PBS Space Time

Imagine a world where humanity masters every planetary resource available to itour first step on the famous Kardeshev scale of technological advancement.

How distant is that step?

Will we even become a true Type-1 civilization, and how can we get there?

In 1964 Soviet physicistNikolai Kardashev proposed a method for measuring the technological advancement of a civilization.

The Kardashev scale has become a go-to metric for what technologically advanced civilization might be capable of.

Its based on amount of energy commanded with a Type I Civilisation controlling access to all available energy on a planetary scale, a Type 2 accessing an entire stars energy output, and a Type 3 harnessing energy from a galactic scale.

Fun side note: Kardashev originally came up with this scale in a paper discussing the detectability of alien civilizations, because the distance over which an alien broadcast might be detectable depends on how much energy is pumped into that transmission.

Despite this modest intended application, the whole idea of the Kardashev scale really captured the imagination of both scientists and science fiction-ists.

Exponential advancement on a cosmological timescale implies frighteningly vast differences between between civilizations born at different times, and Kardeshev captures that.

Type 2 and 3 civilizationsmastery of one or many stars respectivelyare the stuff of extreme sci-fiwere talking Dyson spheres, black hole engines, artificial worlds, galactic empires, and warping the fabric of space for fun.

By comparison, the Type 1 civilization is just getting started.

Maybe its traveled to the nearest star systems and terraformed a planet or two at best.

Humans would be Type 0.

Maybe 0.5 at best.

But if we hope to one day become a super-civilisation; roaming the galaxy, mastering the fundamental constituents of reality, and finally making contact with the aliens who have been waiting for us to graduate technology preschool we need to start somewhere.

And that means becoming a Type I civilisation.

So whats it going to take for us to get there.

Theres a lot more to becoming a stable super-civilization than energy consumptionincluding some messy geopolitical stuff that Im neither qualified nor have time to cover in a short YouTube videoso today were going to stick to Kardeshevs simple criterion and ask what will it take to attain the defining energy resources of a Type I.

In that 1964 paper, Kardeshev actually says that humanity is close to the technological level of a Type 1 civilization and defines a Type 1 power capacity at roughly the current level.

But he was speaking quite loosely, and these days we tend to think of Type I as already having access to planetary-scale energy resourceswhich is a factor of 10,000 times higher than what we currently use.

So thats the thought experiment for todaywhat does it take to master planet-scale energy.

Lets attach a number to that statement.

How much energy can we access from the safety of our home planet?

We want a stable civilization, so were just going to consider renewable sources.

Besides, a proper Type 1 would burn all of the energy locked up in Earths fossil fuels and accessible fissionable material like uranium in a couple of days.

Renewable sources like wind and waves contain a lot of energy, but the amount is piddling compared to the amount of solar energy that hits the Earth.

And that makes senseultimately, almost every source of energy in the atmosphere or biosphere comes from the Sun.

So we actually have a very easy way to estimate the energy use of a Type-1 civilizationits the amount of solar energy hitting the entire planet every day.

And directly collecting solar energy may also be the easiest way to access that power.

So a sun-powered Type-1 will be our first consideration.

There is another way we could become Type-1 that may yield even more energy, but Ill come back to that.

The average solar irradiance at the Earth is 1361 W/m^2, and our planet intercepts that energy over a disk with the Earhts radius, giving us an upper limit of 1.7x10^17 Watts to play withlets say 10^17 Watts.

To put this into perspective, we currently use around 10^13 watts globally10,000 times shy of our Type I goal.

Collecting anywhere close to 10^17 Watts in solar power is going to take a lot more than covering the planet in modern solar panelsnot that wed want to do that anyway.

The first program in upgrading our Kardeshev scale is improving our solar collection capabilities.

So lets start by learning a bit more about solar cells.

The most common solar cells are typically made from silicon and are an application of semiconductor technology that we discussed here.

To summarize, you have two layers of silicon, each mixed or doped with a different element.

One of these doped elements grants an extra free electron to its layerthis is a p-type senmiconductor and on its own those free electrons allow the flow of current.

The otherlayer doped element subtracts one electron, creating an electron hole and an n-type semiconductor.

And those holes can also flow as a current.

Now if you splice those lakers together, the free electrons diffuse from p-type to n-typeacross the p-n junctionto fill the holes, at which point the system is non-conducting.

But if you provide energy to those electrons they jump back across the p-n junction and are able to flow around any circuit that the device is attached to.

