cosmic rays. The three experts who were talking about the reality of this phenomenon were Carolin Crawford (University of Cambridge), Alan Watson (University of Leeds) and Tim Greenshaw (University of Liverpool).

Cosmic rays were discovered about a century ago. The first indications that they existed came from detection of increasing radiation levels as you go higher up in the Earth’s atmosphere. At first they were assumed to be photons and the name “cosmic rays” was coined. This turns out to be a misnomer, they are in fact charged particles – bits of atoms. Some of them are atomic nuclei, some are electrons and some are more exotic things like positrons. They travel at a variety of speeds, from a variety of sources. Crawford told us that they are categorised into three broad groups. The first of these are relatively slow-moving particles that come from relatively local sources – the sun for instance – and are very common. These are the particles that are involved in creating the Aurora Borealis. The next group are moving more quickly, and come from further away – generally these are thought to be generated as as side-effect of supernova explosions. And the last group are the fastest moving and are thought to be from outside our galaxy, these are the rarest type of particle.

The particles aren’t detected directly (on Earth) instead what we detect is the side-effects of these particles hitting the Earth’s atmosphere. As the particles collide with atoms in the upper atmosphere they generate a shower of secondary particles and it’s these that are detected. The types and numbers of these particles can be used to work out what hit the atmosphere, how fast it was going and the direction it was travelling. We know they are charged particles (and which charge) because of the effects of the Earth’s magnetic field – the number of particles hitting the atmosphere varies with latitude with most of them at the poles. This is also why the Aurora Borealis are mostly at the poles. That phenomenon is formed by the particles exciting the electrons in atmospheric atoms, when the electrons return to their original energy states they emit light. They went off into a slight digression on the programme when talking about this – predicting the Aurora Borealis requires prediction of solar weather and that’s being worked on because particularly bad solar weather can lead to EMPs that can affect satellites.

All three experts agreed that the fastest moving group are the most interesting – in part because we still don’t know much about where they come from or how they’re generated. They’re pretty rare, so a normal sized detector (I don’t think they said how big) would only detect about one a century – so Watson was talking about a project he helped set up that built a detector the size of Luxembourg and this detects 3 or 4 of these rare particles a year. One theory of where they come from is that they are generated in galaxies with super massive black holes at the centre. Another is that they have something to do with dark matter.

Particle physics as a discipline grew out of the study of cosmic rays. The Large Hadron Collider does under controlled conditions what cosmic ray particles do when they hit the atmosphere. This is another reason why the fastest particles are the most interesting – they travel at a much higher speed than the LHC can achieve. The fastest moving particles travel faster than the speed of light in air, generating Cherenkov radiation. Again the programme took a little digression to explain this. Light travels at different speeds in different media – and so these particles aren’t travelling faster than light does in a vacuum (like the space the particle was just travelling through), it’s just that they don’t slow down when they enter the atmosphere. So the radiation that is released in front of the particle is moving slower than the particle and so can’t move away from the particle. It’s effectively being pushed along in front of the particle and that’s what we detect as Cherenkov radiation. It’s a bit like the sonic boom you get when something breaks the speed of sound.

As an aside – something I didn’t know before was that 14C dating is a direct result of cosmic rays. The 14C in the atmosphere is generated by cosmic ray particles hitting nitrogen atoms, if cosmic rays didn’t exist we’d not have such a good way of dating organic material (like bones).

Future work on cosmic rays is quite concentrated around figuring out what the fast ones are. There is also data being gathered more directly on the particles involved. The ISS currently has a cosmic ray detector fitted to the side of it, which has been gathering data since 2011 and is planned to continue for ten years.

In Our Time: The Corn Laws

In 1815 the British government passed a law fixing the price of grain at a higher than market price. This was the first of the Corn Laws, and it sparked rioting by those most affected – the urban poor. The laws were to last until the late 1840s, when they were finally repealed under pressure from manufacturers concerned about the effect on trade. The three experts who talked about these laws on In Our Time were Lawrence Goldman (Oxford University), Boyd Hilton (University of Cambridge) and Cheryl Schonhardt-Bailey (London School of Economics).

They started the programme by giving us a bit of context. Britain in 1815 was at the start of the process of industrialisation and just coming to the end of the Napoleonic Wars. So there was concern about how the economy was going to adjust to the new demands of peace and industry. There was also concern over political instability in Europe, and worries about the spread of revolution to Britain (it’s not that long after the French Revolution after all). And the industrialisation of Britain was also shifting population and the balance of power more towards the growing manufacturing cities of the north, which was generating pressure for reform of Parliament and extension of the franchise.

So against this backdrop the landowners, who were the major interest represented in the Parliament of the time (both in terms of who has the vote and in terms of how many MPs come from which areas of the country) vote through a law that protects their profits from grain growing. During the war it was harder to import grain, so to feed the country more & more marginal land was forced into cultivation. Now that peace has broken out the landowners are worried that grain imports will force down the price of grain and the profits they make & the rents they can get from their tenant farmers will be reduced. The law was openly protectionist in nature and the landowners who passed it felt it was their due for supporting the country during the war.

Right from the start didn’t go as well as they had hoped. Britain wasn’t actually able to be self-sufficient, but the hope was that for the 4 or 5 years out of 6 when the harvest was good enough then British grain would be enough. And for the other 1 or 2 years in this cycle when the harvest failed then grain could be bought in from the Eastern European farmers and prevent famine. But as one might predict (with the benefits of a cursory, but 21st Century, knowledge of economics) without the market always being there the farmers of East Europe turned to other crops or other ways of making their living, rather than growing surplus corn just in case they could sell it to Britain. So further laws were passed trying to sort this situation out whilst still protecting the interests of the British aristocracy.

