Billions and Billions of "Earths" in the Milky Way

[magnemoe]

I don't understand this...

If someone has the tech to travel interstellar distances what could they possibly want from our gravity well.

I can see if we were higher advanced and could be seen as a threat simply knocking our planet into the sun, but theres just nothing on the planet that would be valuable.

Well if you don't colonize planets you could just as well stay home and build habitats in kerbin orbit and some Mun bases. Adding more planets brings glory to the emperor.

Much easier if the planet come with an ready ecosystem, the cheap labor is an nice bonus as you just has to convince them to become subjects to the emperor.

No, its not so plausible however we don't know how aliens think and welfare states don't build interstellar empires.

[magnemoe]

"the fact that we don't see fusion-powered alien ships flying around our solar system suggests that interstellar travel might not so widespread."

Yes, it certainly suggests that... but the question is why is it not?

Is it:

1) Few planets actually suitable for life to arise/start? (habitable != conducive to abiogenesis)

2) Few planets actually suitable for complex life?

3) Evolution from simple (like single cells) life to complex (multicellular or syncytical for example) is infrequent or too slow given the life time of many stars?

4) Complex life rarely evolves into a species that establishes a technological civilization?

5) Technological civilizations rarely last long enough to achieve controlled fusion?

6) Civilizations that achieve controlled fusion rarely use it for interstellar travel?

If its not one of 1-5, then there should be multitudes of technological civilizations with controlled fusion, whom can at least colonize their local solar system, and thus are likely to be extremely long lasting. It seems incredulous to me that of these multitudes, not one has embarked on an expansionist phase. Therefore I conclude the problem lies somewhere in 1-5.

I'd say we're only a century or two away from controlled fusion.... and at that point we can begin sending drones carrying biological packages, etc, even if the voyage is too long for us. It would ensure our legacy, and it would also be conducive to defense... we'd start to establish a buffer zone between us an other potential alien civilizations... the best defense is a good offense and all that. If we start an expansion program, we're less likely to be swallowed by an alien's (for that matter, if we encountered aliens more primitive than us, I'd hope we'd study them, rather than exterminate them).

When you think of other possible technologies, like bussard ramjets, the travel time (especially due to time dialation), shrinks a lot. Then if you consider a civilization that has some sort of collective consciousness (borg like?), then its even more likely that they would find it worthwhile to expand.

Generally, the overall picture of life, is that it expands where it can. Why should technological civilizations be any different?

1 and 2, if we talk earthlike planets as they estimate we talk about planets who can support complex life. It probably is far more, suspected that planets close to smaller stars can also support life.

Note that an water planet, might have complex life but not an technical civilization, even if it has some land the areas will be to small for advanced land animals to evolve.

3 If we use earth as an template life evolved fast, however it took billions of years before the atmosphere held enough oxygen for complex life. Complex life was also slowed because climate on early earth was very unstable, look like it was frozen like an ice planet before the Cambrian explosion.

4 best to differentiate here, dinosaurs probably even fish is complex life. Humans 250.000 years ago was intelligent. It look like complex life is pretty easy. Intelligence is an chance factor.

Then the first humanoids started to become significantly smarter than apes they became more intelligent over time. The natural environment did not cause this, many suspect the other humanoids and the early language had an effect, other humanoids was the most complex thing in their environment. This might not be true for all species or simply that they use other markers for breed. High chance they don't become smarter than early humanoids.

For technical civilization, I think the two important factors was printing press and steam engine. first caused information revolution three, first was language, second was writing, now you had the option to mass produce information, the steam engine gave you power. Someone simply had to use this advantage. Again might not be true for aliens.

Now to transform an industrialized society to something advanced it looks easy for humans. Might not be true for all aliens.

5 fusion is probably easier than you think I say 10-20 rather than 200 years. However this is for humans, an aggressive alien will continue nuking his enemies, some others might create an world government like imperial china. Both ideas is bad and has an decent chance of killing them off.

6 yes, as I said welfare states don't produce interstellar empires, the matrix is more fun, might be something in the future who kills advanced civilizations.

On the other hand, had we been lucky we would had three planets with advanced life in the solar system, the space race would not have ended, Soviet union would probably have fallen earlier trying to follow up. We would have had colonies on the Venus with less dense atmosphere and a larger Mars.

[magnemoe]

This ^

There's 2 things that could happen with aliens, peaceful encounter or destroyed from a distance without ever seeing what is coming.

Aliens come to take our minerals/water/women/whatever is so laughable.

Major downside with throwing rocks. If the other part has an self supplied asteroid civilization rocks don't help you much and the other side will throw back. Even more fun if you hit an colony world. Note that for humans its probably 200 years from high powered radio signals to an self supplied asteroid civilization, some aliens might be faster.

Now invading over interstellar distances using slower than light is impossible if the other part has an space civilization (man kziin war), against earth today its easy.

[AndrewBCrisp]

One thing that has bugged me lately about all these "a single race can colonize the galaxy in <50 million years" statements is the implicit assumption that any species wants to expand. I am not convinced that this is the case.

