Saturday, 4 July 2020

In the House and Beyond: in praise of serendipity

The word ‘serendipity’ appears in more than one in five of my posts. I checked. It swims just beneath the surface in many more – arguably in the majority. My Oxford English Dictionary defines it as “the faculty of making happy and unexpected discoveries by accident”. Happy accidents; happy surprises. Just so. Given that the principal theme to this blog relates to my personal reflections as a scientist on topics and events that have entered my life, it would be fair to conclude that serendipity has played a major role within my career, and beyond. However, despite that glowing background, it might seem a little odd to write about making happy and unexpected discoveries in this the year of COVID19. Far from it. There have been some very positive outfalls from the necessary restrictions to all our lives: from the sound of birdsong and rustling leaves free of traffic noise (and fumes!) to the presence of skies unspoiled by aircraft contrails, and all the way up to clapping newly recognised heroes from our doorsteps and the rediscovery of the importance of each other. Whilst I could wax lyrical about such things, it’s perhaps best to stay within the blog’s overarching theme lest I be carried away, or off …

In a tweet posted earlier today (3rd July; screenshot above) Daniel Harding highlighted serendipity’s role in the developments of my life. In fairness, I opened myself up for the comment because, a few days ago, I had revealed as much in a conversation he’d recorded as the opening salvo in his new podcast. (‘Zoom for Thought’, which you’ll be able to find and listen to here; it’s also on Spotify if you prefer. The episode in question is the very first one.) Apart from being a thoroughly nice person with whom to spend a little time in conversation, Dan is also someone I admire for his abilities in music. Indeed, there are CDs that owe their place on my shelves to his enlightening comments and suggestions, begun when I was still a physics lecturer at the University of Kent and he the university’s Deputy Director of Music. We bump into each other still on occasion – or did prior to March of this year – but have mostly kept in touch via posts and messages on Twitter. It would be hard to identify precisely the thread which led to our recorded conversation and the resulting podcast – but it certainly qualifies as serendipitous. Listen for yourselves here, or click on the embedded copy below; it’s sixteen minutes long and includes a wonderful few seconds in which I manage to tie my tongue in quite a knot.

As you listen you’ll hear mention of the U3A (University of the Third Age, specifically the Canterbury group) and it’s my involvement with the U3A that really kicked off the idea that Dan floated concerning his new podcast. It boiled down to his suggestion that we have a chat about the creative ways in which he and I were trying to continue to teach, play music, share passions and perform during the various stages of COVID19 ‘lockdown’. Why me?* Well, because he knew that I had sought a way to continue offering scientific insights in spite of the lockdown and that the effort had given rise to my ‘Physics in the House’ video series – the details of which are in an earlier blog post, here. My idea, such as it was, centred on using objects or devices one might be familiar with in the house to illustrate a particular topic in physics. I hoped that by doing this, and by keeping the mathematics to an absolute minimum, I might encourage a few people to realise how central is the subject to their daily lives. Beyond the fact that it was fun for me to do, I had no idea whether anyone else would actually derive any benefit from it at all – let alone my intended audience. I must therefore include as integral to the happy accidents associated with the ‘Physics in the House’ project the fact that it was picked up by the U3A nationally and has been used to spark science-based conversations hundreds of miles from my home base. Moreover, the feedback overall has been a very special part of the happiness with which I now associate the series, including from someone who watched the videos from his hospital bed. (Sadly, a promised call from a local radio station to talk about the series never materialised. It would have been nice to have been able to share the project with a broader audience, but it was not to be.)

In Dan’s case. One might point to his creation of an internet-mediated performance of the first movement of Vivaldi’s Gloria (details here, and on YouTube here). As it happens, a friend of mine was singing in this, so I first heard it at his prompting. Another joyful performance by Dan with another pianist arises from his love of jazz: the two-piano Doxy by Sonny Rollins, here. Thus, despite our ostensibly very different fields of endeavour, the physical sciences and music, Dan and I found that we shared a great deal of recent creative experience. Furthermore, it became clear that for both of us not to try to find a way through the limitations and barriers was simply inconceivable – a fact that emerges clearly, I think, from the podcast.

As the ‘Physics in the House’ project came to its natural end, it occurred to me that I could augment the series by sharing the video recordings of the foundation-level lectures I delivered when still a salaried lecturer. (I have written before about my experiments with lecture recordings, see here) Before I retired, and knowing that all my recordings would be deleted by my university as a matter of course, I made copies of one year’s worth as an archive. With their permission I have now re-purposed that material as a series of more challenging videos which I’ve labelled ‘Physics Beyond the House’. This was all taking place as the initial ‘lockdown’ rules were beginning to be relaxed, so it seemed somehow ‘to fit’. The details are available in the post immediately preceding this one, here.

And it hasn’t stopped. With a friend and former colleague – and local U3A Science Coordinator – Alan Chadwick, I’m helping to set up a science-based open Q&A session via video link. More of that later …

All-in-all, there’s lots to celebrate when it comes to making happy and unexpected discoveries by accident, even in trying times.

* I did ask this question, more than once.

Tuesday, 16 June 2020

Physics Beyond the House

This is a follow-on from my previous post 'Physics in the House', which may be found here. In that post I collated links to a series of relatively brief videos made during the core period of the UK's 'COVID-19 lockdown' and provided a few background notes as well as links to additional material. Here I'm offering another collection of videos on foundational topics in Physics; their content will. however, be a little more challenging ...

It occurred to me whilst filming for 'Physics in the House' that I might re-purpose the video podcasts I created of the 'Foundation Year' lectures* I delivered during the academic year beginning September 2012. I had downloaded these podcasts prior to my retirement as an academic from the University of Kent's School of Physical Sciences simply because I wanted an archive of the material I'd invested a lot in generating (see my blog post here for some insight) and I knew that it would all be deleted automatically. It was vanity of course, as so much is. The material is of no use to my old department now but, although the syllabus, style of delivery and lecturer may change, the fundamentals of Physics do not; I have their permission to make them available to a new set of students. The content is at a level which, roughly speaking, corresponds to the final two years of school education in the UK (so-called 'A'-level). I still have in mind as my target audience the ever-learning members of my local University of the Third Age group, which has a membership numbering well over 1000 - many of whom love learning about topics in science despite being non-scientists (whatever that might mean).

