We, humans, have this innate feeling of uncertainty when we raise our heads and face the sky. Our eyes jump from star to star, mapping out the vastness in front of our keen eyes, looking for something, for someone. But is there an end to our search? A question that possibly dates back to when humans first learned to look up at the stars, probably the question that urged astrophysicist Frank Drake to come up with an equation to understand why we haven’t seen anyone out there yet. Are we alone in the Universe?
In 1963, 32-year-old Nikolai Kardashev looked up at the stars, but he didn’t question the existence of sentience out there. In his mind, the vastness of space in itself stood as the strongest evidence that we cannot be alone. So, he focused on ways to communicate with our neighbours out there. In his paper, “Transmission of Information by Extraterrestrial Civilizations”, he tried to find an answer to how strong a radio signal from civilizations like ours would need to be in order to be detected using our conventional radio astronomical techniques. On his quest to do so, though, he opened humanity to a new measurement through a thought experiment, a scale that quantifies the growth of civilizations in the universe. This scale is called the Kardashev Scale.
The Kardashev scale is a hypothetical measure of a civilization’s level of technological advancement where each subsequent civilization has exponential advancements. Kardashev decided to use energy consumption on a celestial scale as the currency for the measurement of a civilization’s level of advancement. This was based on our single source of raw civilizational data, which was of the human civilization. Historians had observed that as humans evolved and our technologies advanced, we found more efficient ways of utilizing the resources our planet had to offer. The discovery of fire, for example, enhanced the way we manipulated our surroundings and produced usable energy. Or the technological developments during the Industrial Revolution in the 18th Century. With time, our ability to both produce and utilize energy evolved and it did so at an exponential rate. With an increase in the human population, our energy consumption also naturally increased.
All of this was because humans are expansionists, and this trait in our ancestors allowed them to survive and thrive. So, assuming that other sentient life out there had a similar approach to evolution, Kardashev categorized civilizations into three initial types:
Type I Civilizations:
A Type I Civilization, also called a planetary civilization, is one that is able to harness and use all of the energy available on its home planet, including all the energy its home planet receives from its parent star. Obviously, the first question that comes to mind when we think about this type of civilization is if our planet Earth is one of these, but unfortunately, we’re not quite there yet. For Earth to earn the Type I Civilization status, we would need to reach energy levels as high as about 2×10¹⁷ watts. On the other hand, the amount of energy currently utilized by us is around 2×10¹³ watts (2020). In general, a civilization with energy utilization between 10¹⁶ and 10¹⁷ watts is classified as a Type I Civilization.
A civilization of this level would need to have a large variety of exotic technologies and energy sources that would be intricate enough to access and utilize all the renewable as well as non-renewable sources of energy available on its home planet. Everything from solar energy, wind energy, nuclear energy to even fossil fuels would be in their control. It has been speculated that a fully evolved Type I Civilization would have the ability to control natural planetary phenomena like earthquakes and volcanic eruptions too!
In 1973 astronomer Carl Sagan estimated Earth to be roughly a Type 0.7 civilization.
Type II Civilizations:
While the Type I Civilization level might be just within the grasp of humanity with a few enhancements to our current technology, the next behemoth on the scale is quite a ways ahead. A high Type I Civilization is one that has successfully harvested the resources of not just its home planet but also other planets in its star system. So naturally, it decides to take on the next big challenge and starts harvesting the energy released by its local star. A civilization that is successful in harvesting all the available energy released by its host star attains the Type II status. It is estimated that a Type II Civilization would reach energy utilization levels as high as 10²⁶ watts. But to achieve such feats, these civilizations would have to create colossal megastructures, which might even be larger than the host star itself.
One such hypothesized megastructure is a Dyson Sphere. A Dyson Sphere would encompass the host star and utilize all of its output energy. A civilization with the capabilities to construct such a structure would surely stand out in our night sky though. For example, on October 14, 2015, researchers using the Kepler Space Telescope, noticed irregular light fluctuations from a star KIC 8462852, popularly known as, “Tabby’s Star”, in the Cygnus constellation, about 1,470 light-years from Earth. The researchers noted that the star in question dimmed in brightness by a staggering 22%, for reference, a Jupiter sized planet would only cause a drop in brightness of about 1%. As a result, experts have speculated that this star might, after all, be a real-life Dyson Sphere.
