Experimenting within the Third Age: ‘flipped lectures’

 

Four years BP (Before Pandemic) and soon enough after retirement that I could still remember the details of my life in salaried work, I wrote about some of the ‘experiments’ in education I was fortunate enough to be able to pursue (see here for example, final couple of paragraphs). I find that I am still succumbing to this weakness for trying new approaches in science communication. My intended audience is now the membership of the local branch of the University of theThird Age, U3A , rather than undergraduate students, but the passion to share my love of the life scientific remains the same. This post will offer, I hope, a preliminary reflection on a new take on an old theme. The rich vein of serendipity evident to me throughout will also emerge if I can string the right words together.

Cartoon by Jon Butterworth - used with permission.

Although my first 2020 ‘lockdown’ project was actually fairly conventional in many ways – a vaguely straightforward presentation of some basic Physics, albeit tied to objects one might very well find in the home – it did expand my experience of video creation/editing and the use of YouTube. I also learnt how to perch a small whiteboard on the lap and keep it level and in the frame without getting muscle pain and how simultaneously to control a handful of coloured marker pens as they attempted an escape. Such were the skills associated with 2020. A previous blog post provided an overview to the videos and formed, in essence, a Contents Page for the series (you will find it here). Curiously, given the crudity of the setup and my naïvety as a speaker-to-camera (I generally prefer to be behind the lens) this initial blog post has become the most viewed of them all. Having got to the end of my imagination, or perhaps simply my energy – it’s hard to say when in the midst of the stresses and strains of pandemic life – I turned to something more prosaic: making the few surviving recordings of my pre-retirement lectures available via YouTube (see here for details). The potential audience for this particular video series was never going to be large.

In early summer the call came for ideas and proposals for the approaching 2020/21 U3A Autumn & Spring Programme, none of which would take place face-to-face of course. Whilst everyone had ‘made do’, after a fashion, when the pandemic’s grip had first been felt and the second half of 2019/20’s programme had to be cancelled, actually starting a new year without even the remotest possibility of face-to-face meetings seemed worse somehow. My fellow science-based tutors and I ran monthly Q&A/Forum sessions via Zoom on a selection of topics, which went down very well. (I’m glad that I had suggested it earlier in the year, but the truth is that it was my friend and local U3A Science Coordinator, Alan Chadwick, who actually got it up and running successfully; I doubt I could have done so well.) However, this didn’t address the need/demand for the more focused sessions one would normally expect to lead. Some of these could be handled ‘live’ via Zoom, and several tutors took this route, but it didn’t suit the material I had or my presentation style. In particular, it would be difficult to include the demonstrations I try to weave into my sessions. So, without consciously realising it until well after I’d launched myself into my proposed ‘solution’, I turned to the use of an approach I’d tried during the final couple of years of my working life based on flipped lectures. A classic use of this would be to guide students into studying a topic in their own time – I had recordings of lectures I’d delivered in earlier years available for them, together with recommended reading etc. – and to follow this up with face-to-face sessions in which any issues arising from their study could be ironed out. In my ‘locked down’ variant I hoped to translate my pre-existing (face-to-face) sessions into videos that I could upload to YouTube for our U3A members to view as and when convenient. At some point thereafter we’d schedule a Zoom session so that everyone had the opportunity to engage in follow-up discussions and to pose whatever questions might have arisen in their minds.

As with all novel approaches, feedback and proper reflection are important when trying to assess whether the ‘experiment’ has been a success or needs a re-think. Questionnaires and their like do not appeal: too reminiscent of work, and a sure-fire way to dampen enthusiasm. A simpler route would be to assess the overall demand by looking at the numbers registering for the Zoom session and comparing them to those typically associated with a face-to-face session. Then, from the self-selected people who did participate, one might take a look at the questions posed – what folk actually took away as their appreciation of the videos’ content as distinct from my naïve intentions – and any unsolicited feedback. That brings me, at last, to the primary focus of this post.

Although there were decent access statistics for the blog post and evidence that the videos had been viewed, the numbers actually registering and turning up for the follow-on Zoom sessions were relatively small compared to analogous face-to-face sessions. In a ‘normal’ year one might see between 20 and 40 U3A members participating, but there were only a dozen or so at the Zoom sessions. About a quarter of those people sent subsequent feedback by email – all of which was positive I am glad to say. Likewise, the fact that several folk had taken the trouble to formulate and submit questions in advance and/or engaged in the resultant discussion might also be taken as positive. Having said that, a significant number of the questions posed were arguably at a tangent to the actual content of the associated videos; in practice, this doesn’t matter as the topics were fun to discuss: it’s all about science communication after all, and a little diversion can be instructive.

Taken together, it is reasonable to conclude that the format of ‘pre-recorded video plus Zoom follow-up’ was not popular amongst the membership as a whole. However, judging by the feedback received, the brave few who did embrace the experiment seem to have got something worthwhile from the experience.

On that basis, and bearing in mind the large investment of time required, would I seek to offer ‘flipped’ sessions again in the future? Frankly, given the pandemic-derived impetus for the experiment, I sincerely hope the question doesn’t arise! The truth of the matter is that I needed a project on this scale to help fill the year and would almost certainly have proceeded even if I’d known no-one would turn up; moreover, I enjoyed doing it. Thus, every one of the lovely U3A members who did engage with my experiment provided a distinct bonus: each and every one of them rendered my investment worthwhile.

There is a postscript: now that the major part of my pre-existing U3A material is available 24/7 on YouTube I can’t see myself ever presenting it ‘live’ hereafter. This might be considered a negative consequence were it not for the fact that my next U3A project is thereby called into being – to put together some brand new material from scratch; watch this space …

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I append below the feedback I’ve received and the questions submitted in advance by email (in italics) and the few notes I pulled together in case my brain ‘froze’ during the live Zoom sessions. There were plenty of follow-up/'live' questions of course, but I’m not sufficiently skilled at multi-tasking that I could jot all those down whilst also answering them, so only a few are listed below. I promised participants that I’d include all this material in the present post but, unless you particularly want to read it, do feel free to stop at this point.

Feedback

Thank you very much for this excellent course.

I wondered if we would be able to have access to these valuable lectures on the internet indefinitely please, or is there a limited timescale (lifespan?)? [There is no time limit currently envisaged or planned.]

Thank you so very much for fascinating videos and this morning’s session on radiation.

This went so much further than what we learnt as radiotherapy students with the much broader aspect of the subject so well presented. I am new to U3A and have found the course content really stimulating with the standard of lectures.

I will be looking up your other u tube videos.

Thank you for another really fascinating set of videos and the question and discussion session today. I missed out on science education when I was at school and have been trying to fill the gaps ever since.

Thanks for a fascinating Zoom.

