What is the Fermi Paradox? How rare is non-intelligent vs intelligent life? What are the challenges a species must overcome to colonize the galaxy? Where is everybody? I discuss these questions and more in today’s Ask a Spaceman!

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EPISODE TRANSCRIPTION (AUTO GENERATED)

Where is everybody? For decades, that question was merely a part of physics legend. The kind of thing grad students overhear when their advisers take them out to dinner. But the story behind that question turned out to be true, and it's a good story. It was after world war 2, and flying saucers had burst onto the scene as this huge cultural phenomenon.

And physicists are somewhat like normal people, and when they meet for lunch, they chat, and sometimes they chat about work, sometimes they chat about their family, and sometimes they chat about whatever is in the news. And Enrico Fermi, the eminent physicist of his era was visiting Los Alamos National Laboratory, and he was out to lunch. And over the course of the conversation, it moved to 2 UFOs and flying saucers. And the group ended up nerding out over the possibility of space travel. They realized that for flying saucers to actually be aliens, this had to indicate that it was possible to travel faster than the speed of light, because that was the only feasible way to travel amongst the stars in any reasonable amount of time.

And so, you know, if these are aliens, then that tells us interesting things about physics, and, you know, they're just chatting. But as the conversation went on, Enrico Fermi went silent, and he stopped contributing. And as conversations tend to do, they moved on from the UFO discussion and on to other things, but Fermi remained silent. And then sometime later, out of nowhere, he just blurted it out. Where is everybody?

Everybody immediately knew what he meant. This became the genesis of what is now known as the Fermi Paradox. And here's the basic idea. Life is possible in the universe. You need proof?

Hello. It's nice to meet you. It happened here on Earth. And the universe tends to not just do things only once. In fact, the default assumption in astronomy and cosmology is that we are not special.

We occupy no privileged position or unique status. This concept is also sometimes called the Copernican principle for Nicholas' removal of the Earth from the center of the universe. We're not special. And, you know, there's nothing about our planet that is all that remarkable. There are a lot of rocky worlds out there orbiting sun like stars.

There's a lot of water. There's a lot of carbon and, hydrogen and phosphorus, and all the ingredients that we need for life are all amongst the most common elements in the universe. Heck, we've even been able to put some preliminary estimates on the number of Earth like planets orbiting sun like stars in the Milky Way, and it's somewhere around a few billion. And so if there's nothing special about our planet, there should be nothing special about our life. Life happened here on an Earth like planet around a sun like star.

There are 5,000,000,000 other chances for the exact same thing, so there should be at least 5,000,000,000 other chances for life. By that logic, the universe should be teeming with life. And not just regular life, but intelligent life. And not just intelligent life, but space faring and even space colonizing life. Again, just look at ourselves.

We are right on the cusp of sustained presence in space in a real way. We are on the cusp of being an interplanetary and perhaps even interstellar species. It's not hard to imagine extending our technology just a little bit, and we could be one of those, I don't know, Star Trek civilizations. So if we're right here on the cusp of being able to travel amongst the stars and colonize other planets and explore the universe, then it should be common. If we could do it, then somebody else should be able to do it too.

And heck, you can imagine throwing every technological hurdle in the way. Nothing better than fusion powered rockets. You're always limited to the speed of light. Limited lifespans. Disease, warfare, apathy.

Anything that would and could slow down our progress to spreading ourselves amongst the stars. The thing is, the Milky Way galaxy is roughly 10,000,000,000 years old. And given that enormous amount of time, then space faring civilizations have had more than enough eons to essentially spread throughout the entire galaxy. We should see advanced civilizations everywhere. We're talking Dyson spheres, stellar engineering, signatures of powerful engines.

And, yeah, there are a lot of mysteries in the universe. There are a lot of cosmic explosions that we don't fully understand. There are some high energy particles filtering through the atmosphere that we atmosphere that we we can't pinpoint an origin to. And I have fun at night imagining that the next time we see, say, a gamma ray burst, it's really a death star blowing up or something. But the point is that we see no need to explain any observation in the solar system, in the galaxy, or the universe by invoking advanced alien civilizations.

Even when our natural, dead explanations, like explanations just involving normal physics, don't explain everything of which there are many mysteries in the universe. A fast radio burst, dark energy, the the the hexagon on Saturn. Even when they come up short, we find no great pressure to say that aliens did it. We see no evidence out in the wider universe of any advanced civilizations. And heck, the solar system itself should have been visited multiple times by multiple species either in person or in alien or with their robotic crap.

We should have monoliths and nanobots and space jockey skeletons everywhere, especially on the airless worlds that have maintained a record of impacts and events going back for over 4000000000 years. And yet, we see no evidence in our own backyard of any visitors whatsoever. So where is everybody? Hence, the paradox. Something in this line of reasoning has to give.

