Dissolving the Fermi Paradox

[Quickshot0]

Nah, to stay up the average speed per mass of the construct has to be around orbital velocity, or higher (which will place stress on it, I think a simple pure copper wire is unsuitable, probably some engineered material instead (also makes failures more entertaining, those rarely fail gracefully in my experience) which will also make the whole induction / maglev system easier to work with) and at that point, if there is a collision, you'll get some lateral velocities involved, the debris would spread across the entire orbit spectrum around it.

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You are answering to the original proposed idea on how to make an orbital ring, the proposal I made has no such thing.

The one I proposed is just a static ring slightly spun up with for instance a mag-lev section below it.* The orbital debris spectrum is almost completely sub-orbital speeds as such. Assuming you some how got a collision between the train and the ring.

And there this was just an improvement I thought up of in a few minutes, I'm pretty sure further ones could be made to reduce risks even more. But in any case there is no need for some kind of enormous active structure to already get a reasonable portion of the benefits.


* The drawback being this would allow for less mass to be drawn from the surface quickly as you can't spin it up to much, but I'm not sure how much that really matters in actual effective transport rates.

 

[terma]

No, even in your case, the average velocity is orbital or above, if it's not, it would fall . The maglev train still needs to be close to the ring, riding almost immediately along it, otherwise power costs are going to be exorbitant and just making it a maglev system alone makes it significantly costlier by going from inside a solenoid to, well, not so. I'll admit that the failure is less direct, but a power failure in one train will cause it to drop, causing a wobble because the equivalent train on the other side won't drop immediately. This will cause the ring to locally go higher and slower and start a slightly more eccentric orbit and that's going to be tricky to correct, can cause collisions, and is hard to set up in the first place. I have to say that the proposal appears inherently unstable, and I'm not sure how easy it would be to set up in the first place without increasing orbit eccentricity.

Back to Fermi, I guess those physical limits are our great filter?

 

[Quickshot0]

No, even in your case, the average velocity is orbital or above, if it's not, it would fall . The maglev train still needs to be close to the ring, riding almost immediately along it, otherwise power costs are going to be exorbitant and just making it a maglev system alone makes it significantly costlier by going from inside a solenoid to, well, not so. I'll admit that the failure is less direct, but a power failure in one train will cause it to drop, causing a wobble because the equivalent train on the other side won't drop immediately. This will cause the ring to locally go higher and slower and start a slightly more eccentric orbit and that's going to be tricky to correct, can cause collisions, and is hard to set up in the first place. I have to say that the proposal appears inherently unstable, and I'm not sure how easy it would be to set up in the first place without increasing orbit eccentricity.

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Sure it would be a bit above orbital speed, but that doesn't actually contribute to the scenario you suggested due to it being so low in the first place and any debris thus having a low orbit crossing point. Further instabilities can be corrected via for instance the wires themselves, which obviously allow you via their tension to move the exact ring position around and thus can counter out instability. And if that fails you can always use a fallback thruster system. And if that fails you could for instance segment the ring apart and let them drift in orbit till you can get around to attaching them back together. There are plenty of ways to resolve these kind of problems quite well.

Really these aren't particularly dangerous failure scenarios and you have plenty of time to react to them in quite sane ways. Frankly if one thought every lesser failure scenario in mega engineered structures ever made things inherently non-viable, then there are quite some things we'd have never built that work fine. Like say the dam systems in The Netherlands, that inherently have a catastrophic failure mode, but are totally cost effective and work well enough. Or tall buildings that would collapse if their central support gives way. Jet engines that run hotter then their thermal tolerance ability.

The real question is if you can mitigate risks down to a reasonable level, and I see no sign that in my proposal this isn't eminently doable.

Back to Fermi, I guess those physical limits are our great filter?

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Not a chance, it's to easy to get around the galaxy.

As such it probably is something that precludes getting to the galactic expansion phase. Be it like the article suggests because Habitable worlds are rare and thus few places can develop to that stage, or that we're simply one of the first, or perhaps that most Habitable worlds just don't survive long enough. (Earth is nearing the end of its habitable phase, probably just 0.5 to 1 billion years left)

Plenty of other reasons could be considered as well I guess, like the first species really likes to make large galactic sized preserves and won't let anyone say otherwise. Or near interstellar civs can eradicate themselves rather easily... Well the options go on and on really.

