Brian Clegg's Blog, page 13

Sour? Doh!

You might not think bread is the kind of thing where fashion is important - and it's not if you think of the more basic loaves. But get into the fancier end of the market (always more expensive, usually tastier and sometimes, but not always, healthier) and fashion reigns supreme. For some time now sourdough has been at the forefront of the fancier bread market, though wild flour is making some inroads, which is fine. But sourdough should be a choice, not inescapable.

The trouble is, I don't really like sourdough. I'm not particularly fond of its distinctive taste, the crust is way too hard - I always think I'm at risk of breaking a tooth on it - and it doesn't toast well, not starting to darken and crisp up until the crust is burning. We won't even mention those irritating holes that make it difficult to butter it or put jam on.

I have three corner shops, in the sense they are only 5 minutes walk away - Asda, Marks and Spencer, and Lidl. I particularly like the M&S bakery bread - their baguettes are the best I've had from a non-specialist baker outside of France. But they have gone sourdough mad. I'd say at least 75% of their fancier loaves are sourdough - and those that aren't are all white bread. The only wholemeal non-sourdough bread I can get from the bakery is a basic tin loaf.

I suspect sourdough is something of a bubble (get it?) in the marketing sense - at least, I hope so, and we can return to getting a better balance of fancier bread options for those of us who aren't dedicated followers of fashion.

Image (not M&S) from Unsplash by Mae Mu.

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Weather wonders

My latest book is out - Weather Science. We've had so many books on climate, but relatively few on weather. The distinction is often a puzzle, but it has been summarised in a neat little aphorism: 'climate is what you expect; weather is what you get'. If you look this up online it tends to be attributed to one of two US writers - Mark Twain and the twentieth century SF author, Robert Heinlein. 

Twain did write something a little similar 'Climate lasts all the time and weather only a few days' - but this lacks the effectiveness of the phrase above. Heinlein certainly used the wording in his treacly, 'wisdom'-laden, over-long late book Time Enough for Love, but this wasn't original. It's been suggested instead that it was first penned by Oxford geographer Andrew Herbertson in a 1901 textbook, though as is always the case with such sayings, it is entirely possible it was already in circulation well before that date.

Weather Science, then, takes a look at what we experience from the climate, whether it's the heavy duty stuff such as hurricanes and lightning or the gentler everyday possibilities of whether or not it will rain tomorrow. As well as the different weather phenomena it looks at forecasting and even attempts to modify the weather (on the whole rarely demonstrated with any certainty to work).

Here's a summary from the book's blurb:

Everyone has an interest in the weather, whether it's to check the prospects for a day out or to know when best to harvest a crop. The Earth's weather systems also provide some of the most dramatic forces of nature, from the vast release of energy in a lightning flash to the devastating impact of tornadoes and hurricanes.

For centuries, our only real guide to future weather was folklore, but with the introduction of the first weather forecasts and maps in Victorian times, attempts were made to give some warning of the weather to come. Until relatively recently, these forecasts could be wildly inaccurate - think of Michael Fish's denial that there was a storm on the way the night before the UK's great storm of 1987. This was due to the mathematically chaotic nature of weather systems, first discovered in the 1960s, the understanding of which would transform forecasting from the 1990s and mean that meteorologists became some of the foremost users of supercomputers.

From the crystalline perfection of the snowflake to the transfer of energy from the Sun, science lies at the heart of the weather and our understanding of it. In recent years, weather science has moved to the leading edge with advanced modelling, versatile use of satellite data and a better understanding of mathematical chaos. This is a true example of hot science at work.

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Revisiting the Dirac Sea

REVISIT SERIES:
A post from July 2013 - 

I've written two books about infinity, notably A Brief History of Infinity, and it's a subject I enjoy writing and thinking about. But for physicists, infinity often means a problem. While we can conceive that the universe might be infinite, because we only ever deal with a part of it, when infinity rears its head in calculations, it usually means trouble. This most famously arises in quantum electrodynamics, the science of the interaction of light and matter on the quantum scale. The solution there has been renormalisation - in effect, putting in the real observed values of some quantities to make the infinities go away. And this works, but it's a bit uncomfortable. Elsewhere, such as at the moment of the big bang or in the heart of a black hole, the infinities are taken to mean that our current theories break down at that point and we need to find new ways to look at what's happening.

