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Comment by superposeur | Hacker News Reader

This is intriguing and I’m very happy this exploration is being done.

But, for decades, I’ve been reading reports of the discovery of evidence for the trappings of life elsewhere: water and organics and “habitable” exoplanets. These are valuable discoveries, but the tone of the reports suggest they imply life is about to turn up.

It’s worth remembering that there is not one single shred of evidence that life has ever existed anywhere in the observable universe but Earth. Moreover, no one has succeeded in hatching living matter from non living matter and we must honestly say we do not know how this process came about or the faintest estimate of how likely it is to occur (despite much speculation, some of which may turn out to be correct but equally may turn out to be dead wrong). The oft cited fact that life arose “quickly” after the formation of Earth has no bearing on the question.

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I would turn your logic around and say, everywhere we are able to look, we find evidence that life is more likely than expected. Until the 1990's it was an open question whether any other star had planets; as soon as we got the tools to test that, we found they were ubiquitous. As soon as we got the right instruments to Mars, we found signs of moving water, methane sources, and complex organic molecules in what is basically an Earth-like old lake bed. The moment PCR technology made it possible to do the search, we found a massive 'dark biome' extending many kilometers into the Earth's crust.

When you immediately find strong pieces of circumstantial evidence the moment you acquire the tools to start looking for something, the correct conclusion to draw is not "we have yet to find a shred of evidence", but that further searching is likely to be highly worthwhile.

These factors are what I call the “trappings of life”. It is a completely open question (and I mean completely) how likely life is to arise spontaneously when these factors are present. One single instance of life elsewhere or successful abiogenesis in the lab would change that, but we have neither.

We've barely started looking. It's like picking up one piece of hay, not finding a needle and declaring there's no needle in the haystack.

No is declaring that there is no needle in the haystack. Please actually read my post.

“I just want to be clear that we’ve definitely not actually found life. We’ve found likely precursors everywhere, habitable bodies everywhere, have plausible theories on how to go from precursors to bootstrapping, and see life in every corner of the planet we have explored. But just to be clear we haven’t actually found life anywhere else yet.”

Yeah, we know. So what then was the point of your post?

Well, perhaps you know that none of the recent findings are evidence of life, but in my conversations with others I have perceived a great deal of confusion on this point, even among scientifically literate colleagues. Also, the fact that we have zero understanding of the probability of abiogenesis is, in my experience, a greatly under-appreciated fact. I speculate that the way findings are reported contributes to this confusion.

Also, at risk of incurring a flame, I'll gently point out that you are folding into this confusion and reinforcing it with your language: "likely precursors everywhere, habitable bodies" ... we absolutely do not know that these conditions are "likely" precursors, which is a statement about a probability we know nothing about and as for "habitable" we do not actually know anything about whether or not a body is habitable in the sense of likely to spontaneously form life.

absence of evidence is not evidence of absence

sorry your life has created this crusade of rhetorically reminding people about the absence is evidence

Not in general, just on this particular point. Because, in my opinion, we as a scientific community are currently flush with the (very cool) unexpected discovery of so many exoplanets and it is somewhat distorting our collective thinking about life and its origins.

We SHOULD (be flush and distorted). We can be realistic AND enthusiastic about it. Some technically challenging work was done and achieved results FAR FAR beyond expectations. That is a result worthy of changing outlook. Before, the outlook was on statistical grounds (the universe is so vast that there has to be). Now this outlook has been justified a billion billion times over. It's certainly time to be far more ambitious and inverse the presumptions that we had before.

I.e. before, "there had to be - some, somewhere" and now, "there is most likely all over the place".

You can make the less charged argument that expanding the search for life has in every case so far led to extremely interesting scientific discoveries. So as a pragmatic strategy, it has legs regardless of where you stand on the question of life origins.

Provided you're actively and systematically looking for evidence, then absence of evidence is evidence of absence.

But we've not even started doing that yet. None of the mars rovers have landed anywhere close to where we think is must likely to currently harbor life due to fear of contamination.

We've just now learned how to analyze atmospheres of exoplants.

5 years ago, we couldn't see exoplanets smaller than jupiter.

A decade ago, we couldn't see exoplanets at all.

We still can’t see the atmosphere of the majority of exoplanets. Can’t get around it unless we build a telescope thousands of times bigger than anything else or we make some incomprehensible breakthrough in optics. If we could we would detect life on another planet within a matter of a few hours of telescope time most likely.

