The Podcast of the Lotus Eaters

00:00:00.160 Hello and welcome to Brokernomics. Now, a little while ago I did an episode called Industrialising Space,

00:00:06.340 where I got a clever chap, Grant Donahue, to come on and we talked about everything from industrialising low Earth orbit

00:00:12.920 and then we kind of basically went up from there to, you know, the local couple of planets and then the rest of the solar system

00:00:18.900 and then the galaxy and then the local cluster. And we got a little bit ambitious with that one

00:00:25.440 and I just thought that would be an interesting side topic, but it turned out to be one of the most popular episodes we've ever done.

00:00:31.240 Lots of people absolutely loved it. Really high viewer count. People I've met in person have told me it's one of their favourite episodes.

00:00:37.580 So I thought, well, we can hardly let that lie, can we? So we got Grant back. Grant, thank you for coming.

00:00:43.860 Hello.

00:00:44.240 Well, that's very encouraging.

00:00:45.840 Yes, no, it went very well. So, you know, whatever it is we did last time obviously works.

00:00:51.920 So, well done and welcome back. Glad to have you back.

00:00:56.480 Now, the only thing last time is we were potentially a teeny tiny bit hubristic

00:01:03.760 in that we kind of suggested that we could colonise, you know, the local cluster of galaxies

00:01:11.320 on the assumption that we were the only ones doing it.

00:01:14.820 We kind of had uninterrupted access.

00:01:16.800 And actually, that might not be true. There might be other competing civilisations out there

00:01:23.460 and we're going to be going up against them.

00:01:25.380 So I thought maybe we might want to cover that a bit.

00:01:29.360 So, yeah.

00:01:31.080 So to build on what you said, it's pretty fair to say that we did have a bit of hubris.

00:01:37.140 I mean, I think it's well justified, but we put forward really the two main

00:01:41.380 current, currently discussed solutions to the Drake equation, which is the dark forest

00:01:46.660 and the firstborn, right?

00:01:48.140 Yes.

00:01:48.440 And we tended, at least I tended to favour the firstborn, but that doesn't, we can conjecture

00:01:54.940 about lots of things, but it's worth having the alternative ideas on the plate.

00:01:59.800 And so, yeah, no, it's absolutely worth discussing, you know, in greater detail, what are some

00:02:04.660 other solutions to the Fermi paradox?

00:02:06.380 What are some other ways you can work out the Drake equation to calculate the number

00:02:11.620 of civilisations you'd expect in the local group and what the implications of that are?

00:02:16.580 Yes.

00:02:17.060 Well, the Drake equation seems like a sensible place to stop.

00:02:19.800 And I know there are.

00:02:21.080 So actually, let's define that.

00:02:23.300 So the Drake equation, and I found a nice graphic on the NASA website, so I'll see if I can get

00:02:28.440 my editor to stick that up on the screen.

00:02:30.320 But basically, there is a calculation that you can use to work out roughly how many civilisations

00:02:39.440 you can expect to find in your galaxy.

00:02:41.960 Now, there are competing equations that some people might argue are possibly better.

00:02:46.900 But, you know, since the terms in them are unknown, you're kind of basically going to

00:02:53.000 have errors with whichever one you use.

00:02:55.760 And this is the most famous one, and therefore we might as well use it.

00:02:58.660 So I thought, maybe why don't we start with this?

00:03:02.260 We go through it and we explain why it is quite odd that we're not picking up alien civilisations.

00:03:09.560 Before I launch into my explanation on the Drake equation, anything you wanted to say

00:03:13.820 on the Drake equation itself?

00:03:15.620 Any thoughts on it?

00:03:16.980 Well, just specifically regarding the Drake equation, it's worth remembering that, as you

00:03:20.700 said, there are error bars on every number there.

00:03:22.780 And we don't even we don't agree on which terms are relevant, because when the Drake

00:03:29.020 equation was first proposed, we had a much different theory of both the way our own plan

00:03:32.780 worked.

00:03:33.080 I mean, it's worth remembering when the Drake equation was first proposed, we hadn't

00:03:35.540 discovered plate tectonics yet.

00:03:36.840 And so there's there's not a universal agreement on on what terms should be included or on the

00:03:44.660 error bars on those terms.

00:03:45.700 But it's a good place to start, at least.

00:03:49.320 Well, some of the terms we actually know quite well, but unfortunately, the key terms are the

00:03:54.620 ones that we we know the least well.

00:03:56.940 But we can make educated assumptions on all of them.

00:03:59.080 And actually, I'll just skip ahead to, you know, why this why this is relevant, why this 0.98

00:04:04.560 feeds onto a conversation about where all the damn aliens are, because when you take 0.95

00:04:08.560 a sort of sensible set of numbers and plug them into that equation, you get an end of 0.98

00:04:16.640 50,000, which is, you know, there should be about 50,000 intelligent, technologically

00:04:21.560 advanced civilizations in the galaxy at the moment, which might sound like a lot.

