How many alien civilizations are out there?

00:00:00.000 | This video is about optimistic, pessimistic, and my own estimates of how many intelligent alien civilizations might be out there.

00:00:07.800 | I center this video around the Drake equation that combines a bunch of parameters, multiplies them together,

00:00:14.000 | and estimates, based on that, the number of alien civilizations in our galaxy, the Milky Way galaxy, and the observable universe.

00:00:22.000 | In general, this video is probably less about the estimates themselves and more about the mysteries behind the very question.

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00:00:40.000 | Okay, the Drake equation combines seven parameters, I added an eighth one here.

00:00:45.000 | I'm not using the symbols in the equation because it's too easy for people to forget what each one stands for.

00:00:50.000 | The variables build on each other, hence the multiplication.

00:00:54.000 | Okay, they are the number of new stars born per year, the percent of those stars that have planets,

00:01:00.000 | the number of habitable planets per star, the chance of life developing on one of those planets,

00:01:07.000 | then the chance of intelligent life developing, and finally the chance of that intelligent civilization advancing far enough to develop the technology

00:01:16.000 | to be able to communicate, in our case, through electromagnetic signal.

00:01:21.000 | Seventh is the lifetime of that civilization while it's in the communicating stage of its development.

00:01:28.000 | And finally, the eighth parameter that wasn't in the original Drake equation is the average number of times that a civilization is born on a planet.

00:01:37.000 | That is, one time it's born and it becomes completely extinct and is reborn again.

00:01:43.000 | This parameter makes sense since the age of a planet can be billions of years.

00:01:47.000 | And then you multiply it all together to get the estimated answer to our question.

00:01:51.000 | I list today's estimates for the optimistic and the pessimistic based on the most recent publications that I'm aware of,

00:01:57.000 | and today's estimates for me based on how I'm actually feeling today.

00:02:02.000 | This estimate probably drastically changes from day to day or from hour to hour within the day,

00:02:07.000 | based on my optimism on several of the parameters I'll talk about.

00:02:10.000 | I should say that the optimistic and the pessimistic estimates don't reflect the best case and the worst case.

00:02:16.000 | They simply reflect a reasonable estimate for a high value for these parameters and a low value for these parameters.

00:02:22.000 | Okay, the number of new stars born per year.

00:02:24.000 | The pessimistic one is 1.5 and the optimistic is 3. I tend to side with the 3.

00:02:30.000 | The 1.5 to 3 stars per year is the latest estimate as of about five years ago from NASA.

00:02:36.000 | Most recent relevant paper that I'm aware of is in 2015.

00:02:40.000 | Either way, the variability on this parameter is not very large. Just wait until later.

00:02:45.000 | Okay, the percent of these stars with planets.

00:02:48.000 | This is a little bit tricky, but it seems to me as of 2012, just looking at some papers,

00:02:54.000 | almost everyone seems to believe that now pretty much all of these star systems have planets around them.

00:03:02.000 | Somebody's probably going to argue for the pessimistic one being decreased to like 90% or even the previous one of like 30 or even 20%.

00:03:11.000 | I don't think this affects it that much.

00:03:14.000 | The evidence seems to indicate that pretty much every star has a planet around it.

00:03:18.000 | I like big rocks and I like gravity, so I think this is pretty exciting.

00:03:23.000 | The number of habitable planets per star. This is where we start to get into some fun debate.

00:03:29.000 | Probably mainly centered around the word habitable. Like what does it mean for a planet to be habitable?

00:03:35.000 | The argument for the optimistic view is it's pretty simple to be in the habitable zone of a star.

00:03:42.000 | If it's all just about the range of distances from the star.

00:03:45.000 | The more interesting argument for me that I tend to hold is that in order for a planet to be habitable,

00:03:52.000 | meaning support life in the broad definition of what life is, the planet doesn't necessarily need to be Earth-like.

00:03:59.000 | There could be totally different kinds of planets that are able to support life that we're not even aware of.

00:04:05.000 | Those who argue for the low estimate, like the general set of ideas behind the rare Earth hypothesis

00:04:11.000 | that you should check out, places a lot more constraints on habitability like suitably low radiation,

00:04:17.000 | high star metallicity, which by the way, from an astronomer perspective, a metal is anything that's not hydrogen or helium.

00:04:24.000 | So carbon is a metal. There you go. Fun facts with Lex.

