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The single most important assumption in this paper is that energy consumption will increase by 2% per year. This kind of exponential growth leads to outlandish

by blake1 3y ago

The single most important assumption in this paper is that energy consumption will increase by 2% per year. This kind of exponential growth leads to outlandish estimates for the amount of tidal energy that society will demand. Energy consumption has decoupled from population growth rates and economic growth. How much energy will we consume in 1,000 years? Most projections of the population have it stabilizing at around 15 billion. But continuing at its current growth rate (an optimistic assumption I think), gets us to about 150 trillion humans in 1,000 years. And at 2% growth rate, each of those humans will consume 20,000 times more energy than a circa 2023 human. Now state of the art technology wastes about 80% of the energy consumed, so this is equivalent to 100,000 times more useful energy consumed per human. So the physics in this page is a good examination of the surprisingly large compounding effects of unchecked exponential growth.

bobthepanda 3y ago
The UN has revised peak projections down several times; the peak is now expected at 10 billion.
- coldcode 3y ago
  More countries are now sub-2.0 replacement, China is down to 1.09 so the peak is unlikely to get much more than that.
  - popol12 3y ago
    A Google search for “china children per woman” gives me 1.705 Are you talking about something else ?
    - paulmd 3y ago
      Leave it to HN to be unaware of the physical or social mechanics of reproduction
    - happymellon 3y ago
      Normally it requires two people to make a baby. So 1.7 is less than the number of people requires to create it. Rates are normally calculated by couples. 0.85 per person is a decline.
    - smcin 3y ago
      The Google hit China TFR 1.705 for 2023 is bogus (and 2023 isn't even over yet, which should have alerted you), it's single-sourced from macrotrends.net which is quoting an old (pre-pandemic) UN forecast; you can see from their graph their (forecasted) numbers for 2020-2 turned out totally wrong. Lots of other sites are quoting the Google and macrotrends as fact. So now the #1 Google hit on that is misinformation. (Always look for attributions and dates). As to 2022, China did briefly drop to a TFR of 1.09, like GP said [1]; but the moving average over several years is more like 1.3. You have to put the 2022 drop in context that their very strict lockdown went into its third year, and there were two cases of pregnant women losing their babies e.g. because the hospital denied them entry for having negative Covid tests but a few hours too old [2]. [0]: https://www.macrotrends.net/countries/CHN/china/fertility-rate https://www.macrotrends.net/countries/CHN/china/fertility-ra... [1]: "China's fertility rate drops to record low 1.09 in 2022- state media" https://www.reuters.com/world/china/chinas-fertility-rate-drops-record-low-109-2022-state-media-2023-08-15/ https://www.reuters.com/world/china/chinas-fertility-rate-dr... [2]: https://fortune.com/2022/01/07/china-covid-cases-miscarriage-xian-lockdown/ https://fortune.com/2022/01/07/china-covid-cases-miscarriage...
      - anonylizard 3y ago
        Its now dropping even lower in 2023, long after the lockdowns have ended. Turns out the East Asian style of hyper-competitive child rearing has its downsides, namely the high costs dissuade parents from having children altogether. China faces every antinatal problem the west does, except far worse. 1. Extremely high housing prices making family formation expensive 2. Small apartments suppress large family formation (Seen in Europe) 3. General collapse of marriage rates due to changing incentives and thus moral norms 4. Higher education decreasing fertile years. 5. Economic depression, especially for young people, euro debt crisis level of youth unemployment. You add to that, that China still officially has a 3-child policy (not that many people even have 2), because the birth control bureaucrats still need a job. China is probably 2nd lowest in the world behind South Korea, and will stay there, if not
        bobthepanda 3y ago
        Education is even worse than that. Education itself is highly competitive even down to the pre-K level in some places.
    - istjohn 3y ago
      I suppose that would be replacement rate if there were 42% more women than men in China. But according to Wikipedia there actually 4.5% more men than women.
  - ido 3y ago
    You mean less than that? But more importantly, after that peak comes a long and steady decline (as far as we can tell).
  - jl6 3y ago
    The trends are mostly encouraging but there are still 102 countries with a fertility rate above replacement rate, so we’re not out of the woods yet: https://en.wikipedia.org/wiki/List_of_countries_by_total_fertility_rate https://en.wikipedia.org/wiki/List_of_countries_by_total_fer...
