What is the Kardashev scale, and can we climb it?
The UniverseFridays
May 1, 2026
6 min read
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What is the Kardashev scale, and can we climb it?
The Kardashev scale is an interesting but flawed gauge of a civilization’s growth
By Phil Plait edited by Lee Billings
This artist’s concept shows a hypothetical light-harvesting megastructure built around a star.
cokada/Getty Images
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As a long-time lover of science fiction, I’m very familiar with the old trope of a galaxy-spanning human civilization, thousands or even millions of planets strong. Watching Star Trek, Star Wars and Stargate made such a dizzying future seem almost inevitable. Humans are destined for the stars—right?
We’ve certainly made our first steps in that direction, having already sent robotic probes all across and even out of our solar system. But getting people into space has been trickier. We’re gooey globs of meat that need a lot of TLC to survive beyond Mother Earth. Still, we’ve managed to get to the moon (and a wee bit farther), which is amazing all in itself.
But space is vast and deep, and there’s a very, very long way to go to visit even the other planets orbiting our sun, let alone those around other stars.
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Still, some consider humanity’s future in space to be so bright that they’ll bet the bank on it. China and the U.S. are both proceeding with separate plans for moon bases, and U.S. billionaires are trying very hard to provide the hardware for NASA’s lunar push. Jeff Bezos’s Blue Origin is in the running to develop a lunar lander, as is Elon Musk’s SpaceX, with an approach using its Starship rocket—though both still have a long way to go.
Musk seems confident. Of course he does: with SpaceX, he’s truly revolutionized rocketry—and become the world’s wealthiest person. History shows, however, that his predictions for when his companies’ breakthroughs will occur tend to be several years off the mark—if the breakthroughs happen at all. But outside of quibbles over timing, there’s something more fundamentally questionable in his vision: he has said on multiple occasions that he wants humans to become (at least) a Kardashev Type II civilization—and the concept has caught on, becoming trendy among “tech bros.”
To any deeply nerdy sci-fi fans (guilty!), this is already a familiar idea. In the 1960s, as the U.S. and the Soviet Union engaged in a breakneck-pace space race, many scientists seriously pondered the near and more distant future, including what it would mean for humanity to become a permanently spacefaring race.
One of them was Nikolai Kardashev, a Russian astrophysicist. In 1964 he proposed what is now known as the Kardashev scale, a way of categorizing a civilization’s technological advancement using energy production as a proxy; the idea was that as a society’s tech scaled up, so, too, would its need for power. The scale has three broad categories: A Type I civilization can capture and utilize all the energy it is possible to generate on a planet—usually simplified as all the light that reaches the planet from its star. Type II could capture all the radiant energy from a star. And Type III could do so for an entire galaxy—presumably using humongous armadas of solar panels to trap all that ambient energy radiated into space.
While oversimplified, in some ways, it makes sense. After all, interstellar travel and communication require absurd amounts of energy—simply staying home does so as well as our technological capabilities grow, whether you consider “home” to just be our Earth or the entire solar system. And the most obvious and accessible energy source would be light from any nearby star.
Most estimates put humanity around Type 0.7 currently but with plenty of room for further growth, which sounds about right to me. We haven’t come terribly close to tapping into all the solar energy we can use; ditto for things like nuclear power (including the dream of fusion power, which is always seemingly 20 years away).
But for all the growing we might do, I’m not at all sure how we’ll actually do it. It’s tricky to extrapolate our current progre