00:04:29.000 | Okay, continuing the list of constraints. Low enough density to avoid excessive asteroid bombardment.

00:04:34.000 | And there's much more. There's a long list. I don't know which one of these is most constraining to be honest,

00:04:40.000 | but it really centers around the question stated by the rare Earth hypothesis.

00:04:44.000 | Does a habitable planet really have to be Earth-like?

00:04:47.000 | And exactly how close to the precise conditions of Earth does it have to be?

00:04:52.000 | Next parameter is the probability of life developing on a habitable planet.

00:04:58.000 | This parameter to me is super exciting, especially because it is one of the biggest open questions within the reach of science.

00:05:05.000 | If we discover hard evidence of life on Mars, for example, even if it's extinct, or in Europa, the icy moon of Jupiter,

00:05:14.000 | and maybe more concrete evidence about life on Venus that was recently discovered in gaseous form of phosphine, I think, in the atmosphere.

00:05:25.000 | So if there's like some good concrete evidence of life on another planet,

00:05:29.000 | that shows to you that the probability of life developing is quite high.

00:05:35.000 | So the day-to-day variability in my estimate has to do with how optimistic I am about us discovering life on the planets or moons in our solar system.

00:05:46.000 | Going by recent papers, the optimistic is 13%, the pessimistic is 0.1%.

00:05:51.000 | I go somewhere in between those all the time, sometimes much closer to 13%.

00:05:56.000 | Today it's 1%, we're the 1%ers folks.

00:06:00.000 | The argument I think for the high estimate is that life on Earth appears to have started quickly after conditions were right for it.

00:06:08.000 | So if it started super quick on Earth, maybe it's pretty easy to start when the conditions are right.

00:06:13.000 | And the conditions would be right if we pass the previous parameter of it being a habitable planet.

00:06:18.000 | Again, these parameters stack on top of each other, meaning they're conditioned on whatever the thing that the previous parameter represents being true.

00:06:27.000 | If we stick just on Earth for our evidence, then the argument for the pessimistic view is that there doesn't seem to be evidence of abiogenesis,

00:06:37.000 | or the origination of life occurring more than once on Earth.

00:06:42.000 | As far as I could tell, I did not see any good evidence that life sprung up on Earth more than once.

00:06:48.000 | Meaning evidence of very different kinds of ancestor organisms.

00:06:54.000 | Alright, now we're starting to have some fun.

00:06:57.000 | The probability of intelligent life developing.

00:07:00.000 | This is of course probably one I talk a lot about in the context of artificial intelligence.

00:07:04.000 | Optimistic estimate I've seen is 1%, and the pessimistic one is 0.1%.

00:07:09.000 | I tend to actually see this as pretty high probability.

00:07:12.000 | In fact, I think that once life starts, intelligence is basically 100%.

00:07:17.000 | It's almost inevitable if given enough time.

00:07:20.000 | The open question to me is how long do there have to be a range of stable conditions that support the evolution of life?

00:07:28.000 | And what precisely that range is once life gets going.

00:07:32.000 | In general, the argument for the higher value is that complexity of systems seems to increase effortlessly.

00:07:37.000 | And the argument for the lower value is that humans are allegedly the only intelligent species on Earth

00:07:46.000 | among a lot of the species that have lived here.

00:07:49.000 | So it may be quite difficult even for the evolutionary process to create something like the human brain.

00:07:55.000 | Which I do think is quite a special creation, despite its, in my case, occasional manifestation as dad jokes on Twitter.

00:08:06.000 | Okay. Oh, and I don't understand the optimistic estimate 1% that I saw in a few places, so I doubled it to 2%.

00:08:14.000 | That's where I stand on the probability of intelligent life developing.

00:08:18.000 | There you go. Double it.

00:08:20.000 | Okay. Ability to communicate.

00:08:22.000 | I kind of think of this as the percent of civilizations that become technologically advanced

00:08:28.000 | in the more general context of building advanced technologies.

00:08:31.000 | And I tend to see communication as bigger here than maybe the original Drake estimate did

00:08:36.000 | in that it's likely to go beyond electromagnetic communication,

00:08:39.000 | something that we're not even aware of currently.

00:08:42.000 | So the argument for the high value here is that, again, systems seem to increase in complexity effortlessly.

