Could Earth be the only planet with intelligent life?
bigthink.com
bigthink.com
-- create some way of sustainably separating "self" from its environment, so that all the components of downstream steps don't diffuse away. The separating material, which could be a cell wall or cell membrane, also has to allow selective exchange of raw materials in and out of the cell, and provide protection against damage to the cell.
-- design and build a chemical template (DNA/RNA in our case) which allows it to reproducibly recreate itself and all its components.
-- design the molecular machinery which builds that chemical template, and which is also responsible for reading and interpreting the template, regulating its use, and providing error correction. Instructions for creating machinery that makes the template are encoded in the template.
-- design the molecular machinery (enzymes and other proteins) that builds molecular machines, using a design language encoded in the chemical template.
-- establish a chemistry program that takes in raw materials from the environment, and converts it to energy, building blocks for the machinery and template, and allows for repair, defense, and other tasks.
-- establish and implement reliable reproductive (data backup) framework, minimally involving the creation of a copy of the chemical template, and often copying and spinning off a second, complete cell.
These are the elements of basic, independent (i.e. non -parasitic) life. As far as we can tell, the core elements (information stored in DNA/RNA encoding proteins as molecular machines) of this life solution emerged fairly early in this planet's 4.5 billion-year existence, and every other organism since then has simply iterated on the same solution -- no other competing solutions exist to our knowledge.
It thus makes sense to account for this complexity when we calculate the odds of finding life in the universe. In my opinion, the Fermi paradox is nonsense.
And on top of this complexity of life, it took like 4 billion years on earth (that's roughly 1/3 of the age of the universe) from RNA/DNA to intelligent life forms that can talk about this on the internet. And during this time, no catastrophic global event has happened to undo all that development. Comparing Earth to other planets in our solar system (we cannot really compare to other systems, obviously), Earth is really lucky that there was no such catastrophic event. So many factors are important for this -- our sun is just the right size (not too harsh UV radiation (bad for molecules to be stable), not too small to make our orbit so small that rotation would stop (blowing away the atmosphere)). Our moon is unusally large for a planet like ours, yet it was vital for stabilising the Earth's axis (stable axis == stable weather) and slow down its rotation. And for the moon to emerge, a very nearly fatal impact from another body of the right mass (Mars sized) needed to happen at the right time (very early). At the right speed and the right angle. The availability of water and oxygen at the right times in Earth history where also quite a big unlikelyhood. And it goes on and on: Earth is unimaginably lucky.
Taken all this together, I doubt that anyone could multiply the probability of life on a planet with the amount of planets in the Milky Way (or the universe) we think would be Earth candidates, and claim to have a sensible number. The later is an unimaginably large number, but the first is an unimaginably small number and also a very unknown number. So: we just don't know how often life happens.
And also, detection is not trivial: it is not that easy to see other planets (they are far away), or alien space probes (they are small, space is large), other radio waves (they are weak), or any other signs of intelligent life.
https://en.wikipedia.org/wiki/Zero_one_infinity_rule
I mean, it's potentially possible Earth is the only planet with intelligent life (though highly, highly improbable). But the moment we discover any other planet with intelligent life, then we must assume there are an infinite amount (if the universe is infinite).
Of course this brings up more questions about what is intelligence? Is a slime mold intelligent?
Actually, without any additional knowledge I'd assume that some sort of seeding has happened, as that's presumably more likely than live developing independently.
Its highly probable that, if human-scale intelligence/civilization exists on other planets, Von Neumann probes (or some similar, highly detectable signs of activity) would have reached us by now.
And they have not. This is an interesting paradox.
So first question: why even Von Neumann probes? What would be the purpose of a self-replicating spacecraft? If it's science, then there's no reason to assume we would even be able to detect it. If it's some kind of colonisation effort, it only requires more assumptions.
The basic assumption that the Fermi "Paradox" (I refuse to see it as a paradox) requires, is that technological civilisations remain unchanged over geologic time spans. That's a bold assumption, judging from our sample size of 1. Another assumption is that such civilisations grow exponentially for a practically unlimited amount of time (yeah, yeah, millions of years isn't exactly "unlimited", but on a human time scale it kind of is).
