Fermi Paradox

real ways that that could happen. It's meant to open your eyes, hopefully get you to take these ideas seriously too, and ideally get you to take action. But just as much, I hope by pointing out just how close we are to the brink of disaster, you come to feel the way that I have about your fellow humans and humanity as a whole. That we are flawed and ugly and brutal, for sure, but that we are worth fighting to save,

even from ourselves. That the beauty and the love that humans are capable of creating is greater than the worst of our faults. That nothing we've done is worth letting our entire species come to an untimely, impermanent end. It's a bizarre thing to say, but I found it's worth saying. Humans don't deserve to go extinct. This series is about existential risks. We're not used to this kind of risk,

nor are we really equipped to deal with them. I'll tell you a lot more about them as the series goes on, but while you listen, try to keep in mind that no horrible catastrophe, no world war, no epidemic that's ever come before, nothing we've ever been through has prepared us to take on existential risks. We have no frame of reference for them, because the destruction they can

bring is unprecedented in the history of humanity. Yet, and what maybe the weirdest turn of events in the history of our species, A whole crop of these new existential threats are suddenly looming in our near future. Each one of them could bring about the sudden and permanent end of the human race. This would be a particularly tragic thing. We humans have only just begun to live. Human civilization has been around for about ten thousand years. Think about

what we've accomplished in that relatively short time. Now, think about what it might be like to be a human after civilization has been around for a million years or a billion. So not only are the lives of those of us around today on the line, but we have to remember the lives of all the humans to come are as well, and the stakes for us avoiding extinction in the next century might be even higher than that. As we'll see in this episode, we humans may be

the only intelligent life in the entire universe. If we die, so too does all the things that make us human, All of the love and compassion, all of the inventiveness and curiosity, all of it perishes with us, not just here on Earth, but in the universe as a whole. It's staggering to think, but the responsibility for our own lives, for the future of the human race, and for intelligent life in the universe appears to suddenly rest solely in

the hands of those of us alive today. It would probably be good to know if we're alone or not, just for the sake of knowing what's on the line if we go extinct, So let's start there. As it turns out, you should know an alien by now, so should I. By this point in human history, everyone you and I know should know an alien. We should know them from work, from your kids school. They should be our neighbors. Earth should be a melting pot of not

just human cultures, but extraterrestrial ones too. At the very least, we should be certain by now that there are aliens out there, just as sure as we know that there are people living in France and Denmark. We should know that there are aliens on proximous Centauri B or trappist One F. And yet we don't, and you and I don't know any aliens, which is actually very, very weird. The reason why it's weird is that the universe we

live in is extremely old. It's nearly thirteen and a half billion years old, and our galaxy, the Milky Way, is extremely vast from the perspective of us humans. It takes a beam of light a hundred thousand years to cross it. And within our very old and very immense galaxy, there are a lot of stars, between two hundred to three hundred billion of them three hundred thousand million stars.

Working from the premise that our own stars, light and heat helped raise life here on Earth, one would think that somewhere among those three hundred thousand million stars out there, the same thing would have happened. It happened again and again. By all rights, even with just a slight fraction of those stars growing life on a planet in orbit around it, our galaxy should be teeming with life like mold on a slice of bread. There's certainly been plenty of time

for it to happen. Here on Earth, life arose within the last three and a half billion years and managed to evolve from little strands of proteins into us, sentient human beings who have come to wonder if the same thing has happened elsewhere too. Since the galaxy is nearly four times older than the time it took for intelligent life to emerge here on Earth, it's had ample time to emerge elsewhere in our galaxy too. So what we've

got is something of a mystery on our hands. The universe is by far old enough and definitely large enough to have produced intelligent life over and over and over again, and yet we have not one iota of evidence that we are anything but utterly alone in the Milky Way. It's become increasingly clear that when we look out at the night sky, there's nothing looking back at us. This is the basis of what's come to be called the Fermi paradox, and it begins, like so many great strange things.

