whispering gallery

Good vibrations at Rosslyn, Mansion House

Coffee at Rosslyn, Mansion House, EC4N, coffee clock, base
Coffee time at Rosslyn, EC4N. Why is it that base 60 was used as a counting system in Mesopotamia? And why is it that the echoes of this are still seen in our clocks and the angles of a circle (unless you use the radian system) but not in our everyday counting system?

It’s always “coffee time” at Rosslyn apparently, at least according to the clock above the door. In front of you as you enter the cafe is the counter and, as you move down to collect your coffee (for take-away) the day’s edition of the Financial Times is stuck to the notice board where you wait. An interesting touch, somehow making a resonant connection with the City coffee houses of old such as Jonathan’s, just around the corner, where the stock market was originally located.

There are not many stools or tables in Rosslyn, which appears to be designed as more of a take away space. Nonetheless, we found a perch by the window overlooking the bench seats outside. It is a perfect place to watch the world go by. The massive junction of Poultry providing plenty to see.

Coffee is roasted by Modern Standard and there are bags of roasted coffee on sale (together with some of the mugs) at the other end of the counter to the FT. The occasional (welcome) plant reminds us that life is not just concrete, glass and cars/buses. Although it was sunny, it was not yet hot and so we had a soy hot chocolate and a long black, went back to take our seats and waited for the drinks to arrive.

The wooden spoon that came with the coffee was an interesting touch, reminding me of Barn the Spoon and his work in Hackney. While the clock got me thinking about our use of base 10 as a counting system and the older systems that used base 60.

coffee, hot chocolate, plant, mugs, wooden spoon.
A quiet moment with a coffee and a hot chocolate at Rosslyn. Notice the spoon.

Contemplating these things we noticed a strange effect in my coffee. Or rather, I noticed it and brought attention to it by taking repeated photographs of the coffee while tapping the bench just to try to capture what I was seeing: a resonance pattern on the coffee surface. At this point, your mind may connect to several different things. There’s the resonance effects involved in the Whispering Gallery in St Pauls close by to Rosslyn. There are the resonance patterns caused in bells, drums and violins and the relation between these, air movement and music. There’s the fact that these movements initially revealed the excellence of the table as a movement sensor: the ripples on the coffee revealing footsteps behind us rather like we detect earthquakes in the earth. (My later attempts at photographs were in that sense “faked” as I was tapping the table beside the cup to try to reproduce the effect so that it was visible on my camera).

Or there was the fact that this movement in the coffee cup is exactly the same phenomenon as something in our lab. But whereas in the cup it is an interesting, almost aesthetic feature, in the lab it can be a major pain to deal with.

The problem comes in that the coffee cup was in the middle of the bench. This had been an accident in terms of where we were seated but it had large effects. Because the bench table has its legs at each end, but nothing in the middle, the table itself acts as if it is a massive drum. And one of the more fundamental resonances of a drum has the maximum movement at the centre of the drum: the edges don’t move much but that bit in the middle oscillates wildly. In the coffee cup this manifests as a ripple pattern on the coffee surface, reflecting the street outside in slightly distorted fashion. In the lab this means that some of our instruments become incredibly difficult to use.

ripple pattern coffee Rosslyn
Can you see it? The ripple pattern caused by the coffee being on the drum of the table at Rosslyn. An interesting effect to watch in coffee but what if this sort of thing happens in a physics lab?

Consider for example the Atomic Force Microscope (AFM). This microscope is able to resolve the structure of films down to an almost atomic resolution. It does this by monitoring the resonance of a small silicon cantilever as it approaches the surface of the material being studied. Just for a moment, put a wooden sugar stirring stick (or a lollipop stick) on the edge of a table and ‘twang’ it. It vibrates just as the silicon cantilever does in the AFM. Then think, what if you put the stick in honey and ‘twanged’ it – or put a magnet on the end of it and ‘twanged’ it over a bit of iron, how would the oscillation change? This is what the AFM does but with the atomic forces that are present when you get very close to the surface of a sample. But the phrase “very close” is key. Typically, the cantilever will be nanometers from the surface of the sample and, as it is very sensitive to the forces at the surface of the sample, if that sample moves because the instrument is vibrating up and down on the floor, the image will be at best blurry and unusable and at worst, you are going to be damaging your cantilevers.

