Month: August 2016

Categories
Coffee review Home experiments Observations

Reality bites at Chin Chin Labs, Camden

Coffee grinder at Chin Chin Labs Camden
Nitro-brew? Not this week. Coffee and liquid nitrogen at Chin Chin Labs (a nitrogen dewar is on the table behind the coffee grinder).

It is true that Chin Chin Labs is not really a coffee-based café (although it does serve decently prepared, Monmouth roasted, coffee). Nonetheless, there is no question but that it has to be included as a cafe-physics review on Bean Thinking. Why? The answer is in the photo of the coffee grinder, though you may have to look carefully. You see, Chin Chin Labs is offering a different sort of café experience. Not coffee nor tea, but ice cream, indeed, Chin Chin Labs in Camden Lock advertises itself as the ‘future of ice-cream’ and the reason it does so is because here, all the ice cream is made with liquid nitrogen.

There are only 3-4 tables inside Chin Chin Labs which makes it more of a take-away bar than a sit down café. As you enter, a large dewar of liquid nitrogen is on your left, just behind the counter. Arranged behind this large dewar are a set of smaller dewars while on one of the ice cream preparation tables another (small) dewar sits with a pipe in it, ready for the nitrogen to be decanted out. If all these dewars are full, that is a lot of liquid nitrogen. The coffee is decent and prepared in the normal styles (espresso, Americano, cappuccino, latte), though this place is really not about the coffee (one of the staff expressed surprise that I’d ordered a coffee and not an ice cream). Next to the espresso machine were a set of glass beakers and glass containers as you would expect to find in a chemistry set, while the aprons worn by the staff had “Chin Chin Labs” written in a glittery, (futuristic or disco?), font.

Various dewars of nitrogen
Nitrogen, nitrogen everywhere…

There are many fun things that can be done with liquid nitrogen. From creating ice cream, through to shattering flowers and even to a possible solution for the energy storage problem (info here). Not to mention its important use as a coolant in all sorts of physics experiments and for biological storage. I have spent many hours decanting liquid nitrogen into buckets for basic experiments or into the first cooling stage of very strong magnets (such as are used in MRI machines).

However, at -196ºC, liquid nitrogen is not a liquid that can be treated flippantly. Although it can be fun, and handled correctly there is no problem, it can nonetheless be very dangerous. Which is why something else about Chin Chin Labs struck me quite hard. While there were glass beakers and containers that a cartoon may feature as part of a science ‘lab’, there was none of the equipment that you would actually expect to see in a real lab where liquid nitrogen is used. In our lab, oxygen monitors beep (annoyingly) every 60 seconds*, eye goggles and proper cryogenic-suitable gloves are stored in a highly visible position easily accessible to anyone in the lab. Risk assessments are prominently displayed so that everybody is aware of the risk of oxygen depletion (leading to suffocation) were the nitrogen dewars in the lab to fail and suddenly vent all that liquid nitrogen into nitrogen gas in the lab. These things are not fun, but are a necessary part of running a lab in which cryogenic liquids (including liquid nitrogen) are stored and used.

Ice cream at Chin Chin
The final result: vanilla nitrogen-ice-cream.

It is this contrast, between what is expected of a lab (glass beakers and complicated looking valves on the dewars) and what is in a lab (safety equipment and complicated looking valves on the dewars) that struck me. What do people, the public, café owners, think a lab looks like? What do they (you?) think a scientist looks like? Do we prefer indulging in our stereotyped ideas of a lab rather than think about the reality of life in a real science lab?

I am sure (or at least I hope) that the safety equipment, oxygen monitors etc. are present, but hidden under the counter, at Chin Chin Labs. It should always be possible to have fun with liquid nitrogen, whether in a lab or a café. And the ice cream is definitely worth trying (according to the person I visited Chin Chin Labs with). But, if you happen to pass by Camden Lock and try some nitrogen ice-cream, please do spend a minute to ask yourself, what you think a scientist, or a lab looks like. And do let me know what you think, I’d be interested to know.

