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View Full Version : Resource use as a motive for interstellar expansion



Colin Robinson
2014-Nov-28, 07:51 AM
Pursuit of physical resources has been a big motive for colonisation here on Earth. When the Spanish conquistadors arrived in the Americas, they immediately looked for gold to take back to Europe. Stephen Hawking has warned that if we make radio contact with extraterrestrials, they might come to Earth in pursuit of resources.

Interstellar colonisation, however accomplished, would require a serious amount of energy. This is because the energy you put into something is never less than the work accomplished. Work equals force times distance. Therefore, when the distance is astronomical, the work is astronomical also, so you need an astronomical input of energy to get the job done.

What physical resources could justify the energy costs of interstellar colonisation?

One answer may be: energy itself. A star is a natural fusion reactor, an immense source of energy. Colonising a new solar system means tapping the output of its sun. If energy is what interests extraterrestrials, they would hardly need a radio message from Earth to figure out that our sun (like the hundreds of billions of other stars in the galaxy) is a good source of it.

It might make economic sense to colonise a new solar system for that reason... but only if you couldn't get the energy you wanted from your own sun. Why cross an ocean in search of gold, if you already know there is a rich vein of gold to be mined in your own backyard?

Would it not make economic sense to avoid or at least postpone the costs of the trip by first harnessing as much as possible of the output of your local sun, by surrounding it with devices to catch its rays either a Dyson sphere, or a swarm of mobile devices?

If you wait until your Dyson sphere or swarm is complete, then, when you do send out your interstellar colonising mission, the interstellar mission will require a smaller fraction of your energy budget than if you had sent it out earlier.

The same logic applies to secondary colonisation colonies sending out colonies. If your purpose is to increase the amount of energy you are harnessing, would it not make sense for the primary interstellar colony to first build its own Dyson sphere or swarm, before spending energy on a secondary colonising mission?

If based on such considerations of energy economics, interstellar colonisation might eventually spread through the galaxy, but the process would be slower than if the colonisers moved out as fast as their vehicles would take them... Could that be the reason this solar system hasn't yet been colonised by extraterrestrials?

Jens
2014-Nov-28, 09:36 AM
Even if you could cross interstellar space to get energy, what would you do, recharge batteries and then bring them back to your home star? It would be terribly inefficient. A star gives you almost unlimited energy for billions of years, and the amount of energy you could bring back would be meaningless.

Colin Robinson
2014-Nov-28, 10:12 AM
Even if you could cross interstellar space to get energy, what would you do, recharge batteries and then bring them back to your home star? It would be terribly inefficient.

You wouldn't need to recharge batteries and then bring them back home. You could go to where the energy is, and do stuff with it there.


A star gives you almost unlimited energy for billions of years, and the amount of energy you could bring back would be meaningless.

A star provides a finite amount of energy, though vastly more than we currently use. It will be different if our descendants ever reach the stage of constructing some variant of a Dyson sphere.

Spacedude
2014-Nov-28, 03:12 PM
Aliens (or us) traveling across interstellar space solely for resources does not make sense, as you say there's more in the back yard than there is in the front yard so there's no need to travel across town. This is esp true with the extremely limited space travel technology we currently have on hand. If aliens have traveled here it's probably because they have found a much faster way to do so that is still beyond our imagination. Once here the only thing that we may have to offer of useful interest is our unique evolutionary gene pool of plants and animals and/or use our planet as an oasis in their travels across the vast desert of space. Of course, we can only guess at their motivations.

eburacum45
2014-Nov-28, 10:43 PM
We can perhaps assume that a civilisation based in a single solar system will increase its use of resources towards a maximum, at which time the civilisation will achieve its greatest complexity and/or sophistication. With careful use of resources this level of sophistication could be maintained for a considerable period - at least while the star is on the main sequence. If the civilisation establishes a colony in a nearby system, that colony will in due course reach a similar level of resource use and sophistication.