Over lunch in the summer of nineteen fifty four physicists ambled over to the Fuller Lodge, an old two story boarding house made of human logs with a big, hulking stackstone fireplace that you could practically stand up in. The Fuller Lodge had been converted into a mess all for the people working on the Manhattan Project at Los Alamos,

New Mexico. Taking a break from refining the most destructive weapon the world has ever known into an even more destructive one, these four physicists got into chatting about the UFO fever that had recently gripped America. They dismissed the idea that reports of UFOs were in fact alien in origin, but they didn't dismiss the idea that it was possible life could exist elsewhere in the universe. It was likely

that it did, they concluded. After the group had already moved on to other topics, one of them, Enrico Fermi, abruptly returned the conversation back to aliens. Where is everybody? He asked, or perhaps, but have you ever wondered where everybody is. The precise words were lost over time, but Fermie's three lunch companions all recalled that they knew just what he meant, and they grasped the implications as well. There should be life all over our galaxy, and yet

there appears to be only us. Fairmi never formally explored his question, but it's understandable why it came to be named after him. As physicists go, Faremi was no slouch. He presided over the first controlled nuclear reaction created in a uranium pile of his design, constructed on a squash court beneath the football field at the University of Chicago.

He calculated formula that helped answer the shape of matter on the quantum level, and a family of quantum particles are named after him Fairmians, and of course he helped build the bomb. But more than Fairmi, it was an American astronomer named Michael Hart who was really responsible for the Fermi paradox. In the mid seventies, Heart wrote a paper called the Explanation for the Absence of Extraterrestrials on Earth.

He summarized and organized the arguments against the paradox, which come in a rainbow of colors with only a couple of shapes, and Heart ultimately concluded this because life should reasonably have emerged and be known to us by now. The fact that it hasn't solves the family paradox. The answer is that we are alone. Mystery solved. Michael Heart's paper struck a blow in particular to the group most

diametrically opposed to his conclusions. City researchers set the search for extraterrestrial intelligence is an offshoot of astronomy and astrobiology, and back in the early sixties, astrobiology hit the scientific scene like a bomb. It was an exciting new discipline

that treated the possibility of extraterrestrial life is real. In sharp contrast to the people who agreed with Heart, the astrobiologist camp was populated by optimists who reasoned that it is simply too unlikely for life to evolved only once throughout the entire universe. We just needed to hone the way we search for aliens, and we would surely find them.

Cd He evolved is the intelligence gathering arm of astrobiology, and set about listening for alien transmissions by aiming radio telescopes at the center of galaxies that seemed likely to host life. By the time Michael Hart published his paper said he hadn't found anything, and Hart included in his article that said he was an utter waste of time

and resources. By that time, many others, including some in Congress who funded things like st tended to agree that there is little justification for twelve million dollars taxpayer dollars to be expended for this program. Madam President, I urge my colleagues to vote in favor of this amendment, and I reserve the balance of my time and yield the floor, and I thank the chair. Yet neither hearts paper nor sti's empty handed searches have settled the mystery of the

family paradox. Because we've gotten better at observing our universe, this little mystery has only gotten more weird. Thanks to space based telescopes like the Kepler and new methods we've developed for watching stars, we found that there are a mind boggling number of potential earthlike planetile there. To qualify as a potential host for life, the planet has to

check some boxes. The star that it orbits has to be of a certain type, and in what's called its main sequence, it helps to be around the size of our Sun, which is right in the middle. Size Wise, big stars go through their fuel too quickly to give life a reasonable amount of time to emerge. On the other end, smaller stars don't burn quite warmly enough. The planet has to be a particular distance from the star.

Too too close and any life would be burned to a crisp Too far away, and the star's warmth couldn't overcome the unbearable cold of outer space. Either way, the conditions wouldn't allow for water to form or an atmosphere, both of which we assume are requirements for life to emerge. The planet needs to be in a spot relative to the Sun that's not too hot and not too cold, but just right for life. So it may not come as much of a surprise that some astronomers call this

area the Goldilocks zone. Taking all of this in to account, there are perhaps tens of billions of potentially habitable planets in the Milky Way alone, and it gets even weirder. Throughout the decades that people have attempted to resolve the family paradox, those attempts have always been focused on our galaxy, specifically, the rest of the universe is just too big to allow for the time it would take for another civilization to travel to the Milky Way and make its presence

