The Kardashev Scale is a means of measuring a civilization's progress. It helps gauge whether a society is closer to the "infant" or "adult" end of the spectrum. Case in point: the Industrial Revolution was a huge step forward for humanity, one which caused massive socio-economic and geopolitical changes forever. But was it really a notable event in the cosmic scheme of things?
What about voyaging beyond Earth? It was a notable event for humans, but was it more than a blip in the cosmic ocean?
Leaving the Solar System and even the entire Milky Way might seem like the stuff of the stuff of science fiction, but it might be a reality for humanity, someday. How advanced would we be then? And what if there are already civilizations out there that have achieved these incredible feats?
What is the Kardashev Scale?
The Kardashev Scale is a purely energy-based scale for measuring a civilization's technological prowess. In short, the scale is based on the amount of energy that a civilization has available to it.
It was devised in 1964 by a Soviet Astronomer, Nikolai Kardashev, and it first appeared in his paper, Transmission of Information by Extraterrestrial Civilizations.
Within the first version, Kardeshev originally defined three types, or categories, of civilizations. He established types ranging in scale from a planetary society, to a larger stellar society, and finally a galaxy-spanning empire.
Nikolai formulated his scale in this way because surmised that the overall status of a given civilization is, generally, the product of two things: energy and technology. The better their technology, the more energy one can harness.
And not only that. The more energy a civilization has access to, the better their technology can later become. It was his belief that any society could just develop as far as its technology and ability to use energy would take it.
It is generally only concerned with energy consumption on a cosmic scale. Since the 1960s, the scale has had a few extensions proposed beyond the rather limited three originally defined by Kardashev.
These include new levels: 0, IV, and V. These subsequent scales also included other metrics beyond pure power and its availability. The amount of energy required for the three basic civilization types is detailed in the image below.
A Type 0 Civilization
A Type 0 Civilization, as you can imagine, is one that has not yet been able to harness all the energy of its home planet. It is, therefore, a sub-global one that harnesses power from raw materials.
They do not yet have the ability to leave their home planet but are making steady progress towards it. Yes, you've guessed it, that's humans today. The late, great, Carl Sagan estimated humanity was at around 0.7 on this scale back in 1973.
Some estimate, like theoretical physicist Michio Kaku, we might only be anywhere between 100 and 200 years away from graduating to a Type 1. That'll be nice.
A Type I civilization
Type 1, as defined by Kardashev, is one still limited to one planet. But, critically, to have reached this level on the scale, the civilization must be able to harness all the energy available there.
For them, nuclear fusion is probably child's play as well as harnessing the antimatter. Other power sources from geothermal to other renewables would also be a given. Try to think of something like the planet Coruscant in the Star Wars Universe (but without the larger Republic/Empire), or the great works of Asimov.
A Type II civilization
Type II civilizations are those that have managed to harness all the power of their local sun. An example strategy would be the ability to construct a Dyson Sphere around it.
These hypothetical devices would completely surround a star and be able to collect all of its energy. This would require quite the level of technological ability, to say the least.
They would also likely have colonized multiple planets in their local solar system. For them, extinction is a long-lost fantasy. Little, if anything, would be able to kill them off, save themselves or a massive inter-species war.
A Type III civilization
A Type III civilization, or galactic civilization, would be able to control energy across many star systems and planets. The scale of their technological ability would be something beyond our current understanding and, possibly, imagination.
Some estimates have put this at about 10 Billion times the energy output of a Type II civilization. Who knows what else this kind of civilization would be able to achieve.
This would be something akin to galaxy-spanning empires common in science fiction. From Star Trek, Star Wars, to the Imperium of Mankind in the Warhammer 40,000 Universe, they would be masters of the Universe.
But they would still need to obey the laws of physics. Travel between each corner of the civilization would not be possible unless they'd managed to circumvent the constraints of the speed of light.
Needless to say, this would be a people who have really made it - so to speak.
They would make regular use of Dyson Spheres and might even be able to tap the energy of black holes. A Type III might also be able to harvest energy from gamma-ray bursts and quasars.
Or some other, as yet unknown, energy source.
A Type IV civilization
If a galaxy-spanning civilization isn't impressive enough, wait until you see a type IV. This would be one able to harness the energy across the entire universe.
Who knows what else they would be capable of?
A Type V civilization
Ok, how about one able to harness the energy from multiple universes? Absurd perhaps, but it might be possible in the far, far future.
We simply cannot even begin to understand their technological prowess. Perhaps they have achieved immortality too. One might be tempted to call them gods, for want of a better term, as their abilities would likely be comparable with what we typically associate with god-like creatures.
If they exist, could we make contact?
Back in the 1960s, it was proposed by Freman Dyson that it should be possible to detect the tell-tale signs of such civilizations from their IR emissions.
In 2015, researchers from Penn State University scoured the skies looking for potential candidates. They were able to shortlist around 93 galaxies, from a massive 100,000, that might, just, be home to some advanced civilizations. These galaxies showed signed of unusually high IR-emissions. This is a very rare thing to observe, but, they note, can be explained by thermal emission from warm dust.
Professor Garret, the author of the study, noted that “The original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement and that advanced Kardashev Type III civilizations basically don’t exist in the local Universe.”
So that might just be the end of it. Type III Civilizations either do not exist or are yet to develop.
Or, as Professor Garrett explained “we’re missing an important part of the jigsaw puzzle here. Perhaps advanced civilizations are so energy efficient that they produce very low waste heat emission products – our current understanding of physics makes that a difficult thing to do.”
There has been another study suggesting that finding Yotta-eV (1024 electron Volt) neutrinos could be proof of at least a type 3 civilization. This would require using a quasar (a VERY energetic galaxy) as a particle accelerator.
For comparison, nuclear bomb reactions release a measly 106 eV per reaction.
Are we alone in the Universe? More than likely not, but are we likely to be visited (or invaded,)by a highly advanced civilization in the future? The jury is still out. Let's hope that when they do arrive, they come in peace.