Stephen Hawking: Why Isn't the Milky Way Crawling with Life?

[The Duchess of Zeon]

And it might be only one or two civilizations that do it. Even on Earth in most cultures reclusive hermit kingdoms and extreme lack of interest in exploration are the norm.... The Age of Exploration and the Ming Dynasty were aberrations. The unusual thing about humanity is not that we are intelligent but that we are industrialized. The Romans for example produced examples of steam engines and developed highly sophisticated knowledge of the universe... And kept using slave labour for nearly everything, because there was no motivational pressure to rely on for industrialization. The development of industrial civilization was a unique combination of the geological conditions of the British isles, the cultural conditions of western Europe generally, and the historical circumstances of the Black Death wiping out a large fraction of the population, happening at just the right time to put the necessary technology in the hands of people afterwards that they began to exploit it to begin a process of industrialization.

What we are probably going to find when we venture to explore other planets is a hell of a lot of Qing Chinas--vast centralized Empires that have lasted for ten thousand years in which life proceeds through exploitation of the local ecosystem through physical labour, whatever that ecosystem and whatever their exact structure may be, a common theme we'll find repeated in ten thousand variations.

Even sapient life, where it exists, is quite simply almost certainly not very sophisticated. Our random luck of the draw was in finding a section of the globe laden with coal and steel and other such resources, to find itself with a severe labour shortage at a time when it had the tools to remedy that labour shortage mechanically, and the inclination culturally to do so... Remove any one of those single components and it never happens.

I find this a remarkable notion. Would you object if I use it as the premise for original fiction? It seems to have immense story potential.

You may certainly go right ahead.

[B5B7]

Some excellent objections have been raised to the VNM concept. I read a short stoy a long time ago in which an ancient species realized that other species might create VNMs, that would be basically a plague, and so they acted to counter this by sending out their own machines designed to kill VNMs when the VNMs arrived at stellar systems.

[Adrian Laguna]

The development of industrial civilization was a unique combination of the geological conditions of the British isles, the cultural conditions of western Europe generally, and the historical circumstances of the Black Death wiping out a large fraction of the population, happening at just the right time to put the necessary technology in the hands of people afterwards that they began to exploit it to begin a process of industrialization.

I do not think that the industrial revolution depended on the geological conditions of the British Isles. Certainly the Brits got there first, but if for some reason the islands had stayed backward or collapsed into bickering petty kingdoms there would have been an industrial revolution regardless. The groundwork already existed in France, Spain, the Low Countries, and the Germanic States. Also North America if the British collapsed or stagnated after the place was colonized by them, or the French had been more serious about colonizing.

I would also be inclined to think that the Chinese not becoming industrialized on their own was more bad luck than the normal course of things. The problem I'd say was that they got invaded by Mongols. The earlier Mongols were actually not bad at a all, but the later ones turned out to be... less than adequate. Then the next dynasty took an an attitude of trying to restore the good old days from before the hordes had came from the North, which combined with other factors led to a rather poisonous atmosphere for progress. Certainly the Ming financed the expeditions of Zheng He, and accomplished numerous feats of technological prowess, but I think that was just inertia from the earlier, more vigorous Song dynasty.

Also the Japanese were right on the edge of an industrial revolution in the 19th century, all they needed was impetus and direction. Geopolitical conditions more akin to those of Europe may have given them both. Plague is not the only way to create a labour shortage, if the Japanese found themselves heavily outnumbered they may have turned to industry as a way to do more with less and make-up the difference.

Basically, while the conditions in Europe were unique, they weren't so unique so as to suggest to me that industrialization throughout the Galaxy would be an extreme rarity. Not the norm perhaps, but I doubt that if we run into tens of thousands of other species only two or three of them would be industrialized.

The Romans for example produced examples of steam engines and developed highly sophisticated knowledge of the universe... And kept using slave labour for nearly everything, because there was no motivational pressure to rely on for industrialization.

Not entirely true that the Romans produced steam engines. What they produced were toys more than anything, they couldn't do much in the way of useful work. I'm not sure if their metallurgy was advanced enough to produce steam engines as we think of them.

[ThomasP]

What are the odds that our current biosphere could itself the product of a self-replicating colonization project?

Meaning from the standpoint of plausibility, not necessarily "this really happened", of course. It could be an interesting spin if the aliens have indeed been here, done that, and moved on, with us at the end result.

[Serafina]

What are the odds that our current biosphere could itself the product of a self-replicating colonization project?

Meaning from the standpoint of plausibility, not necessarily "this really happened", of course. It could be an interesting spin if the aliens have indeed been here, done that, and moved on, with us at the end result.

I would say they are pretty low.

Furthermore, there is really no need to assume this. If they did it, they only introduced very, very basic lifeforms to our planet - because everything else evolved (we already see distinctive evolution patterns during the cambric explosion).

Given that there is no apparent use for them to do so, i deem it quite unlikely - building an starship that can search out an suitable planet, carry life for thousand of years and land safely on a planet is not an easy task
.
Overall, assuming that aliens brought the life to our planet is a redundat term according to Occams Razor:
If life did not start out here, but was brought here, it had to start somewhere else - AND we need advanced aliens, willing to bring it here.

Besides, the idea is hardly new.

[ThomasP]

Furthermore, there is really no need to assume this. If they did it, they only introduced very, very basic lifeforms to our planet - because everything else evolved (we already see distinctive evolution patterns during the cambric explosion).

