Categories
Coffee cup science Observations Sustainability/environmental

Stirring up some climate science

Everything is connected. At least, that is part of the premise of Bean Thinking, where the physics of a coffee cup is used to explore the physics of the wider world. So it was great to stumble upon a new connection that I had not previously appreciated¹.

vortices in coffee
Like the vortices behind a spoon dragged through coffee….

The connection is between climate science and that wonderful pastime of pulling a spoon through coffee and watching the vortices form behind it. Yet the research that revealed this connection was not looking for links between coffee and the atmosphere. Instead the researchers were interested in something seemingly (and hopefully) very far from a coffee cup: rogue waves.

Rogue waves are rare and extremely large waves that have been the subject of mariners tales for many years. Nonetheless, it is only relatively recently that they have become the subject of scientific research, partly because they are so rare and so outside our usual experience that they were thought to be the stuff of myth rather than of science. So it is only now that we are developing an understanding of how it can be that, in amongst a number of smaller waves, a massive wave of 20m height can suddenly appear, apparently out of nowhere. One of the groups looking at this problem investigated the effect of a particular sort of (known) instability on a series of waves in water. However, unlike other research groups, this particular study included the effect of the air above the water as well as the waves themselves.

Small waves seen from Lindisfarne
Rogue waves seem to come out of nowhere. A rogue wave can be 2 or 3 times the height of the other waves in the water at the time. How and why do they form?

Although this sounds a simple idea, modelling water waves in air is actually extremely complex. To do so, the authors of the study had to use a computer simulation of the air-water interface. It is not the sort of problem that can be solved analytically, instead the computer has to crunch through the numerical solutions. In order to start to see what was going on with the rogue waves, the authors had to simulate multiple waves of different amplitudes. Each simulation took weeks to perform. Given that this was only a few years ago (the study was published in 2013), you can start to see why people had previously been approximating water waves as waves in water (without worrying too much about the air interface).

Now here is where the link with coffee comes in. The group modelled waves as a function of steepness and found that, above a critical steepness, the wave breaking caused significant interaction between the air and the water layers. In addition to the bubbles that form when waves break, the movement of the air over the breaking wave formed into a vortex which, when it interacted with the back of the wave created an opposite vortex: a vortex dipole “much like the vortices that form behind a spoon dragged through a cup of coffee“.

Rayleigh Benard cells in clouds
The water droplets that form clouds are often ‘seeded’ by particles of salt or dust, such as the aerosols distributed by the vortices in this wave study. Image shows clouds above the Pacific. Image NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response

Just as with the vortices in the coffee cup, vortices were forming in the air behind the wave crest (which acted as the spoon) and travelled upwards through the atmosphere and away from the waves. As each wave broke, a train of vortex dipoles were produced that twirled off into the sky. Imagine a coffee bath and multiple spoons rather than a coffee cup. The authors suggested that these vortices could carry aerosols from the sea (salt, water droplets etc) into the atmosphere. Travelling within the vortices, these tiny particles could travel far further and far higher than we may have expected otherwise. Such aerosols can be critical for cloud formation and so the effect of these breaking waves could be important for climate modelling.

While an undergraduate, I had an opportunity to study a course in atmospheric physics. I remember the lecturer lamenting that while we (as a community, but not really as the students sitting in the lecture theatre at that time) understood atmospheric modelling quite well and that we understood how to model the oceans fairly well, we got problems when we tried to put the two sets of models together. It was clear that something wasn’t quite right. Years later, it seems that at least past of the reason for that is linked to those vortices that you see as you pull your spoon through your coffee cup.

Everything is connected indeed.

A summary of the study can be found here. The abstract (and link to the pdf) of the published paper can be found here. If you do not have access to the journal through a library, an early, but free, version of the paper is here – note though that this version may not include the amendments included after peer review.

 

¹A quote attributed to Jean-Baptiste Biot (1774-1862), is perhaps relevant here “Nothing is so easy to see than what has been found yesterday, and nothing more difficult than what will be found tomorrow.”

Categories
Coffee review General Observations Science history

Some perspective at Over Under, Earls Court

Over Under Coffee Earls Court
Follow the arrow! Over Under Coffee in Earls Court.