Few projects are straightforward, and this one is no exception. My original plan was to upload the lectures in their original form: raw, unabridged. Unfortunately, I found several podcast video files were corrupted in some way. Thus, the overall continuity of the lectures would have been wrecked from the outset. What I have done in order to mitigate this problem is to extract whatever topics exist in a reasonably 'complete' form within the surviving recorded lectures using a process of 'cut & paste' in the basic video editing package on my PC. Given the imposed necessity of going through my archive more carefully than originally planned I have taken the opportunity of chopping out a lot of 'extraneous' material. For instance, a very significant fraction of the two major lecture courses that I've plundered for these new single-topic videos were given over to working through relevant numerical problems and to discussing the various student-defined issues worthy of in-class discussion. (These discussions, by the way, could take us way off the syllabus - which was no bad thing in my opinion. Very early on in my relationship with each year's new batch of students I'd make it pretty obvious that I was open to being sidetracked: the result, most years, was a rich seem of enthusiasm-building gold! We always got the core material covered; it always seemed to work out.) I have removed all this material. Thus, the sum total of video time remaining is reduced even further. Having said all that, the resultant series is arguably stronger than it would have been had I simply made available the four dozen or so 50-minute lectures I originally intended to share. Each of these topic-centred videos has a running time in the range 12 to 42 minutes, although most fall within the shorter half of that range. The definitive judgement rests with the viewer of course.

Naturally, much of the 'raw' character is retained. You'll see the younger me in good health and poor, occasionally stumbling, wearing thick sweaters during the prolonged period when the lecture theatre heating failed, needing to shout over the sound of hammer drilling, strolling around and waving my hands about, ...  More annoyingly, you'll also see plenty of evidence for the fact that I was still learning about video-recording of lectures, despite having been one of the very first people to adopt the technology at my university: the volume will be excessively soft in some places and I'll wander out of shot now and again whilst be way too close when I happened to cough or need to blow my nose. You get the picture.

Although there was an extensive 'reading list' associated with the original lectures, my two top recommendations both came from the same author: Jim Breithaupt. I'm absolutely certain that there are now more up-to-date editions, but the above are what I used as the primary backup material for the courses. My drawing skills are notoriously poor, so I am particularly grateful for the fact that so much excellent graphical material exists already. The other resources I drew on for the occasional illustration and for ideas for numerical examples include the house magazines of the Institute of Physics and the Royal Society of Chemistry, the science pages of the BBC News web site and whatever other school-level material I could lay my hands on; I think the latter is covered by the image shown below.  In addition, you'll see a small number of animations within the video series; the web sites on which they may be found are of course displayed on the captured PC display, some  of these may not exist anymore - that is the nature of internet material - but a search using the relevant subject matter as keywords will inevitably turn up a satisfactory alternative.

I plan to get all the videos created and then to upload them at a rate of one every day or two: I'll keep this post updated as things progress.

There are two principal strands: 'Matter' and 'Waves & Vibrations'. The outline of their (surviving' content is shown below, including links to the relevant video. I have also included an extract from a short series of lectures given on the topic of laboratory work, which covered what's needed in a formal report (and why) together with an overview of elementary error analysis and why that is so very important. I include in this series only the section on errors/uncertainties since COVID-19 has underlined once again the importance of understanding something of uncertainties in experimental data.

1.   Uncertainties associated with experimental data and results.
Topics in the Physics of Matter:
2.   The Atom: Early beginnings, basic descriptions; the nuclear atom, atomic mass and number.
3.   Avogadro’s number, the mole.
4.   More on the Atom: electrons, isotopes, ions. 
5.   Types of matter: solids, liquids and gases etc., phase changes.
6.   Chemical bonding: covalent, ionic, metallic, van der Waal, hydrogen.
7.   Inter-atomic forces and potential energy.
8.   Electron excitation
9.   Electron energy levels, emission and absorption spectra. 
10. The Bohr model of the atom: energy levels in hydrogen explained.
11. Atomic-scale structure of crystals, polymers and plastics, amorphous materials.
12. X-ray diffraction  
13. Fluids: pressure, Archimedes’ principle, hydrostatics.  Available 8/7/20
14. Heat and temperature scales Available 9/7/20
15. Thermometers: gas, resistance, expansion, thermoelectric, optical; notes on absolute temperature, cosmic radiation background.  Available 10/7/20
16. Thermal conduction  Available 11/7/20
17. Perfect gas laws  Available 13/7/20
18. Kinetic theory of gases  Available 14/7/20
19. Radioactivity: half-life, decay chains, radioactivity in nature.  Available 15/7/20
Topics in the Physics of Waves & Vibrations:
20. Definitions and Terminology: oscillations, waves carry energy, progressive wave.  Available 16/7/20
21. Wave properties-i: wavelets, reflection, refraction.  Available 17/7/20
22. Wave properties-ii: dispersion, diffraction, superposition, interference + earthquakes  Available 18/7/20
23. Wave properties-iii: standing/stationary waves  Available 20/7/20
24. Sound-i: introduction - what are sound waves?  Available 21/7/20
25. Sound-ii: loudness, noise, note, pitch; intensity, intensity level/decibel; ultra-/infra-sound.  Available 22/7/20
26. Sound-iii: reflection, refraction, interference; beats.  Available 23/7/20
27. Sound-iv: vibrating wire (standing waves), standing waves in tubes; Doppler effect.    Available 24/7/20
28. Electromagnetic spectrum-i: Introduction.  Available 25/7/20
29. Electromagnetic spectrum-ii: Generation and detection of EM waves; making an fm aerial.  Available 27/7/20
30. Electromagnetic spectrum-iii: refraction of light, critical angle, optical fibres; polarisation.  Available 28/7/20
31. Electromagnetic spectrum-iv: diffraction; interference, Young's double slit experiment.  Available 29/7/20
32. Electromagnetic spectrum-v: transmission diffraction grating; Michelson interferometer.  Available 30/7/20
33. Simple Harmonic Motion-i: circular motion, link to simple harmonic motion.  Available 31/8/20
34. Simple Harmonic Motion-ii: link between SHM and circular motion, displacement, velocity and acceleration; force acting on a body undergoing SHM, mass on a spring.  Available 1/8/20
35. Simple Harmonic Motion-iii: pendulum, energy in SHM, general expression for SHM.  Available 3/8/20
36. Damping and Resonance: light, heavy and critical damping; natural frequency, resonance.  Available 4/8/20

* I helped to start the Foundation Year programme in Physics more than two decades before I retired. It provided a route into the first year of a 'conventional' Physics degree for those students who, for one reason or another - for instance, having studied subjects at school which didn't include sufficient mathematics - didn't qualify for the more usual direct entry. In short, it provided a 'second chance'; I'm a big fan of second chances in education.

