Quantum physics from your (re-usable) cup at Lost Sheep, Canterbury

Coffee in Canterbury, keep cup

Finding the sheep. Lost Sheep coffee in Canterbury. Note the lighting.

I have long been looking forward to trying the Lost Sheep coffee pod in Canterbury. How would the reality compare to the friendly and knowledgable impression they give on social media? Being mostly a take-away outlet, what was their attitude to the disposable coffee cup problem? We had ensured that we had packed our keep-cups when we left London so that we could enjoy a coffee without having to use a disposable cup. Little did we know.

The sheep was visible as we approached the Lost Sheep coffee pod from the direction of the High Street. Adjacent to the pod, people were drinking their coffee while standing at the chip-board standing-bar nearby. In front of us in the queue, another customer was buying what appeared to be his usual coffee in his re-usable cup. The conversation between the customer and barista showing that cafés that help build communities do not have to come in standard formats. ‘Pods’ can work as well as cafés inside buildings (though the Lost Sheep has one of those too over in Ashford). The queue ahead of us enabled us to take more time to study the environment of the Lost Sheep.

Interestingly, a set of ceramic cups were placed above the espresso machine. Although we saw none in use, presumably this means that should you wish to enjoy your coffee at the bars, you can do so, even if you have forgotten your reusable. What a great feature for a take-away coffee place. The friendliness of this café was apparent as I presented my keep-cup for my long black. Commenting on the design of the cup (glass with a cork handling ring, perfect in size for the coffees I mostly drink), we continued to enjoy a short conversation about keep-cups and how nice the size was for the coffee. The coffee was amazingly fruity, a sweet, full bodied brew roasted locally in Whitstable. It was great to be able to enjoy this interesting coffee while wandering as a tourist in my old home-town.

Coffee Canterbury Sheep

Behind the sheep. At least it is easy to spot from all angles.

Before leaving the Sheep though, we did notice the lighting. A yellow hue from the lights immediately above the espresso machine with a whiter, harsher light from the luminescent strip light at the edge of the pod (a dull sunlight surrounding the rest of the outdoor space on this cloudy day). Coals are red hot, the Sun appears more yellow, how does colour vary with temperature? And how does this link to an old story that links quantum physics (very quickly) to your coffee cup.

How things absorb and emit light and electromagnetic radiation has been a subject of study really since white light was split into its different colours and then it was found that there was ‘invisible’ light beyond the blue and far from the red. It was known in the nineteenth century that things (which physicists tend to like to call ‘bodies’ for reasons that become clearer later) that absorbed all the light incident on them re-emitted the light unequally. As they absorbed all the incident light, they could be called a ‘black bodies’. People knew that the radiated light from a black body formed a spectrum that depended upon the temperature of the body. For most things that we encounter on earth, such as the coffee cup, their temperature means that they will emit more strongly in the infra-red, we can feel the heat coming off of them but we can’t see it. But as things get hotter they start to glow ‘red-hot’ and then if we heated them still further, they would glow with different colours.

The stars show this with the colour of the star being an indicator of the temperature of the star. Stars that are very hot shine blue, those that are cooler (but still thousands of degrees Celsius) appear to us as more white. Although these stars are emitting light at all frequencies, they show a characteristic peak in emissions for one frequency. The corresponding “black body spectrum” was very well known in the nineteenth century but the problem was that classical physics just could not explain it. Attempts were made to describe the curve but when it came down to it, if the energy (ie radiation) was described using classical physics, the shape of the curve could not be explained. While classical physics predicted the shape of the curve very well at long wavelengths (reds, infra-reds), there was a failure at shorter wavelengths. And not just a failure, it was a catastrophe: the theory predicted that an infinite amount of energy would be emitted at the low wavelengths. Clearly this is wrong, nothing can emit an infinite amount of energy and so for this reason, the problem was described as the “ultra-violet catastrophe“.

Sun, heat, nuclear fusion

The Sun is our nearest star and source of heat. But what links coffee to the Sun? It turns out a great many things of which this is just one. Image © NSO/AURA/NSF

A solution came when Max Planck changed the assumptions about how energy was emitted or absorbed. Rather than the continuous emission that was expected in classical physics, Planck reasoned that energy was emitted in discrete packets and that, crucially, these “quanta” were dependent on the frequency of the light being emitted. Planck’s formulation allowed for a mathematical description of the curve. Finally the shape of the black body spectrum could be explained, but it came at quite a cost; it came at the expense of classical physics. To use Planck’s formula meant abandoning some aspects of classical physics in favour of a new quantum model and it meant leaving the absolutes of classical mechanics and entering into a new statistical world. This change didn’t come easily even to Planck who had been motivated to study physics by the absolute answers that the theory of thermodynamics seemed to provide. He wrote, regarding his own black body theory:

“… the whole procedure was an act of despair because a theoretical interpretation had to be found at any price, no matter how high that might be”

In some ways, that feeling that you experience while warming your hands on a cup of steaming coffee while basking in the late afternoon sunshine is an intrinsically quantum experience. Neither the infra-red heat of your cup nor the colour spectrum of the sun could be explained using purely classical physics. So while taking time to appreciate the heat of your coffee, perhaps it’s worth remembering that this feeling that you are experiencing comes as a result of the same physics as determines the hot glow of stars and the cold microwave glow of the universe. The coffee heating your hands is indicating that the world is stranger than you may think, a quantum world being revealed to you all the while you sip your coffee.