However, the resources needed to create such a megastructure would be immense. One possible solution to this problem would be to “cannibalize” a planet close to the parent star, such as Mercury, and use its resources to construct the Dyson Sphere. For a high Type I Civilization that is not quite type II yet, a possible variation on the Dyson Sphere concept would be a Dyson Swarm, which is a group of relatively smaller structures that serve the same purpose. There are other proposed variations too, each tip-toeing at the boundaries of science fiction.
A Type II Civilization could decide to further utilize the surplus of energy for various other ventures, such as a Matrioshka Brain, which is a megastructure, specifically a class B Stellar Engine, that could use all the energy output for computations through mechanical power. Such a structure would have an enormous computational capacity, to a point where it could simulate multiple universes simultaneously. The potential applications of such structures are so vast that they have been referred to as the universe’s most powerful supercomputers.
Alternatively, a Type II Civilization might choose to venture off into space along with its entire star system through class A Stellar Engines or Shkadov thrusters, which are megastructures that use the radiation emitted by a star to produce thrust.
Such a civilization would have control over every object in its star system. Say, there was a massive asteroid heading straight towards Earth. Well, a fully developed Type II Civilization could just vaporize it, or it could even alter the position of Jupiter just enough to change the trajectory of such an object. A civilization at this level would have control over its own fate, no known physical phenomenon in the universe would be able to push these beings to their extinction. Theorized megastructures like the Dyson Sphere don’t even scratch the surface of what a civilization, with the seemingly unlimited energy of its star, can do.
Type III Civilizations:
If Type II Civilizations weren’t sci-fi enough, we move onto Type III. This type of civilization would have the ability to harness and use all of the available energy in their home galaxy. A fully evolved Type III Civilization would reach energy utilization levels as high as 10³⁶ watts. This includes the energy of every star, black hole, and even the dark energy present in the galaxy.
A civilization of this magnitude is almost incomprehensible to us. These beings would have discovered efficient ways of interstellar travel, possibly even faster-than-light travel through hypothetical warp drive systems. At such a scale they might even discover new laws of physics that we cannot even start to comprehend.
These beings may be so advanced they might have surpassed the biomarkers that we use to detect signs of life, and we may not even be able to distinguish them from the rest of the naturally occurring universe. To such a civilization, humans would be like what primitive microbial life is to us.
These beings could harness the power of various stars using multiple Dyson Spheres or even tap into the energy of the supermassive black hole at the centre of the galaxy. Theorists suggest that other ways of generating energy might include using cosmic string generators, which would harness the energy of cosmic strings, which are hypothetical rips and tears in space-time that may have formed in the very early stages of the universe.
This level of civilization seemed just about in the realm of possibility for Kardashev. But he decided that a Type IV civilization would be too advanced to even consider. But that did not stop other theorists from adding onto his original scale.
Extensions to the Original Scale:
Type IV: This is a type of civilization that can utilize the entire usable energy of the universe. Feels like we’re straying towards the edge of impossibility, doesn’t it? Well, according to theoretical physicist Michio Kaku in his books “Hyperspace” and “Parallel Worlds,” a Type IV Civilization could harness “extragalactic” energy sources such as dark energy. The current total energy available for our visible universe is estimated to be around 10⁴⁵ watts. A civilization with access to such a tremendous amount of energy would be virtually indistinguishable from the natural universe.
Type V: This would be a civilization that hypothetically controls multiverses.
There are other scales that have been used to classify civilizations, such as John Barrow’s proposed scale based on reverse classification called “microdimensional mastery”, which is sometimes referred to as the Reverse Kardashev Scale, where civilizations are classified from type minus-I to type Omega-minus based on their ability to control objects at increasingly smaller scales, from human-sized buildings down to the basic structure of space and time itself.
All such scales branching out from the Kardashev Scale in itself, were developed to measure the technological advancement of civilizations and to make it easier for us to detect signals produced by their activities in our universe. However, scientists have not yet been able to detect any such stellar phenomena or even remnants of any megastructures like those described. This brings us back to our question, which was the driving force behind the thought experiment: are we truly alone in the vastness of space? Who knows, maybe someday we will come across a class A Stellar Engine zooming past our solar system, and maybe that’ll help us put an end to our crudity.