Consider our own expansion on this planet. While we were nomadic for a long time, our nomadic period was mostly in the "follow the food source" mode, not the "let's just see what's over that mountain" mode. Once we developed agriculture and animal husbandry, we settled down pretty quickly.

Since then, when humans expand, it is usually because the alternative - staying home - is considered worse. The ancient Greeks, for example, founded colonies around the Mediterranean because they were running out of space at home. The Polynesians would use up resources on one island and then travel by boat to the next island. The first Americans followed big game to North America because conditions in Asia during the last ice age were too harsh. Europeans only started colonizing North America en masse because they had cultural and religious groups that could not stay at home without being destroyed - and it was easier to boot out the misfits than force them to conform.

Time and again, we stay in place, with only a few people wanting to go into unfamiliar territory. In groups, though, we move only when we must.

As below, so above. Alien races, regardless of their psychology or social structure, will likely follow a similar pattern on their homeworlds. It's safer to stay where you know you have food and water and shelter, than to pack it up and go where you might not have food, or water, or shelter. You take the risk only when staying home is no longer safe for one reason or another.

Likewise, if we apply this pattern to interplanetary and interstellar migration, what we find is that serious colonization will not happen until conditions Out There seem better than Down Here. Before that point is reached, there will certainly be explorers, scientific or nationalistic expeditions, even small colonies, but the species will not commit to serious colonization until the alternative is worse. All available spheres of influence and resources on the homeworld would have to be either used up or claimed by one faction or another, thus preventing any new faction or culture from springing up. If any attempt to do so, they face the option of conforming, imprisonment - or migration. Similarly, serious interstellar colonization will not take place until a similar situation happens in the home system - all resources claimed, spheres of influence locked in and strictly enforced.

Given that a single star system has a lot of resources and places to settle already present, this saturation point may not be reached for tens or even hundreds of thousands of years.

Every new system that is settled starts the process anew. Gradual expansion until the new system is "saturated", then migration of splinter cultures to neighboring systems. Again, this process would take millenia to complete per system.

It could very well be, therefore, that the big reason why we haven't seen anyone yet because nobody has reached us yet.

[KerikBalm]

One thing that has bugged me lately about all these "a single race can colonize the galaxy in <50 million years" statements is the implicit assumption that any species wants to expand. I am not convinced that this is the case.

As I already said....

"If its not one of 1-5, then there should be multitudes of technological civilizations with controlled fusion, whom can at least colonize their local solar system, and thus are likely to be extremely long lasting. It seems incredulous to me that of these multitudes, not one has embarked on an expansionist phase. Therefore I conclude the problem lies somewhere in 1-5."

"it would also be conducive to defense... we'd start to establish a buffer zone between us an other potential alien civilizations... the best defense is a good offense and all that. If we start an expansion program, we're less likely to be swallowed by an alien's"

"Survival of the fittest will surely operate galaxy wide (not that survival of the fittest = always war, there are many symbiotic relationships where each entity increases its fitness through cooperation).

Species that expand will persist and become more prevalent, species that don't will disappear."

If we assume technological civilizations are common, then it seems incredulous that not a single one has embarked on an expansionist phase. Also, add in the billions of years they have to change their mind, and potential advances beyond that (ramjets and Antimatter), that make it even easier and shorter to do so.

If there are only a handful of such civilizations, this objection is reasonable... if there are millions of them... this is not reasonable.

If there are millions across the galaxy, and they only spread locally, you'd still see the galaxy becoming pretty full, pretty fast. And there are strong incentives to expand locally... at least within the nearest 10 light years or so, where travel isn't *that* hard with sufficiently advanced slower than light travel.

I don't buy the argument that the galaxy is packed full of technological civilizations, but not a single one has decided it would be a good idea to expand beyond their start system.

Likewise, I don't buy the argument that the galaxy is packed full of technological civilizations, but every single one has decided to hide their existence or operates in a way that we can't detect them.

These arguments can work if we assume only a few civilizations, but thats assuming some variant of Rare-Earth.

[AndrewBCrisp]

I believe you miss my meaning, KerikBalm - probably because I haven't elaborated as much as I should have.

I'm not stating that species do not expand. I am saying that such expansion will be slower, and not sustainable over the billenia required to colonize the galaxy.

The essential assumption being made by "rapid expansion" theories is that a species - let's cleverly call them X - once it starts seeding neighboring stars will not stop. Ever. I don't think so. Let's look at how rapid expansionists see X's expansion throughout the galaxy:

1. Species X arises on a planet. Over time, thousands of years mostly, it soon occupies all niches on that planet.

2. Species X looks to the planets and the stars, declares a "Manifest Destiny", and starts a grand campaign, lasting millions of years, to colonize. We are assuming that Species X does not develop any form of faster-than-light travel or communication.

3. ??? Somehow, Species X is able to maintain its focus over a timeframe of millions of years, and over a scope of hundreds or even thousands of light-years in diameter. Each colony, once established, spends only a short time ensuring its survival and then begins working on the next phase of interstellar expansion. No colony falters or changes its mind - or at least, not enough colonies do so to matter.

4. Profit! Species X fills up the galaxy.

This is the model I question. Specifically, steps 2 and 3.

