The main question is why they don’t wage visible wars with each other? Because in the case of war for the territory the earlier you start, the more you gain (for the future computations).
One possible sign of such war would be sending messages addressed to naive civilizations as our, in order to enslave it by powerful AI—I called it SETI-attack. But we don’t see such messages.
The main question is why they don’t wage visible wars with each other?
Visible to whom and how do you know?
Letting a lot of energy escape while destroying something is crude and inefficient. E.g. a nanobot swarm or an information system takeover would leave nothing you’d recognize as war. Plus, are you quite sure some types of (super)novas are not starkillers in action?
Letting a lot of energy escape while destroying something is crude and inefficient.
Scorched earth is the most effective defence, and I would expect to see evidence of civilizations destroying their physical resources on a massive scale. But perhaps the threat of that is what keeps wars from happening.
The rational reasons to go to war are to prevent a future competitor and to gain resources. Scorched Earth removes both of those reasons: if you can destroy your own resources AND inflict some damage on the enemy at the same time, then no-one has rational reasons to go to war. Because even a future competitor won’t be able to profit from fighting you.
If advanced civilisations have automated disagreement resolving processes, I expect them to quickly reach equilibrium solutions with semi-capable opponents.
What happens when the committed scorched-earth-defender meets the committed extortionist? Surely a strong precommitment to extortion by a powerful attacker can defeat a weak commitment to scorched earth by a defender?
It seems to me this bears a resemblence to Chicken or something, and that on a large scale we might reasonably expect to see both sets of outcomes.
No, it doesn’t. Invading you to force you to destroy your own resources is a good way “to prevent a future competitor”. You are not going to do it on your own, so you need to be pushed into this by war.
Not to mention that, historically speaking, reasons to go to war are not often “rational”. WW1 would be a classic example.
No problem. I explore a method to send images up to 1 billion light years (or more) in my article by drawing images from Dyson spheres on a galactic plane.
If your messages which take millions of years to arrive are relevant to a war, the war also goes on for millions of years. Why would you expect to see anything change over a mere century or so?
Intergalactic war may go for million of years. But humans now are naive civilization and the first who can affect it by ideas of a computer program will win it. Basically it would help to convert Earth in a remote fortress which will help to start colonization of our part of the universe. As a result, a territory of the message sender would grow .
Meh. For a war waged over millions of light years (and, necessarily, lasting millions of years) what can Earth offer? Some atoms? They are easily found elsewhere.
When I discussed the idea of Alien AI I met two points of view:
1) AI is impossible.
2) EY: AI will travel with almost the speed of light
I think it worth consider the intermediate point of view, that is 0.5 с as the total speed of colonization.
Reasons:
Colonization speed is lower than the speed of travel of the von Neumann Probes, as they need some time to replicate.
It is lower than cruise speed of the probe, as it needs some time to accelerate and decelerate. Declaration of the high-speed probe is especially difficult.
Closer to с speeds require much more energy because of the special relativity, so energy investments will produce diminishing returns in the speed of colonization.
If a civilization is remote, the universe acceleration will also work against it perceived speed of colonization.
High speed creates a lot of problems with space dust, which require heavier protection shields.
So, 0.5-0.7с speed are a realistic estimate for the maximum speed of space colonization.
And though it mentions 0.5c for fission engines, most “realistic” probe designs will be much faster, because you can use more exotic things like bussard ramjets to decelerate (using them to accelerate, the way they were originally designed, is harder that it seems, but they are perfect to decelerate). Also Eric Drexlers’s been working on some interesting dust shielding designs. So the paper is very much “conservative” in its assumptions.
It is possible that total colonization wave speed is much higher, closer to с, but I suggest just to put some weight to the hypothesis that is around 0.5-0.7c because of some unknown tradeoffs. I would estimate such outcome as 30 per cent. Only in that case observing alien astroengineering and SETI is possible.
Do you have a nice reference (speculative feasibility study) for non-rigid coil-guns for acceleration?
Obvious idea would be to have a swarm of satellites with a coil, spread out over the solar system. Outgoing probe would pass through a series of such coils, each adding some impulse to the probe (and doing minor course corrections). Obviously needs very finely tuned trajectory.
Advantage over rigid coil-gun: acceleration spread out (unevenly) over longer length (almost entire solar system). This is good for heat dissipation (no coupling is perfect), and maintaining mega-scale rigid objects appears difficult. Satellites can take their time to regain position (solar sail / solar powered ion thruster / gravity assist). Does not help with g-forces.
Disadvantage: Need a large number of satellites in order to get enough launch windows. But if we are talking dyson swarm anyway, this does not matter.
How much do we gain compared to laser acceleration? Main question is probably: How does the required amount of heat dissipation compare?
I have not seen any papers about it, but did look around a bit while writing the paper.
However, a colleague and me analysed laser acceleration and it looks even better. Especially since one can do non-rigid lens systems to enable longer boosting. We developed the idea a fair bit but have not written it up yet.
Do you have a non-paywalled link, for posterity? I use sci-hub, but paywalls are a disgrace to science.
