Is it possible to categorize extraterrestrial civilizations when we haven't even made first contact yet? Scientists think they can, based on the energy usage of such alien civilizations.
Nikolai Kardashev was a Soviet-Russian astrophysicist. He proposed the Kardashev scale in 1964, which categorizes civilizations based on the total amount of energy available to them. The original scale is divided into Type I, Type II, and Type III. Let's take a look.
Type I
Type I civilizations are the most technologically adolescent on the Kardashev scale. They have access to the energy output of an entire planet(4×10^12 watts). This could be accomplished by using abundant substances for fusion reactions, such as hydrogen into helium from Earth's water. This is also the process that occurs in the Sun's core. Another method proposed is covering a significant area of the planetary surface or atmosphere with solar panels.
Human civilization isn't even at this stage yet. According to an estimate by Carl Sagan, we are at about 0.7 on the scale.
Type II
Moving on to Type II, this is where things get more exciting. Type II civilizations have access to the energy output of an entire star(4×10^26 watts). One of the theoretical technologies often correlated with Type II civilizations is the Dyson sphere. Freeman Dyson(unrelated to the vacuum cleaner) is credited with developing the model through a thought experiment, although he expanded upon the concept first created by sci-fi writer Olaf Stapledon.
"Not only was every solar system now surrounded by a gauze of light-traps, which focused the escaping solar energy for intelligent use..." - Olaf Stapledon, Star Maker
A Dyson sphere is an artificial structure designed to harvest the light energy emitted by a star. Rather than a complete and hollow sphere, it would most likely look like a swarm or many rings surrounding the star. Realistically, the effective use of a Dyson sphere would require colonization or significant reengineering of the civilization's home planet, as it would plunge any planets in the system into darkness and cold.
Now, it stands to reason if there are other civilizations out there, a good amount of them must be Type II. Therefore, we should be able to observe evidence for these Dyson spheres—stars with a disproportionately low luminosity compared to their infrared radiation. However, despite years of searching, no such evidence has been found.
Some have theorized that this is due to a secondary layer in the "sphere", constructed to absorb the waste heat. This would hide the star's presence further, the purpose which could be connected with the Dark Forest theory. Read more about the Dark Forest theory here.
Type III
We venture further into exotic hypothetical territory in this next step. Type III civilizations have access to the energy output of an entire galaxy(4×10^37 watts). They would apply the energy harvest methods that Type II civilizations are capable of to all of the stars or black holes in the galaxy. They may also utilize quasars and SMBHs at the cores of galaxies as sources of energy.
One possible example of a Type III that pops into mind is the Galactic Republic from Star Wars. The Republic is comprised of hundreds of star systems within the fictional galaxy.
But although the expansive nature of the Republic is impressive, the technological feats shown in the films are far from what a Type III civilization is capable of. The galaxy is unified, but the Republic's technology has not yet been able to utilize all of the energy available. Most of the sub-civilizations in the Republic would rank as either Type I or II.
There are other levels included in expansions of the original scale, such as Type 0(not ranked on the scale), Type IV(control an entire universe), and Type V(control multiple universes). Ultimately, the Kardashev scale could support SETI research efforts by looking for specific technosignatures expected from these hypothetical structures.
That's all I have for you today. Check out the sources linked in the bibliography below, as well as more sci-fi and science works about this topic if you're interested. I'll see you in the next one!
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Bibliography
Lovell, Christopher. “Classifying Civilisations: An Introduction to the Kardashev Scale.” Astrobites, 15 Mar. 2016, https://astrobites.org/2016/03/15/classifying-civilisations-an-introduction-to-the-kardashev-scale/#:~:text=Carl%20Sagan%E2%80%99s%20modified%20Kardashev%20scale%2C%20which%20allows%20for,far%20from%20realising%20Type%20II%20or%20III%20status.
Tate, Karl. “Dyson Spheres: How Advanced Alien Civilizations Would Conquer the Galaxy (Infographic).” Space.com, Future US, 14 Jan. 2014, https://www.space.com/24276-dyson-spheres-how-advanced-alien-civilizations-would-conquer-the-galaxy-infographic.html.
Stapledon, Olaf. Star Maker. Oxford Reprints, 2010.
Kaku, Michio. Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100. Anchor Books, 2012.
Kardashev, Nikolai. “Transmission of Information by Extraterrestrial Civilizations.” Astronomicheskii Zhurnal, 1964.
“Galactic Republic.” Wookieepedia, Fandom, https://starwars.fandom.com/wiki/Galactic_Republic.
Other works about the Kardashev scale and the evolution of extraterrestrial civilizations:
Physics of the Future(Chapter 8: Future of Humanity) by Michio Kaku
The Dark Forest by Cixin Liu
Death's End by Cixin Liu
Children of Time by Adrian Tchaikovsky
Alien Worlds by Netflix
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