Fermi Paradox Great Filters: Space and Time

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Our galaxy consists of hundreds of billions of stars and trillions of planets. There’s something deeply disturbing about the idea that we might be the only ones living in it. So today we return to the Fermi Paradox series for the first in a short series of episodes discussing all the possible factors which might contribute to making technological civilizations like our own extraordinarily uncommon. We have looked at, and will discuss more in the future, some possible ways in which we might be surrounded by advanced civilizations and just not be aware of it. We can never safely discount the possibility that they might drop by for a visit, if indeed they have not already done so. However, the Occam’s Razor approach to the Fermi Paradox, the seeming contradiction between the immensity of the Universe, and the apparent absence of any other advanced civilization than our own, is that there just aren’t any close enough for us to detect. That’s really not a big problem in and of itself. After all, we can’t even see most of the equipment we left on our own Moon half a century ago, let alone buildings on other planets around other stars, and we certainly haven’t built anything on other planets yet. No man has ever traveled further than our own Moon, and except for those twelve and some hundreds who have traveled a couple hundred kilometers over the planet to low orbit, nobody has yet left our own homeworld. We don’t broadcast our signals very loudly and indeed they have gotten quieter as we’ve gotten more advanced, since efficiency encourages us to make them ever quieter and harder to recognize as a signal. We’d have problems hearing our own transmission with our own detectors much further away than our immediate neighboring star systems. Taken at face value then, it’s not much of a Paradox. So long as technological civilizations aren’t so common that virtually every star hosts one, there could be a billion of them in our galaxy alone. But this is not the actual Fermi Paradox and never has been, people get lost in that a bit. The paradox arises from conversations and speculation beginning around the mid-20th century, as we started getting an idea of how truly old and huge the Universe is, and also with the growing recognition that there was actually the possibility of reaching other planets and living on them. It is the awareness of this possible expansion that creates the Paradox. If you believe we won’t colonize our own solar system, let alone other ones, then there’s no real paradox. The Fermi Paradox is more properly known as the Fermi-Hart Paradox because it was Michael Hart’s conjecture back in 1975 that fully manifested the real paradox. We had landed on the Moon and were discussing the creation of bases and colonies on other planets. The first tentative interstellar ships were on the drawing table. Looking at that, he pointed out that we should expect our civilization to generally seek to expand and make use of places with no life on them as new homes for humans and their furry, feathered, scaly and other cousins. We do seem to want to do this and it does appear possible under known science which is steadily improving. The basic nature of biology seems to imply that other non terrestrial civilizations should tend to feel the same way. Any critters who have successfully clawed their way up Darwin’s Ladder ought to be strongly inclined to want to spread out and reproduce; this should hold for any natural alien biology as well. This is the paradox, and it gets far worse when you come to realize that colonizing other planets is advantageous and doable, but far less so than constructing vast swarms of artificial habitats to take advantage of all the sun’s light that is not hitting planets, which is very nearly all of it. Earth gets only a billionth of the light the Sun makes. Access to such power levels makes interstellar travel viable even without improved technology, as we’ve discussed elsewhere, and continuous improvements in computers and robotics make that travel, or the construction of such swarms, often called Dyson Swarms, far easier too. Now up until the day we actually have a colony in another solar system that builds its own colony ship to send folks further out, or have vast swarms of habitats whose combined living area grossly exceeds that of Earth’s, it is an entirely valid objection to say we can’t be sure if such expansion waves are possible from a practical standpoint. We’ve had the technology to land people on Mars since we went to the Moon, or to establish a base on the Moon, yet we’ve done neither, so capability doesn’t imply practicality. However, on this channel, I’ve spent dozens of episodes talking about getting off of Earth, constructing habitats, terraforming planets, and building interstellar starships. We’ve always vigorously confined ourselves to known science when doing this, barring a few looks at concepts like warp drives or wormholes. If you’re a channel regular, you probably feel pretty confident that interstellar travel is within reach, and that we can overcome those challenges to settle our own system and even our whole galaxy. So to restate our