[Space] The Galactic Empire according to GURPS Space

[Daigoro]

In any case, you're giving everyone thousands of years to spread out across the galaxy, so you're looking at the end state of having the galaxy's easily settleable garden world's all sitting near capacity, aren't you? Population growth rates are only going to be a local issue after somewhere has taken a hit from a meme-plague, nanoswarm attack or nova bomb.

[AlexanderHowl]

Such high growth rates are dependent on having an Affinity 10 (the multiplier is equal to Affinity), having a cultural need for children (children in an agrarian society are workers, children in a post-industrial society are expensive), and a positive trade balance for importing medical technology. Even on Earth, we have never had a global ×10 increase, the largest increase was 1900-2000, which had the global population increasing from 1.7 billion to 6.8 billion, which was only a 4x increase. The rapid population 'growth' in the Americas occurred because colonists stole developed agrarian land by enslaving and murdering disease stricken Native Americans, and any space colonies are unlikely to benefit from such circumstances.

[David Johnston2]

Originally Posted by AlexanderHowl

At TL8, half of the nations on the Earth have negative growth rates before accounting for immigration and immigrants quickly reduce their reproduction rates after a generation. At TL10, a society might have only a 0.1% growth rate even with incentives and technology, meaning that it would take 720 years to double the population. In that case, a planet colonized 7,200 years ago with 1 million colonists might only have a population of 1 billion.

GURPS Space tends to assume that usually happens when a planet reaches carrying capacity. Which means that since Garden Worlds rarely hit an affinity of 10 the typical population in the galaxy that has been filled for 10,000 years would be under five billion. The most likely asteroid civilizations would be the ones that actually in the same system as a Garden world with a positive RVM. Ironically easy interstellar travel actually discourages the development of asteroid belts that aren't in Garden World systems, because the Garden Worlds take so much less effort to colonize. When they do colonize asteroid belts outside of a Garden World it's because the system is a Motherlode (rolled 18 for RVM) and there is no closer Motherlode to the GW. A Motherlode always has a carrying capacity of five billion (assuming no increase from TL 10). The best possible human CC for a Garden World is about 22 billion but it would be rare to actually reach that population density without screwing up the ecology and lowering the CC. A more typical Garden world would have an affinity of 7 and a CC of 2.6 billion.

[Rupert]

Originally Posted by AlexanderHowl

Such high growth rates are dependent on having an Affinity 10 (the multiplier is equal to Affinity), having a cultural need for children (children in an agrarian society are workers, children in a post-industrial society are expensive), and a positive trade balance for importing medical technology. Even on Earth, we have never had a global ×10 increase, the largest increase was 1900-2000, which had the global population increasing from 1.7 billion to 6.8 billion, which was only a 4x increase. The rapid population 'growth' in the Americas occurred because colonists stole developed agrarian land by enslaving and murdering disease stricken Native Americans, and any space colonies are unlikely to benefit from such circumstances.

Affinity doesn't change growth rate in Space at all. It changes the initial colony size by x10 per +3 Affinity (roughly), and carrying capacity roughly doubles per +1 Affinity.

Note that Space does not discuss where the growth of a colony comes from (natural reproduction, immigration, mass production of people via growth tanks, etc.), it just assumes that colonies grow in size with age.

[Michael Thayne]

Originally Posted by AlexanderHowl

Such high growth rates are dependent on having an Affinity 10 (the multiplier is equal to Affinity), having a cultural need for children (children in an agrarian society are workers, children in a post-industrial society are expensive), and a positive trade balance for importing medical technology. Even on Earth, we have never had a global ×10 increase, the largest increase was 1900-2000, which had the global population increasing from 1.7 billion to 6.8 billion, which was only a 4x increase. The rapid population 'growth' in the Americas occurred because colonists stole developed agrarian land by enslaving and murdering disease stricken Native Americans, and any space colonies are unlikely to benefit from such circumstances.

The point about the land in the Americas already having been developed for agriculture by Native Americans is a good one. Do we have any hard data on how long that kind of thing takes? Maybe development of the Amazon for agriculture would be a useful precedent to look at, but I think a lot of the natives in that region are horticulturalists, and I don't know if converting land used for horticulture to agriculture is easier than establishing agriculture on truly undeveloped land. Also, getting agriculture going on an alien planet, even one relatively friendly to human life, might not be at all straightforward.

