The Harsh Math of Finding Life in the Galaxy

Welcome to Bedtime Astronomy. Explore the wonders of the cosmos with our soothing Bedtime Astronomie podcast. Each episode offers a gentle journey through the stars, planets, and beyond, perfect for unwinding after a long day. Let's travel through the mysteries of the universe as you drift off into a peaceful slumber under the night sky.

Are we alone in the universe? I mean, it's a huge question, isn't it something humans have probably asked forever looking up at the night sky.

Absolutely, it taps into something really fundamental about our place in the cosmos.

For so long it felt, you know, purely philosophical or maybe just science fiction fodder. But it seems like actual scientific research is starting to weigh in, maybe giving us a more well, a more precise answer.

That's right. Recent studies are trying to model the probabilities based on what we know about planets, stars, and life itself.

Sure that's emerging is maybe a bit surprising, Perhaps not the crowded galaxy we sometimes imagine.

It certainly suggests the odds might be steeper than we thought, especially for technological civilizations like ours.

Okay, so that's what we're exploring today. We're going to look at some really fascinating findings about well, the incredible odds stacked against finding other technological civilizations just in our own galaxy, the Milky Way.

Yeah, looking at the specific conditions needed, the planetary set up, the atmosphere, and the.

Time scales, almost unimaginable amounts of time involved for life not just to appear, but to get to a technological stage.

Exactly. It's a multi layered challenge.

So get ready because our discussion today might just shift how you think about those little lights in the sky. We'll touch on how rare, how incredibly far away, and maybe how astonishingly old any cosmic neighbors might actually be.

It puts things in perspective.

Okay, let's unpack this. Then. We've all seen the movies, right, Star Trek, Star Wars, alien civilizations just jump away. But when we talk about actually finding another civilization, what kind of distances, what kind of time scales are we really up against? According to this new.

Research, well, the scale is the first major hurdle. The reality based on these models is far more daunting than fiction suggests. Right, And it's not just the distance, although that's enormous. What's really fascinating or maybe sobering, is how the sheer scale of space and time compound the challenge as well. It's not enough to just find life or

Ah Okay, So they can't be long gone, and they can't be millions of years in the future. They have to overlap with our tiny window of technological.

Existence precisely, and that is a huge constraint. So when we delve into the numbers from recent studies, well they give us some estimates.

Let's hear them.

Okay. So the estimate for the closest technol logical species to us in the entire Milky Way galaxy could be as far as thirty three thousand light years away.

Thirty three thousand light years.

Thirty three thousand light years.

Wow, Okay. Put that in perspective for us, how far is that really?

Well, think about this. Our own solar system is roughly twenty seven thousand light years from the center of the Milky Way. Okay, So thirty three thousand light years means well, it means our nearest technological neighbors could easily be on the other side of the galaxy from us.

The other side, so not just a different neighborhood, but a whole different continent cosmically.

Speaking, exactly. Imagine trying to shout across a continent and hoping someone hears you. Now, not ten thousand years ago. Light itself takes thirty three thousand years to make that journey, So.

Any signal we send takes that long to get there, and any signal they send takes that long get here. Communication isn't exactly.

Real time, not even close. It's profoundly ancient by the time it arrives. It really paints a picture of potentially extreme isolation even within our own galaxy.

Okay, thirty three thousand light years that distance alone is mind boggling. But then you mentioned this concurrency thing. They have to be there, now, how does that layer on top?

Ah, That's where it gets even trickier, because for a civilization to exist at the same time as us, even across that vast distance, it needs to be incredibly long lived.

Right, because they had to start existing long enough ago for their light or signals to reach us now, and they have to still be existing exactly.

And this research, using planetary models and astrophysical data, tries to estimate how long lived they'd need to be. The minimum suggested survival time is two hundred and eighty thousand years.

Two hundred and eighty thousand years minimum minimum, and potentially millions of years millions. Yeah, for a technological civilization to survive.

Yes, think about what that implies. A species evolves intelligence, develops technology, and then manages to sustain itself at society, it's technology for hundreds of thousands, maybe millions of years.

To us, Yeah, I mean how long we've been technological? A few centuries since the Industrial Revolution, maybe a few millennia with writing in.