Really enjoyed your presentation … I've always felt quite comfortable to have my understanding stretched. Your presentation continued the process especially explaining gravity as fundamental, pervasive, measurable but not yet fully explained. There were good further reading hints too ...

Thank you again for your excellent courses, they make a huge difference.

Your lectures open new doors of learning, & hopefully understanding, food for the soul & life enhancing.

I’m enjoying the videos – at least I appreciate now why you always talk about glasses plural rather than glass!

Thank you so much for this talk – fascinating... I hope I didn’t ask too many questions, but I was riveted.

I have just finished watching your last video on glass. Thank you for putting so much effort into the presentations. As a complete novice I found the material fascinating and although some of the chemistry was above my head, I now have an appreciation of what a versatile and valuable material glass is. It must have been difficult to retire from such interesting work when your passion for the subject is still there!

Questions posed

1) Radiation

What happens to nuclear waste, and will it be a problem long term, or will we have mastered it safely?

It’s a big question, and a serious one. One of the ways forward for the high level waste that needs long-term storage is to incorporate it into a glass. Glasses may be designed to be stable for thousands of years; if in turn these are enclosed in outer protective layers and then carefully stored deep underground away from water courses we are likely to be well protected. There are some exceptionally talented people involved in the research behind these vitrification processes (e.g. https://twitter.com/@clairecorkhill  Sheffield) See also ukinventory.nda.gov.uk Remember, there is always risk – it’s a matter of selecting the optimum way forward on the basis of all available reliable evidence.

Polonium 210 - one of my friends stayed at the London hotel where it was believed Litvinenko was poisoned. About a week later, he was contacted by police at his home in Naples, he was asked to submit to a medical, luckily all clear. Given polonium 210 is an alpha emitter, and apparently was transported in a flask, how could radiation leak out to contaminate hotel rooms, aeroplanes?

Po-210 appears to have been introduced via a cup of tea drunk by Alexander Litvinenko during a meeting with former associates. Po-210 was finally confirmed as he was nearing death precisely because it is an alpha emitter and therefore almost ‘invisible’ to a standard Geiger counter: it took the involvement of specialist scientists with more sophisticated equipment. Once they were involved the trail of contamination could be followed back in time. The two poisoners had contaminated themselves and shared that with items and people around them; obviously, the table setting in the place he’d drunk the tea was also contaminated – especially the dregs in the tea cup. Po-210 is only dangerous as a source of radiation once inside the body, where the alpha radiation kills living cells as the metal is carried around the body (including to the bladder – causing more contamination).

If you keep a glass vase coloured with uranium salts long enough (700 million years!) will it lose some of the green colour.

On the face of it the answer is “yes”, but bear in mind the fact that the decay chain for U-238 takes us, via intermediaries, to U-235 – an isotope which is of course chemically identical to its parent isotope. All radioactive isotopes of U have an associated decay chain but U-238 forms 99.3% of the element, which is why I focused on that in the slides. Thus, given that the half-life of U-238 is about the age of the Earth, the colour will fade – but maybe not at a rate one would notice ;-)

How is a GM tube made sensitive to alpha radiation?

The key is to ensure that the end window is thin and made from something of low density (i.e. relatively few atoms to get in the way). Whilst gamma rays and the higher energy beta particles will have no problems entering the gas within the thin-walled tube, alpha particles will. End windows of mica or occasionally even beryllium (element 3 in the periodic table, a metal – extremely toxic) are commonly used. Thus, whilst it’s harder to detect alpha radiation with a G-M tube it’s far from impossible with the right set-up.

In your demonstration with the various radioactive minerals and aluminium and lead absorbers you used lead wrapped in plastic.  Is there a significant hazard in handling lead?

Lead is toxic; it affects the nervous system and has a tendency to stick around in the body for a long time; it’s an example of heavy-metal poisoning. Lead water pipes began to be phased out decades ago, and lead additives in fuel were removed during the ‘90s and outlawed in the EU in 2000. Lead may be absorbed through the skin – hence the plastic bag.

At a few places in the videos there is a bit of blurring between X-rays which are electromagnetic radiation but are not produced by radioactive decay and gamma radiation also em radiation but is. In everyday language the word radiation is applied to many situations in which the radiation referred to is not nuclear.  I think I understand this but wonder if all your audience do.

This is a good point. ‘Radiation’ may be used of more than one phenomenon; however, at the core of our present topic is the word as applied to radiation having its origin within the nucleus of unstable atoms. (The cross-over in the video was, I think, associated with making the point that gamma rays are themselves electromagnetic in nature – so, a higher energy analogue to x-rays, which in their turn are higher energy electromagnetic radiation than the colours we perceive in a rainbow and so on.)

Comment: The nucleus changes during radioactive decay: it’s not that a part of the nucleus is ‘thrown out’ but rather that there’s a change to the nucleus which results in a newly-created entity leaving with the excess energy of the change. (e.g. a nucleus splitting into two, with one being an alpha; a neutron decaying into a proton and an electron, with the electron leaving; a whole nucleus shuffling down to a less excited state by emitting a gamma ray photon)   

2) What’s so special about the Earth?

How come we’ve landed up in a highly desirable area (estate agents) as a third area out from the Sun?

We are able to ask questions like this because we live on this particular planet – we wouldn’t be around to pose such questions from Venus or Neptune. There is a major philosophical theme here.

What pulled the plug out to get rotation going. Why does everything have to rotate and not stay still.

Early universe: once cool enough for atoms to form (H, He) they were at high T and therefore moving fast; more cooling meant that they could clump together (gravity), but all it takes is a tiny instability in one place to begin to affect all other places around. Locally, there are also the effects of collisions.

Gravity is a complete mystery to me. Everyone takes it for granted. I can’t. Want to know more. What is this prime force and how did it start?

The classic description by Newton tells us that it is a fundamental property of anything that has mass: it’s intrinsic to the universe. It’s not a strong force and may be dominated by other effects at short distances (e.g. magnetic, electrostatic) but for large masses and over long distances it becomes the boss. Einstein’s theories of Special and of General Relativity offered us a model of space-time which is curved/distorted and in which we ‘fall downhill’. We feel our weight because the Earth’s surface is preventing out fall down the slope towards its centre. A key observation was that the path of photons from distant stars is bent as it comes close to the Sun. Listen to ‘The Curious Cases of Rutherford and Fry’. (It was at this point in our Zoom session that we engaged in an extended discussion on the myth of the ‘lone genius’.)

Who names and accepts planet names?