Friday, 10 April 2020

Physics in the House

This is a post I'll be updating a lot (I hope). It's a collation of links to the short(ish) YouTube videos I've decided to try to put together during the COVID-19 lock-down. My primary target audience is the membership of my local U3A branch, but I've made the videos public, so ...

My original intention was to limit each one to ten minutes, but after the first half-dozen it became apparent that I'd never be able to keep to that. I've been told that twenty minutes is too long and I can't help but agree with that feedback. Similarly, I had hoped to avoid all equations but that has not been the case in practice; any that do crop up are very short. (I ought to add that there are also some maths. expressions appearing such as squares and square roots.) As if those failings aren't enough, I have spotted a few errors (none of which are too horrendous, and I correct most using captions within the videos themselves). My apologies to you, on all counts; I will try to do better.

The setup is very basic, as the stills included below will illustrate. The webcam is about a decade old, and my laptop isn't much younger. It's the same story with recording and editing software: I am using only the 'free' apps bundled within Windows-10 and those supplied as default with my smartphone. However, none of those facts provide an excuse for any poor content to the videos themselves or for my choice of topics - that's down to me.

1. Introduction.
2 minutes
My recording studio: a corner of my study, augmented with a 'camera gantry' made from a length of scrap timber G-clamped to a bookshelf. The A3 watercolour pad is so ancient that it's of little use  to my artistic wife, but it does well enough when used with a thick felt-tip pen; I'll replace it with a whiteboard as soon as I am able. In order to get my decade-old webcam close enough to the writing surface I have to slide myself under the makeshift gantry and wriggle into position in the small armchair. When the paper runs out I may have to treat myself to a small whiteboard ...

2. The Spin Cycle: what can we learn about the universe around us from our washing machine?
14 minutes

Watching the spin cycle is not terribly gripping, but I edited the clip down to a few tens of seconds in its final phase. Illumination (here and in other clips) was provided by a small LED torch - in this case it's suspend from the shoe rack to the left of the image.

3. Boiling Water: the sounds associated with boiling a kettle of water and where they originate.
27 minutes - ouch!
After a lot of trial and error (a lot!) I found that I could get a reasonable view of the kettle's insides by raising it on cork mats and hanging the webcam from the kitchen towel holder. I could illuminate the kettle by shining my LED torch through the water-level sight glass; it clatters off it's perch during one of the clips you'll see - I ended up propping it us inside a coffee cup. Sitting my laptop on the cooker hob didn't exactly represent best-practice, but it served its purpose. To reduce the issue of steaming up the webcam I had to fan vigorously ... using a magazine that happened to be nearby.

4. Water in Heating Systems: why is water such a good material within our central heating systems?
11 minutes
There's not much one can film when discussing a central heating system, so I chose to prop myself up next to a radiator and mount the webcam on an old camera tripod. At least the tripod made panning easier, but my arm did ache a little from the effort of holding up the A3 pad I was writing on.

5. Convection: from ice in warm water to the Sun.
17 minutes
Backlit in the morning light, diffused through some light curtains and propped up on a couple of books - high-tech all the way. During the phase of my career when I was visiting Grenoble (southern France, their 'Silicon Valley') for a week at a time to conduct one experiment or another I learnt a useful term for such set-ups: bricolage. I'm getting the hang of the video editing software bundled with Windows-10 at least.

6. Standing Waves: how the principle of superposition leads to standing waves and gives us music.
18 minutes
I'm no musician, but I can at least pluck a guitar string. There are two things to note in terms of getting things to work for this video: a) the trivial point that I now have a lap-sized whiteboard which ought to improve the clarity of my 'artwork' a little (powerpoint was invented for people with my drawing skills!), and b) the sneaky use of a bright LED bulb in my tiny utility room as a sort of strobe light (mains-powered LEDs actually switch from full intensity to completely off with the frequency of the mains - actually, twice each cycle, so twice 50 Hz = 100 Hz).

7. Visible and not-so-visible light: prisms, CDs and a drop of water lead into an exploration of the electromagnetic spectrum and the phenomenon of refraction.
17 minutes
Two of the props employed in this video: a plastic hypodermic taped to the top of my staircase, from which hangs a single drop of water, and a humble CD. There are a few posts on my blog of direct relevance to the material covered here - take a look if you'd like more information on colour, rainbows etc. Two of the most relevance may be found here:
Rainbows    Colour
You might also like to take a peek at a blog post written by a fellow physicist who's posts I make a point of reading: Bean thinking: Where entertaining science meets good coffee

8. The Swing of a Pendulum: how to explain it using the rotation of a record deck and then use it in order to measure the strength of gravitational attraction at the Earth’s surface.
17 minutes
Capturing the behaviour of our two wall clocks – both bought at small local auctions and then brought back into full working order – and a 200-year old locally made long-case clock was relatively easy, although the long-case clock required the webcam to be in portrait mode. Fabricating the 0.81 m pendulum and mounting it above my old vinyl record deck was more of a challenge.

9)  Crystal structures: taking a peek inside a few household materials to see how their constituent atoms are arranged.
14 minutes
I tried a slightly different setup this time, with the webcam looking past me to my desk. Apart from offering something slightly different for people to look at, it enabled me to have a few items of show-and-tell within easy reach. Spot the astronomy-based wallpaper on my PC screen - most of what's there at present comes from the Hubble Telescope, but I already have two of my own images in the folder and hope to add more in due course.

10) Interatomic Forces: using a simple elastic band to try to understand the key forces that hold materials together and control their properties and behaviour.
14 minutes
There have already been examples of the use of scraps of this and that employed in this series of videos but this setup is arguably the most ‘Heath-Robinson’ yet. Duct tape, a jar lid and a map pin get folded into this particular scientific instrument, along with an elastic band and a set of weights from an old, but still used, kitchen scale. It was all suspended from my 'camera boom', itself G-clamped to a bookcase shelf.
We can demonstrate Hooke’s Law and thereby to show that the bonds between atoms (and between molecules) behave as though they had the properties of a spring.
Although I decided not to spend time on it here, we could have set the weighted elastic band oscillating up and down; we could do the same with a suitable spring. Believe it or not, the maths. associated with that motion can be approached in the same way we did for the oscillation of a pendulum: we can 'recycle' the maths. describing uniform motion in a circle. Generically, we're in a favourite physicist's haunt called Simple Harmonic Motion. SHM informs much of our understanding about the motion of atoms within materials.

