Physicist Tom Murphy says he argued with “an established economics professor from a prestigious institution,” on whether economic growth can continue forever. They both agreed to assume Earth-bound economies, and quickly also agreed that total energy usage must reach an upper bound within centuries, because of Earth’s limited ability to discard waste heat via radiation.
the physicist is right when talking about numbers, as usual. Later in his article he concedes much ground and only allows himself to say "Will [growth] be at the 2% per year level (factor of ten better every 100 years)? I doubt that." Which is really much more of a concession then the economist ever made during the conversation. Of course, due to his typical ivy league physicist ego, he was still absolutely stunned at how much more right he was than the economist.
I had such a strong initial reaction to this post and was so sure I must be right. So I did something reasonable: I read the source post of the discussion.
It supported in spades my initial reaction. I HAVE learned something over time, and I suspect that Robin and any serious reader of this blog falls on the same side of this.
The physicist is right. The problem isn't in the details, either. It is in the difference between a fuzzy concept of infinity (or forever as they name it here) and an actual concept of forever.
Before reading Robin's blog I did think that humanity's future was rosy, that Malthus was horribly misinformed by living before modern times. Since reading this blog, it seems more likely that we have had a really good few centuries that actually pushed productivity out in front of population pressure. But absent some kind of biological innovation we have never yet seen the likes of, the slow but steady exponential of biological growth will eventually regain on the episodic-but-ultimately-non-exponential growth of a finite universe.
Infinity is non-physical, non-real. If there is ANY example of an argument where, in a mathematical sense, inifinity is the right answer, I have not yet seen it. You can, I think, be assured a good living if you can find money bets against infinity and without further thought always take the side against infinity.
My favorite finite fact in the discussion was that if energy use on earth continues growing at 3%/year, the average surface temperature of the earth is boiling point in 2500 years. So maybe we devote certain parts of the earth to glowing at 10,000 C so the rest of earth can be kept at 23C or so, but what does that gain us, a factor of 3? 10? 1000? It certainly doesn't gain us a factor of infinity. Whether 100 C average surface temperature is the limit or we are clever and get past that, the actual limit is some finite multiple of that.
There are only 10^70 particles in the universe. 10^71 is 10X the actual universe. 10^100 is insanely larger than the actual universe. 10^1000, 10^100^100? Or as less wrong likes to fantasize 3^^^3? No matter how you wind up counting it, finity is GIGANTICALLY LESS than infinity no matter how big you make finity. And Infinity is Bullshit. (Robin, that looks like a good post title for you.)
We will find solutions and substitutes around our major problems. Just take a look at this bet: http://en.wikipedia.org/wik...
Put me down as being in the camp that says "I welcome the day the sun burns out, because man kind will have created its own sun long before it."
Even the linear growth of space colonization is more than Murphy wants to accept.If I understand correctly his arguments, he accepts that linear growth, while ultimately unsustainable, could continue for a very long time.
He makes and argument that space colonisation is probably either impossible or so impractical and slow that it will not make a large difference, at least in the foreseeable future.
(and syntax :D )
(I think I've did something wrong with the tags)
I didn't attempt a calculation, but my guess is not completely uneducated. According to Wikipedia:
"[...] there is 1.82×1026 kg of easily usable building material in the Solar System, enough for a 1-AU shell with a mass of 600 kg/m²—about 8–20 cm thick, depending on the density of the material. This includes the hard-to-access cores of the gas giants; the inner planets alone provide only 11.79×1024 kg, enough for a 1-AU shell with a mass of just 42 kg/m²."
IIUC, a Dyson sphere that radiates at ~3 K must be much larger than 1 AU, probably about the size of the Oort cloud (50,000 AU), hence, even considering the low gravity environment, the materials and energy costs of building it would be immense.
Hanson is talking about exponential growth, but Murphy is very clearly talking about any growth at all. His epilogue makes it clear, he is talking about "a model in which GDP is fixed—under conditions of stable energy, stable population, steady-state economy." Even the linear growth of space colonization is more than Murphy wants to accept.
I would guess that, even if you could find the materials, the energy cost of building it would probably exceed its energy output within its expected lifetime.Is this an educated guess or just a vague hunch? Any attempt at a calculation?
I think he uses that as a reductio ad absurdum: continued GDP growth would require energy prices to fall to an arbitrarily small fraction, but since energy prices can't fall to an arbitrarily small fraction of GDP, GDP growth can't continue indefinitely.
We don't get 20 resource doublings. Even if we managed to leave the Solar System, exponential energy growth at the assumed rate would require outpacing the speed of light in a few more centuries.
Good luck building a Dyson sphere, especially one that is so efficient that radiates at background temperature.I would guess that, even if you could find the materials, the energy cost of building it would probably exceed its energy output within its expected lifetime.
The most likely answer to Fermi's paradox is that alien civilisations, if they exist, are so sparse that detection, not to mention contact, is impossible.
Murphy refers specifically to GDP growth, which is what policy makers and economists giving advice on public policy refer to when they are talking about economic growth.
IIUC, his argument is that physical limits impose a maximum size on some vital sectors of the economy (food production, manufacturing, etc.) and this in turn imposes a cap on GDP (because the fraction of income spent on these vital products can't become arbitrarily small). It seems to me that his argument is correct.
In the end of the article, he appears to remark that this argument doesn't imply a cap on subjective utility, even if he doesn't use the term.
The end state of a civilization is a Dyson sphere collecting solar energy on the inside and radiating heat at the 3 degree K black body temperature on the outside. That allows the civilization to use superconducting circuits to minimize losses, allows the total energy of their star to be utilized and maximizes the thermodynamic efficiency of energy conversion.
Because the lifetime of a star on the main sequence is limited, and its rate of energy production increases as it ages, a civilization would want to remove mass from their star to prolong its life.
The answer to Fermi's Paradox might be that they are in Dyson spheres. They only radiate at the background black body temperature so they are invisible. It turns out that the oldest and smallest globular galaxies also have the highest concentrations of "dark matter". Maybe "dark matter" is the mass enclosed by Dyson spheres that is invisible because it radiates at the background black body temperature.
Still need to read more Freeman Dyson.
As Robin responded to me in the comments on his original post.... " Growth could continue for a while and then stop at a high level and then capacities could stay high forever after. Not such a bad outcome at all. But still, growth does end."
Tom the physicist is arguing that energy limits utility improvement. Robin is arguing that the world can become so awesome that we can no longer fathom why we should make it any better.
I agree with Robin.