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

[Natorgator]

From an article in The Daily Galaxy:

In his famous lecture on Life in the Universe, Stephen Hawking asks: "What are the chances that we will encounter some alien form of life, as we explore the galaxy?"

If the argument about the time scale for the appearance of life on Earth is correct, Hawking says "there ought to be many other stars, whose planets have life on them. Some of these stellar systems could have formed 5 billion years before the Earth. So why is the galaxy not crawling with self-designing mechanical or biological life forms?"

Why hasn't the Earth been visited, and even colonized? Hawking asks. "I discount suggestions that UFO's contain beings from outer space. I think any visits by aliens, would be much more obvious, and probably also, much more unpleasant."

Hawking continues: "What is the explanation of why we have not been visited? \One possibility is that the argument, about the appearance of life on Earth, is wrong. Maybe the probability of life spontaneously appearing is so low, that Earth is the only planet in the galaxy, or in the observable universe, in which it happened. Another possibility is that there was a reasonable probability of forming self reproducing systems, like cells, but that most of these forms of life did not evolve intelligence."

We are used to thinking of intelligent life, as an inevitable consequence of evolution, Hawking emphasized, but it is more likely that evolution is a random process, with intelligence as only one of a large number of possible outcomes.

Intelligence, Hawking believes contrary to our human-centric existece, may not have any long-term survival value. In comparison the microbial world, will live on, even if all other life on Earth is wiped out by our actions. Hawking's main insight is that intelligence was an unlikely development for life on Earth, from the chronology of evolution: "It took a very long time, two and a half billion years, to go from single cells to multi-cell beings, which are a necessary precursor to intelligence. This is a good fraction of the total time available, before the Sun blows up. So it would be consistent with the hypothesis, that the probability for life to develop intelligence, is low. In this case, we might expect to find many other life forms in the galaxy, but we are unlikely to find intelligent life."

Another possibility is that there is a reasonable probability for life to form, and to evolve to intelligent beings, but at some point in their technological development "the system becomes unstable, and the intelligent life destroys itself. This would be a very pessimistic conclusion. I very much hope it isn't true."

Hawkling prefers another possibility: that there are other forms of intelligent life out there, but that we have been overlooked. If we should pick up signals from alien civilizations, Hawking warns,"we should have be wary of answering back, until we have evolved" a bit further. Meeting a more advanced civilization, at our present stage,' Hawking says "might be a bit like the original inhabitants of America meeting Columbus. I don't think they were better off for it."

Interesting take on the Fermi Paradox.

[Samuel]

This isn't really new and still fails the basic problem. With a simple Von Neuman and STL you can cover the whole Milky Way Galaxy in a couple million years. So... why aren't they here yet?

[Simon_Jester]

This isn't really new and still fails the basic problem. With a simple Von Neuman and STL you can cover the whole Milky Way Galaxy in a couple million years. So... why aren't they here yet?

Also, this paper might be relevant. Unfortunately, I haven't had time enough to give the equations a thorough going over. Based on skimming-level knowledge, it's a paper that attempts to use mathematical modeling to talk about interstellar colonization and the spread of civilizations, with references to other such works.

One interesting point made is that such models suggest that at least some star systems will go uncolonized, and that at a certain point it may be more profitable to send colony expeditions than to try to build massive-scale constructions that we could detect over interstellar distances. In which case the Milky Way may very well be covered with von Neumann machines, and we got left out by chance or by intent. It's not clear that we would be able to tell.
______

Or maybe intelligence predictably evolves in some direction other than trying to colonize the galaxy space-opera style. Hawking suggests that it blows itself up. Another possibility is that it goes through some kind of technological singularity and winds up sitting on servers on the homeworld playing its equivalent of World of Warcraft version 438.

[Samuel]

That wasn't my point. You only need one civilization to do it and the marginal cost is so low for one built up as high as the ones that turn in on themselves with virtual reality, that you could have individuals sponsering their own probes to each system to say hi.

