a. We’re 100% sure flying cars and passenger rockets to other planets are possible, just like we were sure in the 1960s they were possible. And we have helicopters and Mars rovers, so we are more certain than we were then that they are feasible.
b. You’re picking way too short of a timescale. Even if it takes another million years for humans to build a von neuman starship, that’s nothing. A century is as far back as your horizon goes, and yes, lots of errors were made, but mainly because the people back then didn’t even know about a number of tricks that have since then been discovered. (like nuclear energy, compact computers via silicon lithography, jet engines and so on)
I think that theory is entirely plausible, yes. But I can’t sign-up for your newsletter because of all the personal belief that I’d have to suspend to get on-board with (what I see as) an oversimplification of the matter. And I’m not just digging on you Lumpy. In fact, i appreciate your question as I’d not considered that perspective. My horizons have been broadened by this discussion.
However, I’d quickly discount most anyone’s theories on extra-terrestrial intelligence because we.just.dont.know. Until we have a secondary reference, our measurement standards are all suspect. Even a secondary reference is going to introduce its own complications, but it’ll be twice as good as what we’ve got.
It’s incredibly difficult to separate the human from this discussion since we all think we’re (cosmically speaking) so freakin’ great. And why shouldn’t we? We, without question, are the greatest things in the universe so it makes sense that we’d use our mathematics and reasoning to predict what else may be out there.
My first thought when reading your OP was, “that’s an incredible assumption to make… that wood is only found on Earth.” Then I realized that, hey, wood IS only found on earth! :smack:
Yes it’s true we have a great deal of brain hardware dedicated to communication.
But it’s also true that almost all of modern science, and much that humans do in general, is working with phenomena that we do not directly detect or have custom hardware for.
As Half Man Half Wit says, we have a general intelligence we can apply to solve problems of any kind.
And nature includes many very complex phenomena that only drip-feed data to us. Data that we need to use incredibly complex equipment to detect in the first place. But we can still solve and understand such problems.
Language, by comparison, is vast amounts of data in many forms of media. An embarrassment of riches of data.
And it’s not a hideously complex protein that nature has not deigned to label for us: it’s structured data, it’s organized.
The final part of your objection is maybe they will not have concepts of “me” and “you” or whatever.
Well, yeah, maybe. We can’t rule anything out. Maybe aliens will come to Earth, get addicted to rockabilly music, and dance until their feet-equivalents burst into flames.
To me, the plausibility of those ideas are similar.
Because you are speculating that not only will they not have concepts of first-person or third-person in their language, but they’ll be unable to guess that we are referring to such things, and that this will prevent them from communicating at all, forever, and this will be the case for all interspecies interactions. All these propositions need to be true for this to have any relevance to Fermi’s Paradox.
As an engineer working in rocket and spacecraft propulsion I’d really like to hear about this existing technology that could improve on propulsive performance by “a factor of 20”. So would JANNAF, the AIAA, NASA Jet Propulsion Laboratory, and the Planetary Society to name a few, because such a capability would cut interplanetary mission times from many years waiting for an optimal launch window and then years in transit to being able to send a mission whenever a payload can be manifested and accomplishing a mission in something less than a significant portion of a principal investigator’s career. There is no “modestly optimistic technological advancement” that could propel a vehicle to a relative velocity of 0.05c, or “conceivable tech anything from 20% to 50%” of c, much less carry enough propellant to decelerate at the destination system. Even the temperatures generated by D-T fusion would only provide an I[SUB]sp[/SUB] of 10,000 to 20,000 seconds, which as I discuss [POST=16974132]here[/POST], [POST=18236632]here[/POST], and [POST=16377891]here[/POST], would result in propellant to payload mass fractions in the millions or billions. A propellant/payload fraction in the more plausible thousands would require an I[SUB]sp[/SUB] in the 80,000 sec or greater range for which we have no conceivable non-science fiction technology to generate. And just for the record, the constant acceleration ships portrayed in The Expanse, able to flit from planet to planet in a few days are nearly as much science fiction as Star Trek. In the real world, high power means large amounts of waste heat, and constant thrust results in expending propellant at a rapid pace.