Into this situation comes the Great Reform Act of 1832. This extended the franchise to men with less property (one now needed land or a house to the value of £10). And the boroughs were redrawn – the system had been kept the same for about 400 years previously, despite changes in population. Previously there were areas (“rotten boroughs”) where there was little population but they had an MP, and places such as Manchester (a new and growing town in this period) had no representation. This reform changed the balance of power, and the industrialists started to campaign against the Corn Laws. From what the experts on the programme were saying this didn’t have much to do with the plight of those poor who couldn’t afford to buy bread. Instead it was about trading the goods that the manufacturers were making. If Britain wasn’t importing grain then it was hard to get other countries to buy Britain’s exports, which hurt the profits of the industrialists and the country’s economy as a whole. And it was about how if food is expensive, then people buy less clothing or other goods, and again less profit for the boss and less economic activity in general.

The Anti-Corn Law League was formed in 1838, and attracted many supporters. They were working towards a plan for repealing the Corn Laws after the planned 1848 election – involving propagandising to the country in general and the electorate in particular, and getting their sympathisers elected. The Anti-Anti Corn Law League (real name the Central Agricultural Protection Society – CAPS) was formed in 1844 to campaign in support of the Corn Laws. Schonhardt-Bailey gave us some figures to demonstrate something of their reach – the Anti-Corn Laws League started off with about £5,000 worth of subscriptions, and grew by 1845 to ~£250,000 worth of subscriptions. The CAPS had about ~£2,000 worth of subscriptions at that point. The CAPS were handicapped in a couple of ways – firstly their senior figures (like the Duke of Richmond) were the sort of people that fit contemporary stereotypes about useless & wasteful aristocrats, whereas the leaders of the Anti-Corn Law League were charismatic and good persuaders. And the CAPS membership and support base was drawn from people who felt it wasn’t appropriate to take politics “out of doors” – i.e. politics was something that happened primarily in Parliament and between the Members of Parliament. So they had an ideological opposition to drumming up support amongst the electorate & the population at large.

Robert Peel, eventually responsible for repeal, properly enters this clash of ideologies in 1841 when he becomes Prime Minister as the leader of the Conservative Party. The programme digressed a bit to talk about Peel’s background here, as he’s the man responsible in the end for driving through repeal. Peel’s father had been a self-made man, who then became a baronet. Peel himself had been educated at Eton & Oxford, so brought up with the members of the elite, and went into politics. He was ideologically a good fit for the Conservative party of the time, but didn’t feel at ease with them – because he wasn’t part of the old aristocracy he was an outsider in some ways. The Conservative Party was generally in favour of the Corn Laws – they represented the old landed interests. Peel himself voted against repeal several times in the early 1840s, although the experts suggested that he’d always been in favour of repealing them. This probably wasn’t for the same sorts of reasons as the industrialists wanted to repeal them. The suggestion is that Peel saw the Corn Laws as protecting the short term interests of the landed aristocracy at the expense of their long term protection. Effectively he was spooked by the rioting and opposition of the general public to these laws, and believed that as long as these laws existed they kept inflamed the possibility of revolt like in France only half a century earlier. You might have hefty bank balances from your grain profits, but will that help you if the mob burn your house down?

The experts were saying that Peel started by introducing legislation to weaken the effects of the Corn Laws – they believed this was an attempt to avoid looking like he was betraying his party. The plan seemed to be to reduce the laws, and then win the 1848 election on the back of these partial repeals which would then give him the mandate to repeal the Corn Laws fully. But this isn’t how it played out, instead in 1846 Peel brought repeal to the table at Parliament, and managed to persuade sufficient of his party to support him to bring it about. The experts were suggesting perhaps he came to believe his party wouldn’t win the planned 1848 election, so wanted to get this done when the Conservatives would reap the political benefits. Apparently the language used around the issue at the time was fairly religious and overblown (with talk of martyrdom and so on), so perhaps Peel was also swept along by a feeling that it would be the right thing to do to politically die for his faith in repeal.

After the Corn Laws were repealed and a Free Trade approach to the economy was now employed. The experts said that the next couple of decades were very prosperous for Britain – with ample harvests, and plenty of growth in the economy. They also said that this didn’t have much to do with the Corn Laws or Free Trade – it was mostly a result of climatic conditions favourable to agriculture. But because of the presumed cause & effect – repeal of the Corn Laws –> prosperous Britain – this shaped the future of Britain. Free Trade was now seen in many circles as proven to lead to a booming economy.

The programme ended quite abruptly, as Bragg realised they were running out of time – one of the problems with this being a live show I guess. I’m surprised it doesn’t happen more often. I’m not surprised it happened to this one, it was one of those subjects I thought might be a bit dull in advance but turned out to be fascinating once it got going.

In Our Time: The Book of Common Prayer

The Book of Common Prayer was written during the English Reformation as the new reference for the services & ceremonies for the new Church of England, and it’s still in use in many churches today. Discussing it on In Our Time were Diarmaid MacCulloch (University of Oxford), Alexandra Walsham (University of Cambridge) and Martin Palmer (Director of the International Consultancy on Religion, Education, and Culture).

