
Exponential Economist Meets Finite Physicist (2012) - chepaslaaa
https://dothemath.ucsd.edu/2012/04/economist-meets-physicist
======
philipkglass
I generally liked the Do The Math posts but I thought this was one of the
weakest.

Physicist: "Right, if you plot the U.S. energy consumption in all forms from
1650 until now, you see a phenomenally faithful exponential at about 3% per
year over that whole span."

It's not phenomenally faithful. There's an inflection point visible even in
his large graph going back all the way to 1650. US primary energy consumption
in 1977 was 78 quadrillion BTU (quads). At 2.9% annual growth it would have
risen to 245 quads by 2017. Actual US primary energy consumption in 2017 was
only 98 quads. The _per capita_ primary energy consumption in the US was
actually higher in 1977.

Physicists don't need to imagine future limits to growth. The limits are
already visible in the historical record. But, contra the fears of many
scientists circa 1960, the limits to growth showed up on the demand side
before the supply side. We ended up with a world where widespread obesity is a
problem and predicted gigadeaths from starvation did not actually happen.

For any product you can imagine consuming, there are "obesity"-type limits to
how much more of that same product you can consume before the marginal utility
goes negative. For any service you might use, similar limits apply since there
are only 24 hours in a day.

The physicist character gives the more correct answer but his supporting
evidence is flawed. The economist has the much worse answers, but only (I
suspect) because he's a strawman constructed for didactic purposes. Economists
generally don't make 1400 year forecasts of any sort.

~~~
hn_throwaway_99
Thank you thank you thank you. Honestly, this whole article had the veneer to
me of "Ahh, poor silly economist..." I'm not sure if there is a great word for
it, but I call it the "humble-brag equivalent of obnoxiously condescending"

~~~
bshipp
I think part of the problem is that it's easy to draw a trend-line across a
batch of data you actually know about, like oil reserves or food supplies, but
incredibly difficult to make educated estimates about how we will resolve
constraint problems in the future.

Naturally, the most rigorous analyses are going to be heavily weighted toward
historical data, but will carefully ignore predicting future breakthroughs and
paradigm shifts. Any analysis that tries to highlight humanity's adaptive
ability would be laughably ignored, or at least minimized as being overly
speculative.

So here we sit, with our broken pessimistic models, because they're the only
ones the data supports.

~~~
philipkglass
It's not just the pessimistic scarcity predictions that suffer from long term
extrapolation. Optimistic ones of abundance have missed the mark just as
badly. Alvin Weinberg, writing in the June 1970 issue of the Bulletin of the
Atomic Scientists, made an optimistic case for the very large scale use of
breeder reactors -- 160 terawatts of breeder reactor capacity installed by
2050. His _physics_ are perfectly sound. But the demand growth which this
scenario assumes has not materialized.

He imagined that the world might come to demand 20 kilowatts per capita (more
than twice the present per capita use in the US) _and_ have 20 billion people
living in it. Neither population growth nor energy consumption per capita
growth have kept up with his estimates. Accordingly, nuclear fuel reprocessing
and the breeder reactor alike have remained niche technologies without broad
industrial impact. There was never enough uranium consumption growth to
economically justify complicated reactors or fuel cycles.

It is difficult to make predictions, especially about the future.

------
Chathamization
> per-capita energy use has surged dramatically over time

Per capita energy use seems to be declining in advanced economies[1].

> But if energy became arbitrarily cheap, someone could buy all of it, and
> suddenly the activities that comprise the economy would grind to a
> halt...There will be a floor to how low energy prices can go as a fraction
> of GDP.

That seems to be a bizarre understanding of how the economy works. Advances in
efficiency or energy production aren't going to be stopped at some point
because people are worried about someone buying up all the energy. You're not
going to get an inventor to say, "Hey, this new product would be too
efficient, I'm not going to introduce it to the market because then energy is
going to get so cheap that someone will buy it all up."

And someone could already try committing energy blackmail now if they really
wanted. Pepco powers Washington, D.C. and parts of Maryland, and Exelon bought
them for $6.8 billion. Some one, or a group of people could pay that and try
to blackmail the government. Of course, they wouldn't get anything for it but
a quick trip to prison.

[1]
[https://data.worldbank.org/indicator/EG.USE.PCAP.KG.OE?locat...](https://data.worldbank.org/indicator/EG.USE.PCAP.KG.OE?locations=US)

~~~
jbay808
I think we'd need to look globally, because it's easy to outsource your energy
intensive activities.

If I buy my bread from a baker, I can say I don't need any energy to run an
oven anymore, but that doesn't imply that when the baker gets as wealthy as I
am the world won't need ovens anymore.

~~~
philipkglass
Chathamization linked to a graph of energy use per capita in the US, showing
that it peaked in the 1970s. In 2015 it was 6804 kgoe per capita, well below
the peak of 8438 kgoe recorded in 1978.

CO2 emissions are a decent proxy for primary energy in our present fossil-
dominated era, and when accounting for CO2 embodied in imports, the US does
look worse. But it doesn't make a _big_ difference:

[https://www.carbonbrief.org/mapped-worlds-largest-
co2-import...](https://www.carbonbrief.org/mapped-worlds-largest-
co2-importers-exporters)

"Despite the large total of CO2 imports and exports, US emissions are only 6%
higher and Chinese emissions are 13% lower when CO2 transfers are taken into
account."

If the energy/CO2 really should be increased 6% to account for imports, that
would put American energy consumption at 6804 * 1.06 = 7212 kgoe per capita in
2015, still lower than in the 1970s.

~~~
AstralStorm
It should be moved some from China to USA because of trash exports too. (Also
probably Malaysia.)

Anyway, it's great when you compare yourself to second worst.

------
scythe
Tom Murphy's website occasionally comes up in futurist circles. His general
point that unbounded exponential growth is impossible is _obviously_ correct,
but I find his condescending attitude tiresome and he often exaggerates the
apparent validity of his pessimism through questionable arguments.