Also, do you have a nice reference for the bussard ramjet/ramscoop deceleration?
Obvious advantage: A priori you don’t need nuclear fusion at all. You use a big em-field for cross-section and use, ultimately, drag against the interstellar medium for both deceleration and energy generation. No deceleration needed in (thinner) intergalactic medium. Entropy gain should be large enough to run mighty heat-pumps (for maintaining high field superconductors and radiating excess heat). No need to carry fuel or manage fusion; your kinetic energy at relativistic speeds has almost as much energy as antimatter. Antimatter sucks because production, containment, and difficulty of not frying yourself with the resulting radiation (light probe cannot shield against gamma), and probably a couple more reasons.
Disadvantage: not obvious whether this works. I would appreciate an actual engineer doing the computation. (I am just a mathematician, and have not seen a study of this deceleration design because I suck at searching the literature)
Probably at least three problems:
(1) How much impulse at what speeds? Determined by cross-section of collecting EM-field over required mass of collector.
(2) Might be good for decelerating from 0.9c to 0.05c over maybe 10k years (pulling numbers out of my ass). Would still need secondary system for the remaining deceleration, until slow enough for gravity assists. Could collect propellant over the long deceleration, but then would need to dissipate a shitload of heat; unclear whether net gain.
(3) Heat dissipation.
I agree that deceleration is the thing to care about; beat the rocket equation on deceleration by clever designs using the interstellar medium, and on acceleration by big machines.
Question: I suppose it’s implicitly assumed that FTL travel is physically impossible even for extremely advanced civilizations, are there reasons to feel relatively secure in our belief that aliens will not have discovered some sort of exotic or unknown physics that allows them to achieve that?
The main question is why they don’t wage visible wars with each other? Because in the case of war for the territory the earlier you start, the more you gain (for the future computations).
One possible sign of such war would be sending messages addressed to naive civilizations as our, in order to enslave it by powerful AI—I called it SETI-attack. But we don’t see such messages.
However, we still could find them, if medium distance between civilization is in order 100 mln −1 bln light years, and physical travel is below 0.5 c I explore these limitations on the civilization density here: https://www.academia.edu/30029491/The_Risks_Connected_with_Possibility_of_Finding_Alien_AI_Code_During_SETI
Visible to whom and how do you know?
Letting a lot of energy escape while destroying something is crude and inefficient. E.g. a nanobot swarm or an information system takeover would leave nothing you’d recognize as war. Plus, are you quite sure some types of (super)novas are not starkillers in action?
Scorched earth is the most effective defence, and I would expect to see evidence of civilizations destroying their physical resources on a massive scale. But perhaps the threat of that is what keeps wars from happening.
That doesn’t look true to me.
If you can pull it off, it works against any opponent no matter how powerful they are.
I don’t know to which extent “I’ll cut my throat and bleed on you” counts as an effective defense...
The rational reasons to go to war are to prevent a future competitor and to gain resources. Scorched Earth removes both of those reasons: if you can destroy your own resources AND inflict some damage on the enemy at the same time, then no-one has rational reasons to go to war. Because even a future competitor won’t be able to profit from fighting you.
If advanced civilisations have automated disagreement resolving processes, I expect them to quickly reach equilibrium solutions with semi-capable opponents.
What happens when the committed scorched-earth-defender meets the committed extortionist? Surely a strong precommitment to extortion by a powerful attacker can defeat a weak commitment to scorched earth by a defender?
It seems to me this bears a resemblence to Chicken or something, and that on a large scale we might reasonably expect to see both sets of outcomes.
No, it doesn’t. Invading you to force you to destroy your own resources is a good way “to prevent a future competitor”. You are not going to do it on your own, so you need to be pushed into this by war.
Not to mention that, historically speaking, reasons to go to war are not often “rational”. WW1 would be a classic example.
I think that in the case of star wars they may need allies in the remote parts of the universe and so will send SETI messages.
Messages sent at the speed of light..? To “remote parts of the universe”? Consider the time scale.
No problem. I explore a method to send images up to 1 billion light years (or more) in my article by drawing images from Dyson spheres on a galactic plane.
If your messages which take millions of years to arrive are relevant to a war, the war also goes on for millions of years. Why would you expect to see anything change over a mere century or so?
Intergalactic war may go for million of years. But humans now are naive civilization and the first who can affect it by ideas of a computer program will win it. Basically it would help to convert Earth in a remote fortress which will help to start colonization of our part of the universe. As a result, a territory of the message sender would grow .
Meh. For a war waged over millions of light years (and, necessarily, lasting millions of years) what can Earth offer? Some atoms? They are easily found elsewhere.
A new starting point to send probes with the half speed of light in all directions in the backland of the enemy.
Any star system will do for that purpose. All you need is star’s energy.
No, you need a traitor behind enemy lines to receive a message and start an attack. Star system without a civ can’t receive a message.
Ah, I see. You’re thinking, basically, about an information plague which, moving at c, leapfrogs physical probes.
See astronomer Fred Hoyle’s A For Andromeda for a fictional exploration of the idea (and a pretty good novel).