Prior to the break with the Roman Catholic Church all church services were in Latin, and the forms of the services came from several different books depending on what sort of service it was and so on. Even though the English Church’s break with Rome was driven by Henry VIII’s desire for a divorce from his first wife there were genuine supporters of the European flavour of Reformation involved in the process. A key figure amongst these was Thomas Cranmer, Archbishop of Canterbury, who not only orchestrated the original split from Rome but was also (in Edward VI’s reign) responsible for the original versions of the Book of Common Prayer. This was designed to be the single book that contained all the necessary prayers and ceremonies for the Church of England – each parish church had a copy, and used it for its services. The first version was to some degree a compromise between those who wanted a fully Reformed Church and those who wanted a more traditional Catholic theology (with or without the Pope as the head of the Church). As such a contemporary of Cranmer’s (who wasn’t as keen on Reformation as Cranmer) demonstrated that it could quite easily be interpreted in line with traditional Catholic theology. The second edition, again written by Cranmer, was published in the closing months of Edward VI’s reign and it was more hardline Protestant. Edward’s death & his sister Mary’s ascension to the throne returned the country to the Catholic Church and so the Book of Common Prayer was sidelined for a while. When Elizabeth I came to the throne she had the Book of Common Prayer republished, in much the same form as the second edition, and it was again the official prescribed version of the services.

By the time Elizabeth died the book which had once been regarded as “too Protestant” was regarded as “too Catholic” for hardline reformers. There was hope that Elizabeth’s successor would bring about a proper Reformation of the English church – after all James VI & I had been brought up in the Scottish Kirk. Sadly for the reformers James rather liked the ceremony of the English Church, and wasn’t fond of the dour Scottish Kirk – and in particular he liked the hierarchical nature of the English Church which reinforced his sense of his divinely anointed authority. So the Book of Common Prayer (and the concept of bishops) lived on. After the Civil Wars, while Oliver Cromwell was Lord Protector the Book of Common Prayer was again abolished – this time replaced with a much more Puritan form of worship. The Restoration of the Monarchy was also the restoration of the Book of Common Prayer – revised another few times subsequently, but the definitive version is the 1662 revision. This was used throughout the British Empire as it grew, and is still used in some churches today.

As well as the history of the Book of Common Prayer they also talked about the language of it in the programme. Obviously it’s in English – and this was one of the important features of the new service book. An important part of the Reformation was the idea that everyone should understand what was going on – both in having access to a bible in their own language and in having services in their own language. The actual phrasing of the book is also important – it has had a significant impact on the sort of language we use today. They were keen to stress on the programme that it was written with its use in mind – in that the same words are to be used time and time again, so the prayers were constructed to be repeatable. Not florid prose that might sound foolish after a while nor witty or full of punchlines that might sound lame the umpteenth time you heard them. For much of the century or so of the reformation process in England there was a requirement to attended Church of England services that used the Book of Common Prayer. This ensured that the words and their underlying theology sunk in, over time, and that all children were properly indoctrinated.

One thing that they mentioned several times in the programme is something that always strikes me when learning about the Reformation in England – how very odd it was compared to the rest of Europe. The English Church tried (and mostly succeeded) in navigating a third way between catholicism and protestantism. A lot of the theology was reformed as compared to the Catholic church (like transubstantiation), and obviously the Pope is no longer head of the C of E. But the C of E still has bishops and a hierarchy, and even though it’s been austere at various times and places it has also still had ceremony and pomp at various times and places. So it didn’t really make either of the extremes happy – and the way the Book of Common Prayer was discarded once for being too Protestant and once for being too Catholic within the space of a century sort of sums that conflict up.

In Our Time: Galen

Galen was a Greek doctor who lived in the 2nd Century AD and wrote an incredible amount about the practice of medicine. His works were still used as the standard medical texts in Europe & the Islamic world until the Renaissance era – and some parts even after that. The experts discussing it on In Our Time were Vivian Nutton (University College London), Helen King (Open University) and Caroline Petit (University of Warwick).

Galen was born in Pergamon, Greece (the city of the Pergamon Altar, now in Berlin) and was the son of an architect. At this time Pergamon was a rich city and was spending a lot of money on civic buildings, so Galen’s family were well off. Galen was bring brought up as an intellectual, but then when he was 17 his father had a dream where the god of medicine appeared to him and told him that Galen must become a doctor. His medical education began in Pergamon, and later he moved to Alexandria. There he learnt about anatomy, pharmacology and other areas of medical knowledge. Apparently he didn’t much enjoy his time there – Nutton said Galen wrote that he hated the country, he hated the people, he hated the weather, he hated the food. But nonetheless he stayed there for around 5 years, before returning to Pergamon at the age of around 28.

He began to practice medicine in his home town, where he became the doctor who looked after the gladiators. A couple of years later moved to Rome. It’s not known why he moved – maybe just for ambition, or maybe he had other reasons to wish to leave his home town. Once in Rome he gradually built up a reputation as an exceptional doctor. He did this in part by demonstrations, and in part by treating people who then spread the word about being cured by him. Eventually he rose to become the Emperor’s doctor.

Galen wrote a lot. He wrote primarily about medicine, but also about philosophy and about his own life. All three experts agreed that one of the problems with studying Galen is that the best and often only source for his life is himself – which obviously means that any exaggeration or shading of the truth is hard to detect. Galen’s medical texts were partly based on what he had learnt during his education, but they contained a lot of innovative ideas and were grounded in Galen’s own observations of diseases. One of Galen’s primary focuses was on prognosis (and one of his better known works is called On Prognosis) – he was interested in using his observations of the patient’s body and environment to predict what would happen next in the disease. He used a variety of techniques to treat disease – he followed the acknowledged path of the day to first try to cure via the diet of the patient, then use drugs (generally plant based) and then to try surgery. Unusually for an elite doctor of the time Galen did his own surgery, rather than regarding it as too “manual” for a person like himself.