Life - and civilization - tends to move along the path of least resistance, on the paths that expend the smallest amount of energy needed to accomplish the goal. We expend more energy than "necessary" only when it becomes tied to our survival. To use one of the examples I used in my last post: once Europeans started colonizing North America, they filled up North America. The American colonists did not start looking for another continent to colonize in the name of European civilization. This is because there were plenty of resources and living space on the continent they found, that searching for a new continent made no sense. Meanwhile, Europe gradually lost interest in expansion.

(I am aware, of course, that the Europeans dislodged a number of native cultures already living on North America. Let us hope our future descendants are more ethical).

Whether a species colonizes a continent, a planet, or a solar system, you have only so much living space and resources to go around. Unless our species is a race-mind, you will also likely have a variety of cultures within that species, with new cultures splintering off the parent culture. This means we get competing spheres of influence.

Eventually, within a given region, all available living space and all available resources are claimed by one culture or another. Their spheres of influence are now set. If a new culture arises, it now cannot establish itself, because the existing cultures are not likely to divide up their finite resources to support it. The result is that the new culture must do one of the following: take resources by force, assimilate into one or more of the cultures already existing, or leave to find unclaimed territory elsewhere.

That last option is the one for expansion, but its the highest energy expenditure of the lot. First you have to find a place where you might be able to live. Then you have to travel there, carrying all the basics so you can survive and start building a new civilization there. Then you have to survive long enough to build that civilization. It happens because there are times where migration is still lower energy - or at least lower negative outcome - than warfare.

Once that high energy expenditure is made, however, the splinter culture goes back to low energy use. Let's look at Species X now from this perspective.

Steps 1 and 2 remain the same as in our original scenario, but something happens to the colonies when they arrive at their destinations:

3(a): The colonists find a whole new planet or solar system full of resources and living space they can expand into. Species X's central government (the one with "Manifest Destiny" on the brain) is now too far away to rap knuckles. Why waste time and resources expanding to yet another star system when the colonists have all they need here and nobody to force them to do otherwise?

4(a): The colonists build their own culture, separate from Species X - let's call them X'. X' eventually develops splinter cultures, just as X did on its home world. These splinter cultures take the low-energy way out, migrating to other planets or asteroids in the same system as X'. This process continues until nobody can safely migrate without grabbing already claimed territory and sparking wars. Given the vast amount of resources within a given system, this process will take many thousands of years to run its course.

5. Back in the home system, Species X's "manifest destiny" ideology burns out. The rebellion of the colonies, once news filters back home, sparks disillusionment in the fiction of continuing a species' existence by seeding it elsewhere. After all children never want what their parents want. Meanwhile, other - presumably more ethical - ways of dealing with cultural disputes are found, Species X integrates into a system-wide culture which leaves colonization behind. Missions of exploration may be launched, and trade with the former colonies may occur, but new interstellar colonies are no longer seeded by Species X.

6. Species X's expansion in the galaxy grinds to a halt. The daughter cultures may repeat the cycle, expanding to neighboring star systems once they've occupied all available living space in their system, but by that time, they have evolved into something different from the culture or species that seeded them.

So eventually intelligent life can spread through the galaxy, but the rate of expansion will likely be much, much slower. And each wave of expansion brings with it different cultural evolution. The final result is that no one species can or will fill up the entire galaxy.

I hope this makes my point clearer.

[Krevsin]

I still think that the idea of multiple earths is, for now, like a picture of bottled water to a thirsty man. While it's certainly something to strive towards, the main concern should be finding water in any way, shape or form.

And by that I mean: Cool story, bro, but space access needs to be a lot cheaper, rocket flights more frequent and interstellar propulsion more developed before any of this becomes relevant outside of a distant ideal to strive towards.

[Scotius]

You've made a valid argument...for Homo sapiens species . We don't know what other intelligent species think about interstellar expansion, nor how they would attempt it.

[AndrewBCrisp]

Certainly alien species will think differently from us, but unless the laws of nature are dramatically different where they are, they will be bound by the same restrictions as we. There will always be finite amounts of resources and labor to be had. No one civilization can maintain a course of action indefinitely - the changing conditions in the universe would ultimately thwart such single-mindedness. Unless a species is a race-mind (which imposes its own limits to expansion), all species will likely differentiate into various small groups, be they herds, hives, tribes, schools, flocks, or something else. These groups will evolve different strategies that in turn become different cultures.

All species will have a concept of daily life, and, barring immortality, that daily life will probably be dominant in their thinking. Longer-term planning only become necessary once a species becomes aware of longer-term problems or longer-term goals. Thus, long-term plans will be something a species will employ from time to time, but, because of its higher energy requirement, will never become the norm.

Interstellar expansion is very high-energy, very long-term indeed. Not impossible, but certainly very difficult. I expect all species will eventually try it, but for the reasons I outlined above, each species will do so in fits and starts, rather than a long, unbroken campaign of galactic conquest.

The laws of nature can be great equalizers in discussions like these. No matter who you are, no matter how you think, physics trumps everything else.

[magnemoe]

I believe you miss my meaning, KerikBalm - probably because I haven't elaborated as much as I should have.

