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00:00 Humankind likes to think it's pretty darn good.
00:03 Over just a few hundred thousand years - a blink of the eye on the timeline of the universe
00:08 - we've evolved into some pretty reasonably intelligent creatures.
00:12 We've populated a planet, spread across the world, and in recent times we've industrially
00:18 and technologically advanced at a seemingly staggering pace.
00:22 But actually, on the whole, has Earth seen it all before?
00:26 This is Unveiled, and today we're answering the extraordinary question; was a K2 civilization
00:31 on Earth before us?
00:34 Do you need the big questions answered?
00:36 Are you constantly curious?
00:37 Then why not subscribe to Unveiled for more clips like this one?
00:40 And ring the bell for more thought-provoking content!
00:44 The Silurian Hypothesis has fast become a favourite alternate worldview among a wide
00:48 range of people from staunch academics to sci-fi enthusiasts.
00:51 It's a thought experiment, jointly devised in 2017 and published in 2018 by the University
00:57 of Rochester astrophysicist Adam Frank and the director of NASA's Goddard Institute
01:02 for Space Studies, Gavin Schmidt.
01:04 The Silurian tag is a nod to a particular, Earth-dwelling, ancient alien race on the
01:08 BBC sci-fi series Doctor Who.
01:11 But really, this isn't a novelty idea.
01:13 Forget sonic screwdrivers and Dalek warlords, the Silurian Hypothesis is very much grounded
01:19 in the real world.
01:20 At its heart, it seeks to answer a simple question; how do we know there's never been
01:24 another civilization on Earth?
01:25 The argument being that since fossilization is uncommon, and since most of the surface
01:30 of the Earth is less than two and a half million years old, it should theoretically be extremely
01:34 difficult to find any direct artifact from a pre-human group if one did exist.
01:39 Evidence of plastic and nuclear waste might to some degree survive, but even they might
01:44 have been and gone on a planet that's 4.5 billion years old.
01:48 Similarly, researchers can study ice cores to analyze trace evidence of ancient epochs…
01:53 but it's never as though we'll find anything that's incontestable.
01:56 We've taken a deeper dive at the Silurian Hypothesis specifically in a past video, so
02:01 be sure to check that out next.
02:03 But no matter how we might go about detecting what may have come before, if we were to imagine
02:08 that there was something pre-human, then what would that something be like?
02:12 Clearly, one defining characteristic would be that whatever it was, it's no longer
02:16 here - which means it either went extinct, or it went elsewhere.
02:20 To a certain extent, an extinction event should be traceable through studying Earth's strata
02:24 - the thin layers of compacted material that make up the crust of our world.
02:29 But again, retrospective dating in this way is limited once we reach hundreds of millions
02:34 and multi-billions of years back in time.
02:36 Nevertheless, it would perhaps be even more difficult to catch another advanced group
02:41 if it had relocated, rather than died out.
02:43 A K2 civilization - Type 2 on the Kardashev Scale - could be viewed as both not too far
02:49 away from our own, or hugely far away from our own.
02:52 At K2, the group has harnessed the energy potential of its star system.
02:56 It's capable of building cosmic megastructures, and of colonising other star systems as it
03:01 looks to spread across the universe.
03:03 It has long cracked the puzzle of long-distance space travel, and is comfortably set up on
03:08 a number of planets and moons.
03:10 For many, this is, and should be, the direction that humankind itself is heading in… even
03:15 if we are at the very early stages.
03:17 We've been to our moon, we're aiming to go to Mars, we've sent orbiters and rovers
03:22 to the majority of other celestial bodies in the solar system.
03:25 A K2 is much more advanced, then, but it does at least exist along our same trajectory.
03:30 So, if a K2 ever had been on Earth, then what would it have achieved in its time here?
03:35 Perhaps the key thing in terms of covering its tracks is that a K2 should be fully energy
03:40 efficient.
03:41 Whereas the fossil fuels that we use in our lowly state linger for eons, the power that's
03:46 fuelling a K2 should be cleaner, carbon neutral at least, and less disruptive.
03:51 A K2 should have figured out, for example, a better alternative to plastic, one that
03:55 isn't almost indestructible, and a material that doesn't leach into the environment
03:59 in microscopic form.
