Energy, the collapse of the Western Roman Empire, and of the modern society.

The collapse of Western Roman Empire is a very classic topic among scholars of history, politics, economy, etc. Joseph Tainter had a theory, based on complexity and energy management. 

If you have time, you can watch this lecture by Joseph, it's a fun and somber talk about the collapse of Western Roman Empire from his perspective. I also read the book The Collapse of Complex Societies, which elaborates his theory of social collapse with more examples than just the Western Roman Empire, including the Mayan Empire and Chacoan civilization.

The Collapse of Western Roman Empire

In the early days of Western Roman Empire/Roman Republic, it conquered a lot of new lands. Each conquest was easy, and brought great loots. The Romans used the loot to increase their wealth and power and social complexity. 

Some complexities were voluntary: they wanted to enjoy life. Some complexities were forced on them: they needed it to keep their growing republic/empire in order. These complexities were mostly in the forms of bureaucracies and law codes.

Eventually, the conquests ground to a halt: its borders reached the Germanic, Persian, Briton, and so on, countries that were either too powerful to conquer or too poor and distant to worth conquering. Rome went from conquest mode to farming mode. This placed a great burden on the empire: the economy and culture used to run on conquests, but now it has to run on farming.

These two ways of life are fundamentally different in how they use energy: farming is basically eating energy from the sun, given year by year, while conquering is eating energy from other people's farming, accumulated for centuries and obtained all at once.

To fix the energy problem, the empire increased in complexity, by methods like more bureaucracy, more taxes, more social administrations, more currency manipulations (I laughed at how much they shaved the coins so it became worthless in the end). But complexity requires energy too, and the Western Roman Empire became more and more precarious. 

We can quantify the precariousness of the empire by 

$$\text{precariousness} = p = \frac{\text{energy use}}{\text{energy production}}$$

It's basically the opposite of saving rate. If $p=1$, it means it has no reserves: it eats exactly how much it makes. If $p < 1$, it has reserves and can deal with emergency uses. If $p > 1$, it's running at a loss.

The higher $p$ is, the less it can afford to deal with emergencies. As the empire became more complex, $p$ grew, it became more precarious and brittle, and eventually, it just couldn't deal with the emergencies (big empires are always in one emergency or another!) and collapsed.

The collapse of complex societies in general is similar: The basic economic idea of diminishing returns applies to society's complexity, too. Societies are ways of managing materials and energy, and it faces problems in managing. In solving them, complexity usually grows.

But complexity requires energy too, so growing complexity is always a balancing act: solving problems gives the society more access to energy, but the solution itself costs energy. This can be written as another formula:
$$\text{marginal productivity of complexity} = \frac{d\text{(benefit of complexity)}}{d\text{(cost of complexity)}} - 1$$

As a general rule (can be explained by algorithmic complexity theory, really, but that's for another day), the most fundamental ideas, the most simplest discoveries, and the earliest achievements, tend to be the same. Rutherford discovered nucleus with a homemade desktop device, while hundreds of CERN physicists discovered the Higgs boson with a gigantic ring that took 10 years and $\$1e10$ to build!

Those were simpler days...

As a result, the marginal productivity of complexity drops as people keep pushing through a conventional field. That is why going into new fields instead of mature fields is good, and why few modern mathematicians are specialized in classical analysis or geometry, and few modern physicists are specialized in Newtonian physics.

Complexity tends to grow, old laws are rarely taken away (just think of the common law system... 800 years of layers upon layers of laws!), and they tend to grow faster than energy income. When complexity grows so much that it eats a significant amount of energy income, the society would have little reserve to deal with emergencies, and would soon collapse when it fails to solve problems.

Wait But Why

Wait But Why is a blog that explains interesting things in very simple and still accurate enough language, sometimes with badly drawn comics.

The philosophy of WBW is that, knowledge is a tree, with basics like philosophy, physics, and mathematics in the trunk/root, specialized versions like chemistry, astronomy, ethics on the branch, and so on, all the way to the leaves, which are the complicated topics. To understand and remember the leaves, the trunks must be understood first.

Like this:

I will comment on two posts, both about how our society uses energy, and the problems with it. I will only comment on them without explaining them, since they are already written as simply as possible.

Why is my laptop on?

This post traces back the electricity from the laptop all the way back to gravity and nuclear fusion, in amusingly bad comics.

For completeness, it should have stated that chemosynthesis, as well as geothermal energy, ultimately come from the stars too. As Carl Sagan said, we are all star stuff.

Most of geothermal comes from radiogenic energy, fission from earth, which comes from uranium and stuff, which are elements synthesized from the deaths of supernovas using the power of gravity. Some also comes from primordial energy, gravitational energy from the collapse of space rocks into earth back when earth was formed.

According to Wikipedia:

The Earth's interior radiates heat at a rate of about 47 TW (terawatts), which is less than 0.1% of the incoming solar energy... The most important heat-producing elements are uranium (U), thorium (Th), and potassium (K)... estimates of Earth’s internal radiogenic heating rate ranges from as low as ~10 TW to as high as ~30 TW. About 7 TW worth of heat-producing elements reside in the Earth's crust, the remaining power is distributed in the Earth mantle.

Chemosynthesis power comes from the chemical bonding energies of the elements like sulfur and oxygen, which are themselves from the nuclear fusions of the ancient stars.

The deal with solar

Basically, solar power rules. The energy budget on the surface of the earth comes from the sun and geothermal, and geothermal is so puny it can be safely ignored compared to solar power. All other sources of power: biomass, fossil fuel, wind, tidal (I knew it was small, but not that tiny), 

Elon Musk wants to get humans to stop using fossil fuels and start using solar power directly, to avoid an economic and environmental collapse.

This reminds me of the collapse of the Western Roman Empire. Modern society is like the Western Roman Empire just before they ran into the Britons, Germans, and Persians. 

• We are running our society on fossil fuels, energies accumulated over ancient millenia, that we conquered from underground, just like the Romans were running their society on wealth, land, and slaves from easy conquests. 
• We are developing technologies that try to optimize fossil fuel efficiency, just like Romans were developing military technology and political institutions that allow them to better conquer their neighbors.
• We are finally coming to realize that this conquest can't last forever, and we would have to depend on the yearly salary of solar energy, instead of conquering ancient solar energy storages.
• For Romans, they turned to agriculture, and for us, we turn to sunshine, wind, hydro, and some other kinds of solar energies, as well as nuclear (the only significant non-solar energy source humans use)

Things ended badly for Romans because they couldn't transition to an agricultural society that lives on a yearly energy salary. We must turn to solar (and nuclear) energy as fast as possible to prevent a collapse.

Concurrently, developing nuclear fusion power is also important, but don't count on that to solve the energy problem facing humans right now, since it's STILL 20 years away.