I'm not stating that species do not expand. I am saying that such expansion will be slower, and not sustainable over the billenia required to colonize the galaxy.

The essential assumption being made by "rapid expansion" theories is that a species - let's cleverly call them X - once it starts seeding neighboring stars will not stop. Ever. I don't think so. Let's look at how rapid expansionists see X's expansion throughout the galaxy:

1. Species X arises on a planet. Over time, thousands of years mostly, it soon occupies all niches on that planet.

2. Species X looks to the planets and the stars, declares a "Manifest Destiny", and starts a grand campaign, lasting millions of years, to colonize. We are assuming that Species X does not develop any form of faster-than-light travel or communication.

3. ??? Somehow, Species X is able to maintain its focus over a timeframe of millions of years, and over a scope of hundreds or even thousands of light-years in diameter. Each colony, once established, spends only a short time ensuring its survival and then begins working on the next phase of interstellar expansion. No colony falters or changes its mind - or at least, not enough colonies do so to matter.

4. Profit! Species X fills up the galaxy.

This is the model I question. Specifically, steps 2 and 3.

Life - and civilization - tends to move along the path of least resistance, on the paths that expend the smallest amount of energy needed to accomplish the goal. We expend more energy than "necessary" only when it becomes tied to our survival. To use one of the examples I used in my last post: once Europeans started colonizing North America, they filled up North America. The American colonists did not start looking for another continent to colonize in the name of European civilization. This is because there were plenty of resources and living space on the continent they found, that searching for a new continent made no sense. Meanwhile, Europe gradually lost interest in expansion.

(I am aware, of course, that the Europeans dislodged a number of native cultures already living on North America. Let us hope our future descendants are more ethical).

Whether a species colonizes a continent, a planet, or a solar system, you have only so much living space and resources to go around. Unless our species is a race-mind, you will also likely have a variety of cultures within that species, with new cultures splintering off the parent culture. This means we get competing spheres of influence.

Eventually, within a given region, all available living space and all available resources are claimed by one culture or another. Their spheres of influence are now set. If a new culture arises, it now cannot establish itself, because the existing cultures are not likely to divide up their finite resources to support it. The result is that the new culture must do one of the following: take resources by force, assimilate into one or more of the cultures already existing, or leave to find unclaimed territory elsewhere.

That last option is the one for expansion, but its the highest energy expenditure of the lot. First you have to find a place where you might be able to live. Then you have to travel there, carrying all the basics so you can survive and start building a new civilization there. Then you have to survive long enough to build that civilization. It happens because there are times where migration is still lower energy - or at least lower negative outcome - than warfare.

Once that high energy expenditure is made, however, the splinter culture goes back to low energy use. Let's look at Species X now from this perspective.

Steps 1 and 2 remain the same as in our original scenario, but something happens to the colonies when they arrive at their destinations:

3(a): The colonists find a whole new planet or solar system full of resources and living space they can expand into. Species X's central government (the one with "Manifest Destiny" on the brain) is now too far away to rap knuckles. Why waste time and resources expanding to yet another star system when the colonists have all they need here and nobody to force them to do otherwise?

4(a): The colonists build their own culture, separate from Species X - let's call them X'. X' eventually develops splinter cultures, just as X did on its home world. These splinter cultures take the low-energy way out, migrating to other planets or asteroids in the same system as X'. This process continues until nobody can safely migrate without grabbing already claimed territory and sparking wars. Given the vast amount of resources within a given system, this process will take many thousands of years to run its course.

5. Back in the home system, Species X's "manifest destiny" ideology burns out. The rebellion of the colonies, once news filters back home, sparks disillusionment in the fiction of continuing a species' existence by seeding it elsewhere. After all children never want what their parents want. Meanwhile, other - presumably more ethical - ways of dealing with cultural disputes are found, Species X integrates into a system-wide culture which leaves colonization behind. Missions of exploration may be launched, and trade with the former colonies may occur, but new interstellar colonies are no longer seeded by Species X.

6. Species X's expansion in the galaxy grinds to a halt. The daughter cultures may repeat the cycle, expanding to neighboring star systems once they've occupied all available living space in their system, but by that time, they have evolved into something different from the culture or species that seeded them.

So eventually intelligent life can spread through the galaxy, but the rate of expansion will likely be much, much slower. And each wave of expansion brings with it different cultural evolution. The final result is that no one species can or will fill up the entire galaxy.

I hope this makes my point clearer.

I agree here, they will loose focus, going from an colony to sending an new starship will take time. One important thing is the average distance between usable planets is it 20 or 50 lightyear.

Another thing is that you don't travel to other stars unless you have lots of resources. You travel to secure the species, for knowledge and manifest destiny.

You do not travel to another star because you have to as then you don't have the resources anymore.

Not saying its worthless, if the target has advanced life you might find something useful, the potato was the most valuable the Spanish took back from america.

Finding an more advanced civilisation who don't travel might be very profitable.

But profit or resources will not be the main driver.

Still I think this is the most likely first contact scenario.

http://fc07.deviantart.net/fs70/f/2012/177/5/4/first_contact_5_by_olsen1a-d54w8yu.jpg

[KerikBalm]

One species may lose focus... but if they were all over the galaxy, it wouldn't take very long to fill up the galaxy.