00:08:49.000 | So it seems to me that tech advancement is inevitable once you have a sufficiently intelligent civilization.

00:08:58.000 | The arguments that I find somewhat interesting for the more pessimistic estimate is that civilizations,

00:09:05.000 | perhaps in time, tend to isolate themselves.

00:09:08.000 | They perhaps lose interest in colonization or just broadly in the whole task of exploration and communication.

00:09:16.000 | Another idea is that possibly there is a divergent methodology to the ways that intelligent civilizations might communicate.

00:09:25.000 | And so there might not be intersection about them being able to communicate with each other,

00:09:29.000 | like totally new ways of information transfer that we're just not even aware of currently,

00:09:34.000 | which does not involve any kind of leakage of signal that would nevertheless still be detectable.

00:09:41.000 | So I tend to be on the optimistic side of communication ability developing with the 20% estimate.

00:09:48.000 | Next is the lifetime of the civilization once it's already in that communicating advanced technology stage.

00:09:55.000 | I think this is one of the more interesting, one of the more open parameters that basically changes the game in the final estimate.

00:10:03.000 | This is where the most variability comes from.

00:10:06.000 | The previous parameters I find inspiring as a scientist and engineer.

00:10:10.000 | This parameter I find inspiring as a human, because the higher we can get it up as a human civilization,

00:10:17.000 | the more likely it is that we make extensive, deep, meaningful contact with other intelligent alien civilizations.

00:10:27.000 | So the optimistic values here are very high and they range all over the place.

00:10:32.000 | But it centers around the idea that there's one or multiple great filters,

00:10:35.000 | and once we get past them as a technological civilization,

00:10:39.000 | then we're basically immortal from a civilization perspective,

00:10:43.000 | that we will increasingly colonize space, I guess diversifying our use of resources,

00:10:49.000 | such that it becomes increasingly more difficult to destroy ourselves through the various existential threats that we face.

00:10:57.000 | The pessimistic estimate, if we look at human civilization as an average case,

00:11:01.000 | and assume we destroy ourselves within a couple of years,

00:11:04.000 | then for humans the stage of advanced technology is only going to last about 100 years.

00:11:09.000 | When we were able to send out explicit electromagnetic signal,

00:11:13.000 | of course I don't think we chose to do so explicitly until maybe a few decades ago,

00:11:20.000 | I don't remember, I think it was the 70s, stairway to heaven Led Zeppelin era, there you go.

00:11:26.000 | My estimate, to be honest, in terms of the survival of human civilization is almost always pretty optimistic.

00:11:34.000 | The actual estimate of the lifetime ranges all over the place.

00:11:38.000 | I think my current estimate, I just put it 10,000 years, I think even that's really far away.

00:11:44.000 | That's a hundred centuries from now.

00:11:47.000 | We're just in the first 100, 150 years of our advanced technological development,

00:11:52.000 | and what's going to happen in the next 100 of those,

00:11:55.000 | especially given that the rate of innovation seems to be accelerating,

00:12:01.000 | the essentials of my optimism is grounded in the fact that the forces of good

00:12:05.000 | will be able to out-innovate the forces of evil.

00:12:08.000 | Now what that looks like 10,000 years from now,

00:12:12.000 | it's like impossible for me to even imagine,

00:12:15.000 | so I'm uncomfortable with an estimate of one billion years from now.

00:12:19.000 | So that's why I put my optimistic, but not too optimistic,

00:12:24.000 | estimate of a lifetime of advanced technological civilization at 10,000 years.

00:12:30.000 | We're 100 years in, 9,900 years to go to prove me wrong.

00:12:35.000 | And finally this extra parameter of the number of times a civilization is born on a planet,

00:12:42.000 | given the age of a planet, and if it is habitable,

00:12:46.000 | then I think, and some optimistic estimates think,

00:12:49.000 | that it's possible for intelligent civilizations to be reborn on a planet,

00:12:54.000 | and put that value at three.

00:12:56.000 | The original estimate, of course, it wasn't part of the Drake equation,

00:12:59.000 | so it was at one, and so that's the pessimistic estimate.

00:13:03.000 | Okay, so we multiply all these together,

00:13:05.000 | of course the percentages are treated as fractions,

00:13:08.000 | so 13% is .13, for example,

00:13:11.000 | and the result of that multiplication is the estimate of intelligent alien civilizations

00:13:16.000 | that are capable of communicating in our galaxy.

