There were three of them in on it at the start. Juny Parrish and her partner, Moss, were engineers working on the Mare Imbrium section of the trans-lunar railway; their friend, Ringo Takashi, was designing a mural for the big interchange station at Archimedes City. They were all from Paris, Dione, had helped to rebuild the city after the Quiet War, and had worked on the railway that girdled Mimas. The railway stretched across the nearside southern hemisphere of Earth’s Moon was a much bigger project, but in many ways easier. With the exception of Montes Taurus, the terrain was mostly rolling lava plains, with few large craters or rilles. The big machines that fabricated the pylons and track rolled on at a steady three kilometres per day, with few snags, so Juny and Moss were able to commute between the railhead and Archimedes City fairly regularly. One night, over dinner, Ringo told them about a fabulous three-hundred-year-old movie he was mining for his mural, a vast panorama blending dozens of paleo-spaceflight representations of the exploration of the Solar System. He showed them a clips of ape-men clustered around a vertical slab, and people in weird silvery spacesuits examining an identical slab in a pit dug into the lunar surface, said he was working on something that would merge the two.
‘A where-we-came-from, where-are-we-going kind of thing. I might make it the centerpiece.’
Moss was interested in the slabs. ‘Where is the one on the Moon supposed to be?’
‘Tycho,’ Ringo said. ‘The movie is very strange: an attempt at realistic futurism mixed with weird transcendentalism. Aliens uplifting the ancestors of humanity, astronauts triggering an alarm on the Moon, proving that humanity has left the cradle, and nonsense involving wormholes and a kind of posthuman transformation.’
‘I know these people working on wormhole theory,’ Moss said. ‘A posthuman clade in the Belt. You should show them this.’
Juny said, ‘Are they really trying to make wormholes?’
‘Of course not. You know posthumans. All theory and no application.’
Moss was fiddling with the second clip, freezing the moment when one of the astronauts reached out to the black surface of the slab.
‘It would be interesting to actually make one of these things,’ he said. ‘You could plant it in Tycho.’
That was how it began.
At first, they talked about casting a slab of black lucite and incorporating it into Ringo’s mural, playing the two clips superimposed on each other in its depths. Ringo soon dismissed this as a cheap and obvious trick, but the idea didn’t quite go away. Why not make a slab, a monolith as it was called in the movie, and plant it somewhere? Bury it, Juny suggested, with clues pointing towards it, and make a piece of action art or secret theatre involving unwitting treasure hunters that would imitate the lunar scene in the movie, complete with a radio pulse aimed at Jupiter. Or better yet, Moss and Ringo said, aim the pulse at some star where the aliens might come from . . .
It became a game they played over several dinners. Evolving and refining it, until they were all agreed that they had something worth doing. Juny and Moss organised the design and construction of the monolith in a print factory run by a friend of theirs. A black slab with dimensions in the ratio of 1:4:9, the square of the first three integers, 3.35 metres tall. Its faces smooth and black and non-reflective, incorporating a system that converted sunlight to electrical power, stored in capacitors that at a touch anywhere on the surface discharged in a radio squeal shaped by internal waveguides.
The fabrication of the monolith was straightforward: the three of them spent far more time discussing how to erect it, and where. They quickly eliminated Tycho Crater and anywhere on the nearside, because there were too many installations and satellites and spacecraft that could be disrupted by a powerful radio signal. They talked about sites elsewhere in the Solar System, but eventually settled on the farside of the Moon, atop the rimwall of a small crater inside the larger Mendeleev Crater, a spot near a popular hiking trail.
After much argument, they settled on an enigmatic unmodulated radio signal rather than some kind of encrypted message, and decided that it should be aimed at the core of the galaxy. Moss, with the stubborn literalism that was sometimes endearing, sometimes frustrating, said that no alien civilization would ever be found there because the central black hole violently affected the whole region; Juny and Ringo pointed out that they weren’t aiming it at actual aliens, and besides, there were a good number of nearer stars in the same direction. It was a trivial hack to make the wave guide directional, and to delay transmission of the signal when the galactic core was below the horizon. Moss incorporated a safety routine, too, so that the signal would also be delayed if the monolith detected any spacecraft or satellites in the path of the radio beam.
‘We don’t want this to come back and bite us,’ he said.