Cities, it's a blink of an eye. In comparison, to imagine a civilization lasting for say two hundred and eighty thousand years or ten million years requires contemplating a level of stability, resilience, resource management, problem solving on a scale we can barely conceive of.

It suggests they would have had to overcome challenges we haven't even faced yet or are maybe facing right now.

Precisely, it's not just about finding life. It's about finding a civilization that has somehow mastered long term survival against cosmic and potentially self inflicted threats. Well, it's a profound constraint.

So it really hammers home that this isn't just a spatial search looking for a needle in a cosmic haystack. It's also a temporal one, a needle that might have existed ages ago, or might exist ages from now, or as maybe on the completely other side of the haystack right now, but has to have been there for an incredibly long time.

That's a good way to put it. Concurrent exists is the key, and it demands exceptional longevity.

Okay, so let's zoom in a bit. Forget the vast distances in times for a moment. What about the place itself? The planet? What makes a planet even capable of hosting such a long lived civilization. It can't just be any random planet, surely, what's the recipe?

No, absolutely not, and you've hit on the next crucial layer. It's far more than just say, having liquid water, although that's generally considered essential, right.

The fall of the water approach.

Yeah, but this research we're exploring today really emphasizes the strong odds against finding truly earth like worlds capable of supporting complex technological life over billions of years. It boils down to a few critical, interconnected factors.

Like a cosmic recipe, where everything has to be just right.

Exactly, perfect measurements, perfect temperatures, perfect chemistry, all sustained for geological ages. Let's look at some of those key ingredients, starting with something quite fundamental to Earth.

Okay, plate tectonics, plate techtics like earthquakes in volcanoes. How does that relate to alien life.

Well, we tend to see the surface effects the dramatic stuff. But plate tectonics, the slow movement of continental plates, is actually vital for regulating Earth's long term climate. It acts like a planetary thermostat the thermosat. How it's mainly through its role in the carbon silicate cycle. Basically CO two in the atmosphere dissolves in rain water, making it slightly acidic. This rain whethers silicate rocks on land, washing dissolved carbon

So it pulls CO two out of the air over time.

Yes, But then plate tectonics comes in through subduction where one plate slides under another. These carbon rich sediments get dragged down into the earth mantle over millions of years. The heat and pressure release. It's the CO two which eventually comes back out into the atmosphere through volcanic eruptions.

Ah. So it recycles the carbon, It pulls it out when there's too much, releases it when there's too little.

Exactly, it's this incredibly slow but effective feedback loop. It prevents Earth from getting stuck in a runaway greenhouse like Venus, or freezing over completely like Mars might have done. It keeps a climate relatively stable over hundreds of millions of years, which is crucial for complex life to evolve.

Wow. So plate tectonics isn't just about geology, it's about long term habitability. But you mentioned even with this system there's a potential problem a ticking clock.

Yeah, that's the intriguing part. It's a great system, but it might not be perfectly balanced forever over very long time scales. There seems to be a natural tendency for more CO two to get locked away in rocks, then gets recycled back out through volcanism.

Like a slow leak in the system.

Kind of Yeah, a slow geological sequestration of CO two, And this leads to an inherent ticking clock on planetary habitability, at least for life like ours. Oh so well on Earth. The projection suggests that because of this slow depletion, atmospheric CO two levels will eventually drop too low for photosynthesis as we know it to continue efficiently.

Photosynthesis will stop the basis of most of our food chain eventually.

Yes, the estimates vary, but it could be somewhere between say two hundred million and maybe up to a billion years from now. Doctor Scherf, one of the researchers we're drawing on, puts it bluntly. At some point enough carbon dioxide will be drawn from the atmosphere so that photosynthesis will stop working.

Wow, So the planet's own life support system had that kind of built in expiry date for complex life.

For oxygen producing photosynthesis. It seems so, And this has huge implications for finding et well. If a planet doesn't have clate tectonics to regulate CO two in the first place, it might become uninhabitable much faster, or even if it does, like Earth, maybe this CO two depletion clock runs faster

So you need the geology, the thermostat. Yeah, but even then the fuel for life, the CO two slowly runs out. That really emphasizes the fragility. Okay, So the geology sets the stage, regulates the climate. But what about the air itself, the atmospheric mix.

