In 1964 Nikolai Kardashev reasoned that the most fundamental way to classify how
advanced a civilization was was based on its energy consumption. The more energy
they consume, which means control, then the more sophisticated the civilization
must be. Kardashev have even proposed a scale for quantifying how advanced
civilizations are. He called a civilization type 1 if it was able to
harness all of the energy striking its planet from the parent star, which for
the Earth is about 1.7 x 10^17 watts. Such a
civilization should have complete control of their planetary environment,
weather and resources as well as their local orbit. Going further, a type 2
civilization would have a power consumption comparable to the output of
a star, which for the Sun is 3.8 x 10^26 watts. Such
civilization would be using stars as engines effectively, harnessing them
using constructions such as Dyson spheres perhaps. Finally, a type 3
civilization would have a power consumption comparable to a galaxy -
that's something like 5 x 10^36 watts.
Such a civilization would be so advanced it's very difficult for us to make any
kind of predictions about what they would be like and thus there's probably
not too much point worrying about type 4 or 5 or 6 beyond that either.
You might wonder, where does humanity fall on this scale? Well it was Carl
Sagan who extended Kardashev's idea to a continuous scale by noting that the
energy levels are logarithmically uniformly distributed and this one can
fit a straight line through the log of these three power levels. So I'm showing
you the three energy levels here, let's repeat Sagan's calculation and fit the
three power levels assuming a log linear law. This gives us the following equation
for our Kardashev level, K, where P is the power used by our civilization in Watts.
Now, last year in 2017, humanity's average power consumption was
17.9 terawatts, that would give us a Kardashev score of 0.60.
Yet you might say that 0.60 isn't too far off one point zero but remember
this scale is logarithmic. So in order to go from 0.60 to 1 we have to
increase our power consumption by a factor of *10,000* [correction!]. Now there are those
out there who would say no problem, humanity's growth is itself exponential
and thus we should achieve type 1 status in a matter of centuries. But if you get
a calculator, you can calculate when we will attain type 1 status the answer is
in about a hundred years. But does this check out? Okay so here's the average
power consumption of humanity over time and at first glance you know such a
claim seems reasonable, it does look exponential. If we take the logarithm of
the power axis there, then the growth certainly looks exponential even in log
space up to the mid twentieth century, and that's something we call "hyper
exponential" growth. But in more recent decades, that hyper exponential growth
behavior has shut off and so clearly extrapolating this data into the far
future is going to be sensitive to what model you assume. Okay so let me show you
four models that I fitted to this data set. First, the most common is the
exponential, and a hyper exponential in red and orange respectively. Then, a
logistic and a hyper logistic model are coming in green and blue. A logistic
function looks like a leaning S and it mimics the growth of biological
populations which tend to explode and then saturate at some maximum capacity
level. Now, as you can see, all four of these models do a pretty good job of
explaining the current data but if we go forward in time they give very different
predictions about the future. The exponential model sees us becoming a
type 1 civilization by about 4100 AD, whereas the hyper exponential is far
sooner in the mid-2300's. Now whilst those numbers seem promising both of the
logistic functions predict we'll actually stabilize our energy consumption
way before becoming a type 1, predicting a maximum Kardashev score for humanity
of something like 0.65. Now the real point here is to show you that you can
come up with a wide variety of seemingly plausible models to explain the current
energy trends we've seen in the last couple of centuries, but extrapolating
those models into the far future leads to wildly different predictions. But for
the sake of this video, let's be optimistic - let's assume that we do not
saturate at some capped energy level but we keep on growing up to type 1 status.
So what would that even look like? How would we increase our energy by a factor
of *10000* [correction!]. Today, humanity gets its energy consumption from a variety of
sources such as fossil fuels, geothermal, nuclear fission, wind, waves, tides and
solar. First off, fossil fuels are really not a contender as a pathway to becoming
a type one civilization, because even at current levels of usage we're likely to
dry up our oil reserves in about a century, let alone if we increased our
energy demand by a factor of *10000*. It's really not a candidate, and that's not
to say anything about the stupidity of turning your home planet into a giant
greenhouse. But what about using the Earth itself?