problem, if we can see a clear path to soon achieving interstellar travel as a species… a species that has evolved in a relatively short period of time on the cosmic time-scale, and if there is similar life out there in the galaxy, then our galaxy should be saturated with other evolved species who have already done so… so where the heck are they? Nor does the paradox end at the galaxy’s edge, and later this summer we’ll look at intergalactic colonization, and show that it is viable under known science as well, and we never know when some new Einstein might emerge to show us easier and faster means of space travel. The point is if we can do it, so could other civilizations, and even if some were disinclined, or blew themselves up before doing it, the galaxy ought to be settled a thousand times over by now if such civilizations are even slightly common. If just one planet per billion ever spawned civilizations with the capability and desire to settle the galaxy, and if just one of those did it even a few millions years before now, the galaxy should be as untamed and wild as New York or London. And you can’t miss such civilizations. You don’t need to see their homeworld, you don’t need to hear their radio, they’re just all over the place and there’s dozens of ways they’d be detectable, same as trying to detect intelligence in a major metropolis. Trying to hide all those blisteringly obvious signs of civilization would seem both impossible and pointless, you don’t hide civilizations you advertise them. Inside that framework of ideas folks have come up with tons of possible explanations for why such civilizations might not expand and build, or might hide, or might evolve in some way as to not wish to expand. Some seem a bit ludicrous on the surface, others are more sound but still seem fatally flawed. We went through a ton of both types back in the Fermi Paradox Compendium and we’ll give each one a more thorough going over in the future. But getting back to the topic for today, and this sub-series as well... since the reasoning on a lot of those solutions tends to break down, a lot of folks figure that civilizations just aren’t too common at all. Maybe planets that can host life, especially complex life, are far rarer than we think. The Rare Earth hypothesis. Maybe they’re decently common but the pathway to higher intelligence is a lot less likely than we think, with many hurdles filtering out evolutionary improvements along the road to sentience and sapience, or diverting them down different evolutionary paths. Maybe one of these filters is so strong, and so unlikely to be passed through, that virtually no one does. This has become known as the Great Filter Hypothesis. Now this intellectual camp on the Fermi Paradox is a big and diverse one, with many different suggestions for what causes technological civilizations to be rare, but that’s the shared view. The solution to the Fermi Paradox is that we don’t see alien civilizations because there are none, or they are so far away that we can’t see them yet... but not because they aren’t visible. You could see a galaxy sprawling Kardashev 3 civilization even billions of light years away, but the light from them wouldn’t have reached us yet. There may be no civilizations within a billion light years of us, but if one did arise 900 million light years away 800 million years ago, we couldn’t see it yet, even if it had turned entire stars into giant broadcast systems to say hello. There are many filters, some stronger than others, and it is hard to evaluate their relative strengths as we don’t know enough yet. However I generally classify them into 4 groups. Lesser Filters, those we’d be inclined to think would be passed through by most, given enough time. Minor Filters, those which most wouldn’t pass but we’d expect at least a  small percentage to squeak through. Major Filters are ones which very few pass through but given the scale of the galaxy and the universe, you’d still expect a decent number of them overall. And lastly Great Filters, those which are lottery-odds at best, one in a million or less kinds of filters. This is the kind of filter that singlehandedly would shift civilizations from being so common you could hear each other's radio transmissions easily to so rare there might only be a handful galaxy, or less. Now most filters can be broken into many smaller ones. Earth might be quite rare but there’s a lot of ways it might be rare, none of which by themselves is terribly improbable, yet they might stack up to be such a Great Filter when assessed together. We showed an example of that in the aforementioned Compendium episode, arbitrarily assigning 50/50 coin flip odds to each of 50 proposed filters, and seeing how that stacked up to a probability so low that you’d have to search thousands of galaxies and quadrillions of stars to find another civilization. But those were not the only proposed filters by any means, and while many of them are demonstrably stronger than 50%, others might not be filters at all, but simply delaying factors. In this episode and the rest of this short series, we will be examining general categories of these filters in detail. Most discussions of this begin with the Rare Earth filters, but there are