A special thanks to Brilliant, our sponsor for today’s video,
whose online course provided the inspiration for what you’re about to see.
It doesn’t take much to learn that the Earth is facing an energy crisis. Fossil fuels are finite,
but also represent 80% of the source of our electricity. At some point we will inevitably
run out – whereupon we will either need to get our energy from somewhere else, or brace ourselves for
the shocking reality of a world without machinery, computers and phones. If the idea of pushing a
plough all day in an agrarian society doesn’t quite align with your life goals, then you’ll
be in favour of the alternative – finding a different energy source for most of society’s
energy needs, once the oil, coal and gas runs out. You’ll likely have heard of options like wind,
geothermal, or tidal power. But do these approaches dream big enough?
Could the answer to the energy crisis actually be something that sci-fi writers
have been talking about for over 60 years? Although it’s a long way off, could humanity
actually build a Dyson sphere one day? And just how far off are we from being able to do this?
I’m Alex McColgan, and you’re watching Astrum. Join with me today as we examine the case for
Dyson spheres, and discover how the maths behind these gargantuan structures might
make them not just possible, but actually plausible for our future energy supply.
I was recently going through an online course when I came across the topic of Dyson Spheres, and they
really caught my imagination. Dyson spheres are crazy. They were first explored in a paper
by British-American theoretical physicist and mathematician Freeman Dyson, who was considering
the way hypothetical alien civilisations might try to power their society, and how we might
spot them. All life requires energy to live, and the more advanced a society, the more energy it
seems to end up needing. Dyson thought that if an alien race was space-faring, they might
build a habitat in space near their local star to take advantage of its solar radiation. Over time,
more and more habitats would be built, until one day most or all of the star would end up
surrounded by a truly mammoth shell of habitats, which would capture and utilise all the radiation
the star was emitting. This shell was eventually considered one single structure, and came to be
known as a Dyson Sphere. Creating one would give a species access to a ridiculous amount of energy,
sending their civilisation into the next stage up in galactic exploration and expansion.
Dyson got the idea after reading a science fiction book known as Star Maker,
something he publicly credited. And indeed, this idea does sound a little like something
out of sci-fi. It would be very hard, and potentially take a very long time to build
anything so large, and seems to be well beyond the capabilities of our own current civilisation.
That said, this sci-fi idea might need to be something we consider a little more closely. As
the course I was learning from pointed out, there are just over 8 billion humans on Earth right now,
and we collectively use 4x1020 Joules (400 quintillion Joules) of energy per year. This
sounds like a lot, and it is, particularly when you consider that the current estimated amount
of remaining energy available in oil reserves is 6x1022 J (60 sextillion Joules). Doing a
little division, it becomes clear that we only have 150 years of oil reserves left
if we continue burning it at our current pace. 150 years is really not that many.
And given how quickly we are ramping up energy consumption globally,
it’s fair to assume that we might run out of oil sooner, even if more reserves can be
found. I talk a little more about this subject in another of my videos here.
Which is why finding another mass source of energy, such as utilising the energy available
in sunlight, actually is quite appealing. Compared to what we gain from fossil fuels,
the Sun produces a staggering amount of energy, even if you’re only considering the
amount of light that hits our planet’s surface directly. Let’s use a little equation to show
you what I mean. At this distance, the energy we receive from the Sun is around 1360 J/m2s.
Multiply this across approximately 1.1x1014 m2 (110 trillion) of the Earth’s circular
area as it cuts through space, then multiply this again across the course of a whole year
(all 31,536,000 seconds of it), and we would receive around 4.7x1024 J of energy – that’s
10,000 times the energy we are currently using from oil. More than enough to cover our needs,
assuming we could harness it. 1360 J/m2s x 1.1x1014 m2 x
31,536,000 s = 4.7 x 1024 J Obviously, capturing all that
sunlight is a bit tricky to do in practice. And obviously, if we were to capture all of it,
that would make life a bit difficult for any plants on the planet wanting to use that light
for photosynthesising purposes. But even if we got to the point where we were using only half of all
that available energy, we would completely remove our need for fossil fuels, and could have the
energy necessary to support a significantly larger population at the same time. Forget 8 billion,
we could sustain 40 trillion people here on Earth. At which point, the biggest problem wouldn’t be
how to give all those people the energy you’d need to maintain their lifestyles, but where
to put them all. Increasing the population density by 5000 times would go from there being on average
7 people per square kilometre to being 35,000 people per square kilometre, or one person per
3cm2. So, making this work might be a bit of a challenge without some creative housing plans.
Regardless, this does seem like a good solution to the energy crisis. The joules are there. So, if we
can already cover our population’s needs by fully accessing only a small fraction of the Sun’s total
output – the part hitting the Earth – we probably don’t need to harness any more of it just yet.
However, looking to the future, that won’t always be the case. Reaching 40 trillion people is
actually not that far off – at least, on the scale of human history. Our population is currently
growing at a rate of 0.88% a year. At times this number has been as high as 2%... For simplicity,
let’s just take a nice round 1% figure, and calculate using that. If we increase
the population size by 1% every year, the cumulative growth of the population would
hit 8.8 billion in a decade, 22 billion in a century, and 40 trillion in 800 to 900 years.
So, what might be the solution when that happens? Why, doing as Dyson’s
hypothesised alien races do, and increasing the amount of solar energy that we capture,
probably by building solar panels or mirrors and sending them into orbit around the Sun.
As the course I was learning from highlighted, with more solar collection tools comes more
benefits. A Dyson sphere – or a Dyson swarm, as this segmented configuration is technically
known as – offers power that’s many orders of magnitude higher than what we can do with just
a planet’s worth of surface area. Harnessing it would elevate us to a higher level of
civilisation – one that went from controlling its planet to harnessing its entire solar system,
perhaps giving us the springboard that could truly kickstart our expansion across the stars.
