Short story. Alien avatars try to prevent backward civilisation from destroying precious (mathematical) artifacts

This story was told in two parts;

1) An alien civilisation (very advanced indeed) are trying to get an object to a distant Point A in space. They achieve this by firing two microscopic objects at near-lightspeed (a needle and a cylinder) with millimetric precision from two nearby systems. They almost collide and the interaction of the two, I believe the needle passes through the cylinder, sets in process a chain of molecular events culmimating in the cylinder turning into a space station, then receiving the mind-states of two scientists who beam down to a nearby planet to make contact with the locals.

2) On the surface of the planet, the two scientists make contact with the nearest authority figures. They use their advanced knowledge of science to convince them that they're aliens and try to convince them to stop a major project, some kind of mining operation that will destroy the last remains of an ancient race that used to occupy the planet. The precursor civilisation's remains consist of some kind of mathematical proof stored on tablets(?). Ultimately they're successful in getting a good look at these and are able to upload the info back to their own civilisation.

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  Much is made of the precursors being looked down upon by the locals "If they were so advanced, how come they're all dead?"

  
  


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  There are multiple mentions of the aliens being able to kill themselves at will if they're kidnapped or mistreated.

  
  


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  The aliens are able to use their space station to convince the locals that they're aliens.

  
  



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  The bodies are essentially disposable. If memory serves, they leave avatar bodies on the space station to die.

  
  


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  The scientists may have been lovers?

  
  

Answer

I believe you have conflated two Greg Egan stories, "Riding the Crocodile" and "Glory."

"Riding the Crocodile" described the firing of three projectiles at relativistic speeds to rendezvous in space and build an observatory, with digitized humans following a month later. The observatory was constructed to investigate a signal from the Aloof, beings who inhabited the bulge of stars in the center of the galaxy. The observatory was constructed by citizens of the Amalgam, a coalition of beings inhabiting the galactic rim. The rendezvous was described this way:

They watched a reconstruction of the first two modules coming together. The timing and the trajectories were as near to perfect as they could have hoped for, and the superconducting magnets had been constructed to a standard of purity and homogeneity that made the magnetic embrace look like an idealised simulation. By the time the two had locked together, the third module was just minutes away. Some untraceable discrepancy between reality and prediction in the transfer of momentum to radiation had the composite moving at a tiny angle away from its expected course, but when it met the third module the magnetic fields still meshed in a stable configuration, and there was energy to spare to nudge the final assembly precisely into step with the predicted swinging of the Aloof's beam.

"Glory", set in the same story universe as "Riding the Crocodile", is about two women who travel to the world of the Noudah. The Niah, ancestors of the Noudah, spent three million years studying mathematics. The women want to study Niah artifacts, hoping to find out what the Niah learned. They rushed to the site because the artifacts were in danger of being destroyed.

Joan said bluntly, "The present Noudah culture, both here and in Tira, seems to hold the Niah in contempt. Dozens of partially excavated sites containing Niah artifacts are under threat from irrigation projects and other developments. That’s the reason we couldn’t wait. We needed to come here and offer our assistance, before the last traces of the Niah disappeared forever."

"Glory" does begin with the careful construction of a needle that is ultimately sent hurtling through space at close to the speed of light. But the needle ends up plunging into the heart of a star, the shockwaves of its impact causing the construction of something else.

In effect, the shock waves formed a web of catalysts, carefully laid out in both time and space, briefly transforming a small corner of the star into a chemical factory operating on a nanometer scale.

The end product of this and subsequent elaborate and near magical processes were nanomachines, which prepared the way for the embodiment of digitized human beings that were to follow.