00:13:20.000 | And so for these three estimates, the result is 468,000 for the optimistic estimate,

00:13:28.000 | very, very close to zero for the pessimistic estimate,

00:13:33.000 | and 0.7 for my estimate.

00:13:39.000 | Now that's for our Milky Way galaxy.

00:13:42.000 | Interestingly enough, the estimates for the number of galaxies

00:13:45.000 | in the observable universe seems to be changing, and growing actually,

00:13:50.000 | and the current estimate that I'm aware of is actually 2 trillion galaxies,

00:13:55.000 | which is a very high number.

00:13:56.000 | So if we look at the number of alien communicating civilizations in the universe,

00:14:01.000 | it's 940 quadrillion, which is 1,000 trillion, for the optimistic estimate.

00:14:10.000 | It's 300,000 for the pessimistic estimate,

00:14:15.000 | and 1.4 trillion for my estimate as of this hour today.

00:14:21.000 | Obviously there's quite a bit of variability,

00:14:23.000 | and I find it quite entertaining that my estimate landed on very close to one,

00:14:30.000 | which aligns well with the idea that if we're pretty average in the Milky Way,

00:14:34.000 | we're pretty average, that we just may be the only ones in the Milky Way galaxy.

00:14:41.000 | But every galaxy's got one.

00:14:44.000 | There's a bunch of takeaways I have from this quick thought experiment,

00:14:48.000 | and the reason I made the video is I wanted to go through the thought experiment,

00:14:52.000 | provide my estimates, and also reason through the very question itself,

00:14:57.000 | and some of the open questions around the estimate.

00:15:00.000 | So my current view is that we're not alone in terms of communicating

00:15:05.000 | alien intelligent civilizations in the universe.

00:15:11.000 | But the sense I have in terms of the very concept of communication

00:15:15.000 | is that we don't yet have the tools of science to understand what it means

00:15:19.000 | to communicate with alien intelligence.

00:15:23.000 | I tend to believe that aliens are very unlikely to have the humanoid form,

00:15:30.000 | that much more likely the variety of life is greater than we imagine

00:15:35.000 | and greater than we can imagine.

00:15:39.000 | Some of the variability would perhaps invalidate entirely the very structure

00:15:45.000 | of the Drake equation itself, which makes a lot of cosmological assumptions.

00:15:50.000 | Life could exist in different dimensions,

00:15:53.000 | whatever the heck that would even mean for a physics perspective.

00:15:57.000 | As Carl Sagan talked about, it could exist on very different time scales

00:16:02.000 | and very different spatial scales, which would make communication to us appear,

00:16:06.000 | like I think Sagan said, like noise.

00:16:09.000 | Because of our tools, but also because of the human-centric perspective

00:16:12.000 | we have on intelligence, that we're just not accustomed to trying to detect

00:16:17.000 | signal that operates in a different time scale

00:16:20.000 | and even on a different spatial scale.

00:16:22.000 | And not just life itself, I think the variety and extent of intelligence

00:16:28.000 | and communication methodology is greater than we can imagine

00:16:33.000 | and greater than we can imagine.

00:16:36.000 | Intelligent beings could operate at different conceptual spaces

00:16:39.000 | or layers of abstraction.

00:16:41.000 | The nature of communication, I think for humans it's in the space of ideas.

00:16:45.000 | It could be in the space of experiences,

00:16:48.000 | or it could be in the space of whatever lays behind consciousness, for example.

00:16:54.000 | Consciousness itself may be aliens communicating with us.

00:16:59.000 | I mean, from the current scientific perspective, all of this sounds pretty crazy,

00:17:03.000 | but if you step away and just think from first principles

00:17:07.000 | of how little we actually understand about the basic nature of the human mind,

00:17:14.000 | then you have to think that understanding our mind

00:17:18.000 | may unlock some totally new ways of communication

00:17:22.000 | and unlock our understanding of what it means

00:17:25.000 | to be an intelligent civilization

00:17:27.000 | that will totally transform the estimates provided by the Drake equation.

00:17:31.000 | And that's why I think it's really inspiring to scientists, engineers,

00:17:35.000 | just curious minds that the pursuits maybe in my field of AI

00:17:41.000 | and perhaps eventually the field of AI starts to encompassing

00:17:45.000 | the concepts of artificial consciousness.