All that was left was to organise the emplacement. They hired a lunar hopper and borrowed a small construction robot, swore Ringo’s assistant to secrecy, and planted the thing in six hours. Ringo’s assistant took photographs of the three of them posed in front of the monolith, as in the movie clip, helmet visors fully polarised to hide their identity, and after Moss activated it they all had to resist the temptation to touch it: part of the fun was waiting for some random stranger to discover and trigger it.
They did not have to wait long. The first squeal was triggered just eleven days after the monolith had been emplaced, and soon there was a steady trickle of signal pulses. It became a brief sensation. People hiking the trail made a point of diverting to the monolith and triggering it and posing for pictures. Several couples performed partnering ceremonies in front of it. Visitors left tokens, or added rocks to a cairn. Someone strung Tibetan prayer flags nearby, which slowly bleached in the relentless sunlight. The nearest hiker shelter was renamed Monolith Station.
Juno and Moss and Ringo talked about claiming credit but never did. It was more fun to leave it as an enigma. They moved on to other work, and over the years mostly forgot about their little project. Juno and Moss drifted apart; she continued to work in railway construction, while Moss set up home in an ecocommune on Mars, gardening a tented crater. One day, some thirty-six years after they’d planted the monolith, Ringo sent an eidolon to Juno, who was working then on girdling a rock some twenty kilometres in diameter with a monorail.
‘There are other monoliths,’ the eidolon said, without preamble, and showed her in quick succession images of slabs on Ceres, Vesta, several smaller asteroids, and one of Mars’s moons, Phobos. They were identical to the original and like the original aimed their radio blurts at the galactic core, and had appeared within the last hundred days. Clearly a large crew, or perhaps several smaller ones, had been involved in their placement.
‘I have no information on who did it,’ Ringo’s eidolon said. ‘Has anyone contacted you?’
‘No. I haven’t even talked to Moss for . . . it must be six years now.’
'I have already talked to him,’ Ringo’s eidolon said. ‘I’m living on Mars too, so I went to him first. He knows nothing about it. Neither does my assistant, or that friend of yours who helped with the fabrication. It’s a mystery.’
Juno told the eidolon a little about her work, and asked to be kept in the loop. In the next decade, more than a hundred monoliths appeared, scattered through the Belt, on Mars, on the moons of Jupiter and Saturn. No one claimed credit, although after a giant monolith more than a hundred metres tall was discovered on Earth, in the Australian outback, someone blew it up and released a terse statement claiming that monoliths diverging from the norm were heretical. Rumours of a secret cult of philosopher-monks circulated but were never confirmed, and no one ever saw a monolith being erected.
Ringo and Juno met one last time on Phobos. Ringo was outward-bound; Juno was heading towards Bradbury, to advise on construction of a tram system inside the tented city. They confirmed to each other that no one had ever contacted them about the original monolith. Ringo believed that it was a gigantic practical joke, and the rumours about vagabond monks and worship of alien overlords were part of it.
‘Anyone with an industrial maker could replicate what we did,’ he said. ‘We should only be surprised that it is still ongoing after all these years.’
Juno told him that she had analysed the spread of the monoliths. There appeared to be at least nine separate nodes, nine groups making them and setting them out.
‘If it’s a joke,’ she said, ‘it is highly organised. Many people must be involved, and none have ever broken cover.’
‘Neither did we,’ Ringo said.
‘Imagine if we did.’
‘No one would believe us.’
‘There’s no sign that they’ll stop,’ Juno said. ‘Whoever they are.’
‘Maybe they truly believe in what they are doing,’ Ringo said. ‘Maybe it isn’t a joke, to them. Maybe they really do believe that random radio signals will be detected by aliens.’
‘Our silly little joke,’ Juno said.
‘Our work of art,’ Ringo said. ‘I’m glad we never signed it. Because if these monks are right, if aliens do come here, if they’re hostile or if they destroy us without meaning too, we’d be the worst and the most foolish villains in all of history.’
He looked deadly serious for a moment, then burst into laughter.
Juno laughed too. ‘For a moment you almost had me.’
They never met or talked about it again. But on rocks in the belt, on moons in the Outer System, on kobolds and comets, the monoliths continued to appear, each a lonely and enigmatic iteration of a secret purpose, each a single voice of a random and unfinished symphony, singing out to the stars at the touch of a wanderer’s hand.