[The Duchess of Zeon]

That wasn't my point. You only need one civilization to do it and the marginal cost is so low for one built up as high as the ones that turn in on themselves with virtual reality, that you could have individuals sponsering their own probes to each system to say hi.

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.

[Darth Wong]

This isn't really new and still fails the basic problem. With a simple Von Neuman and STL you can cover the whole Milky Way Galaxy in a couple million years. So... why aren't they here yet?

Who says they would necessarily make the effort?

[Frank Hipper]

Why isn't it considered a conceit, speculating that aliens would share any of our motivations in the first place?

Giving them technology is only begging a million and one questions to boot.

[Serafina]

Well, there are some possible soltions to the Fermi Paradox:

-Life in general is extremely rare.
-Life above a certain complexity is extremely rare.
-Intelligence above a certain level is extremely rare.
-Usage of tools to fabricate other tools is extemely rare.
-Using automated production is extremely rare.
-Discovering the scientific method is extremely rare.
Start to see the pattern yet?

Also, it might be possible that
-there just is not enough motivation to travel space, due to it being extremely difficult
-Interstellar travel is just plain impossible, expect for probes
-other intelligent species evolve their technology and society at an extremely low pace

One (or some) of these explanations have to be true - because it is an obvious fact that we do not have encountered extraterrestrial (not to speak of extrasolar) life.

[Junghalli]

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.

[Samuel]

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....

Which is why the Europeans managed to crush them. You only need a few outliers for the whole system to get overturned.

This isn't really new and still fails the basic problem. With a simple Von Neuman and STL you can cover the whole Milky Way Galaxy in a couple million years. So... why aren't they here yet?

Who says they would necessarily make the effort?

You only need a few individuals who are willing to. For a high tech civilization, they are cheap so all that is needed is motivation. And the odds that at least a few members of such a culture are curious about alien life is pretty good.

-Usage of tools to fabricate other tools is extemely rare.

I doubt it. Animals use tools and it isn't a big leap to alter your tools using other tools to make them better.

-Using automated production is extremely rare.

Why? That only works if every society ends up static, unchanging and dedicated to the status quo. It doen't work if the societies have to compete with each other and are trying to get advantages to undermine each other.

-Discovering the scientific method is extremely rare.

There is nothing intrinsically unbelievable about the scientific method.

-there just is not enough motivation to travel space, due to it being extremely difficult

Correct. There isn't a really good reason to go to another star system.

-Interstellar travel is just plain impossible, expect for probes

... I have been talking about probes.

-other intelligent species evolve their technology and society at an extremely low pace

That sounds too much like "humans are special". I think it is more likely that societies get out of the ruts they are in very slowly- the hunter gather period was most of humanities existance on the planet after all.

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.

You only need one plastering probes everywhere to get a different situation from what we see.

[Junghalli]

Which is why the Europeans managed to crush them. You only need a few outliers for the whole system to get overturned.

If her scenario is true there is at least one outlier, ourselves. Perhaps we are the first. Somebody has to be.

You only need one plastering probes everywhere to get a different situation from what we see.

Which is why I said many of these filters work best in combination with other filters that keep the numbers manageable. If there have been millions and millions of intelligent species in the galaxy's history then it is difficult to believe none of them have ever had the ability and will to colonize the galaxy. If there have been only a few thousand then it becomes much more believable.

Also, alien probes may well have visited the solar system in the past and we'd never know. If one had come any time before the invention of writing there would have been no record of it. That's a tiny slice of the age of the Earth or even the age of the human species, and even if it was in historical times we might not recognize it for what it was (records of it would probably be dismissed as a comet or something). Of course, it couldn't have been a colonizing civilization or we would know about it (and probably not be here).

[Wyrm]

This isn't really new and still fails the basic problem. With a simple Von Neuman and STL you can cover the whole Milky Way Galaxy in a couple million years. So... why aren't they here yet?

