We are trying to extrapolate the odds from a sample size of one. There’s just not enough data to know what the actual odds are.
What are the odds that some intelligent creature elsewhere in the universe is right now making an argument from incredulity like the OP’s?
I’m not sure what point you’re trying to make. Some of what I described primarily occurred in the early era of the universe after the Big Bang, but all of these processes are still ongoing and we can indeed observe them, directly and (mostly) indirectly. Some of the heavier elements, including elements necessary for life, can be observed in the spectra of stars, where they are formed and later dispersed through space. Other elements are formed in supernovas or in interactions with neutron stars. These processes appear to be the same everywhere in the universe. On earth, we can observe the formation of organic compounds and we can create them ourselves. We can observe unequivocal evidence of evolution.
The argument for the existence of life elsewhere – and by extension, for some of this life to be intelligent – is the most extreme possible example of an argument from probability. Sure, we have no data from which to extrapolate the relative amount of extraterrestrial life in the universe – although we do have data suggesting that planetary systems are a lot more common that some had thought. But to suggest that the incidence of extraterrestrial life in the universe is precisely zero requires the belief that in the more than 13-billion-year history of the universe during which the formation of life was possible, it only happened once, and in the inconceivable vastness of the universe – which we believe to have the same chemical composition and physical laws everywhere – it only happened here and absolutely nowhere else. Such an incredible hypotheses requires an explanation so powerful that it’s beyond science; it would have to be described as a miracle.
“There are millions of sapient life forms in the universe. You’re not one of them.”
This it the key thing. For all we know, we are the biggest fluke occurrence in the history of the observable universe.
Only THIS fraction really matters now. We know the universe is really big, but if the odds of an earthlike planet generating a technological species is one in five hundred octillion, well, we’re lucky there’s even one.
There are, science guesses, 2 trillion galaxies in the observable universe (a number that shrinks as time goes on but never mind that for now.) Our galaxy, a fairly substantial one, contains upwards of 400 billion stars, so let’s suppose the universe contains 800 billion trillion stars. Let us further suppose than one ten thousandth of them have an Earthlike planet, which I’m drawing from known planets but which is probably REALLY high, but what the hell. So we are left with 80 million billion Earthlike planets (80 quadrillion.)
OK, what fraction of earthlike planets produce a technological species? Yu don’t know.
As @Sam_Stone then points out, we have the issue of the speed of light, limiting the effective range of what exists to us. No part of the universe beyond 13.7 billion light years can be seen at all, and the speed of light limits what intelligent life anywhere “Exists” in any sense that matters. The speed of light is also the speed of information.
There is no way to know what the actual chances are. We know next to nothing about this.
But that’s LIFE. We don’t know how common it is but it seems impossible it has not arisen elsewhere.
But the OP asks about INTELLIGENT life, by which I assume they mean technological civilization. That may be a one time fluke.
Look at it this way; there is really no other animal on our planet liked the streaked tenrec. Tenrecs are a family of mammal that only occur in Madagascar; they are sort of like a combination of the hedgehog, the mouse, and the possum. They’re odd. The streaked tenrec, aside from looking absolutely fucking crazy as compared to most tenrecs (they look like they dyed themselves in preparation for a Pittsburgh Steelers tailgate party), can rub its quills together to make a sound they use to signal one another or warn off predators - the way some insects rub body parts together to make sound. So far as I am aware no other mammal, living or extinct, does this. The streaked tenrec is really a one of a kind creature, like the playpus, axiotl, or Steve Buscemi.
What are the odds that some other planet has evolved streaked tenrecs? I mean really evolved an animal that is a mammal and has all the other morphological and behavioural features of a streaked tenrec and which is either identical in double helix DNA or close enough to it? I’d say it is VERY possible that the streaked tenrec is unique to Earth.
Well, what can’t that also be true of a technological species?
Well, if it were proven, it would be knowledge, not just belief.
I think belief is an appropriate word for a position like the OP’s. I’ve already said in this thread that I’m agnostic on the issue, so I’m probably where you are (“just leave it at that”). Still, while I personally think that the OP’s belief that there must be massive amounts of intelligent life throughout the universe might be incorrect, I do not think it’s irrational or “kooky.”