    - XorNot 3y ago
      Unless those countries have increasingly western lifestyles, stable political systems and growing economies, then it actually doesn't matter. The grim reality is that all those places have substantial modifiers on their death rates, and aren't exporting their increasing population to the world in any meaningful way. We know from experience that if those places actually started to improve, then the birth rate would drop precipitously.
    - crote 3y ago
      2.1 is the replacement rate for well-developed countries. It does not apply universally to all countries. For example, the US had a fertility rate of 7.0(!) in 1800 and saw no significant population growth due to births because most of those kids died well before reaching the age of reproduction. Historically, fertility rates have always dropped once basic standards of living have managed to get rid of excess child mortality.
- quotemstr 3y ago
  Almost every human population is under strong selection pressure towards having more people. This dip in fertility cannot and will not last.
  - deepsun 3y ago
    Unless external factors kick in, like depletion of resources and soils. There's no any law of nature that says homo sapiens must be able to survive. Smaller scale examples are: 1. Easter island -- we, humans, deforested the island, that degraded and depleted human population significantly even before the first european ships discovered the island. From what I've heard, "Rapa Nui" movie is unusually historically correct on the events. 2. St. Matthew Island -- 29 introduced reindeer rapidly overpopulated the island and ate all the available food there, so the whole population died. Same thing can happen on planet Earth.
    - mullingitover 3y ago
      > Easter island -- we, humans, deforested the island, that degraded and depleted human population significantly even before the first european ships discovered the island. More recent research shows that this is probably not true - there's evidence that the population was growing right up until the arrival of Europeans[1]. [1] https://www.sciencedaily.com/releases/2021/07/210713090153.htm https://www.sciencedaily.com/releases/2021/07/210713090153.h...
  - istjohn 3y ago
    The future is Amish
  - crote 3y ago
    Then why aren't people in countries with plenty of resources breeding like rabbits and are we actually seeing a decrease in fertility once people get access to proper healthcare and sufficient food? It is almost like humans are not mindless animals who solely reproduce because of biological urges or something.
RetroTechie 3y ago
> The single most important assumption in this paper is that energy consumption will increase by 2% per year. There's a 2nd big assumption: That tidal energy extracted is additional Earth's rotational energy loss above what Earth does by itself. According to the paper, tidal energy is dissipated through friction between ocean water & the seafloor. This dissipated energy subtracts from Earth's rotational energy. And some rotational energy is transferred to the moon (which makes the moon move further out). Ok so far. Author's 2nd assumption is that as tidal energy is tapped, this is extra energy that subtracts from Earth's rotation. But is it? It might also be that tidal energy extracted by humans, comes out of some fixed 'budget', and the remainder is dissipated naturally. More tidal energy extracted by humans -> less tidal energy dissipated through ocean vs. seafloor friction. Kind of like solar influx: it's a huge but (apart from fluctuations) fixed amount. We can tap some % of that potential, but what's available doesn't increase. And what humans don't tap, gets absorbed / radiated out by other natural processes. I won't even hazard a guess. But it would be interesting to figure out which of those applies.
- pmontra 3y ago
  Your observation seems to make sense. Intuitively, if we extract energy from the tides, tides will be less tall and the speed of water will be smaller. Ocean currents will slow down too. What I don't know is, less friction on the seafloor means that we would actually make Earth slow down less faster than it would do if left alone?
  - Interloper2099 3y ago
    It’s a bit odd to extrapolate to this level. It’s like thinking, yes, I can set one tree on fire and release energy, but look how crazy it is if all the trees in North America burn at once!! And currents are also affected by the rotation of the Earth, temp differences, and salinity differences so they might not change dramatically.
- ricardobeat 3y ago
  Yes, the assumption seems to be that any energy extracted is in addition to the friction with the ocean floor and continental plates, as those will continue to exist.
api 3y ago
20000X the energy of a current human shows how absurd it would be for growth and energy use to not decouple. I can’t even imagine what I could do on Earth using that much power. Fly my own 737 to a new city every day? I suppose spacefaring humans might use that kind of power but if they are living in space they are no longer part of the biosphere of Earth.