Many different cultures named them independently. Earth from 8th century Anglo Saxon word ‘Erda’ meaning ground/soil; Sun – from middle English sunne (Chaucer’s Canterbury Tales). Planets names from Roman myth. Stars often named from Arabic Polaris has also been known by the names Alruccabah, Angel Stern, Cynosura, the Lodestar, Mismar, Navigatoria, Phoenice, the Pole Star, the Star of Arcady, Tramontana and Yilduz at various times and places by different cultures in human history. Some things are named after their discoverer: Kuiper belt, Oort cloud. All objects, bodies and surface features now overseen by the International Astronomical Union.

Termination shock? Heliosphere: You mentioned it is like a 'shock wave'. Could you explain a bit please? Is it just the name of a region that has certain properties or is there something physical there? How much of a barrier is it? Does it behave as a partial two-way barrier? As I understand it, we do get some cosmic radiation incident on Earth, as well as particles from the solar wind.

The term came from a diagram I had inserted into a slide. Heliopause – when the influence of the Sun (magnetic field, solar wind) no longer dominates over galactic forces. This might be thought of as the extent of the Solar System. (The Oort cloud is further out – held there in orbit by the Sun’s longer-ranged gravitational attraction.)

Can you say more about the creation of the molten core and solid centre of the Earth?

Early stage of solar system the planets formed from the gravity-driven) aggregation of gas, and small particles. As ever-larger clumps collided and coalesced the energy of the collisions heated everything up – everything from Mercury to Mars began life as a ball of molten material which then slowly cooled and began to solidify. (The same is true of the outer planets, but they became large enough that their gravity could hold on to a lot of gas as well.) In fact proto-Earth was re-melted in a hugely violent collision with another proto-planet – estimated to be about the size that Mars is today) – out of this collision came the debris which formed our relatively huge Moon.

Is there anything similar on Venus, Mars or the Moon?

Mars is relatively small compared to the Earth, so it has cooled faster but it does still have a molten core – however, perhaps due to the size, there isn’t the motion required to generate a magnetic field. Venus is more similar to Earth in size, but it rotates very slowly (one day on Venus is almost 4 Earth months – in fact its day is slightly longer than it year) and so we don’t get the motions required for either tectonic plate movement or a magnetic field.

I was particularly interested in the equation relating to the likelihood of developed life on a planet in other galaxies. Mostly obvious and difficult to get your head around the infinity of infinities of possible galaxies but what I had never thought of before, and should have, is the fact you have to take time into account too.  That is that life could have existed and finished or maybe not started yet.  So not only the number of galaxies and planets to consider but also the coincidence of life occurring on one at the same time as a life form such as humans on earth is capable of making contact.  Not to mention that contact must be recognisable by the other.

Yes indeed. It sounds as though you know of the Drake equation (see https://exoplanets.nasa.gov/news/1350/are-we-alone-in-the-universe-revisiting-the-drake-equation/ for example, noting the ‘guesstimates’ required) and the Fermi Paradox (e.g. https://www.forbes.com/sites/startswithabang/2018/06/26/no-we-cannot-know-whether-humans-are-alone-in-the-universe/); I am content to await evidence.

Age of the Universe: You mentioned about 14 billion years. Has this been calculated by working backward to the Big Bang and based on current observations of the expansion rate? Or, is the calculation much more sophisticated than that? Detail of the maths not required!

We can get a ‘guesstimate’ of the age simply by reversing the clock on what we currently observe, but there is a need to be a little more subtle than that. We now know, on the basis of our expanding body of observations (which have, in effect, taken us back to within a few million years of the Big Bang), that the rate of expansion was different in earlier epochs. Consider, for example, the fact that when everything was closer together the gravitational attraction between masses was greater – so more tendency to slow the rate of expansion.   (We engaged at this point in a discussion of what the ‘observable universe’ means, introducing Dark Matter/Energy etc.)

Earth's Magnetic field: I can see why relative motion between a solid ferrous inner core and molten (ferrous?) outer core will produce a magnetic field, but how do they think these relative motions might have come about?

Actually, this is a complex problem: a fuller picture is that the solid inner core (about the mass of the Moon, but almost all Fe) rotates eastward a little faster than the Earth overall (it laps the rest of the planet once every 400 years or so) – it gets this ‘push’ from the action on the Fe of the Earth’s geo magnetic field. This means that the fluid outer core is travelling. In effect, in a westward direction compared to the inner core. The magnetic field in created by complex convection currents in the fluid outer core, and its relative motion compared to the inner core is what leads to the tendency for the poles to drift over time. The Fe sank to the centre early on in our history; the inner core is gradually growing as the Earth slowly cools

Does the vortex in the bath go the same way in the southern hemisphere as here? Do Runner Beans twine the same way in Australia as they do in UK ?  (ref Flanders and Swann, The Honeysuckle and the Bindweed)

Yes, no difference – urban myth. They follow the Sun, wherever they are.

And a bit about Sun Dogs which we see occasionally during our sundowners on Whitstable beach, and the Northern Lights which we were amazed to watch from a beach on Sheppey one night a few years ago.

Refraction through hexagonal ice crystals in the upper atmosphere; 22º to either side of the Sun, sometimes with an arc (type of halo).

3) Glass: a look inside – science, technology and art

Please discuss de-colouring agents a little more, specifically Manganese dioxide added to make greenish glass clear.  I did research several years ago on 19th Century lavender window glass.  Manganese was added to glass to remove the green tinge to glass.  But with oxidation/ exposure to sunlight, the glass windows turned lavender.  You can still see some of these lavender windows in vintage buildings…. Back Bay homes in Boston, Walmer Castle in Kent, Sanssouci Palace in Potsdam, Germany.   Occasionally I’ve seen a window or two of the same purple glass in old buildings which haven’t been “restored”.  I would love to hear your opinion about this effect.  

We can purposefully add a metal in order to induce a colour, but the raw ingredients may contain metal impurities; a common one is Fe. Contaminants need only be present in tiny amounts to introduce a colour. The green tinge is often associated with Fe and it’s possible to mask this by using a metal offering complimentary colours (e.g. Se – pink; Co – blue). Thus, a better term would be neutralising or counter-dyeing. These will reduce the overall light transmission, but can lead to a greying of the glass.

High purity raw materials will help, and it’s often important to control the oxidation state of the metal (controlling the proportions of O present in the furnace) and the heat-treatment of the melt.

Mn was popular because it has a range of oxidation states and the highest, Mn(VII), absorbs green light but transmits to either side … generating shades of purple; Mn also helps ensure the iron present is in the Fe(III) state (Fe3+), which imparts only a pale yellow to the glass and is therefore easier to neutralise. The action of UV light imparts sufficient energy to alter the oxidation state of the metals present – including Mn – and so initial colours may alter over time. Indeed, the use of artificial UV lighting in so-called ‘purpling boxes’ will accelerate such effects.

Mn ceased to be used in this way from WW1 as the major source at that time was Germany.

