Categories
General Science history slow

Ghosts of Christmas Past, the Devereux

Grecian, Coffee House, London Coffee House
The Devereux now stands where the Grecian once was

The Grecian is steeped in history. One of London’s early Coffee Houses, it counted Isaac Newton and Edmond Halley among its regulars. Today it is the site of a pub, “The Devereux“, owned by Taylor-Walker. The building itself dates from the nineteenth century though it is on the site of the old Grecian (a drawing of which can be seen on a wall inside the pub). In a sense, the Devereux is a continuation of the Grecian that once existed on this spot and it is for this reason that I’ve wanted to enjoy a drink at the Devereux/Grecian for a long time. What better time to do it than for a Christmas themed cafe-physics review?

The Devereux itself is a fairly spacious, comfortable pub, tucked down a little alley just off Fleet Street. It is strange to consider (while sipping on a glass of the 1730 pale ale) that it was here, just over 300 years ago, that the Grecian would host the after-meeting “pub outing” of the (then newly formed) Royal Society. Paintings and photographs of the Grecian and the Fleet St. area surround you, as you sit and enjoy your drink (they do serve tea and coffee too). Indeed, it is possible to almost feel the history of this place. I recalled reading a 1686 paper in the Philosophical Transactions by Edmund Halley in which he described a live demonstration, in front of a meeting of the Royal Society, of just how much water could evaporate from a heated plate of water in two hours. Halley was interested in this as part of the whole question of how rivers formed and where rain came from. I wondered whether Halley and his friends Newton and Sloane, retired to the Grecian after that meeting and sipped on hot coffee as they sat next to the cold windows which started to steam up on the inside.

Vegetable Lamb, Lamb of Tartary
The Vegetable Lamb in the collection of The Garden Museum

Reading about these early frequenters of this drinking establishment, it is hard to avoid the impression that they were driven by an interest in knowledge and knowing things. Of course the term ‘scientist’ had not yet been invented*. Science as in ‘scientia’ was still just Latin for knowledge, the men who gathered at the Grecian (and they were mostly men) were not “scientists” they were Natural Philosophers. Hans Sloane, another regular, was a great collector, finding curiosities from around the world and displaying them in his house. Most of his collection became the start of the British Museum but there is one curiosity of Sloane’s that I came across recently that is not to be found there at all and that is his “Vegetable Lamb”.

Vegetable Lambs were believed, in the seventeenth century to be, genuinely, part vegetable part animal. You can see from the photo that they do look fairly animal-like. According to the Garden Museum, these vegetable lambs originated in the Far East but now only two remain in the UK. The one that belonged to Hans Sloane (which is in the Natural History Museum) and the one that belonged to John Tradescant and that can now be found in the Garden Museum (now sadly closed until refurbishment is complete in 2017). Hans Sloane’s contribution was to show that this vege-animal was in fact purely a plant, a type of fern, which may make vegetarians everywhere breathe a sigh of relief. It was because these people were interested that they worked so hard in trying to understand the world around them. Which brings us, somewhat surprisingly, to one of the more recent famous patrons of what had by that time become, the Devereux.

Chesterton
The festive Chesterton bookshelf at the Devereux

GK Chesterton is not known for his scientific research. However, he did spend a great deal of time thinking and writing about all sorts of things. (It also appears that he spent a fair amount of time in the Devereux where there is an entire bookshelf of his books). A book of Chesterton’s essays “As I was saying” was published in the year of his death, 1936. Within that book is an essay “About the Telephone”. Chesterton was musing on a sentence that he had read in a newspaper that had troubled him: “The time will come when communicating with the remote stars will seem to us as ordinary as answering the telephone”. Chesterton wrote “Now if you could say to me: ‘The time will come when answering the telephone will seem to us as extraordinary as communicating with the remote stars…’ then I should admit that you were a real, hearty, hopeful, encouraging progressive.” I suspect that with our tendency today towards the fragmentation of knowledge and increasing specialisation, we would categorise the work of Newton and Halley, Sloane and then Chesterton in quite different compartments. Yet it seems to me that they share something in their work: an element of wonder and curiosity at the world. As Chesterton continued in “About The Telephone”,  I am not objecting to the statement that the science of the modern world is wonderful; I am objecting to the modern world because it does not wonder at it.