Right, because even with the right temperature regulation, the specific composition of the atmosphere is absolutely critical, not just for life to exist, but for its complexity and its potential for technology.

Okay, Earth's atmosphere is mostly nitrogen, then oxygen, tiny bit of CO two.

Yep, about seventy eight percent nitrogen twenty one percent oxygen, and that crucial tiny fraction of CO two around point zero four two percent, which keeps us warm via the greenhouse effect.

But that CO two level is delicate, right.

Extremely delicate. Too much CO two and a planet overheats think venus a runaway greenhouse effect, ocean's boiled away surface hot enough to melt lead. Or maybe the atmosphere just becomes too dense and toxic for familiar life into little too little, and the planet freezes. It can't retain enough heat from its star, so you need that sweet spot.

So the research looked at different CO two levels.

It did, and interestingly, it explored a scenario where a planet might have more CO two than Earth but could still be habitable for longer.

How would that work? Wouldn't it overheat?

Not necessarily if other factors compensate. The model suggest a planet with say ten percent carbon dioxide much higher than Earth's, could potentially maintain its biosphere its capacity for life for a staggering four point two billion years.

Longer than Earth's projected habitable lifestam.

Potentially, yes, but there's a catch, always a catch, right to avoid a runaway greenhouse with that much CO two, the planet would need to be significantly farther away from its star than Earth is from the Sun, or its star would need to be dimmer younger. Perhaps the extra CO two provides a thicker blanket, so you need less heat from the star.

Okay, so location, location, location matters MATT precisely to the atmospheric CO two exactly.

In contrast that ten percent CO two scenario with one having just one percent CO two, that planet's biosphere might only last a maximum of three point one billion years before CO two depletion becomes critical. So the initial amount of CO two interacting with the planet's geology and its distance from the star sets a fundamental limit on how long complex life might have to evolve.

It's such a fine tune system geology, atmosphere, orbit. Yeah, I'll have to align perfectly. Okay, Well you mentioned oxygen two. Obviously we needed to breathe. How does that factor into the technology side? Ah?

Yes, Oxygen is fascinating because it's not just about respiration for complex animals, which definitely need higher oxygen levels than microbes. It's about something even more fundamental for technology. Fire. Fire studies show that if the oxygen concentration in an atmosphere drops blow about eighteen percent, you can't have open air combustion.

We really like a match wouldn't.

Light exactly, A match wouldn't light, Wood wouldn't burn reliably in the open air. You couldn't sustain a camp fire, let alone the intense heat needed for things like smelting metal in.

A furnace, and without fire.

Without fire, the path to technology as we know it hits a dead end very early on. Think about it. The Bronze Age, the Iron age. They fundamentally depended on harnessing fire to extract metals from ore and forge them into tools, weapons, structures, metalworking, no metalworking, no steam engines, later on, no complex machinery, probably no advanced chemistry. It's hard to even imagine building a radio telescope or a spacecraft without the foundational technology that fire enabled.

So you need enough oxygen not just to breathe, but specifically above that eighteen percent threshold to even get basic metallurgy off the ground, which seems like a prerequisite for any advanced attack.

Precisely, it's another critical bottleneck. The atmosphere needs enough oxygen for complex life and enough for the key tool that unlocks advanced material science.

Fire. So let me see you've got this straight. We need a planet with plate tectonics for long term climate stability. We need a very specific CO two level balanced with its distance from the star to keep temperatures right and sustain photosynthesis for potentially billions of years, and we need oxygen levels high enough, probably over eighteen percent, not just for complex animals, but crucially for fire enabling metallurgy and technology.

That sums it up pretty well. It's an incredibly specific and likely quite fragile set of circumstances.

It really makes Earth feel well, exceptionally fortunate, almost impossibly so. Okay, so, even if a planet somehow wins this incredible cosmic lottery and has all these conditions aligned, what's the next big hurdle for a technological civilization to actually be detectable bias?

Well, winning the planetary lottery is just stage one. Stage two is time, specifically the enormous amount of time it takes for technological life to evolve in the first place, and then crucially, the time it manages to persist. Persist you mean survive, survive, Yes, survive itself, survive cosmic accidents, survive for long enough to own relap with us.