However, there is another class of infinite entities that is tolerated by some, because they produce useful results, but that others find a little uncomfortable. Two examples spring to mind, both from the quantum world - the Dirac sea and the many worlds interpretation of quantum physics. I'd like to take a look at the less frequently covered of these, that unusual infinite ocean.

Paul Dirac was a superb (if rather strange) British physicist who was one of the leading lights in quantum theory, though he tends to be less well known in the outside world than the likes of Heisenberg or Schrödinger. (See Graham Carmelo's The Strangest Man for more on Dirac.) One of his crowning achievements was to extend Schrödinger's wave equation for some types of quantum particle, which describes the behaviour of those particles, so that it matches the real world. The original version was not relativistic - like Newton's laws it was an approximation that assumed particles moved fairly slowly. But an electron, for example, is often no slouch and it's Dirac's equation you need to keep track of it, not Schrödinger's.

However, something interesting emerged from Dirac's work. The equation has a kind of symmetry of solution that makes it equally possible to have positive and negative energy particles. Sometimes the negative parts of such equations have just been ignored. This happened most famously with 'advanced waves' - Maxwell's equations, describing electromagnetism and light, suggest there should be photons that travel backwards in time from destination to source as well as the usual forwards ones. These were simply ignored until Richard Feynman and John Wheeler realised they could be used to explain another oddity of physics. Dirac, though, did not simply cast his negative energy electrons away. But that led to a problem.

Light is typically produced when an electron drops an energy level. The electron loses energy and this is emitted as a photon of light. Eventually the electron gets to a 'ground state' below which it can't drop any more. But if negative energy levels were allowed, as Dirac's equation suggested, electrons should continue dropping in energy for ever, blasting out vast quantities of light. They don't. So Dirac came up with a the idea that the vacuum - empty space, if you like - contained an infinite sea of negative energy electrons, filling up all the negative energy levels, so your ordinary, everyday electron could never drop into negative energy.

This seems a very unlikely and highly wasteful proposition, requiring as it does this infinitely deep and wide sea of inaccessible particles. It rather typifies the subtitle of my book - 'the quest to think the unthinkable'. However it proved a very productive idea. The model predicts that there will sometimes be holes in the sea - gaps where a negative energy electron is missing. As it happens, a missing negative energy electron is identical to a present positive energy, positively charged equivalent of an electron. Dirac predicted these should exist, and a couple of years later, the positron was discovered. This hypothetical infinite negative energy sea enabled Dirac to predict the existence of antimatter.

Does the sea have any physical reality? That's a difficult one. Some physicists would say yes, while others would hedge their bets with philosophical waffle about the nature of reality. The fact remains that Dirac's infinite sea of negative energy particles has played a powerful role in the development of physics.

That's what I call a big idea. See all of Brian's online articles or subscribe to a weekly digest for free here

 

In the footsteps of Jocelyn Bell

When I was in my last year at Cambridge, by which time my Natural Sciences degree had been refined down to experimental physics, I had to do a project. I had always been fascinated by radio astronomy, often passing Jodrell Bank on the way to a friend's house when at school: with a fellow student I was offered the chance to try some basic radio astronomy. We weren't given a handy, off-the-shelf, giant steerable dish, though. We had to start from scratch.

One huge advantage I had in teaming up with Dave Izod (apologies if I got the name wrong - it was a long time ago) was that he had the huge advantage of being a (then) rare undergraduate with a car. The Mullard radio astronomy observatory was over four miles from my college and I didn't have a bike. 

One of the reasons the exercise was so satisfying was that it involved picking up a whole range of new skills. The starting point, for example, was using a theodolite to determine levels before partially constructing and deploying an antenna that bore more resemblance to a bed frame than the familiar dish shape. There was then a whole host of measurements to be made before data could be collected and some attempt made at interpreting it (with a large amount of help from a patient grad student).

We did finally manage to pick up some radio signals and have a guess at what they were (sorry, analyse them), but what this brought home was the sheer indirectness of radio astronomy - particularly at a time when the technology employed was often so basic. This was as compared with modern equipment's ability to give you far more than just a list of numbers on a print out, which was all we got. I am totally in awe of Jocelyn Bell Burnell (at the time Jocelyn Bell) who had detected the first pulsars using equipment that was similarly basic (if much larger - see part of her 'array' illustrated above) less than 10 years before.