Chin Chin Labs is at 49-50 Camden Lock Place, NW1 8AF

* In the event of the failure of a liquid nitrogen dewar, the oxygen in the room would be displaced. The resulting decrease in oxygen concentration can cause sleepiness, mental confusion or in the case of severe oxygen depletion, coma and death (more info here, opens as pdf). Oxygen monitors check the oxygen level in the room is at a safe level. The beep is annoying but tells us that the monitor still has battery and is checking the oxygen level in the room.

Categories
General Home experiments Observations Science history Tea

Coffee and Pluto

Three billion miles away, on an object formerly known as the planet Pluto (now sadly demoted to the dwarf planet Pluto), there exists a plain of polygonal cells 10-40 km across, extending over a region of about 1200 km diameter. Last year, the New Horizons mission photographed this region and these strange shapes (see photo) as the probe flew past Pluto and its moon Charon. But what could have caused them, and perhaps more importantly for this website, can we see the same thing closer to home and specifically in a cup of coffee? Well, the answer to those questions are yes and probably, so what on Earth is happening on Pluto?

Plutonian polygons
What is causing these strange polygons on the surface of Pluto. Image © NASA

Pluto moves in an highly elliptical orbit with an average distance to the Sun of 5.9 billion km (3.7 billion miles). Each Pluto year is 248 Earth years but one day on Pluto is only 6½ Earth days. As it is so far from the Sun, it is very cold on Pluto’s surface, somewhere between -238 to -218 ºC. The polygons that were photographed by New Horizons are in the ‘Sputnik Planum’ basin where the temperatures are at the lower end of that scale, somewhere around -238 ºC. At this temperature, nitrogen gas (which makes up 78% of the Earth’s own atmosphere) has not just liquified, it has solidified; turned into nitrogen ice. These polygons are made of solid nitrogen.

But solid nitrogen is a very odd type of solid and in fact, at the temperatures on Pluto’s surface, solid nitrogen is expected to flow with a very high viscosity (like an extremely gloopy liquid). And it is this fact that is the clue to the origin of the odd polygons (and the link to fluids like coffee). Pluto is not just a cold dead rock circling the Sun, but instead it has a warm interior, heated by the radioactive decay of elements in the rocks making up Pluto. This means that the base of the nitrogen ice in the Sputnik Planum basin is being heated and, as two groups writing earlier this summer in Nature showed, this leads to the nitrogen ice in the basin forming convection currents. The warmer nitrogen ‘ice’ at the bottom of the basin flows towards the surface forming convection patterns. It is these nitrogen convection cells that appear as the polygons on the surface of Pluto.

Rayleigh Benard cells in clouds
Rayleigh-Benard cells in cloud structures above the Pacific showing both closed and open cell structures. Image © NASA image by Jeff Schmaltz, LANCE/EOSDIS Rapid Response

Of course, convection occurs in coffee too, we can see it when we add milk to the coffee and watch the patterns form or by observing the dancing caustics in a cup of tea. So why is it that we see stable polygons of nitrogen on the surface of Pluto but not coffee polygons on the surface of our coffee? The first point to note is the time-scale. Although the polygons on Pluto are moving, they are doing so much more slowly than the liquid movement in a cup of tea or coffee, at a rate of only a few cm per year. But secondly, the type of convection may be different. Although both of the papers in Nature attributed the polygons on Pluto to convection, they differed in the type of convection that they considered was happening. McKinnon et al., suggest that the viscosity of the nitrogen on Pluto is much greater on the surface of the basin than in the warmer interior and so the surface flows far more slowly. This leads to cells that are much wider than they are deep. We would not expect such a drastic change in the viscosity of the coffee between the (cool) top and (warm) bottom of the cup! In contrast, Trowbridge et al., think that the cells are Rayleigh-Bénard convection cells,  circular convection cells that form such that the cells are as wide as they are deep. This sort of convection is seen in a coffee cup as well as in the sky on cloudy days: On the Earth, clouds often form at the top (or bottom) of Rayleigh-Benard cells, where hot humid air meets cold dry air (more info here). But to form cells that you can see in your coffee (such as are on the surface of Pluto) you would need the coffee to be in a fairly thin layer and heated from below. You would also need some way of visualising the cells, either with an infra-red camera or with powder suspended in the liquid, it would be hard I think to see it in coffee alone. However, you can see these cells in cooking oil as this video shows:

As well as providing the link to the coffee, the different types of convection on the surface of Pluto hypothesised by Trowbridge and McKinnon have consequences for our understanding of the geology of Pluto. If the cells are formed through Rayleigh-Bénard convection (Trowbridge), the basin has to be as deep as the cells are wide (meaning the basin has to be 10-40km deep with nitrogen ice). If McKinnon is correct on the other hand, the basin only needs to be 3-6 km deep. It is easy to imagine that an impact crater could cause a shallow crater such as that needed for McKinnon’s mechanism. A deeper crater would create another puzzle.

If you do manage to heat coffee (or tea) from below and form some lovely Rayleigh-Bénard cells while doing so I’d love to see the photos or video. Please do contact me either by email, Facebook or Twitter. Otherwise, if you just enjoy watching the patterns form on your coffee, it’s worth remembering that there could be an entire cosmos in that cup.

Categories
cafe with good nut knowledge Coffee review Observations Science history Sustainability/environmental

Counting the caloric at Jaz & Jul’s Chocolate House, Chapel Market

Jaz Jules chocolate house
Jaz and Jul’s, The Chocolate House on Chapel Market

The London coffee houses of the seventeenth and eighteenth centuries have entered history as Penny Universities, places of debate and centres of news. Together with the (scientifically based) Grecian, there was Jonathan’s in Exchange Alley (origin of the stock exchange) and Lloyd’s on Tower Street (associated with insurance). But along side these coffee houses there were the chocolate houses, Whites and Ozinda’s on St James’ St and the Cocoa Tree in Pall Mall. White’s in particular developed such a reputation that it features in Hogarth’s The Rake’s Progress (which can be seen at Sir John Soane’s museum).

So it is an interesting bit of history repeating to find Jaz & Jul’s, a chocolate house on Chapel Market. The interior here is very far from Hogarth’s rendering of White’s. Here, light fittings hang from the ceiling like drops of chocolate about to melt into the café while photographs of cocoa plants and farms adorn the walls. Moreover the emphasis on social responsibility, including in sourcing, mean that this establishment is worlds away from the debauched shenanigans at White’s. Their coffee is roasted and supplied by Monmouth while the cakes are hand made and, needless to say, very chocolatey. The light and fluffy chocolate-Pimms cake arrived with my coffee presented on a plate and matching cup that reminded me of a mint-chocolate-chip ice cream.

Interior of Jaz and Jules Chapel Market
The chocolate counter at Jaz and Jul’s

The side of the counter was tiled to resemble a bar of chocolate, which immediately reminded me of the physics and chemistry of chocolate crystallisation. However, the physics connection of this cafe-physics review is a bit more lateral than that. Soon after I had enjoyed my incredibly chocolatey cake at Jaz & Jul’s, a study was released which showed that Britons were significantly under-reporting their daily calorie intake. Could it be that the obesity epidemic is a result of us eating too much rather than merely exercising too little? Apparently, rather than consume the (recommended) levels of 2500 kcal for men and 2000 kcal for women, many people were eating up to 3000 calories per day. Everything in moderation of course and there was plenty of room in my own calorie count for that great piece of cake (honestly). But the word ‘calorie’ turns out to have a connection with chocolate in a more unexpected way.

Calorie comes from the Latin, calor, meaning heat which in turn hints at how we used to think about heat itself. While we now think of heat as energy, which is why it doesn’t even strike us to equate the ‘energy’ in the chocolate cake with the number of kilo-calories in it, this is not how heat was always viewed. In fact, in the eighteenth century, about the time of the old chocolate houses, heat was thought of as a type of fluid, caloric. Caloric was thought to be able to flow in and out of all substances. When something got hot it was because the caloric flowed into it, when something got cold, it was because the caloric had leaked out. Caloric theory was in many ways very successful in understanding heat and heat processes. For example, the theory easily explained thermal expansion, if a fluid had to flow into something in order for that thing to warm up, then surely, the fluid has to occupy some space, the object must expand to hold it!

Mint choc chip cutlery
Coffee with the Chocolate-Pimms cake.