Okay, how long did it take here on Earth?

Well, our planet is about four point five billion years old, and technological life really only emerged in the last tiny fraction of that time, so it took roughly four point five billion years of evolution through countless steps in stages.

That's a huge amount of time.

It is. Think of the milestones the origin of life itself from non life that's a biogenesis, than the evolution of photosynthesis, which changed the whole atmosphere. Then the leap to multicellular life from single cells, then complex animals, nervous systems, intelligence tool use. Each step took hundreds of millions, sometimes billions of years, and there's.

No guarantee that sequence happens everywhere, or it takes the same amount of time absolutely not, which brings us to longevity. The longer technological species manages to survive after it develops technology, the greater the chance it exists at the same time as another civilization like us. This is where that idea of the great filter often comes up, the idea that there are these huge hurdle's life to overcome.

Exactly maybe the filter is behind us, like the origin of life or complex cells, meaning life itself is rare, or maybe the filter is ahead of us, meaning that becoming technological is relatively easy, but surviving with technology for a long time is extremely hard.

And this research suggests the survival part is key very key.

The calculations done by Shurf and Lammer really drive this home. Remember that planet with ten percent CO two potentially habitable for four point two billion years.

Yeah, the one farther from its star.

Right Even on such a potentially long lasting habitable world, for there to be just one other technological civilization in the Milky Way at the same time as us, that civilization would need to have survived on average for at least two hundred and eighty thousand years just for.

One other civilization to exist concurrently.

Yes, minimum average life span two hundred eighty thousand years. Think about that, maintaining stability, avoiding self destruction, managing resources, weather in cosmic storms for over a quarter of a million year.

That puts our few centuries of industrial society into perspective chromatically.

So, and it gets even more stark if you hope for more neighbors. How So, for there to be say, ten technological civilizations existing concurrently in the galaxy right now, the calculation suggests the average lifetime of each one needs to be over ten million years ten million years average average. As doctor Scherf noted, the number of potential alien civilizations

Ten million years. I can barely imagine what human society might look like in ten thousand years, let alone ten million.

That get well, it suggests any civilization we do find is almost certain to be vastly older than us.

That's a very strong implication of these numbers. Yes, yeah, they wouldn't likely be newcomers to the technological stage. They'd be the survivors, the ones who figured out how to last for time, skills that are frankly geological. That's a truly staggering thought. Not just aliens, but ancient aliens who've mastered longevity. It highlights this potential fragility. Maybe the immense challenge of surviving your own technological advancement. Maybe that's the great filter.

It's certainly a possibility that many researchers consider the challenge might not be intelligence, but wisdom and sustainability.

Okay, these numbers, these conditions, they paint a compelling picture. Thirty three thousand light years away, needing to survive for maybe millions of years on a planet with incredibly specific geology and atmosphere. It makes technological life seem remarkably improbable, but science is always learning, right. How solid are these figures are their big unknowns, That's a.

Really important point, and the researchers themselves are very clear about this. These numbers thirty three thousand light years, two hundred and eighty thousand years minimum survival, the atmospheric thresholds based on our current best understanding of astrophysics, minitary science, geology, biology. There are robust estimates based on today's knowledge.

But not absolute certainties.

Definitely not absolutes. There are inherent uncertainties in the models, and new discoveries, especially about exoplanets and Earth's own deep history, are constantly refining our understanding. Think of these as the best most informed calculations we can make now.

And are there factors that just aren't in the calculation yet, things we don't know enough about precisely?

The research explicitly acknowledges several huge factors that ideally should be included, but we simply can't quantify them reliably at the moment. They remain major unknowns. Genuine cosmic mysteries like what. Well, probably the biggest one is the origin of life itself a biogenesis. How does non living matter become living? How often does that happen? Even if conditions are perfect? We only have Earth as an example. Was it a near

If starting life is super rare, then even perfect planets might stay empty exactly.

Then there's the origin of photosynthesis, specifically oxygen producing photosynthesis. It terrorformed our planet, paving the way for complex life. How likely is that specific biochemical pathway to evolve? Are there other ways complex ecosystems can be powered? Another big unknown?