11) Estimating the Speed of Light using chocolate digestive biscuits (plain chocolate, naturally) and an old microwave oven.
17 minutes.
You may find it helpful to watch videos 6 and 7 before looking at this one; if you're OK with what the electromagnetic (em) spectrum is and what a standing wave is then do feel free to skip this step.
This is a demonstration experiment I had planned for the Canterbury U3A 2020 Open Day, but the whole event fell foul of the COVID-19 situation and was cancelled. I've slimmed it all down for this video taster. A notable change is that I would have done the experiment with chocolate buttons as originally conceived, but such non-essentials of life became very hard to come by and I resorted to the sacrifice of a pack of chocolate digestive biscuits instead. This has two major disadvantages: the chocolate softens quicker and makes it that much harder to get the times right, and the larger circles gives me a coarser surface coverage and also happen to have a diameter which is approximately the same as the distances I'm trying to measure. This second issue is the more serious of the two since it means that it's quite possible to miss one feature altogether: I know because that's exactly what happened. Thankfully, a more observant physicist who watched the first version of the video via a link I put onto Twitter sent me back to the proverbial drawing board and I tracked down the problem; thank you
(The microwave oven itself was bought for next-to-nothing on eBay - it had dents and other marks all over the casing but the safety shielding was intact and it worked just fine.)

12) Microwave Ovens: what not to place inside them.
14 minutes.
Whilst I had my ‘disposable’ microwave oven already set up for Video (11) it seemed a good idea to use it for a second ‘fun’ demonstration. I’m always a little wary of telling people what not to do, but I hope that by actually explaining why something is not a good idea the message will come across in a more positive way. Please keep in mind that, although amazingly useful, microwaves have potential hazards associated with them if abused. In this case I was aware of precisely what might happen having seen the consequences of abuse in the past: I chose a single controllable demonstration and took appropriate precautions.

13) The Sun: what can we learn from our nearest star?
14 minutes
The image above shows my webcam with the lens covered by a solar observation film which removes 99.999% of the incoming light - if these are the sorts of precautions one must take in order to avoid damaging equipment then just imagine how much more important it is to protect your eyes from damage. OK, warning over. This video looks at what physics we might learn from observing the Sun. There's a passing reference to convection currents (see Video 5 in this series), and my earlier post on the Earth includes the following: "The Sun, which represents 99.9% of all the mass in the Solar system, is a ‘middle-aged main sequence’ star which means that it’s been stable for about 4 Gy – lots of time for life to develop. It resides in what we might term a ‘quiet suburb’ of our galaxy; we have no black holes or analogous threats in our neighbourhood, which is good. Our nearest neighbour galaxy, Andromeda (M31 in the formal catalogues) is actually heading towards the Milky Way at over 400,000 km/h – but because it’s 2½ million lightyears away we still have several billion years before it arrives."

18 minutes
Smoke detectors save lives - that makes them an example of a positive use for radioactive materials. In this video we'll take a look at how a domestic smoke detector works, and why one particular radioactive isotope is absolutely vital for this technology's operation. Of direct relevance is the blog post that emerged from my first Canterbury U3A session on radiation, which has now run a total of three times (I think) to progressively larger groups of members. (I confess that I was tempted to show you inside the ionisation chamber at the heart of this device, but I stopped short of that because I didn't want anyone thinking that it was a trivial thing to dissect the device.)

15) The Sound of Glass: what can it tell us about the arrangement of atoms within the material?
17 minutes 
If you run a search within this blog using the word "glass" there'll be many returns: I find glass an almost endlessly fascinating material. No surprise then that, for several years, I led a three-session series on the science and art of glass within Canterbury's U3A; it's 'resting' at present whilst I have been developing and running sessions on different topics within the physical sciences. If you prefer to watch a longer video in order to get more background invitation then there is an extended video on YouTube of a talk I gave many years ago at the Canterbury Heritage Museum:
Although of no direct relevance, you may have noticed the image of the crescent Moon on my PC screen in the background during parts of Video 15. It's actually a composite of five separate images taken through my telescope sometime in April 2020. Did you know that there is a lot of glassy material on the Moon's surface and that this explains why it is so bright in our skies?