One thing I do personally believe, but do not know, is that we will not detect (let alone contact) intelligent life that exists elsewhere in the universe any time within my lifetime.
And I do not take this as evidence that it does not exist. “There is intelligent life somewhere else in the universe that we could detect (using technology that we currently have or could expect to have any time soon)” is a far, far stronger claim than just “There is intelligent life somewhere else in the universe.”
Right now as we speak, there is 0 extra terrestial life out there.
Until it’s actually discovered / proven, it’s all just speculation, educated guesses, fantasy, and wishful thinking.
I addressed that when I said “The argument for the existence of life elsewhere – and by extension, for some of this life to be intelligent – is the most extreme possible example of an argument from probability”. The argument that an intelligent technological civilization arose only once and only here, in all the vastness of time and space, evokes the same incredulity as the idea that life itself is unique to Earth; one can say the same thing about the alleged uniqueness of a technological civilization as one can about the alleged uniqueness of life itself, that such an incredible hypotheses requires an explanation so powerful that it’s beyond science; it would have to be described as a miracle. And I don’t believe in miracles.
The streaked tenrec probably IS unique to Earth, as is in fact probably every other life form here in respect to all exact details, because many of those details are evolutionary happenstance that provide no specific survival advantages.
But the evolution of high levels of intelligence, of problem-solving skills, of dexterity, and ultimately the ability to use tools, are all adaptations driven by survival. And indeed, for just that reason, we see the evolution of some of those same traits in the higher animals; they are not unique to homo sapiens except in degree. For that reason, it’s reasonable to expect that life has taken similar evolutionary paths elsewhere.
All of which is completely separate from the question of if or when we will see incontrovertible evidence or perhaps directly encounter extraterrestrial intelligence. I’m willing to believe that it may be a very long time indeed. OTOH, evidence suggesting the likelihood that some form of life exists on a specific exoplanet may (if we’re lucky) be forthcoming within just a few years, thanks to the JWST.
That’s an awfully solipsistic thing to say. There is zero evidence of extraterrestrial life but whether it exists or not is independent of what we here on Earth can detect.
For what it’s worth I’m not willing to say that given the countless planets circling countless stars there has to be some either. Sometimes you have to be willing to say, “We don 't know.”
Forgetting the evidence and just going on my gut instinct, I’d say this:
Given that life started on Earth almost immediately (in geologic terms) after conditions on Earth allowed for it, I’d hazard a guess that life is nearly ubiquitous in the Universe. I would not at all be surprised if we find microbial life on Mars, on Europa and Enceladus, etc.
Also given that after life started on Earth it spent billions of years as single-celled creatures suggests that the jump to Eukarotic life is a ‘great filter’ and such life might be far more rare than single-celled life.
Also, why have life at all? Well, the march of entropy can explain it. Once the universe cooled to the point where it entered the region of chaos and complexity, life emerged because it’s the fastest way to convert energy to a lower value state. An analogy would be vortices that form when flow reaches a certain energy state, to shed energy faster than laminar flow. At some point, the universe drives towards complexity as a means of dissipating excess energy. If we follow that logic, AI and computers are the next stage.
But again, the universe could be teeming with civilizations and we’d have no way to know unless they are right next door. We greatly overestimate our ability to find life if it’s out there by listening passively for them.
My prediction is that we will either discover life elsewhere in the next decade or two, or we will begin to realize that the conditions for life are exceedingly rare and we are a fluke. I’d probably take 2-1 odds that we find life signatures in the next five years.
The way we will find life isn’t through radio SETI, but by actually looking at atmospheres and other proxies for life with telescopes. Our range there is much greater. For example, if there’s a Dyson Sphere within say, 5,000 light years of us, JWST could probably tell if it was by looking at it carefully. If there is a super-Earth within a few hundred light years, JWST should be able to look at its atmosphere for signs of life. This detection capability is orders of magnitude better than what we’ve had with traditional SETI techniques.