For example, he first insists that the conversation about energy consumption
be confined to Earth and ignore space exploration, which is reasonably
sensible because of the large energy cost of space travel. He moves from there
to a thermodynamic bound on energy dissipation _from_ Earth _into_ space via
black-body radiation. This argument is self-contradictory: if we _were_
producing so much energy that it were able to heat the atmosphere (>1000x
today), we would certainly have enough energy to fly into space. (The linked
article "Why not space?" contains no math and few real arguments:
[https://dothemath.ucsd.edu/2011/10/why-not-
space/](https://dothemath.ucsd.edu/2011/10/why-not-space/) )

Also, this paragraph is relatively good evidence he didn't talk to a real
economist:

> _But if energy became arbitrarily cheap, someone could buy all of it, and
> suddenly the activities that comprise the economy would grind to a halt.
> Food would stop arriving at the plate without energy for purchase, so people
> would pay attention to this. Someone would be willing to pay more for it.
> Everyone would. There will be a floor to how low energy prices can go as a
> fraction of GDP._

None of this hemming and hawing about infinity answers the real question: is
it possible for the global economy to grow until nobody has to live in mud-
huts without air conditioning? The answer is almost certainly _yes_.

~~~
dosy
It does seem like physicist enjoys spreading the pessimism of that position in
a condescending way, which makes me think the allegedly "faithful" write up of
the dinner conversation, was in fact compensating for one where the physicist
felt they had been beaten, and was so annoyed by that they have re-written the
conversation in this more favorable way where it appears they win the
argument.

Besides, I think that pessimism (what the physicist probably thinks is
realism) rests on one key point, that the price of energy will have a non-zero
floor. If you remove that, everything is possible, even assuming steady that
energy use, and requiring continued economic growth.

I think the avoidance / supposed maintenance of the "energy price floor" point
was too weak. The assumption was that it will still be a purchasable resource
("someone could _buy_ all of it" and hold everyone else hostage), but what if
energy becomes unlike that? What if energy in the future is unlimited and no
one can buy all of it because everyone can access it? And the only constraint
Earth imposes is that no one uses too much so we don't boil off the atmosphere
or whatever.

I think that's likely. Zero point energy, free energy from the vacuum. Some
whistle-blowers say our secret space program already drives its ships with
this kind of power.

What's interesting is that, based on these projections about hitting critical
energy output, we won't _need_ this ZPE for another 250 - 600 years. So maybe
that's why, if it does exist, it is not going to be released until then. Kind
of sad that 40 years ago or so, some bureaucrat planner may have robbed the
human race of free energy for the next few centuries because of the
projections of an economist and a physicist, not these two, but some other
pair tasked with considering the economic and physical implications of then
soon-to-be back-engineered alien technology.

~~~
jbay808
_What if X is free for everyone in unlimited quantity? And the only
constraint... is that no one uses too much?_

Sounds like a pricing mechanism had better appear. Fish are free for anyone to
catch, as long as nobody catches the last two...

I feel like the rest of your post was trolling, though, so I'm not sure you
were serious about this part.

~~~
dosy
There's others ways to restrict access that aren't pricing. you can't marry
more than one person, you can't take up all the space on a beach or a public
park. it's not about price, is just laws and enforcement.

I wasn't trolling on the rest, just brave. I don't expect you to be able to
respond without name calling tho, as I think you'll see free energy as topic
you can't seriously touch lest it taint your reputation.

------
jeremysalwen
I read through the comments expecting the typical HN takedown of the whole
bogus idea that energy must become cheaper as a fraction of the economy in
order for it to keep growing. But surprisingly, nobody more economically
literate than me has done so, so I guess it falls on me.

We already have experience with an economic input which is required for
practically all production becoming less important to the economy as
efficiency increases, it's called labor. And as efficiency of labor usage
increases, the price of labor goes up, not down, see Baumol's Cost Disease. So
no, the fact that the price of energy will go up with gdp does not mean the
growth is "illusory", and the fact that an "extremely prestigious" econ
professor did not point this out is a bit fishy.

~~~
jbay808
I'm not sure this is quite a takedown of the author's point. In fact, I'm
surprised at how many people on HN seem to be misunderstanding this.

The author is saying that physics puts a fairly solid cap on the amount of
power we can produce on earth. That's the basic point.

What does a finite energy-consuming, exponentially growing economy look like?

If we accept that all economic transactions consume some energy, and the
economy is growing (so the number or the value of economic transactions is
increasing), then once we've hit our physical constraint on power generation,
how does growth continue? Only if the energy required per unit of transaction-
value continually decreases. So the price of energy must continue to drop,
measured by the relative to the value it provides.

The author then points out that this is a _contradiction_ because the price of
energy would have to rise, and therefore that the problem is in the assumption
of continuing exponential growth.

~~~
cinquemb
> _then once we 've hit our physical constraint on power generation_

Are we supposed to accept this? Because I do not. I think the way that we
allocate resources towards energy collection/generation/consumption is a
bigger constraint than what physics can currently allow.

~~~
stouset
This is covered in an earlier post of his. At current growth rates, we’ll
start noticeably heating the Earth in only a few hundred years. Not from the
greenhouse effect, but from literally saturating the Earth’s capacity to
radiate excess energy as heat into space.

This is a raw physical limitation. How we use and how we generate the energy
are irrelevant details. The only thing that matters is Earth’s ambient
temperature, the additional wattage being used planetwide, and the Earth’s
radius. Past a certain point, Earth’s equilibrium temperature will rise well
past current levels, and rapidly.

~~~
cinquemb
> How we use and how we generate the energy are irrelevant details.

Just as irrelevant as assuming the basis behind current growth rates where it
is impossible to mitigate agaisnt "literally saturating the Earth’s capacity
to radiate excess energy as heat into space".

All of this is based on assumptions. You can't just accept one set of
assumptions that underlie a model and throw out others that could refute it
(well one could, but it isn't intellectually honest).

