AboutTalk of Today PodcastEssays
July 24, 2020

A Proxy for Progress: Energy Rate Density

Energy rate density — the amount of energy flowing through a system per unit time per unit mass — can be used as an effective proxy for the progress of our species, as progress is largely determined by how much energy we can put to use towards our goals.

Over the past few centuries, humanity has been on a seemingly inexorable march along the path of progress.

We all have an intuitive notion of progress. It’s the idea that things get better, that the world of tomorrow will be better than the world of today, that our progeny won’t have to worry about as many of the issues that shaped our lives. Our language is suffused with the idea that progress is a process of ascendance. We reach our potential. We climb the corporate ladder. We move forwards and grow as people.

Onward and upwards

The idea of progress is so potent in the way we see the world that we divide our political leanings (arguably in a counter-productive way) based on the idea. One is either a progressive or a conservative.

For something so foundational to the way we see the world, something that is responsible for the historically privileged lives we live, you’d think we’d have a better understanding of what it is and how we might accelerate it.

Recognising this point, economist Tyler Cohen and entrepreneur Patrick Collison wrote an article in The Atlantic in 2019 with the title ‘We Need a New Science of Progress’. They said:

“...for a number of reasons, there is no broad-based intellectual movement focused on understanding the dynamics of progress, or targeting the deeper goal of speeding it up. We believe that it deserves a dedicated field of study. We suggest inaugurating the discipline of “Progress Studies.”

It’s a great idea. Progress has real consequences for the lives we lead. The actions of those who came before us created a world where we can live free from many diseases, fly in planes for, access the library of the world through a palm-sized supercomputer, to list just a few of the amazing capabilities we have that characterise our times.

When we think of progress, we think things like higher living standards and lifespans, increased access to healthcare and education for all citizens. To put it simply, everyone living longer, freer, and more fulfilling lives.

The idea of progress captures vast areas of our lives, weaving together ideas of advancement in technology and science, culture, economics and perhaps most importantly, morality.

With a concept so broad, however, trying to come up with ways of quantifying progress in general could be quite difficult. Fortunately, across all of the domains progress includes, there is a commonality: energy.


Energy is the currency of life. It animates matter, enabling complex configurations of molecules like you and me to manipulate the world around us in the service of our goals, namely survival and reproduction. Each organism has a specific amount of energy it requires to continue living. If the energy the organism has access to falls below this point, it dies. An energy surplus for many forms of life is stored for a rainy day.

In the hands of an inventive species like our own, it means the potential for progress.

Each step up the ladder of progress requires more energy than the previous step to maintain. Thus, the ability to extract energy from the world and put it to work is a useful way to frame humanity’s evolution across the millennia as without excess energy there can be no progress.

Photo by Cullan Smith on Unsplash


It started with fire. When we began cooking food we reduced the amount of energy required for digestion. This led to us needing to eat and hunt less and gave us more energy to fuel development. Thousands of years later we domesticated animals like oxen, outsourcing aspects of the energy-intensive, back-breaking work of agricultural to these beasts of burden. The extra time and energy these developments gave us allowed us to invent — to produce new technologies that helped us do things more easily.

Time and time again, through our ingenuity we’ve found ways to extract energy from the world and to put it to work. From the steam-engine to the electrification of our world, our capacity to generate and channel energy flows has freed up time and resources for ourselves to be spent however we wish.

This trend has continued into our current age, where many living in more advanced societies don’t need to grow food or hunt at all and require upwards of 30x our daily caloric needs in energy to fuel our technologically advanced existence.

Measuring Energy

Energy is critical to everything that we do. So how do we measure it?

In physics, energy is defined as the capacity for doing work. We measure energy in joules (J), where 1 joule is equal to the work done by 1 newton of force acting over a distance of 1 metre. When it comes to notions of progress, however, the quantity of energy alone doesn’t tell us much. A blue whale weighing 136,000kg has a basal metabolic rate around 2 million kilo joules (kj) a day, roughly the same as 280 people, though we’d be hard-pressed to say that blue whales are more advanced than us because of this.

A more useful measure of progress is Energy Rate Density.

Energy Rate Density

Energy Rate Density is a measure of energy flow through a system per unit time per unit mass (measured in J/s/Kg in this essay). It’s a special measure because it relates specifically to the density of the flow of energy in a system, not the absolute amount. The more energy a system has flowing through it per gram per second, the higher the energy rate density.

Dr. Eric Chaisson, an astrophysicist at Harvard University, uses energy rate density as the thread to weave a wonderful unifying, evolutionary worldview of the universe he calls Comic Evolution. His work explores how flows of energy in our universe across billions of years give rise to the cosmic entities we see, and most importantly, the evolution of life and our societies. In his paper Energy Flows in Low-entropy Complex Systems Chaisson writes:

“Energy rate density offers more than an effective metric, capable of assessing structural and functional complexity in thermodynamic systems. It potentially provides a new way to broaden the concept of evolution and to unify the natural sciences, including the physical evolution of relatively simple inanimate systems, the biological evolution of more complex life-forms, and the cultural evolution of some of the most complex systems built by human society. The sum total of these three phases of evolution, broadly conceived, is the interdisciplinary subject of cosmic evolution, a grand scientific narrative now under development.

From the perspective of energy rate density, human beings and our societies have energy rate densities unlike anything else in the universe.

Energy rate densities of various entities in the Universe: Source

Our galaxy has an energy rate density of around 0.0001 J/s/kg; the Sun’s is double that figure. The energy rate density of living organisms dwarfs that of these cosmic giants. Plants have an energy rate density of ~1 J/s/kg (5000x more than our sun), and mammals are at around 4 J/s/kg.

Human beings and our societies have the highest energy rate densities on Earth. Many of our lives have energy rate densities of around 200 J/s/kg.