[Emphasis added]
Yes, precisely. You are assuming that the behavior of an intelligent alien civilization based upon the growth patterns of bacteria or other simple Earth organisms, which by the way often don’t expand in exponential fashion either. An alien civilization may well deliberately limit growth (just as industrial human societies have) and focus on quality of life, advancing knowledge and literacy, and development of novel technologies over population growth and resource utilization for their own sake. And as previously discussed, we could be surrounded by an alien civilization beaming messages through our solar system and never recognize them because of our own primitive limitations in measurement and observation limits us to the electromagnetic spectrum. To date we’ve catalogued about 84 million stars out of an estimated 400 billion stars, or about 0.02% of stars in the galaxy, and of those most we have only spectral data; we’ve only found about 2,700 that have one or more planets even though current theories of star system formation favor the development of planets around the majority of stars. So, really, we know about as much about our galaxy and the probability of advanced life of it as a hermit living in the Adirondacks knows about the boroughs of Manhattan. We really can’t make any credible inferences from what we’ve seen because we’ve seen virtually nothing.
Nope. You’re missing the essential nuance that is precisely the point of my argument. Are flying cars technologically possible, in the sense of whether someone can build something that resembles such a thing? Sure. There are arguably a bunch of them around, and the earlier ones go back to at least the 1940s. But would anyone want to build them for a mass market? Of course not. We’re obsessed with cost, fuel efficiency, safety, long-term reliability, and other practical stuff – the last thing we want is vehicles that have none of those things, and the last thing we need as a society that has too many morons smashing into each other on simple roadways is morons doing it much more dramatically and fatally in the skies. That’s why we don’t have flying cars. There may be technological solutions to those problems that enable them in the distant future, but if so, they will be enabled by technologies that were never even remotely imagined by the prognosticators of the earlier part of the 20th century.
Passenger rockets? Many thought we’d have passenger trips to the moon and even the planets by now after we successfully sent men to the moon. And we could have, if we’d put our minds and dollars to it. The movie 2001: A Space Odyssey posited that by 2001 we’d have passenger spacecraft going to the moon operated by Pan Am. How did that work out, both for passenger spacecraft and for Pan Am? So much for predictions. The question became, why bother? What could possibly justify such an enormous dedication of treasure and social capital? So we didn’t do it, and dealt with more important things. Again, exactly my point.
Ah, so our predictive ability in the short term totally sucks, but if you make the timescale long enough, all our predictions will be correct?
Presumably he was talking about high ISP nuclear electric. Here’s 20 times performance right here : Dual-Stage 4-Grid - Wikipedia
I hate to be mean, but did you miss the memo from the European Space Agency, or are you being pedantic and saying an ISP of 21,400, or roughly 60 times the ISP of standard hydrazine thrusters, doesn’t improve propulsive performance by “a factor of 20”. Or are you saying that even though it works fine in the lab, it’s not ready for launch without years of refinements, and thus the technology is not “existing”?
Didn’t the Voyager probes use hydrazine and some clever maneuvers to gather momentum from the gravity of the planets they flew by?
Also, you didn’t address antimatter. If you can efficiently make antimatter - and since you can create very high electric fields to cause spontaneous pair production using particle beams and lasers pumped via superconducting magnets, that seems to indicate that very high efficiency is feasible. Obviously as a limiting case, for an antimatter production plant in deep space where the background keeps high temperature superconducting magnets cold, you could approach 50% efficiency in theory. And you don’t need anywhere near that - the sun pumps out so much energy for free, and you can gather it with very thin photovoltaic panels in space, that efficiency doesn’t need to be more than 0.1% or so to be totally practical for starship fueling.