16) The Colours of the Sky: a spoonful of milk can illustrate more than you might think.
14 minutes
So many others have tackled this topic - I make no claims for originality - but I could hardly omit from our series a topic of such everyday importance as the blues and reds of our amazing sky. You might like to take a look at Video 7 in the series if you've not already watched it since it will give you an overview of where the colours we can perceive sit within the much wider electromagnetic spectrum. Also, there's a really elegant video demonstration of the same phenomena I'm attempting to illustrate here on the excellent Facebook feed of 'Thinking Bean'. The specific link is here
By the way, please forgive the untidiness of my garage ...
17) Refraction: why do the incoming waves curve near 'The Street' at Whitstable, and is it true that sound carries further at night?
16 minutes
In Video 7 we looked at the refraction of light through a prism and through a droplet of water, but in this video we'll take a look at one local manifestation of the principle ('The Street', a spit of land at right angles to the coastline at Tankerton/Whitstable) and one that we all might test out (why sound carries further at nighttime). There are many, many other examples of refraction in our everyday lives: our spectacles/contact lenses rely on it for instance, as do the lenses in our eyes. I'll leave you to explore: there's so much physics waiting to be found, even in our homes.
In the process of understanding these phenomena we'll get to something usually labelled in textbooks as 'Snell's Law', but ought Willebrord Snel van Royen be given this honour? For further reading on topics of this sort, i.e.  within the history of science, I recommend two expert and very readable bloggers: Rebekah Higgitt, who writes here and Thony Christie, whose blog is here. (Becky is a former colleague, having taken up an academic post after holding a senior position at the National Maritime Museum at Greenwich - we were both closely involved with our university's 'science communication/public engagement' activities.)
18) Diffraction: using a laser pointer, a perspex ruler and the spring from a biro we'll explore a method whereby physicists (and indeed a very wide range of scientists and engineers) determine the exact arrangement of atoms in a crystal.
18 minutes
I have been told that the sound level in this video is relatively low when viewed on a smartphone. I'm sorry about this.
In Video 9 of our series we looked at crystal structures - the arrangement of atoms in everyday materials like table salt, aluminium, etc. - but how are these atomic-scale structures determined?  One of the most powerful methods is diffraction, which is what we focus on here. The majority of diffraction experiments rely upon a bright source of x-rays, which are an energetic, short-wavelength form of light (see Video  7) but we can use other probes as well such a neutrons or electrons - both of which are commonly thought of as particles, but which can behave in a wave-like manner just like x-rays. In this video we'll illustrate the diffraction method using 'scaled-up' analogues. (The COVID-19 virus has been studied using the methods illustrated here.)
One thing I simply forgot to talk about in the context of my illustration of diffraction from DNA using a helix in the form of a metal spring, is the significance of the angle of the 'X' we observed in the pattern. Just as the spacing between markings on my perspex ruler determined the spacing between the bright patches of scattered light we saw on the graph paper - the more widely spaced the markings, the closer the patches of scattered light - so the angle between the lines of the cross is determined by the pitch of the helical spring. The point being that diffraction not only gives us information on the spacing between atoms but also, in the case of molecules such as DNA, offers us an insight into the overall shape of the molecule's structure - the pitch of the helix in DNA's case. A copy of Rosalind Franklin's original x-ray diffraction image from DNA, recorded on photographic film, is shown above on the right; note the 'X' shape. (Image taken from - accessed 23/5/20).
19) The Galileo Thermometer: using buoyancy to measure temperature.
14 minutes
Galileo thermometers are available in all sorts of styles and sizes (and with associated costs); this one was a gift and has graced our dining room for many years. The chap depicted in the background is supposed to be Galileo Galilei himself. I hope the video explains how it works well enough, despite my evident failure correctly to spell 'buoyancy'.
20) The Siphon: a little gravity-driven physics in your WC.
20 minutes
How could we leave the topic of 'Physics in the House' without flushing out the secrets of the WC: what happens when the lever is twisted, and more importantly, why? There have been all sorts of things written about its workings, from suggesting that, once started, the falling water 'pulls' the water behind it through to the supposed driving force of atmospheric pressure. We'll see that all we really need is gravity. 
I've tacked on about five minutes on the topic of atmospheric pressure by the way. The topic caught my eye as I was researching the operation of siphons in toilets and doesn't really warrant a whole video to itself - especially in a series under the heading 'in the house'. Having said that, it's a fascinating story in science, with lots of intriguing history, so you might want to do a little reading yourself.
21)  Why is Glass Transparent - or is it?
20 minutes
My blog is replete with posts on glass: some tackling aspects of the science of the material head-on and some taking a more oblique path. It will be obvious to anyone scanning my writing that this is a material that fascinates me more than any other as a scientist. If you've had the misfortune to sit through one of my multitude of talks on the science and art of glass you'll know that my passion knows no bounds and that, as a consequence, I sometimes stretch the limits of my allotted time-slot. The final two decades of my research career were dominated by chasing its secrets into some exciting new avenues (e.g. bio-active glasses for bone regeneration and for drug delivery). It is perhaps fitting, then, that I draw the 'Physics in the House' series to a close with a video related to 'everyday' glass.

An introductory video and then twenty science-based studies derived from things in/around the house (well, my house) meets the target I set myself at the outset. Five and a half hours in total: that's getting on for the aggregated total of face-to-face time I would normally spend each year leading Canterbury U3A groups. Now that 'lockdown' is dissipating it is perhaps time to draw a line under the project; in truth, I have covered most of the topics on my original list of ideas - and a few more besides. 

However, before I sign off I'll mention a full-length recording of a talk on glass I delivered to an audience in Canterbury's former Heritage Museum way back in 2012. I have been 'resting' my three-session glass science & art U3A course for a couple of years as so many of the membership have already participated. If anyone would like to see a slightly outdated summary then do watch 'Glass: a look inside'.

Physics Beyond the House
Also, I plan to add to 'Physics in the House' a new series of videos. Way back, when I was still reaching Physics as a university academic, I taught courses for Foundation Year students - those who, for one reason or another, wouldn't get a place in the first year of a conventional Physics degree programme without spending time being brought up to speed. (For example, some of the intrinsically bright students on the course will have taken the wrong mix of subjects in their final years at school for a Physics degree.) The course content was, therefore, roughly at the equivalent level to the UK 'A'-level. I was an early adopter of recording technology for lectures (see my blog post 'Flipping Lectures') - one result of which is a library of lectures I have as video podcasts, archived from one particular academic year.  STOP PRESS: see the following blog post for details, here.

Tuesday, 11 February 2020

One click away: scientists I never met

A ‘random’ thought popped into my head recently, probably as a result of something I’d seen or a word or phrase used in conversation, I no longer remember: were there any famous scientists I might have met but didn’t, or perhaps ‘knew’ only once-removed? It used to be said that no-one on the planet is more than six handshakes away (if one shakes the correct hands in the correct sequence presumably); the internet is somewhat more complex, with trillions of pages rather than billions of people. Even there, it seems that no two pages are separated by more than nineteen clicks (see here). Are there people who, though I’ve not actually met them, are only one click/handshake away? One example stands out in my mind …
Way back in 2013 I photographed this from a train as it drew to a stop at Didcot Parkway station (- a station I have used more often than would be possible to number; I lived in Didcot for a season but also travelled there throughout most of my professional career in order to use the world-class research facilities nestled in the Oxfordshire/Berkshire Downs nearby). In passing, it was this shot that set the record for the number of people who were reached by a single tweet from my account; it’s all been downhill since then ;-)

My wife and I were married in the late 1970s in the midst of a second summer of drought. The ceremony took place in a small rural church in the village she’d grown up in, and which was led by the vicar she’d known all her life. I liked Rev. Graham Brade-Birks, or B-B to his friends and familiars. He was a kindly, quick-witted man who, to my naïve twenty-something mind, seemed far too old still to be gallivanting around as a parish priest. (In fact, as I later discovered, he was in his eighties – although you’d be hard pushed to know it.) I was invited to visit him in the vicarage for a pre-wedding pep talk, although we had already enjoyed a great many conversations in the months before the wedding, and more in the period following. This was a vicarage of the sort you’d not find these days: a large, rambling old house with views across the garden to the river Stour, and a study to dream of – built at the top of a spiral staircase in a near-circular tower at one end of the house. It had the less desirable characteristic of being sited only just above the river’s flood plain, devoid of either proper damp-proofing or effective heating; he used to hang hot-water bottles under his outer clothing in order to keep warm. (The house was sold when he finally stepped down and is now almost unrecognisable as a £million+ private property.)

