In the mid-20th century, Carl Sagan pioneered the search for extraterrestrial intelligence (SETI) in the United States, and prominent Russian astrophysicist Nikolai Kardashev did the same in the Soviet Union, the other great scientific superpower of the time.
From that vantage point, he proposed using an alien civilization’s energy needs as a way to categorize that civilization’s position on the ladder of technological progress. This framework became known as the Kardashev Scale, and is one of SETI’s oldest and most visionary ideas, as well as a staple of science fiction.
Also, it’s very incomplete. And if we want to develop our civilization, we need to consider the big picture.
energy ladder
Kardashev’s ideas about advanced alien civilizations were based on basic physics. No matter how advanced civilization has become, energy is still needed to power its technology.
The Kardashev scale not only gave scientists a new framework for thinking about extraterrestrial life, but also a new way to think about humanity.
Kardashev’s proposal was to clarify what energy sources will become available as civilization becomes more advanced. He scaled the starlight. No other source of energy is so accessible and so vast. All stars are giant thermonuclear reactors that pump vast amounts of electrical power into space. So, given the ubiquity of star power, the remaining question is: how much star energy can civilizations capture?
Based on that premise, he outlined three increasingly advanced levels, or “types” of civilization. This scale not only gave scientists a new framework for thinking about extraterrestrial life, but also a new way to think about humanity. Where will we land on the scale? Are we approaching that milestone? Are we on the path to advanced civilization as dreamed of by Russian scientists?
Type I
Kardashev defines Type I civilizations as those that can harness all the solar energy that falls on the surface of their home planet. The sun provides more energy to Earth in one hour than humans currently use in a year. If we were a Type I civilization, we could use all that energy to build our civilization.
Type II
Type II civilizations have far greater technological capabilities and are able to harness the entire energy output of their homeworld. This means that a Type II human civilization can harness 2.2 billion times more energy than a Type I human civilization.
One way to collect all this solar energy is to trap the star in some kind of giant energy collector. Physicist Freeman Dyson proposed this idea several years before Kardashev wrote up his idea of ranking civilizations. His hypothetical structure became known as the Dyson sphere, and like the Kardashev scale, it soon became a fundamental idea in both SETI and science fiction.
As many scientists, including Dyson, have pointed out, a civilization does not need to build a complete Dyson sphere to qualify as Type II on the Kardashev scale. The Dyson group, a dense constellation of energy collectors orbiting a star, would be sufficient. However, constructing Dyson spheres or Dyson swarms is not an easy task, as the prerequisite is pulverizing a significant portion of the planets in the solar system as material.
Type III
The top rung of Kardashev’s ladder takes us from the scale of our solar system to the entire galaxy. The sun is part of the Milky Way galaxy along with 400 billion other stars. If we were a Type III civilization, we would be able to harvest energy from all of them. At this level we are talking about a civilization with god-like abilities.
where we stand
Although humans won’t be building Dyson spheres anytime soon, our ability to harvest energy has increased rapidly over the past two centuries. Thanks to the industrial revolution and the discovery of fossil fuels, our energy use is now on an exponential growth curve.
There are elements that Kardashev ignored when he created his grand idea, which changes everything we think about energy, the planet, the fate of civilizations – the planet’s biosphere.
In 1976, Carl Sagan tallied our energy consumption and determined that we were a Type 0.7 civilization. He then extrapolated our energy use into the future and predicted that it would reach Type I in just a few hundred years. More recently, a group of scientists led by Jonathan Hian at NASA’s Jet Propulsion Laboratory have carefully investigated this problem and estimated that we will reach the pivotal Type I milestone in 2317 (proving once again that Carl Sagan was always ahead of his time).
That means we’re still a few centuries away from surpassing the first milestone on Kardashev’s vaunted scale. That should be cause for big celebration, right?
What Kardashev missed
Unfortunately, things aren’t that simple. There are elements that Kardashev ignored when he created his grand idea, which changes everything we think about energy, the fate of planets and civilizations: the planet’s biosphere, the totality of its inhabitants and the ecosystems they inhabit.