There is considerable controversy over Bell Burnell's lack of a share in the Nobel Prize - she herself has always been surprisingly sanguine on the matter, saying that she didn't think it was appropriate for research students to receive the Nobel 'except in very exceptional cases', which she didn't believe hers to be. However, I am more inclined to follow the lead of one of my other Cambridge-based astronomical heroes, Fred Hoyle who thought this was, indeed, an exceptional case and that her omission was more a matter of sexism on the part of the Nobel committee than anything else.

Whatever was the reality, working briefly, if on a toy project, at the Mullard was an amazing experience and hugely increased my admiration for those who have brought us such discoveries. Modern science writing often gives us a bit more a feel of the realities of scientific work - but I think radio astronomy is one field where we are so aware of the dish antennae that it's easy to forget what important work was done with a few wires, crude equipment, no computers and a lot of hard work.

Image: Part of the Cambridge Interplanetary Scintillation Array - c ourtesy of the Cavendish Laboratory, University of Cambridge.

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The Baywatch principle revisited

REVISIT SERIES:
A post from July 2012 - Science isn't always great at naming things. For every photon there are plenty of clunky names that don't do a lot for you. Take, for instance,  the 'principle of least action', which sounds like a description of the lives of teenagers. This is a shame because it is really interesting. For reasons that will become clear I like to think of it as 'the Baywatch principle.' And what it says, in essence, is that nature is lazy.

French mathematician Pierre de Fermat used the principle of least action to explain why light bends as it moves from a thinner to a thicker substance (from air to glass, for instance) – and Richard Feynman made it a fundamental part of quantum electrodynamics.

The principle of least action describes why a basketball follows a particular route through space on its way to the basket. It rises and falls along the path that keeps the difference between the ball’s kinetic energy (the energy that makes it move) and potential energy (the energy that gravity gives it by pulling it downwards) to a minimum. Kinetic energy increases as the ball goes faster and decreases as it slows. Potential energy goes up as the ball gets higher in the air and reduces as it falls. The principle of least action establishes a balance between the two.

This principle is applied to light by considering time. The principle of least time says that light takes the quickest route. Fermat had to make two assumptions – that light’s speed isn’t infinite (the speed of light was yet to be measured in 1661 when Fermat produced this result), and that light moves slower in a dense material like glass than it does in air. We are used to straight lines being the quickest route between any two points – but that assumes that everything remains the same on the journey. In the case of light going from air to glass, bending is the quickest route. To see why this is the case, compare the light’s journey to a lifeguard, rescuing someone drowning in the sea. The obvious route is to head straight for the drowning person. But the lifeguard can run much faster on the beach than they can move in the water. By heading away from the victim, taking a longer path on the sand, then bending inwards and taking a more direct path in the water, the lifeguard gets there quicker.

Similarly, a light ray can reduce its journey time by spending longer in air and less time in glass. The angle that minimizes the journey time is the one that actually occurs.

When Richard Feynman was inspired by the principle of least action to come up with quantum electrodynamics, the theory that describes the interaction of light and matter so brilliantly, he imagined not just the one “best” path but every single possible path a particle could take in getting from A to B. At the heart of QED is the idea that you can identify the particles behaviour by taking a sum of every single possible path combined with the probability of that path occurring. See all of Brian's online articles or subscribe to a weekly digest for free here

 

WFH and TV

In a recent article, the redoubtable comedian David Mitchell noted that the office supply company Toner Giant had published research showing that a high percentage of those working from home (yes, it was WFH not WTF) watch daytime TV. Sadly, as is often the case when the media comments on data, Mitchell did not provide a link to the original source - it's here if you want it.

There are two interesting bits to this - one is what people allegedly watch and why Toner Giant is telling us (Mitchell struggles to understand why they did this, presumably because he didn't read the whole original piece, which tells you) - and the other is whether or not this is a problem.