Whenever I’m heading somewhere that I haven’t been to for a while, I check the London’s Best Coffee app to see if any new cafés have popped up in the area since my last visit. So when I was in Earls Court recently, I was very happy to be alerted to a new café on the map with a review by Beanthereat.

Over Under Coffee is at 181A Earls Court Road but is tucked around the corner from the main road and so thank goodness for the helpful arrow (and the map which told me I should be on top of it). Once found, we ordered coffee and banana bread and took a table to sit down. The friendly staff behind the counter were quite confident of the ingredients in the banana bread as it is made locally by a lady in Fulham (whose name I have sadly forgotten). The coffee and banana bread formed a great combination for a mid-morning snack. Coffee is roasted by Assembly roasters over in Brixton and came with lovely interference patterns in the bubbles on the surface together with dancing white mists, which never fail to fascinate me.

On the table next to ours was a small Kilner jar for sugar and two succulent plants. The Kilner reminded me of the use of air valves in coffee packaging (which are non-recyclable plastic) and the interesting experiment by Roasting House coffee roasters to investigate whether they are actually needed for freshly roasted coffee (which you can read about here). However it was a picture above the table that prompted the thought-train for today’s Daily Grind. A charcoal sketch, the picture featured a tree in the foreground with a fence behind it. From a very early age we are taught how to represent 3D objects on a 2D sheet of paper, the idea of perspective seems ingrained on our minds. But how intuitive is it really?

perspective in coffee
A picture at Over Under. Note the smaller reflections of the (more distant) light fittings.

Although the ancient Greek artists could convey an idea of depth in their art, the development of a mathematical understanding of perspective only came with Filippo Brunelleschi (1377-1446), although a written account of the mathematics of perspective did not arrive until Leon Battista Alberti (1404-1472). Alberti’s method for drawing in perspective used not just a vanishing point, but an additional diagonal vanishing point in order to construct a sense of depth and an accurate depiction of perspective (a description of Alberti’s method is here). The development of the understanding of perspective during the Renaissance meant that for some paintings, the ‘viewing depth’ can actually be calculated, while other artworks managed to create optical illusions whereby objects would jump out at the viewer as if they are in 3D. Works such as Andrea Pozzo’s ceiling in the chiesa di Sant’Ignazio in which a flat ceiling appears magnificently domed. Or, closer to home,  Samuel van Hoogstraten’s work in the National Gallery in London in which the viewer looks through a peep hole to see the interior of a house complete with a dog that appears to be sitting up inside the painting. Such paintings required a knowledge of the mathematical rules behind the depiction of perspective. Isn’t it surprising that the understanding of these rules is so recent?

Over Under Earls Court
Coffee with bubbles showing interference patterns at Over Under Coffee

Another art work with an interesting use of perspective that will bring us, in some way, back to Over Under Coffee is Raphael’s fresco “School of Athens“. The two figures of Plato and Aristotle stand at the centre of a diverse group of philosophers including Socrates, Zoroaster, Euclid, Diogenes the Cynic and, possibly, an image of Hypatia of Alexandria. Although the use of perspective for the architecture draws your eye towards the centre of the picture, two spheres (held by Zoroaster and Ptolemy) on the right hand side of the picture are drawn as circles rather than ellipses. Spheres viewed from an angle should be represented as ellipses if drawn correctly according to the rules of perspective. Did Raphael make an error in perspective (that may work better for our eyes?) or is the degree to which these two spheres are distorted within the limits of the fresco brush and so not visible in the picture? An episode of Radio 4’s In Our Time discusses this picture at length including a deep conversation about the significance of Plato pointing upwards towards the heavens and Aristotle indicating towards the Earth. Plato’s wisdom and Aristotle’s knowledge, above and below, much like the weave logo that brings us back to Over Under Coffee.

Over Under Coffee can be found at 181A Earls Court Road, SW5 9RB.

 

 

Categories
Coffee cup science Home experiments Observations

Biscuit Crystals

biscuits gone wrong, crystals in the oven
Expanding biscuits are a 2D example of a close packed crystal lattice.