I do stained glass and glass mosaics as a hobby.  Some glass breaks evenly, and some breaks irregularly. Please discuss this effect a little further.         

From Léonie Seliger, head of the Cathedral’s Glass Studio:  “Some glasses are simply harder than others due to their composition. American opalescent glasses for instant are really difficult to cut; the feel under the glass cutter is almost as if you are trying to get through very hard plastic. You don’t hear the nice musical sound a glass cutter’s wheel makes on normal glass (the sound the French call ‘le chant du diamant’), and the cut is almost invisible on American opalescent glass.  It’s hard to break, and I find the break runs away from the cut more often than on normal glass. A major suspect for glass breaking irregularly is poor annealing. Glass that retains internal stresses (because they were not given enough time to dissipate as the glass cools down) will jump unexpectedly, sometimes even while you are still running the glass cutter over it. That can give you quite a start, wastes glass, and makes me very uneasy about using glass from a poorly annealed sheet. It’s alright if you cut it into small pieces, but I would steer away from using large pieces from a stressed sheet in a window. They could fracture when experiencing a measure of strain that well-annealed glass would withstand without any problems.”

My perspective:   I think there are two principal length scales: atomic and mesoscopic.

On the atomic scale it's the chemical bonding that dominates of course; composition is the key factor here. Some of the hardest, most brittle glasses we ever made were phosphates containing multivalent rare earth metals; that was all down to their atomic-scale structure and the bonding that went with it. Move to silicates in which the 3D [SiO4] tetrahedral network is heavily disrupted by alkali metals and these physical properties alter considerably. At longer length scales, the effects of inhomogeneities come into play: variations in local density and/or composition, which are highly likely to have their origins in processing (- batch mixing, heating profile and annealing). I suppose one might tack on a third scale associated with microscopic/macroscopic factors like inclusions in the glass, including bubbles, and variations in thickness - but that's beyond my understanding.

Does this have possibilities ?

“in which they took balsa wood and removed its lignin – a component of wood that gives it [compressive] strength and colour [cell walls and related tissue; cellulose provides tensile strength]. Acrylic, which is non-biodegradable and water-repellent, was introduced into the remaining tissues where it filled both the tiny pores left by the removal of lignin and the hollow vessels that carried water in the tree. That, said Montanari, not only helped maintain the wood’s structure but also restored its strength and improved its optical properties. The upshot was a frosted-looking wood-based material. In the latest work the acrylic was mixed with another substance called polyethylene glycol, which permeates wood well.” https://www.theguardian.com/environment/2019/apr/03/scientists-invent-transparent-wood-in-search-for-eco-friendly-building-material

How do they make these?

Millefiori Glass Paperweights; it’s a bit like the glass version of ‘Brighton rock’, but perhaps easiest to watch:

https://www.youtube.com/watch?v=CYUqvLAeyg4&ab_channel=KSMQPublicTelevision

https://www.youtube.com/watch?v=dQw_yUsTVS0&ab_channel=PanosEgglezos

 

I was quite surprised to find how recent plate glass windows are.

Yes, the really smooth, highly transparent and toughened variant arrived during our lifetime. There were large sheets before that, but of relatively poor/non-uniform quality. For details see: ‘Float: Pilkington’s Glass Revolution’ by David J. Bricknell (ISBN 978-1-905472-11-6, 2009.

Fascinated by the idea of neutron diffraction.  I'm OK with wave particle duality, de Broglie wavelength, electron diffraction etc so am fine with the principles, but how do you separate the neutrons, how can they be accelerated to required energies, and how are they detected once diffracted?   

You’ve done the hard part; coming to terms with the fact that sub-atomic particles can behave like waves and thus be used to perform diffraction experiments is the key step; thereafter it’s fairly conventional.

Neutrons streaming from a nuclear reactor, for instance (e.g. https://www.ill.eu/about-the-ill) emerge with a range of speeds – i.e. energies, or wavelengths – so we can use a suitable crystal as a monochromator via Bragg’s Equation: hey presto we have a monochromatic beam of neutrons heading towards our sample. Of course, we first have to define a ‘beam’, but this can be done using standard shielding material to make a collimator. Post-sample detection as a function of angle is also relatively straightforward since neutrons, though uncharged, will interact with matter; a common form of detector uses scintillation: the neutron is absorbed by an atom’s nucleus – for example, Li, doped into a glass, is highly efficient at absorbing neutrons and when it does so a gamma ray is released which may then be detected relatively straightforwardly.

One can separate the neutrons generated by an accelerator source into their energies, or wavelengths, simply by timing their flight between two fixed points (using small detectors that sample the passing beam). The detectors will not now sort what emerges from the sample as a function of angle but rather on the basis of their time of flight (e.g. where I worked for a few years in the early ‘80s https://www.isis.stfc.ac.uk/Pages/About.aspx - I’ve posted on this a few years ago on my blog: https://bobreflected.blogspot.com/2016/03/large-scale-facilities-for-small-scale.html ).

How long does it take to grow a ‘Venus Flower Basket’ skeleton?

Because euplectella aspergillum is found at such great depths the information about its active life is limited. This is an animal that protrudes from the rocky ocean bottoms, also making it a benthic (bottom dweller) animal. Details of reproduction of E. aspergillum are not known, therefore we can only assume it’s similar to the normal forms of reproduction in related sponges.

How much stronger is glass in compression than in tension?

The compressive strength of glass is extremely high: 1000 N/mm² = 1000 MPa (for comparison, atmospheric pressure is 101 KPa – i.e. about 10,000 times smaller). This means that to shatter a 1 cm cube of glass, it requires a load of some 10 tonnes. Its resistance to tensile stress is significantly lower:  40 MPa (N/mm²) for annealed glass and 120 to 200 MPa for toughened glass (depending on thickness, edgework, holes, notches etc). (by the way, glass is a perfectly elastic material: it does not exhibit permanent deformation, until breakage. However it is fragile, and will break without warning if subjected to excessive stress.)

 

Third Age Physics

This post serves as the 'contents page' for a series of videos to be uploaded to YouTube during the final months of 2020. In essence, they are the online version of various physics-inspired sessions put together during recent years for the 1000+ members of my local U3A branch. This year, being the fun-fest that it isn't, requires a different approach - one that doesn't depend upon face-to-face indoor events. Assiduous readers of my blog - if there are any - will realise that this is the third series of videos to be made available this year, and the second to be dedicated to the non-expert but highly intelligent U3A participants I have come to love spending time with. (Details of the first 'U3A series' may be found in an earlier post, here. There is also a series curated from the surviving recordings of my pre-retirement lectures for Foundation Year Physics students; the details are here.) Apart from providing the YouTube address of each video, I'll use the post as a convenient repository for the details of any 'further reading' (or viewing) suggestions that come to mind. What I'll not be able to offer here is access to the online discussion/Q&A sessions planned as a follow-up to the initial video; sorry, but those must remain within the purview of my local U3A coordinators.