If you can make antimatter efficiently, you fuse to anti-iron, since magnets interact with it strongly. Use laser tweezers and laser cooling and a series of isolated “plants” that do each stage in solar orbit. Fusion need not be net energy positive, so you can burn the energy to get pressures and temperatures (at the focus of the fusor) many orders of magnitude above the peak pressure/temperature in a star so that first 4-hydrogen fusion step is fast enough to be usable.
If you have anti-iron by the ton, well, just funnel the pions it makes when it annihilates out the back and off you go…
Exactly. You’re missing my point. Von Neuman starships need only be created once. The civilization that created them could then naval gaze for the next billion years or go extinct, it doesn’t matter.
The advantage of flying cars was that it saves time otherwise wasted in traffic. But it costs expensive flight training (or would require automation software we don’t have reliable enough even today), it costs impractical amounts of jet fuel, it costs very expensive finely made engines that wear rapidly under the stress of VTOL flight, and it costs all the people who would die in crashes.
As it turns out, this is only worth it for billionaires. For everyone else, it’s cheaper to waste time in traffic.
Von Neuman starships have their own inherent payoff. They exist because they re-create themselves forever.
It doesn’t really help your argument to keep parroting my “missing the point” response and then throwing in increasingly outlandish and improbable fantasies. Sure, (almost) anything is possible, but that’s not a helpful observation. Most outlandish fantasies are, kind of by definition, extremely improbable. In life, as in science (as I said way upthread) the simplest explanations tend to be favored and to prevail, and elaborately contrived ones tend to be improbable in fairly direct proportion to the elaborateness of their contrivance.
To be clear, I have no doubt that there is much to be gained from creating increasingly robust and redundant robotics that is ultimately self-maintaining. I have great doubts that we can follow along any sort of logical pathway to extrapolate that relatively modest and practical objective to the kinds of motivations you impute to a highly advanced intelligence, motivations in effect to take over the galaxy with exponentially replicating automata. That’s just ridiculous pure fantasy.
The problem with this, and basically all the other answers proposed in this thread (‘space is big’, ‘speed of light’, ‘it’s too costly’, ‘they don’t bother’, etc.), is that they really don’t offer any explanation—effectively, they’re just re-stating the question. The Fermi paradox is that given what we know, or believe, about life, technology, and the universe, we should expect our galaxy to be teeming with life. We don’t, so obviously, some of what we believe must be false—but then, saying ‘maybe it’s x’ doesn’t really do any work: yes, maybe it indeed is x, but that doesn’t make the mystery go away, as it doesn’t tell us what is wrong in our present understanding (or beliefs).
Basically, we have an argument of the form ‘x, y, and z imply a’, where a is the presence of life throughout the galaxy; since a appears to be false, we immediately know that one of x, y, or z must be false—so certainly, if x is false, then a doesn’t follow; but that doesn’t tell us anything new that we didn’t already know from merely observing that a is apparently false.
So when you’re saying that life is astonishingly rare, one immediately is forced to ask: but why? What is it that makes life so rare? While it’s true that we have no complete theory of the origin of life, so far, all of the conditions that appear necessary for it seem to be much more wide-spread than even our optimistic guesses; so what’s the bottleneck that accounts for life not being similarly widespread?
Again here’s the issue. If they need only be created once, and they are a reasonable extrapolation from our current technological understanding then they should be ubiquitous given even the smallest slice of galactic time (10My is 4% of a Galactic year).
But they aren’t.
So either
they’ve never been created
they can not be created
they can not propagate across galactic distances in reasonable amounts of time or
their creators have not yet created them
So we’re back a step to the intelligent agents that create self replicating factories and immortal fixated personalities for themselves. However, according to you, the path is obvious and just an engineering problem so whatever has prevented other species from building these engines of creation is either behind or in front of us.
Life seems like it can be common and high levels of sentience appears present in a number of animals. Sapience and the technological mastery seem the first filter you need to squeeze through. The next seems to be sufficient moral evolution to manage the acquisition of ever increasing sources of energy. Throwing stones at each other has a small knock effect; turning an open cycle fusion rocket into your personal creme brulee torch to get that special crust…more so.