Earth’s biosphere includes microorganisms, forests, savannahs, animals, and more. Humans are part of the biosphere, as are all species on the planet with advanced technological civilizations. The biosphere is an important element when considering civilization and its trajectory. Because, simply put, the biosphere doesn’t like to be messed with. As we humans have only recently discovered, the biosphere is a powerful force in its own right.
When we extract huge amounts of energy from the Earth, huge amounts of waste heat are returned to the biosphere. And the biosphere, which is deeply connected to the geosphere, will react when that happens.
There is great irony in the fact that Kardashev does not take the biosphere into account when thinking about civilization. It was his compatriot, the great Russian biogeophysicist Vladimir Vernadsky, who coined the term “biosphere” in 1926. Vernadsky was the first scientist to realize that life, expressed as a biosphere, must be counted as a factor influencing the development of a planet.
If you want a powerful example of the biosphere’s ability to take over the planet, take a deep breath. Earth’s 21% oxygen concentration is the result of microorganisms inventing a new form of photosynthesis over 2.5 billion years ago. This “Great Oxidation Event” caused by the biosphere was one of the most important points in Earth’s geophysical history and completely changed every aspect of Earth’s evolution.
life pushes back
Kardashev’s grave mistake was to ignore the power of the biosphere. A civilization climbing the energy harvesting capacity curve cannot simply rise to the point where it captures all the solar photons that fall on it. Before that happens, the biosphere will generate feedbacks that could potentially bring technological civilization to its knees, and its ascent to Kardashev scale will likely be halted forever.
Recognition of the power of the biosphere eventually led to Earth System Science (ESS). ESS is a modern scientific field in which strong connections between Earth’s biosphere (life) and the rest of the terrestrial sphere (atmosphere, hydrosphere (water), cryosphere (ice), and lithosphere (ground)) are considered fundamental. Because these geospheres are closely related, changes in one geosphere can trigger reactions in the other. These reactions are known as “feedback” and can be positive or negative.
Our simulations showed exactly what Kardashev’s scale misses for civilizations climbing the energy utilization ladder. That is, the climb is neither simple nor easy.
ESS researchers have been warning about this for decades. Our incredible energy harvesting capacity in the form of fossil fuel use has caused feedback in the form of climate change.
The important thing to understand is that energy harvesting always results in some form of feedback. The second law of thermodynamics (also a fundamental physical concept) states that when energy is used to do useful work, there is always waste. When you power your car with a gallon of gasoline, some of that energy is wasted heating the engine block instead of turning the wheels. When we extract huge amounts of energy from the Earth, huge amounts of waste heat are returned to the biosphere. And the biosphere, which is deeply connected to the geosphere, will react when that happens.
test the limits
In 2018, my colleagues and I sought to model an energy-harvesting technology civilization and its interaction with the planet. Although our model was simple, we sought to capture the interconnected trajectories of planetary nations and civilizations as they use ever greater amounts of energy.
In one-third of our simulations, the planet changed environmentally but remained “habitable” for a complex technological civilization, and its population reached a stable state. In a further third, the population could grow rapidly and then decline rapidly, making it difficult to maintain the continued operation of a complex technological civilization. In the final third, civilization completely collapsed and the population plummeted to virtually zero.
A technological civilization that has been successful over a long period of time must have developed the wisdom to maintain a balance between its “technosphere” and the biosphere.
Our simulations showed exactly what Kardashev’s scale misses for civilizations climbing the energy utilization ladder. That is, the climb is neither simple nor easy. If you’re not careful, the biosphere your civilization depends on will be blown off the ladder by hurricane-force winds. Although the feedback from fossil fuels may be more dramatic, energy obtained from renewables is subject to the same constraints imposed by the second law of thermodynamics. The more energy we use, of any kind, the more feedback our biosphere generates. There is no free lunch.
When Kardashev proposed his scale, most people were not yet aware of the amazing power of the biosphere. That is why he could imagine a young technological civilization reaching Type I status unhindered. But if long-term, successful technological civilizations exist, they know better. They must have developed the wisdom to balance their “technosphere” with the biosphere on which they depend. The real question before us now is: “Can we ever be that smart?”
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