physics

Reflections on physics and coffee

BeanThinking started as a way of slowing down and appreciating connections, often between a coffee and the physics of the wider world but also in terms of what can be noticed in any café. Perhaps, for this first post of 2017, it’s worth spending five minutes looking at your coffee while you drink it to see what you notice. Here are a few coffee connections that occurred to me recently:

reflections, surface tension

Reflections on a coffee.

Parallel lines and surface reflection: The parallel lines on the ceiling of a café were reflected in a long black. Surface tension effects on the coffee meant that the reflections were curved and not at all parallel. A piece of dust on the surface of the coffee was revealed in the reflection by the curved reflections of the ceiling. Astronomers can use similar effects (where images of a star appear in a different location to that expected) to infer the presence of dark objects between distant stars and their telescope. This gravitational lensing can be used to detect quasars or clusters of galaxies.

 

 

 

layering of coffee long black

Layers of coffee

Layering of crema as the coffee is consumed: The coffee stain effect and this layering of the crema suggests a connection between a coffee cup and geology. It used to be my habit to take a mug of tea with me when I taught small groups of undergraduates. In the course of one of these tutorials, a student (who had been observing similar layering in my tea mug) said, “You drink your tea faster when it is cooler than when it is hot”. Full marks for observation, but not sure what it said about his attention during my tutorials! Similar observations though can help geologists estimate the age of different fossils.

 

interference patterns on coffee

Bubbles in coffee

Bubble reflections: An old one but the interference patterns caused by bubbles on the surface of the coffee are full of fascinating physics. The fact that the bubbles are at the side of the cup and seem to be grouped into clusters of bubbles may also be connected with surface tension effects (although there is a piece of weather lore that connects the position of the bubbles to the weather. If anyone ever does any experiments to investigate this particular lore, I’d love to hear about them).

 

 

Coffee, Van Gogh

Art in a coffee cup

Van Gogh’s Starry Night: The effects of vortices and turbulence caused the crema of a black coffee to swirl into patterns reminiscent of this famous painting by Van Gogh. As a result of posting this image on Twitter, @imthursty sent me a link to this preprint of a paper submitted to the arxiv: the connections between Van Gogh’s work and turbulence. A great piece of coffee combining with art and science.

 

So many connections can be made between tea, coffee and science and the wider world, I’d love to see the connections that other people make. So, if you see some interesting physics, science or connections in your coffee cup, why not email me, or contact me via FB or Twitter.

 

Time for a slow coffee?

enamel mug, teh halia, Straits Times kopitiam

This enamel mug connected glass to the Giants Causeway (Straits Times kopitiam)

Every two weeks, the Daily Grind on Bean Thinking is devoted to what I have called a cafe-physics review. The point of these reviews is to visit a café, slow down and notice what has been going on in a cafe physics-wise. I focus on physics because it is my ‘specialist’ area but the point is to notice the connections between the coffee, or the cafe and the world around us. To see how what is going on in your mug is reflected in the science of the wider universe. Realising that things that seem disparate are in fact connected: It is the same maths that describes electrons moving in a metal and the vibrations on the surface of a cup of coffee. That sort of connection to me is mind boggling. Yet there is more. Thinking about the connections between physics and coffee can lead to meditations on the environment and sustainability, or considerations about how our attitude to drinking coffee changes our perception of it.

Everything is connected.

Parquet floor at Coffee Affair

How many people have walked on this floor? The story of evolution at Coffee Affair

It is my strong belief that whenever we go into a cafe, order a coffee and then proceed to sit down with our smart phones or tablets and check our e-mail or our Twitter accounts we lose a fantastic opportunity. It is the opportunity to be properly present and to notice what is going on around us. It is the opportunity to slow down and to appreciate what life has given us and the surprising things that the world has to offer. To look at the beauty and the complexity of the world and to say ‘wow’.

This appreciation is open to us all, provided we seize the opportunity to slow down and take that time to enjoy our coffee.

So, this week’s Daily Grind is an invitation. It is an invitation open to anyone who sits down with a coffee. If you notice anything peculiar, or interesting, that you feel deserves a mention as a cafe-physics review why not write an edition of the Daily Grind? It does not matter where in the world you are or what your level of science knowledge is. If a full Daily Grind article is too much but you have a great observation, write a paragraph review of your favourite cafe and I’ll add it to the cafe-physics review map. Think that you don’t know enough science? Never mind, share your idea with me and we can work on it together.

Hasten coffee, long black, black coffee, espresso base

Sometimes the link with physics/science is a little bit tenuous, as it was at Espresso Base

Your observations need not be physics-based. It would be great if it is based on some aspect of science, but, as past examples have shown, this link can be a little tenuous if the cafe/subject warrants it.

So, over to you. I hope that someone will respond to this invitation. Please do contact me if you would like to pen a review or if you have any questions. It is my hope that you are all enjoying such great coffee in the huge variety of cafe’s that we now have that there will be plenty of opportunities for people to slow down and to notice and then to share it with the Daily Grind.

Please contact me here, or in the comments section below. I look forward to hearing from you.

 

Some brief guidelines for a cafe-physics review:

1) The cafe should, preferably, be a good independent.

2) Any science/history etc. needs to be verifiable but, as mentioned, if you’ve noticed something great but are unsure of the science, get in touch and we’ll work something out together.

3) If you have noticed something fascinating with your coffee but at home and not in a café, contact me anyway.

4) Please do not write a cafe-physics review of any cafe you are financially associated with. I will have to refuse/delete any ‘reviews’ that I find are adverts.