00:04:26.360 But when you remember, there are many hundreds of billions of stars in our galaxy.

00:04:30.880 Actually, that's only a very, very small proportion of stars having intelligent life.

00:04:35.360 But nevertheless, there should be thousands of them.

00:04:37.360 And we can't see the buggers.

00:04:39.760 And in fact, let me let me skip ahead now to, you know, before we before we get breaking

00:04:45.260 down into the terms.

00:04:46.540 First of all, rate my logic on this, because this this this is my thinking as to why this

00:04:50.420 is so difficult, right?

00:04:51.200 Now, let's assume that we've got to the end of our Drake equation, we will go through

00:04:57.020 that in a minute.

00:04:57.940 And we've got these advanced civilizations, and they're technological civilizations, we

00:05:03.420 can reasonably assume that advanced civilizations need energy, probably quite a bit of energy.

00:05:12.240 Okay, where are they going to get that energy from?

00:05:14.380 Well, they're probably not going to be burning wood and coal or whatever the local equivalents

00:05:18.780 that are forever, they're probably going to go with whatever the best form of energy

00:05:23.560 production there is at the moment.

00:05:25.160 The best form of any energy production that we are aware of at the moment is nuclear fusion.

00:05:32.600 We can loosely guess at more advanced technologies, but it is it is kind of science fiction, anything

00:05:41.600 beyond nuclear fusion at the moment.

00:05:43.420 So nuclear fusion, we know, okay, let's say we get to nuclear fusion sometime soon.

00:05:47.980 Fine, we're going to use that.

00:05:50.040 And that's all very well.

00:05:52.280 But even if we crack it, even if we can build local nuclear fusion power plants, there is

00:05:59.420 actually already a nuclear fusion generator in our solar system at the moment.

00:06:03.600 And it's a million times larger than the Earth, it's the sun.

00:06:07.520 And it's free.

00:06:09.120 And it just spits out energy.

00:06:10.660 So even if we did discover the tech, even if we mastered it, it's still not going to be

00:06:17.860 free and it still has a setup cost.

00:06:19.960 So you can imagine for a long time, at least, we are going to be wanting to just simply collect

00:06:24.880 the energy coming off our star.

00:06:27.200 Absolutely.

00:06:27.580 So that implies that you build something called a Dyson sphere, which is effectively lots of

00:06:33.580 satellites orbiting around the sun, collecting the energy.

00:06:36.920 Now, these satellites could look something like a few millimeters thick solar panel.

00:06:44.560 So very thin, but they could be vast.

00:06:46.740 Each one of them could be the size of Texas.

00:06:49.060 Sure.

00:06:50.160 Collecting that energy, throwing it back to Earth.

00:06:52.500 So we would expect to see these huge sort of spheres start to develop around the sun.

00:07:00.180 And the interesting thing about these spheres is that while they collect the visible light

00:07:05.260 and send that back to the civilization to use in whatever form that it wants,

00:07:11.820 the laws of thermodynamics dictate that there is going to have to be waste energy.

00:07:16.680 And therefore, there's going to be a mismatch between the infrared signature from the sun

00:07:20.660 and the visible light coming from the sun.

00:07:26.800 So you should be able to see a difference between the visible light and the infrared light coming

00:07:29.880 from that sun, unless the laws of thermodynamics are wrong.

00:07:34.020 Why don't you jump in there just to say if you've followed everything so far?

00:07:37.800 I have.

00:07:38.800 I think that the biggest telltale flag wouldn't necessarily be the mismatch,

00:07:42.640 but the apparent decrease in luminosity without a corresponding decrease in mass.

00:07:47.660 Yes.

00:07:48.060 And so, for example, given the mass of a star and its metallocity,

00:07:53.400 we can predict with pretty strong, with pretty reasonable certainty,

00:07:58.140 what correlations should lie there, right?

00:08:01.500 Like what the spectrum of light itch produces should be.

00:08:04.840 Because the laws of the universe appear to be such that an atom of, say, carbon-14

00:08:12.400 is indistinguishable from another atom of carbon-14.

00:08:15.280 There isn't any unique signature there.

00:08:18.200 And the emission of light, be it ultraviolet or infrared or visible,

00:08:25.140 is determined by the excitation of electrons up into higher energy states and then dropping down.

00:08:31.480 And as they drop down, they emit photons with certain levels of energy.

00:08:36.000 And because those are discrete steps rather than a ramp, there is emission spectra.

00:08:41.600 And so we can study that emission spectra.

00:08:43.840 So it's not necessarily that there's a mismatch between infrared or all this.

00:08:49.700 It's that for a given mass of a star, it should be achieving, at a given metallocity,

00:08:54.500 it should be achieving a certain level of output.

00:08:57.460 And if we can observe that output falling, for example, let's say we build a Dyson Swarm

00:09:01.040 and we capture 1% of the light of the sun, that doesn't seem like a lot.