A Proxy for Progress

Here’s how the energy rate density of humanity — our total control of energy flow — has changed over the past two centuries:

Global Energy Rate Density over the past few centuries (data source: Our World in Data)

Our current global energy rate density is around 41 J/s/Kg.

Energy rate densities for countries around the world vary wildly and in some unexpected ways. For instance, Iceland has the highest energy rate density in the world at ~190 J/s/kg, 46% higher than Luxembourg which ranks #2 at ~130. This is surprising until you consider that Iceland generates 100% of its energy from renewable sources, harnessing the geothermal energy that seeps through its craggy landscape to use in its energy-intensive industries (aluminium processing). Another reason is that a high proportion of its population owns a car.

Energy Rate Density & GDP per capita of the world

Some of the world’s most ‘progressive’ countries like ~Norway (~78), Germany (~55), and Switzerland (~50) have energy rate densities less than other countries that few would consider to be ideals of progress. For instance, Qatar and Saudi Arabia have energy rate densities of ~ 95 and ~80 respectively. This is most likely due to the fact that a vast proportion of their economies are focused on the extraction of fossil fuels, which again involve heavily energy-intensive processes.

Saudi Arabia’s Exports in 2018 (Source)

Comparing the energy rate densities of specific countries isn’t especially useful for a number of reasons. Some include climate differences, the natural resources countries happen to have within their territories, and population density.

The most important point to note, however, is countries, like people, do not exist in isolation. Our countries are inextricably interconnected, specialising in particular industries like mining and manufacturing, all depending upon one another for resources and services to continue to survive. Viewing countries as completely distinct would be like comparing different organs of the body, completely ignoring how they contribute to one another and the greater whole.

From this perspective, we already live in a global society,  so energy rate density is a more appropriate perspective to take when thinking about our progress.


Just like with any measure, there are several shortcomings with using energy rate density as a measure of progress.

Climate Change

Perhaps the most obvious is the relationship between our current sources of energy and climate change. The fossil fuels that the majority of the world uses to is using to drive progress is producing tremendous amounts of waste that could end up killing us all. This isn’t an exaggeration. A radically changing climate and the environmental collapses it could cause could bring about huge resource scarcity and force hundreds of millions — if not billions — of people to suffer from famine, which could destabilise our societies and bring about war.

Progress is not just having the ability to harness increasing amounts of energy, but to do so sustainably across time. Energy rate density doesn’t capture this.

Photo by Ella Ivanescu on Unsplash

Human Rights

The energy rate density of a society tells us nothing of the conditions of people living in it or the health of the bio-regions these societies are situated in. As mentioned above, some countries with the highest energy rate densities are backwards by 21st century moral standards. While there is without a doubt correlation between energy use and the securing of basic human needs and human rights, it’s far from determinant.

One can imagine a society where huge amounts of energy are consumed by factories of robots producing all of our goods, the profits of which going into the hands of the mega-rich 0.0001% of the population without any redistribution, while the rest of the population languish without work in barbarous conditions. Or a world where the biosphere has collapsed, where we live on a near inhospitable, unforgiving, hot-house planet where we need to generate tremendous amounts of power to replace the gifts of nature that we took for granted.

Energy Efficiency

Energy rate density does not capture how efficiently energy is used. It’s easy to imagine a society with a high energy rate density but with shocking efficiency, versus a different society with a lower energy rate density with far higher efficiency rate.

The measure also doesn’t capture huge leaps in information technology, the internet being the best example. The efficiency gains from the internet are hard to capture. Instead of having to buy physical maps that had to be printed and distributed, we have free access to maps that update traffic data in real-time of the world through our phones. We can get knowledge of nearly anything through a simple Google search, rather than spend the resources having to produce, distribute and buy books, or go to a library to get access to them.

If you look again the graph of global energy rate density, the period from the year 2000 to today only shows a relatively small increase, which tells us nothing of the incredible technological transformations our societies are going through. That being said, we’re only at the very beginning of this information revolution. As networked devices become ubiquitous, the internet of things will consume greater amounts of energy, as will the computers we use to process the tremendous amounts of data they generate.

No measure is perfect. While energy rate density fails to capture key elements for progress, that doesn’t mean it isn’t an effective course-grained proxy for it.

Physics and Society — A Broader View

Photo by NASA on Unsplash

The story of Life is a tale of war that has waged for billions of years. Since its seemingly miraculous inception as simple self-replicating molecules, life has engaged in the endless pursuit of finding and harnessing energy to battle the inexorable, gnawing tide of entropy.

The importance of energy for life has never changed. As organisms have become increasingly complex, their demand for energy grows with them.

Having advanced beyond the need to spend most our lives worrying about carnal necessities like food and shelter, our energy appetite has increased to fuel our technologically advanced existence, powering the nervous system of a planetary-scale society and providing opportunities to people that couldn’t have been imagined mere centuries ago.

When we look to into the distant future — thousands of years ahead where we’ve become a space-faring species and we may not even recognise the lifeforms we’ve evolved into — something that will remain constant is the necessity for the manipulation of energy flows to maintain our ever-increasing complex lives.

Where economic metrics like Gross Domestic Product fall short, measures based on the laws of physics stand resolute, unchanging. As we think of progress, not across years or decades, but centuries and millennia, we should think of progress, at least in part, in the universal measure of energy.

*GDP, population, and energy usage data presented in the graphs above come from the World Bank. An average weight of 60kg and a BMR of 7000kj per person were used in the calculations.*

Enjoy the essay? Share it with whoever you think might enjoy it, or

Other essays


New Frontiers Newsletter

Sign up for an infrequent email that weaves together developments in culture, science, and technology with philosophy in an exploration of our place in the world today and what it means for how we should navigate it.

Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.