~~~
mnl
That's the great thing about thermodynamics, you can determine bounds for a
few magnitudes in a physical system ignoring all the details about its
evolution.

For instance you can't disrupt the 2nd law, so at some point it's actually
true that it is impossible to mitigate overheating and you won't be able to
improve Stefan-Boltzmann law (except for increasing our emissivity, at night
I'd guess). You can try to play with mass transfer but more thermal escape is
not a good idea and a heat exchanger with extraterrestrial masses won't work.

I know it's hard to take and that physicists sound arrogant when they do this,
but that's how it is.

~~~
cinquemb
"Wavelength- and subwavelength-scale particles,[1] metamaterials,[2] and other
nanostructures are not subject to ray-optical limits and may be designed to
exceed the Stefan–Boltzmann law."

~~~
BlueTemplar
That's interesting - are they more efficient at getting rid of entropy ? (And
what would be the new limits? If they only give, for instance, a single
doubling worth, that won't buy us much more time...)

~~~
cinquemb
This was my prof at the time who introduced me to this stuff he was working
on[0], you can read more about his work on their site if you are interested.

[0] [http://www.zia-lab.com/](http://www.zia-lab.com/)

------
age_bronze
There's an underlying assumption that economical growth has anything to do
with physical limits. Economical growth is a lie we tell ourselves so that
innovation has its incentives, while everything else that's there because it
must be there (because it will always have a demand), such as energy (but also
food, real estate, etc.) just piggybacks with a similar 'fake growth' that
really arises only from the fact these things are just as valuable as before.
The threat for the lack of supply is just enough to keep businesses that can't
really 'grow' still grow. It will still be exponential growth so long as the
leading innovation companies are growing and everyone else is just corrected
for inflation.

~~~
ThrustVectoring
The less cynical interpretation is that "real goods and services" captures the
_value people derive from them_ , rather than some objective measure like
"energy consumption". There's no innate reason why we can't figure out more
and more valuable ways to do things pretty much indefinitely.

~~~
paraschopra
It depends what you call and measure as value.

If it’s production or goods, there’s obviously an upper limit. Even if in
distant future, we begin assembling atoms into making novel rare elements, all
that process consumes energy and possibly would produce waste. Production is
not free. In the exponential limit, we will hit some constraint.

If we are talking about services, we should realise that even they cost
energy. Even if we tomorrow think that long distance travel will be replaced
by VR, production and delivery of such experiences cost energy.

Fundamental argument is then about energy. Can we keep harnessing it
infinitely? No. Even if we make energy efficient processes, Jevon’s paradox
suggests we will simply start using more energy.

The only way physical limits can be respected is by limiting the growth of
economy and population. (Otherwise if we keep printing money without increase
in production, it isn’t really economic growth)

~~~
cinquemb
> Fundamental argument is then about energy. Can we keep harnessing it
> infinitely? No. Even if we make energy efficient processes, Jevon’s paradox
> suggests we will simply start using more energy.

The thing about infinity is that while it is a limit, it can always be
approached based on ones understanding. And I would not state that our
knowledge and application of energy collection/generation (and even energy
itself) is fairly limited.

>The only way physical limits can be respected is by limiting the growth of
economy and population. (Otherwise if we keep printing money without increase
in production, it isn’t really economic growth)

I disagree (and debt monetization != printing money), naturally markets and
systems will correct. They always have, even when people try to distort it and
keep them from correcting.

~~~
paraschopra
>naturally markets and systems will correct.

Markets and systems obviously correct, but the key question is at what cost
and to whom. Imagine for a moment that we find ourselves in a situation where
energy is limited. Markets will correct themselves by making it expensive, but
who'll suffer the most is the poor (while markets might have been reacting to
overconsumption by the rich).

Saying markets will correct themselves is like saying things sort out
themselves. They do, but usually who takes a hit isn't fair and ethical (as
was evident by 2008 crisis).

------
PaulAJ
The basic fallacy here is the proposition that all economic activity involves
physical work, and hence energy == economic activity. However this is not the
case. My economic activity consists of staring at a screen and pressing
buttons. It is therefore perfectly possible that energy consumption can level
off while economic growth continues.

One can imagine a similar conversation between a geographer and an economist
(if one existed) in 1700 in which the geographer made the same argument about
land use; at the time economic growth was very much about bringing land under
cultivation or other use, and hence (the geographer would argue) economic
growth would be limited by the finite amount of land. Same fallacy.

~~~
fallingfrog
Pressing buttons _is_ physical work, unless you're doing it via astral
projection.

~~~
dane-pgp
But to create 10 times as much value, you don't have to necessarily press
buttons 10 times faster or 10 times harder.

It's possible that by pressing the same number of buttons per year (i.e. the
same number of programmer hours worked), the current generation of software in
the world could be upgraded to a new, more valuable generation of software.

There's a question of whether new software (presumably with extra features)
necessarily uses more energy (per user, per year), but it seems possible that
one year's more-valuable-software could be more energy-efficient than the
previous year's less-valuable-software.

------
pmalynin
I think the dismissal of space colonization over a period of 400 years
is...unreasonable. We could move all production to Mars for example and only
consume the shipped resources. Sure that’s one doubling right there, but we
could continue this process.