We have also been limited until recently by having to look at very small parts of the sky at once. The all-sky surveys we’ve had to date are relatively low quality. But the new generation of survey telescopes like Gaia and the upcoming LSST (now Vera Rubin Observatory) look at the entire sky and record terabytes of data to be sifted through by humans and AIs. If there are bright enough fast-changing light signatures out there, we’re going to find them. Then we can use JWST or the next gen equivalent to examine them. If another Oumouamua shows up, we’ll find it early enough to send missions to it. If there are giant alien laser communications crossing our path or huge energy signatures from relativistic spaceships around nearby stars, we might catch those as well.
And the Giant Magellan telescope and the new 30m class scopes will have resolutions 4X that of JWST and more. We’re in the golden age of astronomy right now. If we’re going to find ET or just some microbes on another planet, I think it will happen fairly soon. If we don’t, that means something as well.
I suggested in my previous post that the JWST has unprecedented potential to detect proxies for life. This is notably through spectroscopic analysis of exoplanet atmospheres. The trouble is that proxies are just that – indicators, not definitive evidence. And it will tell us even less about what kind of life it might be, in terms of evolutionary development.
A SETI breakthrough would be far more exciting, but almost impossibly unlikely.
This is true. Many of the potential indicators of a life in a distant solar system might be the result of entirely abiotic processes, occurring on lifeless planets with surface conditions that we are entirely unfamiliar with. We will need to be acutely aware of false positives.
I can’t put a number on it. And odds are numeric.
My guess is that there are extremely few planets with civilizations that reach our level of scientific achievement, and those planets don’t keep said civilizations very long. But a guess and odds are quite different things.
If I were betting my own money, I’d bet that intelligent life is common.
However, it’s hardly “kooky” to take the opposite position, while there is the Fermi paradox and the lack of empirical evidence. Which are really much the same thing…the Fermi paradox is a misleading name.
I don’t think the standard responses to the Fermi paradox, some alluded in this thread, are satisfactory. But I have debated this at length on SD before. So I’ll resist the temptation to go into that for now.
I think that really depends on if FTL travel(or wormholes, hyperspace, Warp drive, Infinite Improbability Drive) is possible. if it’s not, then that can explain a lack of contact. Plus, we’re kind of out in the boonies.
If you lived in the center of the Milky Way, you would look up at a sky thick with stars, up to 1 million times denser than we’re used to seeing. The closest star to our sun is about four light-years away; in the center of the galaxy, stars are only 0.4–0.04 light-years apart.
It’s not that simple. As ludicrous as the distances between stars is, even travelling far below c a species could spread across the entire galaxy in mere tens of millions of years…a fraction of the age of the galaxy.
Plus, evidence of ETs doesn’t necessarily mean they need to knock on every door in person…detecting any kind of signal, or radiation (e.g. from some kind of superstructure), or technology (e.g. self-replicating probes) would also do. We don’t see anything like this.
Also, FYI, the coolest night sky would probably be in a globular cluster. In the middle of those, stars can be as close as the outer planets of the solar system are to us.
We should also recall that it took some unlikely events to get Earth to support life in the first place. Professor Brian Cox explores these events on BBC Two’s program “Human Universe”.
about 5 billion years ago Earth forms, and by chance ends up in the Goldilocks zone, which eventually results in temperatures where life can form.
4.5 billion years ago Earth gets a moon, but is almost destroyed in the process. A small planet smashes into the young Earth, greatly changing both objects, and causing the Moon to form. The Moon’s gravity changes the way the Earth moves through space. That affects our planet’s climate and give it fairly stable seasons, helping to shape the evolution of life.
The collision also released iron from the Earth’s core, contributing to the chemical cocktail from which life would emerge. Planets the size of Earth with moons the size of ours appear very uncommon based on what data we have.
4 billion years ago life-giving water arrives from space. The young Earth was a ball of molten rock, and any surface water quickly evaporated into space. So where did water come from? Some was probably trapped deep in the Earth as the planet formed, saving it from evaporation. It could then be released by erupting volcanoes, as the Earth cooled. And some came from beyond our planet, from millions of years of icy comets crashing into Earth. Without this water from beneath the Earth’s crust and from space, Earth would have been a lifeless ball of rock. Earth was lucky to be in the path of all that space ice.
