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prime days

(published 5July 2011)


A prime date.

5, 7 and 11 are consecutive prime numbers, but I wonder if 5,711 is one too? I guess the internet would be able to tell me in a flash. But I am not online at the mo. Somehow 5,711 does sound a suitably awkward number that it may be a prime. Let me see – is it divisible to an integer by 3? No. 5, no, don’t need to use a calculator for that. 7? No, but that’s a nice looking number 815.857142857142857142... 9, no. 11? No. 13, no. 15? No. 17, 19, 21, 23, 27? No, no, no, no, no. I’m beginning to wonder if I am going to have to try every odd number up into the hundreds...  maybe so. 35 (being a multiple of 7?) has a similarly good looking answer at 163.171428571428571428571... The forties and fifties and sixties give no integer divisible solutions, but the numbers by which they must be multiplied to get to 5711 are falling, and drop below 100. When I get up to trying 73 the answer is in the seventies, which means that I must be nearly there. 75? No, that is a 76.146666666666666666666666666666666666666666666666666666666667th of 5711. And so, seemingly all of a sudden, I know that it is indeed a prime day.

Last week a trip to the museum at Porthcurno whilst in the area to drop off a silicon photonics drawing. Porthcurno is a small bay on the south coast of Cornwall, down beyond Penzance, where, from 1870 onwards, early international and transatlantic telegraph cables crossed from the land into sea; submerged copper wires taking messages around the world. The first successful trans-Atlantic cable had been laid between the UK and USA in 1865. Submarine copper cables were insulated using gutta percha, a substance similar to rubber, which had recently been discovered. By 1900 Cornwall was connected to India, North and South America, South Africa and Australia via such cables at Porthcurno. Messages were transferred using Morse, or other coded systems; text messages being distributed via a global network more than a hundred years ago. 

And some interesting art. A piece called ‘Soundings’ by Penny Nisbet at the Porthcurno museum (, in which audio signals are generated from a dormant, but largely intact, submarine cable, since it acts “as a giant antenna in the sea of electromagnetic waves we are continually immersed in”. She further says “The prospect of the ancient telegraph cable resting silently on the seabed adds something to the fascination of listening to the sound of the radio energy it is receiving, including natural radio emissions of cosmic and atmospheric origin as well as those from man-made power sources.”

At the nearby Newlyn Art Gallery I pop in to a related exhibition of sounds and sculptures, co-curated by students at Falmouth Art College, called Down There Among the Roots (see for more info). In the Lower Gallery the sounds, by Chris Watson, include those made by hydrophones submerged “at the point where the ocean breaks upon the land and burying equipment into the earth beneath a series of wires”. These noises accompany Phoebe Cummings’ un-fired clay sculpture in a vitrine (and I must admit I’m a sucker for a vitrine – if your tastes are of a similar vein take a look at Marielle Neudecker’s tank works sometime) of a scene incorporating Malaysian Isonandra Gutta trees, producers of the aforementioned gutta percha. Upstairs, larger miniature un-fired sculptures of the Cornish landscape are accompanied by sounds captured from stretched wires in Australia and Cornish field recordings. And the view from the cafe, it being a sunny, turquoise-seaed, cloud-rushingly breezy day, provides other sensory fulfilment.

Art, science and Cornwall on a sunny day – a prime combination.

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