[ericthered]

Originally Posted by Michael Thayne

The point about the land in the Americas already having been developed for agriculture by Native Americans is a good one. Do we have any hard data on how long that kind of thing takes? Maybe development of the Amazon for agriculture would be a useful precedent to look at, but I think a lot of the natives in that region are horticulturalists, and I don't know if converting land used for horticulture to agriculture is easier than establishing agriculture on truly undeveloped land. Also, getting agriculture going on an alien planet, even one relatively friendly to human life, might not be at all straightforward.

Its also a nuanced one. The great plains were managed but largely unfarmed by the Amerindians, and by the time the east coast was settled, the forests east of the appalachians had taken over much of the former farmland. The great plagues that first decimated the natives in the 1500's and 1600's were a long time before the push west in the late 1700's and early 1800's. It is my observation that forest converts quite nicely to farmland. at least for the first decade or so. Fertilizer solves that issue though.



How difficult it is to farm an alien planet is a great point, but its ultimately a setting decision.

[Fred Brackin]

Originally Posted by Michael Thayne

Th? Maybe development of the Amazon for agriculture would be a useful precedent to look at,

That precedent would show that it was a dumb idea. The US Midwest prairies with topsoil 6 inches deep only needed good plows. Clear out a tropical rainforest and you'll discover virtually no topsoil at all.

So any estimate of "planetary carrying capacity" that includes turning rainforests into grain fields is flawed from the start.

One of the main reasons to leave Earth and other highly developed planets would be to get away from what was percieved as "too many people". That sort of imigration would dry up after a planet hit whatever would be percived as the "too many" level.

I tend to assume colony populations far below any figure of multiple billions. Probablya t least one full order of magnitude and possibly more than that.

[Michael Thayne]

Originally Posted by Fred Brackin

That precedent would show that it was a dumb idea. The US Midwest prairies with topsoil 6 inches deep only needed good plows. Clear out a tropical rainforest and you'll discover virtually no topsoil at all.

So any estimate of "planetary carrying capacity" that includes turning rainforests into grain fields is flawed from the start.

One of the main reasons to leave Earth and other highly developed planets would be to get away from what was percieved as "too many people". That sort of imigration would dry up after a planet hit whatever would be percived as the "too many" level.

I tend to assume colony populations far below any figure of multiple billions. Probablya t least one full order of magnitude and possibly more than that.

Now I'm wondering about shipping topsoil to new colony worlds. I don't really know anything about agriculture, but as far as I can tell from Googling topsoil is basically just a mixture of sand, silt, clay, and compost, and is already available for purchase in bulk. (Maybe such commercially available mixtures are inferior to "natural" topsoil somehow, but I don't know why that would be true.) How much soil do you need for a colony? Google suggests one acre is about the right amount of land to feed one person. By my math a thousand tons of topsoil should be more than enough to cover one acre. And with space elevators, drop cans, and inexpensive FTL, you should be able to deliver that topsoil to a planet's surface for under $250 per ton, including the cost of the soil itself. So that adds $250k to your colony startup costs.

Even if the total cost per colonist of setting up a space colony is $1M, that might seem relatively affordable with TL11 per capita wealth, especially if it lets people get away from overpopulated already-colonized worlds, and they hope to get rich off the vast untapped natural resources of unsettled garden worlds.

[Rupert]

Originally Posted by Michael Thayne

Now I'm wondering about shipping topsoil to new colony worlds. I don't really know anything about agriculture, but as far as I can tell from Googling topsoil is basically just a mixture of sand, silt, clay, and compost, and is already available for purchase in bulk. (Maybe such commercially available mixtures are inferior to "natural" topsoil somehow, but I don't know why that would be true.)

Viable topsoil for a new colony would need to include the biota that normal live within topsoil - soil bacteria, fungi, earthworms, and so on.

[David Johnston2]

As to the issue of the number of occupied systems in such a setting, there are maybe 400 billion stars in the galaxy as a whole (although more than half of them would be in multiple star systems). But I've done enough dice rolling that I'd be comfortable saying that for a culture with easy transgalactic travel 999 out of a 1000 stars would be classed as "not worth bothering with".