We've got one of these statements wrong, if not many of these statements wrong, if not all of these statements wrong. But which one? Now I would love to do an entire series on the Fermi and all its possible answers and what it means for current searches for life. But I'll save that for a future date, and please, if you ask more about it right now, the the sooner I'll get to it. But to slate your thirst for solving long standing puzzles in physics, we'll spend today jumping into one, just one of the possible resolutions to the Fermi Paradox, and that's the so called great filter, which sounds kinda ominous and is kinda ominous.

But as we'll see, it doesn't have to be ominous, but it just might be. Anyway, let let let me explain. Versions of the great filter argument have been around for decades just like Fermi was not the first person to ask where everybody is. But the most comprehensive form of the argument comes from Robin Hanson in 1996 who is an economist. That's right.

An economist. You might be thinking, what is an economist doing assessing the the viability of intelligent civilizations arising in the universe? I mean, but who said physicists and astronomers get to have all the fun for themselves? I mean, these are broad questions about the nature of the development of life in the universe and our perspectives for finding it. This isn't just a physics and astronomy problem.

So, yeah, economists, come on into the tent. Let's all have a big alien party. But here's the simplest possible reduction of the great filter argument. The most distilled essence of the entire chain of reasoning to explain why we don't see advanced space faring civilizations roaming the galaxy. There aren't any.

Nobody makes it. That's it. Nobody makes it to that advanced stage. Question, where is everybody? Answer, nobody's home.

In this view, Fermi's paradox is broken in the assumption that intelligent space faring civilizations are common. According to the great filter answer, they're not common at all, and so we shouldn't be surprised when we don't see anybody. But wait. Wait. Wait.

Wait. Wait. Wait. Wait. Aren't we on the cusp of achieving space colonization status?

If the great filter is true and nobody makes it to that level of sophistication, then what does it mean for us? Does it mean we're near the end of the road? Like I said, it's a little ominous. But let's break things down to see under what exact conditions things should start to feel a little spooky and where we might be able to keep our blood pressure in a nice safe range. The issue is that we don't know exactly when or where the great filter actually happens.

There are a lot of steps to go from random planet with the right ingredients for life to vast interstellar empire. For his part, old Robbie Hanson broke it down into 9 separate jumps that life requires to go from the little to the big leagues. You have to have the right star system, then you have to get reproductive molecules, Then, prokaryotic life. Then, you need eukaryotic life. Then, you need sexual reproduction.

Then, multi cellular life. Then, some vague category of intelligence like using tools or something. Then, you need an advanced civilization with the potential for colonization. And then finally, once all the pieces are in place, you can have a gigantic galaxy spanning explosion of life. So where's the bottleneck?

Is it at the beginning, with life ready systems hard to come by? Is it somewhere in the middle where life never gets a start or just spends 1,000,000,000 of years swimming around in oceans? Or is it towards the latter stages? And considering that we are near the very last stage, that's where the anxiety start to set in. So we'd really like to settle this answer please.

Now I know, there is an obvious bias in this argument. That life across the galaxy follows a similar path to us, which may or may not be true. I will dig into this more once I do a full series on the Fermi Paradox, but in brief, if we expand our definition of life, that makes Fermi Paradox even worse. Because if there are more avenues for intelligent species to arise in the universe, not just our pathway, but other pathways available, then there should be even more evidence for life in the universe. There should be even more intelligent space faring civilizations, not fewer.

So let's stick with this restriction because it's the most compatible with solutions to Fermi's paradox. And we'll we'll pick it up later when I do a full series on it. So let's look at the stages. Let's see where the great filter could come into play. Let's look at say, stage 1.

The conditions for life to arise in the first place. Maybe maybe the filter is there. Maybe the conditions for life are exceedingly rare. Well, it it honestly doesn't look like that's where the filter is. And that's because we see a lot of the ingredients for life spread throughout the universe.

We see a lot of the building blocks of life spread throughout the universe. We can look at molecular clouds that have amino acids in them just naturally spontaneously forming. We see water rich worlds everywhere. Not just the Earth, but the subsurface oceans of Europa and Enceladus and all of them. It seems like the ingredients for life in the places where life could get a start are numerous.

Heck, even the terrestrial worlds of the solar system. We know Mars had all the right conditions for life 1000000000 of years ago, and there's a solid chance that Venus did too. So 1000000000 of years ago, we had 3 places in our solar system that looked a lot like the earth. Okay. It doesn't look like stage 1 is going to be the filter, because it looks like there are a lot of potential sites where life can get a start.

