heliocentric theory

Paradigm shifts at The Observatory, Marchmont St

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