But, as far as I can tell, this does not really double the complexity or sophistication of the civilisation, since thse two stars are so very far apart. Communications between the two systems will be very slow, taking years or decades to pass data back and forth. The civilisation may become more diverse, but it will also become more disjointed when considered as an interacting whole. Colonise an entire galaxy, and you will get a large and diverse set of colonies which are all at roughly the same level of sophistication, but which have extreme difficulty talking to each other. (Note that I am discounting any magical faster-than-light communication here, as there appears to be no realistic chance of that).

So is there any pressing need to colonise the rest of the galaxy? Maybe there is - but not to increase the resource use or complexity of their civilisation, but instead as insurance against the future. Eventually our star will die, and some billions of years from now our distant descendants might like to travel to another star to restart our civilisation there. But if that star is already taken we might find this tricky. Maybe advanced civilisations will decide to start the colonisation rush sooner rather than later, so as not to be left out when the stars start dying.

Colin Robinson
2014-Nov-29, 05:40 AM
We can perhaps assume that a civilisation based in a single solar system will increase its use of resources towards a maximum, at which time the civilisation will achieve its greatest complexity and/or sophistication. With careful use of resources this level of sophistication could be maintained for a considerable period - at least while the star is on the main sequence. If the civilisation establishes a colony in a nearby system, that colony will in due course reach a similar level of resource use and sophistication.

But, as far as I can tell, this does not really double the complexity or sophistication of the civilisation, since thse two stars are so very far apart. Communications between the two systems will be very slow, taking years or decades to pass data back and forth. The civilisation may become more diverse, but it will also become more disjointed when considered as an interacting whole.

Perhaps that "disjointed" quality the relative independence of the two branches of the civilisation might be considered desirable?


Colonise an entire galaxy, and you will get a large and diverse set of colonies which are all at roughly the same level of sophistication, but which have extreme difficulty talking to each other.

I see the point, though presumably the difficulty of talking would be less extreme than the difficulty of talking with a biologically unrelated intelligence, as envisaged by SETI programs?


(Note that I am discounting any magical faster-than-light communication here, as there appears to be no realistic chance of that).

So is there any pressing need to colonise the rest of the galaxy? Maybe there is - but not to increase the resource use or complexity of their civilisation, but instead as insurance against the future. Eventually our star will die, and some billions of years from now our distant descendants might like to travel to another star to restart our civilisation there. But if that star is already taken we might find this tricky. Maybe advanced civilisations will decide to start the colonisation rush sooner rather than later, so as not to be left out when the stars start dying.

If that was the motive, logically the stars most likely to be colonised would be the most long-lived ones. I think someone suggested in another thread that this could be the reason our own solar system has not been colonised by extraterrestrials.

eburacum45
2014-Nov-29, 10:38 AM
That is an intriguing possibility. A civilisation that was planning to persist for a trillion years would prefer to colonise red dwarfs, since may of those stars will last that long, and will also get brighter over time.

However red dwarfs are also very dim, often much less than 10% as bright as a sun-like star; so the amount of complexity, diversity and sophistication that could be hosted by a red dwarf would presumably be lower. Here I'm modelling each solar system basically as an island universe, which a civilisation will develop to the greatest possible extent. Communications between these island universes will be almost insignificant compared to internal communications within the system, because of the light-speed delay factor.

It remains the case that a brighter, short-lived star will be capable of supporting an 'island unverse' of this type which is far more complex and diverse in the short-term than a red dwarf, which provides so much less energy to play with. Very bright, short-lived stars could support very complex but short-lived civilisations.

The problem comes when that star leaves the main sequence and explodes or collapses into a white dwarf or neutron star - which a bright star will do after a few million years. Would this brilliant but short-lived civilisation then cast around for other territory to annexe? Maybe they might move on to the next generation of short-lived stars, Herbig-Haro objects and so on that may be forming in nearby nebulae. Or they might use the massive resources of a collapsing or exploding star to power a wave of invasion craft.

I have heard suggestions that a black hole is very big inside, and capable of supporting a very large and complex set of processes - the so-called black hole computer.
http://www.dailygalaxy.com/my_weblog/2010/07/supermassive-black-hole-as-galactic-network-server.html
Maybe, just maybe, the collapse of a bright star into a black hole would be a desirable outcome for these bright, ephemeral civilisations.