The claim is 82% of UK hybrid workers admit to watching TV when working from home - this is based on a 'survey of 2,000 British hybrid workers', though we aren't told how they were selected and hence how representative they were (or weren't). Why does Toner Giant care? Because they claim that personal printing from working at home costs £121,323,121.90 each year - and, by implication, if you use their toner it'll be cheaper.

This is, of course, a wonderfully, ridiculous accurate figure - a sure sign of dodgy statistics. Leaving aside that mindboggling 90p, it's based on an estimation that the average spend per year on employee's printing needs is £700 (remind me how this can get to an number ending with 90p). They sourced this cost from a company that sells digital document handling, presumably who have a small axe to grind here, but give no details of how this number was calculated. I've worked from home for decades, and that's a good five times bigger than my most costly year.

But going back to the claim about watching TV, this underlines a point I've been making ever since trying to get more working from home when I was a senior manager in a corporate in the early 1990s. I had other managers saying effectively 'Unless we can see them, they are not going to be working all the time. They'll skive off.' And that's still the viewpoint today, highlighted by this article. I'm not saying that there aren't any people watching TV or whatever instead of working - but the point I made way back then, and that still holds, was that this should be totally irrelevant.

If we have a decent management system, how employees divide up their time should not make any difference - because we should be managing on output, not input. If WFH employees produce the desired quality and volume of output, they are doing the job well. Whether it takes them 12 hours a day or 2 is totally irrelevant. Of course there are many jobs where this can't apply, just as there are many jobs that can't be done from home. But if you are doing anything from writing code to processing forms, time at the grindstone is no measure of doing a good job. I got that resistance back then because many managers simply didn't know enough about the jobs they were managing to be able to monitor quality of output - and I suspect that's still the case. The problem with WFH is not workers taking time away from the computer to make their day more interesting... it's management incompetence..

Image by Minja Radonja from Unsplash

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An Unsuitable Job for a Woman - P. D. James ****

P. D. James was one of the great English crime writers, with one of the more interesting detectives in Adam Dalgliesh, but reading this novel from 1972 I was struck by how interesting it was to me for two reasons. One is purely personal - it's set in Cambridge just a couple of years before I was there, so comparing the picture James paints with my own experience was fun. But more significant is the stylistic approach she takes.

I'm a great fan of Margery Allingham - and the central character in James' book is a pure Allingham heroine - Cordelia Gray is young, feisty, intelligent and taking on a role that would in earlier years have been considered the 'unsuitable job for a woman' of the title - a private detective. Although technically an Adam Dalgliesh book, we only get indirect references to him until the final chapter where he makes an appearance, very much as a supporting character.

But it's not really having a murder mystery where the author's detective is sidelined that makes this particularly striking - it's not just Cordelia's character that feels like the work of Allingham. The whole thing feels as if it comes from an earlier period, fitting far better with Allingham's arguably best inter-war books. Of course there are some aspects that bring us back to the second half of the twentieth century, such as Cordelia driving a Mini - but on the whole it could so easily have been set 40 years earlier. Cordelia even spends most of her time living in a cottage without electricity.

This period feel also comes out in the portrayal of Cambridge student life - what's front and centre is lying around with picnics and fizz and punting. I'm not saying that such things didn't exist in the 70s - of course they did - but for most students they were far less central than they seemed to be to the characters that James portrays there.

If I'm honest, this is not a great murder mystery - the plot feels a little contrived and unlikely. But taken as a novel that's not so much a pastiche as an homage it's lovely - and although the scene-setting does not feel like the 70s, it is beautifully done for an earlier age, making it a pleasure to read.

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Wiltshire science and Mark O'Donnell

For a number of years I was proud to count the late BBC Radio Wiltshire presenter Mark O'Donnell as a friend. He very sadly died at the end of 2019 - but I wanted to look back and remember some remarkable inserts we made for his show. 

The idea was to visit science and technology locations in Wiltshire. It was a great opportunity to find out more about these places, whether historical or modern. What made the visits was Mark's warm presence and ability to draw the listener in to the scene. Sadly the BBC has not kept the tapes of the visits, but here are a few written highlights from me.