a few Great Filters that folks tend to bypass along the way, and we’ll be looking at some of those today. Some of you might be nodding your heads now and thinking of things like supernovae and gamma ray bursts, or the conditions and time spans necessary for heavy elements to collect, and indeed you are right to do so, but we can go back even further. For us to examine all the reasons why civilizations might be rare in this universe, we should not skip the rarity of our Universe itself, nor the importance of time when regarding it. So that will be our focus for today. Later in the series we’ll talk about the filters to get to intelligent life, of which we have many examples besides humans, and from there we will discuss all of the hurdles and filters you must navigate in going from high animal intelligence to launching rockets into space. These are all big topics which might need further sub-division as we go but for now those will be our primary great filters, and each will get its own episode. But today we are looking at 3 which are not given much attention, largely because the Fermi Paradox has been phrased rather poorly. A big problem in many examinations of the Fermi Paradox, and what creates holes in various arguments concerning it, is that it tends to focus on our galaxy alone. The Universe does not end there, and not only might we detect civilizations further away than in our galaxy, we might have an easier time in doing this if they colonize other galaxies. This does not even require faster than light travel, though most folks tend to think we will achieve that one day. Personally I do not, both because known science doesn’t permit it except under some dubious scenarios that are mathematically valid but probably not physically valid, and because it tends to only exacerbate the problems in the Fermi Paradox. If faster than light (FTL) travel is possible, then you need to account for alien critters from civilizations that emerged over a billion light years away but more recently than a billion years ago. Indeed what we often consider the Universe, better known as the Observable Universe, are those parts that light has had time to reach us from and which are not traveling away from us faster than light. If you have FTL, you have to consider running into civilizations that do too and which originated in areas beyond our ability to see. And while we can’t be sure, the common thought is that our Universe is much larger than the observable parts, possibly a little bigger, possibly vastly bigger or even infinite. Part of the reason I don’t expect us to ever discover a means of traveling faster than light is because of the Fermi Paradox. A billion light years already seems a huge volume to not find other civilizations in, but it’s only about a millionth of the Observable Universe and the entire Universe might be much bigger, and even potentially infinite. If the latter is the case, an infinite universe implies infinite civilizations, even if they are vastly far apart. You can review the various reasons for that in the Infinite Improbability Issues episode, which are equally valid for an infinite or super-large universe as well as alternate timelines. Surely if FTL were possible some of those would have swung by here. But I just mentioned timelines and alternate universes and that’s more of the problem. If time travel is possible for instance, and if you have FTL travel, you should have time travel, fundamentally they’re the same thing. We have to worry not just about civilizations that might have popped up recently but are too far away to see yet, but also ones that haven’t even existed yet. The joke about what year time travel gets invented is ‘all of them’, and the ‘aliens’ you meet might even be folks from Earth far in the future. We have this same problem with alternate dimensions and realities, if they exist and you can travel to them, then that is presumably a two way street, and folks should be showing up from them as well. There are very solid scientific reasons why traveling through time, traveling to other realities, or traveling faster than light should be impossible, but I consider the strongest evidence against them to be that we haven’t run into any folks with this technology. We can reason that some aliens might be very hesitant to show off such technology to a primitive species, for whatever reason, but it’s quite a stretch to assume every single member of every species that exists in the entire universe, or its entire future history, or in other Universes, all feels that way. Nor is that in conflict with the idea that no one seems to be doing sub-light speed interstellar travel either, since for the latter I only need to establish that no one is doing it in our relatively small chunk of time and space, not the sheer immensity of the entirety of all time and space or even in other possible realities. Yet this does give us our first Great Filter too, and it’s called the Fine Tuned Universe. You’ve probably heard of it before in discussion of the Anthropic Principle. We’ve discussed that principle before, and have done episodes on two of its more common examples, the Doomsday Argument and the Simulation Hypothesis. But I intentionally avoided the Fine Tuned