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
below and I will try to get back to you.
So until the next video
stay thoughtul, stay curious.
