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 twitter.com/thinking_bean.

(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."

14) What can smoke detectors tell us about radiation?

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: https://youtu.be/rH4e2aj-DO4. 

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 https://en.wikipedia.org/w/index.php?curid=38068629 - 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.