# Practice English Speaking&Listening with: Explained: The Dyson Sphere

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So, in this video Im going to try to be optimistic about humanitys future (out

of character I know BUT I kind of have to, to setup this video). Okay, Im going to

presume that atomic warfare doesnt happen, overpopulation doesnt happen, killer meteor

that destroys everything doesnt happen, we go to Mars, setup a colony or hundred,

become a fully-fledged space-faring civilisation with bases of operations in different star

systems, everythings happy, utopian future, hurray.

But, I dont even need to go around naming achievements to justify how good a civilisation

is. Theres actually a scientific scale to measure how advanced a civilisation is,

believe it or not. Its called the Kardashev scale (named after a Soviet astronomer Nikolai

Kardashev) and it measures a civilisation on its total energy consumption, basically

how much energy is needed to keep the society going. We are here and need to be here for

the thing Im explaining to start to be realised, but you dont know what any of

this means so Im going to have to spend the next half an hour explaining it.

Its actually quite simple. As a civilisation advances in technology, it is safe to say

the total energy consumption will too, so we will progress up the scale, pretty easy

to understand. There are milestones on this scale, which define the scale of our civilisation.

Type One, here, marks a civilisation that canuse and store most energy that reaches

the host planet’, Type Twocan use and store nearly all energy output from a host

starand Type Three is like Type Two BUT FOR AN ENTIRE GALAXY. This scale is logarithmic,

the further you reach, the more energy needed to progress. We can use decimals to define

civilisations in between the milestones. Just for scale, Type One needs 10,000 Terra Watts.

Type Two needs 10 billion times more than that, and Type Three needs 100 ExaWatts of

energy, which is a staggeringly huge amount. To measure a civilisation, we can use this

equation, formulated by the one and only Carl Sagan back in whenever he did this. You replace

P with the wattage and K becomes the scale of civilisation. As of 2012, the total for

humanity is 17.54 terawatts, which if we plug that in to the formula, this means that human

civilisation is a Type 0.724 civilisation. Decent.

Right, so heres the bit I need to be optimistic about. Were going to assume that our civilisation

will keep growing and growing eventually become a Type One and then Two civilisation, at which

point we will need an entire suns worth of energy to keep us going. But how the hell

are you going to generate an entire suns worth of energy? Use a sun of course. Makes

sense. And finally, after too long a time, we get to the Dyson Sphere, you know, the

one in the title. A Dyson Sphere is a hypothetical structure

a civilisation can build around a sun that will transfer (virtually) the entire output

of that star into usable energy. If we are going to keep progressing as a civilisation,

we are going to have to build something like this in the next few thousand years, well,

according to Michio Kaku at least, but he seems like a trustworthy guy. Now, these structure

come in a variety of different flavours, to suit any civilisations needs. You can have

a plain old Dyson Sphere, or instead try a Dyson Belt, Dyson Ring, Dyson Swarm, Dyson

Hoover or Dyson Shell or some combination of these. These are all a little bit different,

but Ill explain that later. First, HISTORY. The concept of a Dyson sphere dates back to

an exciting period in history known as... the 1930s? Urrgh, thats not very exciting.

Anyway, and to a book by this British bloke about sci-fi space travel, where we see our

first glimpse of a star-encompassing structure. And, like all good inventions, its named

after somebody else. I guess Stapleton Sphere was just too boring.

Skip forward to the 1960s (dont worry, nothing really important happened in between

then anyway) and to physicist and mathematician Freeman Dyson. He proposed the same thing

that weve just discussed, that civilisations will need stars to power their societies eventually.

He then proposed one massive structure could (in theory) surround a star andcollect

its energycalling it a shell. He published a paper about it in 1960 and so the Dyson

Shell was born, which is exactly the same as a Dyson Sphere, just less catchy.

However, in his paper he didnt talk about how (in theory) you could build such a sphere,

and as a result I know what you are imagining. A hollow ball enclosing a star. Well, good

luck with that. Im not even going to talk about how hard that would be to design but

instead try to illustrate how hard it is to build, Im just going to talk about how

impossible it is to collect those materials needed to build one. So, lets make some

assumptions. You are going to build one around a star exactly

like the sun, with a radius of nearly 700,000 kilometres. The shell itself will have a radius

of 0.25 AU (37 1/2 million kilometres) and will be 1 cm thick. We are going to ignore

which impossible material you might construct it with and use steel as an example, which

wont even be the photovoltaic cells but the frame they sit on, keep that in mind.