00:09:04.360 But even at a very great distance, that's extremely noticeable.

00:09:08.040 We should be, if civilizations are doing this, noticing the luminosity decreasing on stars,

00:09:13.280 especially stars that are good candidates for hosting life.

00:09:15.740 And despite the fact that we've surveyed an absolutely enormous number of stars, we haven't.

00:09:19.040 Yes, that is a much smarter way of saying the things that I was saying.

00:09:26.080 But yes, absolutely, that is correct.

00:09:28.260 But OK, so I'll carry on with my logic.

00:09:31.100 So the logic then goes, OK, so we should be building these Dyson Swarms.

00:09:37.280 And we, as a species, currently know how to do it, as in we know the theory.

00:09:42.800 We don't have the engineering chops yet, and we're probably going to be away off that.

00:09:46.940 But the theoretical know-how, we already basically have it.

00:09:50.680 You build solar panels, you set them up, you do an orbit around the star.

00:09:54.800 Yes, there's a lot of complex engineering, but basically we understand the principles of all of this,

00:09:59.940 even if we can't pull off the engineering yet.

00:10:02.580 But it is reasonable to assume that at some point in the next couple of hundred years,

00:10:06.480 we will start building out this sphere.

00:10:08.080 And the only reason that we wouldn't do that is if sometime between now and then,

00:10:16.940 we discover something which is significantly better than fusion.

00:10:20.720 And it needs to be significantly better than fusion, probably an order of magnitude better than fusion,

00:10:25.860 for the reason that I've already explained, that the fusion output of the star is already there and it's free.

00:10:34.140 So you're going to need something significantly better in order to give up on free and abundant.

00:10:40.460 Again, does that logical step make sense?

00:10:44.040 Yes, largely.

00:10:44.800 If your civilization is still existent, you tend to...

00:10:47.700 A good example of this is, just because we've discovered nuclear actors doesn't mean we've undammed all the rivers. 0.52

00:10:52.760 It doesn't mean we've stopped burning coal.

00:10:55.060 It's very rare to hit upon a resource that you simply stop exploiting, unless you entirely eclipse it.

00:11:00.940 And so you make a good point with regards to an order of magnitude better,

00:11:05.200 because if we found something that was 10% better than fusion, that still wouldn't justify it,

00:11:09.520 because it's there, it's free.

00:11:11.040 It is a readily available source of energy, just as rivers are, just as coal seams are.

00:11:16.380 And so unless there's an enormous disadvantage, and I can think of one or two, for example,

00:11:20.680 in the Dark Force Hypothesis, there really isn't much reason not to begin a Dyson Swan.

00:11:25.060 Yes, I mean, the only thing that I can think of as a historical parallel there is that we gave up rather abruptly whale oil.

00:11:32.520 Sure.

00:11:33.220 Because we found something that was significantly better.

00:11:35.280 We found petroleum that we could dig out of the earth.

00:11:37.840 But that's the only thing that springs to mind is something that we rather abruptly ended at a given point.

00:11:41.940 Okay, so given that we should be building Dyson Swarms within the next couple of hundred years,

00:11:48.040 the fact that we're not seeing, and when we look up into the heavens,

00:11:52.320 we're not seeing evidence of these Dyson Swarms appearing from some of these proposed 50,000 civilizations 0.97

00:11:59.440 that are out there in just our galaxy.

00:12:01.340 You have to believe that every single one of them went from the current level of technological advantage

00:12:08.200 that we are at, and in between that and the point of being able to pull off the engineering,

00:12:14.180 every single one of them discovered something that was an order of magnitude better,

00:12:18.900 and therefore they skipped the Dyson Swarm stage.

00:12:22.200 And that doesn't make any sense.

00:12:24.660 And the paradox that we're looking to address is, well, where the hell are they then?

00:12:29.300 Well, they should be there.

00:12:30.940 And it's worse than our galaxy, because in the research for this, I found that there was a project.

00:12:35.780 What was it?

00:12:36.140 It was the Wide Field Infrared Survey Explorer, WISE.

00:12:42.100 Jason Wright and team at Penn State, they actually looked at 100,000 galaxies

00:12:48.220 looking for evidence of galaxy-wide Dyson Swarm building.

00:12:53.120 So 100,000 galaxies they looked at, and each one of those could have hundreds of billions of stars.

00:13:00.020 And they found no evidence of this.

00:13:02.620 Yes.

00:13:02.980 And their work was confirmed by the fact that standard candles were giving off exactly what we expected.

00:13:07.660 So there are a certain kind of stellar phenomenon, which no matter where they happen,

00:13:12.600 produce an extremely predictable quantity of light, not just on the order of stars,

00:13:16.700 but certain kinds of supernovae, because their limits are defined by gravitational forces.

00:13:22.440 So, for example, one of the most famous standard candles is you have a binary star,

00:13:26.860 because most stars actually aren't singular stars, they're binary stars.

