Decoding the Heavens

by Decoding the Heavens- Solving the Mystery of the World's First Computer (retail) (epub)

  Wright stayed for three weeks in the back room of Bromley’s bungalow, surrounded by the radiographs he had been separated from for so long. Some days Bromley never made it out of bed, so Wright left the house and toured Sydney’s museums. But when Bromley was well enough, the two of them sat and talked for hours about their time in Athens, about the Antikythera mechanism, and about what went wrong.

  Bromley was tired, weak and depressed. After years of denial about his illness, he couldn’t escape the fact that he was dying. He told Wright in one of his more lucid moments that for years he had dreamed that his name – and his name alone – would be attached to the final solution of the Antikythera mechanism; that was why he had guarded the results so jealously. To Wright it felt like the closest that Bromley was going to come to a confession; if not an apology, then at least an admission that he had treated Wright badly.

  Still, trying to persuade Bromley to hand over the radiographs before he died was a horrible task.

  To Bromley, knowledge really was power. Throughout his life he had defined himself by what he knew and others didn’t. It was what drove him to become the world’s foremost expert on Charles Babbage, and it was what drove him to return to Athens year after year to study the Antikythera mechanism. Knowledge wasn’t to be shared, it was to be held on to like a currency, to be bartered at a later date. Once, on one of his trips to London, he gave a seminar on the Antikythera mechanism to an audience of curators at the Science Museum. At the end, as is customary at such events, one of them raised his hand and politely asked a question. Bromley looked straight at his inquisitor, eyes twinkling, the corners of his mouth curling through his beard into the hint of a smile.

  ‘That,’ he said finally, ‘is for me to know and you to find out.’

  So for Bromley to give up all of his data to Wright would be the ultimate defeat, it would be an admission that all hope was gone. Wright was torn by guilt; he had to make Bromley face the fact that whatever his dreams had been, he would never be the one to solve the Antikythera mystery. But he could see the pain in the lost, shrunken man before him.

  Some days, Wright thought he had won.

  ‘This is a hopeless case,’ Bromley would announce. ‘Take the data if you want.’ But on other days he’d change his mind, saying that Wright had convinced him the project was worth pursuing: ‘When I’m stronger I’ll have another go.’ Eventually, Bromley’s wife found a way.

  ‘You’ve done this great body of work,’ she coaxed. ‘Let Michael go and make sense of it all, so that your efforts can be recognised.’

  Bromley did keep some of the material – most of the photos and the clearest radiographs – but he handed over the rest to Wright at the end of his stay; a last gift to the living from the soon-to-be dead.

  When it was time to leave, Bromley insisted on driving Wright to the airport, though the effort drained the air from his lungs and the blood from his face. They said goodbye on the forecourt.

  ‘It’s been good knowing you.’

  ‘Have a safe trip.’

  It was the last time they saw each other. Bromley lasted longer than the six months the doctor gave him, but he finally succumbed in September 2002, without making any further progress on the Antikythera mechanism. He was 55.

  Wright was asked to write an obituary for Bromley. Unlike the perfectly glowing accounts that appeared elsewhere, his article was the painful result of an urge to tell what he felt was the unvarnished truth. ‘If I sometimes resented the way in which Allan took, and kept, control of the project, I recognise that without him I might well never have got to Athens at all,’ he said. He ended with four simple words: ‘I will miss him.’

  After Wright returned to London with the radiographs, still working at evenings and weekends, he developed an idea that had been forming in his mind since he first saw the fragments in Athens. It was the possibility that on the front of the mechanism there had once been many more gears, which modelled the movements of the planets.

  It was a bold idea, but several lines of evidence were leading him to the same conclusion. When Wright had examined the fragments directly he saw the remains of brackets sticking forwards from the large spoked wheel. It looked as if they had once carried something round on this gear as it turned. Price had noted these brackets, but ultimately ignored them. In his reconstruction there wasn’t room for any extra mechanism here, because his second big wheel – his Sun wheel – had turned directly in front. But Wright now knew that there was no need for a Sun wheel. The way was clear for extra structures. What were they?

  Wright suspected there were more gearwheels. He had seen wheels carried round on other wheels before – it was a common device in the astronomical clocks he knew from the Science Museum, particularly for calculating the movements of the planets. A train of gears mounted on a turntable would drive a gearwheel around at a certain speed, at the same time as it was being carried round in a bigger circle. Whereas a differential gear has two inputs and one output, here there is just one input and one output, but the output isn’t constant – it speeds up and slows down relative to the central axis as the little wheel turns. This type of gearing is still called epicyclic or planetary gearing, although it’s now more likely to be found in vehicles or industrial machinery than in astronomical displays.

  Unlike the Sun and the Moon, the planets don’t follow smooth paths across the sky. They change speed, stop and zigzag about, so much so that their name (from the Greek word planetes) means ‘wanderer’ or ‘vagabond’. These erratic movements in the heavens upset the Greeks of classical times, because they liked to think of everything in the universe as perfect, and perfect motion was uniform motion in a circle. The structure of the universe reflected the nature of the gods, so there could be no question of any sort of deviation or irregularity. Reconciling the wandering motions of the planets with this idea of perfect circles became one of the most pressing philosophical problems of the day.