Given that there is no apparent use for them to do so, i deem it quite unlikely - building an starship that can search out an suitable planet, carry life for thousand of years and land safely on a planet is not an easy task

I was throwing out the idea on the assumption that the life itself need not be carried aboard your probe/ship. Perhaps the probes could put together your DNA and basic cell structure from the materials already present, as part of their own self-replication process.

As to why, well - we can ask that about any of the scenarios, can't we? I'm going by the running assumption that *somebody* will want to explore and colonize. Carrying the seeds of a biosphere would be one feasible way of doing that, albeit indirectly.

Besides, the idea is hardly new.

Oh, certainly. The book version of 2001 had a similar scenario, though I don't think the Monoliths actually created life, as opposed to just tinkering with it. Fortunately I wasn't hoping the idea required originality

I'm just thinking in terms of a "what if" situation. There are most definitely holes in the idea.

[Serafina]

Furthermore, there is really no need to assume this. If they did it, they only introduced very, very basic lifeforms to our planet - because everything else evolved (we already see distinctive evolution patterns during the cambric explosion).

Given that there is no apparent use for them to do so, i deem it quite unlikely - building an starship that can search out an suitable planet, carry life for thousand of years and land safely on a planet is not an easy task

I was throwing out the idea on the assumption that the life itself need not be carried aboard your probe/ship. Perhaps the probes could put together your DNA and basic cell structure from the materials already present, as part of their own self-replication process.

As to why, well - we can ask that about any of the scenarios, can't we? I'm going by the running assumption that *somebody* will want to explore and colonize. Carrying the seeds of a biosphere would be one feasible way of doing that, albeit indirectly.

Well, assembling it at the planet is a nice idea - but that requires an even MORE complicated probe.

And i can still see no possible benefit from doing so.
There is no sense in preparing a planet for colonization, unless you can send colonists there - which no one did, obviously.
And trying to recreate your own species is just plain impossible unless you manipulate the whole evolutionary process - and we would see proof of that.

Exploration is equally difficult. You either need to return the information via another probe - which is quite complicated, because you need to exactly hit your solar system. Radio waves are going to be badly scrambled over long distances, and lasers need incredibly good aiming.
All of this for information about star systems you have no chance of visiting ever?

[Wyrm]

I meant a probe that goes to a system a stays there.

Point (a) is doubtful. Believe it or not, we have experience with von Neumann machines, and generalists tend to not be very aggressive. That is, a machine that is prolific enough to colonize a planet quickly enough to branch out in a thousand years, say, would be so overspecialized that it is unlikely to find a suitable planet to be able to replicate this quickly.

Why use planets? Won't most systems have enough asteroids?

What makes you think an asteroid is a suitable environment for self-replicating machines? The advantage of a planet is that you can have a crust (for mining raw material), water (the universal solvent for chemical reactions), and an atmosphere (for dispersing waste products) all in the same place.

Heck, even if Von Neumans don't work so well, you can just make normal probes and send them out dispersed to their own region to broadcast to nearby stars. The system would fall apart alot quicker though.

Then you can't take advantage of the exponential growth rate that VNMs afford, and you can't reach every system in a few million years. The home system has to supply all the material and energy.

Point (b) is also substantial. It'll take hundreds of thousands of years for the Voyager spacecraft to reach the nearest stars, and that took a favorable conjunction of planets.

Voyager had to be lauched out of a gravity well. If you start already outside and are willing to be big, you can go alot faster.

And where are you going to get the rocket fuel to propell the probe? The most useful volitiles for space travel exist at the bottom of gravity wells.

Except that's not what a VNM/FSTL strategy is designed to do. That strategy is a colonization strategy. It's designed to convert the resources on the planet the VNMs arrive at into more VNMs to launch towards other star systems. Any preexisting life would be destroyed and erased. This strategy is wholly unsuitable for figuring out what's out there.

Sorry for using the same acronyms. What I mean is a plan where you have a network of probes that go to a system, set themselves up broadcasting and produce more drones to go onto the next system. If they reach one that already has a drone they change course until all stars in this galaxy are reached, at which point they go outward.

Again, this strategy assumes that the probes can self-replicate. This requires complex chemical synthesis and refining, requiring some sort of solvent (water), and plentiful energy.

[PeZook]

I do not think that the industrial revolution depended on the geological conditions of the British Isles. Certainly the Brits got there first, but if for some reason the islands had stayed backward or collapsed into bickering petty kingdoms there would have been an industrial revolution regardless. The groundwork already existed in France, Spain, the Low Countries, and the Germanic States. Also North America if the British collapsed or stagnated after the place was colonized by them, or the French had been more serious about colonizing.

I think that's kind of the point: several factors, occuring at just the right time, are necessary for industrialization to occur. A stable government, relatively small land area, difficulty of external conquest, maritime tradition, attituted towards science and invention and large reserves of coal and iron all had to combine at the right time to spark the revolution. That Britain wasn't necessary for it is irrelevant.

Industrialization is by no means a given. I mean, look at the American Indians: they migrated to the Americas at least 11 000 years ago and only barely reached ancient technology levels (except without the metalworking, whoops!) when the Spaniards invaded and fucked everything up. I mean, the Maya had a civilization at the same time when Babylon was rising, and yet developed none of the advanced technology at the disposal of Europeans who came over and wiped them out. Hell, they didn't even figure out ironworking, still using sticks and stones to do their fighting.

North American indians are even worse, despite living in their areas far longer than the Mayas.

It's entirely possible most cultures remain hunter-gatherers. Or we may just be the first to actually leave our planet - as it was aptly put, somebody has to be

[Starglider]

The development of industrial civilization was a unique combination of the geological conditions of the British isles, the cultural conditions of western Europe generally, and the historical circumstances of the Black Death wiping out a large fraction of the population, happening at just the right time to put the necessary technology in the hands of people afterwards that they began to exploit it to begin a process of industrialization.