Blaise Pascal once wrote of the benefits of contemplating the vast, “infinite sphere”, of Nature before considering the opposite infinity, that of the minute¹. And although the subject of today’s Daily Grind involves neither infinitesimally small nor infinitely large, a consideration of biscuits and coffee can, I think lead to what Pascal described as “wonder” at the science of the very small and the fairly large.

The problem was that my biscuits went wrong. Fiddling about with the recipe had resulted in the biscuit dough expanding along the tray as the biscuits cooked. Each dough ball collapsed into a squashed mass of biscuit, each expanding until it was stopped by the tray-wall or the other biscuits in the tray. When the biscuits came out of the oven they were no longer biscuits in the plural but one big biscuit stretched across the tray. However looking at them more closely, it was clear that each biscuit had retained some of its identity and the super-biscuit was not really just one big biscuit but instead a 2D crystal of biscuits. The biscuits had formed a hexagonal lattice. For roughly circular elements (such as biscuits), this is the most efficient way to fill a space, as you may notice if you try to efficiently cut pie-circles out of pastry.

salt crystals
Salt crystals. Note the shape and the edges seem cuboid.

Of course, what we see in 2D has analogues in 3D (how do oranges stack in a box?) and what happens on the length scale of biscuits and oranges happens on smaller length scales too from coffee beans to atoms. Each atom stacking up like oranges in a box (or indeed coffee beans), to form regular, repeating structures known as crystal structures. To be described as a crystal, there has to be an atomic arrangement that repeats in a regular pattern. For oranges in a box, this could be what is known as “body centred cubic”, where the repeating unit is made up of 8 oranges that occupy the corners of a cube with one in the centre. Other repeating units could be hexagonal or tetragonal. It turns out that, in 3D, there are 14 possible such repeating units. Each of the crystals that you find in nature, from salt to sugar to chocolate and diamond can be described by one of these 14 basic crystal types. The type of crystal then determines the shape of the macroscopic object. Salt flakes that we sprinkle on our lunch for example are often cubic because of the underlying cubic structure on the atomic scale. Snowflakes have 6-fold symmetry because of the underlying hexagonal structure of ice.

It is possible to grow your own salt and sugar crystals. My initial experiments have not yet worked out well, but, if and when they do, expect a video (sped up of course!). In the meantime, perhaps we could take Pascal’s advice and wonder at the very (though not infinitesimally) small and biscuits. And if you’re wondering about where coffee comes into this? How better to contemplate your biscuit crystals than with a steaming mug of freshly brewed coffee?

¹Blaise Pascal, Pensées, XV 199

Categories
Allergy friendly Coffee review General Observations Science history

Thinking space at Le Peche Mignon

Coffee in Le Peche Mignon, Highbury, Islington
Le Peche Mignon in Highbury, hidden down a side street.

It was a balmy February morning when I met an old friend at Le Péché Mignon on Ronalds Road near Highbury and Islington. I had first come across Le Péché Mignon a few months ago when I had had a lovely coffee (and a great cake, I remember the staff being very helpful to check the ingredients for my nut allergy) but too little time to properly think about the space. So, when the opportunity arose to meet a friend (who I have known since we were both 5 but haven’t seen for many years) near Islington, I jumped at the opportunity to meet there.

This small but delightful café seems to be very popular. Both the bench seat in the window (where I had sat last time) and the long, sharing-table in the middle of the café were practically full by the time we arrived in the mid-morning. Fortunately, there was plenty of space in the quiet garden at the back for us to catch up for a couple of hours (and a couple of coffees!). The coffee is roasted by Monmouth, the Americano was very well done and there were quite a selection of pastries and salads on offer. One wall of the café was lined with bottles of wine while Carambars were available to purchase next to the counter.

brick wall at Le Peche Mignon
A join between two brick walls at Le Peche Mignon. How exactly are bricks made and why are they made that way?

The garden behind the café had plenty of tables and, even though it was February, it was warm enough for us to sit comfortably outside. One of the walls of the garden was formed by two sets of brick walls that had a join between them. The appearance of a separation between the walls, together with the weather, reminded me of the crack and the imminent demise of the Larson C ice shelf. However as this was probably too close to recent posts about climate change, I started thinking about defect structures in crystals instead. While pondering this though, my thoughts turned to an entirely different subject matter, the unusual toilet at Le Péché Mignon.