This is exactly how transistors work, with the energy being provided by a small electric potential.

In solar cells, the energy is provided by incoming photons in a process called photoexcitation.

In a solar panel, a circuit provides a path for those electrons to return to the n-type layer and their energy can be extracted en route.

But theres a fundamental limit to how much energy a solar cell can extract from light.

This is called the Shockley-Queisser limit.

There are a few effects that go into determining this limit, but for now lets focus on one of the big ones: spectrum losses.

The energy required to move an electron between layers is a very specific number: typically the energy of a near-infrared photon.

Photons with less energy, which means most infrared, do nothing at all.

Photons with more energyall visible and ultraviolet lightwill excite their electron, but the excess energy gets lost as heat.

The photons in sunlight come with a very broad range of energies, so some loss is inevitable, with an efficiency limit of around 50%.

Other effects drag the efficiencyShockleyQueisser limitdown to around 30%.

In practice we've only just cracked 25% efficiency at the moment.

But this is for traditional solar cells with a single p-n junction.

Newer designs and materials offer the potential to exceed this limit.

For example, layered p-n junctions tuned to different energy photons can capture a wider spectral range without wasting energy.

Certain special materials like perovskites have a similar advantage.

Quantum dots are another exciting possibility are quantum dots thanks to their tunable absorption spectrum.

In general, advances in materials science and nano-fabrication are likely to boost us over 50% efficiency.

Even more important than conversion efficiency is where we put these cells.

Space-based solar power has a major energetic advantages.

Our atmosphere blocks most UV light, but in space those UV photons increase the overall available energy for solar cells by a factor of 10.

Also theres no night-time in space, which adds another factor of two.

And of course, its nice that we dont have to cover Earth in the things, leaving more room for the humans or our AI overlords to inhabit our Type I world.

A major challenge with space-based solar is getting the energy back to Earth.

The most viable candidate is microwave power transmission.

2.45 GHz photons pass easily through our atmosphere.

Pulses of these would be collected by receiver antennae called rectennas which would convert those photons back to electricity.

Or maybe we finally build that space elevator to send people up and channel power down.

So were really looking at swarms of solar arrays orbiting Earth or in co-orbit around the Sun or at Earths Lagrange points.

With the James Webb Space Telescope, weve demonstrated that were able to send large, fragile things into space.

To achieve our 10^17 Watt power source well need an array quite a bit larger than the flattened disk of the Earth in order to make up for the losses, which will never be zero.

Thats more than a hundred trillion square kilometers a lot of solar collectors, and if we scale down our silicon solar cell thickness by a factor of 10 thats still a few trillion kilograms, not including supporting structure.

Fortunately silicon is the second most abundant element on Earth after oxygen, so a few trillion kilograms is nothing.

Add a bit of asteroid mining for the supporting infrastructure, this feels distantly doable.

And of course this will put our new Type I civilization on track to Type II just keep building arrays until we wreath the entire Sun and we have an effective Dyson sphere.

Solar is the most obvious path to Type-I-dom, but it may not be the best.

Remember that the Sun generates energy through nuclear fusionby smashing together hydrogen nuclei to make helium, and converting a small fraction of the mass into energy.

So rather than being content to soak up the energy that the Sun happens to radiate our way, why not build our own mini-Suns on Earth?

Lets talk about artificial fusion.

In the Sun, particles are smashed together and fused into new, heavier nuclei in a series of reactions known as the proton-proton chain.

It starts with lone protonshydrogen nucleiand ends in Helium-4 nuclei.

The most energy is obtained during a particular step of that chain, when two types of heavy hydrogendeuterium and tritiumsmash together to form helium 4.

About 0.4 of 1% of the mass of the ingoing particles is converted into energy, mostly in the kinetic energy of an ejected neutron.

That doesnt sound very efficient, but remember, E=mc2 describes the conversion of mass to energy, and the c2 does some heavy lifting here.

Deuterium-tritium fusion releases four times as much energy as Uranium fission gram for gram.

That means to reach our Type-I energy goal of 10^17 Watts wed need to convert a few hundred kilograms of heavy hydrogen into helium per second.

Fortunately we have a massive supply of deuteriumIll come back to the tritium.

Earths oceans contain around 1.4 billion billion metric tons of water, one eighth of which is hydrogen by mass, and 0.016 percent of that is hydrogen is deuterium.

