parallel lines – Bean Thinking

lines on a table, parallax — An espresso using coffee from Redemption Roasters and a chocolate brownie. What more could you ask?

Many years ago, there was an aquatics shop on the site of what is now The Observatory, a combined photography gallery and coffee shop. Although there is plenty to see through this glass fronted café, you do not feel that you are in a goldfish bowl so much as that this is a space created for you to slow down and contemplate your surroundings. The large rooms and comfortably spaced tables do, of course, give the opportunity for people watching: when we visited, there were people working with their laptops on some tables while others were having business meetings. Then there are the photographs, currently (though only for a few more days), an exhibition of photographs from the 60s and 70s by John Bulmer.

The coffee is supplied by Redemption Roasters and I enjoyed a dark, toffee like espresso with a very good slice of a chocolate brownie (confidently nut free). Several types of milk are on offer for milk based coffee drinks as well as a selection of cold drinks, together with a wide variety of cakes. It is definitely a place to return to when in the area.

coffee the Observatory, TLR — Cakes on the counter at The Observatory. Note the twin lens reflex “camera” on the shelf behind the counter.

While waiting for my coffee, I noticed the grain of the wood in the table. Dark, almost parallel lines on a lighter wood. You can see it in the photograph. Looking around the café, such parallel lines were everywhere. Planks of wood lined the walls, vertical, parallel lines stretching up to the ceiling. In the room towards the back of the café, the ceiling also had parallel lines on it which, given I was viewing them from a distance, appeared to converge with the effect of perspective. It is difficult to know whether these effects were deliberate in a gallery/café so dedicated to an exploration of the visual but I like to think that the small twin lens reflex camera on a shelf (which sadly turned out to be a pencil sharpener on sale) was a nod to this idea shifting lines of sight and perspective.

By definition, two parallel lines are lines that will never meet, no matter how far the lines are extended. If they were to meet at any point, they would not be parallel. This offers a way of measuring the distance to stars as well as providing food for thought on our way of seeing our place in the universe. The idea is that of parallax. If you were to measure the relative position of a star against the background of stars at midnight in June, and then go back to measure the same star relative to the same background at midnight six months later in December, you may find that the star seemed to have moved. The amount it moves, its parallax, is determined by how close the star is to the earth (have a look at the diagram).

parallax and coffee — As the point of view moves around the Sun (represented here by a V60), the closest coffee bean appears to shift relative to the background coffee beans.
The lower two diagrams are an attempt to see things from the perspective of the Lego person separated by “6 months” distance.

Take as an example the star Sirius. Located relatively close to us at a mere 8.6 light year distance, Sirius has a parallax of 0.38 arc seconds or, equivalently, about 0.0002 of the angular diameter of the moon viewed from Earth¹. Stars that are further away are going to have an even smaller parallax until the parallax becomes so small as to be difficult to measure. Even for nearby stars such as Sirius, the small size of the effect meant that it wasn’t until 1838 that it was first measured. Which may be part of the reason that the theory of Aristarchus (310-230BCE) never caught on when it was proposed.

Aristarchus was an early proponent of the idea that the Earth went around the Sun (and not the other way around). The Greek’s realised that if Aristarchus was correct, there should be a parallax effect for the stars viewed at different times of the year (every 3 months)¹. Unfortunately, the Greeks also considered that the stars belonged to a thin shell, so effectively all the stars were at the same distance from the Earth. Consequently, the parallax effect that they looked for (if Aristarchus was correct) was for two stars on that shell to move first towards then away from each other as the Earth circled the Sun¹. They never observed this effect and so considered the heliocentric theory “inconsistent with observations”¹. Although we would now say that the fact that they didn’t observe any such shift is consistent with the huge distances to the stars (and therefore small shifts) involved, for the ancient Greeks it was a problem. As Archimedes commented, if Aristarchus’ theory had been true, it would mean that the universe was much bigger than they at that time thought.

Guardini has written about the effect on the human psyche of this changing idea of the universe and our own place in it (from the Greek’s idea of finite and limited, to finite with a God outside, to infinite and back towards finite but incredibly large). Do our ideas, our models, about the universe affect not only how we interpret the experimental evidence we see, but also our way of being, our behaviour towards our fellow humans and our planet?

Viewing things from a different angle, seeing the effect of a change of line of sight, it brings us right back to the photography in the gallery and the twin lens camera on the shelf. There are certainly many things to contemplate while enjoying a coffee at The Observatory. Which means a second espresso should definitely be a possibility.

You can view some street photography, including some photographed with a twin lens Microcord TLR camera on Artemisworks gallery here.

The Observatory is at 64 Marchmont St, WC1N 1AB

¹Astronomy, the evolving universe (6th edition), Michael Zeilik, John Wiley & Sons, 1991

BeanThinking started as a way of slowing down and appreciating connections, often between a coffee and the physics of the wider world but also in terms of what can be noticed in any café. Perhaps, for this first post of 2017, it’s worth spending five minutes looking at your coffee while you drink it to see what you notice. Here are a few coffee connections that occurred to me recently:

reflections, surface tension — Reflections on a coffee.

Parallel lines and surface reflection: The parallel lines on the ceiling of a café were reflected in a long black. Surface tension effects on the coffee meant that the reflections were curved and not at all parallel. A piece of dust on the surface of the coffee was revealed in the reflection by the curved reflections of the ceiling. Astronomers can use similar effects (where images of a star appear in a different location to that expected) to infer the presence of dark objects between distant stars and their telescope. This gravitational lensing can be used to detect quasars or clusters of galaxies.

layering of coffee long black — Layers of coffee

Layering of crema as the coffee is consumed: The coffee stain effect and this layering of the crema suggests a connection between a coffee cup and geology. It used to be my habit to take a mug of tea with me when I taught small groups of undergraduates. In the course of one of these tutorials, a student (who had been observing similar layering in my tea mug) said, “You drink your tea faster when it is cooler than when it is hot”. Full marks for observation, but not sure what it said about his attention during my tutorials! Similar observations though can help geologists estimate the age of different fossils.

interference patterns on coffee — Bubbles in coffee

Bubble reflections: An old one but the interference patterns caused by bubbles on the surface of the coffee are full of fascinating physics. The fact that the bubbles are at the side of the cup and seem to be grouped into clusters of bubbles may also be connected with surface tension effects (although there is a piece of weather lore that connects the position of the bubbles to the weather. If anyone ever does any experiments to investigate this particular lore, I’d love to hear about them).

Van Gogh’s Starry Night: The effects of vortices and turbulence caused the crema of a black coffee to swirl into patterns reminiscent of this famous painting by Van Gogh. As a result of posting this image on Twitter, @imthursty sent me a link to this preprint of a paper submitted to the arxiv: the connections between Van Gogh’s work and turbulence. A great piece of coffee combining with art and science.

So many connections can be made between tea, coffee and science and the wider world, I’d love to see the connections that other people make. So, if you see some interesting physics, science or connections in your coffee cup, why not email me, or contact me via FB or Twitter.