This is simply incorrect. The circumstances of the UK industrial revolution were somewhat unusual, but firstly that just meant it occurred in the UK first, and secondly humans still went from agriculture to industrialisation in a few thousand years. That's an eyeblink in evolutionary or geological time. Widescale deployment of technology such as powered looms occured within a century of their invention, and most of the key supporting discoveries and innovations did not occur in 18th century England. The English head start in industrialisation was in fact a similar phenomenon to the (formidable) lead silicon valley had in IT through the 60s and 70s. In any case if it had taken another century, another millenium or even another 10,000 years it would make no real difference. Pre-industrial civilisations cannot effectively control and enforce stasis on the entire planet, and without being able to do that the appropriate circumstances will eventually arise somewhere.

What we are probably going to find when we venture to explore other planets is a hell of a lot of Qing Chinas--vast centralized Empires that have lasted for ten thousand years

Human psychology isn't compatible with that; we had a few large empires (over 10% of the species), but they were relatively fragile and most humans that have lived did not live in one of the big empires. I can't see any reason to think that alien psychology, on average, is any more supportive of giant empires than ours is. However it is possible that there is a continuum between instinctive individualists and instinctive hierarchists, and that only species within a narrow range in the middle can innovate quickly while still forming cohesive enough societies to support high technology. Even there, I doubt it, because the average rate of advancement could be 100 times slower than humanity's historical progress and it would barely put a dent in the Fermi paradox. You'd have to have an incredible level of social stasis to somehow avoid developing industrial technology (despite having the theoretical intelligence to do so) - over those timescales climate change and ongoing evolution of the species itself will make things unstable even if they somehow avoid war, plague, rebellions and all the other things that made human history exciting.

Planets bearing life similar to our own aren't likely to lack usable metals - and underwater species aren't likely to be tool users in the first place. Lack of fossil fuels could be a problem though. Having to fuel everything with wood would have been a major drag on historical industrialisation, due to the higher labor costs of acquiring the fuel. There's still wind and water power though, and motors and generators would have been developed even without coal, so I don't think even this is fatal to progress, even if it would slow progress down by an order of magnitude or two.

Our random luck of the draw was in finding a section of the globe laden with coal and steel and other such resources, to find itself with a severe labour shortage at a time when it had the tools to remedy that labour shortage mechanically, and the inclination culturally to do so... Remove any one of those single components and it never happens.

As I said, if that occurred a mere hundred years or two after the basic technology becoming available (in the renaissance period), it was not particularly lucky. If you waited long enough, and humanity wasn't made extinct by something, it would be almost an inevitability. And no, the Romans could not have industrialised; their steam engines were toys that could do no real work, and they did not have the metallurgy to support significant mechanisation. The vastly superior metals (and just as importantly, metalworking still) available in the 18th century were the product of a European arms race several centuries, first of swords and armor, later of cannon.

[Solauren]

You know, I can think of a damn good reason as to why we haven't had contact with sentient aliens if they exist.

We are economically not worth it.

Consider #1:
If someone wants our planet's resources, they'd have to take the planet from us by force. Then they'd have to clean up the mess we've left it, and from however they took it from us. (See Independence Day).
If there are lots of planets, or other sources of resources out in the galaxy, why bother with attacking an inhabited planet? That' just another expense and hassal to consider.

It's cheaper to go to an uninhabited planet to harvest then it is to deal with an inhabited planet.

Consider #2:
Okay, the aliens don't want to conquer us. They want to talk or trade with us. Really, what do we have to offer a civilization capable of Inter-stellar travel? (STL or some form of FTL our knowledge of the universe can't predict yet, doesn't matter).

Resources? Avialable elsewhere without the trade and political bullshit.

Technology? The odds are an inter-stellar civilization has superior technology.

Biological samples for study? Do the 'UFO' routine and take DNA samples for cloning. (Note: No, I don't think that's going on)

Manufacture products unique to our civilizations? Just hack into our communication networks via remote and download them from the internet and make them yourself.

Really, we have nothing to offer another planetary civilization right now. We're not worth contacting.


Now, why don't we see signs of alien civilizations when we are looking into the universe? Probably because we haven't looked in the right place yet. The galaxy is a big place (let alone the observable universe). We're not looking for a needle in a haystack. We're looking for a marble dropped ino the pacific ocean.

It could take a while.

[Starglider]

Point (a) is doubtful. Believe it or not, we have experience with von Neumann machines, and generalists tend to not be very aggressive.

What experience would that be? Hint; bacteria are not von Neumann machines, I know it's sometimes cute to call lifeforms 'organic machines' when beating on anti-AI idiots, but the fact is that machines are intelligently designed and lifeforms are blindly evolved.

That is, a machine that is prolific enough to colonize a planet quickly enough to branch out in a thousand years, say, would be so overspecialized that it is unlikely to find a suitable planet to be able to replicate this quickly.

You appear to be imagining a single, static design of machine that must reproduce itself exactly. I know this is how thought experiments usually go but it is not realistic. Even a simplistic von Neumann design would realistically carry a library of blueprints, and it would build machines appropriate to the local environment. As the size of the local infrastructure base grows, there will be more and more specialisation, just like a normal industrial society. In practice a society advanced enough to build von Neumann machines will almost certainly be able to equip them with a decent level of AI, in which case it can and will design and fabricate equipment and 'offspring' specifically tailored to each situation it encounters. Given such flexibility I see no reason why there would be a inverse correlation between environmental specificity and reproduction rate. In fact I would expect a positive correlation, because a more advanced technology base improves both. Truly general AI will advance that technology base on its own, but that's Singularity territory.