Given the vast distances in both time and space, it's much more reasonable to acknowledge that technological civilisations are simply too far apart (in both time and space) to make contact in most cases. A thriving local interstellar civilisation on the other side of the Milky Way within the Zone of Avoidance would be virtually undetectable by us, for example.
Actually I think the opposite assumption, that civilization radically changes over time, is an argument for it. Future humanity is not people on (sublight) space boats touring the stars like Star Trek, its seemingly some kind of unfathomable transcendent intelligence. Maybe its not even recognized as "civilization" by our standards.
And why would such an intelligence not explore its environment? What's the likelihood, if there are many such intelligences, that essentially all of these intelligences choose to remain static, stagnant and stealthy instead of making their presence known within their light horizon?
The exploring civilisation falls into a similar category: if they are super advanced, they wouldn't be seen unless they want to. So no data point to be had there either. If they're just advanced enough to cross the vastness of interstellar space, they'd take hundreds or thousands of years to get around, so very little chance for them to randomly bump into us at this specific point in time.
"Making your presence known" is also on shaky grounds, since it only takes one. By that I mean it only takes one locust-like civilisation that matches the "Grabby Aliens"-hypothesis to conquer the known universe within just a few billion years. This would imply, that it'd be highly likely that we ourselves would be part of- or descended from this super-civilisation. Again, the facts don't support that.
OTOH, it also only takes one civilisation that wants to prevent such scenario. They don't even have to be around anymore. All it takes is seeding the universe with self-replicating "sentinels" that simply sit dormant around M-, K-, and G-type stars and watch. Once they detect a space-faring civilisation popping up, they'd being their assessment. If the AI suspects a "Grabby-Aliens"-scenario, it's time for Exterminatus or some other, more subtle means of preventing the scenario from materialising.
So subtle in fact, that the affected civilisation might not even be aware of it. In fact, it could happen to us right now and we'd be none the wiser - ever wondered why it haven't made it back to the Moon in over 50 years ;)
The fun part about this hypothesis is that it's just another scenario that we wouldn't be able to detect or rule out: GRBs happen all the time, good thing Earth hasn't been in the way of a nearby one... Or imagine another Carrington Event, only 50x stronger, blasting us back into the stone-age - just another otherwise oddly calm G-type star having a little hiccup; nothing unusual our extra-terrestrial neighbours would think...
Basically the number of scenarios that would match our observations so far while still allowing for a universe teeming with technological civilisations, outnumbers any hypothesis that would truly present a "paradox" IMO. (just an opinion, not a fact, I could be very wrong on this)
This somewhat suggests or relies on humans not being uniquely territorial and resource hungry.
Kind of like the saying that if you see one cockroach you have many, many cockroaches.
1) Galaxies far away are also far back in time - they could all be Dyson-sphered by now and we would be able to know for millions or billions years.
2) This also might have happened elsewhere - we have no means of detecting what's going on in nearby galaxy clusters, or even within our own Milky Way really.
3) In this line of thinking, alien civilisations are always a walking oxymoron or paradox themselves: so they are super-advanced, yet have to be detectable, and they think like us but also don't, because they know about the consequences but don't care about them. They also act without reason but at the same time with purpose. And they are superlong lived (or their machines are) yet feel the need to breed at insane levels to settle entire galaxies because of... of the resources they actually don't need if they wouldn't expand like crazy? - but wait, you said there is no reason - ah my head's spinning :)
Here is one such video I highly recommend.
Or, how do we know they haven’t reached us? Maybe they stayed in the outer solar system. Maybe they came, looked, and left. Maybe they have some sort of cloaking device technology. Maybe they are really small. Maybe they came during the age of dinosaurs and probe is still out there in space, shut down and waiting to be discovered.
Unless human civlization collapses, why not?
> Or, how do we know they haven’t reached us? Maybe they stayed in the outer solar system. Maybe they came, looked, and left. Maybe they have some sort of cloaking device technology. Maybe they are really small.