During one of our conversations, which often drifted into topics in science, he astounded me by recounting the story of when, in pre-WW1 Manchester, he mended the car of someone he used to see around about the university campus: J.J. Thompson. For those readers not familiar with the pantheon of ‘science greats’, J.J. Thompson is the person credited with discovering the electron. In other words, he identified the very first sub-atomic particle and thereby changed the face of Physics. Moreover, it was his work and direct influence that sent Earnest Rutherford along the pathway that led to his own seminal work on ‘splitting the atom’ – the centenary of which was celebrated in 2011. So there I was, in free-flowing conversation with someone who actually knew one of the greats. As time passed it began to dawn on me that Brade-Birks himself knew and understood a lot about a lot. In fact, I dare to say that he was the first genuine polymath I had ever met; it’s a mind-set I’ve always aspired to achieve. He graduated in Geology (with a subsidiary in Zoology); with his wife he became an expert in the study of centipedes and millipedes (aka myriapods – they added eight new species to the lexicon and published a couple of dozen papers, see here for additional details), and whilst a lecturer at a local agricultural college – how did he fit this in with being a vicar? – he wrote books on soil science and archaeology. He spoke and wrote on local history and even made a contribution to the biographical study of Jane Austen, whose brother had lived in his parish.  
The penny didn’t drop for years, but I now take great pleasure in the fact that I had selected one of his books as a prize from my school. I was 13 at the time, so this was many years before I met him; I had evidently already developed my abiding interest in archaeology (see my earlier post, here). For those not familiar with pre-decimal UK coinage, 7/6 – seven shillings and sixpence, or more usually ‘seven and six’ – would now be rendered as 37½p. (Within three years I had found myself a Saturday job clearing tables and washing up: 7/6 was equal to my pay for 2½ hours.) The signature shown is that of my most excellent school head teacher; I mentioned him in an earlier post, here. (In passing, Rev. Brade-Birks’ original surname was Birks. When they married in 1916, he and his wife decided to amalgamate their surnames. I have found several mentions online: e.g. here and here)

It’s time to change the subject, although the longer I spend drafting this post, the more people I remember who deserve a mention. Doing so would, however, be to drift from my core topic – and to render the post unreadably long; a cardinal sin. I’ll therefore conclude with a couple of short stories instead. The first of these concerns two visits to Glasgow University’s Physics Department at the invitation of Prof. Sheila Rowan. Sheila and I had met whilst serving as members of the Science Board of the Science & Technology Facilities Research Council (I’ve written about this work here). My first visit involved delivering a talk on bioactive glass (see here) and having the opportunity to learn about the work of the Gravitational Waves group that Sheila led; my second was as examiner for the PhD student who’d taken a lead in perfecting the glass mirror at the very heart of their gravity wave detector. Why mention this? Well, because their equipment played its crucial role in the first ever detection of a gravity wave – as predicted decades ago within Einstein’s General Theory of Relativity. (see here; also, this video may help) I had been ‘one click’ away from a Nobel prize-winning discovery. Although Sheila and I haven’t met again since our period of service with the STFC concluded, I was exceptionally pleased to see her later appointed to the office of Chief Scientific Adviser for Scotland

This happy fact provides for me a perfect segue into a couple of examples of my encounters with the ‘science-adjacent’ movers-and-shakers of their day: the politicians with responsibility in the area. Take for example the meeting set up by my then local MP and the Higher Education minister, Boris Johnson. How interesting it would now be to offer my personal recollections of the man currently our Prime Minister, but no … he cancelled at the last minute. Never mind, I had a fascinating evening eating dinner with a small group of MPs and one other academic, sharing with them whatever insights I had regarding university teaching and research in the sciences. More satisfying, and amusing, by far was opportunity to discuss such matters with David Sainsbury, Baron Sainsbury of Turville, when he was Minister for Science and Innovation (1998 – 2006). He visited the department I was at the time leading (here) and we spent an hour or so talking over tea and biscuits; no cameras, no up-staging by my university superiors: at his request this was a very low-key affair. This was my brush with science policy-making at the highest levels – still one click away in truth, if not more. When it came time for him to leave I walked him to the designated car park rendezvous, but neither chauffeur nor car were anywhere to be seen. Our campus security eventually people found him: parked and fast asleep in a particularly quiet corner of the campus. I’ve no idea what the upshot of that faux par was; it would be nice to think that it became a source of light-hearted humour …

As with my example of Rev. Brade-Birks, I suspect we could all recount a brush with the stars of our particular firmament, even if they’re once-removed. We all of us have great value however, simply by being who we are; I’ve no experience of being famous, even within my small cluster, but I suspect it’s less desirable than it sometimes seems. For my part, I had an amazing career. It is tempting to say that it was guided by serendipity and fueled by the ever-present struggle to hide or disguise failure; in truth there were also other forces at play. I’ve written about my life as a scientist throughout this blog, often obliquely, sometimes more directly (as here). I met some amazing people during this long phase of my life: hugely talented and creative individuals with the ability to bring the very best out of those around them. Some, I am glad to say, were also people of warmth and compassionate generosity (e.g. here); others were not. I have tried to learn from them all – in the latter case, in terms of what not to do.

