Tidal energy is not renewable

The first time I'd run into the notion that high metabolic systems burn out faster was reading Asimov's book on black holes, The Collapsing Universe, when I was a young boy, and learning that the hotter and brighter a star, the shorter its life. The very largest known star, CY Canis Majoris, is a red supergiant, near the end of its life, and is thought to have formed 8.2 Mya, roughly the same time h. sapiens and chimpanzees diverged on the evolutionary tree. Contrast the birth of our own Sun at about 4.5 Bya.

The notion that human civilisations might be somewhat akin to stars, burning through their metabolic and resource foundations, has a symmetry to this concept, though there are more confounding factors to cultures than there are to starts, where metallicity, mass, and the presence or absence of stellar companions are about the only relevant factors affecting lifespan.

The idea that civilisations are bounded by limits and that growth only reaches those limits more quickly also punches some gaping holes in the notion of long-termism, which argues for maximal growth and growth rates. That makes sense if ultimate growth and all stages along the pathway are both unlimited. If, however, there are both local and global maxima, that is, ceilings to growth and sustainability, and most especially if reaching those limits is a high-risk event, then rather than argue for maximal growth at all times, a more reserved approach is called for.

The question of two species or cultures competing for the same resources is another point, and it's been raised several times in this thread. I'd look to actual ecosystems where fast- and slow-growing species (including r/K selection theory: https://en.wikipedia.org/wiki/R/K_selection_theory>) exist. If the slower-growing species is also the more resilient for other reasons, then its slow growth need not be an ultimate handicap. That of course isn't a given, but depends very much on both the fitness landscape (selective pressure) and specific species adaptations. Human cultures are not identical to biological species, though they share some resemblances. Most especially, cultures are malleable, individuals can move between cultures, and the practices and knowledge of cultures can be shared, adopted, and transmitted to a much greater extent than biological species' genetic code is.

(I'd also like to make as painfully clear as I can that I am NOT equating "human culture" with any specific ethnic or geneological line, but rather the knowledge, practices, language, geographical distribution, and activities of groups of people, whether of common or diverse ancestry. Rather I'm focusing on both as persistent patterns which share the characteristics of inheritance, variability, and selection, and are thus evolutionary phenomena.)

As discussed in another comment, alliances matter far more for cultural protection than measures of wealth (collective or per-capita GDP, say): https://news.ycombinator.com/item?id=37400918>.

I'm not saying that national capability as expressed in defensive capabilities doesn't matter at all, but suggest that it matters far less than one might generally think. Even at times where marauding empires were fashionable, the empires they created rarely survived long: Alexander, Rome, Napoleon, and Hitler all made tremendous conquests, but in three of those four instances, lost control within a few years, decades at the outside. Rome itself held at maximum extent with no peer in capabilities for a few centuries.

Common interest and fraternal bonds seem far more effective than military might. Certainly less costly. And one could argue that both Pax Romana and Pax Americana were based more on economic than military factors.

On the 2nd and 3rd points: Certain forms of growth, most especially those based on fossil fuels, must end in the very near future to avoid absolute catastrophe. The political and economic opposition to this remains strong, unfortunately. As for channeling growth into basic infrastructure and safety nets, amen!

Glad you're getting something from this.

You're making a different argument now, probably without realizing. The original blog post starts by saying:

> I said to him, “economic growth cannot continue indefinitely,” just to see where things would go.

Re-reading the blog post I see that it's very confusing, because the physicist isn't retelling the story clearly and probably not thinking about his argument clearly. He uses the word "exponential" in the title of the blog post, but then his recounting of how the discussion begins doesn't involve that. The first time it comes up in his retelling, it's when the physicist starts conflating wealth with energy. So whilst you are talking about exponents they appear to be irrelevant to the argument.

Phrased another way, for as long as humanity can somehow improve its collective situation in some way the economy can grow.

But even if the economist had tried to defend unlimited exponential growth, it would only affect the time window within which economic claims are valid. Remember that we're talking about wealth, which isn't dependent on physical limits. There's no theoretical upper limit to wealth just like there's no theoretical upper limit to how big numbers can get. Or rather, to argue that there is a limit, you have to start making complex and highly speculative arguments about hypothetical limits to human ingenuity, potential and preferences which is why the counter-argument goes in the direction of talking about the Matrix.

Let's put that to one side. Just like the physics guy in the article you clearly think you're winning some meaningful points here, but you aren't. Like most fields of study, economics is the study of worlds that roughly resemble our own. This is so obvious that it doesn't normally need to be stated explicitly. Perhaps it's not obvious to people who research physics due to the unusually universal nature of physical claims. So the statements it makes are grounded in a set of axioms and contexts, one of which is when they say there are no limits to wealth they mean in practice, for a world and society somewhat like this one.

That's why to argue against this point you have to keep bringing up wholly theoretical societies, where we reached the limits of the universe or became brains-in-jars. If you want to talk about the economics of the Matrix then great! Go for it! It will make for intriguing science fiction, but not more. It is A-OK if our current definitions of terms like wealth and growth fail for hard sci-fi worlds.

No I haven't. Actually I said the opposite, and I will reassert it here: growth and energy usage doesn't need to be decoupled in any way, for China to actually export energy. Export is appearing on both sides of the equation: on the GPD side, and on the energy consumption side.

Of course we want to get into the details. I can see there are many reasons why the earth maybe releasing more than it absorbs.