- ben_w 3y ago
  > I can’t even imagine what I could do on Earth using that much power. Fly my own 737 to a new city every day? Sure, why not? It's absurd today for the average person, but it's the kind of thing rich people get to do already, and looking at the rich today is a decent (though imperfect because inflation and invention don't work like that) hint for what normal people can afford in a richer future.
  - mattmaroon 3y ago
    Aviation historically, has not gotten cheaper overtime. If anything, it is more expensive. Only rich people had planes 100 years ago and only rich people own them now and the trend line doesn’t indicate it’ll be different in another hundred.
    - deleted 3y ago
      [deleted]
    - ben_w 3y ago
      Nobody owned a 747 a hundred years ago. Cheapest flight I've ever taken was 9.99 from Berlin to London — not sure if pounds or euros, but does it matter when either way it is less than I used to spend on a week of school lunches nearly 20 years earlier?
      - paulryanrogers 3y ago
        Exceptions like 10 EUR flights aren't sustainable. They're just auctioning off empty seats to cut costs. The comparison was conceptual thing to similar thing. Only the rich own and operate private planes, that hasn't changed. The fact that other, more sophisticated planes exist doesn't undermine the point. There are also diminishing returns. And past leaps in lifestyles aren't guaranteed to continue the same trends, and can reverse. The earth has seen several major extinction events. Arguably humans are the cause of the latest one. Doubtful we can sustain billions of us without an ecological system to produce our bare necessities, certainly not enough for a full life.
codethief 3y ago
> The single most important assumption in this paper is that energy consumption will increase by 2% per year. […] How much energy will we consume in 1,000 years I keep posting this link here on HN but, once again, it seems very appropriate: > The upshot is that at a 2.3% growth rate (conveniently chosen to represent a 10× increase every century), we would reach boiling temperature in about 400 years. https://dothemath.ucsd.edu/2012/04/economist-meets-physicist/ https://dothemath.ucsd.edu/2012/04/economist-meets-physicist...
- casparvitch 3y ago
  If HN was reading Murphy the front page would look very different every day
- joak 3y ago
  This boiling temperature conclusion makes the assumption that we continue using thermal power (steam engines, etc...), where waste heat is around 60%. However photovoltaic and wind does not produce much waste heat. Arguably solar and wind cannot scale 1000x but then you could have non thermal fusion like Helion's https://www.helionenergy.com/technology/ https://www.helionenergy.com/technology/. Btw, thermal power is already showing limits (rivers overheating in summers), we don't have to wait 400 years to see its failure.
  - midasuni 3y ago
    Where does the energy go then? EM radiation leaving the planet?
    - joak 3y ago
      Chemical energy. Like the plants, they take sun energy and store it as chemical energy. We could do the same, take CO2 and water and make CH4 and oxygen (electrolysis + Sabatier reaction) and make plastic. Or take ore, aluminum oxide and iron oxide, and "unburn" them releasing again oxygen (we already do that) etc... We mostly use energy to manufacture things. Life takes energy and lowers the entropy of the planet. Why shouldn't humans able to do the same? Any technical reason?
deleted 3y ago
[deleted]
svnt 3y ago
> gets us to about 150 trillion humans in 1,000 years I realize the big issue is settled here but just to scope this detail: the total land area of earth is coincidentally approximately 150 million km^2 At 150 trillion humans each human would get just about a square meter. Many of those square meters are uninhabitable.
- midasuni 3y ago
  That’s about the density of Kowloon walled city. And ignores the available space in the ocean.
  - woobar 3y ago
    Did they grow any food, produce electricity, or had any manufacturing at all in Kowloon?
    - throwaway2037 3y ago
      To be clear, "Kowloon" is different from "Kowloon Walled City". And, yes, they did have very small manufacturing inside. I highly recommend that you find a copy of this (in)famous book about it: << City of Darkness>> (https://cityofdarkness.co.uk https://cityofdarkness.co.uk).
- deleted 3y ago
  [deleted]
dredmorbius 3y ago
The lesson that constant percentage (that is, exponential) growth cannot continue endlessly is the fundamental message behind the concept of Limits to Growth. That is, there exist intractable limits to growth, and that no matter how convenient it may be to pretend otherwise, humans ignore this fact at their extreme peril. Long-term ongoing economic growth, expressed as a constant percentage, is baked in to most current orthodox economics and economic policy. Even apparent mavericks such as Thomas Piketty assume that growth will continue interminably (noted in Capital in the Twenty-First Century). Rather than being a critique of Liu, you've actually written a criticism of those he himself is generally addressing.