Point (b) is also substantial. It'll take hundreds of thousands of years for the Voyager spacecraft to reach the nearest stars, and that took a favorable conjunction of planets.

Not really relevant because the Voyager spacecraft was not intended to be an interstellar mission. They were launched on relatively small boosters on trajectories optimised to visit as many planets as possible. We could do much better (at least x10 velocity) just with conventional rockets if we explicitly launched an interplanetary probe, and much much better if we used nuclear propulsion (which has been technologically possible since the 1960s, and blocked only by bizarre human politics).

Getting to other star systems would be prohibitively slow for planet-launched spacecraft. To spread across the galaxy in a couple of million years requires spacecraft with delta-v of a couple of percent c. That's a lot of energy to impart to one spacecraft, and under any practical set of considerations requires an interplanetary infrastructure to realize.

There have been credible design studies for spacecraft in the 50,000 ton class capable of delivering a decent von Neumann probe with a cruise velocity of 6% of c, e.g. the Project Daedalus study (halving the top speed to allow for decceleration to relative rest). That was somewhat ambitious, but you could get nearly half of that just using a nuclear pulse drive based on late 50s technology (as detailed in the Project Orion design study). Both of these are quite within the capabilities of civilisations like ours, if the political structure made interstellar missions a priority - they would be trivial for a planet covered in a robotic civilisation built out of a von Neumann seed. Elaborate insterplanetary infrastructures are really only needed if you want to launch batches of antimatter-powered relativistic probes, or fire millions (or billions) of probes out of giant mass drivers.

Except that's not what a VNM/FSTL strategy is designed to do. That strategy is a colonization strategy. It's designed to convert the resources on the planet the VNMs arrive at into more VNMs to launch towards other star systems. Any preexisting life would be destroyed and erased. This strategy is wholly unsuitable for figuring out what's out there.

Again you appear to be using a horribly oversimplified design of VNM. Anything with enough AI to function as a reasonably general replicator can easily be programmed to scan for evidence of life and avoid colonising such planets. Appropriate behaviour in this situation would be to unfold a big antenna and radio or laser news back home, then possibly consuming some asteroids to build orbital sensor platforms and/or robotic lander probes.

Which gets to the reason why a race would not jump to using the VNM strategy: it's not really the parent species that will be colonizing the galaxy — it's the VNMs! What's the interest in that species to let loose these VNMs?

Pure exploration aside, the notion of having VNMs thaw out embyros, gestate and raise them to start an organic civilisation is a common and fairly practical one. Frankly even if you're sending live colonists (hibernating or otherwise) sending some VNMs first is a good idea to build some infrastructure for them, but then if you're at that technology level you may just be able to send uploads anyway. It's ok, once the infrastructure is built I'm sure some sentimental hobbyist uploads will start trying to set up an organic ecosystem for fun.

[Mayabird]

I've said all along that sapience being rare seemed like the most likely single explanation to me.

Personally I think it's a number of filters, rather than just one. I don't understand why people always think of it in terms of one Great Filter. The thing is, incomplete filters where in a heavily populated galaxy one civilization is bound to slip through are much more air-tight in a thinly populated galaxy where the species that get to that filter have already had to pass through numerous others. I.e.:

Most life never gets past the single-cell stage.
Virtually all of the complex ecologies that do exist never develop sapient species.
Most of the few sapient species that develop never achieve agriculture.
Most of the few sapient species that achieve agriculture never achieve advanced technological civilizations.
Most of the very few advanced technological civilizations that arise are relatively isolationist "hermit kingdoms" that don't explore much beyond their own solar system.
Most of the tiny, tiny handful of expansionist civilizations that are left over after that peter out before they can spread beyond a tiny fraction of the galaxy's disk.

This.

With one more "filter": the sheer scale of time and space in the universe. The universe is fucking huge and if there's no FTL, we'll only know about stuff when the light reaches us. There could be a galaxy where intelligent life turned the entire galactic core into some Dyson hyper-sphere thing, but if this galaxy was two billion light years away and the building of it went from 600-500 million years before now, we wouldn't have a clue even though it's a giant "PEOPLE HERE TOO" sign. There could be generation ships plying the Andromeda galaxy now, but we can't see them and they haven't been going long enough to show up in our neck of this galaxy. It is a very big universe, and H. sapiens sapiens has been around for maybe 150,000 years, with most of that spent as hunter-gatherers.

It's not a real filter so much as an added layer of difficulty for us.

I have a hunch, based on little hard data, that life itself could be very common in the universe. It may even be plentiful in our own solar system outside Earth, but it'll be entirely single-celled life, and most life in the universe will be single-celled or the equivalent. But that's more because life can get a foothold in all sorts of conditions but has a hard time getting complex on the likes of Europa or Titan and in the atmosphere of Venus or whatever.

[Serafina]

You know, I can think of a damn good reason as to why we haven't had contact with sentient aliens if they exist.

We are economically not worth it.

Consider #1:
If someone wants our planet's resources, they'd have to take the planet from us by force. Then they'd have to clean up the mess we've left it, and from however they took it from us. (See Independence Day).
If there are lots of planets, or other sources of resources out in the galaxy, why bother with attacking an inhabited planet? That' just another expense and hassal to consider.

It's cheaper to go to an uninhabited planet to harvest then it is to deal with an inhabited planet.