One area that was tricky for caloric theory though was the fact that friction could cause something to heat up. Such heat generation is crucial for our extraction of chocolate. Once harvested from the plant and cleaned, the cocoa bean is first roasted then shelled to leave the cocoa ‘nibs’. These nibs are then ground more finely. As they are being ground, the friction caused by grinding is enough to cause sufficient heat to melt the cocoa butter in the nibs which is then extracted and retained for later use*. How could you explain this heating if you thought of heat as a fluid? The traditional explanation was that as the two objects rubbed against each other (in this case, nib and stone grinder), the caloric fluid would be squeezed out, it would appear as if heat had been generated.

Benjamin Thompson, Count Rumford (1753-1814), disagreed with this explanation of heat. In the course of a colourful career he had been involved in manufacturing cannons in Bavaria. Rumford had noticed that a lot of heat was generated each time a cannon shaft was bored out. The heat produced continued as long as the grinding continued. If the heat were due to the cannon leaking caloric, surely there would be a point at which the cannon stopped getting any hotter. Yet this did not happen. Rumford suggested (correctly) that instead what was happening was that the energy generated by the boring was being transferred into the metal of the cannon, causing microscopic motion.

Although the heat as motion/energy idea eventually caught on, caloric in some ways still survives in the name that we give to our food energy intake. And so we can return to the cake, could it be that spending time thinking about the caloric in the cake can justify the calories consumed eating it? Sadly the jury is out on whether thinking counts as calorie counting exercise. It seems that the brain’s energy consumption is already so great (at 20% of our resting metabolic rate), that intense thinking does not add too much to the energy consumed by the brain. So we’ll need another excuse and I don’t think we have to look far. The coffee and chocolate at Jaz & Jul’s is delicious enough to justify a significant chunk of your daily calorie count, just based on considerations of taste. Everything in moderation!

 

Jaz and Jul’s is at 1 Chapel Market, N1 9EZ

*”Chocolate: A Global History”, by Sarah Moss and Alexander Badenoch, published by Reaktion Books, 2009

 

Categories
General Science history

Super cold brew

Cold brew coffee with ice
Cold brew coffee served with ice. Image from pixabay.com

How cold do you drink your cold brew? Poured over ice? As an experimental physicist who works with liquid nitrogen (& helium), I was initially quite intrigued to learn of nitro cold brew coffee. Could it be coffee that somehow uses liquid nitrogen to fast-cool it, what would that do to the taste? You would expect liquid nitrogen (at -196ºC) to rapidly cool the coffee below its freezing point, after all, it is how Heston Blumenthal makes ice cream. To make a drink-able cold-brew with liquid nitrogen would require great skill, especially given the potential health risks. It would be another situation where you may well ask yourself, “what’s the point?”

However, it turned out that the reality was far more mundane, gaseous nitrogen is passed through cold brew coffee to create a drink with a silky mouthfeel. A smooth drink that comes straight from the tap just like stout. Such a drink is going to behave as an ordinary liquid and chilled only to the point that it is kept in the vat. The novelty would presumably come from the mouthfeel introduced by the many tiny bubbles distributed through the drink. Just as with water, if you cooled the nitro-brew below its freezing point it would solidify and form coffee cubes. No real difference to get excited about. But what if there was a very different sort of liquid, a “super liquid”, that didn’t behave like water, coffee or even liquid nitrogen but one that could leak through solid cups?

Superfluid helium is such a liquid. Like water, oil or even liquid nitrogen, when you cool helium (the same gas that is in party balloons)∗, it becomes an ordinary (but very cold) liquid at -269ºC. But unlike those liquids, when you cool it further, below -271ºC, it does something very odd indeed. It becomes a superfluid in which the liquid moves with zero friction or equivalently, zero viscosity (honey is very viscous, water is very much less so).  And it is because of these properties that it can do some astonishing things such as stream through cracks in containers that were thought impermeable (see the video at 0:52m), or even climb the walls of the container it is in (1:13m)!