- xg15 3y ago
  I think there is one escape from this, basically confining more and more "growth" to artificial numbers on paper (or in a DB). Cryptocurrencies are kind of going in that direction, where the "value" that is reported as economic growth doesn't correspond to any kind of real-world matter or activity, but is simply assigned to some specific group of bits. I can kind of believe that this virtual kind of growth could continue a long time without boiling the planet, but of course that doesn't make things less absurd, as the "value" would represent nothing objectively useful and would have to be maintained artificially - either through scarcity mechanisms like PoW etc, or through locked-down devices and ecosystems. So that kind of "growth" could go on forever without burning the planet but would probably be a step back for civilization.
  - dredmorbius 3y ago
    The problem with this, or any other hypothetical "decoupled growth" argument is that, well, it's purely hypothetical. There's no evidence whatsoever that economic growth can be decoupled from resource, and most especially energy, usage. There are instances of increased efficiencies, which thanks to the Jevons Paradox increase overall resource utilisation (economically, efficiency is equivalent to a reduced price, and hence induces greater demand). And there are instances of outsourced resource utilisation (both in terms of inputs and of waste sinks), most notably that of China which has committed tremendous domestic resources and incurred immense environmental insult in providing "cheap goods" (that is: goods lacking fully-costed externality impacts) to developed countries. But there's nary a trace of actual empirical evidence of substantive decoupling in the real world. Much handwaving and could-be's, however.
cryptonector 3y ago
With this analysis no energy source is renewable, and we'd even run out of sunlight (or surface area that can be dedicated to solar power anyways, or see demand exceed solar power were we to put solar panels on every square inch of the planet's surface). In reality we're already certain to hit a population maximum in just two+ decades, and not only that but the world is very likely to be on a negative population growth curve after that for some time. And we're going to need some new tech revolution to drive energy demand in developed countries up much more than it is, and the developing world's per-capita demand will not likely exceed the developed world's once fully developed. I.e., we're not growing forever, the end of population growth is around the corner, and the end of energy demand growth is not much further.
- fostware 3y ago
  [flagged]
ChuckMcM 3y ago
Extrapolation is always a bad thing :-). That said, this guy has some interesting thoughts. Of course he misses out that if you pump the tides you can speed up the rotation of the earth and thus "renew" the lag (think moving your legs while swinging). Similarly solar isn't renewable because at some point the Sun is going to run out of hydrogen, and if you made a dyson sphere to capture all of the Sun's energy you would wipe out life on earth.
georgeecollins 3y ago
15 billion as a stabilized population of the Earth is actually a very high estimate. Some estimate the curve will flatten at 10.5bn. But it is all a prediction, so who knows. https://en.wikipedia.org/wiki/Projections_of_population_growth https://en.wikipedia.org/wiki/Projections_of_population_grow...
sidewndr46 3y ago
If you assume 2% increase per year, anything is irrelevant. Nothing can allow humanity to sustain unbounded energy growth on a single planet.
solalf 3y ago
Peak human population is expected to reach 10.4B in 2084 and slowly decrease from there. This is according to the UN[1] but other estimates envision a much earlier peak by the 2040s at 8.5B followed by a sharp drop to 6B by the end of the century[2]. [1] https://www.un.org/en/global-issues/population https://www.un.org/en/global-issues/population [2] https://earth4all.life/news/press-release-global-population-could-peak-below-9-billion-in-2050s/ https://earth4all.life/news/press-release-global-population-...
deleted 3y ago
[deleted]
bufferoverflow 3y ago
1000 years is a loooong time. It's entirely plausible to have trillions of humans, if we create conditions for that. And not only on Earth. For that to happen we need almost complete automation, which would provide cheap food, cheap housing, cheap healthcare, and lack of worry about the immediate future. Even if you can sustain 1% increase in population per year, 1000 years of prosperity will result in (8 billion)*(1.01^1000) = 167673 billion = 167 trillion people (1% is roughly the current population growth, but it's slowing down)