Universe consideration because it wasn’t pertinent at the time and tends to make folks get off onto heated theological discussions and attack each other, which I try to discourage here. Let me explain it quickly and simply though. The fundamental structure of our world and our universe is based on various physical constants, the most obvious being gravity which is strangely weaker than the other three known forces. Were it as strong as they, you wouldn’t be able to put enough atoms in one place to make even single celled organisms without their undergoing gravitational collapse into tiny black holes. So presumably any universe where gravity was that strong could not host life, though we’ll beat on that notion later this summer when we visit the concept of a Boltzmann Brain. Gravity is just one such example, we have a number of physical factors and dimensionless physical constants, that if they differed significantly from what they do in this Universe, would seem to prevent life from being possible. Indeed even very tiny alterations to these could make life impossible and if something has a value of 1,234,576, and can have any value up to a billion, but only 1,234,566, 67, and 68 permit life, you’re really lucky to live in a place where it has that value. In fact the odds against it are… well… astronomical. That is what causes the big theological arguments and why it is called Fine Tuning. One camp argues that it is so insanely improbable that those constants can’t possibly be random and if they aren’t random then some Intelligent Designer must have set them up that way. The other camp says that it can be random, if we simply assume a ridiculously large number of other realities with different values in which life doesn’t exist… and thus has no need to worry about how improbable their existence is. Yet I’ve never personally considered either argument particularly compelling. I could propose nearly exact copies of Earth with minor variations in gravity or pressure or composition and how these variations would prevent complex life from emerging, and indeed we’ll be discussing how such minor variations might impact the development of complex life later in this series. Those variations will include versions of Earth having less mass, different compositions, etc. A person living a few hundred years back would have been entirely justified in wondering if near exact copies of Earth, just with weaker gravity or thinner air, might exist. We now know though that these are not independent variables. If you want stronger gravity you need a more massive planet, or one that is denser. The surface gravity of Earth is that specific, seemingly arbitrary value of 9.807 meters per second squared for a reason and can’t just be 9.806 or 8, let alone 9,807 meters per second. If you head up from sea level a bit, climb up a mountain, gravity drops in a clear and predictable fashion. The pressure of 101,325 Pascals could vary from less than a Pascal to billions of them, but there is a reason why it is what it is and it is directly linked to the surface gravity, change one and you change the other. As we’ll see later in the series, there is more to atmospheric pressure than just that, but then none of those factors are random in their effect either. So I don’t like the Fine Tuning arguments just taking for a given that all of these physical constants have values pulled out of a hat, be it random or by divine fiat. It may be so, but it is entirely possible these things are connected. A man standing on a bunch of hexagonal cobblestones might be justified in wondering if that’s a natural phenomena and find himself absorbed in investigating how it could be so, until someone comes by and asks him to please stop poking at the bricks in her garden path. But in neither scenario, natural or artificial, would he be correct in simply assuming that the pattern was completely random. It could be that such a pattern might emerge somewhere in a vast enough field of stones, but we know from places like the Giant’s Causeway that such things can be the result of complex geological processes making them much more likely. We also know that humans like to build paths, generally out of clean geometric shapes that fit together and are of dimensions appropriate to our own bodies, width, and footspan. Neither is actually random. Yet those values could be random, or from a set that’s still quite large and in which very few combinations permit life, so we see this as our first Great Filter. Projected numbers vary on this wildly, and again we have no idea how random those constants are, if at all, but in most contemplations of this concept the improbabilities of being in one that can support life are so huge that they can only be meaningfully expressed in exponential notation. So it’s a pretty monumental Great Filter. You have to live in a Universe where life is possible in order to contemplate how likely it is to encounter aliens to chat with. There may be innumerable ones where the parameters don’t permit it, or make it far less common than in ours, or even far more common. We’ll get to that more in the Boltzmann Brain episode but a Universe truly fine-tuned for life should be one in which every drop of matter is being utilized