00:13:29.660 You have a white dwarf, a star that died earlier, and a more massive star, which has expanded,

00:13:35.160 entering its death phase.

00:13:36.040 And as a result, if they are close enough, the white dwarf will begin to draw gas off.

00:13:41.760 The white dwarf has carbon and neon and oxygen, but it never was mass enough to fuse those.

00:13:50.360 So you can think of it as it has a lot of hot fuel, which never achieved its ignition point.

00:13:54.880 It got through all of the...

00:13:55.200 Hang on.

00:13:55.900 So a white dwarf is a star, which is...

00:13:59.060 No, it's...

00:14:00.040 So hang on.

00:14:00.420 Is it a star, or is it just a big Jupiter?

00:14:02.300 So when you have a low mass star, one thing to know about fusion is that the threshold to achieve fusion

00:14:11.760 is different for every kind of fusion you're trying to perform.

00:14:15.900 And so you can...

00:14:17.800 Or rather, for self-sustained fusion.

00:14:19.080 So, for example, fusing hydrogen and hydrogen into helium requires a lot less pressure and a lot less energy

00:14:25.160 than fusing helium and hydrogen together to make beryllium.

00:14:29.360 And actually, that's not stable.

00:14:30.260 It decays almost immediately, but there are different processes.

00:14:34.920 And so when a star is low mass, it may never achieve the threshold to go from burning hydrogen

00:14:40.180 from burning helium into the heavier elements and burning those all the way up to iron.

00:14:45.280 And so as a result, you have a star that simply winds down.

00:14:48.680 It doesn't explode in a supernova.

00:14:49.940 It simply winds down, and you're left with a remnant with a tiny amount of nuclear fusion going on,

00:14:54.280 but that's mostly just kept alight by its own heat.

00:15:00.840 It's cast off some of its outer layers, and it is simply a stellar remnant.

00:15:05.640 I see.

00:15:05.960 So a white dwarf is a star which is less massive than our sun, which, okay, it can fuse hydrogen,

00:15:12.880 but when it starts to go beyond that, when it's run out of hydrogen, then it kind of basically runs out of steam and it goes into standby.

00:15:18.700 It becomes a white dwarf.

00:15:19.840 It becomes a white dwarf because it doesn't have the sufficient gravity to create the pressure it needs to perform fusion.

00:15:27.020 So why does that provide an extremely reliable candle?

00:15:30.200 Because the stellar, if it is in a pair with another star, it can begin to draw mass off of that star if the star expands.

00:15:38.520 So let's say it's with another star.

00:15:39.780 That star also goes into a red giant phase near the end of its life.

00:15:43.060 Its sphere expands.

00:15:45.640 If that star, if its outer layers pass the Roche limit of the white dwarf,

00:15:49.760 that is to say the white dwarf begins to exert pull and pull gas off of the other star,

00:15:53.900 it will slowly gain mass, and as a result, it will slowly gain pressure.

00:15:57.380 And because the energy and pressure needed to achieve fusion is the same everywhere in the universe,

00:16:07.460 it's the same reaction.

00:16:09.320 If it achieves a certain amount of gas, it will, at that point, and every time at that point,

00:16:14.080 immediately achieve a fusion reaction, restart itself, and explode.

00:16:19.460 Why does it explode?

00:16:21.060 Why doesn't it just start working up the luminosity?

00:16:26.420 Because what immediately happens is, as you start that fusion reaction,

00:16:30.000 you tip over a threshold whereby the star, before, it had a lot of hot...

00:16:34.420 Think of a barrel of hot gasoline, right?

00:16:36.960 And you're adding pressure, and you're adding temperature, you're adding pressure.

00:16:39.400 The moment you add enough temperature and pressure that it ignites,

00:16:42.700 does it just burn off a little bit, or does the entire barrel blow up?

00:16:46.160 It's because now you create a fusion event which releases a lot of energy,

00:16:50.500 because what you have to know is, as you go further down the fusion chain,

00:16:53.300 the reactions don't get less energetic.

00:16:54.640 They actually get more energetic.

00:16:56.800 They release more energy.

00:16:58.520 And so what immediately happens is, it has a fusion event,

00:17:01.260 which then massively increases the pressure in the star,

00:17:03.740 which then massively increases the amount of star that can actually cross that threshold all at once.

00:17:08.580 And you get a runaway cycle.

00:17:11.080 And so because the threshold is the same, that's what makes it a reliable candle?

00:17:15.520 Exactly, because it's when it has drawn off a certain amount of gas.

00:17:19.760 It doesn't matter...

00:17:20.420 How would you build a Dyson swarm around something so unstable?

00:17:23.340 You wouldn't.

00:17:24.260 But the more useful thing about that is,

00:17:26.820 is the standard candle tells us that there isn't anything strange going on with those signals that could be confusing us.