Pretty surprising that a discussion of Fermi’s Paradox has gone on for this long without mentioning Cixin Liu’s Dark Forest theory.
Apropos of nothing, there’s a deep schism in SETI between the ‘listeners’ and the ‘broadcasters’ (METI / Active SETI). I’m firmly in the ‘stay completely quiet in the jungle until you understand the ecosystem’ camp.
If we were having this debate in 1850, and I am insisting that an internal combustion engine is just an engineering problem, would you agree that
a. You should know in 1850 that an internal combustion engine is possible if you are familiar with the thermodynamics of combustion and reasonable extrapolation as to what you can machine out of steel.
b. You could safely make the argument that it’s so far off that you will never see an internal combustion engine in your lifetime. (it took until 1890 for a useful one, and I’d argue that really high power ones weren’t available until the 1940s). Furthermore, you could cast doubt that the really high power ones are even possible. (I’m talking about the turbocharged, methanol injected ones that produced over a thousand horses and fit in a fighter)
So here’s the key elements that I feel differentiate a von neuman starship from “fantasy” vs engineering problem.
Self replicating molecular nanotechnology already exists. Bacteria already do it. Each bacterium needs a few simple ingredients in water and it can copy itself. (oxygen, light, CO2, water, and trace metals is all it takes)
Von neumann machines already de facto exist. There is no task a human hand can do you cannot build a robotic waldo to perform instead. We already have dry factories, spread across the world, that self replicate. Every piece of machinery in those factories is made of parts, and those parts were all made in some other factory. Full automation is now possible, it is simply a function of cost that humans still work in them.
Chemistry can occur in a vacuum, you don’t need liquid water to to make vacuum chemistry occur at high speeds, but it requires an alternate form of catalyst. Drexlerian nanotechnology calls for physical nanoscale fixtures that force only the chemical reactions you want to go forward. This means that eventually - even if it does take a thousand years to get there - you can do what #1 and #2 do, except you wouldn’t need a factory the size of Shenzhen to do it. You could build a factory that can duplicate itself that fits in a household refrigerator or smaller.
The human brain is a machine made of matter. Even if it uses “one weird trick” of physics we don’t yet understand, that trick can be duplicated. By trick, it turns out you can make chips that exploit physics to perform computation, such as D-wave’s thermodynamic minimizers or so far theoretical quantum computers. The human brain might use a trick that can’t be efficiently duplicated with a straight Turing machine, but even if it does, you can build a computer chip that does it.
So we’re 3/4 of the way to a starship, and I’ve stuck to things that already exist or you cannot argue won’t work!
Now, well, antimatter annihilation makes gamma rays and charged particles. If you could make a large quantity of antimatter, and then contain it somehow (I talk about fusing to a heavier element but that’s not the only way), you simply need to collide the oppositely charged particles inside an engine bell and have magnetic fields that send the charged particles in a direction that will give you thrust. That’s it. ISP is going to be 20 to 30 percent of the speed of light.
We’ve already produced antimatter before, just the best method so far is stupidly inefficient. No way to get a large quantity. I’ve read Drexler’s books and lots of things on machine intelligence and the human brain, so I feel completely certain about all the other assumptions, but not this one. I don’t know how feasible large scale production of antimatter is. I’ve read that there’s some method to boil the vacuum with lasers, and the lasers can be 90% efficient or better free electron lasers, but I can’t tell you how efficient the net reaction would be.
And there’s the problem that once the starship is at 10 or 20 percent of the speed of light, any collision that punctures the fuel tank probably means destruction of the vessel. I don’t know how feasible it is to stop this. (you would obviously have an armored prow on the ship made of the strongest material feasible and it would need to be a kilometer or more of various barriers to deflect or break up a tiny rock you hit - but I don’t know if that’s likely to save you or not)
I will kindly ask you to stop misquoting me. You took my first three sentences and then tacked on the last sentence from my last paragraph without indicating any intervening break. “That’s just ridiculous pure fantasy” refers specifically to your hypothesis of galactic colonialization by swarming automata, a fact which is completely absent from the way you lifted that remark totally out of its context.