 

To explain the behaviour of superfluid helium it is necessary to use quantum mechanics. Indeed, Fritz London (1900-1954) is said to have described both superfluidity and superconductivity (which happens in solids) as “quantum mechanisms on a macroscopic scale”. At the heart of the theory of superfluidity is the idea that the helium atoms fall into the lowest energy ground state possible, a Bose-Einstein condensate. To form a Bose-Einstein condensate, the particles (atoms of helium) have to  be bosons rather than fermions. All particles in nature can be categorised as either bosons or fermions. The difference between the two types comes from another quantum property of particles, the spin. Spin is related to the angular momentum of the particles and, this being quantum mechanics, can take only discrete values, either whole number or half integer numbers.

cold brew, doublemacbex
Another photo of cold brew coffee, this time from Bex Walton (flickr) – note the condensation around the rim, much could be said about that. Image CC licensed.

Bosons are particles with integer values for spin, fermions are particles with half integer values. Most of the elementary particles you will have heard of are fermions: electrons, protons, neutrons, they’re all fermions. Some particles however, such as the photon (the particle of light) are bosons. Helium 4 atoms are effectively composite bosons, because of the combination of 2 protons, 2 neutrons and 2 electrons that make up the atom. When you add their individual (half-integer) spins, you will get an integer spin, hence a boson not a fermion. The distinction is important because while bosons can share a lowest energy state (the Bose-Einstein condensate), fermions cannot. Quantum mechanically, no two identical fermions can share an energy level (the Pauli exclusion principle), so you can never get to a state where all the fermions are in the lowest energy state. There are practical, every day consequences of this for us, such as the way metals such as copper conduct electricity and heat, the fact that the electrons in the metal are fermions turns out to be crucial for us to understand how metals ‘work’. In contrast, the fact that the helium atoms are in the lowest energy state in super-fluid helium means that the ‘liquid’ behaves very strangely indeed.

We seem to have come a long way from the idea of a cold coffee. But perhaps next time, if someone offers you a “super cold brew” take a moment to think of the physicists who get to play with some real super cold superfluids†. Hope you enjoy the video.

 

*Technically it is Helium 4 that becomes superfluid at 2.2 K (-271ºC). The rarer isotope, Helium 3, does not become superfluid until much lower temperatures and even then, the superfluidity has some very special properties.

†Although I do get to work with liquid helium (and although it is mostly helium 4), I work at the relatively ‘hot’ temperatures at about -269C. At this temperature the interest is not so much in the liquid helium itself but its use as a coolant for other materials.

 

 

Categories
Coffee review General Observations Science history slow Sustainability/environmental

Life at the Coffee Jar

CoffeeJar_exteriorI had been waiting for an opportunity to try the Coffee Jar for a fair while. It is not that it is in a remote location, it is in fact situated on Parkway just five minutes walk from Camden or Primrose Hill. Nonetheless it feels as if it needed a special trip to get there (and, though this is pre-empting the end of this cafe-physics review, it does deserve such a ‘special trip’). Inside, there is seating at the window and running along one wall, and although it is not the smallest of cafés, it is certainly a ‘cosy’ one. This is not intended as an estate agent’s euphemism but instead to emphasise the additional meanings of this word to convey a warmth and friendliness about the space that the Coffee Jar definitely has. So far, we have been twice (see, the ‘special trip’ is worth it!). The coffee comes from Monmouth and so unsurprisingly, on the two occasions I had a coffee there (Americano and Soya Latte), it was very well done and enjoyable. At the front of the counter are a wide selection of home made cakes and cookies. While this presentation can be awkward for allergy sufferers (nutty cakes or cakes with loose nuts on top are placed side by side with the nut free options which could give contamination issues), the cookies were very good (more on the cookies later).

As befits the name, hand painted jars and coffee mugs decorate the end of the tables (and can be purchased should you wish). Individual art pieces decorate the walls while the window is painted with a scene that is somehow mirrored (shadowed?) in the ink prints on the take-away cups. All in all, there is plenty to notice in this “cosy” space. And so it took a fairly long time before I noticed the fish that was dangling above my head.
robot fisherman, robot fisherwoman, coffee jar camden
Apologies for the blurry photo but you can see the robot fisherman on the shelf.