What about stage 2 to 3? You know, the bits about self reproducing molecules and single celled organisms. Well, we don't have much to go on here. We have one single planet where this we know where we know this happened, but it's still a data point. And the data we can mine from the Earth is that life appeared as soon as possible.

And as soon as life did appear, it started contributing to Patreon. That's patreon.com/pmsutter, p m s u t t e r. You'll also find a link in the show notes. It's how you can keep this show going and even unicellular prokaryotic life at the dawn of the history of the Earth was already signing up to Patreon to support the show. So if it could do it, I think you can too.

And I do truly do appreciate all of your contributions. But the real truth is pretty much as life could appear on the Earth, pretty much as soon as conditions were even marginally possible to support life on Earth, we have evidence for life on Earth. So if we are forced to guess and this is only a guess, then a halfway decent reasonable guess is that the filter is not in the earliest stages. That if life has the right conditions, it probably shows up right away. Again, I'm emphasizing that is a guess.

But it's a guess based on the only data point we have available to us which is that life showed up right away. Okay. What about the middle stages? You know, the march from single celled organism doing their single celled things to intelligent creatures that can wield tools and leave feedback reviews about them. Again, we still only have one data point, but we might be able to learn something about those filters from this one data point.

Looking at the history of the Earth And assuming that it's a typical scenario that the okay. Earth like planets are pretty common. Check. As soon as the conditions were right, life appeared. Check.

No filters there. But intelligent life took a very very long time to appear on the Earth. 1000000000 of years of evolution with a lot of setbacks, a lot of evolution, a lot of catastrophes, a lot of volcanoes, a lot of rocks falling from space, the usual. It took a long time. And in fact, we, us, humanity, intelligent humanity appeared on the earth pretty much as late as it possibly could.

And that's because the clock is ticking on the earth. Yes. The sun is only midway through its life. It's only 4 and a half 1000000000 years old. It's got another foreign change left to go.

But as it ages, it steadily gets hotter and brighter. And in less than 500000000 years, the sun will be too bright. It will be too hot. Our atmosphere will evaporate. Our oceans will boil.

And we're going to turn into another Venus in only a few 100000000 years. So if you look at that span of time that the Earth could possibly host life, life itself appeared within a few 100000000 years, and intelligent life only appeared with a few 100000000 years left to go. So based on this one data point, which is not a lot, but, you know, that's all we get, at least so far, it looks like there might be a filter right in those middle stages where life is common in the universe, but intelligent life is not. Where Earth like planets are common, life appears pretty much anytime they gain a foothold, but the march to intelligence is special and rare, and that's where the filter is. We can't exactly test this.

That's a pretty strong word for the ideas we're putting out here, but we could at least start to wrap these questions and responses in some sort of statistics or probabilities, which is if we continue our searches for life, if we dig through the ice of Europa, if we examine the atmospheres of our neighbor planets and other star systems, if we find evidence for simple life but no sign of intelligence, then that might be a clue that this filter idea is a reasonable answer to Fermi's paradox, and that the filter happens on the march to intelligence, where life is common in the universe, but intelligent life is rare. And so we shouldn't expect to see space faring civilizations because it's really, really, really, really hard to make intelligent beings in the first place. But like I said, these are all guesses. We only have our one data point. Let's keep going.

What if simple life is easy and common? And what if intelligence is easy and common? What if the march to intelligence isn't as hard as it seems and just on the Earth, it took a few 1000000000 years because we had a few strokes of bad luck? But if you go to some other random Earth like planet, there are intelligent beings on those worlds in general. What if the filter is at the last step?

That reaching galaxy spanning super spreaders is hard. Well, maybe species simply destroy themselves. I mean, it's not hard once you put your mind to it. The idea is that interstellar travel, or even interplanetary travel, requires the ability to harvest, store, and use incredible amounts of energy. And you need to develop a sophisticated technological base to do all that.

And if you can do that, if you can harvest and store and use more than enough energy to travel to other planets or other stars, then you can harvest, store, and use more than enough energy to wipe every single living thing off the face of your home planet. It's not a coincidence that we developed nuclear weapons and are facing climate change at the same time that we can launch rockets into space and send probes throughout the solar system. That's not a coincidence. Both require harnessing incredible amounts of energy and having sophisticated technology, and you can't have one without the other. You can't have the benefits of space travel without the risk that that kind of technology brings.

The best insurance against self annihilation is to have your favorite kind of living thing on multiple surfaces on multiple planets. But that takes time, centuries, maybe millennia. And in that time, as you are spreading yourself to your neighbor planets, maybe your natural satellites, and then maybe to other stars. In that time, you are facing a precarious balance because you're trying to climb a ladder to the stars where you can preserve your species on multiple planets, have multiple backup options, but that requires using so much energy, and that energy can be used for nefarious purposes. So in that climb to the stars, you're trying not to cut yourself off at the knees.

