Today I'm talking about the Fermi Paradox in my astro-for-physics-majors class (and I'll talk about it again on Friday in my astro 101 class).
It's a really simple question with completely terrifying/mind-blowing implications, first asked by Enrico Fermi (who, ironically, was one of the Manhattan project scientists...)
Our universe is 13.8 billion years old, our Galaxy is at least 10 billion years old, other planets are surely much older than Earth, with more time to involve intelligent life.
"So where is everybody?"
A few possibilities for how to resolve the paradox. I'm going to list them all and put a poll at the end of this thread so you can vote for your favourite!
1. We are alone. We are the first intelligent life that has ever evolved in the Universe.
(Generally in astronomy any explanation that requires us to be special is a bad one. Then again, we are here asking this question, which is kind of the mother of all observation biases)
2. There are other civilizations out there, but they don't travel. This could be because it's just too hard (our furthest probe has traveled something like 0.004% of the distance to the closest star). Or maybe the drive to explore/colonize is a human trait and other intelligent life wouldn't have that drive.
2.b The absolutely most depressing option: there are other civilizations, but technologically advanced civilizations just don't last very long, so the chances that we'd overlap with another civilization nearby and notice their presence is super unlikely.
3. A galactic civilization exists! But they are avoiding us, either because we're morally reprehensible, or because we're in a kind of "wildlife preserve" (though I find these ideas pretty weirdly human-centric...)
4. The only civilizations that survive long-term are the ones that realize that exponential growth is unsustainable, and completely reorient to a lower-energy state. This would make them undetectable to us.
(I talked about this idea, called "Homeostatic awakening," a few days ago, with lots of interesting comments: https://mastodon.social/@sundogplanets/111478947136600731)
Which resolution to the Fermi Paradox do you think is best?
@sundogplanets It's interesting to read Sci Fi author and astrophysicist Alastair Reynolds address this in his novels.
Does Drake's number come next?
@sundogplanets
Civilisations are too far apart.
@Nick_Stevens_graphics @sundogplanets if colonization is possible, they wouldn't stay far apart. How fast could an interstellar civilzation spread in a million years? 10 million? A billion? This is geometric growth. There was a time when COVID-19 was "too far away" until it wasn't.
@Pxtl @Nick_Stevens_graphics @sundogplanets
That's a very very big if.
We are close to the peak of our usable resource stream right now, and not even one human has stepped on another planet. Our hope is we dramatically reduce our resource consumption and waste enough to mitigate the climate emergency enough that civilization more or less survives, but reducing emissions 90%, which means cutting 2/3 of today's energy sources, isn't going to leave much for rockets.
1/
@Pxtl @Nick_Stevens_graphics @sundogplanets Setting up a self-sustaining colony even on Mars would cost quadrillions of dollars and take a century. Almost every industrial process today expects infinite amounts of free air and large amounts of very cheap water; all would have to be reinvented. Simply making a computer chip requires hundreds of different chemicals at high or extremely high purities. It's not even clear all these resources exist on Mars.
@Pxtl @Nick_Stevens_graphics @sundogplanets So you've got the whole world cooperating and spend 10% of the world's GDP every year for decades and what do you get sometime after 2100?
A freezing cold, arid, airless, dark, poisonous, radioactive desert with people living under domes.
No place on Earth outside an active volcano is so inimical to life. Antarctica has air and water, is much warmer, and the storms are made of frozen water, not fine and abrasive sand.
3/
@Pxtl @Nick_Stevens_graphics @sundogplanets What sane person would inflict this miserable life on themselves? And what about their kids? To tell a kid that he can never swim in the ocean or walk in a forest, how would that go?
"It's OK, Dad, I love this life of endless discipline against the outside world that would kill us in an instant if we stop paying attention for even one second. Now back to my exciting job in the water mines!"
4/
@Pxtl @Nick_Stevens_graphics @sundogplanets
I have followed the space program since I was a small boy, before we landed on the moon. The first non-picture book I read was Heinlein's "Between Planets" (I figured out years later, when I ran into the word "Geiger counter" again).