I was thinking more of Vernon Vinge’s A Fire Upon the Deep, but yeah, this is not a new idea.
Yes!
Very interesting! But I feel that this is very improbable:
When I discussed the idea of Alien AI I met two points of view:
1) AI is impossible. 2) EY: AI will travel with almost the speed of light
I think it worth consider the intermediate point of view, that is 0.5 с as the total speed of colonization. Reasons:
Colonization speed is lower than the speed of travel of the von Neumann Probes, as they need some time to replicate.
It is lower than cruise speed of the probe, as it needs some time to accelerate and decelerate. Declaration of the high-speed probe is especially difficult.
Closer to с speeds require much more energy because of the special relativity, so energy investments will produce diminishing returns in the speed of colonization.
If a civilization is remote, the universe acceleration will also work against it perceived speed of colonization.
High speed creates a lot of problems with space dust, which require heavier protection shields.
So, 0.5-0.7с speed are a realistic estimate for the maximum speed of space colonization.
I have a paper on that :-)
http://www.sciencedirect.com/science/article/pii/S0094576513001148
And though it mentions 0.5c for fission engines, most “realistic” probe designs will be much faster, because you can use more exotic things like bussard ramjets to decelerate (using them to accelerate, the way they were originally designed, is harder that it seems, but they are perfect to decelerate). Also Eric Drexlers’s been working on some interesting dust shielding designs. So the paper is very much “conservative” in its assumptions.
Thanks for interesting link.
It is possible that total colonization wave speed is much higher, closer to с, but I suggest just to put some weight to the hypothesis that is around 0.5-0.7c because of some unknown tradeoffs. I would estimate such outcome as 30 per cent. Only in that case observing alien astroengineering and SETI is possible.
Second question:
Do you have a nice reference (speculative feasibility study) for non-rigid coil-guns for acceleration?
Obvious idea would be to have a swarm of satellites with a coil, spread out over the solar system. Outgoing probe would pass through a series of such coils, each adding some impulse to the probe (and doing minor course corrections). Obviously needs very finely tuned trajectory.
Advantage over rigid coil-gun: acceleration spread out (unevenly) over longer length (almost entire solar system). This is good for heat dissipation (no coupling is perfect), and maintaining mega-scale rigid objects appears difficult. Satellites can take their time to regain position (solar sail / solar powered ion thruster / gravity assist). Does not help with g-forces.
Disadvantage: Need a large number of satellites in order to get enough launch windows. But if we are talking dyson swarm anyway, this does not matter.
How much do we gain compared to laser acceleration? Main question is probably: How does the required amount of heat dissipation compare?
I have not seen any papers about it, but did look around a bit while writing the paper.
However, a colleague and me analysed laser acceleration and it looks even better. Especially since one can do non-rigid lens systems to enable longer boosting. We developed the idea a fair bit but have not written it up yet.
I would suspect laser is the way to go.
Interesting idea. No, I don’t have any references, sorry!
Do you have a non-paywalled link, for posterity? I use sci-hub, but paywalls are a disgrace to science.
Also, do you have a nice reference for the bussard ramjet/ramscoop deceleration?
Obvious advantage: A priori you don’t need nuclear fusion at all. You use a big em-field for cross-section and use, ultimately, drag against the interstellar medium for both deceleration and energy generation. No deceleration needed in (thinner) intergalactic medium. Entropy gain should be large enough to run mighty heat-pumps (for maintaining high field superconductors and radiating excess heat). No need to carry fuel or manage fusion; your kinetic energy at relativistic speeds has almost as much energy as antimatter. Antimatter sucks because production, containment, and difficulty of not frying yourself with the resulting radiation (light probe cannot shield against gamma), and probably a couple more reasons.
Disadvantage: not obvious whether this works. I would appreciate an actual engineer doing the computation. (I am just a mathematician, and have not seen a study of this deceleration design because I suck at searching the literature)
Probably at least three problems:
(1) How much impulse at what speeds? Determined by cross-section of collecting EM-field over required mass of collector.
(2) Might be good for decelerating from 0.9c to 0.05c over maybe 10k years (pulling numbers out of my ass). Would still need secondary system for the remaining deceleration, until slow enough for gravity assists. Could collect propellant over the long deceleration, but then would need to dissipate a shitload of heat; unclear whether net gain.
(3) Heat dissipation.
I agree that deceleration is the thing to care about; beat the rocket equation on deceleration by clever designs using the interstellar medium, and on acceleration by big machines.
Use Google Scholar to find fulltexts like https://pdfs.semanticscholar.org/847d/8dabb12f67124868af0876c77538e4fd1c60.pdf
Question: I suppose it’s implicitly assumed that FTL travel is physically impossible even for extremely advanced civilizations, are there reasons to feel relatively secure in our belief that aliens will not have discovered some sort of exotic or unknown physics that allows them to achieve that?
Yes, I assume it. If not true, they must be here.
No.
Exactly. FTL is allowed even by relativistic mechanics (who know what allows quantum gravity?), although time travel paradoxes ensue.