P.s. My original working title for this post was ‘One click away: scientists I never met and things I never did’. It is evident that I dropped any attempt to reflect on the latter phrase in my subsequent musings. I may return to the topic one day; I have long come to terms with the fact that I tend to disqualify myself by default. As a consequence I have eschewed all kinds of opportunities which, were I a person of different makeup, I might have enjoyed immensely. C’est la vie

P.p.s. I shan’t be able to beat J.J. Thompson as my best ‘one click away’ story. I’ve written relatively little about my old university department (e.g. here) but it deserves a mention within the broader scope of this post. When I was appointed it was a cause of celebration in the department: not because of me but because a very long hiatus had last been ended as university posts were ‘released’ through a government funding initiative to get some ‘new blood’ into an ageing population of UK academics. My appointment to what had been my ‘dream’ job for many years was life-changing, as one might expect, but once the dust had settled a little and I began to take stock something else dawned on me. I had joined one of the ‘plate glass’ universities created in the expansion of the 1960s and I was, de facto, working alongside people who had built the place from scratch. They had welcomed the first students and begun to guide them through a syllabus put together not long before their arrival and using teaching methods and laboratory set-ups designed between them. I was, in a sense, one click away from the birth of a university and its constituent courses. I have to say that I found it rather poignant when the last of that generation of academic and technical pioneers retired. Amongst them were those present at the birth of NMR as a tool for imaging, and of the large-scale scientific use of neutrons and synchrotron x-rays; all of them had their own stories to tell. 

Tuesday, 14 January 2020

Messing around with Sound

In fairness to you dear reader, I ought to open with a confession: this post contains many more words than I’d usually aim for. In order to mitigate this I have moved several hundred words to an [endnotes] section so you only need read them if you’d like a little more detail/information. I’ve told myself that it may prove useful for anyone else thinking of giving a talk to a lay audience on the same topic; who knows. In addition there are, sadly, few pretty pictures to soften the blow, but I have added lots of links to animations and the like …

For the first three years of my retirement – from academic life that is, I was a scientist before that, and I still am – I led three two-hour sessions, one per week, on the art and science of glass for my local University of the Third Age (U3A) branch. (It has over 1000 members, making it one of the larger branches on the UK scene; the web site is here to which I contribute the odd snippet now and again, here.) It was huge fun, due in no small part to my audiences of smart and careful listeners. In the process, I got the opportunity to develop further whatever skills I had in conveying aspects of science without the use of mathematics. However, after the 2018/19 season I decided to set this material to one side for a while. We all need new challenges from time to time, when the old must make way for the new. I had by this time developed a session on the topic of ‘Radiation’. This was a start, but my plan, such as it was, involved introducing new topics on a rolling basis. Accordingly, in the following year, I successfully trialled a session which explored the question: ‘What’s so special about the Earth?’. After that – and we’re now into the current, 2019/20, season – came sessions on ‘Colour’ and on ‘Sound’. Where I go from here is undecided [i], although it’s definitely time to lay ‘Radiation’ to one side for a while as everyone who wants to learn something under this heading has by now been able to. (I know this because, unlike my other sessions, there wasn’t a waiting list of ‘reserves’ hoping to get a seat on the basis of a last-minute drop-out.)

All of this is but a preamble to the central reason for writing a blog post after a relatively long hiatus. Put simply, I promised to draft something on the topic of ‘Sound’ [ii] in the hope that it would act as a sort of memento for those brave souls who risked contracting my cold virus in order to participate in the session on January 7th. (And participate they did by the way: every bit as sharp-witted and engaged as any other U3A group I’ve encountered, and with a great sense of humour – more of that later …) 
As a bit of fun, whilst I was busying myself setting out the various bits of kit I’d borrowed [iii] for the event, I projected onto a large TV monitor the live ‘oscilloscope’ trace [iv] of the sounds present in the venue as people arrived and settled down to chat to each other. It was fun to see the realisation dawn that it was they who were creating the changing ‘squiggles’ on the screen. (The screenshot shown in the figure above was not captured at the time but specifically for this post – it’s derived from a piece of music I played for the purpose – but the principle holds.) This pre-session bit of ‘show and tell’, which I explained to everyone later on, worked particularly well because we were in a relatively small room with hard walls and large windows bouncing the sound around. Unfortunately, this would make life less easy for later demonstration experiments. A partial solution involved dropping the wood-slatted venetian window blinds and angling the slats in the hope that any echoes would be broken up a little. It worked tolerably well. Even with the same slides and associated ‘show & tell’ kit, no two talks are ever the same; it’s part of the fun of the whole process.

Sound was of course listed in the relatively short Science section of our U3A programme of events for the year – science-related topics represent about 10% of the total – so we started with a bit of basic terminology and a few definitions in order to get the ball rolling. A key concept was that of an oscillation: a repeated to and fro motion. All waves are oscillations. (Hence, a ‘Mexican wave’ is not actually a wave at all – it’s a pulse.) Having got that under our belts it was possible to focus on sound waves and to illustrate what was going on by considering the to and fro motion of air molecules in front of a loudspeaker cone. As the cone moves forwards it compresses the air in front of it (i.e. increases the pressure) and as it moves back again it causes the air pressure near it to decrease; the air molecules are oscillating backwards and forwards. In colliding with the next layer of air molecules this oscillation is propagated outwards; all the while, individual air molecules are simply oscillating forward and backward, forward and backward. The animation shown here illustrates the behaviour quite well. Of course, sound travels in liquids and solids as well; the same generic principles pertain, but the atoms/molecules are closer together and tend to be bonded to one another far more strongly than is the case for air molecules. The speed of sound in dry air at 20ºC is 343 m/s (at 0ºC this drops to 331 m/s [v]; humidity also has a significant effect) but in helium gas it’s a whopping 965 m/s, which is why one’s voice sounds high-pitched after inhaling helium. The speed goes up again in water (for seawater it’s about 1522 m/s) and leaps up again in solids to several thousands of metres per second. As a passing observation, the variation in the speed of sound through different materials is what enables geologists and geophysicists to use the technique of seismology to such good effect – but to explore that would require another blog post.

We looked at what was meant by sound frequency – the note or pitch – and then at the difference between intensity and loudness, the latter being the subjective response of our ears and brain to changes in the intensity of sound waves arriving at our eardrums. This enabled us to get to grips with the oft-quoted unit of the decibel as a measure of loudness. It was also a great point at which to reflect on what an amazing instrument the ear actually is: capable of detecting frequencies from a few tens of oscillations per second (one oscillation/s is called a Hertz, Hz) to around 18,000 Hz, and able to do so over twelve orders of magnitude in intensity [vi]. Interestingly, a baby’s cry is at a higher frequency than an adult’s, about 500 Hz compared to ~350 Hz, which corresponds much more closely to the frequency range at which an adult’s hearing is most sensitive. The obvious experiment was to use one of my borrowed signal generators to send sound waves of a particular frequency from a loudspeaker and to vary the frequency in order to determine the range enjoyed by those present. No-one got much below 40 Hz or, with a couple of exceptions, higher than about 14,000 Hz; our ears degrade with age.