known to us. So by leaving out the other hundred billion galaxies in the universe and there's seventy billion trillion stars, the idea that perhaps other life might exist outside our own galaxy was allowed to stay aglow as a faint member of possibility, But in two thousand thirteen that ember was snuffed too. A pair of philosophers from Oxford figured out that the math shows there has been plenty of time for intergalactic civilizations to have evolved and traveled to

our galaxy too. This is one of those Oxford philosophers under Samberg, actually suppose you wanted to go out and colonized as far as you could, how far could you go? And we found that you can literally do this over billions of light years, which means that this is also something aliens could have done. So if it's a bit weird that we haven't noticed in the alien spreading across the Milky Way, now we need to take into account.

But actually there are also millions or billions of galaxies where aliens could have come from but they haven't shown up yet. So when we finished that paper, we kind of pointed out that we made the Fermi paradox a million or a billion times worse. The Family paradox extends not only to our galaxy, but it seems to the

entire visible universe. Hm to a lot of people who think about this kind thing, it's simply too outlandish to believe that we are the only intelligent life in the entire universe, and so over the years, people have put forth some interesting answers to the family paradox on the basis that there is intelligent life out there, we just don't know it yet. At the most basic level, the arguments consists of the notions that aliens either can't or

won't make the trip to see us. Aliens have had plenty of time to colonize the galaxy and even the universe, as we've seen, even considering travel at less than the speed of light, even travel at ten percent the speed of light shall allow for the Milky Way to be

colonized in fifty million years at the most. But even allowing for plenty of time to make the trip, it's entirely possible that the trips between stars and galaxies is extremely difficult, so difficult in fact, that no intelligent civilization has ever successfully managed it, although plenty may have tried and lost a lot of their people to be impossibly hazardous trips before finally giving up. Space is far from empty. It's full of tiny particles called cosmic dust, raw material

that planets are made from. There's a dust cycle out in space where dust is blasted into space by exploding stars. This dust fills space, and even though it consists of extremely tiny particles, it would pose a hazard to any spacecraft traveling at some significant fraction of the speed of light, which again, remember something like six hundred and fifty million miles an hour. Even a tenth of that is still

sixty five million miles per hour. At these speeds, the spacecraft kinetic energy is so unimaginably huge that a collision with even some tiny piece of matter would be catastrophic. MT physicists calculated that impacting even a single grain of cosmic dust would be tantamount to the explosion of something like two and a half tons tons of T and T aboard the ship, and cosmic dust is just one

hazard that space bearing species would have to overcome. There are surely plenty of others that we haven't learned of yet. This argument has a flaw to it, though, and I want you to pay attention to it, because it's part of a theme that really all arguments regarding the Family

paradox share. If the reason aliens haven't colonized the universe is because it's extremely hard to travel between stars and galaxies, that means that it is so hard that not one single intelligent civilization managed to figure out a way around it, not one out of the potentially millions or billions or even trillions that may have evolved over the life of

the universe. This is important because to resolve the Family paradox, it would take just one of them to have learned how to survive the trip, to colonize the galaxy and

show us that we are not alone. And you can argue that it would really only take one, one single member of one single civilization of the potentially trillions of them to make it to Earth and make their presence known to us to have proof that we are the only intelligent life in the universe, which makes the Fermi paradox even stranger or more clearly settled, depending on your view.

The other side of that particular coin holds that other civilizations could colonize the galaxy or even the universe, they just don't want to. There are a lot of theories as to why that might be. Now it's possible we're anthropomorphizing aliens here. We humans will almost certainly colonize the galaxy if we ever get the chance to. So, perhaps we're relying too heavily on the assumption that any life would. This is the senior astronomer at the Study Institute set

show Stack. All of this, all of this is based on trying to guess, because that's really the correct verb, to guess what is important to the extraterrestrials. And I don't think that we're actually very good at that any anymore than you know, the ancient Greeks would have been very good at guessing it's important to century Americans. I don't think that they could have seen foreseen the kinds

of things that would be important to us. Perhaps the civilization develops to the point where it's technologically capable of interstellar and intergalactic travel, it loses its taste for such things. Perhaps the civilization goes philosophical and contemplative a race of beings who prefer to spend their time thinking about the meaning of life. You're solving the deepest mysteries of the