I find the entire idea that life could only exist on earth farcical. A lot of people in this thread don’t seem to understand that we can’t directly image many exoplanets to begin with and that we haven’t even been trying to find life on other planets and moons in our own solar system, it has in fact been suppressed every time credible circumstantial evidence of life is found (Viking lander experiments and methane on mars both come to mind)

I agree it’s an open question, but I think it’s highly likely with lots of circumstantial evidence that life is an evolutionary emergent phenomenon where inorganic material reactions create life. We already know that’s the case in highly controlled environments. We don’t yet have confidence about the exact mechanism on Earth but based on those experiments it’s likely (& generally currently accepted as the most likely mechanism AFAIK) that the boundary layer of volcanoes (probably underwater) + some crucial initial elements being available causes life to form “spontaneously”. Given the elements required and their overall availability in the universe, it’s also highly likely these conditions reproduce quite readily & life is generally quite abundant. Similarly, significant levels of intelligence within animals seems like quite a common occurrence as well (great and lesser apes, elephants, octopuses, dolphins, wolves etc). Whether or not intelligence + physiological evolution + social evolution to take advantage of that intelligence to build things cooperatively is a huge unknown of course although I think it’s inevitable. On the other hand, how long life sticks around on a planet once it forms is an open question - it’s not clear if a life ecosystem that’s stable for billions of years is likely and I suspect there’s probably a small amount of filtering that happens where planets become inhospitable rather “quickly” and can’t support life for multiple billions of years (e.g. there were probably several events in our history where it could have collapsed).

Our type of society is probably much much rarer because you need access to mineral and energy deposits to go through each technological phase. For example, because of all the mining we’ve done, if humanity were to disappear it’s highly likely the Earth would not sustain another technological society because all the “easy to get to” deposits of crucial metals & things like oil are gone and there’s no way to bootstrap a technological society (it’s possible other kinds of resources could be developed to build other kinds of technology so who knows).

I think based on our existing body of knowledge, life is likely extremely plentiful throughout the universe at one point in time or another. Some form of intelligent life is highly likely wherever we find any life that manages to stick around through bilions of years. A highly technological adept species of life though is highly likely an extreme rarity and a planet gets one shot at developing it. Whether any manages to escape their home planet remains an open question that likely only we will manage to answer over the next thousands of years if we make it that far.

>Our type of society is probably much much rarer because you need access to mineral and energy deposits to go through each technological phase. For example, because of all the mining we’ve done, if humanity were to disappear it’s highly likely the Earth would not sustain another technological society because all the “easy to get to” deposits of crucial metals & things like oil are gone and there’s no way to bootstrap a technological society (it’s possible other kinds of resources could be developed to build other kinds of technology so who knows).

As I recall-though it's been many years-this was something of a premise in Farmer's Riverworld series. Once you've taken the first pass though historical mineral etc. resources, you don't really get a second pass.

Readily obtainable hydrocarbons are lost for the forseeable future. However, haven't we made it easier for future civilizations to obtain minerals and metals? We have extracted, refined and placed them all in concentrated surface areas all over the planet (i.e. city limits)

Except a huge amount of it is alloys. You’d have to reprocess it to extract out the raw materials which is much harder than mining ore and requires a lot more tech. Like things may be bronze plated but you’re not going to find a whole lot of bronze in 1 spot.

Wouldn't the next civilization just find itself mining the remains of human cities? IIRC, the majority of the copper ever extracted is still in use.

Cue Indiana Jones voice: you can’t just mine that—it belongs in a museum!

> I think it’s highly likely with lots of circumstantial evidence that life is an evolutionary emergent phenomenon where inorganic material reactions create life

Out of curiosity, if you reject religion, what other possibilities are there?

Just inorganic material combining at random and eventually, over about 10 billion years, randomly creating something that self replicates in some way, beginning the process of evolution through natural selection and inevitably progressing to life as we know it.

I don't think religion is needed at all for this. I also don't think this has to be a common thing (after all, here on Earth it only happened once, but it's also possible that once life is widespread it makes it very difficult for emergent new forms of life to take off).

Where did you get 10 billion years of random chemistry?

The articles I read assert that life began just 500 million to 1 billion years after formation of earth. 3.5-4.1 billion years ago with an earth age of 4.5 billion.

The universe is about 15 billion years old, and chemistry didn't start with the formation of Earth.

Chemistry in earth certainly started with the formation of earth.

Are you suggesting that abiogenesis didn’t start on earth, but self-replicating molecules started evolving in earths protoplanetary disc?

Serious question, haven’t encountered that theory before. It’s kinda panspermia-lite.

I believe you may discussing at cross-purposes.

Presumably like your parent, I believed this was a discussion about the probability that life has originated elsewhere in the galaxy / universe, independently of life on Earth.