I won’t even bother responding to the rest of it. Same old thing – endless strings of concatenated hypotheses. Apparently you enjoy sci-fi. Look, if my grandmother had wheels, she’d be a streetcar, and I would point out that both grandmothers and wheels are things that actually exist today!
That hypothesis is supported by the above, strongly so. If you aren’t educated enough to respond, that’s fine, but don’t call something fantasy you are ignorant about. What you call “endless strings” I call “a single assumption not strongly supported by existence proofs today”. (cheap production of antimatter). Everything else exists or exists in a form that is directly correlated to the form it needs to be, to the point that an educated person would say “well, I concede that since we have A, B is possible”. This would be like “we have a streetcar, but it runs on 2 rails, therefore we can make a 3 railed streetcar”.
SamuelA; you seem very attached to the concept of antimatter rockets. Even if you could obtain a large enough supply of antimatter to propel the craft to another star, what would be the best strategy to deal with the intense gamma rays produced by such a reaction? It’s not much use sending a self-replicating factory to Alpha Centauri if it has been cooked by radiation before it gets there.
Well, like I mentioned above, you’re not going to be sending human beings this way. You have some type of computational system, probably just digital computers, and these computers emulate some equivalent to human intelligence or better. Most importantly, these intelligence emulations have a digital state file that saves the “personality” of the system. That state file is redundantly distributed across N, where N is on the order of dozens, of separate physical modules in the ship. So as gamma rays damage the computers, data isn’t lost because there are enough copies that error correction can restore the original state (and housekeeping software would be continually doing this). As computer modules fail completely from excessive damage, a robot removes the failed module, takes it to a recycler, and probably converts it to plasma followed by a long series of manufacturing steps to re-create a brand new module. The data gets shifted back over, just a fancier version of a modern day RAID array rebuild, and everything is back to where it was before.
This would be true for the entire starship as much as possible. This is how it would survive decades to centuries in transit - it’s a ship of Thebes. Every piece is constantly being rebuilt, especially the parts at the prow that are exposed to the constant bombardment by interstellar wind.
And that’s why radiation “cooking” it is an easily solved problem. So long as at no time are you completely out of redundancy - as long as every key component of the “factory” part of the ship has at least 1 surviving redundant module, so long as you retain enough surviving “crew” that you have access to every key skill, the ship can continue the mission.
No, your problem is that if you hit a pebble while going ~10% of the speed of light, the resulting explosion would probably be more than any feasible ship structure could withstand. In essence, it’s the abrupt nature of the impact that you can’t recover from.
My take on the Great filter is related to this presumed abundance of antimatter and self-replicating machines; I call it ‘Light-speed Paranoia’, or maybe ‘Light-Travel-Time Paranoia’ might be a closer description.
So you send self-replicating devices or colony ships off to nearby stars, each of which are capable of creating significant quantities of antimatter (or, if that technology proves to be unphysical, we can assume that these devices can propel mass at great speeds in some other way). Once they are light-years away, they are isolated from any oversight or control you once had over them. If they decide to replicate kinetic weapons or antimatter bombs to use against you, you will never know - because of the light-travel time these things are happening beyond your C-horizon. So you build relativistic bombs and rockets (just in case).
Given enough paranoia it wouldn’t be long before one system uses all this self-replicating rocketry to wipe out the other - the more energy your ships use, the better they work as weapons. And paranoia is something that everyone in the universe experiences, according to Douglas Adams. The result is- no galactic empire can persist in the face of uncertainty.
Ah but you misunderstand SamuelA ingenious solution to that. His immortal digital species is also impervious to evolutionary change.
I’m still waiting to see evidence of these inevitable, technologically feasible entities that have had billions of years to swarm across our galaxy. Perhaps, like Stranger implied, they’ve all been eaten by dogs.