Ifthere is even one more civilization sending out probes, that implies there are many within our light horizon sending out probes. I find it implausible that every single one would choose the same strategy of keeping probes stealthy and undetectable.
Second, life just seems not easy. Intelligent life doesn't necessarily have conditions to be sending out masses of timeless void travelling probes on and on. Probably a lot of the advanced ones struggle or lurch along as we do trying to subsist off the local ecospheres.
This is not how VN probes work....
VN probes work more like the lily pad riddle that humans commonly fail to understand.
>In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of the lake?
The answer of course is the answer 47 to the riddle. With VN probes the answer would be "who the hell knows" at this point. Maybe interstellar space is a whole lot more dangerous than we expect and sending out countless self replicating probes isn't possible. Maybe the intelligent aliens out there are a whole lot smarter than us, and the idea of sending out probes that you effectively lose control of is recognized as a bad idea. Or, maybe there is no one else is out there. Hard to figure out with a sample size of one.
I mean, RNA/DNA has done that by trial and error alone. Of course the question is how do you keep it on task and not going extinct.
So I'm not sure why you'd think that a civilisation comparable to humans would be able to.
Also: if you can build Von Neumann probes, you can construct a Dyson swarm. You just instruct the probes to create the components of the swarm from the raw materials in your star system. But that would massively boost a civilisation's energy budget. Therefore, it's quite likely that any civilisation capable of building Von Neumann probes will have built a Dyson swarm.
So, secondly, it's about as paradoxical as the lack of detected Dyson swarms.
If the rules of software design apply to the universe, what is to stop us from assuming that our almighty creators are storing an $intelligent_life_form_count variable in a single byte somewhere and there can only be 255 of us ?
Testing can only disclose the presence of bugs. Never their absence.
So it's impossible to prove there isn't any life beyond Earth.
why do you say that? If SETI finds unambiguous signals, and they're independently confirmed several times, why would that not be "proof"?
As for the last sentence, the less said the better. "All our existing evidence" is pathetically small.
Likewise, we just need to seed other star systems with intelligent life and see how many our astronomers can find.
The more we move to the right of this sum the hard is to replicate conditions to find bugs and so we move from finding to probabilities and risk management.
With that said, this could explain why we will not detect life because we only had the technology to detect what we call life, and this window could be only 1000-2000 years before we moved beyond physical reality. So the chance that a similar intelligent life with similar tech era out of billions of years makes it almost nil. Both windows has to match.
From what we know, life is effectively guaranteed to emerge on a planet with a rocky core and water in the habitable zone. Are there planets like this? Yes, lots, probably.
We don't know how many random chemical reactions are required for life to be likely. We probably agree that a small puddle isn't likely to spontaneously generate life within a century. We like to think that one planet for a billion years is about the right size. But it could be that it takes a whole universe of planets before it's likely to happen once.
If that were the case, then the universe would look exactly like it does now, with us living on the planet where it happened and no life discovered elsewhere so far.
Of course not. But that's why we discuss probabilities.
We also can't discuss definitively about things that we have no reasonable ways to detect. So claims about there's no life because we would have seen them is completely worthless given that we have very, very few, if any, ways to detect such life.
Assuming it existed, are we even able to detect a planet like Earth with similar animal and human activity in any other solar system, even in the Milky Way? I am personally not aware of such general capability.
If we found native life on Europa or something, that would change things completely. Independent life arising at least twice in the same solar system would make it clear that life is common. But a sample size of one, with the anthropic principle, leaves us no clue. Life might be common, or we might be unique.
You're assuming something. Maybe something like "a world with water has high probability of life emerging". That is a massive assumption.
Given that I find that assumption implausible, I consider the rest of the post to be built on a flawed foundation.
With what else I added: a rocky planet with water, an active molten metal core, and in the habitable zone. It is indeed my understanding that life on such a planet is quite probable. Life is described as "not hard" given such conditions. And Mars was such a planet.