3.8 billion years ago complex molecules combine to create life. How unlikely was the moment when life first began on Earth? That remains one of the greatest mysteries about the origins of human existence. We still don’t know how life arose, but it may well have happened at hydrothermal vents - underwater hot springs dotted across the ocean floor. They churned out a potent mix of chemicals and energy, that may have combined to create the first life. Whatever the truth, many scientists believe that with the right conditions, the chances of life arising are surprisingly high. But if those conditions had not existed on Earth, our planet today would be a watery soup of complex chemicals, but no more. Lucky chance again.
2.7 billion years ago a chance collision creates complex life. For a billion years, the only life on Earth was single cells. Then something happened which created the template for all complex life. Two single cells merged together. They got inside each other and, instead of dying, formed a kind of hybrid, which survived and proliferated. And because every animal and plant today shares the same basic building block – the same type of cell structure – we are very confident that this only happened once, somewhere in the oceans of the primordial Earth. Biologists call this one-time event ‘the Fateful Encounter’, and it suggests that complex life requires a good dose of random chance.
2.4 billion years ago a new type of bacteria creates oxygen. Life existed on Earth for billions of years with almost no oxygen in the air. Most bacteria fed off carbon dioxide and other gases, like methane. Then a new type of bacteria evolved. These cyanobacteria created energy in a new way: photosynthesis, using sunlight to split water. Oxygen was just a waste product of this process, but over time, levels in the air built up to what we breathe today. If this hadn’t happened (and the Earth went along merrily for 1.4 billion years with the old type of bacteria only), and Earth had stayed shrouded in carbon dioxide and methane, animal life could never have evolved on our planet.
1 billion years ago, we finally saw multicellular life take hold. Again, we had complex cells for 1.4 billion years before this step took place.
65 million years ago a cosmic meteor disaster wipes out the dinosaurs, who had dominated the Earth for over 160 million years. Without that random occurrence how likely is it that anything resembling Homo Sapiens would have arisen?
So we see that it’s likely that multicellular life itself, much less sentient life seems to have resulted from a string of unlikely events. How unlikely were these events? That’s still what we don’t know. So the jury is still how as to just how often life is still happening across the universe.
The oldest solids in the solar system are 4.57 billion years old.
The moon is probably around 4.42 billion years old
So around 150 million years between the beginning of the solar system formation and the solidification of the surface of the moon. (Which is a much bigger gap than we used to think.)
Per solar system? Approximately 12%, give or take 87.9%.
The Fermi paradox could be explained in different ways:
The Dark Forest theory. Civilizations build telescopes good enough to realize there is other technological life out there, and stop broadcasting strong radio-waves towards the sky so they don’t get “bombed” as a “precaution”.
Stars are too far away and too sparse in our corner of the universe to talk to each other, or visit each other. Too much background noise, too much distance. Maybe in the galaxy center, things are/were different?
Maybe we will see evidence of just the kind of life Fermi was wondering about in a telescope generation or three? Or ten?
Maybe Earth was actually populated briefly but the collision with what would become the moon wiped it all out, and it took a while for life to reappear? Maybe the prior occupants did not pollute so much, or didn’t live very long and are thus hard to see when we look at geological strata?
Argument from incredulity. I like the idea.
You see great obstacles but you fail to see the great heroes that rise from randomness, time and luck, and might overcome them as happened on earth. The unknown unknowns. Maybe earth is average. and we’re just too blind to see our alien relatives.
That is an excellent post indeed. You have put a lot of what I fuzzily thought in clear words.
Fascinating. The most efficient way, you say? Because we’ll go hunt that hydrogen-carbon? I’ve always been interested by the concept of life as a slow flame. A slow flame that knows how to seek food/wood to burn/increase entropy/what have you.
It is exciting stuff. We should put more money into scopes.
Yeah, I wish we lived in the galactic downtown too. You could actually talk to your neighbors and walk everywhere. Earthburbia is boring and super quiet
I think the only thing we can see is some sort of pulsar star that was/is pulsing in a clearly artificial way. Like morse code or smoke signals. Low-bitrate long range communication.
Since the universe may very well be infinite it’s probably certain that there is uncountable amounts of intelligent life in the universe. Perhaps even exact copies of ourselves. I don’t think it’s kooky to not be aware of how large infinite is.