universe from home. But even the most inward focused society would have good reason for expanding from their home planet. As their population grew, they would need more and more raw materials to keep them alive while they sat around in contemplated life. It would be more space, more energy. The need for scarce resources appears to be one of the few universal commonalities that any civilization will have to

deal with. This is good. This means that we can pretty confidently use this clue to predict the behavior of any intelligen life. Then we humans run into limitations on our ability to grow or make food, so we need more space for that. We need space for our bodies as well, since each person needs somewhere around one point six one point seven meters of physical space to stand up and extend our arms with him, plus we tend

to like a little extra to move around into. Requirements like these mean we would eventually face the prospect of either systematically curtailing our population growth to maintain no more than what the Earth can support and based on all current and historical data, we tend to overstrain the planet rather than work within its confines, or we can spread out.

It's difficult to imagine that any advanced society faced with resource pressures would not look out to at least their own solar system as a source of material solutions to their problems. This scenario extends further and further, both into

space and time. As the society continued to grow, they would take up more and more space, and over long enough spans of time, they should reasonably have colonized a sizeable chunk of their galaxy, if not the whole thing, even with their desire to remain inward over so many generations. But maybe aliens have good reason to resist the urge to spread out. Maybe they're hiding from something, Maybe they

know something that we don't know. One of the long standing theories about why a civilization with the capability of traveling to other stars would opt not to is the

idea that they might be afraid of something. Perhaps there's some older civilization that doesn't like to compete for scarce resources with young upstarts like ourselves, the first civilization to have colonized the galaxy would have all the advantage over any others that came later, even considering a hundred thousand year head start, which though it's tough to remember that the cosmic time scales we're dealing with here is the blink of an eye, and earlier civilization would have time

to see the galaxy with things like berserker probes, hypothetical type of self replicating space probe designed to attack and destroy entire civilizations. These berserker probes would be capable of strangling in the cradle the colonial aspirations of any younger civilizations before they ever got started. Right about where we humans are in our progress right now. What's ironic about berserker probes is that they can produce their own solution

to the family paradox without even existing. We humans thought of the possibility that they could exist, so it stands to reason that other intelligent civilizations might too. It's possible that part of the process of the umbing and intelligent society engaged with the unknowns of the universe is to start having second thoughts about signaling into the void and instead to go silent. Eventually, every single one of these societies might stop attempting to communicate and resigned to just

sitting and listening instead. So the universe could be teeming with intelligent civilizations, each being quiet as a dormouse, each listening and unaware of the existence of the others, and the berserker probes wouldn't even have to exist beyond the hypothetical for this solution to the family paradox to work. But if berserker probes do exist, why wouldn't we have

had an unpleasant visit from them by now? Transmissions from our radio and TV shows have been traveling through space since we first started broadcasting here on Earth in the early twentieth century, and steady researchers have been actively shouting at other star systems with radio since the sixties. Probably the most unsettling answer is that we did get their attention,

and they're on their way. They just haven't had time to reach us yet, or perhaps they don't much care about us so long as we stay here on Earth

or even within our own galaxy. In two thousand and seventeen, Oxford philosophers Stuart Armstrong, Ander Samburg, and Milan Turkovich developed a new explanation for the Fami paradox that says that perhaps the universe does contain berserker probes, but rather than actively patrolling the galaxy, they are posted on the outskirts of some ancient civilizations state territory while the civilization sleeps. This new idea, called the estivation hypothesis, supposes that the

civilization in question has reached a post biological state. Post biological civilizations are their own can of worms entirely, and we'll talk about them more later on. But what they amount to is a species that has shed its biological form, whether it's an upright bipedal form like us humans, a giant root, vegetable, whatever, and has preserved its minds into a computerized form. There are myriad advantages to this. Less physical space is needed, you don't need to grow food.

