3 ms·

Think “matter scanner/printer”. Scan an object, at atomic & energy vector level. Transmit that information to a destination’s printer. Expansion is then indeed

Think “matter scanner/printer”. Scan an object, at atomic & energy vector level. Transmit that information to a destination’s printer. Expansion is then indeed at speed of light, capped only by need to physically move a small “seed” printer (rapid transport may have enormous energy cost, but that’s all that needs moving; everything else is just data). Having seen tech go from digital imaging to 3D organ printing in a fraction of my lifespan, seems plausible.

lisper 6y ago
But first you have to deliver the printer to the destination somehow.
- TeMPOraL 6y ago
  Here's an idea. Imagine you have a way to build von Neumann probes that can boost themselves to some high fraction of c (say, 0.9). You start pumping them out in your home system, and send them towards some stars - not necessarily the closest ones. You keep sending them. There's now a shell expanding at 0.9c that's shaped by your production capabilities. Of course, the probes will spend time accelerating and then decelerating towards their destinations. But even as they decelerate, other probes, going to further targets, pass ahead of them. Any probe that lands in a system sets up a facility for building and provisioning more of itself, and sends those to further star systems, adding to the wave. Meanwhile, any technological advancement could be transmitted at the speed of light - so the probes receive improvement instructions as they fly, and the entire shell keeps upgrading itself as it expands. What's the aggregate speed of that shell? Less than 0.9c, I think, but I'd say it's still a high fraction of it. The main warning sign we could look for, assuming there are no crazy unknown physics allowing creation of silent drives, are deceleration plumes and associated thermal emissions. But then, civilizations like ours should be easy to spot from a distance. Don't bother with radio waves, just look at the spectral lines of the planets in a system; if you spot high concentrations of chemicals that don't have geological rationale to be there (such as oxygen in our case), this implies something is keeping the planet away from equilibrium - likely some form of life. If we go by Dark Forest theory, the standard procedure upon detection of such "life signs" would be to send updated instructions to the von Neumann probe heading towards that system: "don't decelerate, ram the planet (or the star) at 0.9 c". If there's anything of use left there, another probe will come later and consume it. So, by the time we spot the evidence of the von Neumann probes, we may just be about to get hit by a relativistic kill vehicle at the vanguard of the expanding shell. (I'm tempted to build a toy model and play with the parameters to see how much of an advance warning we would have.)
  - gmuslera 6y ago
    Suppose that there is no need to have in the equation living beings. So you have your von Neumann probes assimilating all the matter in their path into new von Neumann probes, lets call them Borg von Neumann. And they are nodes of a collective /distributed "computing" scheme called Alien Civilization 3.0. Still you need time to stop, make your conversion, pick next target, accelerate and deaccelerate. And you may be turning everything into nodes, i.e. suns, exoplanets, etc. As we find stars pretty far away and exoplanets in far away solar systems, we are safe for some million years at the very least, even with relativistic speeds. And still, it is about what we think with the wrong mindset and a lot of unknown unknowns to properly understand the problem. Expanding may be obviously wrong for advanced enough... something.
  - ctdonath 6y ago
    Would make a great toy, implemented along the lines of Universal Paperclips.
- ctdonath 6y ago
  Yes, but a whole lot easier to deliver a printer than a functioning civilization, when you can just print a civilization.

lisper 6y ago

But first you have to deliver the printer to the destination somehow.

TeMPOraL 6y ago
Here's an idea. Imagine you have a way to build von Neumann probes that can boost themselves to some high fraction of c (say, 0.9). You start pumping them out in your home system, and send them towards some stars - not necessarily the closest ones. You keep sending them. There's now a shell expanding at 0.9c that's shaped by your production capabilities. Of course, the probes will spend time accelerating and then decelerating towards their destinations. But even as they decelerate, other probes, going to further targets, pass ahead of them. Any probe that lands in a system sets up a facility for building and provisioning more of itself, and sends those to further star systems, adding to the wave. Meanwhile, any technological advancement could be transmitted at the speed of light - so the probes receive improvement instructions as they fly, and the entire shell keeps upgrading itself as it expands. What's the aggregate speed of that shell? Less than 0.9c, I think, but I'd say it's still a high fraction of it. The main warning sign we could look for, assuming there are no crazy unknown physics allowing creation of silent drives, are deceleration plumes and associated thermal emissions. But then, civilizations like ours should be easy to spot from a distance. Don't bother with radio waves, just look at the spectral lines of the planets in a system; if you spot high concentrations of chemicals that don't have geological rationale to be there (such as oxygen in our case), this implies something is keeping the planet away from equilibrium - likely some form of life. If we go by Dark Forest theory, the standard procedure upon detection of such "life signs" would be to send updated instructions to the von Neumann probe heading towards that system: "don't decelerate, ram the planet (or the star) at 0.9 c". If there's anything of use left there, another probe will come later and consume it. So, by the time we spot the evidence of the von Neumann probes, we may just be about to get hit by a relativistic kill vehicle at the vanguard of the expanding shell. (I'm tempted to build a toy model and play with the parameters to see how much of an advance warning we would have.)
- gmuslera 6y ago
  Suppose that there is no need to have in the equation living beings. So you have your von Neumann probes assimilating all the matter in their path into new von Neumann probes, lets call them Borg von Neumann. And they are nodes of a collective /distributed "computing" scheme called Alien Civilization 3.0. Still you need time to stop, make your conversion, pick next target, accelerate and deaccelerate. And you may be turning everything into nodes, i.e. suns, exoplanets, etc. As we find stars pretty far away and exoplanets in far away solar systems, we are safe for some million years at the very least, even with relativistic speeds. And still, it is about what we think with the wrong mindset and a lot of unknown unknowns to properly understand the problem. Expanding may be obviously wrong for advanced enough... something.
- ctdonath 6y ago
  Would make a great toy, implemented along the lines of Universal Paperclips.
ctdonath 6y ago
Yes, but a whole lot easier to deliver a printer than a functioning civilization, when you can just print a civilization.