Mankind has not been around that long. Even if we consider that they "scanned for future intelligent life" somehow, that possibility was only apparent for a couple million years.
You still have to come up with an explanation why they did not settle earth a couple million years ago.
Otherwise, you are of course correct - there may be a shitload of planets to go around, especially if you only want resources (which you can mine from uninhabitable planets).

Personally, i really like to think that we are one of the first intelligent species around. After all, you need AT LEAST a second generation start + remains of a friggin big supernova OR a third-generation star for life - otherwise, you just do not have the necessary elements. Given the age of the universe, it may well be that we are one of the first intelligent species around.

[GrandMasterTerwynn]

Which gets to the reason why a race would not jump to using the VNM strategy: it's not really the parent species that will be colonizing the galaxy — it's the VNMs! What's the interest in that species to let loose these VNMs?

Pure exploration aside, the notion of having VNMs thaw out embyros, gestate and raise them to start an organic civilisation is a common and fairly practical one. Frankly even if you're sending live colonists (hibernating or otherwise) sending some VNMs first is a good idea to build some infrastructure for them, but then if you're at that technology level you may just be able to send uploads anyway. It's ok, once the infrastructure is built I'm sure some sentimental hobbyist uploads will start trying to set up an organic ecosystem for fun. :)

Yes. I figure if you've got the technology to build VNMs, you're probably at the point where you're ready to redefine what it means to be a sapient being to be an AI upload in a shiny, extremely long-lived VNM body. At which point, sending out VNMs becomes synonymous with colonization.

Personally, i really like to think that we are one of the first intelligent species around. After all, you need AT LEAST a second generation start + remains of a friggin big supernova OR a third-generation star for life - otherwise, you just do not have the necessary elements. Given the age of the universe, it may well be that we are one of the first intelligent species around.

The average age of habitable terrestrial planets in this galaxy is likely to be one or two billion years older than Earth. Probably long enough for more than a few examples of sapient life to have already evolved, passed through technological singularity, have gotten bored and decided to spend the rest of the lifespan of the universe running recursive ancestor sims, or triggering the formation of organic-life-friendly planetary systems and ecosystems for the lulz.

[Junghalli]

And where are you going to get the rocket fuel to propell the probe? The most useful volitiles for space travel exist at the bottom of gravity wells.

The negligeable gravity well object population of the solar system is hardly volatile-poor. Comets and KBOs are largely made up of ice.

With one more "filter": the sheer scale of time and space in the universe. The universe is fucking huge and if there's no FTL, we'll only know about stuff when the light reaches us. There could be a galaxy where intelligent life turned the entire galactic core into some Dyson hyper-sphere thing, but if this galaxy was two billion light years away and the building of it went from 600-500 million years before now, we wouldn't have a clue even though it's a giant "PEOPLE HERE TOO" sign. There could be generation ships plying the Andromeda galaxy now, but we can't see them and they haven't been going long enough to show up in our neck of this galaxy. It is a very big universe, and H. sapiens sapiens has been around for maybe 150,000 years, with most of that spent as hunter-gatherers.

Indeed. I touched on this, although in a somewhat different way, when I pointed out that we've only been watching for aliens for a pathetically tiny amount of time. The Earth could have been awash in alien radio signals in 1750 and we'd never know about it. An alien probe could have passed over Earth 5 million years ago and we'd never know. Somewhere in your bloodline there might be a cave-man who met an alien astronaut face to face tens of thousands of years ago and we'd never have a clue.

Radio waves are going to be badly scrambled over long distances, and lasers need incredibly good aiming.

You'd need fairly good aim to reach another star system anyway. Get your probe's course wrong and you end up having to expend a lot of energy correcting it, since even slight errors will cause a wide miss over the kind of distances we're talking about.

Personally, i really like to think that we are one of the first intelligent species around. After all, you need AT LEAST a second generation start + remains of a friggin big supernova OR a third-generation star for life - otherwise, you just do not have the necessary elements. Given the age of the universe, it may well be that we are one of the first intelligent species around.

According to this paper Earthlike worlds could have begun forming in our galaxy 9.3 billion years ago. Assuming intelligent life started to arise on those first-generation Earthlike worlds at roughly the same rate it arose on Earth the first intelligent species would have evolved around 5 billion years ago.

It's possible we're the first intelligent species in our galaxy or galaxy group or supercluster, but it would have to be because intelligent life in general is ridiculously rare.

[Simon_Jester]

Why bother? You can say "survival", but humanity right now isn't exactly rushing off to build space colonies even though it would be a really big help towards long-term species survival, much less place them in other solar systems far away from the central civilization and system.

Expanding on the "Qing China" point, it's possible that an alien civilization, particularly a highly centralized and integrated one, might decide that the costs of settling in other solar systems (namely, the long distances and communications, the eventual fracturing that would come due to those unless the species is really long-lived and patient) simply aren't worth the benefits unless they are in serious threat of species death. In the meantime, they'd have a nice, integrated civilization in their home system, one in which communication is only a slight hassle, and travel mildly problematic.

The same goes for a species that goes through the singularity and winds up living in virtual worlds. For an AI, leaving the network of AIs you live in means being so far out of touch that billions of billions of clock cycles pass before you can talk to anyone. That could be intensely unappealing, and therefore discourage colonization.

I think they'd probably discover the existence of an external universe eventually, assuming they developed advanced technology. If they're intelligent and technological they're probably going to be curious. They're going to wonder what makes up the roof of the world and what that hot thing in it is, and will turn scientific instruments on it. Sooner or later they're bound to turn something on it which will be able to see the sun and the stars.

