Connectivity

Shades of light and dark. How do we see shadow, colour, depth? How is it linked to the physics of coffee?
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The other morning, grinding coffee in order to prepare a V60 (the last of a fantastically complex Natural El Salvador from Amoret coffee), I was hit by the intense aroma of rich, freshly ground beans. It seems at the moment that we are surrounded by more vivid impressions of things that have, in reality, always been there, but that have previously been obscured by other features of our lives. Such things have been revealed by the changes to our lives that have come about as the result of the “lock-downs” needed to reduce the transmission of Covid-19. The birdsong that seems more dramatic and intense than before the traffic subsided. The colours of the trees as the spring light bounces off and filters through the leaves no longer surrounded by a misty haze of pollution (now suggested through its absence). And of course the smell of the coffee hitting our olfactory senses.

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Before this period of social distancing and self-isolation, I had been preparing for another in the series of Coffee & Science evenings at Amoret coffee in Notting Hill. The title of the evening had been “Space Coffee” and we were going to explore the connections between what happened in your coffee cup with features that you can see in the atmospheres of planets such as Saturn and Jupiter. Actually the connections are a lot wider than that and can be seen on the Earth too, but the atmospheres of Jupiter and Saturn have some very peculiar structures that you may not immediately think could possibly be linked to your coffee cup. One of the key people who worked on the science behind this was Hermann von Helmholtz (known as H2 to his friendsa). For the Coffee & Science evening, the important work of Helmholtz was on vortices and fluid rotations, but it turns out that he has more links with a coffee cup than that, connections that can even give us some food (drink?) for thought in this time of separation.

which will win, gravity or light
The world has not really been turned upside down, but certainly the way that we view it could be. An opportunity to re-assess our view points?
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Helmholtz made many contributions to the understanding of our world including how we see it. In addition to inventing the ophthalmoscope (in ~1850), Helmholtz was interested in the way in which we perceive colour and how we manage to see in 3D. Thinking about the way in which we see things like light and colour and developing on the idea that how we perceive our world is, ultimately, received in each of our own minds via our sense organs, Helmholtz compared the sensations of light and colour to symbols of language: ways in which we interpret the world around us. As Michel Meulders writes in his fascinating biography of Helmholtz (told from the view point of a medical doctor rather than a physicist)b, Helmholtz had

“…stated lyrically that we should thank our senses, which miraculously gave us light and colour as responses to particular vibrations and odour and taste from chemical stimuli. We should thank the symbols by which our senses informed us of the outside world for the spell-binding richness and the living freshness of the sensory world.”

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What does it mean that I should thank my senses for the way in which I smell, see and hear the coffee beans as they are ground?

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The connections between Hermann von Helmholtz and coffee are more than just the vortices that form, and more than the fact that Michael Faraday once served him cups of it while he was preparing lectures for the Royal Institutionc. We’ll be exploring those links over the next few weeks, from how we see coffee, through how we hear it and eventually to what ties it all together. Please keep checking back but also, do let me know what new sensory symbols you have perceived in this time of opportunity to attention.

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a “Worlds of Flow”, Olivier Darrigol, Oxford University Press (2005)

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b “Helmholtz: from Englightenment to Neuroscience”, Michel Meulders, MIT press (2010)

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c “Helmholtz and the British Scientific Elite: from force conservation to energy conservation”, David Cahan, Notes & Records of the Royal Society, 66, 55-68 (2012) doi:10.1098/rsnr.2011.0044

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