On the Kardashev scale - a method of measuring a civilisation’s advancement by evaluating how much
energy they could potentially use - this would tip us from a type 1 civilisation into a type 2. In
case you’re wondering, we’re currently only about a Type 0.7, as we’ve not quite managed to make use
of all the energy on the planet, while a Type 2 would have access to all the energy in the Solar
System. To get to a Type 3, we’d have to harness the entire galaxy, so that’s a long way off.
Still, the energy levels a Dyson sphere could produce are already so extravagant,
it seems silly to our current understanding to even contemplate them.
If we completed a Dyson Sphere or a Dyson Swarm, we would go from 4.7 septillion Joules to 10
decillion Joules; increasing our energy levels by 20 trillion times. That should be enough to keep
the lights on for the foreseeable future. Technologically speaking, we are pretty
much already at the point where we could make a solar panel that could capture sunlight from the
sun and send it towards Earth. Or even easier, we could simply create space mirrors to reflect the
light towards where we needed it, say an orbiting space foundry outside of Earth’s atmosphere,
with the same end result. This might be the simpler idea as then you don’t have to worry
about how to transfer the generated electricity from the solar panel back to Earth - you can
just send the sunlight directly to wherever it’s needed (although you would be sacrificing some
habitability on the dyson sphere itself). Placing mirrors into stable orbits is not impossible for
us, and having them be able to manoeuvre slightly to reorient throughout the year doesn’t sound too
implausible. So then it’s just a question of how much materials would this require. Unsurprisingly,
depending on what distance you created your shell, a Dyson sphere would need a
LOT of material. For instance, the course I was learning from identified that building
a Dyson sphere that coincided with the Earth’s orbit would need about 6% of the entire volume
of the planet even if the panels were less than a millimetre thick. This is hardly ideal,
even if we could selectively drill out the materials that we needed. But if we
instead built the sphere at a much more compact distance to the Sun – say, at the
distance of Mercury’s orbit – then the material requirements become much more feasible.Mercury
itself likely contains all the raw material that might be needed for such a structure, and as far
as we know there is no-one living on Mercury who would complain if we were to fill it with holes.
But then the last issue to consider - other than the moral question of whether it’s ok to
tear apart an entire planet for purely our own benefit - is that this is obviously an
energy intensive process. Materials have to be mined, processed, and then made into their
components. The solar panels or mirrors would need to be built, and even once that’s done,
they need to be lifted out of Mercury’s gravity well – and that’s a particularly
energy-intensive process. If we utilised all the Sun’s energy that was hitting the planet Earth,
and spent it all on doing nothing but lifting mirrors for our Dyson sphere out of Mercury’s
orbit, we can calculate how long it would take us to lift enough mirrors to complete the entire
shell. We know the formula for overcoming the gravitational binding energy of Mercury:
E=3GM2/5R [where G is the gravitational constant,
M is Mercury’s mass, and R is its radius) Which for Mercury gives us roughly 2x1030
J. We already know how much energy we at maximum could get from sunlight here on Earth:
4.7 x 1024 J. So then it’s just a simple matter of dividing the first by the second.
And voila. This process would only take a measly 425,000 years. During which time, there would be
no energy left to support Earth’s population, or give light to our plants, because we were using it
all to build the Dyson Sphere… Hmm. Maybe this isn’t
such a viable idea after all. But wait. There’s one last point to
factor into this. That’s the fact that once our mirrors came online, they could start providing
energy of their own to help pay the energy costs. This would then become an exponential process,
with no additional input required from Earth, perhaps except for a little oversight. One mirror
would provide energy to make a second. Then both would double to make 4. Every instance you would
be doubling your number of mirrors, and once you get exponential growth involved, depending on how
much energy you put into the system at the start, the entire thing could be completed much sooner…
According to some calculations, Mercury would be completely disassembled in as little as 31 years.
In other words, if we started building one right now, you might live to see its completion.
Ethical considerations aside, such numbers really bring into focus the viability of
this project. Something that takes half a lifetime to complete is certainly ambitious,
and the initial cost might indeed be great. There would be some practical considerations
to think about in terms of the best way to set up mining operations on Mercury.
But these are questions we’re already putting our minds to anyway. Scientists
are currently working out how to set up bases on the Moon, with similar intentions. We’re
not far away from doing the same on other planets, once we have the techniques down.
In other words, there really aren’t very many barriers left towards attaining the
immense energy of the Sun. A Dyson sphere might well be another example
of something that sounded like science fiction to us, but will turn out to be
something our children or grandchildren will one day come to take for granted.
As I mentioned at the beginning, Dyson spheres weren’t something that I just arbitrarily
started thinking about. The springboard for this thought experiment started when I was
looking through the courses of the sponsor of today’s video, Brilliant. Brilliant is an online
learning platform that has thousands of different lessons for STEM subjects such as mathematics,
computing and science. Specifically, I was looking through their course “Physics of the Everyday”,
where their interactive lesson all about Dyson spheres delved into the maths I explored here,
and even a little I only touched on. If you want to better understand the
mathematics involved in Dyson Spheres and more, or want to develop your skills and
expand your knowledge in other areas in a fun way, why not give Brilliant a try?
They have new lessons released every month, and they’re bite-sized enough
that it’s easy to take it at your own pace. Scan my QR code or click my link
in the description below to go check them out – the first 30 days are free,
and the first 200 of you to sign up will get 20% off Brilliant’s annual premium subscription.
Thanks for watching. If you liked this video, maybe you’d like this video too
about colonising Mars. A big thanks to my patrons and members. If you also want your name added to
the end of every Astrum video, check the links below. All the best, and see you next time.