  In the fourth century BC one of Plato’s students in Athens, called Eudoxus, came up with a system of concentric spheres. Those that carried the planets slid over others, all rotating in different directions, with the Earth in the middle. The effect was that each planet traced a sort of figure-of-eight curve. It was a cunning idea, but it didn’t match the actual movements of the planets very well. Then in the third century BC a mathematician working in Alexandria called Apollonius developed a much better idea: epicycles. He imagined the planets looping the loop – in other words, travelling in a small circle at the same time as the centre of that circle moved around the Earth.

  This explained why the planets appeared to speed up and slow down, and why sometimes it even looked as if they were going backwards.

  The concept works because it does actually bear some relation to reality. As we observe a planet, it is circling the Sun at the same time as Earth is, so the motion we see is the combination of those two circles – the planet’s orbit and ours. When we look at Mercury or Venus, which are closer to the Sun than we are, the motion we see is a combination of our orbit around the Sun (this is the bigger circle) and the planet’s orbit around the Sun (the smaller circle). When we look at the planets that are further from the Sun than us – Mars, Jupiter and Saturn – we’re the ones looping the loop. Our path around the Sun is superimposed on the bigger circle that is the planet’s orbit around the Sun. Apollonius didn’t know any of this, of course. He was just trying to come up with a geometrical model that could explain the way that the planets looked from Earth.

  It’s quite straightforward to translate this model into the language of gears. If you want to model the motion of Venus, for example, you need a big turntable that rotates at the speed of the Earth around the Sun (or the Sun around the Earth, from a geocentric point of view). Then you need a smaller gear that spins around on that turntable, to simulate Venus’s orbit around the Sun. The size and speed of this smaller gear relative to the big turntable are determined by the size and speed of Venus’s orbit compared to Earth�
�s. If you imagine a pin sticking up from a point on the edge of the smaller wheel, then the speed with which the pin circles the big wheel’s central shaft represents the motion of Venus as we see it. The astronomical clocks of Renaissance times used slotted levers to translate this motion back to a pointer on the zodiac dial. The dial pointer would be driven by a shaft that was itself turned by a lever that had a slot cut into the end of it, so it looked a bit like a tuning fork. This slot fitted over the pin on the epicycle wheel. As the epicycle wheel looped the loop, the pin slid up and down in the slot, driving the lever, and therefore the pointer, around at varying speed.

  All of the necessary sizes and speeds of the cycles and epicyles can be determined from straightforward observations of the planets’ movements. Ptolemy, working in Alexandria in the second century AD, worked out the appropriate mathematical equations. But other Greek astronomers were certainly thinking along similar lines before him, even if their figures haven’t survived.

  So could the Antikythera mechanism have included epicyclic gearing to model the motions of some or all of the planets? The inscriptions that Price had originally noted (but passed over) in Gears from the Greeks were a hint in this direction – Venus was mentioned by name, and there were several mentions of ‘stationary points’, the moment at which a planet appears to stop and change direction. But that wasn’t all. Wright saw that protruding forwards out of the centre of the big four-spoked wheel was a sturdy square pipe that was fixed on to the metal plate behind. The square shape suggested that some wheel must have sat here, with a square hole to make sure that it didn’t slip around the central pipe. This is just what you would expect if there was epicyclic gearing riding on the big wheel – a fixed wheel in the centre would drive an epicyclic gear train as it was carried around on its turntable. This idea also explained the size of the four-spoked wheel – it needed to be so big because it was carrying other gearing.

  The four-spoked wheel moved around at the speed of the Sun around the Earth. That would be perfect for carrying gearing to model the two inferior planets, Venus and Mercury. But ancient Greek astronomers saw all of the planets as equally important. Wright felt sure that if the designer of the Antikythera mechanism had modelled Mercury and Venus, he would have included the others as well. This was a bit more complicated, because it would require a separate turntable rotating at the appropriate speed for each planet, with the epicycles then rotating at the speed of the Sun. But it could be done using just the same mechanical techniques. During 2001 Wright presented his ideas at a conference in Olympia, Greece, taking along a little cardboard model to demonstrate how the planetary gearing might have worked.

  Wright knew that suggesting so much extra gearing for which no trace remained was likely to be controversial. And although the epicyclic gearing he was proposing was no more complicated than the differential gear that Price had suggested, he was sure that he’d face strong scepticism about whether the Greeks would have been capable of such a thing. It was a step up from simply modelling a body going around the Earth at a constant speed. This was taking the latest mathematical theory about variations in the motions of the planets and translating it into mechanical form.

  So Wright decided to do what he did best. He would make a model of the mechanism by hand, using traditional materials and methods, to prove that the Greeks could have done it. As soon as he got back from Olympia he gathered some pieces of scrap metal – including the name plate from an office door and a pub door kicking plate – and started to make his own Antikythera mechanism. By this time he had married again – to an understanding woman called Anne who worked across the road at the Victoria and Albert Museum – and he’d made a new workshop in one of the rooms of their period home in Hammersmith, pushing back the tide of books until every inch of floor, wall, shelf and bench space was covered with tools and old metal gadgets and instruments, from replicas of ancient astrolabes to twentieth-century trombones.