00:17:32.460 It's telling us that the metallosity in those galaxies is similar to us.

00:17:35.980 It's telling us that the stars are of similar composition.

00:17:38.480 So we're essentially saying we can't posit that perhaps the galaxies we're looking at are red shifted to the degree that we wouldn't recognize it,

00:17:46.820 because the standard candle is telling us, no, our light readings here are consistent,

00:17:50.060 or at least it's giving us a reading that we can use to provide an adjustment.

00:17:53.380 I see.

00:17:53.880 So they're telling us that everything about these 100,000 galaxies is normal.

00:17:58.840 Exactly.

00:17:59.340 Everything that we can tell is normal.

00:18:00.820 It is simply the fact that there is the absence of any advanced civilisation or Dyson swarms.

00:18:06.880 Exactly.

00:18:07.300 Yes.

00:18:08.200 So it lets us eliminate a huge number of possible alternative explanations.

00:18:13.760 And that means that we are left with a very small number of ones.

00:18:16.520 And one of the most harrowing ones is they simply aren't there.

00:18:21.660 The great silence is deafening.

00:18:23.640 So we go through the Drake equation in a moment, and we can pare down each of those terms within it to get down to basically one advanced civilisation per galaxy, as in...

00:18:37.080 Or a considerably smaller number.

00:18:38.940 Was that?

00:18:39.640 Or a considerably smaller number.

00:18:41.340 Yes, or a considerably smaller number.

00:18:43.020 We're just the one in, you know, many hundreds of local galaxies that is that one.

00:18:47.920 But you have to start really pushing the numbers in order to sort of get down that low.

00:18:53.880 But you certainly wouldn't expect it in 100,000.

00:18:56.520 I mean, that would be an absurd...

00:18:57.920 That is kind of straining credulity that you haven't got more than one intelligent civilisation in 100,000.

00:19:06.640 So something weird is evidently happening here.

00:19:10.020 Thus, I presume you would agree with me, but thus the Fermi paradox does appear to be a real paradox.

00:19:15.700 Oh, yeah.

00:19:16.940 There's no good explanation as to why it's that low.

00:19:20.860 I think there are good hypotheses.

00:19:24.780 Because one thing that the Drake equation doesn't do a great job of is accounting for time.

00:19:28.540 This is why the firstborn hypothesis came considerably later.

00:19:31.260 Because the Drake equation did not account for the amount of time it takes for a planet to develop to the point where life could exist on it.

00:19:38.520 And so you can eliminate a huge number of stars.

00:19:40.680 This is what I meant by...

00:19:42.060 It's not just the values on those terms, but there are additional terms.

00:19:44.680 And with an equation like the Drake equation, the interesting thing is that as you add more terms, the number falls very, very quickly.

00:19:52.620 A good example...

00:19:53.440 Yeah, because you're multiplying out and multiplying out.

00:19:55.760 Exactly.

00:19:56.240 And each one's a decimal.

00:19:57.160 And you add an extra multiplication and your ultimate...

00:19:59.580 And let's say it's a generous 10% on that second term.

00:20:02.380 You've already reduced it by a factor of 10.

00:20:04.880 Exactly.

00:20:05.560 And so that number can fall very quickly.

00:20:07.980 There are other factors.

00:20:09.140 You can eliminate a huge chunk of the stars by being too close.

00:20:12.540 I believe we discussed this last time.

00:20:13.700 By being too close to the galactic center.

00:20:16.780 You can eliminate stars based on metallocity.

00:20:18.880 The Drake equation...

00:20:20.140 Again, it's not to say anything against its author, but it's simply...

00:20:24.380 It was proposed long enough ago that when you start adding terms and you make certain assumptions,

00:20:28.220 you actually can get down to numbers where it's...

00:20:31.540 I'm not going to say certain, but it's not a completely mind-boggling possibility that you might not expect to get more than one civilization in the sort of radius where we could reliably detect them.

00:20:46.140 Oh, that's sad.

00:20:47.660 It's not...

00:20:48.100 Now, of course, that's...

00:20:49.680 Again, that's one extreme end of the terms.

00:20:51.780 Because I'm...

00:20:55.480 For example, one of those is you're assuming that the only viable kind of life is carbon-based life.

00:21:02.100 Now, that was an assumption he made where you could actually be more generous because you could say, well, there are actually more candidates.

00:21:08.180 There's silicon and there is silicon, sort of...

00:21:13.820 And there are some possibilities for perhaps sulfur.

00:21:16.820 And if you allow for those, then suddenly you can be a lot more...

00:21:21.140 There are a lot more candidates.

00:21:23.060 Well, just because you're expanding the habitable zone of the star.

00:21:25.720 Exactly.

00:21:26.440 Because if...

00:21:27.440 The reason why carbon-based life is so specific is because most reactions that we can tell that require carbon-based life need to take care...

00:21:34.820 Need to take place in a liquid medium.