There are sounds we will never hear of course. At high (ultrasonic) frequencies we know that bats are able to echo-locate their food, and in the medical world we design instruments to image parts of the body, break up unwanted lumps and so on. At the other end of the scale, low (infrasonic) frequencies are associated with elephant and whale calls as well as with the blades of wind power turbines. There are occasions when the frequency (or equivalently the note or pitch) of a sound seems to change all by itself. It’s most obvious when an emergency vehicle is travelling towards you and then passes by and travels away: the frequency seems higher on its approach and then drops as it travels away. This is an example of the Doppler Effect (see animation here). It was demonstrated in a simple but quite dramatic way by fixing a small speaker (from a printed circuit board) to a battery via a switch and twirling the whole thing above my head in a circle. The frequency (pitch) of the sound as heard by my lovely audience increased or decreased depending on whether the source was approaching or receding from them.

Our next keyword was ‘superposition’. Although an extremely important principle across Physics, it has particular ramifications in the context of sound waves. Basically, we can think of overlapping sound waves as adding together in a very simplistic manner: if an increased pressure bit of one overlaps an increased pressure bit of another, the result will be an even higher pressure; if an increased pressure section of the wave were to overlap with a reduced pressure section of another however, they would tend to cancel one another out. This may be illustrated in practice in several ways, but I started with beats. This occurs when we hear two sound waves which differ slightly in terms of frequency – usually by less than 10 Hz: we end up hearing only one frequency, which is the average of the two, and its intensity goes up and down. Twin-propeller aircraft are famous for giving rise to this effect. In our case, I was able to demonstrate the effect by running two loudspeakers from separate signal generators and then slowly varying the frequency of one of them so that it approached and went past the frequency of the other. This set of animations may help.

We then came to a really fun bit, when I got everyone to stick a finger in one ear, stand up, bob down and move around the room. It was quite a sight. We were talking about the creation of an interference pattern using my two loudspeakers, but this time powered from a single signal generator to ensure that they were perfectly matched. It’s a tricky concept, but this animation reveals the essence of what we created, in 3D, using two sound waves. What we established was a stable room-filling pattern of high and low intensity sound through which we might move. I chose a frequency in the region of 1500 Hz for this simply because I knew it would provide a pattern spacing of less than half a metre. Why the need to block one ear (or remove one hearing aid in a couple of cases)? So that we could explore the sound interference pattern without the confusion of having two ‘detectors’, our ears, send separate signals to our brains. After a few minutes of fun, and a bit of discussion on whether one could navigate around the room by counting the number of high/low intensity regions we had moved through, I asked everyone to park themselves at a low intensity point. If we were experiencing what I had told everyone we were, then by unplugging one of the loudspeakers the sound intensity at their ear – their sound detection device – ought to go up. Thankfully, everyone was able to confirm to me that it did. 

Resonance was to be my final topic. Although we were able to cover the basics – the necessity to ‘drive’ the system at its natural frequency – we ran out of time before I could set up the coup de grace: smashing a wine glass using only sound. My laptop’s soundcard scope came to fore again in that I could at least show everyone how to find the natural/resonant frequency of a wine glass simply by flicking its edge with a fingernail. The screenshot of one I had tried at home is shown above: the glass rings at a particular frequency/note. In this case – indeed, for all the odd wine glasses I possessed – the natural, or resonant frequency was in the region 870 Hz. Subject the glass to a high enough intensity of sound at that same frequency will cause it to vibrate more and more … until it breaks. This video shows precisely the arrangement I had intended to use.

From the questions posed at the time and from subsequent kind and generous feedback I’m clear that were there more time, those present would also have enjoyed to hear about why musical instruments sound so different even whilst playing the same note, including what makes a standing wave. Perhaps next time. All I could leave them with as our session came to its end was a warning and a piece of prose:
  • beware sounds at 5-7 Hz as this corresponds to the resonant frequency of our body’s water-filled cavities (- an important consideration when designing car suspension systems, and otherwise) and
  • enjoy George Eliot’s appreciation of resonance: “How will you know the pitch of that great bell too large for you to stir? Let but a flute play ’neath the fine-mixed metal: listen close ’till the right note flows forth, a silvery rill: then shall the huge bell tremble – then the mass with myriad waves concurrent shall respond in low soft unison.” (Middlemarch, OUP, Oxford).

[i]  Is there scope for something on waves, or on quantum mechanics? What about an open Q&A session: could I pull together a sufficiently multi-disciplinary team who would volunteer to join me in the ‘bull pit’, and would there be an audience? Ought I to step sideways out of the U3A and into something qualitatively new? There are lots of possibilities, but as yet no decisions. 

[ii]  Indeed, there are blog posts on each of the topics I’ve covered within the U3A thus far with the sole exception of ‘Sound’, so it’s surely got to happen. Existing posts may be found by clicking on the following links: Radiation (here), Earth (here), Colour (here and links therein); Glass is at the heart of half the posts on my blog, so take you pick (e.g. here or here; or if you’d like to peek into my professional interests in glassy materials, try here). 

[iii] I am immensely grateful to my old department (The School of Physical Sciences, University of Kent) for their continued support in my science communication endeavours, and in particular to ex-colleagues Dr. Dave Pickup and Dr. Vicky Mason. I made sure to acknowledge this support in my talk, as is my habit whenever I use borrowed items for ‘show-and-tell’. 

[iv]  I used a piece of software which is freely available to download for use within non-commercial/educational contexts (here). It uses the laptop’s soundcard, so it does have limitations of course; however, it is extremely useful for talks such as this one.

[v]  I’ll not cover it here, but this is the reason why sound carries further at night. The cooler air near the ground has the effect of refracting (bending) the sound waves downward – thus, the sound wave’s energy is not dissipated up into the atmosphere quite so much. In the daytime, when the air near the sun-bathed ground is warmer, the waves are bent upward and thus away.

[vi]  From 1 W/m² to 1 pW/m² where W, the Watt, is a measure of the wave’s energy and a picoWatt is one million millionth of a Watt. For context/comparison: the heat output from a single adult is in the region of 100 W; a domestic electric kettle typically consumes power at a rate of 2,000-3,000 W. The ear is thus a very sensitive wave detector.