Noclevername
2014-Nov-29, 11:00 AM
The problem comes when that star leaves the main sequence and explodes or collapses into a white dwarf or neutron star - which a bright star will do after a few million years. Would this brilliant but short-lived civilisation then cast around for other territory to annexe? Maybe they might move on to the next generation of short-lived stars, Herbig-Haro objects and so on that may be forming in nearby nebulae. Or they might use the massive resources of a collapsing or exploding star to power a wave of invasion craft.

White dwarf stars are pretty useful for a while. They can support small civilizations of a few billion beings all by themselves for longer than the lifetime of the present universe.

galacsi
2014-Nov-30, 10:23 AM
White dwarf stars are pretty useful for a while. They can support small civilizations of a few billion beings all by themselves for longer than the lifetime of the present universe.

Longer than the lifetime of the present universe ? Really ? I very much doubt that . You are not speaking of planets orbiting white dwarfs ? Because when these stars cool down and they cool down rather "fast" , the HZ will shrink;maybe you are thinking about habitats ?

Noclevername
2014-Nov-30, 10:43 AM
Longer than the lifetime of the present universe ? Really ? I very much doubt that . You are not speaking of planets orbiting white dwarfs ? Because when these stars cool down and they cool down rather "fast" , the HZ will shrink;maybe you are thinking about habitats ?

I said nothing of planets, I was speaking of usage of energy resources. And yes, the current crop of white dwarves are hot enough to be white because the universe has not been around long enough to let them cool down. See http://en.wikipedia.org/wiki/Black_dwarf.

eburacum45
2014-Nov-30, 04:18 PM
There are plenty of yellow-hot white dwarfs, a few orange-hot ones, but few that are red hot and none that are 'black'. White dwarfs do take many billions of years to cool down, and would be useful for extended periods. Each white dwarf could illuminate a 'ringworld' or a habitat swarm with a population much larger than the current population of the Earth, as Olaf Stapledon realised many decades ago.

Eventually, however, such a population would have to move elsewhere, or decline in number towards zero.

Noclevername
2014-Nov-30, 05:37 PM
There are plenty of yellow-hot white dwarfs, a few orange-hot ones, but few that are red hot and none that are 'black'.

I didn't know that there was such a variety, thanks.

galacsi
2014-Nov-30, 09:50 PM
I said nothing of planets, I was speaking of usage of energy resources. And yes, the current crop of white dwarves are hot enough to be white because the universe has not been around long enough to let them cool down. See http://en.wikipedia.org/wiki/Black_dwarf.

But you have to be cautious when you choose your white dwarf ,it must be in a very poor environment for dust and gas that can accrete onto the white dwarf. Because accretion means: x-rays.

eburacum45
2014-Nov-30, 10:57 PM
I didn't know that there was such a variety, thanks.
Well, it is a bit of a stretch, to be honest. The coolest white dwarfs are around 12 Gy old and 3700-3800K, which is at the top end of red dwarf temperatures.
http://cas.ou.edu/astronomer-and-colleagues-identify-12-billion-year-old-white-dwarf-star
This is, however, hotter than an incandescent light bulb. Remember them?

Noclevername
2014-Dec-01, 05:16 PM
This is, however, hotter than an incandescent light bulb. Remember them?

Hey, if it can bake a cake... :)

Noclevername
2014-Dec-01, 05:18 PM
The question is, would a star really be the most efficient energy source for an advanced civilization? For instance, starlifting hydrogen for fusion might make a better fuel source, and extend the life expectancy of the star in the process.

tuhaybey
2014-Dec-02, 05:52 AM
The only resource that I think it could be advantageous to mine from another solar system would be information. Anything else, the costs of transporting it back would seem to be many orders of magnitude greater than it's value could possibly be, but information you can transport back at light speed basically for free. In fact, the overall cost of harvesting information could be fairly low if you're willing to wait long enough for it. You could probably send very small, light, robots on a centuries long mission to collect information and transmit it back.