00:21:36.440 And almost the only liquid medium suitable for those is water.

00:21:39.580 So there's a very specific temperature range.

00:21:41.400 But if you're suddenly...

00:21:44.240 If you're a life...

00:21:45.260 If you're a life form that can conduct reactions in liquid ammonia, that massively expands the habitable range of the star.

00:21:54.440 Because suddenly, you know, liquid ammonia takes a lot less heat to be liquid.

00:21:59.920 Yeah.

00:22:00.140 It's...

00:22:00.820 And so...

00:22:02.400 So I'm not trying to say that the...

00:22:06.840 What I'm putting forward is the only solution.

00:22:08.280 I'm simply saying the paradox is very much real.

00:22:12.900 But I think there is a credible explanation.

00:22:15.820 It is merely a hypothesis, but it is an explanation.

00:22:19.000 Okay.

00:22:19.140 So let's start going through the equation.

00:22:20.580 Sure.

00:22:20.820 Because it will...

00:22:21.480 It will elicit more conversation as we start to put out some of the terms.

00:22:25.720 So hopefully my editor is now showing the equation thing in front of us.

00:22:30.100 So we're looking for N, the number of technologically advanced civilizations in the galaxy. 0.99

00:22:34.240 Sure.

00:22:34.420 And the first term that we're looking for is R, the rate of formation of stars in the galaxy.

00:22:39.500 Now, that one, very basic.

00:22:41.060 I think we pretty much know that's between one and five.

00:22:45.380 Would you agree that's about right?

00:22:48.000 Something like that.

00:22:51.680 Stellar nurseries are pretty easy to monitor and star births are quite noticeable.

00:22:55.780 Okay.

00:22:56.860 So between one and five on that one, nice and simple.

00:23:00.440 Fraction of stars with planetary systems.

00:23:03.600 My understanding is that the thinking is at the moment that basically almost all of them have planetary systems.

00:23:09.020 Yes.

00:23:09.700 Now, the number of them that have stable planetary systems is a different matter.

00:23:12.920 But at least, as far as we can tell, the best way I can put this is every time we've gotten better at detecting planets, we've found a greater and greater proportions of exoplanets around stars.

00:23:24.260 So that's the sort of trend that leads to the point where you start thinking, well, are there any without them?

00:23:28.440 And we have a few that are pretty strong candidates.

00:23:31.520 Proxima Centauri has no detected planets.

00:23:33.740 And it's quite close.

00:23:34.720 But it seems like the vast majority do.

00:23:39.020 Okay.

00:23:40.160 What have we got next?

00:23:41.220 We've got the number of planets per solar system with an environment suitable for life.

00:23:45.340 So this is the point that you were just making, because this assumes it's going to be carbon-based life.

00:23:50.380 And therefore, it's going to be only basically planets within the orbit of something like Venus to Mars.

00:23:55.860 So there are, in our system, there are going to be three planets that qualify for N.

00:24:00.600 So if that's true, if our solar system is anything to go on, that's a reasonably high proportion.

00:24:06.500 But even if we plug in a lower number here, say 0.5, as I did for my equation when I ran this, 0.5 is a lot less than the three that we've got here.

00:24:15.040 So you'd have to assume that our system is rather bountiful when it comes to habitory planets.

00:24:21.340 Sure.

00:24:21.800 I will point out, though, that Venus probably isn't in the habitable zone.

00:24:26.820 But it's because, as far as we can tell, the main reason why Mars didn't succeed is not because of where it's placed.

00:24:36.260 It's simply not massive enough.

00:24:38.420 But Venus is of similar mass.

00:24:40.160 It had a lot of the same things going for Earth.

00:24:43.640 And the main thing that seems to have driven its runaway greenhouse effect was increasing stellar luminosity.

00:24:51.100 Because it's worth remembering, over the star's lifetime, that habitable zone may move.

00:24:54.460 So it's not enough to just be in it.

00:24:55.760 You actually have to be in a point where, even at the highest point of luminosity and the lowest point of luminosity, the star won't scorch or freeze the planet such to the point that it's irreversible.

00:25:04.060 Yes.

00:25:06.540 Okay.

00:25:07.480 You don't want to be an edge case on the edge of the planetary zone.

00:25:11.120 Okay.

00:25:13.420 Okay.

00:25:13.880 So with us, you could say, okay, there's two, possibly three planets that fall into that.

00:25:19.500 So, again, it's a reasonably high number.

00:25:21.560 And for the equation that I did, I just picked 0.5, which is somewhere, you know, four times less than what we would have.

00:25:27.560 Okay.

00:25:27.960 What have we got next?

00:25:28.540 We've got FE, the fraction of suitable planets on which life actually appears.

00:25:33.320 Now, this is where it starts to get a bit difficult because, as far as we know, there's only one.

00:25:37.800 So it's 100% on the sample case that we've got.

00:25:40.740 But then again, what's your thinking on this one?