This argument assumes two things not in evidence:

(a) Von Neumann machines exist that are both generalist and have a high reproduction rate, even given marginal resources, and

(b) fast STL delivery of these von Neumann machines is cheap and widely adaptable to any arbitrarily marginal material base.

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.

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. 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.

Who says they would necessarily make the effort?

You only need a few individuals who are willing to. For a high tech civilization, they are cheap so all that is needed is motivation. And the odds that at least a few members of such a culture are curious about alien life is pretty good.

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.

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?

[Samuel]

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? 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.

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.

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.

[Junghalli]

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.

Such a system wouldn't really be a problem for the Fermi Paradox. Like I said, it's only in a very narrow window of time that we'd have any idea if our solar system had been visited by such a thing. The solar system could have been visited by thousands of waves of these probes and the only way to know would be to thoroughly explore the asteroid belt and find the sites where they've extracted materials for replication, and possibly the defunked millions of years old probes themselves. If the probes stay behind are the system is supposed to be Ragnarok proof then it's more problematic though.

[Singular Intellect]

I suppose it's possible that any species that has the intelligence to start building advanced technology inevitably hits a technology singularity, and the odds of a species suviving that are arguably extremely low, because they just aren't smart enough to produce a positive outcome.

[Serafina]

-Usage of tools to fabricate other tools is extemely rare.

I doubt it. Animals use tools and it isn't a big leap to alter your tools using other tools to make them better.

Show me an single animal that uses tools to fabricate other tools. Using a tool is as simple as picking up a stone to crack a nut. Even making some slight alterations to it (like cleaning a branch) is not that complicated, and can easily be discovered by accident. (we have observed this).
However, making tools to produce tools with requires quite some pre-thought - and we do not have observed such behaviour in any species expect humans (and our ancestors).

-Using automated production is extremely rare.

Why? That only works if every society ends up static, unchanging and dedicated to the status quo. It doen't work if the societies have to compete with each other and are trying to get advantages to undermine each other.

We took thousands of years to make use of it. Societies CAN end up mostly static, if they are not agressive (or their neighbors). Perhaps we are agressive enought to continue our development, but not too agressive to be no longer able to form prospering societies?

-Discovering the scientific method is extremely rare.

There is nothing intrinsically unbelievable about the scientific method.

And yet, it took a very long time for us to discover it.

-Interstellar travel is just plain impossible, expect for probes

... I have been talking about probes.

Yeah, but why should you send probes to remote stars? Making it a two-way trip is complicated, and radio transmissions are likely to be badly scrambled. Just sending a probe and getting nothing from it is pointless. Likewise, constructing an expensive, complicated probe that CAN report is useless if you can not colonize the star.
If anything, they are likely to scan neighboring systems, but not remote ones.

-other intelligent species evolve their technology and society at an extremely low pace

That sounds too much like "humans are special". I think it is more likely that societies get out of the ruts they are in very slowly- the hunter gather period was most of humanities existance on the planet after all.

Well, if we are speculating whether or not we are the only sentient species (adn for all we know, we are) in a huge part of this galaxy, we are possibly special. It is an valid reason.

Van Neumann devices in general do not make a lot of sense if you do not GAIN anything from it. While research is a viable interest for every civilisation capable of reaching space, it is not a given that they are willing to pour a shitload of resources into something that has no benefit whatsoever within dozens or hundreds of lifetimes - or at all.

[NecronLord]

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.

[Junghalli]

Yeah, but why should you send probes to remote stars?

Because you're curious about what's there.

Making it a two-way trip is complicated, and radio transmissions are likely to be badly scrambled.

I imagine lasers would probably work better than radio.

[Broomstick]

What if there are aliens but they are adapted to a much difference environment and thus view Earth as too hostile to bother with? There's a wide range of temperature/pressure/etc. tolerances among life forms on earth, after all, it is not inconceivable for "life as we know it" to favor conditions seldom found on earth.