Just as the toilets in our old primary school, the toilet at Le Péché Mignon is outside, in the garden. This got us reminiscing about our old primary school which, during winter, regularly closed when the outside toilets froze (hopefully not a problem for the toilets at Le Péché Mignon!). And while the school has undergone significant renovation since then, it does get you thinking about the history (and engineering/science) of toilets. While this may seem an unpleasant subject for, what is after all a café review, please do bear with me because thinking about toilets can lead to surprising connections. For example, a recent New Yorker article about confirmation bias featured quite a discussion on toilets. How? It seems that while people generally tend to think that they understand how a toilet flush works, when asked to explain it step by step, they suddenly become far less confident. Our knowledge is not so great as we tend to think it is.

cup of coffee in Le Peche Mignon
From coffee cups to aeroplanes, the hardness and porosity of materials depends on the temperature that the starting materials were ‘baked’ at.

Which brings me back to Le Péché Mignon. The issue of flushing toilets became a problem for London in the mid-nineteenth century when the introduction of the “water closet” increased the volume of water flowing into the rather inadequate sewage system (if you are interested in the history of the toilet you can click here). The great engineer Joseph Bazalgette (1819-91) was commissioned to design and build London’s sewer system in which a network of tunnels were built across the capital. Bazalgette’s northern branch lies about 5 minutes walk north of Le Péché Mignon and runs from Hampstead Heath to Old Ford in Stratford. A distance of just 9 miles (14.4 Km), this particular tunnel has a remarkably steep gradient dropping at least 4feet (1.2m) every mile (1.6 Km). Imagine water flowing down a plug hole. The turbulence and speed of the water (ahem) flowing down this ‘drain’ means that Bazalgette had to think very carefully about how he lined this particular tunnel. If he had used ordinary bricks, such as those that make up the wall around the café’s garden, they would have eroded quickly with the turbulent motion of the water. Consequently, Bazalgette specified Staffordshire Blue bricks¹ to line this tunnel. During the manufacturing process, Staffordshire Blue bricks are baked at very high temperature (and in a low oxygen atmosphere) making them particularly resistant to erosion and to water absorption. It should not surprise us that the hardness, brittleness and texture of materials should be affected by the temperature at which they are formed after all, great care is taken about the temperatures at which chocolate is melted and allowed to re-solidify. Indeed, a vast amount of research is done to understand how different materials (from ceramics to metals) respond under different heat treatments. This research is important for applications as diverse as the walls of sewer tunnels to the design of aeroplanes. And, of course, to the design of better coffee cups, a thought with which we can return to thinking about this great little café.

Le Péché Mignon can be found at 6 Roland’s Road, N5 1XH

¹”The Great Stink of London…” Stephen Halliday, Sutton, 1999

 

 

http://www.plumbing-geek.com/howdoesatoiletwork.html

http://www.baus.org.uk/museum/164/the_flush_toilet

Categories
Observations Science history Sustainability/environmental Tea

A language problem?

Bob Ward, Obama quote, climate change
The last generation: our urgent need to communicate effectively.

The beverage was prepared by pushing water (at 94ºC and 1.0 MPa) through a pellet of coffee beans ground to an average of 10 – 100 μm diameter. The pellet had been compacted (“tamped”) using a variable pressure as described in ref [1]. Following a manual transfer of the cup to the table, the drink was consumed at a temperature of 55ºC. Fruity overtones were noted.

Would you rush to try this coffee?

Last week I wrote about the effects of climate change on coffee and how climate scientists are trying to reach out and communicate more about the science behind global warming. But there was a crucial question left un-answered, just how do we communicate? Do we all speak the same language or is the dry impersonal prose of science a hindrance to discussion?

To start with the encouraging news. It turns out that scientists are a pretty trusted bunch. In a recent survey 79% of the British public trusted scientists to tell the truth (compared with 21% for politicians). Part of the problem for politicians may be the language that they tend to use, “if I am honest…”, “to be fair…” etc, are apparently statements that haemorrhage trust. These are not statements that you will hear made by scientists. The language of science is cold and dry, utterly devoid of the personal. So, coupled with the results of the survey, it is tempting to think that we should continue to use our cold and impersonal language when communicating things like climate change. It seems that this works.

