International Year of Light

An opportunity to become a cafe-scientist

coffee, Timberyard, wooden tray — A great place to sit and do some citizen science: Timberyard, Seven Dials has plenty of seats outside.

There are many things to be gained from putting down your smart phone when you enter a café. Firstly, there is the opportunity to fully experience the coffee. The sounds as it is made, the smell, the taste, even the feel of the coffee. Then there is the opportunity for people watching; their behaviour as they order their coffees or have their meetings or try to alleviate boredom while playing with their smartphones. Of course, there is also the opportunity to look at the history of the café and its surroundings, to think about a café-physics review or just slow down and notice things. There’s always something interesting going on.

If you are lucky enough though to be in Athens, Barcelona, Belgrade, Berlin, Copenhagen, London, Manchester, Milan or Rome there is now even more reason to put down that phone while you savour your coffee. By doing so, you could be helping scientists with a few questions that they have about atmospheric pollutants. If you are not in one of those cities, you miss out this time, but you may want to keep reading because if enough people get involved now, perhaps next time the iSPEX-EU project may come near you.

contrail, sunset — What sort of aerosols and pollutants are floating in the atmosphere above your head at this moment?

The question is, what are the atmospheric pollutants that are in the air near where you are now? Perhaps you are in a café on a main road and the answer seems obvious, it is those cars and buses that keep passing by. But there are in fact many forms of atmospheric aerosols or particles and they range in size from a few nanometers to tens of microns (which, in terms of coffee grind is from much smaller than the smallest Turkish coffee to approximately the size of a small particle in an espresso grind). Is it really so clear that where you are, in the centre of that big city, is that polluted? If on the other hand you are on the coast in Barcelona, just how salty is that salty sea air? The iSPEX-EU project allows you to measure it and find out.

These particles of dust, salt and soot etc. can have an effect on human and animal health, so clearly we want to know more about their distribution and their prevalence. But there are also, more subtle reasons why we may want to know about them. They may have an effect on global warming and they are certainly needed in order for clouds to form, (though as yet we still do not fully understand this process). We need more data about what aerosols are around and where they are to start to know what questions to ask (let alone answer) about health, the climate and cloud formation. Yes, we have satellite measurements and pollution data at specific locations, but what people are missing is that local information. What are you actually breathing? When you look up at the blue sky, what pollutants (or other type of aerosol) are you looking through? Can we get enough data to know how the air quality varies between the cafés of Hackney and those of Hammersmith?

Skylark Wandsworth — Another ideal cafe for iSPEX-EU measurements, great coffee and a lovely outdoor seating area at Skylark cafe, Wandsworth Common

To get this data the scientists involved in iSPEX-EU need people, many people. People who are willing to spend 5 minutes turning their iPhone (sadly it is an iPhone-only project) into a pollution detector. The more people that they can get measuring, the more data that they will be able to obtain. All you need is an app from the App-store and a (free) device that fits over your iPhone camera which you can pick up from somewhere local to you. Then, you just take a seat outside the café on a lovely blue sky day between now and the 15th October, aim your phone at the sky and take a series of photographs which are shared back with the scientists coordinating the project. If you are curious to know how your air quality compares with that in another participating city, you can check the live map to see how the measurements are going across Europe.

The device works by looking at the colour spectrum as well as the polarisation of the light reaching the camera as a function of angle. This information gives tell-tale clues as to the size of the aerosols as well as their prevalence. There is a lot more information on the website of the iSPEX-EU project and so I would recommend that if you do want to know more, you click their link here. In the meantime, why not sign up with iSPEX-EU, take a seat outside in that café and enjoy a great coffee knowing that, as you do so, you are contributing to our understanding of atmospheric science.

If you do decide to participate, please let me know of any great locations that you find, both for the coffee and the measurements, or share your pollution measurements with me in the comments section. I look forward to seeing some great data on the live map.

To get involved with the iSPEX project, you can follow the link here.

Reflections at Knockbox, Lamb’s Conduit Street

Knockbox coffee is on the corner of Lamb’s Conduit Street and Dombey Street. It is a small place and we had to go twice in order to get a seat, though the compensation is that there are views all around the cafe (it being on a corner). I enjoyed a very good americano, made using Workshop coffee. Complementary jugs of mint infused water were dotted around the cafe which is always a nice touch. Sadly, I tried Knockbox just after lunch and so didn’t try any of the edibles on offer. This does mean however that I will just have to go back to try them at some point (and of course, to enjoy another coffee).

There were a lot of things to notice around Knockbox that day. There were the air bubbles in the water that had become stuck around the mint leaves. There were the light bulbs (that you can see through the windows in the picture). And there was the espresso machine: A gleaming piece of machinery that sat majestically on the counter. Looking at the espresso machine it was impossible not to be struck by the reflections from the surface. The reflections are not only testament to how much the staff at Knockbox must polish the machine; how reflections work is the subject of today’s Daily Grind.

espresso machine, metal, reflection — The gleaming espresso machine at Knock box

The interaction of materials with light is one of those fascinating areas that reveal physics at its most fundamental. I’ve often taught undergraduate physics students who are looking forward to learning about quantum mechanics because it is “weird”. This is true, quantum mechanics can be quirky, but electromagnetism (which is about light) can be just as odd. To get such elegant and surprising physics out of what is essentially all classical, nineteenth century theory, is one of those joys about learning about (and teaching, using and experiencing) this subject.

However, to return to the espresso machine and light. How light interacts with objects reveals how the electrons are distributed in the material which in turn tells you something about the atoms that make up the espresso machine. (For how to experience electrons in your coffee, see Bending Coffee, Daily Grind, 26 Nov. 2014). As the electrons are electrically charged, they respond to light which is, ultimately, an oscillation of electric (and magnetic) field. Electrons in a metal are shared in an “electron sea” between all the atoms in the metal. Consequently, when light falls on a metal surface, the electrons can respond to the electric field oscillation of the light and they re-emit the light backwards as a reflection.

ImpFringe, #ImpFringe, Fox's Glacier Mints, linearly polarised light — Sugar rotates linearly polarised light. The ‘device’ above is made from layers of Fox’s Glacier Mints and 2 linear polarisers (eg. a pair of polarised sunglasses). Photographed at ‘Lit Up’, an Imperial Fringe event held at Imperial College London, that was free to the public.

On the other hand the electrons in the atoms of the plastic of the grinder (or the glasses on the top of the espresso machine) are held firmly to each atom. Therefore most of the light that we see will go straight through these substances with each atom acting to propagate the light forward but not able to completely block it for a reflection. Coffee beans too contain electrons that are held in place by the atoms in the molecules that make up the bean. Unlike the glass though, the electrons in coffee beans are held in atomic bonds that happen to have an “excitation energy” that is at a visible light frequency. Rather than let the light through, they absorb certain colours of light (more info in the Daily Grind here). The result is the opaque, deep brown of the coffee bean.

This year is the international year of light, a year which is intended to celebrate our understanding of light. There are so many light based processes occurring all around us at every moment. Why not stop in a cafe and see how many you can spot in your coffee cup?