If I may make an analogy to microbiology here.... If you put one bacteria on an agarose plate, one colony forms, that gradually spreads... and takes a long long long time to cover the whole plate (its growth does not follow a simple exponential curve, as only those along the circumference grow, in which case its a much more linear growth)

But if you plate about 1,000 bacteria on your plate (roughly equal distribution)... overnight you have a "lawn" of confluent colonies....

That we don't see "confluence" should mean that there aren't that many out there.

And you're also assuming governments as fickle as the US government who can't agree on anything.

If we have some sort of collective or single consciousness, then the time span is not such a big deal, and its likely the goal could be pursued longer, with a view towars the "bigger picture"

It would also send out colonies to avoid using up all the resources, leaving the center to die while only the periphery is expanding. A more uniform expansion prevents the center from dying out so fast.

I would say that generally speaking, life tends to spread... aggressively. Lets not just consider one case for one species (colonization of the Americas), but life in General... and even in the case of american colonization... they spread across the continent quite rapidly, and filled it in later.

Like I think a species would do with our galaxy, before even considering an inter galactic expedition.

[Moon Goddess]

The better Fermi Paradox is not why has no one attacked us or talked to us, the best question is.

Why isn't the whole galaxy converted to Von Neumann probes, long long before we ever evolved.

[AndrewBCrisp]

Depends on what you want your Von Neumann probes to do: Robotic Replicators thoughts at Centauri Dreams

Quoting from the article:

And perhaps there lies the answer to Fermi’s Paradox. Maybe intelligent extraterrestrials are more interested in making a good first impression than the incessant consumption of resources. Perhaps that is why the Solar System wasn’t scoured by a wave of Von Neumann probes long ago. The folly of our assumption is that we see all before us as resources to be utilised, but why should intelligent extraterrestrial life share that outlook? Maybe they are more interested in contact than consumption – a criticism that can be levelled at other ideas in SETI, such as Kardashev civilisations and Dyson spheres that have been discussed recently on Centauri Dreams. Perhaps instead there is a Bracewell probe already here, lurking in in a Lagrange point, or in the shadow of an asteroid, watching and waiting to be discovered. If that’s the case, it may be one our own Von Neumann probes that first encounters it – and we want to make sure that we make the right impression with our own probe the day that happens.

[Warhorse]

I believe you miss my meaning, KerikBalm - probably because I haven't elaborated as much as I should have.

I'm not stating that species do not expand. I am saying that such expansion will be slower, and not sustainable over the billenia required to colonize the galaxy.

The essential assumption being made by "rapid expansion" theories is that a species - let's cleverly call them X - once it starts seeding neighboring stars will not stop. Ever. I don't think so. Let's look at how rapid expansionists see X's expansion throughout the galaxy:

1. Species X arises on a planet. Over time, thousands of years mostly, it soon occupies all niches on that planet.

2. Species X looks to the planets and the stars, declares a "Manifest Destiny", and starts a grand campaign, lasting millions of years, to colonize. We are assuming that Species X does not develop any form of faster-than-light travel or communication.

3. ??? Somehow, Species X is able to maintain its focus over a timeframe of millions of years, and over a scope of hundreds or even thousands of light-years in diameter. Each colony, once established, spends only a short time ensuring its survival and then begins working on the next phase of interstellar expansion. No colony falters or changes its mind - or at least, not enough colonies do so to matter.

4. Profit! Species X fills up the galaxy.

This is the model I question. Specifically, steps 2 and 3.

Life - and civilization - tends to move along the path of least resistance, on the paths that expend the smallest amount of energy needed to accomplish the goal. We expend more energy than "necessary" only when it becomes tied to our survival. To use one of the examples I used in my last post: once Europeans started colonizing North America, they filled up North America. The American colonists did not start looking for another continent to colonize in the name of European civilization. This is because there were plenty of resources and living space on the continent they found, that searching for a new continent made no sense. Meanwhile, Europe gradually lost interest in expansion.

(I am aware, of course, that the Europeans dislodged a number of native cultures already living on North America. Let us hope our future descendants are more ethical).

Whether a species colonizes a continent, a planet, or a solar system, you have only so much living space and resources to go around. Unless our species is a race-mind, you will also likely have a variety of cultures within that species, with new cultures splintering off the parent culture. This means we get competing spheres of influence.

Eventually, within a given region, all available living space and all available resources are claimed by one culture or another. Their spheres of influence are now set. If a new culture arises, it now cannot establish itself, because the existing cultures are not likely to divide up their finite resources to support it. The result is that the new culture must do one of the following: take resources by force, assimilate into one or more of the cultures already existing, or leave to find unclaimed territory elsewhere.

That last option is the one for expansion, but its the highest energy expenditure of the lot. First you have to find a place where you might be able to live. Then you have to travel there, carrying all the basics so you can survive and start building a new civilization there. Then you have to survive long enough to build that civilization. It happens because there are times where migration is still lower energy - or at least lower negative outcome - than warfare.

