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SPRING 2003 - This month from Architects of Eternity

The Machine that Bent Atoms  

The Machine that Bent Atoms, Cambridge, Lat. 52o, 12'N, Long. 0o, 07'E, 23 September 1919.

In my column THE MOVING FINGER this autumn I have published the text of my most recent article for Chemistry in Britain which deals with the oldest fossils in the world. The technology behind that investigation is mass spectrometry so here's a reconstruction of how the mass spectrograph was invented, taken from my book ARCHITECTS OF ETERNITY

Cambridge's wind has a special quality at any time of year, and in the winter of 1919 it chilled Francis Aston to the marrow as he cycled swiftly along King's Parade towards the Cavendish. The fat cobbles of the road were icy and his already erratic front wheel threatened to slip sideways at any moment and deposit him unceremoniously on his flannelled backside. But he continued rattling his way past King's with its brightly painted Victorian post-box and imposing arched lodge. The College's chapel glistened in the cold sunlight, proclaiming the College's vaunted musical aspirations - as well as its wealth - to the world. At the site of the sheer, cold sides Francis' thoughts turned fleetingly back to his own comfortable college rooms further back up Trinity Street at St John's. The fire in the saloon would be bright now that his scout had been in to turn it, but within minutes she would find that for the third time that week he had forsaken his first cup of tea and the muffin on which he customarily breakfasted.

But it was worth the early starts, for the apparatus was almost completed. Down narrow Free School Lane he cycled, past the bay front window of his laboratory, and then turned hard left under the peaked archway of the Cavendish itself. Standing his bike against the wall of the tiny courtyard within, he then walked back into a shadowed doorway. Past the entrance to the steep steps that led to the famous tower room where Rutherford was revolutionising science. He walked down the narrow passage and into his cluttered office. The stone floor was covered in a fine patina of glass dust that crunched under his brogues, and the wooden benches that surrounded the room were covered with a hazardous confection of old glass tubing, burnt-out electrical valves and fragments of bent wire and twisted metal. In the corner of the room a glass-blower's torch still sputtered yellow with the rich coal gas that fed it. From its brass valve another length of flexible metal hosing led to the bulbous oxygen tank. With the two gases combined, the flame was hot enough to melt the hardest silicon glass. Aston rubbed the tips of his fingers against each other in rueful memory, they were baked hard by more than one bruising encounter with white hot glass. But, like the early starts, that too was worth it, for on the bench in the middle of the room, four foot high at the maximum extent of its curvature and dominating that narrow space stood the machine.

Aston circled it carefully, admiring for the thousandth time the smooth sweep of the glass flight tube, the uncompromising gunmetal grey of the frame that supported the pumps and the sprawl of frayed wire that covered the entire system like so much confetti. He had had to think of a name for this contraption now that it was almost ready and only the previous night had decided on 'mass spectrograph'. What could be simpler? This was an instrument that ignored the complicated chemistry of atoms and reached straight for the heart of the matter: their weight. But in the arcane world of physics Aston was only too well aware that weight was too imprecise a term; the particles that his machine separated were differentiated by mass. Drawing a hand along the machine's harsh metal surface he reflected on the analogy that he had used only last night in the senior common room to explain the machine's operating principles. It was based on something that he had had seen only a week before at the college's sports-field out on the Madingly Road. Two runners - undergraduates - had been panting hard as they rounded the final curve towards the finishing line. It was an uneven match, as one must have been a good head taller than the other and weighed at least two stone more. He was struggling, panting far behind his smaller comparison who, head down, was running like a thing possessed. As the lighter man had flown round the final corner he had eased gently and unknowingly toward the outer marker of his lane so that as he entered the final straight he was running at the outer edge of his lane. Not so the other runner. Aston had seen that as the heavier runner entered the corner, puffing and winded, but still gamely making good time, he had not deviated nearly as far as the lighter man; his heavy gait had kept him centred firmly almost in the middle of his lane all the way around the corner and down into the final straight.

And last night, as he stared into the flickering flames in the hearth and searched for the words to explain his invention to a classicist and a historian, that image had come back to him. The masses he was measuring, he had said, were like the two runners; because they had different weights, they were unable to stay the course with equal precision. The smaller runner - he of lighter mass - had drifted off to the edge of his lane - deflected by the combination of his own velocity and the need to turn the corner; the heavier mass had not deviated as far. And Aston's apparatus had a bend in it, like the sportsfield at Madingly Road, and, just like the runners, the atoms or molecules in the machine's flight tube would need to turn the corner. However, in his machine, the corner would be negotiated under the deflecting influence of the magnetic field that awaited the particles just as they eased into the turn. And when they left the corner, they, too would occupy different positions within their own lanes. They would have been separated by the different responses of their mass.

After this pronouncement Aston had seen his audience stare at him, felt their amusement. But he had not cared, for a machine that could separate big atoms from small atoms, just by bending them through a magnetic field, would change the face of science. Of that he was sure.

Architects of Eternity

Extracted from Architects of Eternity by Richard Corfield. Published by Hodder Headline, ISBN 0-7472-7179-8.

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Richard Corfield 2003 in association with pedalo.co.uk