Each video will have been recorded in a single take, and without a script or notes in order to try to reproduce the 'live' experience. Also, it would simply be too dispiriting to deliver a long and stilted monologue by reading from a script ... oh how I miss sharing my love of science face-to-face with a group of people who can provide real-time feedback!  This video-based approach is, you can tell, not my ideal - although a variant of it worked very well when I was teaching students (see here) as face-to-face follow-up sessions were built into the process.  The upshot is that viewers will get all my stumbles, throat-clearing, failures in memory and moments of lost track: forbearance is a good quality in such contexts. I am not, as you will rapidly discern, a 'natural' in front of the camera. (I'm reminded of the media training day I attended a few years prior to retiring during which I was recorded being interviewed: the feedback was hilarious. Apparently, one of my sentences lasted 35 seconds! You have been warned.)

Only after beginning the project did it fully dawn on me what a significant undertaking it was. It's far more tiring to record a talk than it is to share it face-to-face with people. Furthermore, I have allowed myself the opportunity to include more material than I might have risked in a live performance. I have tried not to lose all sense of restraint in this regard but it's been good to have the opportunity of sharing a few more artefacts for instance. What I will try to ensure is that I build a 'sanity break' into the videos every 40 minutes or so: a juncture at which it's easily possible to have a rest. I may do this within a given video or by splitting the thing into two or more parts.

One more thing: although it's entirely possible to read my blog and watch the videos on any suitable device, the larger the screen the more you'll see. It was ever digitally thus 😉

1. What's so special about the Earth?
87 minutes, with an intermission at 42 minutes; there is seven minutes-worth of optional additional material tacked onto the end.

The original U3A programme abstract read: "With the discovery of planets orbiting stars other than our own Sun, several of which have been labelled ‘Earth-like’, it might be tempting to conclude that we’re really not that special. Moreover, some might argue that humankind ought to consider spreading out and colonising such exoplanets. Is any of this reasonable?" This topic is tackled first as there is only one practical demonstration I wished to show. This was, in a way, selected as the test-bed for subsequent videos in the present series.

There are a couple of my former blog posts which include relevant information and additional links: on star and planetary formation and on the very subject of the U3A talk at the heart of this topic, here. Indeed, many of the links shown below are also included in these earlier posts.

Useful video/animation links cited within the talk include:
On the scale of bodies in the Solar System
On solar wind 
On tectonic plate movement and similarly here
On the Earth-Moon rotation about their barycentre  
A fun look at the earth’s rotation on its axis.
Also, there's a great TV documentary available on the importance of the Moon. Whilst on the subject, this is a link to a brief computer simulated animation depicting the probable violent birth of our moon after the Earth collided with a Mars-sized planet in the early years of the Solar System; it shows clearly why the chemical/mineral composition of the Moon is almost identical to the Earth: they both solidified from the same 'mixing pot'. Indeed, since making the video I have come across another contribution to life on Earth made by the Moon: apparently, it once had a weak magnetic field which provided important additional shielding for emerging life on our planet - see here for details.
(Diagrams and figures used in the slides have references to their sources included on the page itself.) 

p.s. I am indebted to Leigh Edwards for pointing out in a comment on YouTube that there are ~100-200 billion stars in the Milky Way - I used the word "million" in error; my apologies.


2. Radiation: bad, benign, beneficial - Parts 1 ,2 & 3

Part 1: discovering the language (51 minutes)

Part 2: bad and 'benign' - balancing risk (62 minutes, with an intermission at 27 minutes)

Part 3: beneficial uses of radiation (32 minutes)

The original U3A programme abstract read: "Radiation, has been of considerable interest for over a century – but how much do we know about it? Together, we’ll take a look at its origins and effects – bad, benign and beneficial – from a scientific perspective."

There is a blog post written previously which include relevant information and additional links, here. 

UK figures on radiation exposure. Other links are shown within the slides in the video.

3. Glass: a look inside - science, technology and art
Part 1: what is a glass and what goes into the mix? Glass in nature, both hot and cold. (58 minutes, with a break at 32 minutes)

Part 2: glass-making technology; looking deeper inside. (45 minutes)

Part 3: staining and painting, sculpture and culture. (41 minutes)

Part 4: technology and engineering - glass in the development of science, communications, consumer items, architecture and the kitchen. (55 minutes, with a break at 33 minutes)

Part 5: towards the cutting edge - bioactive glassy materials and some major breakthroughs in physics; myths, breakages and sound. (67 minutes, with a break at 37 minutes)

The original U3A programme abstract read: ‘Glass has existed in nature for billions of years; mankind has been using it since the Stone Age. It is ubiquitous, often irreplaceable, in art, in technology & engineering, & in science. We'll discover, at the level of its constituent atoms, what a glass is; we'll look at its uses in technology, in art, architecture, & in science: from bottles to stained glass windows, to scaffolds for re-generating bones & for drug delivery.’ This online version covers material from what was originally a little less than four hours of 'live' event spread across three sessions, hence the necessity for multiple videos. Having indulged myself by including an extended range of 'show-and-tell' artefacts, the five constituent videos in this series will, if you watch them all, take approximately four and a half hours. By the way, I hope you like the green-screen backdrops to this series: if nothing else, it will make a change from the bookcases against my study wall.

There are several of my former blog posts which include relevant information and additional links, but here I include only three of them: here, here and here. There is also a one-hour video, recorded some years ago in Canterbury’s Heritage Museum – now closed, sadly – which covers some of the same ground within a single one-hour video: here. 

Additionally, you might like to augment this series with the following material:

On 'Prince Rupert's drops' - thermally toughened glass; there are some great ultra-slow motion sequences. YouTube provides a treasure-trove of accessible material on glass-blowing, float glass processing, making stained glass panels and all sorts of other relevant topics.

Some of the general interest books on glass from my shelves, should you want or need additional reading material:

4. Colour 

Part 1: introduction, Newton's approach (the electromagnetic spectrum, prisms, rainbows etc.) - 35 minutes.
Part 2: a look at Goethe's observations and Turner's use of his idea (perception and interpretation) - 34 minutes.

There are a lot of demonstration-type experiments in the face-to-face original session, so it's impracticable even to attempt to translate this into video format given my limited home setup. However, by stripping out the more challenging demonstrations, a variant of the material becomes a (hopefully serviceable) possibility.