And so, it is important to ensure that the AFM is placed in a suitable area of the lab: not in the middle of a floor in a high level building because that will just act as a drum in exactly the same way as the coffee cup was being vibrated at Rosslyn. If you’re not fortunate enough to have the AFM in a basement lab, you could place the AFM (and other vibration sensitive instruments) at the corner of the room, so the vibration amplitude of the floor-drum is minimised. You could also try to place the instrument on concrete blocks to ‘damp’ the vibration. An extreme example of this sort of damping is the ‘quiet labs’ of Lancaster University just next to the M6 motorway. These labs have been designed to minimise vibration noise and the team there routinely achieve atomic level resolution with their atomic force microscopes.

The silence of an area next to the M6 contrasting with the noise of the City. The directions that contemplating a cup of coffee takes you are always surprising.

Rosslyn is at 78 Queen Victoria Street, EC4N 4SJ

Getting to the point at Sharps

coffee and Caffeine at Sharps

Coffee at Sharps Coffee Bar.

There will be plenty to notice at any café that shares space with a barber’s shop. And so it was the case at Sharps Coffee Bar on Windmill Street. The café is at the front of the barber’s shop which is separated from the tables by a glass wall: people watching in a type of human goldfish bowl. The counter was on the left of the shop as we walked in and it was great to see that in addition to the usual espresso based drinks there was an aeropress coffee available (as well as batch brew). Given the chemistry of pre-brewed coffee, I tend to pass on batch brews though I am aware that there are many people who enjoy speciality coffee who will disagree with me. However, given that the barista on the day was “still perfecting” his aeropress recipe, I enjoyed instead a long black prepared with The Barn roasted beans.

The sign in the window suggested that “maintenance matters” which is something that I am sure that we can all agree on, whether it is on haircuts, coffee equipment or even equipment in a science lab. A stitch in time saves nine so they say. On the board listing the prices, it was good to see that Sharps coffee bar mentioned the use of almond milk. Although personally I generally drink black coffees, cross contamination can be an issue for allergy sufferers and so it is always helpful to be alert to the use of nut-based milks when they are used (you can read more here). Edibles were supplied by Kaffeine. Behind the bar there were a couple of trough-like sinks while the contrast in the wood and the tiling on either side of the bar provided another avenue of thought.

cacti in a row

Sign, window and cacti at Sharps Coffee Bar

In the window, a row of cacti caught my attention. Cacti seem known for two things. One is that they are (generally) prickly and the other that they are extremely water efficient.  But these two facts can also apparently be linked. Some cacti use their spikes or hairs to change the local atmosphere around them so that air is trapped in the hair or that air flow is reduced. Both of these measures would help to prevent water loss from the main body of the plant. It is an example of the structure of something affecting the environment around it. Similar effects can be seen on the hairs on a spiders legs which trap air allowing the spiders to survive if they are submerged as well as to waterproof the legs in more general times. Some plants similarly use hairs (and therefore the air trapped in them) to waterproof their leaves. The benefit of this for the plant is that waterproof leaves mean that drops of water roll off of them causing the leaves to be self-cleaning. This is an effect that people are trying to mimic in order to make self-cleaning surfaces for human use.

View of St Paul's Cathedral London

There is a whispering gallery in the dome of St Paul’s Cathedral. An interplay between sound waves and the shape/size of the dome.

Structures can also be used to trap sound waves either deliberately with meta-materials or, almost accidentally such as the whispering galleries of cathedral domes. Moreover the hairs themselves can act as part of a sound detection system. Human ears for example have tiny hairs in the cochlea. As a sound comes in and these hairs vibrate, the movement of these hairs gets converted to a nerve impulse that we can eventually ‘hear’. Perhaps this could take us into a consideration of what hearing is, what sound is and, in a Berkeley-type way whether we actually experience anything outside of ourselves at all. However, more directly it takes us back to the barber’s shop and how evolution has resulted in a wide variety of structural adaptations that allow different life forms to live optimally in their environment.

And with that, it would probably be time to sit back and enjoy another coffee.

Sharps coffee bar is at 9 Windmill Street, W1T 2JF