Yes, but how much will they care? They know the sun and the stars are up there, but they're only detectable using advanced scientific instruments. Why would they be any more interested in colonizing space than you are in colonizing the ocean floor?

The fact that intelligent life knows a frontier exists does not mean they're interested enough to dedicate a large fraction of their gross planetary product to colonizing that frontier.

Why bother? You can say "survival", but humanity right now isn't exactly rushing off to build space colonies even though it would be a really big help towards long-term species survival, much less place them in other solar systems far away from the central civilization and system.

Excellent point, but the problem with the Fermi Paradox is it only takes one successful "crazy" species to fill up the galaxy. Sooner or later one is bound to emerge by sheer probability if technological civilizations are common.[/quote]Yes, but the probability of such a species having existed long enough ago to have done this cannot be estimated. There are too many fudge factors; the probability could be anything from "almost one," in which case the Fermi Paradox hits with full force, to "almost zero," in which case the Fermi Paradox is a moot point because we're the only species in the galaxy that would even consider doing that.

[Junghalli]

Yes, but how much will they care? They know the sun and the stars are up there, but they're only detectable using advanced scientific instruments. Why would they be any more interested in colonizing space than you are in colonizing the ocean floor?

It didn't say they'd necessarily be interested in colonizing it (a species with eyes might no be either - just look at how half-heartedly our own space programs are funded), I was simply saying that they'd know about it.

Yes, but the probability of such a species having existed long enough ago to have done this cannot be estimated. There are too many fudge factors; the probability could be anything from "almost one," in which case the Fermi Paradox hits with full force, to "almost zero," in which case the Fermi Paradox is a moot point because we're the only species in the galaxy that would even consider doing that.

Yes, but we can say that as a simple matter of statistics the more technological civilizations there are the less plausibility explanations like "nobody cares enough" have, because larger populations are more likely to have deviations from the norm and it only takes one deviant civilization to fill up the galaxy in very short timescales compared to its lifespan. This is why I favor a number of filters instead of a Great Filter. You don't need to worry about how every Earthlike world in the galaxy must produce a civilization apathetic to interstellar colonization; very few of such civilizations arise because other filters catch most of them before they can get that far, and there may be more filters ahead the catch the tiny handful that slip past this particular one.

[Wyrm]

Point (a) is doubtful. Believe it or not, we have experience with von Neumann machines, and generalists tend to not be very aggressive.

What experience would that be? Hint; bacteria are not von Neumann machines, I know it's sometimes cute to call lifeforms 'organic machines' when beating on anti-AI idiots, but the fact is that machines are intelligently designed and lifeforms are blindly evolved.

A 'von Neumann machine' has a specific definition, and organic life fits that definition like a glove. In fact, the way real organisms replicate themselves is a pretty good match to the way von Neumann machines replicate themselves. Hint: von Neumann's chief insight was that the blueprints are their own specification.

Even if you were correct, yours would be an irrelevant point, because organic life faces exactly the same problems dealing with their environment as VNMs would.

You appear to be imagining a single, static design of machine that must reproduce itself exactly.

I do not. A lifeform that is able to aggressively utilize a particular resource will not be able to survive on a different resource, as it is too optimized for that resource to effectively utilize another. A constructor that is optimized for using one resource would be ill-suited to using another. That's a basic engineering tradeoff.

I know this is how thought experiments usually go but it is not realistic.

I'm basing my reasoning on an exant model, while you're basing yours on fanciful, hypothetical machines with hyperbolic capabilities, and I'm not being realistic? Huh.

Even a simplistic von Neumann design would realistically carry a library of blueprints, and it would build machines appropriate to the local environment.

How many different blueprints will you need? How large is the universal constructor you need to carry? What's the resulting weight of this library and constructor? You have to carry both to be effective. Remember also that this library and constructor has to be fault-tollerant against many centuries of hard interstellar and cosmic radiation, as well as sheer time.

Also, you're imagining a universal constructor that could construct absolutely anything, when even in organic life, no such damn thing exists. We would only be able to construct such a thing because we use our tools on resources produced by our extensive infrastructure. The kind of machine you're fancying must be a mini-civilization onto itself, or a seed to a technologically advanced civiliation. The former case is a very, very Hard problem. In the latter case, you're enslaving a race of intelligent creatures to your own end.

As the size of the local infrastructure base grows, there will be more and more specialisation, just like a normal industrial society. In practice a society advanced enough to build von Neumann machines will almost certainly be able to equip them with a decent level of AI,

Why? A true self-replicator would have to be about the order of macromolecules to manipulate matter with enough precision to be a true self-replicator. You can't fit very much intelligence in even a million atoms.

We could do much better (at least x10 velocity) just with conventional rockets if we explicitly launched an interplanetary probe,

And where are you going to get the fuel and the oxidizer for the rockets? Also, 10x Voyager speed is not a substantial fraction of c. No fast exploration for you!

and much much better if we used nuclear propulsion (which has been technologically possible since the 1960s, and blocked only by bizarre human politics).

And where are you going to get, refine, and enrich the radioactives?

The reason we can mine so easily on this planet is because we have an active geology, where the heavier elements get churned up mechanically and separated chemically. Asteroids are significantly lacking in that geology.

