A 2.3% growth in population for 1400 years would lead to a population of around 4.6*10^23 people. This has nothing to do with reality - the rate of population growth is decreasing and will continue to decrease as countries get more prosperous. The increase in economic output taking place right now goes both towards making people richer and supporting the increase in population. If population levels off, even at some ridiculous level like 50 billion (which it won't), there is absolutely no argument for 2.3% growth extrapolated anywhere near that amount of time into the future without some sort of change in economic paradigm.

The math is fine, the assumptions that undergird that math are terrible. You can see that in a lot of his blog posts. There's another [0] that argues that economic exploitation of space doesn't make sense because it is impractical to ship large numbers of people offworld - which is true, and supported by mathematics and physics, but barely touches (if at all) on things like space-based solar power generation and asteroid mining, neither of which depends on shipping large numbers of people offworld, as colonization presumably does.

http://physics.ucsd.edu/do-the-math/2011/10/why-not-space/

The 2.3% figure applies to economic growth, not population growth. The blog argues that our economy relies on energy. In the next 1400 years, our supply of energy must inevitably plateau. Therefore, the economy's growth has an upper bound.

I was using the blog as evidence to support my argument. My argument was that once we hit the economic plateau, our quality of living will decrease if the population continues to increase. Therefore, perhaps eugenics (a la China's one-child policy) won't sound like such a bad idea in the future.

> but barely touches (if at all) on things like space-based solar power generation and asteroid mining

Again, he covers this in his first post via reductio ad absurdum:

> Let’s think big: surround the sun with solar panels. And while we’re at it, let’s again make them 100% efficient. Never-mind the fact that a 4 mm-thick structure surrounding the sun at the distance of Earth’s orbit would require one Earth’s worth of materials—and specialized materials at that. Doing so allows us to continue 2.3% annual energy growth for 1350 years from the present time.

> My argument was that once we hit the economic plateau, our quality of living will decrease if the population continues to increase.

This is totally irrelevant because (as I said) population growth is slowing down and the population is almost certainly not going to continue to increase forever. It's forecast that human population will max out late this century due to declining birthrates in countries that are growing wealthier; hitting the theoretical limits (e.g. max solar output) before then is so implausible it's barely worth discussing.

> Again, he covers this in his first post via reductio ad absurdum:

His assertion that SSP (and everything else) is impractical for sustaining 2% growth for a millennium is true, but practically irrelevant. Space-based exploitation can increase the plateau cap, allowing for higher standards of living for a future populace whose population is level or declining.

I hate to come off as anti-intellectual, but science is bound by the burden of proof and has no capacity to account for human ingenuity or dramatically different models of consumption, production and growth. Yet history shows we can expect precisely these kinds of changes, every time.

There is lots of writing and historical context for how Malthus and his theories influenced the day of the potato famine, google around for it and draw your own conclusions.

"but science is bound by the burden of proof"

... to prove what exactly? That humanity will inevitably overcome the issues which overpopulation begets? That our population will plateau before we reach 250 billion if we close the gender gap? I feel like your comment was really vague, and you answered jrs99's question somewhat obliquely. So I don't know what you're arguing. But if your Amazon link is anything to go by, I assume you predict a decrease in the world's population.

Also, I don't think we can continue to extrapolate history as you imply. I used to think that our age was no different than any other age. I used to think "Humans have always had the same needs, right? Technology simply gives us more effective ways to satisfy them. Technology changes, but Humanity's needs have stayed relatively consistent."

Randell Munroe's project "Time" changed my opinion. To roughly paraphrase, "Whatever civilization comes next won't have fossil fuels to jump-start another industrial revolution." And I began thinking "Huh... I guess that makes sense. Fossil Fuels make us pretty unique, doesn't it? There's a pretty low probability that we'll find an energy source more dense and convenient than Fossil Fuel. Things like solar and fission are certainly nice. But if they packed the punch that Fossil Fuels did, they'd have dominated our economy already! So does Fossil Fuel represent a limiting reagent (chemistry term) on what Humanity can achieve?"

I think you and the astrophysicist can agree that something has to give. And perhaps closing the gender gap will plateau the population before we reach 250 bil. But given this fails and the population reaches 250 bil and we live in dystopia anyways (like jrs99 originally asked), do you still believe that eugenics are inherently immoral?

[I'll take up that offer and start reading up on the famine.]

I guess I am being vague, because my argument distills down to simple optimism vs. pessimism. I can't argue what is not known. We don't know what tomorrow's energy sources will look like. We don't know how to sustain two, five or ten times the population, let alone the exponential growth we've witnessed. Of course something has to give, and it will. Fossil fuels are unique, sure. And of course they are limited.

But imagine how limited people felt in the 1700s when their entire energy and food supply was simply the sun and arable land. I bet that felt rather absolute to them too. I mean, it's the sun. It's pretty fundamental and unchanging. What else could there be? Surely we can do the math on how much farmland there is to work and calculate possible yields and determine the maximum number of humans the planet can sustain. And what should be done with that number?

Yet centuries later we have shattered those limitations many times over, doubling and doubling and doubling the population again.

I don't mean to belabour the point, maybe we will transcend our current limitations (I think we will), or maybe we won't. But even if we don't, let resource scarcity cull and control population instead of policy.

The crux of the astrophysicist's argument lies in thermodynamics. Given the economic track we're on, the demand for energy will equal the entire output of the sun. Not merely the output of the sun that the earth's surface can capture, but 360 degrees' worth of electromagnetic radiation at 100% conversion efficiency.

I too recently thought that humanity probably overcome whatever problems the universe throws. But I don't see how humanity plans to "transcend" the laws of thermodynamics. The least far fetched idea I can think of is antimatter. But handling a substance that volatile somehow seems to me like a very bad idea.

You seem to be appealing to this notion that "There's so much about the universe we still don't know. What the future looks like is beyond our wildest imaginations."

http://chem.tufts.edu/answersinscience/relativityofwrong.htm

Above is Isaac Asimov's essay The Relativity of Wrong. In a nutshell, an English teacher had expressed disapproval at Asimov's arrogance when he "had expressed a certain gladness at living in a century in which we finally got the basis of the universe straight." To which Asimov responded "[that the teacher] may be imagining that because all theories are wrong, the earth may be thought spherical now, but cubical next century, and a hollow icosahedron the next, and a doughnut shape the one after."

Humanity doesn't know everything. And maybe we never will. But at this point, we're pretty confident that we've gotten down the basics . I.e. Relativity may have replaced Newtonian Physics, but Newtonian Physics wasn't outright invalidated for everyday velocities. By and large, our scientific body of knowledge is logically monotonic. We'll augment our models, we'll refine our models, but it's unlikely we'll ever say, "Newtonian physics is, and always has been dead wrong. We have to start physics from scratch."

> But even if we don't, let resource scarcity cull and control population instead of policy.

And this is a different issue altogether, concerning ethics. As I said before, I think birth control policy is the better of 2 evils. The other evil being warfare resulting from abject poverty. Such policies would prevent a lot of needless pain and suffering. I'd rather live in happier world with less people than in a sadder world with lots of people. It's not like those unborn will mind, because they won't exist.

But maybe you think the parents will mind, or believe in the efficacy of natural selection. Our stances remind me of The Giver/Gathering Blue.