00:25:45.460 Because life did seem to emerge almost immediately as soon as the planet calmed down.

00:25:51.360 Exactly.

00:25:51.720 Right in the Archean.

00:25:53.940 So there's a very good reason to think that life can emerge almost immediately on the point that conditions are suitable for it.

00:26:04.440 And so I don't have much contest there.

00:26:08.360 It seems to be that just getting to life itself isn't a particularly difficult chemical step.

00:26:13.060 My contention is that it's when you get to multicellular life because that took on the order of 2 billion years.

00:26:19.640 I don't think the Drake equation accounts for that.

00:26:22.840 So what is the thinking there?

00:26:24.160 So you're thinking of something like our planet is about 5 billion years old.

00:26:27.800 So within the first billion years, life forms within the first 400 million years for complex life to form.

00:26:36.400 Is that right?

00:26:37.720 We of the the way I always try to think about it is that if you look at the entire history of life on Earth, something like five sixths of it is just multi is just single cellular life without nuclei.

00:26:51.040 Yes, just goo.

00:26:52.300 Yeah.

00:26:52.440 And then there's the Cambrian explosion.

00:26:54.300 And then after that, it's not fair that the pre-Cambrian, the early the late pre-Cambrian does have some multicellular life.

00:27:00.320 But for the most part, for the vast majority of the Earth's history, despite the fact that the conditions were nominally there, multicellular life just didn't develop.

00:27:08.080 OK, so we had what viruses and bacteria and that's about it, was it?

00:27:11.280 We're actually not even sure viruses, but we can't tell how viruses evolved.

00:27:15.900 We were not entirely sure if they evolved from non-living material or if they're bacteria that lost their own metabolisms.

00:27:22.840 Or if they evolved multiple times.

00:27:28.380 OK.

00:27:29.700 Viruses are real.

00:27:30.860 And don't even get me started on archaea.

00:27:32.580 I cannot teach you about archaea.

00:27:34.040 No one knows anything about archaea.

00:27:35.660 They're an entire domain of life that no one understands.

00:27:38.340 I've never heard of them.

00:27:39.780 Very briefly, what are they?

00:27:40.880 Archaea is, so there are the categories of life, animalia, plants, fungi, and bacteria, and archaea.

00:27:54.200 And archaea are, this entire family, they're as varied as the category of animal or as of plants.

00:27:58.600 And they are universally singular cellular.

00:28:01.340 And as far as we can tell, none of them are ever pathogenic.

00:28:03.580 So despite the fact that they are as common as bacteria and as common as other forms of single cell life, and they're everywhere, we have never found a single one that is pathogenic, that causes disease.

00:28:14.580 It is so alien that it doesn't seem to interact with us at all.

00:28:16.960 So I'm going to bank that thought for when we come on to the Fermi Paradox later, because that gives me something there.

00:28:25.000 OK.

00:28:26.240 And actually, the other thing on the point of life emerging is, I don't know if you heard it, but there is this one guy, I wish I remembered his name, who basically put forward the notion that life is a natural consequence of the laws of thermodynamics.

00:28:40.000 Because when you've got energy bombarding a system, that energy has to go somewhere.

00:28:46.040 And I'm butchering his argument, but it's something like the path of least resistance is for that energy to be fed into basically creating life.

00:28:55.180 Because it's a way of dissipating the energy.

00:28:57.740 It's it's if you provide energy to a system or if you provide energy to a system, it will tend to arrange itself into ordered into an ordered into into an ordered state.

00:29:09.220 Crystals tend to grow in the presence of energy, that sort of thing.

00:29:12.460 And so life could be one means of expressing it.

00:29:15.360 Admittedly, that's a teleological argument in that it's an argument from consequences.

00:29:19.600 But but I think there is something to that.

00:29:22.880 But but it's not it, but it's but you don't fundamentally dispute that it's impossible, that life is more or less an extension of the laws of thermodynamics.

00:29:31.260 And therefore, we can assume that almost anywhere where you bombard a suitable planet with enough energy, life is going to emerge because it kind of has to because the energy needs to go somewhere.

00:29:42.820 I'm not sure I would say that I inherently agree with it, but I'm not going to say that I I'm good.

00:29:48.220 I can't dispute it, but I would need to because I can think of some counterexamples.

00:29:52.900 Admittedly, they're somewhat trivial counterexamples, but I can think of some reasons why I would disagree, because life, unlike certain other kinds of energy investments, is not arbitrarily investable.

00:30:03.600 You can't pour an arbitrary amount of energy into life into a system and get more and more life out of it.

00:30:08.140 Eventually, the amount of life actually starts to decrease because the system is too energetic for chemistry to take place.

00:30:12.480 And so the amount of energy being supplied is actually it's not an unconstrained value past a certain point.

00:30:21.680 But I think there is something to that, that if you're providing a suitable amount of energy for a long enough period of time to a chemically active system, you would expect very complex things to start emerging.