Kurzgesagt did a video on this recently https://m.youtube.com/watch?v=JOiGEI9pQBs

Sorry, I meant possibilities other than "an evolutionary emergent phenomenon where inorganic material reactions create life"

Commenter is referring to the case where life is a common occurrence as an "an evolutionary emergent phenomenon where inorganic material reactions create life" in contrast to the case where life has only happened once, which would be more like an extremely lucky fluke where inorganic material reactions create life.

Simulation hypothesis: all this may be much younger than we expect.

Nonuniform physics—call it colliding universes or whatever, but the processes that gave rise to life on Earth may not be possible anywhere in this universe now. Including labs on Earth!

>>>I agree it’s an open question, but I think it’s highly likely with lots of circumstantial evidence that life is an evolutionary emergent phenomenon where inorganic material reactions create life. We already know that’s the case in highly controlled environments.

Did I miss some big announcements? Where has anyone created life from inorganic material reactions in a highly controlled environment?

Serious question, not trolling.

Seems to me that would be an insta-Nobel.

I overstated that life from inorganic in a controlled laboratory environment is what we have evidence for. What we do have evidence for is organic compounds forming from inorganic environments and we’ve shown certain kinds of RNA can self-replicate.

Unless life originated directly at the formation of the universe and panspermia is how life got to this planet, the only logical explanation is that life somehow emerges from “nothing”. We don’t know the exact mechanism and it seems much more likely that life originates on a planet rather than in space & arriving at a planet. The “intelligent” panspermia explanation (i.e. aliens seeding life throughout the universe to preserve it) would still require an inorganic origin for life.

This is what I referred to as "speculation" in the literature for life's origins on Earth. This speculation is a good first theoretical stab... or it might not be. Until life is created from inorganic matter in a laboratory (enabling us subsequently to estimate how rare or not it might be elsewhere in the observable universe), we should substantially dial back our confidence from "life is likely extremely plentiful throughout the universe at one point in time or another".

I agree that we are limited to "speculating" due to n=1. However, personally my sense is that simple life is more likely to be ubiquitous than not. This is informed by the fact that currently there is no evidence that conditions on early Earth were particularly unique in comparison to first principles modelling of rocky planet atmospheres**. This coupled with the relative speed with which simple life emerged points to it being a relatively probably event, though we can't be certain. I expect that with missions such as PLATO and the upcoming HWOs we'll have a better sense of the conditions on mature Earth like planets in the habitable zone. Though studying a large sample of early Earth's shortly after formation may be out of our reach for a while yet, depending on which particularly mission gets chosen.

**Not my sub-field. Extremely complex models. Much is still unknown.

To me the simpler question is “if life didn’t originate from inorganic conditions somehow, what other explanation is there? Life came into being with the creation of the universe?”. It’s possible the latter explanation is what happened, it just feels extremely unlikely. So the more likely explanation is that life originates from inorganic conditions. Then the question is where? Is it on a planet or in space? Panspermia doesn’t have a lot of traction because the mechanism of action seems too complex to have a good probability of success unless intentional (but then you have a question of how did life that started panspermia intentionally begin & you’re back to needing it forming spontaneously out of nothing).

And if “out of nothing” is the baseline condition, the most likely explanation is that it happens where there’s a lot of energy to sustain it while not enough to kill it, which means planets at the boundary of thermal activity (since we need something more direct than photosynthesis which is a relatively complex capability that came late in Earth’s cycle as far as we know).

Taking a slight sidetrack to relativity, consider just how absurd our universe is. To maintain the consistency of the speed of light from all reference frames, time (and 'real' distance) are instead the variables, and there is every reason to believe this is correct. If you didn't know this to be the actual case, it'd feel absurd to even consider it.

Trying to intuitively and logically reason about something with no answer in sight, all while assuming the truths of our era, may ultimately be pointless.

Our universe, logical though it may be, plays by its own rules, and many things will be simply irreconcilable until those rules are further elaborated on.

As an aside the big bang also does not really answer the prerequisite question of where the initial inorganic matter/energy came from. The idea there being some sort of a quantum fluctuation, which then begs the question of its origin. I suppose it's just turtles all the way down.

The Turtle way down is called 'Rechnender Raum' also known as

https://en.wikipedia.org/wiki/Calculating_Space

And if the turtles feel bored out of their minds, they go full

https://en.wikipedia.org/wiki/Ouroboros and eat their own behinds.

Which solves the problem of recursion, hen&egg nicely.

Consider black holes, white holes, wisely.

The question of free will? Just checksum errors in the substrate.

Because entropy, of course!

Chill...

