Sciency Words A to Z: Kardashev Scale

Welcome to a special A to Z Challenge edition of Sciency Words!  Sciency Words is an ongoing series here on Planet Pailly about the definitions and etymologies of science or science-related terms.  In today’s post, K is for:


In 1963, Soviet scientist Nikolai Kardashev published this paper concerning the search for extraterrestrial intelligence. Kardashev seems to have been primarily interested in how much information aliens might be able to transmit to us across the vastness of space.  This, in turn, relates to how much energy an alien civilization is able to produce, because the more energy you have, the stronger your radio signals can be.

Kardashev summarized his thoughts on this by devising a scale—now known as the Kardashev scale.  In Kardashev’s original system, there were only three types of civilizations:

  • Type I: a civilization that has harnessed energy on a planet-wide scale.  Kardashev considered Earth to be a Type I civilization.
  • Type II: a civilization that has harnessed the energy of an entire star, perhaps by building a Dyson sphere or some other megastructure around their own sun.
  • Type III: a civilization that has harnessed the energy of an entire galaxy.  Kardashev doesn’t offer any examples of this, but I might point to something like the Galactic Republic/Galactic Empire in Star Wars—they’re approaching Type III status.

Later scientists have expanded on the Kardashev scale.  Humanity has been demoted to a Type 0 civilization, because we don’t really use all the energy available to us on our planet.  Not yet, at least.

We can also talk about Type IV civilizations, which can harness the energy of the whole universe, and Type V civilizations, which can harness all the energy of the multiverse, or perhaps all the energy of alternative timelines, or something like that. Examples?  I don’t know, maybe the Timelords from Doctor Who or the Q-Continuum from Star Trek. Or maybe these people.

So which of these civilizations should we expect to find out there? What sort of transmissions do we expect to see?

The problem with Type IV and V civilizations is that their activities would be, to us mere mortals, virtually indistinguishable from nature.  As for Type 0 and Type I, their radio signals (if they’re sending any) may be too weak for us to detect over all the background radiation of the cosmos.

But the Type II and Type III civilizations… Kardashev was pretty optimistic about our chances of finding them.  In his 1963 paper, Kardashev argues that it’s absurd to think Earth is the only planet with intelligent life, and furthermore most alien civilizations should be far older and far more advanced than we presently are.  You may recall Enrico Fermi made a similar argument.

So there should be plenty of Type II civilizations out there, and perhaps a few Type IIIs as well, all chattering away in loud, easy-to-detect radio transmissions.  Or so Kardashev claims.  “In any case, the deciding word on this question is left to experimental verification,” he wrote.  But after fifty years of trying to detect something… anything… what has the experimental evidence shown us?

That’s a fair question.  And yet I have to agree with Kardashev: it is absurd to think Earth is the only planet with intelligent life.  So once again, in the immortal words of Enrico Fermi, where is everybody?

Next time on Sciency Words A to Z… wait, did we detect a signal?  Nope.  False alarm.

16 thoughts on “Sciency Words A to Z: Kardashev Scale

  1. As someone said, if we’re the only intelligent species, the universe is a big waste of space. SETI has been a shot in the dark so far, but look at what we’re learning about exoplanets. SETI capabilities will improve too. Maybe we’ll get to listen in on some alien TV shows, but conversations are foiled by that annoying speed-of-light thing. Unless some Type I decides we’re interesting enough to lend us a hand… or tentacle… or whatever.

    Liked by 2 people

    1. You’re right, SETI capabilities will improve with time. Also, during the course of my research, I learned that in the beginning SETI researchers took some educated guesses about which radio frequencies aliens might use to contact us, and they focused almost exclusively on those frequencies. It seems a bit presumptuous to me to try to predict which radio frequencies aliens would choose to use. I feel like we could have very easily missed something.

      Liked by 1 person

  2. A few years ago there was a study of 100,000 galaxies, looking for Type III type civilizations. They didn’t find any, although they did find 50 galaxies that have higher than normal infrared radiation that *might* indicate large scale Type II civilizations, or it might be due to natural causes. I think there was supposed to be a follow up study, but if so I can’t find anything.

    Liked by 1 person

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.