Musical Coffee

Tasting notes from Finca San Cayetano coffee

Tasting notes from Hasbean’s Finca San Cayetano coffee

A few weeks ago, I chanced upon an article “Listening to Stars Twinkle” (link) via Mr Gluckin on Twitter. At very nearly the same time, I received in the post, a new coffee from Hasbean (link) which suggested an entertaining coffee (see pic).  A perfect time to have some fun with coffee, I think.

The article was about ‘stellar seismology’: Understanding the inside of a star by watching sound travel through it. We know from daily experience that the way sound travels through air depends on the temperature of the atmosphere.  Sounds can appear to travel further on cold evenings than on warm nights for example (for an explanation of this effect click here). Conventional seismology on earth uses the same principles. By measuring how sound is deflected as it travels through the earth, geologists can work out the type of rock in the interior of the earth (and whether the rock is solid or molten).

Burmese bell, resonating bells, stars

A bell rings with a note that depends on the composition (bronze) and shape of the bell. © Trustees of the British Museum

Unlike these earthly examples though, ‘listening’ to a star is not so easy.  We cannot hear stars vibrate as sound travels through them. We can only view them from a distance.  It is therefore very fortunate that the surface of a star will start to move noticeably as the sound travelling through the star hits one of the star’s ‘resonances’. Just as a bell has a tone depending on its shape and what it is made of, so a star has a series of ‘notes’ that depend on the composition and temperature of the star. These ‘notes’ are the star’s resonances and we can find out what they are by watching the different patterns on the star’s surface. Each resonance has a distinct, signature pattern which is dependent on the ‘tone’ of the resonance, much like the patterns you can see on the surface of a coffee by dragging a take-away cup across a table. The temperature and composition of the interior of the star determine the ‘notes’ of the resonances and so, by looking at the surface vibrate we can work out what is inside a star.

Can we illustrate this with a cup of coffee?  Of course we had fun trying.

In the video, the hot coffee is poured into a take-away cup that I have previously made into a loud speaker.  In the next few days I will upload details of the making of the speaker onto the Daily Grind. Hooking up the speaker to my phone, I could easily play music through the cup (and through the coffee).  But by connecting the cup-speaker to the phone with a tone generator app installed (free and downloadable from the app store for iPhones and probably similar for Android phones) I could generate single ‘notes’ through the speaker from 1Hz to 20 kHz.  Our ears are only sensitive to frequencies from approximately 20 Hz-20 kHz so below 20 Hz we cannot hear the notes being played.

home made loud speaker, coffee cup, kitchen table physics

The coffee cup speaker in an improved design

Nonetheless between 12 and 13 Hz, the surface of the coffee started to show a lot of movement. Although the distinct patterns of a resonance could not be seen (perhaps the speaker, lighting or other experimental conditions needed optimising), we can clearly see the coffee resonate as the surface is vibrating so strongly at these frequencies. As the tone was changed to down to 10Hz or up to 14Hz, the vibrations faded. The ‘resonance’ of the hot coffee filled cup-speaker was 12-13 Hz.  If the cup were to be filled with yoghurt or only half filled, we would expect the ‘note’ at which the surface vibrated to change. Indeed, in this latter case, I could no longer find the resonance anywhere near 12-13 Hz.

‘Listening’ to the coffee by watching its surface means that we can, in principle, work out the properties of the coffee, its temperature, density etc.  And it is in this way that we ‘listen’ to stars ‘twinkle’ so as to understand our universe more.  So thank you MrGluckin and Hasbean for providing an entertaining couple of weeks for me!  Please try this at home and let me know what you discover in the comments section below.

Important Disclaimer: No coffee was wasted in this experiment! I had already finished drinking the contents of the cafetiere and just used the old grounds to provide the ‘coffee’ in the video.

Extra thanks: Becky Ramotowski and Gardensafari.net for the photos. The photos from Garden Safari are © www.gardensafari.net

Introducing Bean thinking

As this is the first true blog post, let’s do the introductions. What is Bean thinking and who is @thinking_bean?

Breakfast coffee, introductionThe human bean behind @thinking_bean has worked for a fair few years in university research centres, researching obscure but fascinating areas of physics where magnetism meets superconductivity. Such research fields can be very beautiful but perhaps not of immediate technological relevance. Understandably, this can cause some in our society to question the utility of investigating these phenomena. Part of the motivation behind Bean thinking is to explore this question, why do we do science?

A second motivation is to share the wonder of the world that today’s understanding of physics gives us. Some of these beautiful areas have not yet been fully understood even though they occur in something as apparently simple as a coffee cup. Through teaching, outreach, talking to friends and even in conversations with some colleagues, I became aware of the way that science, perhaps particularly physics, can be perceived as a very interesting, but perhaps very difficult subject, far removed from people’s everyday lives.

Yet this is not true! Slow down, put down your smart phone, e-book or tablet, observe the world. Physics is all around you. Warming your hands around a mug of hot coffee, you may not realise how it is related to the Big Bang. Looking at a glass of milk can illustrate the reasons that the sky is blue. Even the mere act of stirring coffee can be related the Heathrow minute (link, link2).

Hence Bean thinking, which hopefully will become a space where curious individuals can come and discuss interesting phenomena that they notice in the day to day. If this can be done with a cup of coffee, all the better. The point is to slow down and start noticing. Each Wednesday I will update the Bean thinking blog, the “Daily Grind” with things that I have noticed or that I find interesting. Who knows, if anyone starts to read this and shares their observations perhaps the Daily Grind can also include these. As this website develops, I may add a forum, but for the moment, please let me know what you think about the concept and what you observe around you in the comments section below.