What If We Could Build an Alderson Disk?

WHAT IF

What would happend if could build this massif construction?

Transcript

00:00 This is not some DVD floating in space.

00:05 It's a megastructure

00:07 that might one day become humanity's home.

00:11 The Earth might not remain habitable forever.

00:16 It could get engulfed by a massive solar flare,

00:20 or become too hot due to climate change,

00:23 or have all its life wiped out

00:26 by one enormous asteroid.

00:29 What if I told you we could outlive all these disasters?

00:34 And that we could do that

00:36 by building a space megastructure

00:38 bigger than the Sun itself?

00:41 Just how big would we have to make it?

00:45 And what would life be like on a structure like that?

00:51 This is WHAT IF,

00:53 and here's what would happen

00:55 if we could build an Alderson disk.

01:00 Why would we colonize other,

01:01 currently uninhabitable planets,

01:04 if we could hypothetically build a habitat of our own?

01:08 Something that would host many billions of future humans

01:13 without ever running out of space.

01:16 It does look like a DVD, doesn't it?

01:19 Only it has the mass of 3,000 Suns.

01:24 The reason why we'd need our Alderson disk

01:27 to have such a huge mass is gravity.

01:31 All objects with mass

01:33 are gravitationally drawn to each other.

01:36 And objects with a greater mass

01:39 have a greater gravitational pull.

01:42 For the Alderson disk to be stable enough to host life,

01:46 we'd need it to have a stronger pull than the Sun does.

01:51 That's where it gets tricky.

01:53 Because the Sun is the most massive object in our Solar System,

01:58 accounting for 99.8% of its total mass.

02:02 To have enough material to outweigh the Sun,

02:05 we'd have to get it by breaking down every planet,

02:09 Moon and asteroid in a radius of hundreds of light-years around us.

02:15 Or we could give our Alderson disk artificial gravity.

02:20 This type of gravity isn't caused by attraction,

02:23 but by acceleration or centrifugal force.

02:27 In other words, we'd have to spin our disk

02:30 fast enough that it doesn't collapse into a donut,

02:33 or get swallowed by the Sun.

02:36 But since we haven't really figured out artificial gravity yet,

02:40 let's stick with the first option

02:42 and make our Alderson disk very, very massive.

02:46 241 million km (1.2 billion mi) wide.

02:51 That would make it stretch past the orbit of Mars.

02:55 It would also be several thousand km (1,000 mi) thick,

03:00 and would have a surface area equivalent to over one billion Earths.

03:06 Just imagine how many billions of humans could live on it.

03:12 But not so fast.

03:14 Our Alderson disk wouldn't be habitable everywhere.

03:19 And before I explain that,

03:21 let me talk about the Sun for a moment.

03:24 Our Sun would be sitting stationary in the hole at the center of the disk.

03:29 And because of this,

03:31 our disk would have no day and night cycle,

03:35 only a never-ending twilight.

03:38 But since our disk would have a bigger mass

03:42 and a stronger gravitational pull,

03:45 there's a chance that the Sun would wobble up and down.

03:49 That would somewhat solve our day and night problem,

03:51 but it could also increase the possibility of colliding with our star.

03:59 We might need to install gamma-ray lasers

04:01 to have more control over the Sun's wobbling.

04:04 And still, our disk-shaped world would need way more things

04:08 to become suitable for us to live on it.

04:12 One of the most important things is an atmosphere.

04:16 On Earth, the atmosphere protects us from harmful ultraviolet radiation.

04:21 It reduces temperature extremes,

04:24 and it creates pressure that allows liquid water to exist.

04:29 We'd need an atmosphere to do all the same things for our Alderson disk.

04:34 And to keep the Sun from stealing it,

04:37 we'd need to build a wall around the disk's inner edge.

04:42 Unlike Earth, the Alderson disk wouldn't have liquid metal in its core

04:46 to give it a magnetosphere.

04:49 A magnetic field is important because

04:51 it keeps the solar wind from stripping off the atmosphere.

04:55 Without it, the solar wind would erode the part of the Alderson disk closer to the Sun.

05:02 This could make the entire structure unstable,

05:05 and possibly destroy it altogether.

05:09 Once we figure out how to make the atmosphere and magnetic field,

05:13 we could bring in water.

05:15 We'd make holes in the disk that would allow for oceans.

05:20 Because of the way gravity would work on our Alderson disk,

05:24 the water could be suspended.

05:27 The oceans on the disk-shaped structure would literally be bottomless.

05:33 For the same gravitational reasons,

05:36 humans would be able to live on both the top and the bottom side of the disk.

05:41 For those living on the bottom side,

05:43 it wouldn't feel as if they were walking upside down.

05:47 It would be just normal on each side.

05:50 But of course, this space megastructure could have some flaws.

05:55 Because of the disk's enormous mass,

05:58 its gravity might make it collapse into a gigantic torus,

06:02 or even worse, a black hole.

06:06 Then there are asteroids.

06:09 Even though we used up all the nearby asteroids

06:12 to form our Alderson disk in the first place,

06:15 there's no guarantee new interstellar space rocks

06:19 wouldn't come and bombard our disk world.

06:21 And not just asteroids, but rogue planets as well.

06:27 Even the slightest hit could destabilize the disk

06:30 and plunge it right into the Sun.

06:34 Speaking of the Sun, remember I said that

06:36 not all of the Alderson disk would be habitable?

06:40 That's because the Sun wouldn't be heating it evenly.

06:44 The inner side of the disk would be very hot.

06:48 To withstand the tremendous heat,

06:50 we'd have to give our disk a heat shield,

06:53 just like the one we developed for the Parker Solar Probe.

06:58 The outer edges of the disk would be freezing cold.

07:02 But the middle band of the structure

07:04 would be just perfect for life.

07:06 Although there would be a lot of unused space,

07:10 the habitable area would still be 50 million times larger

07:14 than the entire surface of Earth.

07:18 So a giant platter with the thickness

07:21 of several thousand kilometers,

07:24 it might not survive in space.

07:27 Luckily, I have another idea in mind.

07:32 But that's a story for another WHAT IF.

07:36 [music]

07:41 [BLANK_AUDIO]

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