by blake1 3y ago

bobthepanda 3y ago

The UN has revised peak projections down several times; the peak is now expected at 10 billion.

coldcode 3y ago
More countries are now sub-2.0 replacement, China is down to 1.09 so the peak is unlikely to get much more than that.
- popol12 3y ago
  A Google search for “china children per woman” gives me 1.705 Are you talking about something else ?
  - paulmd 3y ago
    Leave it to HN to be unaware of the physical or social mechanics of reproduction
  - happymellon 3y ago
    Normally it requires two people to make a baby. So 1.7 is less than the number of people requires to create it. Rates are normally calculated by couples. 0.85 per person is a decline.
  - smcin 3y ago
    The Google hit China TFR 1.705 for 2023 is bogus (and 2023 isn't even over yet, which should have alerted you), it's single-sourced from macrotrends.net which is quoting an old (pre-pandemic) UN forecast; you can see from their graph their (forecasted) numbers for 2020-2 turned out totally wrong. Lots of other sites are quoting the Google and macrotrends as fact. So now the #1 Google hit on that is misinformation. (Always look for attributions and dates). As to 2022, China did briefly drop to a TFR of 1.09, like GP said [1]; but the moving average over several years is more like 1.3. You have to put the 2022 drop in context that their very strict lockdown went into its third year, and there were two cases of pregnant women losing their babies e.g. because the hospital denied them entry for having negative Covid tests but a few hours too old [2]. [0]: https://www.macrotrends.net/countries/CHN/china/fertility-rate https://www.macrotrends.net/countries/CHN/china/fertility-ra... [1]: "China's fertility rate drops to record low 1.09 in 2022- state media" https://www.reuters.com/world/china/chinas-fertility-rate-drops-record-low-109-2022-state-media-2023-08-15/ https://www.reuters.com/world/china/chinas-fertility-rate-dr... [2]: https://fortune.com/2022/01/07/china-covid-cases-miscarriage-xian-lockdown/ https://fortune.com/2022/01/07/china-covid-cases-miscarriage...
    - anonylizard 3y ago
      Its now dropping even lower in 2023, long after the lockdowns have ended. Turns out the East Asian style of hyper-competitive child rearing has its downsides, namely the high costs dissuade parents from having children altogether. China faces every antinatal problem the west does, except far worse. 1. Extremely high housing prices making family formation expensive 2. Small apartments suppress large family formation (Seen in Europe) 3. General collapse of marriage rates due to changing incentives and thus moral norms 4. Higher education decreasing fertile years. 5. Economic depression, especially for young people, euro debt crisis level of youth unemployment. You add to that, that China still officially has a 3-child policy (not that many people even have 2), because the birth control bureaucrats still need a job. China is probably 2nd lowest in the world behind South Korea, and will stay there, if not
      - bobthepanda 3y ago
        Education is even worse than that. Education itself is highly competitive even down to the pre-K level in some places.
  - istjohn 3y ago
    I suppose that would be replacement rate if there were 42% more women than men in China. But according to Wikipedia there actually 4.5% more men than women.
- ido 3y ago
  You mean less than that? But more importantly, after that peak comes a long and steady decline (as far as we can tell).
- jl6 3y ago
  The trends are mostly encouraging but there are still 102 countries with a fertility rate above replacement rate, so we’re not out of the woods yet: https://en.wikipedia.org/wiki/List_of_countries_by_total_fertility_rate https://en.wikipedia.org/wiki/List_of_countries_by_total_fer...
  - XorNot 3y ago
    Unless those countries have increasingly western lifestyles, stable political systems and growing economies, then it actually doesn't matter. The grim reality is that all those places have substantial modifiers on their death rates, and aren't exporting their increasing population to the world in any meaningful way. We know from experience that if those places actually started to improve, then the birth rate would drop precipitously.
  - crote 3y ago
    2.1 is the replacement rate for well-developed countries. It does not apply universally to all countries. For example, the US had a fertility rate of 7.0(!) in 1800 and saw no significant population growth due to births because most of those kids died well before reaching the age of reproduction. Historically, fertility rates have always dropped once basic standards of living have managed to get rid of excess child mortality.
quotemstr 3y ago
Almost every human population is under strong selection pressure towards having more people. This dip in fertility cannot and will not last.
- deepsun 3y ago
  Unless external factors kick in, like depletion of resources and soils. There's no any law of nature that says homo sapiens must be able to survive. Smaller scale examples are: 1. Easter island -- we, humans, deforested the island, that degraded and depleted human population significantly even before the first european ships discovered the island. From what I've heard, "Rapa Nui" movie is unusually historically correct on the events. 2. St. Matthew Island -- 29 introduced reindeer rapidly overpopulated the island and ate all the available food there, so the whole population died. Same thing can happen on planet Earth.
  - mullingitover 3y ago
    > Easter island -- we, humans, deforested the island, that degraded and depleted human population significantly even before the first european ships discovered the island. More recent research shows that this is probably not true - there's evidence that the population was growing right up until the arrival of Europeans[1]. [1] https://www.sciencedaily.com/releases/2021/07/210713090153.htm https://www.sciencedaily.com/releases/2021/07/210713090153.h...
- istjohn 3y ago
  The future is Amish
- crote 3y ago
  Then why aren't people in countries with plenty of resources breeding like rabbits and are we actually seeing a decrease in fertility once people get access to proper healthcare and sufficient food? It is almost like humans are not mindless animals who solely reproduce because of biological urges or something.