~~~
TaylorAlexander
Mars does look a lot closer in 2019 than it did in 2012. Back then it seemed
like no real plan existed, except for one little company not a lot of folks
believed in. Now we’ve got billionaires in a space race and suddenly it seems
obvious that we’ll colonize space to some degree even in the next 100 years,
likely with some aggressive growth. We’ve only recently come off the gloomy
decades after Apollo where space exploration was so muted compared to the
glory days.

~~~
ajnin
Sure it seems closer now than before, but reaching Mars is still very very
far, it's nothing like going down the road to the chemist, for example let's
say that we want to pursue the current population growth but on Mars, that's
an estimated 82 million new people per year (130 million if you count only
births), using the Starship SpaceX is currently developing that would take
820000 launches per year or 2250 per day.

But those ships are not like planes, you can't reuse them multiple times a
day, the trip to Mars takes something like 6 months, and that's a launch
window that opens only once every 2 years, the rest of the time it takes
longer and more propellant, so your ships would make the round trip in 1 or 2
years, so you'd need to build 820k to 1.6 million ships only to be able to
shuttle the population to Mars and stay constant on Earth.

That would be a serious industrial investment. A quick search says that there
are around 24000 planes in service in the world, and over the course of
history, 150000 planes have been built, including all military and commercial
aircraft. So we'd need to build a production with many many times more
capacity that all the airplane builder that exist today.

Then there is the energy cost of those ships, Earth gravity well is actually
pretty deep and chemical propulsion only just is able to escape it. That many
launches is going to need a lot of energy, a rocket can hold up to 500 tons of
fuel, multiplied by several thousands of launches per day, and you reach a
non-negligible percentage of the current daily worldwide energy expenditure.

The idea of being able to mine asteroids or outsource production in a
meaningful way on another planet is similarly unrealistic, escaping gravity is
not easy. Of course the technology will improve, but not by the several orders
of magnitude that would be needed. When we colonize space, it is likely that
it will be more like seeds, with only relatively minimal exchanges when the
scale reaches a whole planet.

~~~
BlueTemplar
Actually, a space elevator would help a lot here, but it's questionable
when/if we will be able to build one...

------
acchow
Absolutely there are thermodynamic limits to energy "use" on the planet.

But isn't it obvious that we will expand into space stations and then
eventually onto other planets?

> But if energy became arbitrarily cheap, someone could buy all of it, and
> suddenly the activities that comprise the economy would grind to a halt.

This segment contained a number of logical leaps that I can't agree with. It
is possible for energy cost to fall arbitrarily low without reaching zero. And
you can imagine an arbitrarily low price that would skyrocket quickly if
someone actually _tried_ to buy all the energy.

> So once our fixed annual energy costs 1% of GDP, the 99% remaining will find
> itself stuck. If it tries to grow, energy prices must grow in proportion and
> we have monetary inflation, but no real growth.

I'm not able to follow the claim here. Can anyone shed some light?

~~~
dosy
I think it's a condensed version of saying:

If we have finite energy at a fixed price (of say 1% of GDP in total cost),
then either the rest of the GDP (which is not energy) does not grow, and so
the demand for that energy (and so its price) remains the same, or it tries to
grow (and cannot "is stuck") because growth will increase demand for the
energy and therefore drive up prices, but since it is energy and fundamental
to everything, all prices will go up, so we will have inflation, but inflation
is not growth.

~~~
acchow
> but since it is energy and fundamental to everything, all prices will go up,
> so we will have inflation, but inflation is not growth.

Oh ok... I see why I got lost. In my head I didn't hold the assumption that
"all growth necessarily must consume more energy". This is assumed throughout
the article until the Epilogue.

But if you drop this assumption, then I don't think the "it's just inflation
not growth" holds anymore.

~~~
dosy
I had to parse that part a few times to get it myself, when I saw you didn't
get it too I could relate.

Then I had to think a few times about what you gave in response! It seems this
part of the topic is quite involved. I think I get some of it now.

If you drop the assumption that grow takes energy, then no extra demand on
energy from growth, then no price increase on energy, then no inflation, and
so it's just growth, not inflation. Agreed.

But when you and me are examining it like this...the whole situation described
by that sentence starts to seem a little contrived to me. Seems there's a lot
of error bars on each of the assumed connections in that causal chain, that
could lead that path to branch at each of them into many other possible paths,
rather than just the one path that condensed sentence proposes.

I still have a hard time imagining a growth that doesn't use more energy
(except the one defined in that article as "development", which seems to be a
more sophisticated/involved use of existing resources, rather than
extracting/creating more new (primary) resources.)

If you could elaborate some more on your images of growth that don't consume
more energy, I'd find it helpful to understand this whole thing better.

~~~
kgwgk
> I still have a hard time imagining a growth that doesn't use more energy
> (except the one defined in that article as "development", which seems to be
> a more sophisticated/involved use of existing resources, rather than
> extracting/creating more new (primary) resources.)

Can’t you imagine efficiency gains leading to an increase in output (GDP) for
constant inputs (resources)? That’s growth. (Note that the article talks about
development as something different from GDP growth.)

~~~
dosy
Right, I think the article was saying development is GDP stagnation but
increasing quality nonetheless, does that about match your understanding of
it?

I still can't really imagine the other scenario because when I see efficiency
gains I think they will lead to growth and more energy usage. Examples like
"increasing CPU power should have led to faster software, but instead it lead
to slower languages and larger software". Same for memory and bandwidth. Our
websites keep expanding to fill the next generation of network capacity.

So the gains from efficiency are quickly consumed by increasing growth and
energy use. Maybe you could help me imagine some that are not like that? I'd
like that.

It's easier for me to imagine the examples like in the article (more fancy
dessert, same ingredients) that are there classed as development, distinct
from growth. But growth as defined there, with static energy, I can't imagine
right now.

~~~
kgwgk
> I think the article was saying development is GDP stagnation but increasing
> quality nonetheless

I don't know what the article is trying to say, really. It talks about
"improving the quality of life" but I'm not sure if that includes factors that
are already considered in GDP calculations
([https://www.bea.gov/sites/default/files/papers/P2006-6_0.pdf](https://www.bea.gov/sites/default/files/papers/P2006-6_0.pdf))
or it's about immaterial quality of life improvements (more hapiness or
whatever).

> But growth as defined there, with static energy, I can't imagine right now.