The original U3A programme abstract read: ‘Most of us grew up on Isaac Newton’s theory of colour; we use it to explain a multitude of everyday things like rainbows. There were alternative theories however, like those derived from the careful observations of Johann Wolfgang von Goethe – who influenced JMW Turner’s choice of colours very significantly. We’ll explore the world of colour from a scientific perspective, and in the process consider the role of individual perception in our technicolour world.’
There are a couple of my earlier blog posts which include relevant information and additional links: here and here including a link to one of the projects I undertook with the Turner Contemporary gallery in Margate (here). 

Also, there's a fascinating video series available on Goethe’s approach to colour.

If you want to dig a little deeper into the phenomenon of the refraction of light, then video 30 in the 'Physics Beyond the House' series will provide further details; other videos in the series offer additional information on the electromagnetic spectrum etc.

“So, what is it?” – astronomy that is

Although I watched some of the early series, I confess that the BBC’s ‘Red Dwarf’ never became one of my favourite TV shows. Perhaps it was the science nerd in me, although that hasn’t dampened my enjoyment of other SciFi programmes or movies. However, a handful of snippets seem to have lodged in my mind, one of which lies within the ‘White Hole’ episode (see here) in which the concept of a white hole is discussed. Their interpretation of the physics associated with mathematical models of white holes, which began to emerge during the 1970s and onwards, was almost nonsensical – but the repeated question “So, what is it?” reflects an important aspect of the life scientific. For reasons which will hopefully become apparent as you read on, it’s a memory that resurfaced recently as I reflected on a Q&A session I was involved in on the subject of astronomy.

There were no obvious images to go with this post, so I’ll treat you to my latest attempts at astrophotography from my garden: Mars and Venus ... The other shot of Venus was taken in May, when far less of its illuminated surface was visible from Earth - that's why it's so very bright at present. For a little more detail on my stumbling attempts at astrophotography see my previous blog post, here. (Just for fun, note the south polar ice cap just about discernible on Mars.)

Well, what do you think astronomy is? The commendably brief definition provided by the online Collins English Dictionary states that it is “the scientific study of the stars, planets, and other natural objects in space” or alternatively “the scientific study of the individual celestial bodies (excluding the earth) and of the universe as a whole”. As a former academic who worked cheek-by-jowl for several decades with professional astronomers, and as an amateur stargazer myself (see my previous blog post, here) I’d have to say that either form of words covers the subject tolerably well. I could take issue with the dictionary at the fringes of its definition, but that might end up multiplying the number of words without generating a significant improvement to one’s actual understanding. One of the things I’ve repeatedly discovered over the years in speaking to non-experts about science is that the connotations they have for words with which I feel ‘at home’ may be quite different to my own. Avoiding the pitfalls that can arise from a failure to get to grips with the background and expectations of participants is a key ingredient to successful science communication and engagement. I recently had another opportunity to observe the existence of this apparent dissonance … 

Earlier this year – indeed, well before lockdown/shielding – I hatched a plan, in cahoots with the science coordinator of the local branch of the U3A (Alan Chadwick, search here for subject coordinators, science) to organise and co-host an open ‘Q&A’ session as part of the 2020 summer programme of events. Topics in science account for only about 10-15% of what is on offer to members, so I’m continually on the lookout for ways in which one might extend and broaden the appeal. I contacted my fellow science theme leaders – a handful of similarly committed people – and made sure that enough of them were interested to make it viable. As with so many of our ideas, good or not-so-good, the rise of the COVID19 troubles forced a rethink. We opted for a series of monthly video-streaming sessions, each having a specific theme and with questions sent in advance to the two people designated as leaders. Second in the series, after ‘Diet’ was a session on ‘Astronomy’, for which I was one of the volunteer leaders. It’s not my intention to summarise the 90-minute session, although I can say that it was as much fun as it was exhausting, but there are a couple of thoughts that occurred to me during the run-up to it and as it unfolded. The first and obvious point is that the submitted questions, augmented during the session through the online ‘chat’ facility offered by our chosen platform, covered a lot of ground. More than that however, one might interpret the questions as providing a snapshot of what our participants thought astronomy was actually all about. Thus, alongside the choice of observing targets and what instruments might be useful, and several cosmology questions centred on the Big Bang, black holes and the various multiverse theories, we had questions on colonising Mars (and further afield), space junk and extra-terrestrials. One lovely question alluded to ‘spiders on mars’ – see here for the non-Bowie answer ;-) 

It might have been tempting to filter or to re-interpret the submitted questions, but that would have been a mistake in my opinion. All the topics raised were, in the minds of our sharp-witted questioners, ‘astronomy’; as such, each and every one of them deserved to be taken seriously and given as sensible and as full an answer as we could. When I was still an academic, and doing my best not only to teach a physics syllabus but also to inspire in a broader sense, there were a couple of phrases I used early on when talking with each year’s new intake: “there’s no such thing as a silly question” and “science is always wrong”. Both require humility on the part of the lecturer/course leader. The first speaks to the desirability of starting from where the questioner is, and not imposing pre-conditions. The second opens up a discussion on the scientific method and how it progressively reveals the nature of our world/universe to us, with each generation of theories yielding to the better ones that follow. Both aspects came to the fore more than once during our Q&A, even if only tangentially.

Our next monthly online science forum is on ‘ecology’, and the one after that is on ‘chemistry’. I’m chairing the latter so I can only hope that I make the two-person ‘panel’ and their questioners feel as valued and comfortable as I was made to feel. So, a blockage to our original plan for a one-off Q&A has been turned into an opportunity for a whole series of online sessions … science communication in action, aided and abetted by the ever-present forces of serendipity.

Pictures of a stargazer

It’s a good job I write primarily for myself, for the sheer pleasure of playing with words as a way to uncover my thoughts. It’s a good job because it allows me cheerfully to draft this post even though I’m sure that, for some of its readers, there’ll be a sharp intake of breath as they discern my ignorance and naïvety. I’m going to share with you my reflections on the stumbling restart in retirement of two of my childhood hobbies: astronomy and photography. In truth, neither of those terms are being used properly. I’ve seen the work of amateurs who take amazing photographs and I don’t compare – I was always more interested in aspects of technique, and, back in the day this included processing of ‘black and white’ photographs in various borrowed darkrooms. Even now, you’ll see me playing with the options on my smartphone rather than worrying about composition. Likewise, I’ve worked alongside and been in awe of talented professional astronomers (see here) and I marvel at the knowledge of dedicated amateurs (e.g. here). Thus, whilst I certainly learnt my way around the constellations and the details of the solar system as a child, it’s still more accurate to describe me using the diminutive: ‘stargazer’. Indeed, despite having treated myself to a retirement present of a lovely telescope, I remain happy simply to gaze: to gaze either at the whole sky – or what fraction of its delights that light pollution leaves to us – or, nowadays, to let my telescope meander across the heavens. Every patch of the night sky I turn my attention to, it seems to me, contains examples of unutterable and mysterious beauty. However, I have latterly begun to play with astrophotography; these are my reflections on the early stages of my rediscovery of the night sky. My recommendation is that you try to read it on a screen larger than a smartphone as there are a lot of images that will benefit from the expanded scale. Make yourself a drink and find somewhere comfortable to sit as this is going to be a long post!