In any case whatever the case we still don't really know what it is with any certainty. Which is slightly worrying, as some of those options could be dangerous to us. So hopefully the reason is already behind us, rather then still ahead of us.

 

[terma]

Windmills and berms don't fail catastrophically, they just fail, while they do salt the ground when they do, you can plug the holes and get the pumps going again. A Kessler syndrome is something else.

I'll admit I haven't done the math, but I wonder what sorts of materials would allow you to control tension and so on in the ring. Also note that each active system within it makes one more possible failure point. (On the other hand, making the ring more and more massive is a good idea and makes salvaging them more likely in case of a problem, I agree.) (I'm also interested to see how well they'll deal with tidal effects, but not enough to do it myself.)

The thing about elevators is that they are relatively simple, passive structures, they don't require power to be fed in for them to keep working, and that appeals to me, downtime might be horrible, but it's far more likely there'll be something to salvage.

 

[Quickshot0]

Windmills and berms don't fail catastrophically, they just fail, while they do salt the ground when they do, you can plug the holes and get the pumps going again. A Kessler syndrome is something else.

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I presume this is a reaction to the claim dams fail catastrophically. And if you really believe just some pump work and so is enough, it really isn't. A major dam break will erode away the surrounding dam and cause a massive influx of water, it's basically a catastrophic failure with little ability to counter.

In any case, there have been some suggestion on ways to deal with Kessler syndrome induced debris, including stuff like using a laser to burn away the smallest stuff and induce thrust on some what larger parts, so as to force their orbit to intersect the atmosphere. For larger pieces there are some proposals here. But basically orbital clutter can be recovered from, albeit at a price.


As such I don't think we can expect aliens to stay locked up on their home world if they don't want to be, even if they did suffer a Kessler syndrome disaster.

 

[terma]

Oh, yeah, dams do break catastrophically, selective reading, my bad. But they mess up a single drainage basin, and perhaps a neighboring one, debris going off at odd angles in low orbit is a global problem.


My problem with those collection efforts is one of scale, an orbital ring is enormous, the amount of debris it could generate is enormous, the clean-up mechanisms would be of a scale beyond that, it could be bad enough that only ground based solutions could work at the beginning of a clean up because space based ones would just get chopped apart. Hence decades.

I'm not saying it's impossible, I'm saying there's a lot more effort and technology involved in it, and that making one responsibly requires even more of that. (And, again, that the structure's very existence is unstable, that's a big one.)

 

[Quickshot0]

I think I'll stop this increasingly off-topic discussion here and just leave it with the summary of, I think you're worrying to much about things that can just be engineered for. It all seems a little to much like a 'couldn't possibly solve this' type of attitude, rather then truly seriously questioning if the raised questions can't be answered by one self already if one just thinks about it for awhile and looks around online a bit perhaps.


Hmmm... well nothing further comes to mind to say about Fermi's paradox at this point either though, I think most of it has been said already.

 

[firefossil]

Oh for fuck's sake...

INVERSE SQUARE LAW. By the time a radio signal from multiple star systems away reaches us, its going to be indistinguishable from background radiation.

The Fermi Paradox was never a paradox to begin with. The universe could be teaming with high tech civilizations that are incapable of contacting each other.

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We won't hear general radio noise from other solar systems, yes. However the amount of energy required to communicate across interstellar distances is not particularly high. See this article on communicating with an interstellar probe at Alpha Centauri 4.34 year light years away...

Communications lasers would use 0.532 micron wavelength since there is minimal power output by the stars in that frequency band. A laser with an input power of 250 kilowatts would allow for a data rate of 1000 bits per second at maximum range.

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With a shrimpy 250 kilowatt laser. To some extent bloom is a good thing, you'd ideally want a bloom that simply covers the whole solar system, while still maintaining enough strength to be be detected by alien SETI using the kind of stuff we currently use to look for alien signals. It wouldn't be hard to just start badgering nearby stars with periodic "we're here, come pick up the phone" messages. The energy cost and laser array size is all within conventional human standards.

 

[Quickshot0]

We won't hear general radio noise from other solar systems, yes.

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Yes we would, the upcoming square kilometer array can detect television transmitter level powers out to dozens of light years range.

It's at the end of this article, just to name a source.


Basically the idea that background radiation would make something undetectable for us was an incorrect line of thinking, as we can subtract that radiation from what we get and see if there are any excess anomalies. This is because the background radiation behavior is known to rather high precision, so one can see way way below the noise threshold.