Even by the end of Galen’s lifetime he was beginning to be regarded as the place to turn when learning about medicine. And this grew over the next few hundred years. His works were gradually streamlined into a canon, that weren’t necessarily the whole story, and then were translated via Arabic into Latin. Medieval doctors relied on the information in Galen in their medical education, even though complete texts were hard to come by. But in the Renaissance some of the fundamental underpinnings of Galen’s work were queried – Vesalius began to do dissections on humans and realised that much of Galen’s anatomical knowledge was derived from animals (a point I think they could’ve brought out more earlier in the programme). And Harvey’s work on circulation showed that the four humours theory of how the body works was clearly not the case. But even after this Galen’s pharmacology was still useful (and some parts still are today).

The programme seemed to run out of time a bit abruptly towards the end, so there wasn’t as much on Galen’s legacy as I might’ve liked to hear.

In Our Time: Exoplanets

The first planet orbiting a star other than the Sun wasn’t discovered until 1992 and since then the subject of exoplanets has gone from being something you argue about the existence of to a rapidly expanding field with new discoveries all the time. The experts who discussed exoplanets on In Our Time were Carolin Crawford (University of Cambridge), Don Pollacco (University of Warwick) and Suzanne Aigrain (University of Oxford).

One of the reasons it took so long to discover any extra-solar planets, despite people speculating about their existence for centuries, is that they are very hard to directly see. In fact I think they were saying that none of the known ones have actually been seen. Instead a variety of more indirect techniques are used to detect them, and these required both sophisticated technology & sophisticated knowledge of physics before they could be used. The technology needed to develop to a point where small differences in stars could be measured accurately and consistently over time. And the physics is required to both predict how a star without planets would behave and then to figure out what the differences from this prediction mean.

In the programme they ran through a variety of techniques used to detect planets. One of these is to look at the colour of the star’s light and see if it’s changing between blue-shifted & red-shifted over time. If the star has no planets then you won’t detect that. When there’s a planet orbiting the star it’s not quite as straightforward as the planet circling the star, actually the star and the planet are both circling a point between them (that’s a lot lot closer to the centre of the star than it is to the planet). So the star will seem to move back & forth relative to us observing it. This is biased towards detecting more massive planets, as they’ll move the centre of gravity from the centre of the star more – so-called “hot jupiters” for instance, which are planets the mass of Jupiter that orbit close to their star.

Another method is to look for the changes in the star’s light caused by the transiting of a planet across the face of the star. Obviously this is only possible to detect if the planet is orbiting in the right plane for us to see it. But if you have one transiting where we can detect it then you can detect the existence of other planets in that system by looking at the perturbations of the orbit of the one that transits. You can also detect things about a planet’s atmosphere with this method. The changes in the light of the star can be used to tell you something about the size of the planet (in terms of diameter), and if you look at different wavelengths of light then you’ll see varying diameters. This tells you when the atmosphere of the planet is thin enough to be transparent to that wavelength, and different gases absorb different wavelengths differently so you can figure out the gases that are present. Apparently you can even detect the presence of clouds using this technique.

Another method uses the phenomenon of gravitational lensing. If the light from a distant star passes by a closer to us star on it’s way to the telescope then it will be bent by the gravity of the middle star. A planet orbiting that middle star will affect the lensing effect, and you can figure out things about the size & distance from the star by exactly how the lensing is affected.

If you use the first two methods together you can tell things about the density of the planet. Is it small & heavy? Is it big & fluffy? Or even small & fluffy? There seem to be a wide variety of planet types out there, not all of which are represented in our own solar system. There are also a wide variety of types of solar system out there – Pollaco pointed out that one reason there was argument about the reality of the first exoplanet discovered was because people were assuming that our own solar system was a good model for “all systems everywhere”. It turns out it’s not. The example they used in the programme was systems that have hot jupiters – the first exoplanet was one of these, and the very idea of a Jupiter type planet orbiting with a periodicity of only 4 days was almost unthinkable. They also talked about planetary systems detected around brown dwarves – stars which weren’t quite massive enough to ignite at the end of the formation process. And planets around pulsars (again like the first ones detected) – and one of the experts (I think it was Crawford?) made a throwaway remark about how these are probably not the first planetary system for the star in question. Before a star becomes a pulsar it goes through a supernova explosion, which would probably destroy any original planets – the ones orbiting afterwards are probably secondary captures.

They also discussed looking for planets which might be habitable. Bragg asked if we are thinking about life like ourselves, or germs. The answer was (paraphrasing) “yes”. At the moment no-one knows enough to know what we’re looking for in terms of life on other planets, and at first we’re obviously limited to things we know about life on Earth as a starting point for what to look for. So looking for rocky planets which are neither too big nor too small, that are in the right zone for liquid water. And other things about our own solar system might’ve been necessary – like the presence of Jupiter which draws away some of the comets that could bombarded Earth & wipe out all life. I think it was Aigrain who talked about other ways of detecting life – looking at what we can tell about the atmospheres of the planets. If there are very reactive gases present then they must be being made constantly – some of these we only know of biological processes that make them. So if one could detect such gases that’d be a sign of life.

It was a little bit of an odd In Our Time episode, because there was less of a sense of a narrative than they normally have. It felt like this is because the study of exoplanets is in its infancy – we’re at a point where most of the work is data gathering. I mean in the sense that a lot of planets are being discovered and categorised, but as yet they’re not classified and grouped into types. Nor are there overall theories about how solar systems in general work or were formed – it’s now clear that the one we know isn’t the only sort there can be, nor is it particularly typical of what we’re detecting now.

In Our Time: The Mamluks

The Mamluks were a slave army that went on to rule Egypt (and Egypt’s empire) for around 300 years between the mid 13th Century & the early 16th Century AD. Although we call it a dynasty the position of sultan was generally not hereditary during this period, and before one could be a sultan one needed to have been a slave. The three experts who discussed it on In Our Time were Amira Bennison (University of Cambridge), Robert Irwin (SOAS, University of London) and Doris Behrens-Abouseif (SOAS, University of London).