Let's take wind and wave power. Well, the first thing to note there is that wave
power is largely driven by the wind, so you can't really double dip on both.
There is some debate about exactly how much energy is contained within the
Earth's winds, but we do know of course that winds are ultimately generated by
the Sun's energy warming up the atmosphere. So a starting point is to
note that the Earth's surface absorbs about 9 x 10^16 watts of
Solar radiation. Now that power warms the entire Earth but wind power is generated
by the residuals, the thermal differences between regions. In 2004, Vaclav Smil
estimated that at best about two percent of this incident energy ultimately gets
transferred to the air in the form of kinetic energy, and so wind power has
to be less than this number. So put together, wind power - and by proxy wave
power - would have a maximum theoretical power level of about 1800 terawatts, and
that's assuming 100% efficient energy extraction.
Now what about tidal energy though? Tidal energy is different it is generated not
by Solar radiation, but by the gravitational influence of the Moon and
the Sun. The total amount of power dissipated through tides by the Earth's
oceans is now well determined with techniques such as altimetry,
satellite and lunar laser ranging all agreeing on a value of 3.7 terawatts. And
it's a similar story for geothermal energy, which is ultimately driven by the
internal heat of the Earth itself, that gives you about 47 terrawatts. Again not
at the right level for what we need. Now this just leaves us with two contenders
left in the game, solar energy and nuclear energy. Present-day nuclear power
plants use fission to generate their energy, that's the splitting of heavy
atomic elements. But it has long been a dream that we could exploit the nuclear
fusion process in the future, that's the combination of lighter atomic elements
together. Now it's a long-running joke that nuclear fusion power plants are
always 40 years away from us, it never seems to get any closer, but let's just
make the assumption we'll figure this out one day and we will have nuclear
fusion power. Now nuclear fusion can happen with the combination of really any two
elements you want, but the most energy efficient process identified for nuclear
fusion power plants is the combination of deuterium and tritium. Now these two
are heavy isotopes of hydrogen, which is a fancy way of saying they just have
extra and neutrons in their atomic nucleus than a hydrogen atom does. Now
fortunately there's no shortage of deuterium here on the Earth, there's something
like 40 trillion tons of the stuff just in our oceans. Tritium however is far
rarer. It's only found in trace amounts inside water so typically it is produced
by the reaction of free neutrons and lithium inside nuclear reactors. That
sounds great, but lithium is also a fairly rare commodity - there's only
about 30 million tons of the stuff in the ground, in the reserves that we have,
but there's probably an extra 200 billion tons of the stuff dissolved in
seawater. So if we had access to all of that lithium that's dissolved, we'll be
able to make something like 90 billion tons of lithium. Now since each
deuterium-tritium fusion reaction creates 17.59 mega electron volts of
energy, we would expect a total amount of energy that we could extract from
nuclear fusion would be something like 5 x 10^28 Joules. That would be
enough to power a type 1 civilization's energy needs for approximately 10,000
years. So nuclear fusion could be a viable pathway to becoming a type one
civilization but what about solar well of course solar energy is generated
from the Sun and it's important to remember that the Sun is, in essence, a
giant nuclear fusion power plant in the sky.
Now on the Earth one of the big problems with nuclear fusion is confinement, how
do you keep this hot plasma together at extreme enough pressures and
temperatures in order to kick-start the nuclear fusion process? But on the Sun,
confinement happens for free, it happens from the own self gravity of the star
itself. Yet more, space is very empty and thus the transmission of energy from the
Sun to the top of the Earth's atmosphere is essentially lossless. Finally there is
clearly enough power to become a type one civilization from solar because
that's actually how we define a type one civilization - it's one which uses all of
the solar radiation incident upon its planet. So all you need to do is tile all of
your planet with solar cells and hey, you're a type one. Now you might say, wait where
would I live? Well this doesn't mean there's no living space, it just means
all of the living space is underneath the solar panels. However, even this
extreme scenario is probably not enough because solar cells are not 100%
efficient. Modern solar technology is something like 25% efficient and
there are some laboratory demonstrations which approach 50% efficiency, but a 100%
efficient solar cell is impossible. And that's because the
maximum theoretical efficiency of such a device is governed by the ratio of the
temperature of the receiver to the temperature of the emitter - in our case
that's the Earth to the Sun. The so-called "Carnot efficiency" of this system
would be, at best, 95% - we could never do better than that.