Say you have a factory producing 1000 widgets per day and you improve the
efficiency of the process and now you produce 1100 widgets per day using the
same quantities of labour, raw materials and energy. Don't you agree that this
is growth?

~~~
dosy
Cool link, thanks I'll read it.

I'm not actually sure right now. Somehow I think that if you make those extra
widgets without using more energy, then the extra people who buy and use those
extra widgets will end up using more energy in doing so, and their extra
purchase and use will, however incrementally, grow the economy as a whole a
tiny bit, which will use that much extra energy.

So if it's growth, then it can't be static energy.

But somehow also I think that you can have static energy and not call it
growth, but development, or something else like someone said before (maybe
you).

What's development? I don't know. But maybe it's something like we produce
1000 widgets with more intricate decorations on them. And use no more energy
doing so.

I grant that it's pretty confusing. And that's how it seems to me right now.

Thanks

~~~
kgwgk
The economy is a complex system, the only way to be sure that when you change
something somewhere the energy consumption will remain constant is to put a
constraint on it. You could set quotas, increase/decrese taxes to drive it to
the desired targets, etc.

Imagine the system is at equilibrium at a certain output and energy usage and
you discover a device than increases efficiency in the use of energy by 10%.
The system could produce the same output as before using 10% less energy. But
the new equilibrium won't be the same output at 10% less energy consumption,
because some resources will be freed in the energy generation sector and the
price of energy will go down resulting in some activities that were not
economically viable before becoming viable. Maybe desalting sea water was too
expensive before, but with lower energy prices and higher efficiency it does
make sense, for example. You will have an increase in output but whether the
new energy consumption is below or above the original level depends on the
details. The latter is more likely, I guess.

~~~
dosy
Thank you for explaining / taking me through that. I totally agree that it's
in the details.

My factory now makes the same amount of sneakers but uses less energy, and I
have more profit which I can spend on more things, maybe making new markets
viable. And in the macro picture, that extra energy, lower prices, makes some
things become viable. And what happens from there regarding energy depends on
the details. Very interesting and good, semi-detailed discussion.

------
heraclius
It’s not clear how meaningful these measurements are anyway. Consider two
years: in the first, 1000 tonnes of wheat are produced, and in the second, 500
tonnes of wheat and 300 of steel. Which year, one asks, is more productive? We
can measure everything in wheat-equivalent or steel-equivalent or (commodity-
basket)-equivalent (i.e. PPP) but ultimately such calculations are just as
arbitrary as reduction to wheat bushels (or carpet kilometres or whatever.)
Incommensurability therefore seems to make all this fairly meaningless.

~~~
jbay808
This is why, as all economists agree, measurements of economic growth are
completely arbitrary and the economy hasn't changed in any meaningful way that
can be called "growth" since the middle ages.

... Oh, wait, or maybe growth actually _can_ be expressed as a quantifiable
concept?

In this case, the author chooses energy as an objective measurement, because
all economic transactions must consume energy in order to occur.

~~~
mr_toad
> the author chooses energy

And is thereby begging the question.

Economists value goods using prices.

~~~
AstralStorm
Prices fluctuate a lot, embodied energy and production energy can fluctuate
for the same thing too, but trend down until they got the ceiling or whole
branch of technology is phased out.

You could take some representative branches of housing to build what is called
an energy basket, using similar method used to calculate PPP.

Such rough methods would include communication, transportation, housing,
clothing, food, self-expression and a few more mostly timeless needs that
haven't changed for many centuries.

The problem is of accurate representative sampling of each category. That gets
easier the closer we are to modernity with big data gathering.

The methodology would survive start from before bronze age even, I think.

------
evdev
Am I missing something, or hasn't energy per capita in the developed world
already stopped growing? As well as population growth in rich societies?

~~~
jbotz
Energy consumption has _not_ stopped growing in rich societies... so long as
the economy grows, energy consumption grows. The relationship isn't perfectly
linear only because the available metrics are imperfect, but if you have any
data that outright contradicts this rather reasonable assupmtion, please show
us.

~~~
evdev
[https://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&...](https://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&met_y=eg_use_pcap_kg_oe&idim=country:USA:CHN:CAN&hl=en&dl=en#!ctype=l&strail=false&bcs=d&nselm=h&met_y=eg_use_pcap_kg_oe&scale_y=lin&ind_y=false&rdim=region&idim=country:USA:CHN:CAN&ifdim=region&tstart=-302731200000&tend=1432872000000&hl=en_US&dl=en&ind=false)

~~~
jbotz
Huh, I sure put my foot in my mouth on that one... a rather big assumption I
never checked. Recalibrating...

But in my defense it's worth mentioning that _globally_ it still seems to hold
true. The fact that energy consumption stopped in rich countries is apparently
mostly due to the fact that manufacturing, which is one of the most energy-
intensive parts of the economy, moved to poorer countries. But since the rich
countries consume those manufactured products, the energy use should be
counted against them too!

~~~
philipkglass
See my above reply to jbay808. If you include imports, CO2 emissions
attributable to the US increase by 6%. Even with that 6% upward correction,
primary energy consumption per capita in the US now is lower than it was in
the 1970s.

------
seiferteric
Only complaint is the discussion about super computers consuming vast amounts
of power. I do think there is still room for many more doublings in efficiency
for computers, it will likely require a switch to a completely new technology
though. Also a bit more wild speculation... He does not account for the idea
of space based manufacturing (he just mentions living in space). It's at least
conceivable we could one day have almost everything made in space (even food)
and air dropped to us periodically. Wouldn't this bypass his main argument? We
could even have space based energy production, beamed down to earth via laser.
There would still be waste heat of the energy consumed, but you would
eliminate the waste heat of the actual energy production (he sited ~30%
efficiency for power plants, so 70% waste heat).

~~~
jbay808
"I do think there is still room for many more doublings in efficiency for
computers"

I don't think our finite physicist is arguing that exponential growth can't
happen temporarily, just that _eventually_ we hit the boundaries of our petri
dish. It's a challenge to economic models that sometimes deny in principle
that the petri dish even has boundaries.