The Mamluk army was founded under the Ayyubid Dynasty, and soldiers were “recruited” i.e. bought as boys from Kipchak Turks who lived on the steppes, or from Circassians from the Caucasus. These peoples fought as a horse archers, and this was the skill they were purchased for. Once enslaved they were brought to Egypt where they were given a good education, and they were instructed in & converted to Islam. Bennison was keen to stress that this slavery was different to the US model that we are more familiar with – the Mamluks had high status, even as slaves, and in later times in particular were often freed once their education was finished.

When the last of the Ayyubid Sultans died, and his heir shortly after, his widow ruled in her own name for a while. She allied herself with the Mamluks, and subsequently married one of the Mamluk generals who became Sultan in her place. The experts were saying that the Mamluks used this to legitimise their rule – a sense of continuity with the old dynasty. They also did this by reinstating the Caliphate – the last Caliph had died in Baghdad when the Mongols sacked the city & when a relative of his turned up the Mamluk Sultans installed him as Caliph in Egypt. He was a figurehead, but one that meant they were seen as the legitimate Islamic rulers of Egypt & the surrounding area.

Even after they took power the Mamluks were “recruited” in the same way, from the same places. They were mostly a meritocracy – at the end of their education the best & brightest became Emirs and other members of the elite (not just leading the army but leading the country). The position of Sultan was also filled from the Mamluk ranks, and the experts said it was generally not hereditary although sometimes sons did succeed fathers. There was also a lot of assassination as a means of succession – which apparently was also the way in their original cultures, if you killed the King you were fit to be the King. I thought it was fascinating that for so long the Egyptians & surrounding areas were ruled by outsiders.

The “Sons of Mamluks” were generally born to Egyptian mothers, and the experts said they didn’t often enter the army. Instead they were privileged & pampered, and well educated – they tended to serve the country as the civilian bureaucracy. And these men are why the Mamluk era is so well documented by contemporaries – they wrote biographies & histories of their nation.

During the Mamluk era the borders of their empire were fairly static, they had no expansionist goals. They worked to oust the Christians from Syria, and even fought off the Mongols. Perhaps a bit of luck involved in the timing of that latter, as the leader of the Mongol army threatening them was actually back in Mongolia at the time to elect the new Great Khan. But another important factor was that for the first time the Mongols were facing an enemy who fought using their own tactics. Their rule didn’t crumble or collapse towards then end, instead they were conquered in one fell swoop by the Ottoman Empire who took advantage of the distraction of part of the Mamluk army by the Portuguese presence in the Red Sea.

The Mamluk era was generally peaceful & stable, and the experts said that the primary legacies of the Mamluks are in literature (including new poetic forms) and architecture. A lot of the classic buildings of Old Cairo were built by the Mamluk Sultans or their Emirs, and they were responsible for a lot of the infrastructure as well.

In Our Time: Pascal

Blaise Pascal was a 17th Century Frenchman who was a scientist, mathematician & philosopher. Several of his ideas are still recognised today – either still in use (for instance some of his mathematical work) or recognised by the naming of modern things (like the programming language Pascal). Discussing him on In Our Time were David Wootton (University of York), Michael Moriarty (University of Cambridge) & Michela Massimi (University of Edinburgh).

Pascal was born in 1623, and died in 1662 age 39. David Wootton gave us some context for the France of the time which he called essentially the time of the Three Musketeers – so Richelieu is in charge in France, the country is allying with Protestants in the Thirty Years War but in terms of internal politics there is a big crackdown on Protestantism. In the wider world Galileo is active at this time – which took me by surprise as I think of Pascal as nearly-modern but Galileo as end-of-medieval and clearly that’s not a sensible distinction! Descartes is also still alive when Pascal is born.

Pascal was educated at home, his father had planned that the boy should be told about various subjects young but then not study them until later when he was ready for them. But the young Pascal had other ideas – for instance figuring out Euclidean geometry himself once he’d been told about it, rather than waiting till he was taught the subject. One of the people on the programme (I forget which one) said that Pascal was Mozart type levels of genius – just in maths, science & philosophy rather than music. One of Pascal’s first notable works was inventing a mechanical calculator while he was still in his teens – he did this to save his father time (his father was a banker and thus had lots of adding up to do).

Pascal’s work in physics was on one of the big questions of the day – could there be such a things as a vacuum or not. Aristotelian ideas said no, but an actual experiment suggested yes. Pascal repeated the experiment – taking a tube filled with mercury & closed at one end, then inverting it in a basin of mercury. The level of the mercury in the tube drops and a space opens up at the top of the tube, there’s nothing this space can be full of, so it must be a vacuum. Pascal also took these experiments further – looking at different liquids (like water), and testing the effects on the height of the mercury at different heights above sea level. He was one of the first to demonstrate that air had pressure, and that this pressure varied with altitude.

Pascal also had an influence on the future of science & the scientific method. He hadn’t been brought up reading Aristotle as the “answer” to all the questions about the natural world, and he didn’t believe that you required a metaphysical starting point to answer a physical question. So he said that in science there was no appeal to authority, nor was there Truth, just that you looked at the facts as they were and explained them as best you could. Then when more facts were known you might have to change your mind – you’d not have Truth, just have got as close as you could under the circumstances. One of the experts said that Pascal was one of the first people to actually demonstrate this way of having scientific progress – other writers before him had talked about how you could progress in science but he actually did it.