And you might say, no worries, I'll just build a giant solar cell farm in space
and beam the energy back to the Earth, but even that has some problems the
conservation of energy now becomes your enemy. Energy cannot be destroyed or
created, it can only be transformed from one form to another and that's not some
Jedi doctrine, that's the first law of thermodynamics. If a civilization uses a
certain amount of energy to power their civilization that energy doesn't just
disappear after they're done with it, it becomes waste heat, it warms their planet.
And that statement is true no matter what your energy source is be a solar,
nuclear or antimatter. Right now the waste heat generated by humanity's
activities is so minuscule it really doesn't make any difference to the
temperature of the planet, but for a type one civilization it's a different kettle
of fish. One way to calculate this is to take the solar energy scenario, and I'm
going to walk you through a very simple calculation for the equilibrium
temperature of the Earth that's a very basic calculation we often give our
students in intro level classes here. Using the Stefan-Boltzmann law, one can
show that a planet's temperature approximately equals this, where I've
labeled here the various terms for you. The albedo term is the key here, that's
how much light is reflected back into space without ever being absorbed by the
planet. For the Earth it's about 30%. Now if you are a type one civilization you
do not want 30% of this solar radiation to be reflected back into space,
that's energy that you need to power your civilization.
So by tiling your planet with very efficient solar panels, you essentially
make your planet very very dark, dropping the albedo over here down to zero. So
hopefully you can see from this equation, that if I decrease the albedo I'm going to
raise the temperature. And in fact it would raise the Earth's temperature by
about 24 degrees Celsius or 43 degrees Fahrenheit, and that's really huge, it
would render large portions of your planet completely uninhabitable. And you
can't really geoengineer your way out of this problem either, for instance the
idea of building a giant space based mirror, such as in the trailer
Clara that we did in the last video, that's not gonna work because then
you're reflecting away the very energy that you need to power your civilization.
And switching to a different energy source than solar, say nuclear power, is
really not going to help you. In fact it's going to make things even worse, because now
not only do you have to dissipate all of the waste heat generated by your nuclear
reactors, but you also still have to get rid of all of that energy which your
planet is absorbing from the Sun anyway. You have twice the problem to deal with.
So no matter how you look at it, becoming a type one civilization is going to
cause your planet to warm up. So I would claim that a type one civilization maybe
has two options for getting around this, let me know if you have other options.
You can think of one would just be to build a giant air conditioner have
everybody live inside and keep those small volumes cool. Okay.
Another option, which might be a bit more realistic I think, would be that to relax
this assumption that we have to live on a single planet - to let our civilization
spread out to the other planets and moons in your solar system. That way you
don't have to dissipate all of the energy in a single location, it allows you
to keep each of those bodies a bit cooler. So hopefully I've convinced you
at the end of this video that becoming a Kardashev type one civilization would
dramatically change our way of life, it's not going to be business as usual. Now
scientists like myself do these types of thought experiments and calculations
because ultimately we're interested in what these
realizations would look like in our telescopes, and the only way you can
really figure that out is to sort of put yourself in their shoes and imagine what
your planet would be like, which is kind of what we've done in this video. If
you're interested in the detection of such civilizations I'm actually helping
to organize a meeting about that topic in Houston later this month, so stay
tuned on this channel for more videos after that meeting, where I'll tell you
about some of the technosignatures people were getting excited about. Hey if
you've got this far through the video then you must have enjoyed the content
so please consider subscribing to our channel. I bet this video will generate
some pretty interesting comments and questions so please do put them down
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stay thoughtul, stay curious.