~~~
Mirioron
If the universe is infinite then that does imply that eventually the petri
dish will be too.

~~~
jbay808
It doesn't, actually. The universe is getting bigger but the available
negentropy, practically speaking, is not. A big, heat-death universe is not a
useful resource to anyone.

------
fallingfrog
I just want to draw attention to something which we are glossing over, which
is that saying economic growth has a very high limit and saying that it has
_no_ limit are very, very different claims. If the claim you're making is that
it has _no_ limit, then the counterargument is trivial: the universe is
finite, it contains a finite capacity for information storage, therefore no
matter how you define "economy" the answer you get will be a finite number.

But, I still see a lot of people who won't even concede the point in the case
of unlimited growth. That, to me, suggests that we are looking at a deeper
phenomenon than can be resolved via logical arguments.

Think about the responses that believers have when confronted with the
argument that there is no god. That is not an argument they can confront
objectively. They respond with anger, disgust, etc. You're not making a truth
claim to them; you're attacking their happiness in the afterlife. You're
suggesting that their grandparents have vanished into nothingness instead of
being in heaven. No matter what the facts are, they can never accept such an
argument.

I get the exact same feeling from all of you arguing for infinite exponential
growth. You're not reacting as if this is a truth claim; you're reacting like
I'm trying to take away your happy future, in which everyone is fabulously
wealthy and everything continuously improves, forever.

Think about how it makes you _feel_ to consider that economic and scientific
growth may have a limit. Can you be certain that you are really objective on
this topic?

------
challenger22
Has anyone done the math to determine what fraction of global warming is just
from the steady-state relationship between heat production and radiation into
space, regardless of changes in albedo? Always been curious about that one.

i.e. In the same way that a computer runs hotter when consuming more wattage,
how much has the Earth gotten hotter just because we are consuming more
wattage lately?

------
lerno
If we assume average value of GDP at t = g(t)

Energy usage per point of GDP = f(t)

Then we can obviously construct a hypothetical scenario:

lim t->inf g(t) * f(t) = C

This is obviously possible if one flips it over, making economic growth depend
on the rate of which we reduce the energy cost for producing a dollar of GDP.

This obviously means that production must be decoupled from the sheer AMOUNT
of physical goods, as those are necessarily limited.

To increase GDP, we do not need to increase the amount we produce but the
value of what we produce.

Sure, one way to increase GDP would be to produce two cars for the same
resource use as one car would need. And that has limits.

But if I can produce a rocket that can propel something to orbit with the
resource use of a car, I’m am not only enabling more rockets being built, but
also actively reduce the energy cost of one.

------
Stay_frostJebel
Ultimately, this is a problem of semantics. Physics describes one objective
reality that interacts with billions of subjective realities. Economics
describes how billions of subjective realities interact to form one objective
reality.

The article has a few places where the physicist attempts to ascribe an
intrinsic value to an item (say dessert types) independent of the supply and
demand curves for that item. The whole concept of a demand curve is that
everyone has their own value that they give to an item. The fact that some
people do NOT value some particular lifestyle improvements does not affect
econ in the slightest.

------
ericdykstra
This reminds me of the Limits to Growth graph, popularized by #GraphTwitter

[https://pbs.twimg.com/media/D7LCSEDWwAE5_Ar.jpg](https://pbs.twimg.com/media/D7LCSEDWwAE5_Ar.jpg)

------
sadness2
> thermodynamic limits impose a cap to energy growth lest we cook ourselves ..
> I’m talking about radiating the spent energy into space

Huh? This seems to be a critical premise for establishing a crisis, yet it's
incoherent and essentially imaginary.

Ok, some ways we use energy have poor thermal efficiency. Light bulbs are the
classic example, but look at the improvement from incandescent bulbs to LED's.
Most uses of energy just move heat around within the environment, and if
anything that would tend towards thermal equilibrium (a sort of microcosmic
'heat death'?), not "cooking".

~~~
BlueTemplar
No, it's basic thermodynamics : [https://www.sciencealert.com/scientists-have-
developed-a-sol...](https://www.sciencealert.com/scientists-have-developed-a-
solar-panel-that-can-also-beam-heat-into-the-cold-void-of-space)

~~~
xiphias2
This is really cool, so there's a way to radiate heat to the space much more
efficiently than the sun does, which destroys the argument of the physicist.

~~~
BlueTemplar
I think you meant "much more efficiently than the Earth does" ? It weakens the
argument... but I'm uncertain whether fatally or not. You still need to
radiate exponentially increasing amounts of power to outer space ! This is
going to mess with surface temperature sooner or later...

------
Swivekth18
It is possible to grow economically within a constrained energy budget, as the
lever metaphor suggests. With efficiency, it is even possible to double the
population… But I find it very hard to believe in a continued economic growth
simultaneously with a declining energy budget, especially when the economic
aspect is facing a cliff of massive debt. The only way out is good ole
industrialism on a massive scale in such a scientific way to keep cooking
dinner and not spoil the garden.

------
Glyptodon
Water seems more interesting than energy as a bound. If energy gets as cheap
as breathable air is now due to some sort of long running series of changes
and improvements cornering the market would be like trying to bag the whole
atmosphere and then charge people for it. The cheapest things are the most
impossible to corner. Not that I have any idea whether some sort of ability to
do more with less can bound energy use below some arbitrary output threshold.

------
Amboto2205
Doesn’t the definition of a “steady-state” economy mean that there will be no
real GDP growth, but only nominal growth? I don’t understand the assertion
that GDP can grow indefinitely just because the arbitary “utility” can. There
will still be physical limits inside a steady-state which would be subjected
to price, which will affect GDP.

------
karmakaze
Flaws aside a fun read.. It's a set-up when we're talking about an indefinite
time scale AND bounding the discussion to Earth. Also the 1400 year time scale
seems absurd. If/when for instance we have continuing orders of magnitude
efficiencies in quantum computing. The physicist is debating for the wrong
side.