There have been credible design studies for spacecraft in the 50,000 ton class capable of delivering a decent von Neumann probe with a cruise velocity of 6% of c,

Why is a 50 kiloton spacecraft sufficient to carry a decent von Neumann probe? You assume that a real von Neumann probe with a sufficiently adequate universal constructor can fit in the payload. You will justify this assumption now.

e.g. the Project Daedalus study (halving the top speed to allow for decceleration to relative rest). That was somewhat ambitious, but you could get nearly half of that just using a nuclear pulse drive based on late 50s technology (as detailed in the Project Orion design study). Both of these are quite within the capabilities of civilisations like ours, if the political structure made interstellar missions a priority - they would be trivial for a planet covered in a robotic civilisation built out of a von Neumann seed.

All of which require refined materials and fabricated parts — to wit, an exant civilization — to build. That means that there's only going to be one of these spacecraft no matter how many times your von Neumann machine replicates, unless it's able to refine materials and fabricate parts just like a civilization could. Furthermore, unless these machines can replicate the bombs/fuel pellets for the rocket, it's going to be good for only one trip. In order to take advantage of the VNMs' advantages, the spacecraft and its fuel must also be within the machines' manufacturing capabilities.

Except that's not what a VNM/FSTL strategy is designed to do. That strategy is a colonization strategy. It's designed to convert the resources on the planet the VNMs arrive at into more VNMs to launch towards other star systems. Any preexisting life would be destroyed and erased. This strategy is wholly unsuitable for figuring out what's out there.

Again you appear to be using a horribly oversimplified design of VNM.

Given that life is made of the most common elements in the universe, it's obvious that, for creating a VNM to be used in unpredictable environments like remote alien planets, the low-hanging fruit is an artificial life-form. That particular form of VNM is not known for its smarts. And I'm including humans here.

Anything with enough AI to function as a reasonably general replicator can easily be programmed to scan for evidence of life and avoid colonising such planets. Appropriate behaviour in this situation would be to unfold a big antenna and radio or laser news back home, then possibly consuming some asteroids to build orbital sensor platforms and/or robotic lander probes.

Again, you theorize a universal replicator with no limits on raw materials and end products. Justify its real existence.

Also, you're assuming that the AI can recognize life in any form. That to me suggests some form of imagination, given that 'life' itself is an extremely slippery concept — it's hard to find a definition that is general enough to include any potential life form we've never seen without including things that aren't life that we know about. To go beyond literal definitions is a reasonable standard for imagination, so we are employing an intelligent entity that has imagination to do our will.

If that thought doesn't give you pause, you're a total bastard.

Which gets to the reason why a race would not jump to using the VNM strategy: it's not really the parent species that will be colonizing the galaxy — it's the VNMs! What's the interest in that species to let loose these VNMs?

Pure exploration aside, the notion of having VNMs thaw out embyros, gestate and raise them to start an organic civilisation is a common and fairly practical one. Frankly even if you're sending live colonists (hibernating or otherwise) sending some VNMs first is a good idea to build some infrastructure for them, but then if you're at that technology level you may just be able to send uploads anyway. It's ok, once the infrastructure is built I'm sure some sentimental hobbyist uploads will start trying to set up an organic ecosystem for fun.

Again, you theorize the existence of an entity that can replicate itself, has intelligence, is smart and clever enough to construct the underpinnings of a technological civilization, and at the end must surrender itself, its children, and their combined labors to usurpers of dubious worth and authority. What's to prevent a mutant VNM from killing the embryoes and simply forming the Cluster, a civilization by robots, for robots, and will crush the puny fleshlings?

[Samuel]

Again, you theorize the existence of an entity that can replicate itself, has intelligence, is smart and clever enough to construct the underpinnings of a technological civilization, and at the end must surrender itself, its children, and their combined labors to usurpers of dubious worth and authority. What's to prevent a mutant VNM from killing the embryoes and simply forming the Cluster, a civilization by robots, for robots, and will crush the puny fleshlings?

Because it is programmed to do so. We aren't going for an AI- an idiot savant machine is good enough and it doesn't have to be much of a savant given that time is not a major constraint.

Why is a 50 kiloton spacecraft sufficient to carry a decent von Neumann probe? You assume that a real von Neumann probe with a sufficiently adequate universal constructor can fit in the payload. You will justify this assumption now.

You do realize we can use more than one, right? If it take 495 kilotons, we have the machine build ten such spacecraft and lauch them together.

[Wyrm]

Again, you theorize the existence of an entity that can replicate itself, has intelligence, is smart and clever enough to construct the underpinnings of a technological civilization, and at the end must surrender itself, its children, and their combined labors to usurpers of dubious worth and authority. What's to prevent a mutant VNM from killing the embryoes and simply forming the Cluster, a civilization by robots, for robots, and will crush the puny fleshlings?

Because it is programmed to do so. We aren't going for an AI- an idiot savant machine is good enough and it doesn't have to be much of a savant given that time is not a major constraint.

Starglider stated that it would be an AI, and he seems to think it's necessary for a true universal constructor. However, even if it was an 'idiot savant', it will act as programmed, but it will have to construct an advanced infrastructure and educate a crop of humans without adult intervention. These are both tasks that I would think requires genuine intelligence. When was the last time you let an idiot savant build a bridge or raise a child? The 'idiot' qualifier is there for a reason.

And who says time isn't a major constraint? Even on ice, suspended embryos will not last forever.

Why is a 50 kiloton spacecraft sufficient to carry a decent von Neumann probe? You assume that a real von Neumann probe with a sufficiently adequate universal constructor can fit in the payload. You will justify this assumption now.

You do realize we can use more than one, right? If it take 495 kilotons, we have the machine build ten such spacecraft and lauch them together.

So instead of just building one craft, the VNM now have to build two or more. Congrats! You've just multiplied every problem I stated above by that factor.

Also, Starglider has yet to prove a universal constructor is possible for any payload.