If we burned the oceans deuterium, wed be able to power our Type 1 civilization for a few million years before running out.

And if we cant make it to Type 2 by then, well, maybe it wasnt meant to be.

Having the fuel for fusion is one thing, but we also have to have the reactors.

How long before we have that?

Commercial fusion is famously 50 years away no matter when you ask.

That said, there are major programs to bring this to reality.

The most promising approaches use powerful magnetic fields to confine an extremely hot plasma, trying to duplicate the crushing effect of the intense gravity in the core of the Sun.

Perhaps the most famous is the International Thermonuclear Experimental reactorITERin France; a type of reactor called a Tokomak.

There are other magnetic confinement projects and designs, and also non-magnetic and non-confinement options, but thats not for this video.

Currently magnetic confinement seems most promising for commercial reactors, and ITER is the furthest along.

There are still many challenges to overcome before magnetic confinement fusion is commercially viablefrom dealing the the plasma instabilities to safely extracting the energy from the extreme-energy neutrons produced in fusion.

The main issue is getting more energy out that you put in to get the reaction started and maintained.

And that seems to be a matter of scale.

Larger reactors should have an easier time doing thatand this is the great hope of ITER, with its proposed 500 MegaWatt output supposedly only needing 10% of that to sustain the reaction.

This is scheduled to come online in around 10 years or 50.

OK, back to the question.

Assuming we get fusion technology, how many reactors do we need to power our aspiring Type-I status?

Lets say we build many ITERs.

We only expect a fraction of its output to be convertible to electricitythose neutrons are hard to catch.

At 20% efficiency wed need 100,000 reactors to power our super-civilization.

That is a lot, but its not utterly preposterous.

If we double efficiency and scale reactor size by a factor of 10 then 5,000 reactors scattered across the globe will provide every Watt well need for millions of years.

But with great power comes great need for storage and distribution of that power.

That means the development of a planetary-scale supergrid.

Rather than stringing lossy copper cables across the planet, were going to want to parallel-track development of high temperature superconducting cables.

Underground networks of, say, yttrium barium copper oxide can distribute our new extreme current density with minimal power dissipation, thanks to their zero resistance when they become superconducting.

Challenges here include the fact that even high temperature superconductors need to be cooled quite a bit, which means both energy and cumbersome piping.

The energy part we seem to have sorted, and were going to require those chunky pipes anyway due to the typical brittleness of superconductors.

This is stuff that companies are working on today, so we can hope its sorted by the time we need it.

OK, so we have a couple of paths to Type-1-civilization-hood.

But now that we have a completely ridiculous amount of energy, what do we do with it?

Why did we go to all this trouble anyway?

Honestly, maybe we didnt need to.

Maybe we can settle down and live in modest harmony with our planet and chill on these expansionist tendencies.

Maybe its juvenile to obsess over some made up metrics in a soviet paper from the 60s.

But seeing as we got this far, and we have an imaginary Type-1 civilization, we may as well do something with it.

Part of being a Type I civilisation is the ability to not just harness the energy on Earth, but to be in control of its natural forces.

We now have access to energy on the same scale as the atmosphere and the ocean, and so can, presumably, change them for the better.

So I guess we start out by saving the planet, reverse climate change and all that, now that we actually plan to stick around as a species for a while.

They say if you have a hammer, every problem is a nail.

But energy is the most versatile hammer there is, and its the ultimate currency of problem-solving.

Near limitless clean energy can enable colossal scales of resource gathering and manufacturingfrom mass-scale desalination and farming to asteroid mining, advanced manufacturing, building perfect cities for all peoples.

We could turn the Earth into a paradise of abundance.

Assuming we also solve all world conflicts, which energy cant do directly although surely eliminating scarcity helps.

Energy is information and power is computation.

Our supercomputers will run hot and grind out solutions to all technological challenges and unlock the secrets of the universe with sheer brute force processing and unthinkably capable AI.

Well duplicate our energy facilities to power the terraforming of other worlds, creating simulacra of our Earthly paradise.

And so humanity will claw its way towards the next levels of Kardashevs scale.

Or we might just spend the energy mining Kardeshev-coin and training our AI successors.

But whether its us or them, Earth will be on track to spawning a civilization of the Type II, soon mastering the energy of an entire star, and then of many.

And then maybe we look back at Nicholai Kardeshevs little paper and realise that we are the beacons he imagined, and that weve announced our presence to new Type-0s still emerging across galactic spacetime.