------
jasonhansel
Even if there is some limit to economic growth in the distant future, is that
necessarily a _bad_ thing? It might be that, by the time we reach this limit,
society would be so prosperous that we would see no reason to exceed it.

~~~
drdeca
This seems possible, yes, though if it is the case, I think we ought to
prepare for that eventuality somewhat ahead of time, so that we don’t
encounter a nasty shock when the time comes.

------
jobigoud
I often wonder where we would be if the Earth was the size of Jupiter. Or if
life started on the Moon instead of Earth.

------
vbuwivbiu
not one mention of bitcoin in this discussion, which would seem to be the
obvious connection between physics and economics

------
orasis
Exponential growth can continue in virtual realities as the physical reality
maxes out.

~~~
kreldjarn
Did you read the piece? They talk about VR.

~~~
Ancalagon
Actually, they dismissed it pretty quickly I thought.

~~~
jbay808
I believe the "dismissal" is this cogent argument:

Shuffling bits around takes energy; if your virtual reality services grow
exponentially and energy production doesn't, then the price of energy must
also increase exponentially or else one of your VR companies could buy all the
energy and shut down the competition.

Energy production (and computation) are limited by the capacity of the earth
to vent heat into space at a reasonable surface temperature.

So unless you allow for an exponentially expanding real-world physical
economy, you can't have an exponentially growing virtual economy.

~~~
b_tterc_p
The price of energy is capped at the cost to privately produce it for
yourself, which is probably pretty low in the scheme of all encompassing
virtual real estate fiscal gods.

~~~
jbay808
Not unless the physical economy is growing at about the same rate as the
virtual one. Or else how is that extra power generation capacity being added?

~~~
b_tterc_p
If the virtual economy grows 10%, that doesn’t mean we need 10% more energy to
make it happen.

------
cerealbad
isn't the universe expanding at an accelerating rate? if the problem is excess
planetary heat, you can use thermosynthesis to accelerate novel thermogenesis
in pseudo-living species - imagine endothermic sea sponges cooling the oceans
and helping to repopulate at risk ocean animals.

"this thing humans do cannot continue" is a weak argument. everything humans
do is some expression of the natural state of conditions in their immediate
environment, technology is just another convolutional cycle on top of the pre-
existing ones, squeezing more efficiency from the raw resources existing
there. the planet is not in balance, and ecosystems are not fixed. things are
in a state of glacial flux with periods of extreme instability due to various
cycle renewals - volcanic, tectonic, asteroid/comet impactor, solar,
geomagnetic symmetry breaking, viral.

'man made causes' are a misnomer, they are just accelerated selection events,
man happens to be a global selector for almost all living things, and man
activity on the planet can be a mass extinction event due to many scaling
factors, the most obvious one being the technology cycle mentioned previously,
the efficiency it provides can be simplified to 'making more heat'.

it's easy to fall prey to goldilocks thinking - due to limited information and
the tyranny of the present. try to think in terms beyond a human lifespan.
look at the progress achieved in the past 300 years. if we wanted to we could
spend the next 300 years returning earth back to a pre industrial epoch and
wipe from the surface of the planet all traces of the modern advanced
civilization we created, not by a cataclysm or destructive war but by planned
intentional decolonisation. given that its possible and very likely to happen
(perhaps a catalyst is required, like a new global religion) over the past
300k-1my this maybe happened multiple times. humans are still here in some
form or another and they will continue to be here into the foreseeable future
x10 my's, because they have shown capable of surviving (milankovitch scales,
100k, 41k, 23k years).

technology is dominant and makes the smartest humans think in brittle ways.
the people shaping rocks for millennia were not stupid, they were just
incapable of thinking beyond their stone paradigm. pretend to be a godlike
alien silently watching the world from the largrangian point in the earth-moon
system. millions and billions of years go by. once life begins on earth it
continues into the present, the idea that humans, in the next few thousand
years, will somehow pose an unconscious risk to a process that has survived
and morphed for billions of years is a misreading of the story. what COULD
happen is another mass selection event, where a human bottleneck eliminates
99.9% of all living things. that happened before and it's part of some larger
cycle that humans are necessarily a part of (as living things) and what is
considered causal could also be simply an expression of a deeper reason for
living things to exist - to out compete other living things and monopolize the
space available to them.

is the physicist a finitist? seems like he substituted growth which is the
economists mantra, for change which is his. predicting the future is a waste
of time, as an agent in the world you will either cause the future or be slave
to it despite your best efforts either way. if it is knowable it will be
unchangeable, given all your free actions will lead to the known outcome. it
is clearly unknowable and therefore ununchangeable - since the capacity to
measure any deviation or change does not exist. what will occur is as likely
to occur or not occur had you participated or not.

my pet theory is that any time you see people attempting a cross-disciplinary
leap of faith their parachute often fails to open. good 20th century examples
being james watson and william shockley - both making the tempting leap from
(bio)electrical systems to socio-communication ones, leading to self-
embarrassment. the only interesting problem for the 21st century is how do you
transform knowledge from one domain to another and retain it, the only way
humans will survive their own extinction without reverting back to barbaric
primitivism is to plasticize expertise and mass produce it.

~~~
drdeca
> if the problem is excess planetary heat, you can use thermosynthesis to
> accelerate novel thermogenesis in pseudo-living species - imagine
> endothermic sea sponges cooling the oceans

Uh,

Thermodynamics.

You can’t destroy heat, just pump it around.

A heater does not need to expel cold. A cooler needs to expel heat.

Stuff can feed on heat gradients. Things cannot feed on uniform heat.

~~~
cerealbad
a seebeck generator can exploit airflow above or depth below oceans to convert
heat into electricity. what uniform heat? all human heat effects augment the
existing temperature cycles which have baked in gradients. thermoelectric
processes simply reverse this, it would cause a lot of rain and raise ocean
levels as the excess atmospheric water vapor is returned to a liquid state-
due to the transformation of heat into electricity which would be stored or
used to move the little sea robots around.

is the sun uniform heat? how do ectothermic animals and plants using
photosynthesis work? I'm not sure why you think you can magically break
thermodynamic symmetry...