But these civilizations are not free from scarcity either. Here's philosopher Ander Samberg again. So suppose you're a really advanced civilization. You've been around for millions of years, you kind of explored in the galaxies, You've done most of a big physical stuff. At this point, probably most of what you want to do is going to be kind of cultural. We have no idea as umus what an advancedivils might

want to do. But I think it's a pretty certain bet that it's going to require competitions of some kind. Information processing a k. A. Computing has its own requirements. It needs energy and it produces waste heat, two huge factors that a post biological society would come up against as it uploaded more and more of its population to

a digitized format. Rather than food, water, and couple of square meters of physical space, they would need processing power and speed to keep their digitized minds humming along and

to simulate the world for them. So a post biological society would have very good reason to colonize their galaxy in search of more raw materials to build hardware and to harness more energy from They will probably build massive engineering projects to capture energy from entire stars, like through some variation of Dicen spheres to a hypothetical energy collection machine that could be constructed around a star to capture

some enormous fraction of its energy. They may deconstruct entire planets to build those Dicen spheres, so they may have energy and aces. But at some point a post biological society might strike upon a seemingly insurmountable truth about information processing. Regardless of how efficient it is, computing produces some amount

of waste heat. This can be tricky enough with a single server him here on Earth in the early twenty one century, those racks of servers have to be cooled with fans, and the room has to be air conditioned. So that means that not only is the actual process of computing taking up energy, there's an additional energy expenditure

required to keep the hardware cool. Heat is the sworn enemy of efficient information processing, and efficient information processing would be the lifeblood in the oxygen to a healthy post biological society, So keeping heat to a minimum would be of the utmost importance. You may say, and I would

agree with you. That's certainly a post biological civilization with a hundred thousand or million or billion year head start on us would have almost certainly figured out better, more efficient, and less heat producing methods for information processing than the computers we humans have hit upon today. It would be one of the more surprising things in this whole series

if that weren't the case. But when you begin to scale up from the level of server room on word to capturing the energy of an entire star, even an almost efficient computer will still have a massive waste heat issue, and that post biological society will have to deal with it, and that problem is compounded with each new star and

each new piece of hardware that's added. Since you have a finite amount of energy, even if you're a really big supercivilization, that means that the total amount of competition you can do is going to be set by temperature. So if you wait until the universe gets colder, you

can get much more competition done. Some people have suggested that perhaps the edge of the galaxy, which butts up against the coldest regions of intergalactic space, is the best place to look for other civilizations, since they will have likely set up shot there to deal with their massive waste heat problem. But that Oxford group realized that the optimal place for a post biological society to best deal with their waste heat is somewhere in time, not space.

M One popular suggestion for the expiration data of the universe comes about ten billion thousand years from now via the heat death of the universe. Every bit of energy in the universe was released in the Big Bang some thirteen point seven billion years ago, and the ninete century we humans it upon the laws of thermodynamics, which had some bad news about that energy. Over time periods, that energy will cease as the heat differentials that produce it

begin to equalize. As every atom in the universe slowly stops moving, the universe will cool, and eventually the universe will experience the death of heat, and with the cessation of the movement of atoms and the particles that make them up, not life, not computing, nothing will be possible any longer. Long before the expiration date, the universe will still be alive with energy, but much much colder than

it is now. So particularly clever post biological society might realize that the energy they have available to them could be captured and stored for use later on, when the universe is colder and computing is, by extension far more efficient. So perhaps they built themselves a galaxy's worth of Dyson's fears to collect and store the energy from their stars while the society went to sleep for a billion or

so years. Even a peaceful post biological society would be forced to protect their energy allotment and their hardware while they slept, and so they would almost certainly post some sort of guard like berserker probes to watch over them and the civilization they'd arranged in store for themselves while they slept. Estivation is a kind of hibernation that some animals do when it's hot out, and the estivation hypothesis

goes fairly far and entering the family paradox. We haven't been colonized by other civilizations because they're sleeping, So the estivation hypothesis is that advanced civilizations might actually think that it's too sweltering hot right now, it's three degrees above absolute zero, so they decide to just hide and estivate

until it's cold enough. So in about one point five trillion years, it turns out that the universe stops getting colder because of the background radiation from the horizon, and at that point it might be rational for the super civilizision of wake up and they kind of feel the nice, crisp autumn air or in this case, the very cold vacuum of a very far future, and start really running recipilizations.