Once that high energy expenditure is made, however, the splinter culture goes back to low energy use. Let's look at Species X now from this perspective.

Steps 1 and 2 remain the same as in our original scenario, but something happens to the colonies when they arrive at their destinations:

3(a): The colonists find a whole new planet or solar system full of resources and living space they can expand into. Species X's central government (the one with "Manifest Destiny" on the brain) is now too far away to rap knuckles. Why waste time and resources expanding to yet another star system when the colonists have all they need here and nobody to force them to do otherwise?

4(a): The colonists build their own culture, separate from Species X - let's call them X'. X' eventually develops splinter cultures, just as X did on its home world. These splinter cultures take the low-energy way out, migrating to other planets or asteroids in the same system as X'. This process continues until nobody can safely migrate without grabbing already claimed territory and sparking wars. Given the vast amount of resources within a given system, this process will take many thousands of years to run its course.

5. Back in the home system, Species X's "manifest destiny" ideology burns out. The rebellion of the colonies, once news filters back home, sparks disillusionment in the fiction of continuing a species' existence by seeding it elsewhere. After all children never want what their parents want. Meanwhile, other - presumably more ethical - ways of dealing with cultural disputes are found, Species X integrates into a system-wide culture which leaves colonization behind. Missions of exploration may be launched, and trade with the former colonies may occur, but new interstellar colonies are no longer seeded by Species X.

6. Species X's expansion in the galaxy grinds to a halt. The daughter cultures may repeat the cycle, expanding to neighboring star systems once they've occupied all available living space in their system, but by that time, they have evolved into something different from the culture or species that seeded them.

So eventually intelligent life can spread through the galaxy, but the rate of expansion will likely be much, much slower. And each wave of expansion brings with it different cultural evolution. The final result is that no one species can or will fill up the entire galaxy.

I hope this makes my point clearer.

This is a likely path for species X to follow, IMO, if and only if X chooses to expand by actually moving population around directly. If X expands by using von Neumann probes to create population in situ, the expansion will proceed much more swiftly, and there's no real reason to assume it will run out of steam, absent programmed limits. Since the latter method is orders of magnitude cheaper than the former, it is, IMO, rather more likely to be used ...

[falofonos]

I'd recommend "Existence" by David Brin,

Also the interstellar environment is poorly understood to put it mildly, it may not be possible for any form of self replicator (life or machine) to safely move between stars.

Then there's the problem of deep time : We've been transmitting relatively coherent radio waves for maybe 80 years consistently, our civilisations only produced written language 6000 odd years ago. Alien civilisations may have risen and fallen while we were still running around after the food.

http://en.wikipedia.org/wiki/Gamma-ray_burst

Although stellar lifespans are long there are lots of them, plenty of opportunities for life to be exterminated across large swathes of the galaxy by supernovae and gamma ray cones from other galaxies.

While the expansionist aliens may have spread, they're quite likely to have also been destroyed or collapsed due to natural disaster on a massive scale or just through mutation / evolution / loss of expansionist desire / stagnation or cultural drift.

Edited November 11, 2013 by falofonos

[KerikBalm]

"While the expansionist aliens may have spread, they're quite likely to have also been destroyed or collapsed due to natural disaster on a massive scale or just through mutation / evolution / loss of expansionist desire / stagnation or cultural drift."

Once they've got the capability to move between stars (and actually used it), even a gamma ray burst wouldn't wipe them out.

Even if they're still in their home system, if they've got self sustaining subterranean asteroid/moon/planets colonies (as is likely on bodies exposed to radiation belts already), they'd survive a gamma ray burst.

And thats not even considering a "terminator" scenario where biological life is eclipsed by machines it creates.

mutation/evolution would not lead to their extinction without an outside cause.

[magnemoe]

The better Fermi Paradox is not why has no one attacked us or talked to us, the best question is.

Why isn't the whole galaxy converted to Von Neumann probes, long long before we ever evolved.

Why should anybody want to convert the galaxy to Von Neumann probes?

Yes life want to spread out, however the stars are hard to reach, a system who mainly focused on producing more probes would be very unlikely to be able to build an starship, far easier to fight for resources inside an star system.

Star travels second requirement is that you have more resources than you can use. The obvious first it having the technology.

[Person012345]

I think the answer to the fermi paradox is that they simply never bothered, for the same reasons we haven't bothered yet and by the time they were under cataclysmic threat it was too late. Maybe.

Though it is a hard one.

[Depth]

Von Neumanns remind me of the old 90s game Machines, by Acclaim.

The story went that the Earth was getting desperately low on resources and decided to send machines capable of setting up an infrastructure to extract resources and create the foundations of colonization on planet after planet. They lost contact with the machines, and so decided to send more. Upon arrival elsewhere in the galaxy the new machines eventually found the established machines. The two Controllers each staked claim to completing the mission, believing the other to be faulty. The entire dialogue lasted a fraction of a microsecond, and led to an interplanetary war on a MASSIVE scale, with tons of resources spent on weapons development.

Sadly the story declined when the game got going.