Lost Sheep coffee is in St George’s Lane, CT1 2SY


Coffee prints at Water Lane Brasserie, Canterbury

coffee in a friendly environment Canterbury

Drinks at Water Lane Brasserie, Canterbury

Making our way down the cobbled High St in Canterbury, into a side street within the old walled town and then following the black board signs for coffee, we found our way to Water Lane Brasserie on Water Lane. Although it is very close to the High St and even the bus station, somehow Water Lane Coffee feels quite hidden. We had decided to try Water Lane for a spot of lunch as we had read good things about the food and coffee. A friendly dog welcomed us into the café where a few groups of people were chatting or working on their laptops.

Various, slightly out of place, ornaments were dotted around the fairly large space. There was the Newton’s cradle in the window, the Fly agaric mushrooms near the sofa seats, the hand grinder and syphon brewer near the counter and, of course, the jenga sets on some of the tables. As various customers came and left, the friendly service suggested that this was a café in which relationships are built along with jenga towers. Corny analogies aside, it may have been tempting to focus a café-physics review on such pieces dotted around. However, it always seems that the more that you contemplate a place, the more rewarding the observations become (to yourself at least, whether they become more interesting to others is quite another matter).

mushrooms at water lane

A Fly agaric (Amanita muscaria) mushroom near the sofas. Learning about how to identify mushrooms is excellent training in noticing.

Our soup, which was indeed a lovely way to enjoy a light lunch meant that we had quite some time to look around the café. Just outside the window, a bird feeding area with hanging bird feeders had somehow attracted an ingenious moorhen that was cleverly balancing on a conveniently placed pole while grabbing food perhaps intended for smaller birds. Inside, punting equipment lined the walls as it seems that you can punt in Canterbury’s river now when it is warmer (is this a new thing? I cannot remember this from years ago when I used to be in Canterbury more regularly). On a shelf above the counter there were several beers with the logo “Canterbury Ales”.

By this time we were enjoying our coffee (long black) and soy hot chocolate. These were a great finish to the soup. Although there was no information about the roaster, the coffee was very drinkable, darker rather than fruity. As we moved the soup away, the indentations on the top of the (old card table) table became more obvious. Rather like footprints in the sand or fossils in London’s Portland stone. Evidence on a table top of coffee-drinkers-past. Could we gain much information from the imprints left on the table top? Firstly, this table has not just been used for playing cards, a fair few plates of food have been placed on it. Secondly, some very heavy small objects, given the shape of the footprint, perhaps vases, have also been put on the table in the past, was this used decoratively? It is difficult to know with any certainty what happened on this table but with a bit of extra information, such fossil footprints can be full of information.

coffee prints at Water Lane

The table top at Water Lane. What can you discern from the indentations that have been left?

When thinking about fossil footprints, as with the table, the first bit of information that can be gleaned from the fossil is the size of the animal (or object) that made them. So even in the absence of a skeleton fossil, it would be known that some dinosaurs were enormous. Last year a set of dinosaur footprints were discovered in Australia that were 1.7m large, a single foot larger than many humans are tall. Then there is the information that can be ascertained from multiple footprints, such as the idea that perhaps dinosaurs hunted in packs or at least, that some dinosaurs such as the Tyrannosaurus Rex moved in small groups, presumably for hunting. Elsewhere, the presence of different types of dinosaur footprints that seemed to move in different patterns suggested a hunt that occurred millions of years ago.

Tristan Gooley in “The Walker’s Guide to Outdoor Clues and Signs” suggests using more recent footprints to see the wildlife stories that have recently unfolded around you when you walk in the country*. He writes:

“Tracking is built upon these simple, logical principles. All four-legged animals lift and replace their feet in a set order and rhythm and this reflects their evolutionary heritage….. It will not be long before you come across two sets of tracks that are clearly related in some way. The two types of tracks, their character, the spaces between them, the habitat, the time of year and a host of other circumstantial evidence will reveal whether an animal was hunting another, scaring it off, playing with it or trying to mate with it. Here, following the track means reading the story.”

Returning from our day dreams and to the table at Water Lane, looking out the window it became apparent that a figure was staring back at us. Standing just on the other side of the river Stour, a short, stout, statue of a monk looked out from under the hedge around the church beyond the river. The old Greyfriars chapel dates from the thirteenth century, the home of the (then recently formed) Franciscans, named after St Francis of Assisi. Details of the history of this place are revealed in old graffiti around the venue. The monk on the river seemed to silently acknowledge the place’s history as the water ran by. What clues as to previous visitors are there in this friendly, quiet and contemplative café on the river Stour? What will be our imprint on the world when we leave it, as individuals, as a society?

Water Lane Brasserie is in Water Lane, Canterbury.

“The Walker’s Guide to Outdoor Clues and Signs” by Tristan Gooley, Hodder & Stoughton, 2014

*Not just the country. In many urban parks you can see the recent behaviour of geese, sea gulls and the dogs that chase them, or walking down a pavement tracking a dog that has just walked through a puddle. Hearing a story from the clues left behind needn’t just be a game left to country walkers and fossil hunters.