And this might be an explanation of why we're not seeing any but it doesn't fully resolve the family paradox either. We should still be able to observe their dicense fears or other massive engineering projects encircling a star with an

energy capturing devices no small feat. We should be able to sense such a thing, And indeed, the team of Japanese researchers scanned a portion of the sky to look for telltale signs of dicense fheares stars that produce a normal amount of heat but are unnaturally dim or even totally dark. They didn't find any, So it doesn't look exactly like the universe is currently full of sleeping elder civilizations looking for Disonian artifacts. These massive engineering projects is

a proposed new branch of CETI. Whether civilization is active, sleeping or extinct, the projects they created would likely endure, and if we can find those, we found our answer to the family paradox. But yet again we have found nothing of the sort. We have an uncovered one scrap of evidence the universe has ever been colonized. The Fermi paradox stands stronger than ever. But what if what we're

seeing is an actually the reality of the universe. What if we're being actively manipulated that somewhere out there the universe is indeed teeming with life, that there are widespread engineering projects that litter the galaxies. We just can't see any of it because we're being prevented from seeing things as they really are. This is the basis of a family of answers to the Family paradox called the Zoo hypothesis, thought up in nine three by m I t astronomer

John Ball. It supposes that we humans are being kept without our knowledge and some sort of cosmic zoo, and being observed, maybe even studied, without our awareness. Perhaps we're being kept in a kind of nature preserve until we reach some crucial point in our evolution when the secrets of the universe will be revealed to us. Or maybe we're meant to stay in a naturally preserved state forever.

Maybe the rest of the universe has been paved over with dicens fears, every other available planet stripped and deconstructed for materials, and out of a sense of intergalactic nostalgia, our planet and the life on it, including us, has been selected to be kept in a pristine state. The Zoo hypothesis has some holes in it too, mostly the same as any other solution to the Family paradox. It would take only one member of one civilization to shatter it.

The Zoo hypothesis presumes some sort of star Trek like prime directive to leave us alone, and it would have to be firmly upheld by all other civilizations in this galactic club, keeping us in the dark for as long as humans have been around. There are no options. The prime directive is not a matter of degrees, it is an absolute, one would think. Some people object to this

dismissal of the zoo hypothesis. They point to things like UFO sightings and historical documentation of inexplicable phenomena like the fifteen sixty one Cathedral of Light over Nuremberg, Germany. All of this is evidence of past non compliance with this prohibition on contact with us humans. It's also possible that Earth was visited in human prehistory as well, and that there's just no surviving evidence of it. Or maybe we

have received messages and just don't know it yet. Perhaps they are encoded in our DNA, waiting for us to find them and make sense of it. There is something very disconcerting about the zoo hypothesis, the idea that knowledge we would very much like to have is being kept from us without our say in the matter, through ways we may never hope to overcome on our own. But I don't know. Is that better or worse than the alternative?

Is the idea that we are being manipulated by a galactic club of civilizations better or worse than the idea that there are no other civilizations at all. There is a very reasonable alternative explanation to the Faramie paradox, one that requires us to make the fewest leaps of faith to reach it. That we are utterly and entirely alone in the universe. This is Oxford philosopher Toby Ord. There are about two hundred billion stars in our galaxy the

Milky Way. So if the chance of life or intelligent life evolving around any one of those stars was was even you know, one in a billion, you'd expect that to be about two hundred stars in our galaxy that have involved intelligent life. And yet when we look around, we see no signs of this, and we also don't see any signs of it in other galaxies um that

we have looked at. Some people think that this is a paradoxical result, but I think it's actually much more likely that the that it's just that there aren't any As Michael Hart puts it, in this Our universe is too big and too old for it not to be teeming with life by now. That we've not seen evidence of other civilizations suggests that they do not exist, but that's not to say they never did. Perhaps we don't see other intelligent civilizations because none of them have survived.

On the next episode of the End of the World with Josh Clark, the great filter is whatever is in the way, whatever makes it hard for any one piece of ordinary dead matter to produce expanding, lasting life. If we are alone in the universe, then perhaps there's something that's killed off every other civilization before it could spread from its home planet. And if that's true, can we expect the same in our future?