Obviously, the Earth isn't going to have scientific or technical knowledge that is of any value to a species that is capable of interstellar travel. It is hard to guess what sorts of information a much more advanced civilization would have an interest in, but perhaps our biodiversity is sufficiently rare that DNA sequences and whatnot are valuable.

eburacum45
2014-Dec-02, 05:04 PM
I agree. Information flows between colony systems could be very large. Since each colony will develop almost completely independently, they will have lots of cultural and historical information to convey, as well as any useful technological developments they might achieve. I'd expect that really surprising technology would start to plateau out, after a while; a community of roughly equal systems might not have all that much to teach each other after the first few million years, but I might be wide of the mark here.

Perhaps the really scary stuff they might keep to themselves, a prospect that is slightly disturbing. Millions or billions of highly advanced, roughly equal societies keeping secrets from each other sounds somewhat unstable.

Noclevername
2014-Dec-02, 08:43 PM
I think "sending back" resources is missing the point. The resources could be used where they are, by sending out generation ships or seeder ships to "civilize" the new systems, but interstellar shipping of bulk materials would not be a viable process for anything, perhaps other than those items or substances whose value exceeds a monetary economy; necessary for some purpose, but not present in significant amounts in the home system. And even then, sooner or later an advancing society could either learn how to make it themselves, or do without.

Jens
2014-Dec-03, 02:52 AM
I think "sending back" resources is missing the point. The resources could be used where they are, by sending out generation ships or seeder ships to "civilize" the new systems, but interstellar shipping of bulk materials would not be a viable process for anything, perhaps other than those items or substances whose value exceeds a monetary economy; necessary for some purpose, but not present in significant amounts in the home system. And even then, sooner or later an advancing society could either learn how to make it themselves, or do without.

In that case, though, I'm not sure about what the original question was. It said "resource use as a motive," but in this case you are just saying colonization for whatever reason, i.e. to spread ourselves and have the resources to support those new populations. That seems like a fairly clear issue: if you are going to colonize, of course you need the resources to support the colonists...

The original post began by talking about the Spaniards bringing gold back to Spain.

Colin Robinson
2014-Dec-03, 03:41 AM
In that case, though, I'm not sure about what the original question was. It said "resource use as a motive,"

It seems to me that use of physical resources is use of physical resources, whether or not you bring them home before you use it.


The original post began by talking about the Spaniards bringing gold back to Spain.

That was meant as an example of one way of using resources. Another example would be when a swarm of locusts migrates to a new area. They do so in order to use physical resources (things to eat). But they don't bring the food back where they came from, they eat it on the spot.


but in this case you are just saying colonization for whatever reason, i.e. to spread ourselves and have the resources to support those new populations. That seems like a fairly clear issue: if you are going to colonize, of course you need the resources to support the colonists...

True, but the pace and the methods of colonisation will be different if the motive is something other that use of physical resources. E.g. if the motive is to set up a research base to gather information.

kzb
2014-Dec-03, 12:34 PM
GOLD is not really a resource. It's not much practical use for anything. Nevertheless it was the prime motivation behind the conquistadors and probably many other invasions.

ETs might have no clue that humans value gold. Maybe ET values something that we can't imagine the reason for.

The resource issue is important, because there are likely very few if any planets that are precisely in our comfort zone (of gravity, temperature, illumination etc). Just imagine if there is one such ET race on an Earth twin many LY away, but their sun is evolving so the planet is becoming uninhabitable.

There is only ONE twin planet within any plausible transport range, and that is Earth. The planet as a home for large populations is its "valuable resource", and it could be worth fighting over.

Noclevername
2014-Dec-03, 01:43 PM
GOLD is not really a resource. It's not much practical use for anything. Nevertheless it was the prime motivation behind the conquistadors and probably many other invasions.

ETs might have no clue that humans value gold. Maybe ET values something that we can't imagine the reason for.

The resource issue is important, because there are likely very few if any planets that are precisely in our comfort zone (of gravity, temperature, illumination etc). Just imagine if there is one such ET race on an Earth twin many LY away, but their sun is evolving so the planet is becoming uninhabitable.

There is only ONE twin planet within any plausible transport range, and that is Earth. The planet as a home for large populations is its "valuable resource", and it could be worth fighting over.

An extremely implausible scenario. If any ET civilization can travel between the stars, then they have mastered methods for staying in space without planets. Also, they would have our native ecology to contend with.