 

[PhoenixMercurous]

Yes we would, the upcoming square kilometer array can detect television transmitter level powers out to dozens of light years range.

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Dozens of light years is tiny compared to the size of the galaxy, which is ~100,000 ly in diameter.

 

[Quickshot0]

Dozens of light years is tiny compared to the size of the galaxy, which is ~100,000 ly in diameter.

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Obviously, yes, I certainly wasn't trying to make that argument.


Instead it's just a note that the noise floor doesn't stop you from detecting things.

And I guess it allows a naive extrapolation for the size of radio telescope you would need. So far I can tell by rough guesstimate, you'd need an instrument a few thousand kilometers long on each side, assuming you made it as a single instrument. Which we don't do with modern ones, instead being arrays of many smaller ones. So physically speaking there is no problem, though economically it might very well be. Though who knows what future century economies can afford?

Now as for a potential blocker, I don't really know if you can keep beating the background radiation to that degree I really couldn't say for sure. Though it doesn't seem entirely implausible from my sketchy knowledge on it, an expert would know more though, or maybe if one googled around for it something could be found to settle the matter.


So as such in the end it's just a comment that perhaps communication detection isn't actually impossible, as one person had suggested. What to further make of it would take further consideration on its implications and in what arguments one wants to use it in.

 

[firefossil]

Dozens of light years is tiny compared to the size of the galaxy, which is ~100,000 ly in diameter.

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Dozens of light years basically covers "any place we might consider sending a generation ship to" and "enough to have a very very slow conversation". It also would be a quick test of the "intelligent life is common but interstellar travel is rare to nonexistent" hypothesis.

And I guess it allows a naive extrapolation for the size of radio telescope you would need. So far I tell by rough guess, it would be a few thousand kilometers long on each side if you made it as a single instrument. Which we don't do with modern ones, instead being arrays of many smaller ones. So physically speaking there is no problem, though economically it might very well be. Though who knows what future century economies can afford?

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It'd also probably be a space based array orbiting the sun or somesuch, as in space you have infinite empty room to space your array of telescopes however you feel like. You could make a Square AU Array if you so felt like it. Though given the nature of how signal strength declines as a square of the distance it could still be difficult.

 

[Catty Nebulart]

Nah, to stay up the average speed per mass of the construct has to be around orbital velocity, or higher (which will place stress on it, I think a simple pure copper wire is unsuitable, probably some engineered material instead (also makes failures more entertaining, those rarely fail gracefully in my experience) which will also make the whole induction / maglev system easier to work with) and at that point, if there is a collision, you'll get some lateral velocities involved, the debris would spread across the entire orbit spectrum around it.

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Nah the materials strength of the copper is irrelevant, you could use particle beams or anything else that carries momentum and can be pushed off of by magnets. Copper is usually used as an example because it;s not exotic, easy to work with, relatively cheap etc. If the orbital ring fails... it's going to be a disaster, like a bridge failing, except more widespread. it's not going to be that bad for orbital debris though, the inner copper wire should be way above escape velocity while the bulk of the ring is stationary. Yes some will be dragged by friction into orbit but that should be a minuscule fraction at most. Furhter you can design it to break apart on structural failure and have parachutes on the pieces so they come down gently. It's not going at orbital speed so it will just gently fall.

Even if you don't you have minutes to warn the people under it to get out of the danger zone, and any large ring should have multiple rings for redundancy, so the possibility for disaster is not that bad. Now if you build on truly immense scales and build a shell-world or something then the calculus is very very different, but for a small number of rings it should be fine. As for stability, remember that you are floating on a sea of magma with an ill understood convective system, and the thin layer of rock you are standing on is drifting and parts of it are sinking, yet you have no trouble assuming that bedrock is solid and stable.

Yes and Orbital elevator would also work, but it needs magical materials, and it is still more expensive and has less throughput and uses than an orbital ring.

The risky rings for Kessler syndrome is once you have several at different inclinations and heights, including a bunch well above 100km so their debris won't decay fast, and different inclinations means they can impact at speed. But if you are a civilization with dozens of orbital rings.... It should not be a problem.

 

[Quickshot0]

Yes and Orbital elevator would also work, but it needs magical materials, and it is still more expensive and has less throughput and uses than an orbital ring.

