Interstellar travel will probably doom the long-term future
Some quick thoughts: By the time we’ve colonized numerous planets and cumulative galactic x-risks are starting to seriously add up, I expect there to be von Neumann probes traveling at a significant fraction of the speed of light (c) in many directions. Causality moves at c, so if we have probes moving away from each other at nearly 2c, that suggests extinction risk could be permanently reduced to zero. In such a scenario most value of our future lightcone could still be extinguished, but not all.
A very long-term consideration is that as the expansion of the universe accelerates so does the number of causally isolated islands. For example, in 100-150 billion years the Local Group will be causally isolated from the rest of the universe, protecting it from galactic x-risks happening elsewhere.
I guess this trades off with your 6th conclusion (Interstellar travel should be banned until galactic x-risks and galactic governance are solved). Getting governance right before we can build von Neumann probes at >0.5c is obviously great, but once we can build them it’s a lot less clear if waiting is good or bad.
Causality moves at c, so if we have probes moving away from each other at nearly 2c, that suggests extinction risk could be permanently reduced to zero.
This isn’t right. Near-speed-of-light movement in opposite directions doesn’t add up to above speed of light relative movement. e.g., Two probes each moving away from a common starting point at 0.7c have a speed relative to each other of about 0.94c, not 1.4c, so they stay in each other’s lightcone.
(That’s standard special relativity. I asked o3 how that changes with cosmic expansion and it claims that, given our current understanding of cosmic expansion, they will leave each other’s lightcone after about 20 billion years.)
Right, so even with near-c von Neumann probes in all directions, vacuum collapse or some other galactic x-risk moving at c would only allow civilization to survive as a thin spherical shell of space on a perpetually migrating wave front around the extinction zone that would quickly eat up the center of the colonized volume.
Such a civilization could still contain many planets and stars if they can get a decent head start before a galactic x-risk occurs + travel at near c without getting slowed down much by having to make stops to produce and accelerate more von Neumann probes. Yeah, that’s a lot of if’s.
20 billion ly estimate seems accurate, so cosmic expansion only protects against galactic x-risks on very long timescales. And without very robust governance it’s doubtful we might not get to that point.
Awesome speculations. We’re faced with such huge uncertainty and huge stakes. I can try and make a conclusion based on scenarios and probabilities, but I think the simplest argument for not spreading throughout the universe is that we have no idea what we’re doing.
This might even apply to spreading throughout the Solar System too. If I’m recalling correctly, Daniel Deudney argued that a self-sustaining colony on Mars is the point of no return for space expansion as it would culturally diverge from Earth and their actions would be out of our control.
Some quick thoughts:
By the time we’ve colonized numerous planets and cumulative galactic x-risks are starting to seriously add up, I expect there to be von Neumann probes traveling at a significant fraction of the speed of light (c) in many directions. Causality moves at c, so if we have probes moving away from each other at nearly 2c, that suggests extinction risk could be permanently reduced to zero. In such a scenariomostvalue of our future lightcone could still be extinguished, but notall.A very long-term consideration is that as the expansion of the universe accelerates so does the number of causally isolated islands. For example, in 100-150 billion years the Local Group will be causally isolated from the rest of the universe, protecting it from galactic x-risks happening elsewhere.
I guess this trades off with your 6th conclusion (Interstellar travel should be banned until galactic x-risks and galactic governance are solved). Getting governance right before we can build von Neumann probes at >0.5c is obviously great, but once we can build them it’s a lot less clear if waiting is good or bad.
Thinking out loud, if any of this seems off lmk!
This isn’t right. Near-speed-of-light movement in opposite directions doesn’t add up to above speed of light relative movement. e.g., Two probes each moving away from a common starting point at 0.7c have a speed relative to each other of about 0.94c, not 1.4c, so they stay in each other’s lightcone.
(That’s standard special relativity. I asked o3 how that changes with cosmic expansion and it claims that, given our current understanding of cosmic expansion, they will leave each other’s lightcone after about 20 billion years.)
Right, so even with near-c von Neumann probes in all directions, vacuum collapse or some other galactic x-risk moving at c would only allow civilization to survive as a thin spherical shell of space on a perpetually migrating wave front around the extinction zone that would quickly eat up the center of the colonized volume.
Such a civilization could still contain many planets and stars if they can get a decent head start before a galactic x-risk occurs + travel at near c without getting slowed down much by having to make stops to produce and accelerate more von Neumann probes. Yeah, that’s a lot of if’s.
20 billion ly estimate seems accurate, so cosmic expansion only protects against galactic x-risks on very long timescales. And without very robust governance it’s doubtful we might not get to that point.
Awesome speculations. We’re faced with such huge uncertainty and huge stakes. I can try and make a conclusion based on scenarios and probabilities, but I think the simplest argument for not spreading throughout the universe is that we have no idea what we’re doing.
This might even apply to spreading throughout the Solar System too. If I’m recalling correctly, Daniel Deudney argued that a self-sustaining colony on Mars is the point of no return for space expansion as it would culturally diverge from Earth and their actions would be out of our control.