RetroTechie 3y ago

> The single most important assumption in this paper is that energy consumption will increase by 2% per year. There's a 2nd big assumption: That tidal energy extracted is additional Earth's rotational energy loss above what Earth does by itself. According to the paper, tidal energy is dissipated through friction between ocean water & the seafloor. This dissipated energy subtracts from Earth's rotational energy. And some rotational energy is transferred to the moon (which makes the moon move further out). Ok so far. Author's 2nd assumption is that as tidal energy is tapped, this is extra energy that subtracts from Earth's rotation. But is it? It might also be that tidal energy extracted by humans, comes out of some fixed 'budget', and the remainder is dissipated naturally. More tidal energy extracted by humans -> less tidal energy dissipated through ocean vs. seafloor friction. Kind of like solar influx: it's a huge but (apart from fluctuations) fixed amount. We can tap some % of that potential, but what's available doesn't increase. And what humans don't tap, gets absorbed / radiated out by other natural processes. I won't even hazard a guess. But it would be interesting to figure out which of those applies.

pmontra 3y ago
Your observation seems to make sense. Intuitively, if we extract energy from the tides, tides will be less tall and the speed of water will be smaller. Ocean currents will slow down too. What I don't know is, less friction on the seafloor means that we would actually make Earth slow down less faster than it would do if left alone?
- Interloper2099 3y ago
  It’s a bit odd to extrapolate to this level. It’s like thinking, yes, I can set one tree on fire and release energy, but look how crazy it is if all the trees in North America burn at once!! And currents are also affected by the rotation of the Earth, temp differences, and salinity differences so they might not change dramatically.
ricardobeat 3y ago
Yes, the assumption seems to be that any energy extracted is in addition to the friction with the ocean floor and continental plates, as those will continue to exist.

api 3y ago

20000X the energy of a current human shows how absurd it would be for growth and energy use to not decouple. I can’t even imagine what I could do on Earth using that much power. Fly my own 737 to a new city every day? I suppose spacefaring humans might use that kind of power but if they are living in space they are no longer part of the biosphere of Earth.