[Savage117]

I think intelligent life exists all over this galaxy, not just tiny hotspots here and there, im thinking at least millions for each galactic arm. Even more for non-intelligent life. Its always been my theory that any complex life can become intelligent, it only takes time and a little luck. We Humans survived the cataclysm that destroyed the dinosaurs, we were probably some sort of rodent or marsupial at the time, but we were there, its possible that helped jump start our rise to intelligence, perhaps it was needed for our species to survive, you either adapt or go extinct.

I think the reason we haven’t run into other intelligent life in our galaxy yet is because of the vast distances and species bias. Even though we have been sending out radio signals for more than a 100 years, those signals degrade, they degrade to point of being undecipherable just several light years away from out solar system. Only a narrow, directed, radio wave would be able to be deciphered at larger distances, and only what we are directing it at and anything caught in between would receive it. The chances that you would hit a passing spacecraft out in the black, or a planet that you weren't aiming at, would be mind bogglingly, astronomically tiny. Not to mention the chance that some space anomaly re-directs or garbles your message. So that means that only the nearest stars have even had the chance to hear our radio signals and the stars we have specifically sent narrow radio beams to, that is a very small number, plus we have to take into effect the age of those signals when they reach those stars. In the most ideal situation, we will only be able to be detected from about 50 light years away, and not in a sphere like you’d think, more like a bunch of spotlights flailing about the area. The Earth is a dim radio disco ball in the middle of a very deep ocean.

The second hurdle is species bias. For some reason many humans seem to think life can only exist if there is liquid water, on a planet that is in the "Goldilocks" zone, many seem to think it also has to be a similar atmosphere to Earths as well. I can't accept this as true. I think life can spring up anywhere, given the right conditions, even in a vacuum. And this life, if it were intelligent, would probably be looking for life on other planets similar to its own, just like us. We look for "Earth like" planets because its what we know works, we know a planet with similar conditions as ours is going to have life similar to ours, if life evolved their, it may act and look very different to us but it would be "life" as we know it. But that is, statistically, very unlikely to be the case, and if this life evolved on a planet where its an Argon Oxygen mix they would likely believe, just like us, that life as they know it could only evolve on such a planet. I think because of this we are just missing each other, or we are too far away to hear.

The galaxy is a humungous place and the chance that a spacecraft from another species goes passing through our system, even if there are millions of space fairing species out there, is still infinitesimally small, and just as small is the chance that we see it if it does pass through.

Space is big guys and gals, very, very big.

P.S. OP you should change your title to "Billions and Billions" as a nod to Carl Sagan.

[Person012345]

I think intelligent life exists all over this galaxy, not just tiny hotspots here and there, im thinking at least millions for each galactic arm. Even more for non-intelligent life. Its always been my theory that any complex life can become intelligent, it only takes time and a little luck. We Humans survived the cataclysm that destroyed the dinosaurs, we were probably some sort of rodent or marsupial at the time, but we were there, its possible that helped jump start our rise to intelligence, perhaps it was needed for our species to survive, you either adapt or go extinct.

I think the reason we haven’t run into other intelligent life in our galaxy yet is because of the vast distances and species bias. Even though we have been sending out radio signals for more than a 100 years, those signals degrade, they degrade to point of being undecipherable just several light years away from out solar system. Only a narrow, directed, radio wave would be able to be deciphered at larger distances, and only what we are directing it at and anything caught in between would receive it. The chances that you would hit a passing spacecraft out in the black, or a planet that you weren't aiming at, would be mind bogglingly, astronomically tiny. Not to mention the chance that some space anomaly re-directs or garbles your message. So that means that only the nearest stars have even had the chance to hear our radio signals and the stars we have specifically sent narrow radio beams to, that is a very small number, plus we have to take into effect the age of those signals when they reach those stars. In the most ideal situation, we will only be able to be detected from about 50 light years away, and not in a sphere like you’d think, more like a bunch of spotlights flailing about the area. The Earth is a dim radio disco ball in the middle of a very deep ocean.

The second hurdle is species bias. For some reason many humans seem to think life can only exist if there is liquid water, on a planet that is in the "Goldilocks" zone, many seem to think it also has to be a similar atmosphere to Earths as well. I can't accept this as true. I think life can spring up anywhere, given the right conditions, even in a vacuum. And this life, if it were intelligent, would probably be looking for life on other planets similar to its own, just like us. We look for "Earth like" planets because its what we know works, we know a planet with similar conditions as ours is going to have life similar to ours, if life evolved their, it may act and look very different to us but it would be "life" as we know it. But that is, statistically, very unlikely to be the case, and if this life evolved on a planet where its an Argon Oxygen mix they would likely believe, just like us, that life as they know it could only evolve on such a planet. I think because of this we are just missing each other, or we are too far away to hear.

The galaxy is a humungous place and the chance that a spacecraft from another species goes passing through our system, even if there are millions of space fairing species out there, is still infinitesimally small, and just as small is the chance that we see it if it does pass through.

Space is big guys and gals, very, very big.

P.S. OP you should change your title to "Billions and Billions" as a nod to Carl Sagan.

It's not that it should pass through. Each of the colonies should grow and start sending out it's own spaceships. The entire galaxy should be colonized by now. We have a habitable planet and they should theoretically have come to have a look as it would be a candidate for colonization.