Yes, this seemed an odd thing to me too, so I checked and indeed, a wooden fish was suspended on a string from something hidden on the shelf above my seat. At this point, an opportunity arose to go and sit at the window and so I was able to turn and look properly at the cause of the suspended wooden fish which was actually a toy robot. It just gets more surreal. But indeed, on the shelf above the seats against the wall was a toy robot fishing, a wooden fish hanging at the end of his (her?) line.

A robot that is fishing can prompt a large number of questions which seem to me to be at the intersection of science and philosophy. To what extent has automation improved our lives? Is it a good or a bad thing to use robots in jobs traditionally done by humans? Moving away from robots and towards computers, what about artificial intelligence? Much has been written about artificial intelligence in recent years. There is some angst about whether robots will come to take-over the world with an ability to think that far surpasses our human ability. Alternatively, there are people who look to artificial intelligence with the hope that it will help us drive cars or investigate pollution or all manner of other (to a greater or lesser degree) useful things. One test that has been suggested as a way of establishing whether any particular computer, or artificial intelligence, can think is the Turing test proposed in 1950 by Alan Turing. A prize set up to reward the first computer “chatbot” that could reliably mislead human judges into thinking that it was itself a human (the Loebner prize) has so far not been won (a prize is awarded each year for the most convincing chatbot but so far, none has been so reliably convincing as a human to win the top, “gold” prize).
soya latte at the coffee jar camden
Unusually I had a soya latte.

But the robot on the shelf was not represented as thinking but as fishing, an occupation that is associated with relaxation. This robot was not just thinking, it was taking time out to relax; it was represented as being alive and sentient. This prompts a rather different question to that of merely intelligence: At what point do we say that something is living? How can we define life? As could perhaps be expected, NASA has taken some time to consider this question. As they say on their website:

“Comparing the semantic task [of defining life] to the ancient Hindu story of identifying an elephant by having each of six blind men touch only the tail, the trunk, or the leg, what answer a biologist might give can differ dramatically from the answer given by a theoretical physicist.”

Which may make you wonder well, what would a theoretical physicist say about how we could define life? Erwin Schrödinger (1887-1961) had a very interesting, physics-based, definition of life. Although he is now perhaps more famous for his equation or his cat, in 1944 he wrote a book called “What is Life” (opens as pdf). To very briefly summarise, the argument goes that the tendency of all inanimate objects is towards equilibrium. A hot cup of coffee will lose heat to its immediate environment and so reach the same temperature as its surroundings, a small amount of blue food colouring at the bottom of a glass of water will eventually colour the entire glass a paler blue. To be alive is to defer this state of equilibrium for to achieve equilibrium is the same thing as death. Schrödinger argued that rather than merely consume energy, living things consumed negative entropy from their food-stuff. Entropy is a quantity introduced with the theory of thermodynamics. It is often taken as a measure of the order in a system (though there are caveats to that). The second law of thermodynamics states that for a closed system, the entropy of the system will either increase or stay the same. This suggests that to avoid equilibrium, or equivalently to avoid death, the living thing must consume order (or negative entropy) and somehow stave off this tendency to maximum entropy. To answer the objection that it would be easy to consume negative entropy by eating diamonds (which are highly ordered crystals) and so therefore that there has to be more to life than this, Schrödinger expanded on the thermodynamics of his argument. That bit gets quite technical and so is another reason that, if you are interested, it is worth getting hold of the book.

 

So to return to one of the first questions but phrase it in a slightly different way. Could a robot cookie maker replace the “home-made” cookies that were on offer in the Coffee Jar? It turns out that this is a subject that my often-times cafe-physics review companion (let’s call them J) has quite an opinion about. We visited the Coffee Jar twice partly because of the cookies! It seems to me that J would not have been impressed by the cookies were they robotically mass manufactured. There was something very appealing in the home made quality of them. So, there we go, one of the questions answered neither scientifically nor philosophically but on the very reasonable basis that home made cookies taste and look better. Do let me know if you agree if and when you visit the Coffee Jar.
The Coffee Jar is at 83 Parkway, NW1 7PP
“What is life?” Erwin Schrödinger, Cambridge University Press, first published 1944, my edition published 2013