A spheres area is 4 pi r^2. Plugging in 37,399,467,500m gives us 1.76×1022square

meters, the surface area of the sphere. We can fold this out into a flat shape, in theory

because there is no perfect representation of a sphere in 2 dimensions, but weve assumed

a lot of things so far so lets not worry. Multiplying by 0.01 metres (1cm), this gives

us 1.76×1020cubic meters of material needed, which is a number that Im not going to

pronounce because this video might last until the next Olympic Games if I do. Go Tokyo,

woo! Provided the steel has a 1% carbon content and therefore 99% percent iron content (1.7424e+20),

and presuming 80% of the Earths core is iron, we would need 23 Earths cores to

supply the iron to make just the frame for it. Nearly two-dozen massive planets mined

hollow. This is ridiculous, what am I doing with my life.

We are going to have to completely obliterate entire solar systems, presuming they have

as massive a planetary system as we do, AND THEN transport all of it, every atom, light

years, which will cost unimaginable amounts of fuel and time and industry. AND THEN we

have to build the bloody thing, which will take hundreds and thousands of years AND THEN,

it has to be economically worth all the effort of designing, resource collecting, transport,

manufacture, engineering, construction and maintenance.

*breathe* Assuming ALL OF THAT, you can finally stand

back on whats left of the planet youve gutted, along with many others, and watch

as thousands of years and an entire species work collapses and destroys itself in the

star because there is no physical material anywhere near strong enough to support that

kind of a structure. OH WELL, BACK TO THE DRAWING BOARD. UUUHHH.

*pause* This is why Freeman Dyson in 2013 stated he

wished it hadnt been named after him, probably because most peoples interpretations were,

quotephysically impossible’. But... ...there is another way. Remember those

variants from earlier...? Unlike a complete shell, these work by having

an orbiting network of structures, like a ring or a disc or a belt composed of smaller

energy gathering satellites. This is the more realistic of the two, still very hypothetical

concepts. After all, this design has the ability to be added to incrementally and we are starting

energy right there... right? Well, we could try to build more rings there,

but we have an underlying problem. This area, where the orbits cross, is incredibly dangerous.

Incredibly incredibly dangerous. Ill explain. A lot of people have this misconception about

orbits, perhaps led by simplistic diagrams like the one onscreen. With the way gravity

works, everything is attracted to everything else. There is no outer limit on the pull

of gravity. This means a star 500 million light years away is pulling on you, just by

a tiny amount. On a bigger scale, the Moon and Sun pull on satellites in orbit, drifting

them out of sync with each other. You still have tiny tiny molecules of gas up that high,

which drag against the spacecraft and slow it down towards Earth, hell, this is why the

ISS needs to reboost so often. Orbits naturally change, and to calculate

how this would happen would be physically impossible. Sure, you can allow for the massive

pull of planets, but as soon as the first spec of debris gets anywhere near them, they

will desynchronise. And if they desynchronise, they might hit each other. And the millions

of shards of debris will hit more satellites, which will hit more until you have a Kessler

Syndrome shell of shrapnel travelling many kilometres a second obliterating everything

near that orbit, and rendering that altitude physically unusable for centuries.

According to this video, a destruction on that scale would actually cause a recession,

the biggest economic recession in the universe. Oh yeah, and your civilisation has no electricity.

No power. Its basically an apocalypse. So thats fun.

*Sigh * However impossible Ive made it sound, scientists around the world are working

right now to make it a reality. We as a species have done the impossible before, so why let

it phase us? I mean, if another civilisation had a couple million year head start, I have

no doubt they would be trying to put in place some sort of stellar structure...right..now.

Wait...what? Holy shit.

HOLY SH*T. HOLY SH*T.

Yes, because in 2015 star KIC 8462852 was found by the Kepler Space Observatory to have

strange light fluctuations, as far as we know, unique light fluctuations. Fluctuations that

would indicate some sort of swarm of spread out orbiting matter. A swarm that weve

never seen before. It is wholly possible that this is our first

glimpse of intelligent extra-terrestrial life, or at least of their shadows from 1,480 years

ago. They may be constructing a Dyson Swarm, one of the more reasonable constructions when

trying to power a civilization. But ultimately, we will never know for sure. But its pretty

cool, right..? So thats the Dyson Sphere. Its uses,

origin, practicality, configurations and maybe even realisation. I hope you enjoyed this

video. Thanks for watching.

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