Rethinking the Kardashev Scale

We need better resolution on the problem.

The Kardashev is a staple of discussions about the development and colonisation of space. Initially proposed as three discreet classifications of civilisations by Nikolai Kardashev in 1964, where a Type 1 civilisation would control the energy of a planet, a Type 2 civilisation would control the energy of a star, and a Type 3 civilisation would control the energy of a galaxy . It was later refined into a continuous scale by Carl Sagan using the following formula.

We are supposed to be at 0.73 on this scale - something I dispute below - and our objective should be to ascend to 1 and then 2 by expanding out into space. Here it overlaps with the work of Freeman Dyson, who in a 1960 paper suggested that an advanced civilisation might trap all the energy of its host star and that this might lead to distinctive infrared sources astronomers could find. A few tentative candidates have been proposed, but none are definitive.

One thing that I’ve always objected to with the Kardashev Scale is the treatment of values less than 1. The scale dates to the 1960s, when we were still in a kind of “Man vs Nature: The Road to Victory” mode of thinking. Our energy usage was simply how much fossil fuels and uranium we burned through. At a push some would consider agricultural use of sunlight. Since then we have been more conscious that we exist in the context of an ecosystem, and I argue that from the perspective we have, since making the entire planet accessible in the 20th century, been using all of its energy in some way or another.

For example, we have chosen not to cut down the entire Amazon rainforest and turn it into pasture - we could do that technologically, but we (mostly) value the environment there as it is - and thus we are ‘using’ the Amazon as a rainforest. Covering about 7 million square kilometres, and assuming time averaged sunlight of 500W per square metre, we “use” about 3,500 terawatts continuously in this application - compared to our industrial use of only about 20 terawatts. While it may be possible to place human value on each square metre of the planet to properly calculate our use, and such a thing might be valuable in the context of environmentalism, It just muddles the issue in the case of the Kardashev scale.

In addition, the Karashev scale also lacks granularity when applied to near term space efforts. There are many steps between where we are now and capturing all the Sun's energy! Overall, I think we can find a better metric.

The Dyson Scale

What we want to know, really, is how close we are to a Dyson swarm - a density of solar collection surfaces so high that all the of the energy of the Sun is captured. This is the end point of solar system development, the subject of memes about dismantling the planet Mercury, and represents 2 on the Kardashev Scale.

To make this figure of merit manageable we do still need a log scale, but we also need one that excludes the Earth’s contribution which would drown out the energy gathered by our current space efforts.

Here is the formula that does that:

I’m calling is the Dyson Scale, and using the symbol D. We use a base 10 log (which is more intelligible for people than a base 10 billion log) and P is the power captured by assets in space. The lower term is the total solar output (4 x 10²⁶ Watts) minus the power received from Earth, but the latter term is 2 billion times smaller so can be approximated to be zero.

The scale reaches zero when we have a complete Dyson swarm, and is negative until then. The first satellite to use solar power, Vanguard 1, collected about 5mW electrical power from its tiny solar cells, which may have been perhaps 10% efficient giving 50mW of energy capture. When this was launched in March 1958, it placed humanity at around -28 on the Dyson Scale, having previously been at -∞ for all human history. Fast forward to the present day, we are around -18.

Here is how I come to that estimate.