It sometimes seems hard for us to sit in a cafe on our own without using, or at least looking at, our telephones. Checking our email or the latest news on our telephones has become extraordinarily ordinary for us. Maybe this should be our New Year’s resolution: put our phone back into our pocket and consider, with Chesterton, Sloane, Halley and Newton, just how wonderful it is.

Happy Christmas & New Year to all

 

* The word science/scientist was first used in the sense that we now understand it by William Whewell in the nineteenth century.

“As I was Saying – a book of Essays by GK Chesterton” was published by Methuen&Co Ltd, 1936

The Devereux can be found in Devereux Court, just off Fleet Street, WC2R 3JJ

Categories
Home experiments Observations slow Tea

Coffee baubles

resonating coffee
Not the best image of a resonating coffee but you hopefully get the idea

Most people, at some point in their lives, must have pushed a take-away coffee cup across a table and watched as patterns form on the liquid surface. Sometimes these patterns seem to stand still, we’d say that they form ‘resonances’. On even rarer occasions, on dragging your cup across the surface, you may have seen coffee droplets jump out of the coffee and then dance on the coffee surface for a couple of seconds as the liquid vibrates.

Today’s Daily Grind investigates these ‘floating droplets’ with an experiment in time for Christmas: Decorate your coffee with coffee baubles.

To make these droplets form on your coffee in a controllable way you will need a few bits of equipment:

  1. A couple of loud-speakers with the woofers exposed
  2. Some sort of liquid soap (washing up liquid, hand soap, soap for hand washing clothes etc)
  3. Some water (or coffee but you will do horrible things to it)
  4. A shallow dish (I used the bottom of an old yoghurt pot)
  5. A “dropper”, a pipette or syringe would be ideal, a straw will probably work.

You can do this completely systematically, in which case you’ll also need a signal generator to provide a fixed frequency output to the speakers (I used “ScorpionZZZ’s Lab, Signal Generator Lite for iPhone). Or you can just go straight to the fun bit which is to make these droplets dance to music. It’s Christmas so it’s entirely up to you!

floating drops, resonances, speakers, kitchen top science
Balance a shallow dish on the woofer of a speaker. A roll of sellotape can be used to couple the vibrations of the speaker to the dish if necessary.

Balance your speakers on a flat surface and put the shallow dish so that it sits in good contact with the woofer. Because my dish was ever so slightly larger than the vibrating bit of the speaker, I ‘coupled’ the speaker to the dish with a roll of sellotape. Mix 10ml of soap with 100ml of water (this does not have to be exact but you may want to investigate just how much/little soap you can get away with). If you are using coffee rather than water, you will need to mix 10ml soap with 100ml coffee.

Pour about half the soapy-water into the dish and then turn the speakers on. If you are using a signal generator, watch what happens as you sweep the frequency from 10-200 Hz. Now, either choose a frequency which shows a nice resonance pattern on the water, or start playing the music through the speakers. Music with a good beat will work well (I watched drops dance to Tiesto, Blondie, and Josh Woodward’s “coffee”).

Drip a drop of the remaining soapy-water onto the resonating surface. A video of my playing with these droplets can be seen above. Although not all the drops will float, it is fairly easy to start to form patterns of flowers or rows of droplets and then it’s worth just playing.  How big a droplet can be made to float without collapsing? How many minutes can you get a drop to last before it sinks? What happens if you combine a drop of black (soapy) coffee with a drop of milky (soapy) coffee?

Have fun, and please do share your videos and photos of your experiments with me on Facebook or Twitter.