Day one: assemble the delivered tripod and equatorial mount, with its geared motors; put the telescope together, checking the alignment of its mirror, fitting and aligning the small ‘finder-scope’ used to navigate to the right bit of sky, and fitting an eyepiece. Everything then needs to be balanced so that the small drive motors are not placed under strain; I’ve taken to using insulating tape in order to mark balance points etc. as it reduces the time taken to get everything set up for an evening’s observation in the garden. You can find all sorts of excellent descriptions of how the various sorts of telescopes work, so I’ll not bore with details beyond the fact that mine is a 150 mm Newtonian reflector on a motor-driven equatorial mount. It has a relatively long body, which helps with contrast when viewing planets. The key point about the equatorial mount is that it’s set to the observer’s latitude (51.28º N in my case); thus, once properly set up and pointing at the object being observed, it requires only one motorized drive in order to keep that object in the field of view as the Earth rotates underneath. The important phrase is ‘once properly set up’ – therein lies many a challenge. (All my kit was purchased locally, from F1 Telescopes. Sadly, after 20 years supporting amateur astronomers in Kent, they have recently ceased trading.)

After an initial attempt to capture images through the telescope’s eyepiece using a clamp to hold my smartphone in place, I gave up. It was an inexpensive method, but very frustrating in practice and I failed to get anything I was genuinely pleased with. I therefore opted for a bespoke imaging device which is in essence a digital camera or, rather, it’s the electronic heart of a camera: the light-sensitive chip that captures the image. The camera’s optical components, i.e. the complex lens assembly, is replaced by my telescope and all the software to control exposures, store the resultant images etc. resides in software on my laptop. My camera is the purple device shown above (Altair Astro GPCAM-290c). It directly replaces the eyepiece, and connects to my laptop via a USB cable.

My initial ambition was to be able to view objects within the solar system – all eight planets if I could, although I was only confident about observing the Moon, Venus, Mars, Jupiter and Saturn. These are easily visible to the naked eye as bright spots in the sky – a large disk in the case of the Moon – although it’s far harder to make out colour and detail, even using binoculars. The choice of telescope was made with that overall goal to the fore. Beyond that I thought I might enjoy a few star clusters, like the Pleiades and perhaps a binary star here and there. It is probably true of all hobbies, but the evolution in my objectives was rapid. I started hunting out galaxies, such as our neighbour Andromeda, and nebulae (vast clouds of gas and dust, from which stars are created) like the Orion Nebula which, you’ll not be surprised to hear, sits within the constellation of Orion.

Here it all is, set up in my back garden, camera connected to my laptop. The tripod has been aligned to North and levelled, the telescope is balanced and we’re ready to go.

Although one can pick out lots of detail on solar system objects through the telescope eyepiece, one is immediately and repeatedly reminded that the human eye isn’t good at seeing colour when the light intensity is low. That issue is made even more obvious when observing deep sky objects like galaxies and nebulae: they might easily be written off as wisps of cloud to the uninitiated. (Deep sky refers to objects that lie outside the solar system and are not individual stars, e.g. other galaxies, star clusters or nebulae.) So, having purchased the telescope from the gifts given to me by my family for Christmas/birthday, my wish-list for the following year contained a plea for contributions towards a decent first astro-camera. It’s barely left the telescope since. Everything has a cost of course, beyond the monetary, and in this case it’s the need to master a lot of new software in order even to capture an image in the first place let alone process the resultant data into something vaguely pleasing. The learning curve is steep and long, and the further I travel along it the more I realise I need to learn. Thankfully, there are many others out there travelling the same road – and some are sufficiently far ahead that it’s possible to learn from them. On Twitter, for instance, I’ve latched on to several people’s posts as a source both of inspiration and education (e.g. this tweep and this one) and have found some genuinely useful material on YouTube (e.g. here). Also, to be frank with you, I’d be further along the road were it not for the fact that the COVID-19 lockdown – shielding in my case – had the bizarre effect of sapping the fun out of pre-existing hobbies. As a result, I all-but ignored my telescope, and creative writing, and reading, and … for several months. I replacing them with the creation of a couple of video series: Physics in the House aimed at the membership of my local U3A branch (here) and Physics Beyond the House. Although I’m still not writing much – snippets, and a couple of free-form poems in order to have something to discuss over Zoom with the Creative Writing group I’m in – I have started reading again, and most importantly I’ve had the telescope out in the garden once more.

Rather than expose too much of my inexperience in this post, I’ll show you a few of the images I have captured. I’ll use the associated captions in order to fill in a few of the details.

These images of the Moon illustrate one of the issues. The image on the left is a picture captured using my smartphone at the eyepiece: I get the entire Moon, but the detail is poor; I could have persisted using the ‘Raw’ and ‘Pro’ options on the ’phone camera in order to control the setting manually, but the incentive was weak given the difficulty of aligning the thing in the first place. Having moved to the bespoke astro-camera and it’s possible to get the central image. In terms of quality, this is so much better – but the field-of-view (FoV) is severely limited. Now, the Moon has an apparent diameter which extends across 31 arcmin – i.e. about ½º – so that implies my telescope/camera combination will image only about ¼ - ⅓ of that, or about 8-10 arcmin. (There are 60 arc minutes in one degree, 60 arc seconds per arcmin.) Thus, to get the image on the right I had to combine five separate overlapping images into one mosaic composite. The detail is far better resolved; indeed, by comparing the image to a lunar map (- there’s an excellent app called LunarMap HD which will suffice for most purposes) I estimate that features down to about 30-40 km are identifiable. Although it took a lot of time and effort I think my composite image is rather nice, even though I say so myself ;-)

The Moon video above, which is best viewed in full screen mode, illustrates two important points: the way in which images are captured and the effects of atmospheric turbulence. Playing the video in slow motion and/or on a larger screen will help reveal the apparent ripples on the Moon.) ‘Seeing’ is the astronomer’s term for the effect of turbulence caused by thermal effects in the atmosphere which cause variations in its refractive index and therefore distortions in what is observed at ground level. (See video (17) in my Physics in the House series for an explanation of the phenomenon of refraction.) However, it also allows me to introduce a key feature in the image-capturing process. One doesn’t, as a rule, simply ‘click’ and take a single frame; instead, an extended series of frames (referred to in the jargon as sub-exposures, or ‘subs’) is captured in the form of a movie file. The details of each frame are set in advance – so, for instance, the exposure time might vary from a fraction of a second to several minutes – as is the total number of subs, which is a number typically (for me) in the hundreds. Ideally, the telescope would be set up so precisely that longish exposure times would be practicable and an accumulated total of hours of subs collected. I’m not yet in that league; at the moment I tend to use subs of no more than a second or two at the very best, and I seldom manage more than 500 of them at a time.