[Junghalli]

What if there are aliens but they are adapted to a much difference environment and thus view Earth as too hostile to bother with? There's a wide range of temperature/pressure/etc. tolerances among life forms on earth, after all, it is not inconceivable for "life as we know it" to favor conditions seldom found on earth.

The problem is really more why isn't our solar system full of the alien equivalent of O'Neill colonies.

[TheLostVikings]

What if there are aliens but they are adapted to a much difference environment and thus view Earth as too hostile to bother with? There's a wide range of temperature/pressure/etc. tolerances among life forms on earth, after all, it is not inconceivable for "life as we know it" to favor conditions seldom found on earth.

The problem is really more why isn't our solar system full of the alien equivalent of O'Neill colonies.

Perhaps unlike us the hypothetical aliens can easily tell the difference between actual gravity and centripetal pseudoforces, and thus prefers to live on Real PlanetsTM? Perhaps living on planets has simply been the hot thing in galactic living fashion for the past couple of billion years?

For silicon based life the "habitable zone" would be much closer than ours, and for amonia based life it would be much further out. Our assumptions about what makes a solar system "ideal" for life to appear are exactly that: Assumptions. Extrapolated from a data point of one.

And you know what they say about assumptions...

[Guardsman Bass]

Yeah, but why should you send probes to remote stars?

Because you're curious about what's there.

You don't need to send probes there to do that.

This seems to be anthropomorphizing potential aliens. They may very well decide that the resources required to send probes elsewhere just for curiosity's sake isn't worth, or may have a different view of what's "curious" and worth investigating than we do.

That said, I'm in the "multiple filters" camp, although you could probably go into more specifics in the "sapient species does not developed advanced technology category". What if, for example, you had a species that never developed the equivalent of an "eye", and has no concept of astronomy or anything outside of the environment in which they can travel immediately (the ground or possibly atmosphere)? It's very hard to imagine a race like that developing interstellar space probes - on their own, they might never even discover that there is anything beyond their world.

The problem is really more why isn't our solar system full of the alien equivalent of O'Neill colonies.

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.

[Junghalli]

What if, for example, you had a species that never developed the equivalent of an "eye", and has no concept of astronomy or anything outside of the environment in which they can travel immediately (the ground or possibly atmosphere)? It's very hard to imagine a race like that developing interstellar space probes - on their own, they might never even discover that there is anything beyond their world.

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.

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.

[Civil War Man]

This isn't really new and still fails the basic problem. With a simple Von Neuman and STL you can cover the whole Milky Way Galaxy in a couple million years. So... why aren't they here yet?

Who says they would necessarily make the effort?

Not only that. Suppose there is a civilization that made the effort, and launched their probes 10,000 years ago. It could be another 100,000 years or more before the probe reaches the range where it would be detected by today's astronomical equipment, and that's if they're pretty close neighbors.

Or suppose they did it 10,000,000 years ago. "Huh. This planet has life on it, but it's going to be a very long time before they even remotely start to catch up with us, if they even make it that far. We'll add it to our list of inhabited planets, but it's not going to be worthy of our attention."

[Lord of the Abyss]

Not an idea original with me, but I agree with it : it seems to me that if the idea of colonizing/exploring the galaxy with VN probes is actually practical, and there are multiple technological species in this galaxy, there's a plausible reason why the galaxy isn't swarming with them. It's "against interstellar law" - or at least, the will of the older cultures. The danger of some genocidal/conquest minded/rabidly expansionist culture being able to release a swarm of madly replicating probes that'll gobble up everything but themselves is too great. Even if they had no interest in expansion, I'd think there'd be a good chance that a high tech culture would release "police probes" designed to keep some other civilization from running wild.

In this scenario, the probes are probably already here; but they are sitting quietly, just waiting in case they see a probe from another culture show up and start converting the asteroid belt into warships or something of the sort.