> To me the simpler question is “if life didn’t originate from inorganic conditions somehow, what other explanation is there? Life came into being with the creation of the universe?”.

OK let's pretend to forget for a moment that we have no definition for "life". Here is what we know:

    - tons of examples of life turning into non-life
    - zero examples of non-life turning into life
    - a crapton of non-life around us

Based purely on that evidence what do you think is more likely: that non-life magically converts to life or, idk, how about it started with life and all that non-life you see is formerly life?

Hm what if you add a forth known:

- a lot of examples where life exists where we were thinking it should not be possible

I think it raises a bit the idea that life is in a way special and fragile at individual level but not that fragile as a whole.

I think you are taking the wrong tack in your approach to this. You keep saying life must arise at the end of an experiment. The thing we can do is work through to dna base pairs arise. If you are then in the right environment for random mixing of these base pairs for millions of years, I do think you'll get microbes.

It's a big mistake to say we have to run an experiment that produces living organisms from nothing to say we know how it works. And that likely took millions of years. That feels like an excuse to argue that it can't happen without some external power (not the sun, ha).

I don't think inorganic material reactions can be described as an evolutionary phenomenon.

It is evolutionary in the sense that the various reactions slowly changes the make up of the environment until the conditions necessary for life emerges.

The other part of the open question is how easily life is able to spread across worlds. This is why it's so vital to go look at Mars without contaminating the search. If life spreads easily (whether within the solar system or more widely), then we'll likely find traces of life there that look a lot like our own. If life arises easily, but doesn't spread easily, we may find traces of very un-earthlike biochemistry. And if life is rare, we'd expect to find nothing.

Any of the three results would have huge implications. And then rinse and repeat on Enceladus, Ganymede, Europa, and so on. And find a way to look at exoplanet atmospheres and chase stuff that comes in from outside the solar system. Even negative results will add enormously to our understanding.

At this point isn’t Mars already contaminated?

No, almost certainly not. There are individual living microbes and spores on the various landers, but unlike the microbiome that would travel with a human mission, they're not viable and have no mechanism to get to somewhere where they'd be viable.

I mean, you say that, but also this story was a thing that happened:

https://www.cnet.com/science/sea-plankton-found-on-the-outer...

The leading theory is air currents from the planet slowly contaminated the station over the decades, not contamination before launch. It's also then still pretty protected by radiation still being so close to Eath. Our probes go through pretty tight clean room packaging, shed almost all their outside layers before leaving Earth orbit while still being very toasty, and then get blasted by intense radiation for months and are finally separated by some pretty massive distances on the planet.

idlewords was specifically mentioning that we have (found life elsewhere).

It was pretty clear to people that there would be no life 750 metres inside the earth crust below another 700m of ocean: too hot, no light, pressure, bla, bla. - And plenty was found. Of course it's an easy counter "Still Earth, haha! Doesn't count". So yes, it's back to the point that whenever we have developped tech to go look, we have found "whatever the tech could find". Except - for now - TV serials radio waves. That's true. And bacteria on Mars. Yes it's a glib way to put it but it's not an unfair answer to that criticism.

I went to a biology/astronomy talk where there was a researcher working on the sequence of chemical changes on the early earth without much water or atmosphere would need to create dna base pairs. It was stunning because they basically had a sequence of things and geological discoveries point toward the precursor chemicals being available. It's not that dna was just there.

This is not "life arising spontaneously". This is chemicals in an environment where they eventually build dna base pairs. Then after millions of years, perhaps you get microbes and go from there. Meanwhile we are getting water on earth from comets crashing down.

The “eventually build dna base pairs” (that continue self replicating) is the uncertain and possibly ludicrously improbable step. See for instance https://www.nature.com/articles/s41598-020-58060-0 which argues for a probability per exoplanet small enough that it hasn’t happened a second time in the observable universe. On the other hand, one of the self-organizing proposals cited elsewhere in this thread may turn out to be correct and the probability may be much higher.

The point is that, while there are some cool ideas on the table, everything hinges on the particular value of this probability (not just a qualitative story of how life might have arisen) and we don’t know what it is. Still relevant: https://blogs.scientificamerican.com/cross-check/pssst-dont-...

Sorry, I didn't see your posting before. The person speaking at the astronomy on tap presentation made it seem much more likely, basically given expected conditions on pre-biotic earth, very likely in a million year timeframe.

I'm a software engineer so I don't readily admit I don't know what I'm talking about. Are you in the field and can maybe elaborate on your skepticism? This fellow was pretty certain they've worked out several likely possible paths. This was last year.

typo "I readily admit that I don't know anything" ;-) And I have bad typing and proofreading skills!