But here we are half a century later, and progress in space has been extremely slow, and progress on exhausting our resources incredibly fast.
5/
@Pxtl @Nick_Stevens_graphics @sundogplanets
If we as a species aren't going to spend the tens or hundreds of trillions it would take to stabilize our biosphere where all of us live now, it seems inconceivable that we'll spend orders of magnitude more to conquer this truly miserable territory of Mars where perhaps 1% of 1% of humans will live.
Is it that humans are uniquely unlucky? Very hard to tell but it doesn't seem that way.
6/
@Pxtl @Nick_Stevens_graphics @sundogplanets In particular, in terms of technology, we not only have generous helpings of literally every natural element on the periodic table, but astonishingly, this tremendous windfall in the form of fossil fuels.
Fossil fuels represent money left on the table from hundreds of millions of years ago. With all that waste energy, eventually organisms evolved to consume lignite, so new coal and oil will not be formed in future.
7/
@Pxtl @Nick_Stevens_graphics @sundogplanets
So our planet as we found it, aside from being hospitable to life, independently had every natural element including generous amounts of metals, and on top of that, a huge source of obvious energy easy to extract, based on an evolutionary accident.
The economics for us are impossible by orders of magnitude. I can't imagine it would be so much better for other creatures as to make it possible.
/thread
@TomSwirly @Nick_Stevens_graphics @sundogplanets
Forget Mars.
If we're talking about Fermi Paradox, it's about interstellar travel/colonization. So we send out 100 interstellar probes on century-long journeys to 100 stars, 1 finds a planet with liquid water and CO2-rich atmosphere and drops some oxygen-making algae into the oceans and phones home. 400 years later a slowboat full of corpsicle settlers arrives.
The Question: is the slowboat full of corpsicle settlers possible?
@Pxtl @Nick_Stevens_graphics @sundogplanets
Mars is impossibly expensive - but your plan is orders of magnitude more expensive.
The idea that you could create algae to grow in an environment you've never seen is unreasonable.
On Earth, this took tens of millions of years, and algae only got us to about 10% of the oxygen we had today.
If we can't collaborate as a species for 50 years to save our planet, will we complete this 500 year plan?
No, it is not possible.
@TomSwirly @Pxtl @Nick_Stevens_graphics @sundogplanets Inhumane interests in charge since then. As always, Western Enlightenment goes too far!
@Pxtl @Nick_Stevens_graphics @sundogplanets
"This is geometric growth."
Would it be? Or would the civilization start in-fighting as soon as several star systems are colonized?
@csstrowbridge @Nick_Stevens_graphics @sundogplanets Would that stop colonization? Especially for the peripheral worlds?
@Pxtl @Nick_Stevens_graphics @sundogplanets That's the question I've asked, but framed it as "How long would it take humans to populate our galaxy, assuming we could create colony-ships that could travel at a tenth the speed of light or faster?" And where 'colonizing' means colonies of a million or more around suitable stars.
My guess is the first civilization able to colonize other stars would colonize the whole galaxy before the next such civilization emerged.
@BLatro @Nick_Stevens_graphics @sundogplanets
Exactly. And we're 13.7 billion years in.
If it were possible, it would've been done already. So where are they? Is it impossible, or is the Great Filter behind us and there is no other sapient life in the galaxy?
@Pxtl @Nick_Stevens_graphics @sundogplanets Life I think will be common. But life was here for about three billion years before the Cambrian Explosion. That suggests getting to advanced lifeforms is probably a quite unlikely event, never mind human level intelligence.
@BLatro @Pxtl @Nick_Stevens_graphics @sundogplanets intelligent life has evolved independently on Earth in both cephalopods and mammals suggesting it may not be uncommon. Its human manipulation of the environment thats unususual, though many animals do this too, humans are more like universal constructors, if we can’t achieve something, we can eventually make a technology that will. This ability and a lack of understanding its implications is probably also our downfall
@Glubhorn9 @Pxtl @Nick_Stevens_graphics @sundogplanets Human's intelligence is the thing most likely to prevent us from becoming extinct. (Meaning in the next few millions of years or so, or whatever.) Without it, whether we become extinct or not is just a matter of chance.