  By the end of the year he had reconstructed the front of the mechanism: the gears calculating the motions of the Sun and Moon, as well as epicyclic wheels for Venus and Mercury. He now needed to construct separate turntables for Mars, Saturn and Jupiter. And he figured that if the mechanism contained epicyclic gearing for the planets, it would probably have done so for the Sun and Moon as well.

  Only one orbit is involved in the apparent motions of each of these two bodies from Earth – us around the Sun, and the Moon around us. But the Greeks knew from their observations that this couldn’t be the whole story – both the Sun and Moon appear closer at certain times than others, and their speeds vary in a regular pattern. This is because the orbits of the Earth and Moon, like those of the planets, are not regular circles, but elongated ellipses with the body that they are orbiting around located nearer to one end. The Moon, for example, spends part of its orbit relatively close to us (so it looks larger in the sky and appears to be moving faster than average) before it swings off around the more distant tip.

  The Greeks were so committed to the idea of the heavens consisting of perfect spheres and circles that they would have found it impossible to contemplate such a thing. Instead they explained the variations using different combinations of circles – either epicycles or what’s called an ‘eccentric’ model. This assumes that Moon or Sun is moving in a perfect circle around the Earth, but that the centre of its orbit is slightly offset from the Earth. So one end of its orbit will be slightly closer to us and the other end will be slightly further away. Because the orbits concerned aren’t very elongated this actually works quite well as an approximation to reality. Wright added two more epicyclic gear trains to his model so that the pointers on the zodiac dial incorporated the varying motions of the Sun and Moon. The Sun epicycle sat on the main wheel along with those of Venus and Mercury, while the Moon epicycle needed its own turntable. He kept the old Sun pointer, however, which was simply going around at the Sun’s average speed, because this showed the date against the calendar scale.

  Everything was falling into place. The epicyclic gearing fitted into the mechanism so naturally he knew he was right. But as he worked on the planetary display, the back of the mechanism – Price’s supposed differential gear and the function of the back dials – remained a mystery.

  Then Wright heard that he had competition.

  A film-maker called Tony Freeth, who lived down the road in Ealing, west London, was apparently campaigning to persuade the Athens National Archaeological Museum to let him image the Antikythera fragments again, using the latest X-ray technology. Freeth was working with Mike Edmunds, an astronomer from Cardiff University, and a team of prestigious Greek scientists.

  Wright had come across Edmunds before. Judith Field and Edmunds had studied together at Cambridge University and one day she got a call from him. Edmunds asked her about the Antikythera mechanism, so she gave him Wright’s number.

  If he calls, you must tell him all you can,’ she told Wright. ‘He’s a serious astronomer, a professor! Make sure you give him a good answer.’

  So when Edmunds called, Wright spoke to him at length, telling him all about the problems he saw with Price’s reconstruction, how the mechanism may have displayed the movements of the planets, and what he thought needed to be done next. Edmunds told Wright that a research student of his, Philip Morgan, was engaged in a project to reassess the mechanism and that at the end of it, they planned to write about their work.

  ‘I’ll let you know when it comes out,’ he said.

  Wright saw the article in print at the beginning of 2001. To most eyes it would have been a fascinating account of a little-known ancient mystery, but Wright was horrified. Much of it was a review of Price’s work, which, however well-researched, he felt should be discounted. As far as he was concerned, at least, the most original and worthwhile points in it were the ideas that he had shared with Edmunds on the phone – the possibility that the device had been a planetarium, and his ideas for future research. At the end of the paper, Edmunds and Morgan ack
nowledged a ‘communication from M. T. Wright’, but that was it. There was no mention of all the years he had worked on the mechanism or the progress he had made. A familiar feeling crept through him like icicles. Once again, he had shared his ideas in good faith. And once again, he felt he was being sidelined.

  Straightaway, he wrote a letter of complaint to the journal and it was published a couple of issues later. ‘Readers may wish to know about the subsequent and continuing work by Bromley and myself,’ Wright said ‘which will oblige all who are interested in this mechanism to trust less implicitly in what Price wrote.’ After outlining some of the work he had done so far, he finished with barely contained frustration: ‘It is surprising that Edmunds and Morgan do not mention our work, since the communication that they acknowledge was a telephone conversation between Prof. Edmunds and myself in which I outlined it.’

  Beneath the letter, the journal ran a reply from Edmunds – an equally thinly veiled dig at Wright’s lack of progress so far. So when Wright heard that Tony Freeth and Mike Edmunds were working to get access to the Antikythera fragments, just as he was finally starting to get somewhere, he felt dismayed and angry. Later, when Freeth approached him to ask if he would support their campaign, he sent a frosty reply, explaining that as an employee of the Science Museum it would not be appropriate for him to tell staff at another museum what to do. Besides, there was no need for new images. His own radiographs were perfectly adequate and he knew he could solve the puzzle, if only everyone would leave him alone long enough to do so.