Pascal was also interested in mathematics & he corresponded with Fermat. One of his theorems to do with the geometry of conic sections is still used by mathematicians today. Pascal’s triangle was mentioned briefly on the programme as another example of his mathematical legacy. He was particularly interested in probability, and would work on gambling problems for French aristocrats he knew. He & Fermat worked on a particular problem to do with what the pay out should be for a game of Points that is interrupted before the end. In Points a coin is flipped multiple times, each time it’s heads player A gets a point, each time it’s tails player B does. First player to 10 points wins the pot. How the pot should be split if it’s terminated early depends on what the probabilities of each player winning from the state it’s in (rather than just splitting it according to how many points so far). Pascal & Fermat’s work has had far reaching implications in a lot of the business world, not just in gambling or the specific problem – like insurance for instance.

Later in life (if you can call it that for someone who dies so young) after some sort of intense religious experience Pascal turned away from science & towards religion & religious philosophy. Here he believed strongly in appeal to authority – he built on the work of earlier philosophers who said that human reason is too weak to comprehend the Truth of the world in a metaphysical sense. And so in contrast to his scientific ideas Pascal felt that religious Truth is revealed and is unchanging. Pascal had become a member of the Jasenists, a Catholic sect that built on the ideas of Augustine in the same sort of way that Protestants did – in particular believing that people cannot come to a state of grace through their own efforts, they must be chosen by God to receive God’s Grace and so only the chosen are saved. Mainstream Catholicism of the day believed that by doing good and repenting sin you could come closer to being saved, and so the Jesuits regarded the Jansenists as heretics just as much as Protestants were. One of Pascal’s later works was written to argue that the Jesuits & mainstream Catholicism were wrong, and it was partly arguing based on appealing to the authority of Augustine and saying that the Jesuits were diluting the true Christian morality to make it more palatable to the masses. This work is credited by some later Catholics as having damaged the reputation of the Jesuits enough to have been a contributing factor in their suppression in the late 18th Century.

Pascal’s Wager is one of his philosophical ideas that is still remembered today. Massimi pointed out that it was never intended to convert an atheist, but was aimed at sceptical Christians. In it Pascal says that given there are two states – either there is a God or there isn’t – then there two ways to wager: either bet for God or bet against God. Given this, how should you bet to maximise the chance of a good outcome? If you bet against God and you are wrong, then you will suffer eternal damnation after death, so the best thing to do is to avoid that – bet for God and even if you’re wrong you’ll suffer no consequences. This doesn’t work if you believe there is no God, you need to have doubt about that. It also doesn’t say anything about whether or not Christianity is the Truth – Massimi pointed out that one objection to Pascal’s Wager is that the same argument can be made for any religion. And if you enjoy this world’s pleasures then there is also a down side to betting for God, making it a less obvious choice (definitely no pleasure now as vs. possibly no pleasure later, a more complex situation to weigh up) – which was not a problem that Pascal had. He said once that life was like being chained in a dungeon in the dark, and every so often the guards come in and strangle someone. Cheerful fellow …!

In the summing up section of the programme they discussed how Pascal’s legacy lives on in science & mathematics but is most influential in religious thought. The three experts credited him with laying the foundations of modern Christianity – in that faith & religion now are seen as something that you choose to believe in without needing a rational argument. And that is a very Pascalian way to see it.

In Our Time: Queen Zenobia

I’m sure I’d heard the name of Queen Zenobia before, but I’m equally sure I’d got no idea who she was other than a vague sense of “classical era?”. After listening to the In Our Time episode about her I now know rather more. The experts who talked about her were Edith Hall (King’s College, London), Kate Cooper (University of Manchester) and Richard Stoneman (University of Exeter).

Zenobia lived in the 3rd Century AD, and was the daughter of the Governor of Palmyra in Syria. Her family were Roman citizens and the experts suggested that they probably thought of themselves as Romans first & Syrians second. Zenobia claimed descent from the Ptolemies (so also from Cleopatra) and was also related to a previous Roman Empress (Julia, who was married to Septimus Severus who was Emperor around the turn of the 2nd Century AD). She was married to Odaenathus, as his second wife, who was Governor of Palmyra after her father’s death. Odaenathus died in suspicious circumstances, as did his eldest son (whose mother was not Zenobia). Stoneman said that there was no evidence that Zenobia had organised her husband’s murder, but there is also no evidence for it being someone else. His opinion was that it was a rival of her husband’s who had done the deed, but then Zenobia had taken charge before the rival could. She then governed Palmyra – at first on behalf of her son, but later in her own right.

Palmyra was an important city in the trading network that stretched from the Roman Empire across the lands to the east. It was situated in an oasis that had been a caravan stopping place for millennia, and the town had become rich from the control & protection of trade. By Zenobia’s time it had been a part of the Roman Empire for quite some time, and the experts seemed sure that Zenobia’s father would’ve regarded himself as a Roman keeping order for the benefit of Rome. By later in Zenobia’s reign it was clear she didn’t.

At this period the Roman Empire was in a bit of a shaky state – there’d been 19 Emperors in 30 years (by the late 260s AD) most of them having been assassinated. Unrest and barbarian incursions in the north and west of the Empire had distracted attention from the east, which was mostly left to its own devices. Zenobia took advantage of this and quite quickly conquered an empire of her own that ranged from parts of modern day Turkey round the east coast of the Mediterranean to Egypt. The experts suggested that her method of “conquering” was mostly to offer a more stable & powerful state to the leaders of the various towns & regions – capitalising on her family & personal networks of contacts & allegiances. The experts disagreed about whether conquering Egypt was a good idea or not – I think it was Hall who was suggesting it made strategic sense as the place to put her borders, but Stoneman thought that it unnecessarily antagonised Rome. Hall was also suggesting that Zenobia had sentimental reasons for including Egypt in her empire – due to her claimed descent from Cleopatra.