~~~
drdeca
A seebeck generator “converts a heat flux into electrical energy” (Wikipedia),
it does not convert heat into electricity.

(Edit: by which I mean, it does not decrease the total amount of heat in the
system.)

You need something colder on the other side.

The sun-earth system is not uniform in heat, no. The sun on average is hotter
than the earth on average.

Edit: what thermodynamic symmetry are you referring to?

~~~
cerealbad
the mechanism that generates heat is reversible, that's how we got fossil
fuels to begin with (hydrocarbon storage). if you think converting heat flux
into electrical or mechanical energy doesn't reduce the total heat flux of the
system then it's a perpetual motion engine? you get more energy out than you
put in? think it through.

it's powered by a heat differential, you are draining the heat from the system
and storing it or dissipating it under motion - reducing the overall flux -
over time by cooling the hot side and heating the cool side eventually some
equilibrium is reached, depending on how efficient the throughput is and how
much heat you have, you then exhaust your temperature gradient and need to
move somewhere hotter or colder.

one of us is very confused here. i claim "you can reduce heat locally in the
earth system", and give examples: capturing and insulating it (trees, plants),
converting it into other types of energy (genetically modified sea
sponge/robots), as well as venting it into space through an
atmospheric/orbital seebeck ring.

im not breaking any laws of thermodynamics, i am turning the planet into a
refrigerator.

edit: to clarify i am claiming it's possible to move heat away from the
habitable thin boundary layer by conversion: storage, mechanical use or
venting.

~~~
drdeca
I agree that converting heat flux (or, uh, temperature gradient? I think I
might actually mean temperature gradient) into electrical or mechanical energy
reduces the amount of heat flux ( or temperature gradient) of the system.

Reducing the temperature gradient(s) of the system does not reduce the amount
of heat in the system. When the temperature gradient decreases, that just
means that there isn’t as much variation in the temperatures in the system.
The temperatures become more uniform. When the temperatures are uniform, you
cannot use the temperature in order to do useful work.

.. I now notice that I missed that you mentioned putting things into orbit?

I misunderstood and thought you meant putting the seebeck stuff in the ocean,
as if that would cool down the oceans.

Yeah, if you pump heat into places that you can remove from earth, or have
emit black body radiation more effectively, that would help.

But, Unless you are ejecting stuff away from earth, there is still a max rate
you can radiate away heat at a given temperature? Oh, but, hm, if you made
your thing in orbit really really hot, hm.

Is that what you were saying?

Sorry for misunderstanding what you meant about the ocean.

~~~
cerealbad
i did mean the ocean originally, you have heat sponges which sit near the
surface and use the gradient between air flowing above the surface, the hotter
temperature above, and the cooler temperature of the ocean. the sponges can
use the heat to move or they can trap it like charging a battery so you
transform heat into kinetic or chemical energy. it occurred to me that a third
way is to build a ring that uses the heat exchange between the layers of the
atmosphere and space, using the same ectothermic biological principle.

talking about the earth as a system here is a bit of a misnomer. the core up
to the mantle is very hot, but that heat only escapes to the surface through
lava tubes/vents because the tectonic plates are good insulators. im
specifically talking about the part of the earth we care about affecting the
temperature of - and you can do this by shifting the heat up, down, storing it
or converting it. the atmosphere is more permissive than the hydrosphere,
hadal zone or crust.

it's easier to imagine the earth as a ball and things leaving the surface as
exiting the ball system. but really when we talk about the earth it's more
like a layer on a ball, and if you go deep into the ocean, underground or exit
the atmosphere it's all the same type of thing.

as far as i know the climate cycles are a surface feature of the planet, deep
underground is more inaccessible to our technology than reaching another star
system.

the term is called geosequestration.

~~~
drdeca
I had thought you meant sponges at the bottom of the ocean.

Not sure what you mean by storing heat.

You could store energy obtained from (the smoothing-out of) a temperature
gradient, but that isn’t storing the heat, just the energy extracted as the
temperature gradient goes away. It doesn’t decrease the amount of heat?

And I suppose if you have some endothermic reaction (like melting ice) you can
decrease the amount of heat around, (and then if you freeze it again, you
release the heat), which is sort of like storing heat, but it isn’t like you
can store arbitrarily large amounts of heat this way. You would need
arbitrarily large amounts of stuff to have react.

I’m still fairly sure you cannot “transform heat into kinetic or chemical
energy”, but rather, you can transform a difference in temperatures, and a
potential for heat to be exchanged, into kinetic or chemical or whatever
energy?

In the example of that mechanism for converting a temperature gradient into
electricity, suppose you had two regions with particular and different initial
temperatures , which are in contact with opposite sides of the mechanism. The
two regions have the same mass and are made of the same material. How do you
expect the temperature of all the parts after reaching equilibrium to depend
on the initial temperature? I expect that the total heat will remain the same
(even though you did extract some energy as the difference in temperatures
went away).

Also, pumping heat around costs energy. To move things against the tendency
for temperatures to equalize, costs energy, right?

I don’t understand why the fact that earth is not homogeneous would be a
reason to not call it a system?

I don’t see how the specifics of geology and such are relevant here. The
question is: under what circumstances can we keep the part of a system that we
care about to stay at a low temperature while waste heat is being added to the
system at an arbitrarily fast rate, and the only way we have for heat to leave
the system is blackbody radiation? (Assuming the system is
connected/contiguous and stuff)

Now it sounds like you are suggesting that we just make the inside of the
earth hotter while keeping our part cool?

------
jammygit
I just want to say that this discussion is a charming read so far (the salad
just arrived - I can’t wait!)