Disclaimers & Credits:

No coffee was wasted in the making of this video. A very good coffee from Roasting House was thoroughly enjoyed before the remnants were diluted and mixed with soap.

Inspiration & experimental details taken from Jearl Walker’s great article “The Amateur Scientist” in Scientific American, p. 151 (1978).

 

Categories
cafe with good nut knowledge Coffee review Science history

Hanging out at J+A Cafe, Clerkenwell

Exterior of J and A cafe (the bar is on the other side of the passageway)
Exterior of J and A cafe (the bar is on the other side of the passageway)

Tucked down a little alley, in the back streets of Clerkenwell is the J+A Cafe. Not just a cafe, but also a bar, J+A is a satisfying place to find, particularly if you happen to find it serendipitously. As you head down the alley, the café is on your right whereas the bar opens up on your left. The café is simply furnished, with bare brick walls adorned with a few impressionist paintings. There are plenty of seats at which to enjoy good coffee and home-made cake. Their website suggests that J+A specialise in Irish baking and so we dutifully had a slice of Guinness and chocolate cake with our coffees. Importantly, the dreaded “does it contain nuts?” question was met with a knowledgable answer and without the ‘frightened bunny face’ that I often encounter when I ask this question. J+A definitely gets a tick in the ‘cafe’s with good nut knowledge’ box on my website.

Lights were suspended from the ceiling, connected by wiring that was allowed to hang down, a section of electrical wire held at both ends and freely hanging. While I’m sure that this was done for aesthetic reasons (and certainly it works on that level), such hanging wires are in fact far more than merely pleasing to the eye. Such hanging wires were a mathematical puzzle just four centuries ago. Indeed, these simple hanging wires form curves that are so important they get their own name; they are catenary curves, from catena, the Latin for chain.

lights at J and A coffee Clerkenwell
Between each lamp, the electrical cord formed a catenary curve.

Galileo had thought that a wire hanging under its own weight and suspended at its two end points formed a parabola. A fairly simple curve that is easy to describe mathematically. It was natural for Galileo to assume that these catenary curves were really parabolic. He had earlier shown that objects that fell with gravity followed parabolic paths, and after all, the hanging wires did look almost parabolic. It fell to Joachim Jungius to show that the curve was not parabolic and then to Huygens, Bernoulli and Leibniz to derive the equations determining the form of the curve. Although the differences between the parabola and the catenary curves are subtle, they have profound consequences.

When a chain, or a wire, is suspended and allowed to hang under its own weight, it forms a catenary. Flipping this around, quite literally, a catenary arch will be self-supporting. This means that a vault made of a series of catenaries or a dome that is made into the shape of a catenary will be self-supporting with no need for buttresses. This property of the catenary curve was used by Antonio Gaudi in his designs of the Casa Mila in Barcelona and also by Christopher Wren. The famous dome of St Pauls is not a catenary, but it is not one dome either. It is in fact 3 domes stacked together. The outer dome is spherical (which is weak from a structural point of view) while the inner dome is a catenary. The dome between these two was designed, using the mathematics of the day, to support the impressive outer dome (more info here and here). Wren, was not just an architect, he was also a keen mathematician, there is maths, physics and beauty throughout many architectural designs.

Mathematics in the city reflected in the lights of J+A.

J+A is at 1+4 Sutton Lane, London EC1M 5PU

 

Categories
General Observations slow Sustainability/environmental

A drop in the Chemex?

Chemex, 30g, coffee
How do you prepare your coffee?

How do you prepare your coffee? Generally I’ll either use the Chemex or a French press. Often it will be the French press purely because it is, sadly, quicker. However, on those mornings that I do slow down to prepare a Chemex, I generally feel better for it. Not only does the coffee taste better, but those 5 minutes of preparing the coffee pay off as time for the mind to wander rather than just time spent waiting for the caffeine. When the Chemex is nearly ready, the fresh brew drips slowly from the filter onto the liquid below. Each drop produces a ripple pattern. At the start of the UN conference on climate change in Paris (COP21), we may well hear talk of some of our efforts being mere “drops in the ocean”. So it seems a good time to reflect on those “drops in the Chemex”. Just how much influence can a drop  have?

