The Kardashev Scale

Classification

The Kardashev Scale was invented to measure a civilizations technological progress based on the amount of control they have over nearby energy. By connecting the different stages to each other, we can be helped to understand what kind of structures we have to look for to find them and to understand the next steps they are likely to take after accomplishing any given stage. Let's look at the specifications.

Type 0 civilizations

Any species that is not able to use the entire energy of their home planet yet is classified as a 0.xx civilization. The percentage of the energy of their home planet that this species can already harness replaces the two crosses here. For example, humanity currently is classified as a Type 0.72 civilization, indicating we are using 72% of the available energy of our planet.

Type 1 civilizations

A species reaches Type 1 on the Kardashev Scale as soon as it is able to use 100% of the energy of their home planet. Humanity is thought to still be 100-200 years away from now, but has made significant progress within the last century.

As we can see, within the last 120 years we went from being a Type 0.58 to a Type 0.72 civilization.

Type 2 civilizations

A Type 2 civilization is capable of using the entire energy of their planetary system, most of which is coming from their star(s), depending on how many there are, since we also observed systems with up to four stars. Type 2 civilizations are the ones we are mostly looking for, since they are relatively easy to identify: Their star(s) would most likely have either a complex form of a Dyson Sphere or a Dyson Swarm swinging around them. This is why the Kardashev Scale is useful: We know their next step towards increasing their available energy, so we can also take an educated guess on how they would solve it.

Sadly, we have yet to find a single Dyson Sphere or anything that seems to absorb a system's star's energy. We once thought we found a structure like this when we observed a star that was giving off much less energy than usual from time to time, however after a closer look we found out it was only due to tiny dust particles on the telescope.

Happens to the best of us.

Type 3-5 civilizations

A Type 3 civilization is basically "just" a Type 2 civilization that managed to not only use their home system's star's entire energy but repeat that step on all stars in their home galaxy. A hypothesis by Robert A. Freitas Jr. states that a colonization of the entire galaxy would be undertaken by a more evolved species with the help of autonomous machines. These would land on a planet and take about 500 years to harvest the raw materials of the planet and produce new machines with them, which pursue the same goal on other planets. Due to the resulting exponential growth, it would take 3.75 million years for our Type 3 civilization to have scoured the entire galaxy.

Type 4-5 are superlatives of this: A Type 4 civilization is able to control and use the energy of more than one galaxy while a Type 5 civilization controls their entire supercluster of local galaxies.

However, due to the fact that Type 3, 4 and 5 civilizations would have to place Dyson Spheres all around their galaxies, we could easily detect them were there any of them near the Milky Way. Because of this, it's very unlikely for any species to have exceeded Type 2 anywhere near us, yet.

Type Ω civilizations

A Type Ω civilization would be able to manipulate and control their entire universe, or possibly multiple universes. This is often called a "Watcher" type civilization and we will come back to look at them more closely in one of the next chapters.

Conclusion

In the context of the Fermi Paradox that we are trying to further observe here, we found out that our best guess at finding other civilizations is to look for energy-harvesting structures around other stars. We don't really have any way to detect civilizations that are limited to nothing but their home planet.

Since we know that there are lots of planets in the habitable zone and are still unable to detect any Dyson structures, there has to be something that's holding back many intelligent species from reaching Type 2, right? There might be! This is called The Great Filter. Wanna find out more about it? Turn over to the next page :)

Additional Resources

1.
Robert H. Gray, an american data analyst and astronomer, published an article on IOPscience, going into further detail about how we have to imagine civilizations of Type 0-4 on the Kardashev Scale.