These images of Venus (108 million km from the Sun, c.f. the Earth at 150 million km) bring us to the next point. Given that multiple sub-exposures, subs, are collected as a movie, there has to be a process whereby they can be added together: this is called stacking in the trade. There are all sorts of software packages available to help one manage this. I started with Registax but subsequently moved across to AutoStakkert, although I still use Registax for a final 'polish' using its wavelets analysis function. In essence, both of these free-to-download packages allow the user to combine the best of the subs into a final stacked image - I simply find AutoStakkert easier to use. It sounds ‘easy’ but in this stage, as with all the other stages, there are many possible routes one might follow. The version on the left was stacked via one ostensibly reasonable route whereas the image on the right, which is significantly ‘sharper’ is the result of taking an alternative route … Whilst there are useful blog posts and YouTube videos, it seems that trial-and-error is the expected way forward. (To be genuinely useful, a tutorial needs to come from someone with experience and understanding and an appreciation of the subtleties of a teacher; this is a combination of skills and attributes hard to find in the plethora of material available online.) In passing, it’s worth noting that Venus appears featureless because it’s completely covered in relatively reflective clouds - I'd need sensitivity to uv light in order to be able to pick out variations. Also, because it’s closer to the Sun than is the Earth, we get to see it as a crescent – for exactly the same basic reason as we enjoy the waxing and waning phases of the Moon. The images shown are in greyscale, but when attempting colour images one needs to be aware that digital cameras are most sensitive to green (see the very first test image I took, below, of a distant TV aerial). Further image processing is a necessity in order to bring out the colours; I use an old version of Adobe Photoshop (CS) for this. To be honest, this is yet another stage in the astrophotography game that I continue to struggle with: there are endless combinations of ‘levels’, ‘curves’, ‘colour balance’, ‘saturation’ and ‘brightness/contrast’ to play around with. Experience is everything, and that takes time to accrue.

The above images of Jupiter (780 million km from the Sun), and particularly of Saturn (1.4 billion km from the Sun) show how important it is to have good ‘seeing’. Both stacked images came from ~500 sub-exposures (subs), with ~25% of the best of them contributing to the stacked images seen here. The picture of Jupiter looks OK – indeed, we can see three of its moons (see re-processed images below, in which the brightness around the planet has been boosted; the inverted image on the right provides another route by which fainter objects might be spotted). The stacked image of Saturn is less good however: we can’t resolve even the separation of the two major ring systems, which I’ve observed through the eyepiece before, and none of its moons are visible. The images were collected on the same night’s observation earlier this month and provide a perfect example of the losses one incurs when the seeing is not optimal.

Now we come onto Deep Sky images, although still within our own galaxy, the Milky Way. Shown above is M32, the Orion Nebula, which is a vast cloud of dust and gas – the material from which new stars are formed. The cloud is illuminated and energised by some very bright stars – the four near the centre of this image – which are emitting a lot of UV light and causing the gas to glow. It’s a little over 1,344 light years away (i.e. the light which formed this image began its journey across space in the year in which, according to Wikipedia, “King Wulfhere of Mercia dies after a 17-year reign and is succeeded by his brother Æthelred; King Hlothhere of Kent re-establishes Kentish supremacy in London; in Japan, Emperor Tenmu decrees the end of serfdom and issues a decree to distribute the tax-rice for peasants in poverty”. This is the first, and so far only such object captured – a fact that is all too evident in the rudimentary nature of the image. I’ll return to this at some stage and re-observe it in light of my growing experience. If nothing else, I’ll need more and longer subs which in turn means a superbly set up telescope. In addition, given that M42 covers a relatively large patch of the sky, 1½ x 1º, and noting the very small field-of-view accessible from my equipment, you’ll appreciate that I’m only able to capture a small proportion of the whole nebula. (The location map on the right is taken from here.)

This is as good a point as any to talk about the tricky business of focusing - tricky because each touch on the telescope's focus wheel sets up vibrations in the image. One effective solution is the use of something called a Bahtinov mask (see here for details) which covers the telescope's objective and creates a diffraction pattern in the eyepiece/camera. The physics behind diffraction patterns need not detain us here, fascinating though it is, since the key point is easy to describe. With the telescope's field of view centred on a reasonably bright star, one adjusts the focus until the arms of the X-shaped lines cross at the star's centre. At that point, the system is focused and the mask may be removed. All one needs is enough starlight to generate a visible pattern: the one in the image above is too bright.

The image above is, I think, of the binary star system ‘Epsilon (ε) Dra (Σ2603)’ in Draco, near the Plough. However, I only think it is … a fact that brings us to yet another problem which needs some sort of solution. I need an accurate idea of where I am looking. There are computer algorithms, called ‘plate resolving software’, which can analyse the stars in an image and provide a precise location – but they won’t operate with the equipment I have because of the limited field-of-view I’ve mentioned before, i.e. there are not enough things in view for the algorithm to work. The same issue pertains to locating individual objects like galaxies or the smaller and more distance nebulae, which is why ‘easy’ targets like the Orion Nebula are the only realistic ones for me at present.

I can’t conclude without mentioning our nearest star, the Sun. Apart from anything else, this is astronomy that can be undertaken without the loss of sleep! For a small outlay, I bought an A4 sheet of specialist solar filter material that blocks 99.999% of the Sun’s light. I glued and duct-taped the major portion onto the ring of a cake mould which was large enough to slip over the front of my telescope, and used most of the rest to make a similar cover for the telescope’s finder scope out of a length of plastic tubing. The mottled appearance to the Sun’s surface is from the huge convection currents that churn through its surface layers. Notice the limits imposed by the small available FoV again. There were no sunspots on the day I tried this out, but one day …

I could easily spend the next season getting improved versions of the above images. Whilst better seeing is down to the atmosphere, I could introduce a more sophisticated setup procedure for the telescope (Polar Alignment is an obvious next step: referencing the initial alignment to Polaris, the Pole Star, about which the night sky rotates) and then collect more/longer subs so as to get an improved final image. However, I want to combine that with an expansion in the list of targets. I still want to work my way through the solar system of course, but there are some Deep Sky objects I’d also like to track down which will survive the limited FoV of my current telescope and camera. After that I shall need to bring out my little contributions ‘money box’ again.

This post is dedicated to Rachel, who wanted to know more – it’s always good to want to know.

Physics 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.