The startling significance of Mr Talbot's spectacles - visiting Lacock Abbey and the scene of the first negative imageA revelation in Wroughton - at the Science Museum controlled environment store and library (a location that so impressed me that I suggested it as a location for my little TV piece teaching quantum physics to then BBC business editor Robert Peston)How oxygen was first discovered in an adventure playground - visiting Bowood House and Joseph Priestley's laboratoryA scary time at Porton Down - inside the Health Protection Agency's controlled laboratoriesDo you like Dyson? I don't know, I've never Dysed - off to Malmesbury to see Dyson's R&D centre (and trying not to call them hoovers)Forget Houston, I've been to Swindon - the surprise location of the UK Space AgencyWhat is it? A puzzle from our visit to the WRC in Swindon

Just to finish, Mark's producer for much of his time at the station and now presenter Karen Gardener gave this tribute to Mark on her show shortly after his death.

Image from BBC

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The Monk - Tim Sullivan ****

It’s always satisfying to come across a well-written murder mystery and discover there are several more waiting. In this case I accidentally started with book 5, but have since gone back to the first of Tim Sullivan’s novels featuring DS Cross.

The most interesting feature of the series is that Cross is on the autism spectrum. This gives him some distinctive advantages over his colleagues, while also offering some challenges. On the whole Sullivan handles this well - in this book, almost all of Cross’s colleagues regard him with affection, though we are told that in the past he was treated badly. That is perhaps the most unlikely aspect - it’s hard to imagine that policing has so many suitably thoughtful officers, though I may be resorting too much to stereotype.

The murder victim is a Catholic monk, with much of the action taking place in an abbey - also well handled and providing a neat tie-in to Cross’s enthusiasm for church organs.  The monk’s background is unusual, giving opportunity for a suitably twisty plot. One oddity here is that, given the relatively low numbers of Catholics in the UK, a surprising number of the characters in the novel seem to be Catholic or to have ties to that church (not just those involved with the abbey).

Something else relatively unusual is the way that Cross undertakes interviews later in the book, though the approach only really works because he already knows quite a lot about what actually happened, and so can lead the suspects through a web of lies - unlikely though this is, it’s very satisfying. Sullivan brings the key interview with the suspect centre stage, dedicating around the last quarter of the book to this, with the exception of a twist that comes after it. Having since read several other Sullivan books, this is a standard feature of the series.

This isn’t the sort of murder mystery that makes you go ‘Wow!’, but it is very enjoyable and engaging if cosy mysteries are your thing. Occasionally the writing is a touch lazy, and perhaps too much is made of Cross’s colleagues reactions to his autism, but overall I’ll definitely be reading more. One tiny moan, perhaps indicating that laziness, concerns the line ‘the odometer never went over seven miles an hour’ - well no, it wouldn’t, would it, considering what an odometer measures.

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Evidence of absence

The other day, reading Tom Chivers' excellent book on Bayesian statistics Everything is Predictable, I was reminded of that old chestnut, 'absence of evidence is not evidence of absence.' This is often put forward as if it were a powerful logical argument. But, in reality, it's a bit of common sense that sometimes works, but always oversimplifies.

In case you aren't familiar with the expression, I might say that I've never seen any evidence that dark matter exists (as opposed to the behaviour of galaxies and galactic clusters attributed to dark matter), but I shouldn't take that as evidence that dark matter doesn't exist.

As Tom Chivers points out, this is very frequentist thinking. The Bayesian approach would be that every good quality experiment that fails to find dark matter modifies our priors - it can be used to reduce the probability that it exists.

Interestingly, this somewhat trite saying only tends to be wheeled out when responding to a theory we agree with. I can imagine UFO enthusiasts saying 'just because there isn't good evidence, it doesn't mean they aren't out there.' While technically true, the rest of us would probably say that we're inclined to take the lack of good evidence, particularly now everyone carries a camera all the time, as evidence of absence.

Note that this is totally different to saying that lack of evidence definitely means that something doesn't exist - of course that's not true. Yet if you keep looking for something and fail to find repeatedly, it is logical that this should reduce the probability you apply to its existence. And in practice, science often does this. For years, experiments like the famous Michelson-Morley one attempted to find evidence for the existence of the luminiferous aether. No evidence came to light, and over time the likelihood of it existing was reduced, helped by a theory that made it unnecessary.

The reality, then, is absence of evidence, when that evidence is searched for effectively, is evidence of absence. It's just not proof.

Image from Unsplash by Albert Antony

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