It is worth stopping for one moment to consider what is going on around us at this moment. As I write this, it is late November in the Northern Hemisphere. Taking a walk outside, I can see the last of the yellow leaves falling off the trees. In just a couple of weeks time, many of the trees will be bare. Why do the leaves fall from the trees? We could answer this question in a number of different ways. Biologically, the tree is forming cells at the joint between the leaf and the tree that will eventually enable the leaf to tear from the tree. As these cells are, in some way, responsible for the leaf falling off, they are called “abscission” cells. But even with these abscission cells, the leaf still needs something to force the leaf off. Often this is the wind which is why we get such an abundance of leaf fall on windy days. However there is another mechanism that can help a leaf to drop, and that is a curious interplay between the leaf and rain.

autumnal scene, red leaves, hydrophilic
The surface of the leaf changes from waterproof to ‘wettable’ over the course of the summer

In the spring, many species of tree, including Oak, develop a wax layer on the leaf. Perhaps you have been walking in the country and have needed to wax your walking boots before you go? The wax on the boots acts as a waterproofing for the boot, ensuring that your feet don’t get soggy. The wax on an oak leaf performs the same function for the leaf, it makes the leaf waterproof. Although this is not the only function of the wax. It seems that a waxy surface also slows the processes that dry out the leaf, prevents insects and pathogens attacking the leaves and may even play a role in affecting the way that the light is concentrated into the leaves for photosynthesis. Nonetheless, from the tree’s perspective, it is a significant advantage to have waterproof leaves. Imagine rain falling onto a waterproof surface. The drops of rain do not ‘wet’ the leaves but instead roll off. As the raindrops roll off, they take particles of dust and dirt with them. It is a tree’s way of cleaning itself. Waterproof surfaces are self-cleaning surfaces. Something that some scientists are now trying to replicate for man-made products.

hydrophobic leaves
Some leaves are more waterproof than others.

As the summer continues and the leaf gets older, the wax layer changes. The structure of the wax changes and erodes as the wind, weather and even pollution batter the wax layer. Just as with the hiking boots, the damaged wax layer results in a less waterproof leaf. The leaf becomes “wettable”. When a drop falls on a surface, the shape of the droplet is determined by how waterproof the surface is (more details here). A surface is termed “wettable” when the droplet becomes significantly flatter and coats the surface rather than forming a spherical drop that can roll off. Now consider each raindrop as it hits the different types of leaf. In the spring, the leaf is waterproof and the raindrops will roll off them. A drop of rain will cause the leaf to shake on its stem but then to return to its original position. It is ultimately not affected by a light rain shower. In the autumn when the leaves are no longer waterproof, the rain will start to stick to the leaf surface. Now when the leaf shakes, the wet leaf will not return to its original position but will bend slightly further downwards. As it continues to rain, the leaf will experience a greater torque and this means that it is more likely to fall off the tree. As each rain drop hits the leaf, the likelihood that the leaf will tear away from the abscission cells at the base of the leaf increases. Each drop has an effect.

This also has an important consequence for some of our technology. One renewable energy source that has been proposed for self-powering electronic devices harnesses the energy of rain. When rain falls on an array of cantilevers, it forces the cantilever to bend and to oscillate. This energy can be harvested ( that is, changed into a form that is useful to us) by using small piezo-electric devices (that convert movement into electricity or vice versa) at the  base of the cantilever. When a tree leaf is wet, the leaf joint experiences a greater torque which causes the leaf to ultimately tear from the tree. For the rain-energy harvesters, this is exactly what we want. The greatest energy obtainable from the cantilever system will be from cantilevers that can be made wet. Waterproof cantilevers would be a bad idea. A renewable energy that comes from rain would definitely be a positive development for UK energy production!

It seems that one coffee drop does indeed go a long way.