Okay, what else?

The origin of multicellular life? Earth had only single celled life for what maybe three billion years?

The leap to.

Complex, coordinated multicellular organisms like plants and animals was a huge step. Maybe another major bottleneck. How often does that happen?

Hmmm? The true life existed for ages before it got big.

And then even if you get complex intelligent life, there's the frequency with which intelligence develops. Technology of the kind we could detect, think radio waves, large structures, atmospheric modification. Is that an inevitable path for intelligence or just one possibility. Maybe other intelligent species focus inward or develop in ways we wouldn't recognize technology.

So maybe intelligence doesn't always lead to radio telescopes.

Maybe not. So you have these massive unknowns at biogenesis, photosynthesis, multicellularity, the intelligence to technology leap, and how you view the probability of each of those steps really shapes your outlook.

How so, Well, if you're an.

Optimist, you might think each of those steps is actually fairly probable given the right conditions. If life starts easily, if photosynthesis is a common evolutionary solution, if multicellularity isn't that hard, and if intelligence naturally leads to technology, then maybe technological civilizations aren't quite as rare as the current planetary and longevity models alone suggest.

Okay, that's the optimistic take.

Right, But if you're a pessimist, or perhaps just more cautious, you might think each one of those steps is incredibly difficult, a major hurdle with a very low probability. If any of them are near impossible, then the already loan numbers we've discussed could plummet even further. We could be effectively unique or one of a vanishing a small number.

It's like a chain, and if any link has a very low chance of forming, the whole chain becomes improbable.

That's a good analogy. We're looking at this incredibly complex equation and some of the key variables, well, there's still question marks. It gives us a framework, a powerful one, but highlights how much we still have to discover.

Yeah, it really underscores that science is a process. We have these amazing tools, these models, but the universe still holds on to some of its biggest secrets. Okay, So wrapping this up our discussion today, looking at this scientific analysis paints a really thought provoking picture, doesn't it.

It really does.

Technological alien life likely very rare, very far away, possibly incredibly ancient, all because of this precise, maybe fragile combination of planetary conditions, atmospheric balances, and the sheer difficulty of surviving for immense stretches of evolutionary and civilizational time.

That seems to be the direction the evidence is pointing. Yes, a more constrained, perhaps quieter universe than we might have hoped for.

It could feel a bit lonely that.

Perspective and yet despite these odds, despite the potentially low numbers, the researchers driving this, like doctor Shirf, are adamant about one thing that the search must go on. His stance is clear. Although technological extraterrestrial intelligences might be rare, there is only one way to really find out, and that is by searching for it.

So the low probability doesn't mean we stop looking.

Absolutely not. The scientific imperative remains because think about the outcomes. Okay, if we keep searching with better telescopes, better techniques and we find nothing, well, that silence becomes data. It strengthens the case for rarity, It sharpens our understanding of the specific conditions needed for life like ours, and it underscores our own potential uniqueness. That in itself is a profound scientific insight.

Finding nothing tells us something important exactly.

But if if we search and we do find something thing, a clear, verifiable signal evidence of another technological mind.

Out there, that would change everything.

It would arguably be the single biggest scientific breakthrough in human history. We would know, finally, definitively that we are not alone. It would reshape our understanding of biology, of cosmology, of our own place in the universe forever.

So the search is worthwhile, regardless of the outcome. Find nothing we learn about rarity, find something we learn We're not alone.

That's the beauty of the scientific quest.

So what does this all mean for you? Listening right now? Next time you look up at the stars. Does thinking about these odds, this potential rarity, make the universe feel I don't know, emptier well perhaps, Or does it make our own existence here on Earth feel even more extraordinary, like we won an unbelievable cosmic lottery? Does it highlight the sheer improbability, the incredible chain of events planetary atmospheric evolutionary that had to happen just right for us to be here.

Having this conversation, it's certainly gives you a different perspective on Earth.

Maybe the most profound takeaway isn't just about searching for them, but about appreciating us, appreciating the astonishing, perhaps fragile reality of our own technological civilization, and maybe just maybe realizing the immense value we should place on ensuring its continued existence.

Something to think about the passa

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