00:30:31.220 And life seems one of the very natural courses of it.

00:30:34.360 That's interesting. When you say one of the things, are you able to envisage something other than life, which is the product of increased complication?

00:30:47.600 Plate tectonics. Plate tectonics is a great example of that in that you have you've supplied you have an energy being you have energy.

00:30:54.260 You look at the simplest plate tectonics, a stagnant lid, where you just have the inner core.

00:30:59.100 You have an inner core, which is liquid. And then outside of that, you have a solid core, a mantle and a singular shell that like Mars.

00:31:06.140 But then as you have something more massive like the Earth, we have an inner core, which is solid, an outer core, which is liquid, a mantle, which is sort of an amorphous liquid or an amorphous solid.

00:31:18.960 And then you have a crust and those crustal plates are broken up into different pieces and they're moving across each other and exhibiting different failure methods and all that.

00:31:26.820 Plate tectonics, I think, is a really good example. And just the hydrosphere in general is a great example of how pouring energy into a system can produce an enormous amount of complexity.

00:31:36.260 And unlike life, it doesn't seem to be strongly constrained until you melt the lid.

00:31:39.600 And even then, you know, like almost all of our diamonds come from exactly that, where the mantle was hot enough to burn through the plate and create kimberlite pipes, which then form the diamonds.

00:31:50.420 But these things are not mutually exclusive, as we've done with here.

00:31:53.820 They can they can develop alongside each other because there was a lot of energy being poured into the system.

00:31:58.660 Indeed. And they can also drive each other. They can further enhance each other.

00:32:02.040 So, yeah.

00:32:04.500 OK, so fraction of planets where life emerges.

00:32:07.960 I mean, for my equation, I chose 50 percent.

00:32:11.080 Sure.

00:32:12.020 Which seems reasonable, but you could easily make an argument that it could be significantly higher than that.

00:32:17.180 Oh, actually, what do you make of the argument?

00:32:19.660 Because another theory is that.

00:32:24.420 Life did not. Life did not emerge on Earth.

00:32:27.080 It arrived here.

00:32:29.160 Panspermia.

00:32:29.600 Yes. What do you what do you think about that one?

00:32:33.840 I mean, I don't see what needs to be the case, but it's for me, it doesn't seem to solve anything because the life has to start somewhere in that, you know, you you it's a bit like and I'm a Catholic, but nothing annoys me more than bad arguments for God.

00:32:48.700 Because it's the only thing that annoys you more than bad arguments for the other side is bad arguments for your own side, which is you say, well, the universe needs a universe creator because it exists.

00:32:57.480 And then you say, well, then God exists.

00:32:59.020 Where's God's creator?

00:33:00.140 You just move the problem back a step.

00:33:02.360 I think it's perfectly possible.

00:33:03.600 Well, panspermia is is is is is is an option, but it still ultimately puts you at a point where, well, then where do the bloody life originate?

00:33:12.420 All that it serves to do is to call into question whether Earth is actually suitable for a candidate for life to arise or if it isn't.

00:33:18.540 And if you're only adding questions without actually adding any answers, it's not super useful tool of explanation.

00:33:24.620 I'm not saying it's impossible.

00:33:25.800 It's just as a hypothetical until we have reason to consider it.

00:33:29.560 I don't.

00:33:32.960 I don't put a lot of thought into it.

00:33:34.580 And I see your point.

00:33:35.560 And if if it is.

00:33:39.360 If it if it is landing on a planet where it's suitable, you kind of assume that it would emerge on that planet anyway, on the grounds that it is as we've established suitable.

00:33:47.580 Exactly.

00:33:48.540 Right.

00:33:48.780 OK, so I've gone for 50 percent, but still we argue it could be beyond.

00:33:53.600 OK, fraction where intelligent life emerges.

00:33:56.560 So this one.

00:33:58.180 So we've agreed that life emerging is actually fairly straightforward and simple.

00:34:03.400 And the Drake equation kind of skips your complex life term and goes straight into intelligent life.

00:34:10.980 So we're going to have to roll complex life and intelligent life into there.

00:34:14.260 Just addressing the point of of intelligent life emerging.

00:34:17.560 Again, on the planet that we've that we're on, you know, you can make an argument that has happened.

00:34:22.980 Once, but maybe three times on our planet, if you include whales and dolphins, I don't know whether that whether they would necessarily count as intelligent or possibly they also mean technologically using, you know, tool using or something like that.

00:34:37.940 But then dolphins do use tools to a limited extent.

00:34:42.040 So take us through this one.

00:34:45.200 Intelligent life emerging, but we might have to roll in your complex life factor into it as well. 0.54

00:34:49.500 So this is actually one of my favorite examples of how you can sort of decompose problems like this to make them more salient.

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00:35:04.340 Thank you.

PREVIEW： Brokenomics ｜ Where are all the Aliens？

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