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The statement 'magical' kind of bothers me here, for Earth it's still with in the physically possible realm. Admittedly it's pretty close to the reasonable limit, meaning you'll have to be true master material engineers to create what you need at the quality level you need. But it is thus possible with in actual physics, and so not 'magical'. It would be how ever be truly astonishing to see.


Though this continuing discussion kind of makes me wonder if a thread on space mega-engineering would be worthwhile or not.

 

[PhoenixMercurous]

Nah the materials strength of the copper is irrelevant

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You have a continuous, solid ring being loaded by a radially inward force. In the ring's rest frame, this is exactly the idealization used to model cylindrical inverse pressure vessels, like a vacuum chamber or a submarine. The mechanical strength of the material will matter. If you used a particle beam the force would, AFAIK, end up being carried by electrostatic interactions between particles in the beam.

Edit: Wait, it's not quite exactly the same, the Lorentz force and gravity are body forces, not surface tractions. That complicates the matter quite a bit. I'm inclined to think the strength would still matter, especially because the bottom of the ring would be moving slightly slower than the top, but I'm not entirely sure.

Edit 2: In the case of a particle beam, which would be approximately infinitely thin, the difference between tractions and body forces vanishes, so the thin walled pressure vessel approximate should still hold, so there should be a compressive force along the particle beam. The solution for a finite thickness ring (ie a copper ring) should give the same result for an infinitesimal ring as the infinitesimal approximation, so there ought to be a compressive force along a finite thickness ring. Even a copper ring would be approximately infinitesimally thin compared to the radius of the ring, so the thin walled pressure vessel approximation might still work for the copper as well.

I may have to think a bit more on this...

 

[Catty Nebulart]

I may have to think a bit more on this...

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Well let's simplyfy take a cross section, the copper ring experiences a radially outward force, Fc, the magnets are more complicated since they need to confine the copper, but the only one that matters is the one on top which pushes downward with the mass of the magnets and everything else on its slice of ring. Let's call it Fm.

Material strength of the copper doesn't matter let's say it melts, is still on a ballistic trajectory that generates the Fc force outward. X amount of mass will flow through the cross section and needs to be deflected to stay in the circle. It will be squished and deformed but the nature doesn't change. You are limited by the strength of the magnet. You can also stack multiple rings and magnets side by side spreading Fm and making it required magnitude smaller.

You can then stack these slices together till they form a ring and the force of each slice is independent. (Well in an idealized simple scenario)

Contrast that with a spaceelevator cable, where the is a tension force on each point that is the sum of all the weight beneath it and the force required to hold it up... You can't simply attack the slides because the forces change, and you can't distribute the forces by running multiple cables because each one needs to lift it's own weight.

 

[Quickshot0]

Contrast that with a spaceelevator cable, where the is a tension force on each point that is the sum of all the weight beneath it and the force required to hold it up... You can't simply attack the slides because the forces change, and you can't distribute the forces by running multiple cables because each one needs to lift it's own weight.

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Well kind of the case with the cables, though tapering is an option. Which means you can have a thicker cable section at the highest stress location and a thinner at a less stressed area.

Admittedly this does have very real limitations, which for instance makes a steel cable completely infeasible for Earth, as the tapering is so extreme as the make the cable its own planet scale object. So the trick is really to at least find a material strong enough to bring the tapering to a some what acceptable level.

For Earth this is still possible in principle, based on what we know of material science. Though in practice we can't actually make materials of any real length yet of such strengths. Still, it's something one could perhaps achieve in one of the future decades.

 

[PhoenixMercurous]

Well let's simplyfy take a cross section, the copper ring experiences a radially outward force, Fc, the magnets are more complicated since they need to confine the copper, but the only one that matters is the one on top which pushes downward with the mass of the magnets and everything else on its slice of ring. Let's call it Fm.

Material strength of the copper doesn't matter let's say it melts, is still on a ballistic trajectory that generates the Fc force outward. X amount of mass will flow through the cross section and needs to be deflected to stay in the circle. It will be squished and deformed but the nature doesn't change. You are limited by the strength of the magnet. You can also stack multiple rings and magnets side by side spreading Fm and making it required magnitude smaller

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You haven't considered the distribution of forces inside the copper, nor mechanical equilibrium. The situation is more complex than you realize, a simple free body diagram isn't going to suffice. Full disclosure, I forgot about the acceleration last time so I wasn't completely correct.

You also have the issue that copper is diamagnetic and electrically neutral, so a spinning ring of copper won't interact with a magnetic field and more than a static ring would. I mentioned this before, but you seemed to miss it.