IsaacKuo
2014-Dec-03, 03:00 PM
When it comes to long lived power sources, nothing beats a black hole. There are various mechanisms for sacrificing matter into black holes for energy, and they are all vastly superior to stellar fusion because:

1) You get far more energy per kg of "fuel"
2) You can throttle the process, turning on and off the power like a tap - anywhere from zero power consumption to power levels greater than a supernova
3) You can use ANY matter for fuel, not just fusionable isotopes
4) You can conveniently refuel as long as the galaxy exists, deflecting anything that passes nearby into orbit (this requires very little energy and delta-v, thanks to the Oberth effect and the black hole's deep gravity well)

Basically, a black hole system is far more desirable than any star system if energy and power are what you care about. You don't even need any megastructures to efficiently utilize the power available. For example, you could simply use geothermal energy in a small asteroid in an elliptical orbit. Periodically, you build a small sacrificial impactor drone and launch it into a retrograde orbit at apoapsis. Then you dig a deep hole for the impactor to enter at periapsis. It impacts at nearly the speed of light, causing the equivalent of a large underground nuclear explosion--to keep the asteroid's core molten and hot.

You can scale up this approach by having two contra-orbiting rings of asteroids--one with an orbit slightly inside the other. They lob impactor drones at each other, as desired, to keep up core heat. Each asteroid is essentially its own tiny Dyson sphere, that's only a ~100km in diameter.

The only "problem" with these black hole systems is that we'd find them pretty much impossible to spot. Unlike a Dyson Sphere, they can be throttled down to any desired level...if longevity is the goal, then these may be dialed down to practically nothing. That means practically no waste heat emissions for us to spot. (In contrast, a Dyson sphere would emit as much as a red giant.) Really, the only way for us to spot them would be sheer luck of gravitational microlensing. Even then, there's no way for us to distinguish the system from an uninhabited black hole system.

primummobile
2014-Dec-03, 04:28 PM
GOLD is not really a resource. It's not much practical use for anything. Nevertheless it was the prime motivation behind the conquistadors and probably many other invasions.

ETs might have no clue that humans value gold. Maybe ET values something that we can't imagine the reason for.

The resource issue is important, because there are likely very few if any planets that are precisely in our comfort zone (of gravity, temperature, illumination etc). Just imagine if there is one such ET race on an Earth twin many LY away, but their sun is evolving so the planet is becoming uninhabitable.

There is only ONE twin planet within any plausible transport range, and that is Earth. The planet as a home for large populations is its "valuable resource", and it could be worth fighting over.

Gold has plenty of uses, especially in electronics. The only reason your computer doesn't have thousands of dollars of gold in it is that it would cost thousands of dollars. Gold is an excellent conductor and it doesn't corrode like copper and silver do.

Jens
2014-Dec-03, 10:31 PM
It seems to me that use of physical resources is use of physical resources, whether or not you bring them home before you use it.



Well, if you are going to use it on-site, I'm not sure how that differs from an expansion to get real estate.

Noclevername
2014-Dec-03, 11:31 PM
Well, if you are going to use it on-site, I'm not sure how that differs from an expansion to get real estate.

Expansion to get real estate is a use of resources, isn't it??

Colin Robinson
2014-Dec-04, 12:03 AM
Well, if you are going to use it on-site, I'm not sure how that differs from an expansion to get real estate.

The question is what makes a particular bit of "real estate" desirable to a particular person or group? For instance, the western and northern coasts of Australia were sighted and charted by European seafarers through the seventeenth century (beginning 1606). Did they immediately say: "Ah, real estate!" and start setting up colonies? Not at all. No European country tried to colonise Australia until 1788...