00:17:47.000 | I think that provides the opportunity for both the scientists

00:17:51.000 | and the engineers to understand the human mind

00:17:54.000 | and to build artificial versions of it, you know,

00:17:57.000 | artificial general intelligence.

00:17:59.000 | And that seems to hold the key.

00:18:01.000 | And that is an engineering problem, is a scientific problem,

00:18:04.000 | but it seems to hold the key for us to be able to better understand

00:18:07.000 | what kind of other intelligent civilizations might be out there.

00:18:10.000 | Again, that's super exciting because in a sense,

00:18:13.000 | understanding ourselves is one way to search

00:18:18.000 | for intelligent civilizations out there.

00:18:21.000 | And in general, as I mentioned, I think all,

00:18:25.000 | or at least most of the parameters in the Drake equation

00:18:28.000 | can be illuminated through science and through our engineering pursuit.

00:18:32.000 | So if we discover life on Mars, for example,

00:18:35.000 | that shows that life is doable elsewhere.

00:18:39.000 | If we are able to build artificial general intelligence systems,

00:18:42.000 | at least to me, that shows that intelligence is doable elsewhere

00:18:46.000 | other than the human brain.

00:18:49.000 | And, you know, as a society,

00:18:52.000 | if we're able to avoid existential risks that are before us today,

00:18:56.000 | I think that shows that survival is doable elsewhere.

00:19:01.000 | Okay, looking at point three, four, and five quickly,

00:19:05.000 | let me say that this whole idea of other intelligent alien civilizations

00:19:09.000 | out there is really exciting and inspiring to me.

00:19:13.000 | So I hope that governments, nation states,

00:19:17.000 | will be able to look at the search for intelligent life,

00:19:22.000 | not as a threat, not as something that you keep as a secret,

00:19:26.000 | but as something that can inspire us.

00:19:29.000 | I think we're humans first and Americans second.

00:19:33.000 | We're curious descendants of apes.

00:19:36.000 | And I think the idea of threats and secrecy,

00:19:40.000 | I hope will become an outdated concept.

00:19:44.000 | But of course, it's not just about hope.

00:19:47.000 | You have to work hard to make it happen.

00:19:49.000 | You have to have actual practical ideas how we get there.

00:19:52.000 | Because right now, the old systems are stuck in this place

00:19:55.000 | where it's nice to have two superpowers fighting against each other.

00:19:59.000 | There's the Soviet Union and the United States.

00:20:01.000 | Maybe the 21st century will be defined by China

00:20:04.000 | versus the United States and so on.

00:20:06.000 | I think it's possible, and I think we have to build systems

00:20:08.000 | that move us beyond that.

00:20:10.000 | I think for point number four, I think doing so is essential

00:20:13.000 | for the survival of the human species.

00:20:16.000 | Again, that's my current view, but I think about this a lot,

00:20:19.000 | and I go back and forth.

00:20:21.000 | It mostly has to do about, at least my thinking,

00:20:25.000 | on how much evil there is in the world.

00:20:28.000 | And right now, for a time at least, I'm quite optimistic

00:20:33.000 | about the fundamental good in human nature.

00:20:37.000 | And finally, of course, in terms of increasing the lifetime

00:20:42.000 | of human civilization, but in general,

00:20:45.000 | finding intelligent life out there,

00:20:47.000 | I think space exploration is really exciting.

00:20:52.000 | In general, this whole topic, the reason I made this video,

00:20:55.000 | the reason I have sometimes these conversations about aliens

00:20:58.000 | is I do believe that science is the best tool we have,

00:21:02.000 | but we can still have an open mind

00:21:05.000 | to the mystery of the universe around us.

00:21:08.000 | And of course, to me, the most fascinating,

00:21:11.000 | the mystery of the human mind itself.

00:21:15.000 | So clearly, this particular human mind has to apologize

00:21:19.000 | for the probably too long, boring rambling about aliens,

00:21:24.000 | but I hope for the few of you still listening

00:21:28.000 | that it was at least somewhat interesting.

00:21:32.000 | Again, please do check out the Brave browser

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00:21:37.000 | to show support for the podcast that I host.

00:21:41.000 | Thanks for tuning in.

00:21:42.000 | See you next time.

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How many alien civilizations are out there?

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