It is also my understanding that Mars absolutely had large bodies of water. Basins, waterfalls, etc. have been discovered that could have only been formed via large, flowing bodies of water. And this would have been during a time where Mars' core was still active and the Sun was hotter, making Mars warmer than it is now.
Yeah, see, that's an assumption. And "not hard" is very far from a universally-accepted evaluation of the odds for that situation.
So, when someone like me comes along who doesn't buy the assumption, can you provide a foundation for it that is stronger than "yes, I assume it" or "everyone knows"?
> can you provide a foundation for it that is stronger than "yes, I assume it" or "everyone knows"?
That's not really an accurate portrayal of my argument. But here's sources I know of.
* Origins of Life course on Complexity Explorer
* The Origin and Nature of Life on Earth: The Emergence of the Fourth Geosphere
* Every Life Is on Fire: How Thermodynamics Explains the Origins of Living Things
And I'm not talking about probabilities that deal with how large the universe is. We know that it is unfathomably huge, with countless galaxies, stars, and planets.
But in "Fermi's Pair o' Decks" there is an illustration of just how few things need to align "just so" to make it almost certain that we are the only life in the universe: https://shaungallagher.pressbin.com/blog/aliens.html
In fact, all you need are two decks of playing cards to understand how combinatorics can very quickly overwhelm our intuitions.
https://www.sciencedirect.com/science/article/abs/pii/S00945...
"the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand"
Life pops up really fast. Going from Prokaryotic to eukaryotic takes a really - almost weirdly - long time. Presumably going from eukaryotic to something we can easily recognize as intelligent takes an even longer, which again is weird, amount of time.
From that I'd expect life to be common and intelligent life that's reachable to us - that is on a time frame / distance that is reachable for humanity as a species - to be either non-existent or rare as hens teeth. It may be common in terms of the universe though just not knowable.
It will definitely a "no" when we find clear evidence of intelligent life elsewhere, but we should know for sure when we inspect every other place in the universe, in all history of it, and that is billions of light years spanning billions of years to say "yes". And we can't even rule that out even in our closest star system, at just 4 light years from here, yet. Everything is too far away from our view to rule out that is not in some place that we didn't see yet, because practically everything fits in that definition.
“The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence.”
But with 10 to the 24th stars, even one in a billion odds are no deterrent.
There is simply no explanation for the existence of life at all.
Nobody has the faintest idea how life came into existence, and the question of the origin of life is, frankly, the only interesting question because it is a prerequisite for the existence of any other question.
Without life there are no questions.
Let’s say that Earth is about 4.5 billion years old and that intelligent life has been externally detectable for about 120 years since radio was invented around 1900. And it’s by no means certain that just because a civilization on a given Class M planet achieves radio signal generation that it will soon achieve warp drive technology and build a fleet of starships. That civilization could simply watch episodes of the Golden Bachelor while consuming all of its available resources and then fade away. Or just blow each other up.
I’m not saying that intelligent life outside of Earth does not or has never existed. We can only detect a small part of the known universe. And we can only detect what’s going on roughly right now because there isn’t a WayBack Machine for interstellar radio signals.
All this requires the combination of several low probability events:
* A planet must be within detectable range of Earth.
* A civilization must have developed.
* The civilization needs to survive for a meaningful period of time. One century is not meaningful.
* The civilization must be visible essentially right now.
I’m not saying that the search for intelligent life on other planets isn’t interesting or worthwhile, but I do think that Elon Musk should stop wasting his time on space travel and start spending it on global warming. That will give us the best chance of extending our run as an intelligent civilization.
The primordial soup argument is akin to lightening striking a wheat field and spontaneously producing a birthday cake complete with icing, candles, and balloons.
Most theories postulate simpler replicating chemical reactions, maybe around hydrothermal vents or pools, possibly forming in mineral structures and cavities. Later on membranes may have formed, and so on. Many steps, not one.
It is of course speculation as we just don't know. But if you agree that life occured naturally without supernatural intervention (or aliens, but that just pushes the speculation to how the aliens occurred), then there must be such a set of steps.