KABOOM
2014-Dec-04, 04:58 PM
When it comes to long lived power sources, nothing beats a black hole. There are various mechanisms for sacrificing matter into black holes for energy, and they are all vastly superior to stellar fusion because:

1) You get far more energy per kg of "fuel"
2) You can throttle the process, turning on and off the power like a tap - anywhere from zero power consumption to power levels greater than a supernova
3) You can use ANY matter for fuel, not just fusionable isotopes
4) You can conveniently refuel as long as the galaxy exists, deflecting anything that passes nearby into orbit (this requires very little energy and delta-v, thanks to the Oberth effect and the black hole's deep gravity well)

Basically, a black hole system is far more desirable than any star system if energy and power are what you care about. You don't even need any megastructures to efficiently utilize the power available. For example, you could simply use geothermal energy in a small asteroid in an elliptical orbit. Periodically, you build a small sacrificial impactor drone and launch it into a retrograde orbit at apoapsis. Then you dig a deep hole for the impactor to enter at periapsis. It impacts at nearly the speed of light, causing the equivalent of a large underground nuclear explosion--to keep the asteroid's core molten and hot.

You can scale up this approach by having two contra-orbiting rings of asteroids--one with an orbit slightly inside the other. They lob impactor drones at each other, as desired, to keep up core heat. Each asteroid is essentially its own tiny Dyson sphere, that's only a ~100km in diameter.

The only "problem" with these black hole systems is that we'd find them pretty much impossible to spot. Unlike a Dyson Sphere, they can be throttled down to any desired level...if longevity is the goal, then these may be dialed down to practically nothing. That means practically no waste heat emissions for us to spot. (In contrast, a Dyson sphere would emit as much as a red giant.) Really, the only way for us to spot them would be sheer luck of gravitational microlensing. Even then, there's no way for us to distinguish the system from an uninhabited black hole system.

But if the energy/power could only really be used in situ, would it be feasible to establish a "space colony" in a proximity close enough to the black hole that could still use the energy but not survive long term? I had thought that any proximities to close to a black hole would be very hostile to a space colony.

IsaacKuo
2014-Dec-04, 06:11 PM
But if the energy/power could only really be used in situ, would it be feasible to establish a "space colony" in a proximity close enough to the black hole that could still use the energy but not survive long term? I had thought that any proximities to close to a black hole would be very hostile to a space colony.
There isn't anything particularly hostile about being close to a black hole lacking an accretion disc (an accretion disc forms when a black hole is sucking up matter from a close stellar companion).

Even so, a "space colony" might want some distance because of the risk of a runaway accident. The suggested contra-orbiting asteroids could suffer a relativistic Kessler Syndrome disaster--rapidly producing a cascade of relativistic impactors in a dangerous torus around their former orbits. As such, it may be desirable to site a "space colony" at a much higher orbit.

The asteroids can beam energy to the "space colony" with long range laser or microwave beam.

Such an accident would be a freak occurrence, and wouldn't last very long. Those impactors, zooming around at relativistic speeds, would soon collide with something and convert themselves into thin plasma that disperses (mostly gets lost to the black hole). The asteroid system could then be replaced with a backup in higher orbit.

Solfe
2014-Dec-05, 06:27 AM
What if the reverse was true, that a species expanded due to the abundance of certain resources? Suppose you had a lot of materials for nuclear power, ready metals for spacecraft, excellent resources for power storage plus a massive population problem?

Time to conqueror/explore.

Noclevername
2014-Dec-05, 07:10 AM
What if the reverse was true, that a species expanded due to the abundance of certain resources? Suppose you had a lot of materials for nuclear power, ready metals for spacecraft, excellent resources for power storage plus a massive population problem?

Time to conqueror/explore.

That might justify system-wide expansion, but interstellar is not going to be affected. Starships would be far too resource-intensive and energy expensive to solve overpopulation.

Noclevername
2015-Feb-22, 09:01 AM
The question is what makes a particular bit of "real estate" desirable to a particular person or group? For instance, the western and northern coasts of Australia were sighted and charted by European seafarers through the seventeenth century (beginning 1606). Did they immediately say: "Ah, real estate!" and start setting up colonies? Not at all. No European country tried to colonise Australia until 1788...

Probably ecause they already had real estate at home.

I doubt European colonization of foreign lands is a viable comparison to either expansion into space from a planet, or interstellar expansion. The OP mentions Spanish gold but that kind of bulk trading between stars is just never going to happen; the distances and technological hurdles and energy requirements are far too massive for such commerce to pay. Any interstellar expansion of a species will have to be driven by other motives.