towards that purpose almost from the get go, and ours is clearly not. That said, it actually used to be. The Universe is about 14 billion years old, but back when it was only 14 million years old, it was much closer together and about the temperature of warm bathwater. This was a short period, only a few millions years, perhaps decently longer if we assume life popped up then and was able to evolve enough to survive in a few places where local phenomena like gravitational heating kept things warm until stars emerged. Indeed it might have adapted enough to the increasing cold to survive, much as we often consider comets as possible sources for life, under the Panspermia hypothesis, as an alternative to shoreline tidal pools or deep sea thermal vents. I don’t favor Panspermia myself, but we don’t know how life started on Earth yet, and comets remain a viable scenario. We don’t know what conditions are required for Earth-style carbon based life, let alone all the options. So we want to be very careful as we move forward in the series from our geocentric perspective on life not to rule out that it might emerge from a wide variety of environments and elemental compositions besides carbon and liquid water. We will also see however, that when it comes to truly complex life, this situation is reversed, and there do not appear to be many environments that would allow technological civilizations to arise and flourish. It is that sort of advanced, intelligent life that the Fermi Paradox is interested in, not more basic forms of life which are incapable of space-travel or communicating with us. Simple life might be incredibly rare too, or so common it has developed multiple times in our own solar system, but you need a lot of biodiversity to spawn intelligence, excluding the Boltzmann Brain scenario, and for that you need a lot of energy, time, and pretty ideal conditions. We’ll get more into those as this series progresses, but that’s our second Great Filter. Earth is the only plausible place in our solar system to host truly complex life sophisticated enough to build spaceships. We might find extinct or even extant microorganisms elsewhere in the solar system. It might emerge wherever an appropriate chemical soup exists that is churned around by some energy source, but there’s no place with big animals and plants around that we can see. Even in a place like Europa, where you might feasibly have hidden marine life beneath the ice, it wouldn’t seem terribly realistic to expect to find civilizations. But even if life is that common, Earth composes about a millionth of the solar system’s mass, most of which is in the Sun or in the Gas Giants, neither of which seem hospitable places for life. All the other big moons and rocky planets combined still only account for a tiny fraction of the available mass in our solar system and most have no plausible energy source abundant enough to allow civilizations to have arisen there. Additionally, only a thin skin around the Earth, just the first several meters out of several million meters of rock and magma on the way to the center, actually hosts life. There are several trillion tons of matter on this planet that is incorporated into living tissues but the planet is around a billion times that in total mass, and the solar system a million times more massive than that. So in our solar system only about a quadrillionth of the matter is alive. Only a small portion of the matter in this universe is going to have the right composition, right density, and right amount of energy flux, an essential triad, to have any chance at all of being alive and a far smaller percentage of that will be positioned to be intelligent. Only one quadrillionth of  our solar system’s matter is alive and not even a thousandth of that is actually contained within humans. A billion billionth, just a quintillionth, of this solar system is made of humans, not a bad Great Filter considering that’s in the ballpark of how many stars are in the part of the Universe we can plausibly hope to see recently enough in time for civilization to have arisen and be detectable. That takes us to our third and final great filter for today, which is Time, though perhaps it's unfair to call it a Great Filter. As I mentioned a moment ago the Universe used to be the temperature of warm bathwater, and life might have evolved all over back then, but the big hindrance to doing so was the lack of heavy elements. In astronomy and cosmology we usually refer to all elements heavier than hydrogen and helium as metals, and for the most part only hydrogen and helium were around right after the big bang. Some heavier elements in trace amounts were around even then, but large quantities of them didn’t begin appearing till stars formed and died. The biggest stars live the shortest time, and make the heaviest elements, so those started appearing on the scene quite early in the game, about a hundred million years in, and the biggest stars are often shorter-lived than that. Yet it takes a while to accumulate a lot of these, and as we’ll see next time there’s a lot of factors that would have made the early universe inhospitable too, even in those lucky few places that might have gotten enough metals for a decent planet