[Monkeh]

The edge of an expansion wave for a society that is colonizing planets will eventually reach mind boggingly fast speeds. The population pressure behind it would force them to soak up resources at faster and faster speeds.

Stephen Baxter talked about a species of star crackers that sailed into a system on huge solar sails and then made the sun go nova to accelerate out again. Epic.

[Simon Ross]

I'm of the opposite view of most of the people posting it would seem. While I am fairly sure the universe is full of life bearing planets, I suspect intelligent life may be a bit of a fluke. From our own experiences of the earth, we know life started pretty early and managed to survive some pretty traumatic events including near extinction events. All in all, it would appear that life is pretty tough and will survive in most environments and through most disasters.

Intelligence on the other hand seems to have occurred only once (that we know of) and seemed to take a very long time to develop given that mammals have been around for the best part of 250 million years. Also puzzling is the fact that the development of intelligence completely bypassed entire groups of animals that occupied the earth for far longer yet must have had the same environmental and biological pressures on them to develop a more efficient method of survival.

I suppose the jury is out on whether intelligence is actually an efficient long term survival trait. As others have already mentioned, intelligence could place such a heavy demand on the resources available to it on the planet of it's birth that it ends up simply running out of basic materials and power sources before it can develop the technology to seek them further afield. In which case, yes there may well be other civilizations out there, but there is a good chance that they are living in a post technology dark age, one from which there is no possibility of escape

[magnemoe]

I'm of the opposite view of most of the people posting it would seem. While I am fairly sure the universe is full of life bearing planets, I suspect intelligent life may be a bit of a fluke. From our own experiences of the earth, we know life started pretty early and managed to survive some pretty traumatic events including near extinction events. All in all, it would appear that life is pretty tough and will survive in most environments and through most disasters.

Intelligence on the other hand seems to have occurred only once (that we know of) and seemed to take a very long time to develop given that mammals have been around for the best part of 250 million years. Also puzzling is the fact that the development of intelligence completely bypassed entire groups of animals that occupied the earth for far longer yet must have had the same environmental and biological pressures on them to develop a more efficient method of survival.

I suppose the jury is out on whether intelligence is actually an efficient long term survival trait. As others have already mentioned, intelligence could place such a heavy demand on the resources available to it on the planet of it's birth that it ends up simply running out of basic materials and power sources before it can develop the technology to seek them further afield. In which case, yes there may well be other civilizations out there, but there is a good chance that they are living in a post technology dark age, one from which there is no possibility of escape

I also find intelligence as the most obvious roadblock. It might require that you are warm blooded in the first place at least with our biochemistry as it require plenty of energy still we have had warm blooded animals a long time. Mammals not only take care of their kids but higher mammals also train them, this might come with intelligence but is an obvious requirement for an tool user with language.

The Cambrian explosion came just after earth stopped being an ice planet, this probably had to do with oxygen generation, air also had enough oxygen for advanced life. Life appeared shortly after earth could support it. Intelligence took a long time, still we could have waited another billion years.

Next roadblock, you not only need an very smart animal but also one who can use tools, if it can not use tools wait for the next one.

Second, after you get something like homo habilis, an borderline sentinel being who can make simple tools and operate well in packs you need them more intelligent and they are already doing pretty well.

Humans was lucky, the interaction within the pack created an pressure for more intelligence, the other humans was the primary challenge. This might not be true for others, not true for chimpanzees but might be true for something who is smarter. Again aliens will likely to be different, also this stops then you are smart enough to handle an language and social interactions well enough, the aliens might have an sort of primitive civilization but we would see them as borderline morons, they will use far longer than us to develop advanced technology perhaps to long.

However you was lucky and got something as smart as a human. That does it eat, probably not grass or leafs as it contains lite energy and you don't need intelligence to sneak up on an leaf, elephants is an exception, probably as they can afford the huge brain in the large body.

Either it eats fruits, roots and berries, is an predator and both as us.

Now if your diet is to specialized you will probably not be able to spread out your numbers will be limited, same is true for a predator or very large like an elephant. However in the last two cases you might spread out widely and prevent any other species from becoming intelligent. An intelligent predator might be able to do this without even being an tool user.

Predators need huge areas, their numbers will be low, this decrease the rate of innovations even if they are tool users, they still spread out like humans did using stone age technology.

To reach the next level you need domesticated plants and animals, not many of them, none in many areas, you also need population problems to generate the pressure for change far harder work beeing an stone age farmer than hunter. If you could control population growth you probably would not bother.

So yes its some problems

On the other hand I think that intelligence is an survival benefit. Humans will last far longer than the other primates, this was true 20.000 years ago and more so today.

However this is more as we are adaptable and able to spread out than we are intelligent, however you need numbers for innovations.

[WestAir]

Would we be a technological marvel if we were an ocean-barring species with the same intelligence & brain? If we lacked opposable thumbs?

If Earth had no land but we were still mammals like Dolphins, could we do half of what we've accomplished? Electricity would be an impossibility. Combustion... etc all. With no opposable thumbs how could we manipulate our environment so freely?

Technological intelligence comes from more than just a brain or sentience.