@BLatro @Pxtl @Nick_Stevens_graphics @sundogplanets the factors likely to drive human extinction in the near term are those caused by our intelligence - anthropic climate change, nuclear, chemical and biological weapons, environmental degradation and AI if you believe the hype. I’ve never seen evidence that more intelligent species go extinct less often
@Glubhorn9 @Pxtl @Nick_Stevens_graphics @sundogplanets We're not extinct yet, and there's never been any other species on Earth as intelligent as us. Meaning the jury's still out on this question.
@Glubhorn9 @BLatro @Nick_Stevens_graphics @sundogplanets okay, so where are the AGI aliens?
All the same factors remain in the Fermi Paradox if we replace ourselves with AGI? Hell, if anything self-replicating conscious boxes of silicon on spaceships instead of fleshlings is *more* likely.
@Pxtl @BLatro @Nick_Stevens_graphics @sundogplanets self replicating AGIs would be unlikely to have the same motivations as us or their creators. Its limiting to think an alien civilisation would operate like capitalism in space. Maybe AGIs woukd just lurk under the ice in the Kuiper belt doing alien stuff. Maybe they would disgust us.
@Glubhorn9 @BLatro @Nick_Stevens_graphics @sundogplanets okay but that's not the question. The question is whether they'd colonize. Would *any* of them *ever* be expansionists? Because it only takes one expansionist group - fleshy or otherwise - to spread across the galaxy.
@Pxtl @BLatro @Nick_Stevens_graphics @sundogplanets what sets out is not going to be what arrives. An entity that began by agressively expanding might just settle down and adapt locally if it found a nice star system. On Earth species quickly diverge when separated geographically, the scale of space is far more extreme, in every direction expansion would have a different result
@Glubhorn9 @Pxtl @Nick_Stevens_graphics @sundogplanets That we'd evolve as a species if we started colonizing the galaxy is a plus, as it'd make us a more resilient species, or group of species. How fast we could travel would also play into this. There'd be a big difference between speeds close to the speed of light and slower ones where time dilation has little effect on the aging of the passengers.
@BLatro @Pxtl @Nick_Stevens_graphics @sundogplanets evolution doesn’t lead to resilience. Over 99.9% of all species to have evolved on Earth are extinct, not sure it would be different in space
@Pxtl @BLatro @Nick_Stevens_graphics @sundogplanets there is non human sapient life on Earth already. Instead of trying to communicate with elephants or whales or octopi, we subjected them to genocide for profit, eating many of them, and turning others into pianos and billiard balls.
@Glubhorn9 @Pxtl @Nick_Stevens_graphics @sundogplanets There's still that three billions of years of mostly just single-celled life on earth. We've no idea how unlikely a Cambrian-like explosion is. And yeah, there's other intelligent life on Earth, but it's not human-level intelligence. No whale, elephant or octopus is wondering how we might divert an asteroid from smashing into Earth, never mind actually doing something about it. Humans are though.
@BLatro @Pxtl @Nick_Stevens_graphics @sundogplanets we have no idea what other animals are thinking, almost nobody is interested unless they think like us, its pure chauvinism.
@Glubhorn9 @BLatro @Nick_Stevens_graphics @sundogplanets this is all a moot point. The hard part of evolution wasn't to sapience, it was multicellular life.
It took 800m years to go from simple multicellular animals to humans (and maybe other sapient animals? Doesn't matter!)
It took 4 times as long to go from the earliest single-celled life to *any multicellular life at all*.
So if we find life on other planets? Odds are good it's just microbes.
@Nick_Stevens_graphics @sundogplanets it's a big big Universe, this Galaxy alone is insanely big. Life may be common but complex, self aware life....very hard to come by.
@sundogplanets I went with "don't travel/don't last long," but on a cosmic scale, "not long" could be a long time indeed but still not overlapping with others. Life might be relatively common but life that evolves to use technology in ways detectable by other technology using life might be rare.