And that's, like, that's us. We can send robotic craft beyond the edges of the solar system. We can send crews to live months at a time in orbit, and we can also wipe every living thing off the face of the earth. We have more than enough nuclear weapons to kill off all of humanity and then some. And if we pump enough carbon into the atmosphere, things can go haywire real quick and have the same effect.

So yeah. Maybe intelligent species are common, but they just kill themselves. Or maybe they don't kill themselves. Maybe maybe the march to intelligence takes so long that nature does the job for us. And that here we are intelligent, and as we're building out the capabilities to become a space, faring civilization, maybe nature sends an unlucky rock in our direction or an ozone killing blast from a gamma ray burst.

Maybe it just takes so long that nature does the job. And remember, for the great filter argument to work, it has to be near total which means this is it. This is the end of the line. The last stop before galactic extinction. Goodbye everyone.

Hug your loved ones. Take that one last bite of cheese because the end of our species is right around the corner. Whether we do it ourselves or nature does it for us, this is it. You get to taste space. You get a little taste, but then your species is gonna die.

I've ended some other episodes on real downer notes, and I refuse to do that here. There are other less stressful options. First off, remember that the great filter might be earlier, and we're already on the other side of it. We're one of the lucky few that make it even to this level of intelligence. So we're done.

We pass the filter. And and the galaxy is ours for the taking. Or remember that the great filter isn't about absolutes. It's about probabilities. It's about saying that space faring civilizations are so rare that we shouldn't expect to see anybody.

It doesn't mean it's impossible. The great filter might be here. It might be on this cusp of space faring status, where we have advanced technologies and harness incredible energies, but that also pose a risk to ourselves. It could be here, but it's not guaranteed. We might get lucky.

We still got a chance. Or maybe the assumption about intelligence leading to a space colonizing galaxy spanning civilization is wrong. Maybe galactic colonization is harder than we think. Maybe we don't see anybody because, it's it's really really hard. And you can be super advanced, unlock all the mysteries of physics, but you can't get around the speed of light.

And you can't get around the energy requirements. And you end up spreading to, like, your nearest few stars, and then that's it. And then you're happy. Maybe space colonization is boring. We're all interested in it right now, but maybe a 1000 years from now, we won't be so interested in it.

Maybe our culture will move on. And and then not just cultural norms, but maybe progress. Technological development is not linear. Maybe we'll develop in less imperial directions. Maybe we'll pour our time and effort not into rockets and space habitats but but something else that makes our lives richer.

And maybe everyone does it. Maybe they're just cultural and technological avenues that are are much more promising and much more fulfilling to any intelligent species. And maybe we don't bomb ourselves into oblivion, but just into the stone age where we're still around, still intelligent, but just right here. Maybe climate change gets so out of control that we're forced to spend all of our energy dealing with that, and and we never make it to the stars. Maybe the great filter is a little bit softer where it confines intelligent species to their home planets or their home systems, but doesn't necessarily obliterate them.

All of these would fit the great filter, especially if they work in combination where you have the conditions for life appearing all throughout the galaxy super common. You have life itself super common throughout the galaxy. You even have intelligent life throughout the galaxy. But that intelligent life doesn't spread, doesn't make itself really obvious, just just hangs out, chills at home. That would fit the great filter because Fermi's question was where is everybody?

Maybe they're home, but we just don't see them. Maybe we're not on the brink of total annihilation because there are other options available for our future. So maybe we're all good. But seriously, where is everybody? Thank you to Snap Planet for the question that led to today's episode.

Please keep those questions coming. That's askaspaceman@gmail.com or the website, askaspaceman.com. And please keep those reviews coming in on your favorite podcasting platform. It really helps the show visibility. I truly do appreciate it.

And, of course, I cannot thank you enough for all of your generous contributions on patreon. That's patreon.com/pmsutter. I'd like to thank the top contributors this month. They're Justin g, Chris l, Alberto m, Duncan m, Corey d, Robert b, Nyla, Sam r, John s, Joshua Scott m, Rob h, Scott m, Lewis m, John w, Alexis Gilbert m, Rob w, Jessica m, Jules r, Mike g, Jim l, David s, Scott r, Heather, Mike, s, Pete, h, Seves, Watt, Watt, Bird, Lisa, R, Koozie, Kevin, b, Michael, b, and Eileen g. I truly appreciate everything that you do to make this show possible, and I will see you next time for more complete knowledge of time and space.

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