Unfortunately for Zenobia’s fledgling Palmyrene Empire the Roman Emperor Aurelian (who came to power in 270AD) was more effective than his predecessors. He recaptured the breakaway western parts of the Empire (in Gaul & Britain) and defeated some of Northern barbarians. He also regained a bit more control over the economy and political situation in Rome. So now he was free to turn his attention to the east, and deal with Zenobia. As I mentioned in the last paragraph Stoneman pointed out that Egypt was where a lot of the food for the Empire was grown, and so Zenobia had made herself a target that couldn’t be ignored.

There were two, or possibly three, major battles in Aurelian’s campaign against Zenobia & the Palmyrenes and Zenobia was defeated and forced to flee in all of them. After the last one Zenobia was captured, and Palmyra was eventually sacked (I think not immediately after Zenobia’s defeat but after it tried rebelling a subsequent time). Zenobia was to be taken to Rome, to be paraded as a captive through the streets of Rome in Aurelian’s triumph. There are doubts as to whether that happened or not, and what subsequently happened to Zenobia. Stoneman thought that after the triumph Zenobia was allowed to retire to a villa and live out the rest of her life in obscurity, rather than be executed. Hall & Cooper gave another couple of possibilities – Zenobia may’ve been executed, but she also may never’ve reached Rome. She might’ve died of disease on the way there, but Hall was convinced that Zenobia would’ve suicided rather than be paraded as a captive.

There was a bit more of a “herding cats” feel to Bragg’s moderation in this episode – Hall and Cooper were both very enthusiastic, and all three experts got a bit sidetracked from time to time with other subjects that weren’t quite the subject of the programme.

In Our Time: Icelandic Sagas

The Icelandic Sagas were written down in the 13th Century and tell the stories of the original colonists of Iceland and their descendants. On In Our Time the context & contents of these sagas were discussed by Carolyne Larrington (St John’s College, Oxford), Elizabeth Ashman Rowe (University of Cambridge) and Emily Lethbridge (Árni Magnússon Manuscripts Institute in Reykjavík).

Iceland was settled primarily by Norwegian aristocrats and their households from the 9th Century AD onwards. In Norway at the time the King was beginning to centralise more power which wasn’t going down well with these aristocrats, hence their move. As well as the Norwegians there were also other Scandinavian settlers, including some who had settled in parts of the British Isles first. And a not insignificant number of Celtic women from the British Isles. The society they set up in Iceland didn’t have a King, instead there were 36 or so chieftains who met at the Althingi to decide on laws & settle court cases. The sagas are often about these court cases, which makes them sound rather dry but these cases would be to settle things like family feuds which had got out of hand with lots of death on both sides so they’re anything but dry.

During the programme they told us the plot line of part of one of the sagas – the Laxdæla saga. In this two foster brothers (their genealogies are told in an earlier part of the saga) make a trip to Norway & they leave behind in Iceland a woman (Guðrún) that one of them (Kjartan) intends to marry. She would rather have made the trip with them, but was told it wasn’t appropriate. Kjartan remains in Norway longer than his foster brother (Bolli), who when he returns fails to pass on greetings from Kjartan to Guðrún and instead gives her the impression that Kjartan has found himself a new woman. Bolli & Guðrún marry, and when Kjartan returns to Iceland he’s not happy with this state of affairs. Eventually Bolli kills Kjartan, and then Kjartan’s brothers seek vengeance on Bolli & kill him. Guðrún is pregnant with Bolli’s son at this point, and when the boy grows up he seeks vengeance on his father’s killers. The saga as a whole tells the story of all four of Guðrún’s marriages.

Christianity came to Iceland around the year 1000AD, and with Christianity came the writing of books. At first religious texts were the only books written down but by the 13th & 14th Centuries the Sagas were being written. They were explaining that the coming of Christianity influenced the way these sagas were told or rather written down – in some ways the stories are divided into what might be thought of as an Old Testament & a New. So the people who lived prior to Christianity reaching Iceland are often depicted as virtuous pagans (by Christian ideas of virtue) or incidents in their stories are pre-figuring eventual conversion or reflecting biblical imagery.

Lethbridge talked about how the sagas are very much rooted in the landscape of Iceland. The places where events take place are real places that you can go and visit. And people who live nearby can tell you the stories that are associated with their local area. The sagas are still very much a piece of the identity of Icelandic culture, and the return of the physical manuscripts when Iceland became independent after the Second World War was an event that a lot of the population turned out on the streets to witness. People living in Iceland today can often trace back their family history to the people talked about in the sagas.

There is some debate about how much of the stories in the sagas are true. Clearly the supernatural parts (like the dead who don’t stay in their graves but come back to fight you) didn’t really happen. But in terms of the non-supernatural stuff some of it can be corroborated from other sources, although some can be disproved or disputed using these sources. For instance people & places exist independently of the sagas, and some of the events are recorded in more sober histories. But equally some descriptions of laws or events are clearly written long after the fact as they’re anachronistic for the time the saga is set. One of the experts said you can think of the sagas as being like historical novels – the facts are used but then dialogue & details are added to make it a good story.

The sagas generally share a narrative style. They are written fairly neutrally, and talk about what people said or what people did not what they were thinking. The narrator doesn’t take sides or judge the characters. The furthest they go is to say things like “and many men agreed this was not wise” – putting the judgement in the things other characters said at the time. There are interludes of poetry, said to be composed by the characters in the saga, which do convey something of the internal thoughts of a character and the experts were saying that this poetry was possibly composed at the time of the saga’s stories and passed down orally.

