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> But unfettered growth isn't sustainable, this has been proved again and again. This is vague, and assumes the conclusion. All we've ever known is unfettered

> But unfettered growth isn't sustainable, this has been proved again and again. This is vague, and assumes the conclusion. All we've ever known is unfettered growth, and it's been accompanied by people "proving" that it's "not sustainable" for a long time. So far we have not only sustained it, but thrived while sustaining it. More importantly, we have come to rely on it: We're pretty sure we couldn't have a society like this one without hundreds of millions of people.

tzs 5y ago
Any given growth rate is not sustainable long term. For example, consider a growth rate of 1% per year (about what the world population growth rate currently is). Right now, every human is on or near the Earth. Let's call this year 0. In year 1, every human must be within one light-year of the Earth. In year 2, every human must be within two light-years of the Earth. In year N, every human must be within N light-years of Earth. Take the volume of a sphere of radius N light-years and divide it by the population after N years of 1% growth, and you get the volume available per person if humans were spread out evenly among all possible space that humans could theoretically occupy. At year 1, that is about 4.39 x 10^38 m^3 per person, so no problem. But at around year 11600 it is 4 m^2 per person. By 12101 it is down to 0.04 m^3 per person. The internet tells me that the average volume of a human is about 0.06 m^3 so 0.04 m^3 per person would be bad news. What if we manage to invent Star Trek style warp engines right away, which let us go 1000x the speed of light. That makes everything a 10^9 times better. At 12101 we have 40000000 m^3 per person. But by 13524 we are down to 40 m^3 per person, and by 14000 below 0.39 m^3 per person. From there we have only got until 14192 before we are just below 0.06 m^3. Remember, this is being ridiculous optimistic. Even with warp drive available starting tomorrow we would not be able to spread so fast that 14000 years from now we are uniformly occupying a 28000 light year diameter spherical volume around Earth. In reality we'll hit a space limit a lot earlier. Hence, we can conclude that 1% is not sustainable for more than a few thousand years even under very optimistic assumptions. Long term the growth rate must be one that on average declines over time, simply because a growth rate that does not do so leads to exponential growth, but we live in a universe were accessible space cannot grow faster than polynomially.

tzs 5y ago

Any given growth rate is not sustainable long term. For example, consider a growth rate of 1% per year (about what the world population growth rate currently is). Right now, every human is on or near the Earth. Let's call this year 0. In year 1, every human must be within one light-year of the Earth. In year 2, every human must be within two light-years of the Earth. In year N, every human must be within N light-years of Earth. Take the volume of a sphere of radius N light-years and divide it by the population after N years of 1% growth, and you get the volume available per person if humans were spread out evenly among all possible space that humans could theoretically occupy. At year 1, that is about 4.39 x 10^38 m^3 per person, so no problem. But at around year 11600 it is 4 m^2 per person. By 12101 it is down to 0.04 m^3 per person. The internet tells me that the average volume of a human is about 0.06 m^3 so 0.04 m^3 per person would be bad news. What if we manage to invent Star Trek style warp engines right away, which let us go 1000x the speed of light. That makes everything a 10^9 times better. At 12101 we have 40000000 m^3 per person. But by 13524 we are down to 40 m^3 per person, and by 14000 below 0.39 m^3 per person. From there we have only got until 14192 before we are just below 0.06 m^3. Remember, this is being ridiculous optimistic. Even with warp drive available starting tomorrow we would not be able to spread so fast that 14000 years from now we are uniformly occupying a 28000 light year diameter spherical volume around Earth. In reality we'll hit a space limit a lot earlier. Hence, we can conclude that 1% is not sustainable for more than a few thousand years even under very optimistic assumptions. Long term the growth rate must be one that on average declines over time, simply because a growth rate that does not do so leads to exponential growth, but we live in a universe were accessible space cannot grow faster than polynomially.