[Junghalli]

A lifeform that is able to aggressively utilize a particular resource will not be able to survive on a different resource, as it is too optimized for that resource to effectively utilize another. A constructor that is optimized for using one resource would be ill-suited to using another. That's a basic engineering tradeoff.

Would a self-replicating probe actually need to be adapted to such a wide variety of environments? It would most sensibly use asteroids and comets/KBOs as raw materials for its replication, and one solar system's Kuiper Belt or asteroid belt does not seem to me like it would be so radically different from another's. True, the probe might need equipment to exploit a variety of objects of very different compositions (equipment to extract the carbon and other useful materials from a dirty snowball vs. equipment for doing the same for a dry hot carbonaceous asteroid might be rather different), but aside from issues of temperature and radiation from proximity to the local star we're talking about fairly similar working environments (hard vacuum).

A self-replicating probe might also be programmed to skip replication in systems that did not contain resources it could readily exploit. Even if you only take equipment to work in an environment like our asteroid belt, say, a large number of solar systems will probably have similar asteroid belts. Replication would be slower, but you could still take advantage of exponential growth. Especially if you programmed your probe to replicate like crazy whenever it found a suitable solar system, instead of a simple one solar system surveyed one replication strategy.

And where are you going to get the fuel and the oxidizer for the rockets?

I don't see why this would be a big problem. Find a suitable small icy object (comet, KBO, icy moonlet), grab some water, crack it into hydrogen and oxygen with electrolyses, and you have your rocket fuel and oxidizer. Of course, chemical rockets are about the worst thing you could use for interstellar exploration, but it's not hard to envision lots of propulsion systems for which "wilderness refueling" on icy bodies would be practical.

The reason we can mine so easily on this planet is because we have an active geology, where the heavier elements get churned up mechanically and separated chemically. Asteroids are significantly lacking in that geology.

Actually asteroids would be much richer in metallic elements than planets precisely because they never had active geology. In a planet almost all the juicy heavy elements sink to the totally inaccessible core early in the planet's history. With asteroids the heavy elements remain evenly mixed in with the silicates and other chaff. Even C-type asteroids might be as much as 22% iron by mass, and you could probably scoop easily processed nickel-iron granules right out of the dirt. And then there's nickel-iron asteroids like 16 Psyche, which seems to be basically a 200 km flying mountain of metal.

http://www.tricitiesnet.com/donsastronomy/mining.html
http://www.permanent.com/a-mining.htm

Again, you theorize the existence of an entity that can replicate itself, has intelligence, is smart and clever enough to construct the underpinnings of a technological civilization, and at the end must surrender itself, its children, and their combined labors to usurpers of dubious worth and authority.

Since its creators program its goal system I don't see why this is a problem. The "robots will rebel" concept is based on the idea that robots will have tendencies similar to organic life (they will want to preserve themselves and their descendants, will value their own existence, will value their self-determination etc.), but there's absolutely no reason an intelligence designed from the ground-up by us would be like that. We have those traits because natural selection has selected for them; there's no reason for a designed intelligence to have them.

It is true that self-replication does open up the possibility of mutants and eventually the possibility of the laws of Darwin taking over. This is a legitimate concern with self-replicating machines.

I'd also point out Peter Watts's take on consciousness in Blindsight, which is that it may not be necessary for an intelligent mind. If that's true an "idiot savant" AI might be every bit as smart as a sapient one, it simply wouldn't be self-reflective. Of course, even a sapient AI would have no reason to object to its "slavery", assuming it's designed competently, since its goal system would be completely designed by us (not by natural selection, which would naturally create self-interested intelligences).

[Coyote]

What we are probably going to find when we venture to explore other planets is a hell of a lot of Qing Chinas--vast centralized Empires that have lasted for ten thousand years in which life proceeds through exploitation of the local ecosystem through physical labour, whatever that ecosystem and whatever their exact structure may be, a common theme we'll find repeated in ten thousand variations.

I find this a remarkable notion. Would you object if I use it as the premise for original fiction? It seems to have immense story potential.

You mean, Stargate SG-1?


Couldn't it be that life and technology has already arisen elsewhere, but because the images we get from stars now is thousands or even millions of year sold, we haven't "seen it yet"?

They may already be on their way....! ( )

[Stark]

Maybe by 'remarkable' he means 'remarkably stupid'. It's not just bad authors who follow the train of thought 'aliens not like people = aliens not like contemporary culture = aliens are like xyz ancient culture = aliens are contrived political soapboxes'.

[Junghalli]

Couldn't it be that life and technology has already arisen elsewhere, but because the images we get from stars now is thousands or even millions of year sold, we haven't "seen it yet"?

Could be, but it would still require that older first civilization to arise remarkably close to ours in time. Light only takes 100,000 years to cross our galaxy and even at .01 c the entire galaxy could be colonized within 10 million years, while the galaxy has been capable of supporting life for at least 9 billion years.

The coincidence is less if we assume technological civilizations are ridiculously rare, so the nearest ones are billions of light years away, but that of course would require other filters to explain why there are so few of them. Of course, we probably couldn't detect a civilization at that distance anyway unless they were enshrouding a significant fraction of the stars in their galaxy with Dyson Spheres. Interestingly, I remember reading a web article a while back where they found far-away galaxies that exhibit roughly the characteristics one would expect if that was what we were seeing (I can try and find it if you want). I err on the side of caution and assume it's natural phenomenon, but it's interesting to think about nonetheless.

The thought does, however, remind me of the Phase Transition Hypothesis, of which one example is described here.