 

[IndyFront]

I think its likely we are the first advanced civilization of our type of organism, but I think it is folly to think that we are the first advanced form of life period. There are other advanced, really intelligent forms of life on this planet with us at this moment that are considered uncivilized simply because they do not have opposable thumbs or technology.

 

[mesonoxian]

The difficulties and costs of living away from Earth vastly outweigh any plausible benefits. No signal we send out is likely to be especially noticeable to extraterrestrial observers. The same limitations apply to alien life. I don't think there is anything paradoxical about not encountering life that evolved around other stars.

 

[Quickshot0]

The difficulties and costs of living away from Earth vastly outweigh any plausible benefits.

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That's quite the claim to make, especially as we do know there is a lot of quite valuable resources in space. Do you have any particular reason to think these will be eternally uneconomic to exploit?

 

[mesonoxian]

That's quite the claim to make, especially as we do know there is a lot of quite valuable resources in space. Do you have any particular reason to think these will be eternally uneconomic to exploit?

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Exploiting them economically won't require us to live in space. We exploit resources in inhospitable places like deep underground or the middle of the ocean, but we don't colonize them. We just send a few technicians to run the machines doing the extracting.

 

[Quickshot0]

Exploiting them economically won't require us to live in space. We exploit resources in inhospitable places like deep underground or the middle of the ocean, but we don't colonize them. We just send a few technicians to run the machines doing the extracting.

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True, you only need some people out there in such a model.

Well then, lets look at it from a different angle. There are a lot of people who don't seem to care that our planet might be a bit easier to live on. We could look at them perhaps as being some what like the people who left Europe for the America's back in the day. Those who want to start something new run their way, not how it's done at home. And they're willing to pay extra for it.

For such people, is there a reason to think that an O'Neill Cylinder would forever be out of their price range? It's expensive, yes, but it doesn't seem impossibly so. And if you are extracting resources in space already, you can source many of the needed materials locally.


So basically, is there a reason to think that it will remain unaffordable for people who want such things for all time?

 

[mesonoxian]

True, you only need some people out there in such a model.

Well then, lets look at it from a different angle. There are a lot of people who don't seem to care that our planet might be a bit easier to live on. We could look at them perhaps as being some what like the people who left Europe for the America's back in the day. Those who want to start something new run their way, not how it's done at home. And they're willing to pay extra for it.

For such people, is there a reason to think that an O'Neill Cylinder would forever be out of their price range? It's expensive, yes, but it doesn't seem impossibly so. And if you are extracting resources in space already, you can source many of the needed materials locally.


So basically, is there a reason to think that it will remain unaffordable for people who want such things for all time?

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Living in habitats within the solar system, close enough to be supplied from Earth, makes the prospect feasible. I can't imagine it being terribly desirable, though. The price is enormous, and the potential for catastrophic failure is much greater than living Earth bound. And when these things fail, the cost in lives and resources would be staggering.

The people who left Europe to go to the Americas were going to an already heavily human altered part of the same planet, and they still died in droves because living far away from a technological and agricultural support base means you have very little margin for failure. The European emigrants got an entire continent of resources to exploit for their troubles. Our O'Neill colonists are getting a small island's worth of territory, and materials they already paid for and shipped there, except in a much less stable environment.

So yes, if someone wanted to build near Earth orbital habitats, they could probably make them viable on the short term. But I don't see any plausible benefit that comes close to offsetting the costs and risks involved.

 

[Quickshot0]

I don't really agree with your risk assessment, space is a very dull environment. This means there aren't a lot of surprises and once you've solved a problem in a reliable way, it will tend to remain that way.

So certainly, if you say built an O'Neill cylinder in a stupid and foolish way, it could be a major catastrophe risk. But it's not like you have to though, while I imagine early versions might, with refinement they'd probably eventually become very reliable. Like other major engineered systems that are well enough understood.

As such I'd argue long term space is probably the safer habitat, unlike Earth where the planet itself is constantly prone to high energy events causing catastrophes over large areas. From Hurricanes to flooding, or Earthquakes to Tsunamis. We've engineered ourselves to do better against them, but even now they are far from a fully solved problem.


Another factor would be if WW3 ever happened, then everyone being in one very small area (ie a planet) might be pretty dangerous. Being off world might have a higher survivability then being near ground zero of such a conflict.


As such I'm seeing at least two plausible benefits space has on Earth.