@sundogplanets None of the above, but equally don’t ask me what the other options should be.
@sundogplanets I was listening to a piece on NPR the other day talking about the mitochondria, and that the endosymbiosis between it and cells was such an unlikely event that if there is other life in the universe, it's probably microbial.
Does that count as homeostatic awakening? It's not that they've moved to a lower energy state, it's that they never got the energy to become larger in the first place without something like the mitochondria.
@DLink @sundogplanets But endosymbiosis has happened multiple times in the history of life on Earth? e.g. at least once with mitochondria and at least twice with chloroplasts. Multicellularity has likewise apparently appeared and disappeared many times.
Which is not to say that "non-microbial life is extremely rare in the universe" is wrong. We cannot say one way or the other.
@michael_w_busch @sundogplanets You're right about chloroplasts, but I'm afraid I can't offer any defence of this hypothesis because I was just listening to people talk about it. You might get more clarification by asking an expert. I believe it was an episode of Radiolab called "Cellmates" if that helps.
And of course we can't say it's one way or another, that's sort of the point of this exercise.
@DLink @sundogplanets I learned the above examples via biologists who were rightly criticizing the mistaken assumptions about Earth biology that astronomers have often made in discussing possible extraterrestrial life.
Here I recall @pzmyers ; who points out that while multicellular life keeps showing up in the history of life on Earth, the collection of traits we are pleased to call "intelligence" doesn't (and echoes other biologists pointing out SETI's peculiar definition of intelligence).
@michael_w_busch @sundogplanets @pzmyers I appreciate you deferring to a biologist. Is it possible you could point me in the direction of some of these criticisms?
I'm not trying to proselytize, just parroting things I've heard smarter people say.
@DLink @sundogplanets Here is one of @pzmyers 's pieces: https://freethoughtblogs.com/pharyngula/2006/10/24/a-little-pessimism-about-extra/
(From quite a while ago now.)
@michael_w_busch Thank you! 2006 isn't too bad. And it doesn't matter cause I hadn't seen it!
If anything though, doesn't this sort of bring up my point? They even call the first eukaryote an astonishing and unique event, and position it as a barrier to intelligent life. Of course, he goes on to say that even though that happened, millions of lineages failed to achieve "intelligence". If anything, this tells me that the barriers to intelligent life are even greater than my example.
@michael_w_busch @DLink @sundogplanets just what I was thinking!
@DLink I'd call that "we are alone" in terms of intelligent life.
@sundogplanets Voted “don’t last long” due to the cosmic scale of things.
@sundogplanets Voting my hope here
@sundogplanets Shouldn't 2 have a c option? That other civilisations do travel, however long they last, but space is really big? Even if humanity reduced itself to atoms tomorrow, our furtherest probes are still our furtherest probes. Which raises the question: even if we did receive an alien satellite, how could we know whether the civilisation that sent it still exists, or when it was sent?
@GavinChait @sundogplanets makes for cool science fiction stories!
What matters isn't "travel" but "colonize".
If aliens stay on their homeworlds and send out only probes and explorers until they die or fold up into silence? No Fermi paradox: Everybody stays in small sphere near home.
But if it's possible to colonize, somebody would've done it. Then geometric growth kicks in and you spread over the galaxy in a few million years.
If it's possible to colonize, where are the colonists?
If it's not, Earth will be our tomb one day.
For the same reason, #TimeTravel remains a will remain fiction.
Going back to infinity in time, if Time Travel were at all possible, it would have already happened. Where are the time travelers from the past?
And #God.
If God were real, She would have revealed Herself to us already.
If God were real, She would not need #prophets and #evangelists to distort Her word while they allegedly try to spread it. She would tell it directly to us, clearly, succinctly, and unequivocally.
If God were real, and She were omnipotent, She would not need #religious #fanatics to “do Her work.” She would do it Herself.
So it falls upon US to confront evil, not rely on God’s grace.
@rameshgupta @Pxtl @GavinChait @sundogplanets or, as Hawking famously said, if time travel were possible and would have been invented in our future, where are the time-travel-tourists from the future that would come visit us?