to form. But this is where we see time as a Great Filter and also see an important Fermi Paradox concept that people miss a lot. This Universe is still quite young at 14 billion years old, check back in 14 trillion years and it will still be quite ripe with stars, though appear far less massive and far bigger. Just one over-sized galaxy composed of the handful of our nearest neighboring galaxies merged together, an island of stars surrounded by an ocean of night trillions of light years across. Universal expansion will steal away virtually every galaxy we can see now, even as time lets light from further and further away reach us. Check back in 14 quadrillion years and it will all be dark, lit only occasionally by the collision of dead stars with each other or leftover planets. We’ve discussed how life might continue on  during that time and beyond, indeed even flourish, but it won’t be naturally occurring anymore. No new planets spawning new civilizations. For the next several trillion years there will be stars and planets forming continuously, and barring artificial intervention life should be popping up a lot more often for most of that time. Our biggest constant filter is time not because some filters are impassable, but rather because they each take time to pass and you only have so much of it. Anything which delays development could make civilizations not emerge until their star dies, but more importantly, the Universe is young, and most of the stars in it are much younger. Most of them will live far longer than our Sun, which is actually on the heavy and short-lived side of normal, so some planet around a sun that will live 20 billion years might not host civilizations yet, but it’s still got a lot of time to get that done. The Rare Earth and Great Filter camps generally do not think life is all that rare, but as we’ll see in the series, the focus is more that advanced life like ourselves is pretty rare so far. Given more time, given more metals in the universe, we expect to see many more places host life and more of that develop intelligence. Check back in ten billion years and the galaxy might be boiling over in life-bearing planets with intelligent critters roaming around them. If we checked back in ten million years, we’d actually tend to expect life everywhere too, but originating from Earth, with us colonizing outwards. This is our last point for today, and it is what I call the Time Elapse Argument or (TEA). It comes up a lot in contemplating whether or not some peculiar phenomena is natural or indicates artificiality. We expect that as the universe gets older we would see more artificial aspects. More civilization arising and expanding and manipulating matter and energy. It follows from that then that a younger Universe would show less signs of all of the above. And since when we look far away in space we are also looking far back in time, you would expect anything which is artificial in nature to be less common the further away you look. So anytime we see some phenomena that folks think might indicate intelligence, our quickest way to check is to see if distant parts of the Universe have less of them. Ring galaxies for instance were often looked at as signs of an emerging Kardashev 3 civilization. The problem is they don’t appear any less common as you look further into the past... at least not until you look so far back that galaxy formation itself was still pretty rudimentary. Quasars, on the other hand, were more common in the past, with most galaxies having settled down since then, and so are clearly not a sign of life. Now some folks will point to the Supervoids, those huge areas of space absent of virtually all galaxies, and say that could be artificial. This is flawed logic for a number of reasons. The voids are indeed bigger now than they used to be, but they’re no bigger than the rate of expansion of the Universe would suggest. More importantly, they were there  from the beginning expanding along with everything else and seem to do that in every direction we look. We wouldn’t expect civilizations springing up all over the universe to be expanding in the same ways, at the same rates, or from the same starting points. Especially ones predating any realistic timeline for the development of Earth-like planets. A void expanding around an emerging civilization as it begins converting stars into engines should have a starting point of at least a few billion years after the galaxies began forming, not right from the very outset. It also ought to give off huge amounts of Infrared radiation and exhibit measurable gravity in excess of the apparent matter present in them, which the voids do not. They should actually be devoid of visible stars entirely, which the voids also are not. There’s tons of stars and galaxies in those voids, just way less than in other places. But that’s the Time Elapse Argument in a nutshell, and it’s one that is important to keep in mind while contemplating the Fermi Paradox, along with Exclusivity and statistics in general. You might have gotten a rocky planet forming around a yellow sun as early as a couple hundred million years into the universe, possibly even seeded with life by comets made up of frozen ice from the Bathwater