- The Kardashev scale describes three basic levels of advancement in terms of harvesting energy through which a civilization should progress.
- There are three types, and humanity has yet to achieve Type 1 status.
- Type 2 and Type 3 civilizations have almost god-like abilities to manipulate solar systems and even galaxies.
How do technologically adept civilizations evolve over timescales measuring in the tens of thousands or even millions of years? This is a question that haunts me as a researcher in the search for “technosignatures” from other civilizations on other worlds. Since it is already known that longer-lived civilizations are the ones we are most likely to detect, knowing something about their possible evolutionary trajectories could be translated into better search strategies. But even more than knowing what to search for, what I really want to know is what happens to a civilization after so much time. What are they capable of? What do they become?
This was the question Russian SETI pioneer Nikolai Kardashev asked himself back in 1964. His answer was the now-famous “Kardashev Scale.” Kardashev was the first, but not the last, scientist to try and formalize the steps (or stages) of the evolution of civilizations. Today, I want to begin a series on this question. It is central to technosignature studies (of which our NASA team is hard at work), and it is also important for understanding what might lay ahead for humanity if we manage to get through the bottlenecks we face now.
The Kardashev scale
Kardashev’s question can be put another way. What steps in a civilization’s advancement up the ladder of technological sophistication will be universal? The basic idea here is that all (or at least most) civilizations will pass through some kind of quantifiable stages as they evolve, and some of these steps might be reflected in how we could detect them. But, while Kardashev’s main interest was finding signals from exo-civilizations, his scale gave us a clear way to think about their evolution.
The classification scheme Kardashev used was not based on social systems of ethics because these are things that we can probably never predict about alien civilizations. Instead, it was based on energy, which is something near and dear to the heart of anyone trained in physics. Energy use might provide the basis for universal stages of civilization evolution because you cannot do the work of building a civilization without using energy. So, Kardashev looked at what energy sources were available to civilizations as they progressed technologically and used those to build his scale.
From Kardashev’s perspective, there are three basic levels or “types” of advancement in terms of harvesting energy through which a civilization should progress.
Type 1: Civilizations that can capture all the energy resources of their home planet constitute the first stage. This would mean capturing all the light energy that falls on a world from its host star. This makes sense, since stellar energy will be the largest source available on most planets where life could form. For example, Earth gets hundreds of atomic bombs’ worth of energy from the Sun every second. That is a pretty potent energy source, and a Type 1 species would have all this power at their disposal for civilization building.
Type 2: These civilizations can harvest the entire energy resources of their home star. Nobel Prize-winning physicist Freeman Dyson famously anticipated Kardashev’s thinking on this when he imagined an advanced civilization constructing a vast sphere around their star. This “Dyson Sphere” would be a machine the size of the whole solar system for capturing stellar photons and their energy.
Type 3: These super-civilizations could use all the energy produced by all the stars in their home galaxy. A typical galaxy contains a few hundred billion stars, so that is a whole lot of energy. One way this could be done is if the civilization covered every star in their galaxy with Dyson spheres, but there could also be more exotic methods.
Implications of the Kardashev scale
Climbing from Type 1 upward, we go from the imaginable to the god-like. For example, it is not hard to imagine using lots of giant satellites in space to capture solar energy and then beaming that energy down to Earth via microwaves. That would get us to a Type 1 civilization. But making a Dyson sphere would require chewing up whole planets. How long until we get that kind of power? How would we have to change to get there? And once we get to Type 3 civilizations, we are almost thinking about gods with the capacity to engineer entire galaxies.
For me, this is part of the point of the Kardashev scale. Its use for thinking about detecting technosignatures is important, but even more potent is its capacity to help us guide our imaginations. The mind can go blank staring across hundreds or thousands of millennia, and so we need tools and guides to focus our attention. That may be the only way to see what life might become — what we might become — once it arises to set out across the frontiers of space and time and possibility.