04:01 In speculative fiction, writers often use the catch-all term "exotic materials"
04:06 to describe anything that's required for some kind of far-future, seemingly impossible
04:11 technology.
04:12 For a K2, however, those exotic options are mundane.
04:16 And naturally, they're impossible for us to imagine.
04:18 If we knew about them, we'd surely be using them by now, and we would exist further up
04:23 the Kardashev Scale than we do.
04:25 Today, humankind seems to be on the brink of perhaps the biggest energy breakthrough
04:29 since the Industrial Revolution.
04:31 For decades, we've had nuclear fission energy - the splitting of the atom that powers, for
04:35 instance, nuclear bombs.
04:37 But what we really need is nuclear fusion energy, which involves combining atoms to
04:41 again create power.
04:43 It's the same process as what happens inside a star, including our own sun, where hydrogen
04:48 atoms are fused into helium.
04:50 If, however, we could take the power of a star and bring it down to Earth, we should
04:55 then have energy that's limitless and clean.
04:58 The problem for us at the moment is that, while we've long experimented with fusion
05:02 reactors, none have yet managed to produce net power.
05:06 They all require more energy to run than what they create.
05:10 At K2, though, that's another problem that should have been solved.
05:14 And then, given that fusion energy will reportedly produce far less long-lived nuclear waste,
05:20 it should again mean that it would be difficult to trace any civilization that was using it.
05:24 It's another reason why a K2 group in particular could potentially move through space without
05:30 anyone knowing about it.
05:32 There are some elements of K2 that perhaps would hang around, however, and none more
05:36 so than its signature technology, the Dyson Sphere.
05:39 This is a massive frame that gets built around a star in order to siphon away from that star
05:45 every last unit of energy that it makes.
05:48 Given the immense local temperatures, it's thought most likely that it would be built
05:51 and manned by a community of self-replicating machines.
05:55 At such a close proximity to a star, this just isn't an environment that organic lifeforms
06:00 would want to be in.
06:01 So, is there any evidence that our own sun has ever hosted a Dyson Sphere?
06:06 In short, no, there isn't.
06:08 We can easily see it, so there clearly isn't one around it right now.
06:12 Our view is in no way obstructed, so we know there aren't any remnants of a past structure
06:16 still floating around.
06:18 A speculative science fiction storyline might involve the deliberate destruction of a Dyson
06:23 Sphere as a K2 moves on, perhaps by those same self-replicating robots collapsing and
06:28 driving it into the sun itself… but ultimately, that really is just a storyline.
06:34 There has never been any indication that anything like that has actually happened.
06:38 While then, the Silurian Hypothesis arguably shows that a past civilization could be effectively
06:43 invisible to us in the here and now, perhaps such a civilization actually will have never
06:48 made it to Kardashev Type Two.
06:50 Or at least, they will have never properly developed this solar system to match what
06:54 we would expect of a group at that level.
06:56 Another hypothetical possibility is that, while a past civilization never emerged here,
07:01 one did once settle here.
07:03 That way, it would be more like they were paying this system a visit, rather than ever
07:07 calling it home.
07:08 A group such as that would at once be more difficult to detect once again.
07:12 Importantly, the Silurian Hypothesis is a thought experiment only.
07:17 It was put forward by Adam Frank and Gavin Schmidt much more as a general inquiry, rather
07:21 than a genuine suggestion for what might have been on Earth before.
07:25 In this video, we've combined the notion with the prospects for a K2 civilization specifically…
07:30 and in some ways it works, and in other ways it doesn't.
07:33 What's your view on whether an ancient Type Two on Earth is possible?
07:38 Let us know in the comments!
07:40 Perhaps in reality, humankind isn't that special after all.
07:43 Perhaps our planet, our moon, our star, and our solar neighbourhood could all have been
07:48 viewed through the eyes of something else at some point in history.
07:51 Ultimately, there is no evidence to directly suggest that, but the Silurian Hypothesis
07:56 has, in recent times, asked us all to seriously consider our place in the cosmos.
08:02 What do you think?
08:03 Is there anything we missed?
08:04 Let us know in the comments, check out these other clips from Unveiled, and make sure you
08:08 subscribe and ring the bell for our latest content.