ben_w 3y ago
> I can’t even imagine what I could do on Earth using that much power. Fly my own 737 to a new city every day? Sure, why not? It's absurd today for the average person, but it's the kind of thing rich people get to do already, and looking at the rich today is a decent (though imperfect because inflation and invention don't work like that) hint for what normal people can afford in a richer future.
- mattmaroon 3y ago
  Aviation historically, has not gotten cheaper overtime. If anything, it is more expensive. Only rich people had planes 100 years ago and only rich people own them now and the trend line doesn’t indicate it’ll be different in another hundred.
  - deleted 3y ago
    [deleted]
  - ben_w 3y ago
    Nobody owned a 747 a hundred years ago. Cheapest flight I've ever taken was 9.99 from Berlin to London — not sure if pounds or euros, but does it matter when either way it is less than I used to spend on a week of school lunches nearly 20 years earlier?
    - paulryanrogers 3y ago
      Exceptions like 10 EUR flights aren't sustainable. They're just auctioning off empty seats to cut costs. The comparison was conceptual thing to similar thing. Only the rich own and operate private planes, that hasn't changed. The fact that other, more sophisticated planes exist doesn't undermine the point. There are also diminishing returns. And past leaps in lifestyles aren't guaranteed to continue the same trends, and can reverse. The earth has seen several major extinction events. Arguably humans are the cause of the latest one. Doubtful we can sustain billions of us without an ecological system to produce our bare necessities, certainly not enough for a full life.

codethief 3y ago

> The single most important assumption in this paper is that energy consumption will increase by 2% per year. […] How much energy will we consume in 1,000 years I keep posting this link here on HN but, once again, it seems very appropriate: > The upshot is that at a 2.3% growth rate (conveniently chosen to represent a 10× increase every century), we would reach boiling temperature in about 400 years. https://dothemath.ucsd.edu/2012/04/economist-meets-physicist/ https://dothemath.ucsd.edu/2012/04/economist-meets-physicist...

casparvitch 3y ago
If HN was reading Murphy the front page would look very different every day
joak 3y ago
This boiling temperature conclusion makes the assumption that we continue using thermal power (steam engines, etc...), where waste heat is around 60%. However photovoltaic and wind does not produce much waste heat. Arguably solar and wind cannot scale 1000x but then you could have non thermal fusion like Helion's https://www.helionenergy.com/technology/ https://www.helionenergy.com/technology/. Btw, thermal power is already showing limits (rivers overheating in summers), we don't have to wait 400 years to see its failure.
- midasuni 3y ago
  Where does the energy go then? EM radiation leaving the planet?
  - joak 3y ago
    Chemical energy. Like the plants, they take sun energy and store it as chemical energy. We could do the same, take CO2 and water and make CH4 and oxygen (electrolysis + Sabatier reaction) and make plastic. Or take ore, aluminum oxide and iron oxide, and "unburn" them releasing again oxygen (we already do that) etc... We mostly use energy to manufacture things. Life takes energy and lowers the entropy of the planet. Why shouldn't humans able to do the same? Any technical reason?

deleted 3y ago

[deleted]

svnt 3y ago

> gets us to about 150 trillion humans in 1,000 years I realize the big issue is settled here but just to scope this detail: the total land area of earth is coincidentally approximately 150 million km^2 At 150 trillion humans each human would get just about a square meter. Many of those square meters are uninhabitable.

midasuni 3y ago
That’s about the density of Kowloon walled city. And ignores the available space in the ocean.
- woobar 3y ago
  Did they grow any food, produce electricity, or had any manufacturing at all in Kowloon?
  - throwaway2037 3y ago
    To be clear, "Kowloon" is different from "Kowloon Walled City". And, yes, they did have very small manufacturing inside. I highly recommend that you find a copy of this (in)famous book about it: << City of Darkness>> (https://cityofdarkness.co.uk https://cityofdarkness.co.uk).
deleted 3y ago
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dredmorbius 3y ago

The lesson that constant percentage (that is, exponential) growth cannot continue endlessly is the fundamental message behind the concept of Limits to Growth. That is, there exist intractable limits to growth, and that no matter how convenient it may be to pretend otherwise, humans ignore this fact at their extreme peril. Long-term ongoing economic growth, expressed as a constant percentage, is baked in to most current orthodox economics and economic policy. Even apparent mavericks such as Thomas Piketty assume that growth will continue interminably (noted in Capital in the Twenty-First Century). Rather than being a critique of Liu, you've actually written a criticism of those he himself is generally addressing.