Steam, scattering, colour
How would you describe your coffee? Do those who read your description read it in the sense that you wrote it?

Only we would be wrong, the language that we use is (apparently) not helping us to communicate and we need to change it (as the meeting was told in an impassioned talk by Bob Ward). An average scientific paper for example is designed to convey exactly what we did, how we did it and to eliminate any possible element of confusion. Ideally, we would write a scientific paper so that someone else could read it, understand precisely what we have done and repeat the experiment under very similar conditions. In this context, our dry language can work very well but does it work generally when communicating results more widely?

To see the problem, compare the (scientifically written) coffee review that started this article with an extract from a recent review of Silhouette Cheapside by Brian’s coffee spot:

The coffee offering’s simple: there’s a single-origin espresso from Notes, a Brazilian Cachoeirinha during my visit. As an espresso this was gorgeous: fruity and complex, it rewarded me with every sip, holding its own right to the end. I also tried it as a flat white, which was very smooth and surprisingly different, the coffee and milk perfectly complimenting each other.

A visit to Cheapside may be imminent.

So this is the problem, while the scientific language may convey accurately what was consumed, it can’t convey it fully. Language that communicates more generally includes details about how we feel: “gorgeous”, “rewarded me with every sip”, “surprisingly different”. The language used in Brian’s coffee spot in no way detracts from an accurate description of the espresso or the flat white. Arguably your idea of the drinks that Brian sampled at Silhouette is far better formed in your mind than the idea of the espresso described by the scientific-language description at the start of this post. Can we extend this reasoning to scientific descriptions of the science of climate change and its likely effects?

Earth from space, South America, coffee
Our common home.
The Blue Marble, Credit, NASA: Image created by Reto Stockli with the help of Alan Nelson, under the leadership of Fritz Hasler

Perhaps you could imagine yourself in the position of a climate scientist: your research is showing you that the planet that you live on is likely to suffer significant change as a result of something that we humans are doing but can also do something about. I would guess that you are likely to get quite worked up about it. Wouldn’t it come across better if scientists were to use some of that emotion in how they communicate? Wouldn’t it convey our meaning more effectively?

Immediately though we come up against this issue of trust. Does the cold and dry scientific language somehow better communicate that the argument is evidence based? In this line of reasoning, subjective descriptions would be ok for things like describing a good coffee but not ok for describing climate change. And yet I can’t help feel that even here there is a problem. The philosopher of science Michael Polanyi argued that “Fairness in discussion has been defined as an attempt at objectivity, i.e. preference for truth even at the expense in losing force of argument”. Our “preference for truth” must include the fact that we have an emotional investment in the argument. It is our planet that we are destroying. Indeed, attempts to hide this emotional investment may even lead others to suspect climate scientists of other, more nefarious, secondary motives (financial gain, global conspiracy). However there is an important caveat on Polanyi’s argument, he writes: “[f]airness and tolerance can hardly be maintained in a public contest unless its audience appreciates candour and moderation and can resist false oratory…”.

screenshot of tweet from Digitalnun
A thought provoking tweet from @Digitalnun – science communication goes both ways.

Which brings me to a last point. A recent tweet by Digitalnun posed a question on related lines: does careless reading or careless writing lead to more problems? What we write is not necessarily what people read and if we allow emotion to enter into the cold language of science then we may increase the likelihood of misinterpretation (whether deliberate or not). Will those who read our attempts to communicate science with full honesty be able to resist false oratory, twisting our words to imply a ‘war’ or financial interest? Which is more appropriate, to remain dispassionate and potentially unconvincing or to be more honest in our discussion at the possible expense of losing trust? It’s not a question which seems to have an easy answer. What do you think? Do scientists have a language problem? Would you trust a discussion on climate change more or less if you thought that the scientist actually cared about the planet too? Let me know, either in the comments below, on Facebook or on Twitter.

[1] is hyperlinked above but if you are in the habit of scrolling down to look at the references, you can find the article about tamping in “coffee research” published here.

The Polanyi quotes are from “Science, Faith and Society” by Michael Polanyi, University of Chicago Press, 1964 (2nd edition)