Epoch, but these ought to be very uncommon and the Fermi Paradox is all a statistics game. On the same note, we can easily talk about civilizations that might be very different than ours in behavior. They may not be interested in expansion, or may be going out of their way to hide, However we are operating on the assumption that intelligent life that manifest technological civilizations will tend to favor that kind of behavior for the same reasons we do. Evolution should favor growth-inclined species, and a taste for exploration and challenges ought to come with the curiosity you’d expect to be a prerequisite for developing technology. There may be exceptions to this, but they ought not be too common, and in this context we only care if the reverse is true, that such behavior is exceedingly rare. If expansion across a galaxy is possible and practical, than the desire to do it has to manifest much less often than the number of civilizations capable of it in a galaxy. If there is less than one such civ per galaxy, no problem, but if you’re talking thousands or millions, it gets a bit ridiculous to assume they all can but none choose too, so you either have to assume they can’t, because they don’t exist, or they can’t because it isn’t practical, or you have to assume that they don’t want to for some reason. As mentioned, we have talked about some reasons not to before and will do so again in the future, and of course we talk about the practicality of interstellar colonization all the time here. But our focus for the rest of this series on Great Filters of the Fermi Paradox will center around why they might just be incredibly rare, and we’ll pick that up in the next episode of the series by focusing on the Rare Earth Hypothesis, but also discussing whether an Earth-like environment is really necessary for life and why places with life but unlike Earth might not be able to evolve more sophisticated life as well. Next week we will be looking at ways to get a permanent foothold off of Earth, and closing out the Upward Bound Series by looking at Orbital Rings, massive structures that don’t just give you a foothold in space but rather a nice comfortable highway to the stars. To get alerts when those and other episodes come out, make sure to subscribe to the channel, and you can visit this channel’s website, IsaacArthur.net, or our Patreon page, to help donate and support future episodes. If you enjoyed this episode, please like it and share it with others. Until next time, thanks for watching, and have a great week!
Info
Channel: Isaac Arthur
Views: 587,493
Rating: 4.8662357 out of 5
Keywords: Fermi Paradox, Aliens, Alien Civilization, Rare Earth, Fine Tuned Universe, Great Filter, extraterrestrial, Anthropic Principle, Drake's Equation, SETI
Id: ZlgyxQJHHcY
Channel Id: undefined
Length: 37min 39sec (2259 seconds)
Published: Thu Jun 22 2017
Reddit Comments

Not a huge fan of the voiceover saying one thing, but the screen having other text. Specifically the notes on the screen about our moon.

Rest was good.

👍︎︎ 2 👤︎︎ u/persolb 📅︎︎ Jun 23 2017 🗫︎ replies

So, the TEA argument is one I've thought a lot about recently and never had a name for. The concept that the time involved with the creation of complex life would have a direct impact on our observation of complex life, especially in (but not limited to) the truly young galaxies that we can observe, just seemed fairly obvious to me. I'm glad Isaac covered that one. I'm going to go over my understanding of it, and if anyone can point out any flaws in my reasoning, I'd greatly appreciate it.

Specifically, my thoughts on this recently have been along the lines of truly metal poor systems. My first assumption, which I'm almost positive is correct, is that the creation of every element aside from hydrogen requires the fusion reaction of a star. My second assumption is that without a wide variety of elements, life would not form. Maybe that's a little less obvious, but if you only have, say, the first 8 elements to play with, then I then the possible chemical reactions are so low as to make complex life impossible. The third assumption was one I learned recently from cosmos, which was the progress of star formation in our universe. Apparently, our star is in the third wave of stars forming in our galaxy, hence it's metal content.

So, with all these as given, the first wave of stars certainly couldn't have held life (hence the TEA argument for really distance galaxies), and it's also possible that the second wave of stars also didn't have the capability for life due to its non hydrogen content being restricted both in mass quantity and elemental quantity. If this is the case, then the only possible planets in the surrounding area that would have a decent chance to visibly be hosting technological life would be in, say, a bubble around us between 1 and 0.5 billion light years distant. That was my estimate, though I honestly think it's a bit large.

So, to kinda spearhead this, is this basically the TEA argument? And is this one of the things that groups like SETI take into account when scanning stars for signs of technological life?

👍︎︎ 1 👤︎︎ u/mr_christophelees 📅︎︎ Jun 26 2017 🗫︎ replies
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