xg15 3y ago
I think there is one escape from this, basically confining more and more "growth" to artificial numbers on paper (or in a DB). Cryptocurrencies are kind of going in that direction, where the "value" that is reported as economic growth doesn't correspond to any kind of real-world matter or activity, but is simply assigned to some specific group of bits. I can kind of believe that this virtual kind of growth could continue a long time without boiling the planet, but of course that doesn't make things less absurd, as the "value" would represent nothing objectively useful and would have to be maintained artificially - either through scarcity mechanisms like PoW etc, or through locked-down devices and ecosystems. So that kind of "growth" could go on forever without burning the planet but would probably be a step back for civilization.
- dredmorbius 3y ago
  The problem with this, or any other hypothetical "decoupled growth" argument is that, well, it's purely hypothetical. There's no evidence whatsoever that economic growth can be decoupled from resource, and most especially energy, usage. There are instances of increased efficiencies, which thanks to the Jevons Paradox increase overall resource utilisation (economically, efficiency is equivalent to a reduced price, and hence induces greater demand). And there are instances of outsourced resource utilisation (both in terms of inputs and of waste sinks), most notably that of China which has committed tremendous domestic resources and incurred immense environmental insult in providing "cheap goods" (that is: goods lacking fully-costed externality impacts) to developed countries. But there's nary a trace of actual empirical evidence of substantive decoupling in the real world. Much handwaving and could-be's, however.

cryptonector 3y ago

With this analysis no energy source is renewable, and we'd even run out of sunlight (or surface area that can be dedicated to solar power anyways, or see demand exceed solar power were we to put solar panels on every square inch of the planet's surface). In reality we're already certain to hit a population maximum in just two+ decades, and not only that but the world is very likely to be on a negative population growth curve after that for some time. And we're going to need some new tech revolution to drive energy demand in developed countries up much more than it is, and the developing world's per-capita demand will not likely exceed the developed world's once fully developed. I.e., we're not growing forever, the end of population growth is around the corner, and the end of energy demand growth is not much further.

fostware 3y ago
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ChuckMcM 3y ago

Extrapolation is always a bad thing :-). That said, this guy has some interesting thoughts. Of course he misses out that if you pump the tides you can speed up the rotation of the earth and thus "renew" the lag (think moving your legs while swinging). Similarly solar isn't renewable because at some point the Sun is going to run out of hydrogen, and if you made a dyson sphere to capture all of the Sun's energy you would wipe out life on earth.

georgeecollins 3y ago

15 billion as a stabilized population of the Earth is actually a very high estimate. Some estimate the curve will flatten at 10.5bn. But it is all a prediction, so who knows. https://en.wikipedia.org/wiki/Projections_of_population_growth https://en.wikipedia.org/wiki/Projections_of_population_grow...

sidewndr46 3y ago

If you assume 2% increase per year, anything is irrelevant. Nothing can allow humanity to sustain unbounded energy growth on a single planet.

solalf 3y ago

Peak human population is expected to reach 10.4B in 2084 and slowly decrease from there. This is according to the UN[1] but other estimates envision a much earlier peak by the 2040s at 8.5B followed by a sharp drop to 6B by the end of the century[2]. [1] https://www.un.org/en/global-issues/population https://www.un.org/en/global-issues/population [2] https://earth4all.life/news/press-release-global-population-could-peak-below-9-billion-in-2050s/ https://earth4all.life/news/press-release-global-population-...

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bufferoverflow 3y ago

1000 years is a loooong time. It's entirely plausible to have trillions of humans, if we create conditions for that. And not only on Earth. For that to happen we need almost complete automation, which would provide cheap food, cheap housing, cheap healthcare, and lack of worry about the immediate future. Even if you can sustain 1% increase in population per year, 1000 years of prosperity will result in (8 billion)*(1.01^1000) = 167673 billion = 167 trillion people (1% is roughly the current population growth, but it's slowing down)