Women in Iceland in the era that this stories took place did not have legal standing – and so had to work through the men in their lives. The experts said that despite this women in the sagas are written about much like men, as real people, and the sagas will often have female characters who do act and get their own way. Even if it is through men because of the legal system, they’re still shown with agency of their own.

Near the end of the programme Bragg went off on a little diversion about language. He repeated a story he’d heard about speakers of Cumbrian dialect being able to make themselves understood to Icelandic speakers & vice versa after a little bit of time & some good will on both sides. The experts agreed that there’s sufficient Norse influence in Cumbrian dialect that this is plausible (and I think they agreed that the particular story he’d heard was true too).

In Our Time: Relativity

Physics is one of those subjects where I can very clearly see the boundaries of my understanding – as soon as we get to quantum physics or Einstein’s theories of relativity I can follow the surface level explanations & analogies, but I’m always aware I don’t understand it on a deeper level. I assume the same is actually true of all subjects at some point – I’m not a genius, and I spread my self-education widely among many subjects rather than deeply delving into one – but for physics I can see the fence. It’s a peculiar sensation.

The three experts who talked about Einstein’s theories of relativity on In Our Time were Ruth Gregory (Durham University), Martin Rees (Astronomer Royal and University of Cambridge) and Roger Penrose (University of Oxford). The programme started with a bit of context: in 1905 Einstein published four papers, including one on Special Relativity. At the time he was working as a clerk in a patent office & was previously unknown as a physicist. Ten years later he published a paper extending Special Relativity into General Relativity.

Prior to Einstein’s theories of relativity the assumption was that there was some sort of objective measure of time in the universe, the same no matter how it was observed. Einstein theorised that the motion of the observer affected the observation of the passage of time – hence relativity. Apparently he later regretted using that word for his theories because it’s been used since to imply that physics is all just subjective & depends on your point of view, but actually there is still an objective physical reality which can be described mathematically & rigorously it’s just that within the system the point of view of the observer is important for the observations made.

One of the things that Einstein’s theories grew out of was the observation that the speed of light remains constant no matter what direction you’re travelling in or how fast you’re travelling. This seems to be a paradox. Say you think about driving a car towards or away from another car that’s driving towards you – when you’re travelling towards it, it gets closer to you quicker than if you’re travelling away from it. (I hope that makes sense.) But with light if you’re travelling towards it it appears to be travelling the same speed as it travels if you’re travelling away from it. Einstein’s theory explains how this happens by explaining how time is running differently (I think).

Special Relativity implied that time is another dimension like the spatial dimensions, and Minkowski built on this theory to mathematically describe spacetime. Einstein then used this mathematics as part of his theory of General Relativity. One of the key insights of General Relativity is that spacetime is curved by the presence of mass and this curvature explains why gravity exists. Gregory used an analogy I’ve heard before to describe spacetime & its curvature – thinking of spacetime as being like a four-dimensional version of a two-dimensional rubber sheet. If you have your rubber sheet suspended as a flat horizontal plane and then you put something large like a bowling ball on it, the sheet will be distorted & curved where the ball weighs it down. Then if you roll a marble across it it will accelerate down the slope towards the bowling ball – or if you get your angles and speed right you can make it orbit the bowling ball.

There was some discussion of the twin paradox at two different points in the programme. This is a thought experiment where you have twins one of which remains on Earth, and the other one travels away to a different star system at close to the speed of light, and then returns. When the twins meet again the one that stayed on Earth will be older than the one that went to the stars and back. This is a staple of science fiction, and I think the first time I ran into the idea was in “Time for the Stars” by Robert A. Heinlein which I read when I was at middle school. The first time it was discussed on the programme was in the context of Special Relativity as the way of demonstrating what Einstein is talking about. And they mentioned that this has actually been shown experimentally – by getting a very accurate clock (synchronised with a matching clock) and putting it on a plane and flying it to the other side of the world & back. Then when you compare the two clocks the one that travelled has measured less time than the one that stayed put. Gregory pointed out that the observations demonstrate both the effects of relative motion and the effects of distance from a massive object (the maths needs to take into account that the plane is up in the air while the other clock is on the ground). I had no idea prior to this programme that the effects were measurable on such a human scale.

The second time the twin paradox came up was in the context of talking about the geometry of spacetime. Penrose was explaining that with his theories Einstein was trying to explain the universe in geometrical terms. Spacetime is four-dimensional, three dimensions are the familiar spatial ones that can be explained using Euclidean geometry. For the fourth dimension, time, Einstein (and Minkowski?) showed that you could use almost the same geometric rules only needing to reverse a sign – turn a plus to a minus. The way Penrose explained what he meant by this was to use the twin paradox – one twin is moving from event A to event B along a straight line in the time dimension, the other is moving from A to B on a curved line in the time dimension. For the spatial dimensions a curved line is a longer path than a straight line, for the time dimension a curved line is a shorter path than a straight line. (And this is what I mean by being able to see the edge of my understanding – I can write that last sentence as a fact and accept it is true, but I don’t understand why or how.)

I know I’ve missed out various things they discussed but I shall only mention another couple before I finish the post. Firstly there are real world applications of the theories of relativity, it doesn’t just help physicists understand the universe – it’s an important part of the underpinning of how GPS works. The other thing was that Rees was saying that Einstein was in some ways more like an artist than a scientist. By this he meant that for an artist their work is generally unique, if they didn’t exist no-one else would produce the same artworks. But for science generally if one person doesn’t come up with the theory or do the experiment then someone else would not long after. Rees thought (and the other two agreed) that while Special Relativity would probably have been thought of by someone else soon after, General Relativity was such a large jump that if Einstein hadn’t thought of it then we might still have not thought of it.