Great comment! Indeed there is a recent Nature paper that's causing a lot of discussion that is investigating that missing link between the physics of matter and the emergence of the natural selection and evolution processes that give rise to life. this is a really fascinating area! https://www.nature.com/articles/s41586-023-06600-9

That link (going from basic chemical to bootstrapped evolution) is an entire field of research. Not one paper now and then. Labs, money, researchers building on each other's work... Just want to point out.

Any good (starter) books on this?

I have passed on the request to one of the scientists.

You call these factors "circumstantial evidence", but they are only circumstantial evidence if our ideas about what allows/causes/etc life are correct, which we have not validated at all.

If we can't promote abiogenesis in a lab our understanding is clearly limited, which is itself surprising. How many other processes in nature have we observed and not been able to replicate ourselves (or at least make progress towards replicating)?

“England has developed a hypothesis of the physics of the origins of life, that he calls "dissipation-driven adaptation."[3][5] The hypothesis holds that random groups of molecules can self-organize to more efficiently absorb and dissipate heat from the environment. His hypothesis states that such self-organizing systems are an inherent part of the physical world.[7]”

If Jeremy England’s hypothesis is true, then life shouldn’t be unique but rather inevitable, as life in general would be the way for matter to better dissipate heat, and better turn low entropy into high entropy.

In fact, if you watch what life is doing in terms of physics, then it’s obvious that all it does is consume low entropy (stored chemical energy, heat from heat baths), and dissipates it around very efficiently.

Even we, humans are more and more good at it: we take hydrocarbons chemical energy and turn it into work and heat. It’s not enough for us, we now consume energy stored in atomic bonds, and turn it into work and heat. We capture concentrated sunlight and also turn it into work and heat, etc.

Essentially, we are doing what we are supposed to do as a function of physical matter: we produce more entropy.

I don't think that's Jeremy England's idea.

https://en.m.wikipedia.org/wiki/Entropy_and_life

Henry Adams first put it to print in the 1910s, and Schrödinger did a fine turn on it and wrote a whole book in the 40s.

The idea that life exists as the most efficient method to facilitate thermodynamic equilibrium is older than the neutron.

It seems like a more fundamental phenomenon would be the ability to self replicate. I imagine some organic compounds forming a primitive vesicle in a relatively calm lagoon. As the vesicle collects more organics it gets too large and eventually blebs off a small vesicle (primordial fission). The heartiest vesicles that can replicate fastest tend to survive the longest and produce the most copies. Evolution takes it from there.

>> better turn low entropy into high entropy.

I took a double take and thought you'd made a typo, because I've never heard that assessment before.

I see what you're saying about dissipating heat and work... but life organizes. Most of that wasted heat from any organism is the result of its processing, consolidating and transmitting information. Which is probably the only counter-entropic (extropic) process we can observe in the universe. My view has always been that life fights against entropy.

>but life organizes

Yes, and that's the interesting part. In the right circumstances, more entropy doesn't mean less complexity. Matter can become more complex and less entropy locally if that results in increase of total entropy in the system. This can occur, for example, if we have constant flow of concentrated energy on some local areas of the environment that continuously wants to spread out. Because the system as a whole "wants" to maximize its entropy as fast as it can, and it statistically "searches" for the shortest paths possible. This may result in natural occurrence of more and more complex molecules that dissipate heat more and more efficiently.

It's like the planet's atmospheric processes, for example. Where differences in heat concentration don't just spread out in linear gradients but can form complex structures like vortexes, hurricanes or even stable geometric hexagons (like the famous hexagon storm on Saturn), etc.

>My view has always been that life fights against entropy.

Yes, it "fights" against entropy to exist, but it exists solely by processing low entropy into high entropy. Maybe that's why it even exists in the first place?

This part is better addressed in Jeremy England's work, for more basic explanations you can refer to videos like

this: https://www.youtube.com/watch?v=GcfLZSL7YGw (it's a very good video on this topic by PBS)

I would turn this argument around and say if life elsewhere is more likely, than it should be more likely that life from beyond has found us. If the likelihood of life elsewhere is so high that it has to be true, to me it would also be true that life should have found us by now

I really don’t think people are talking about intelligent life here.

We’ve also found water on the moon.

And we know at least one Jupiter satellite has water.

So that’s at least 4 bodies in the solar system that have water and all the bodies where we have successfully landed more than 1 rover have or had water (earth, moon, mars).

Every body where we could have discovered water, we have discovered water. Seems like bayes theorem indicates that water is also probably highly available in the universe.

"we find evidence that life is more likely than expected"

But only after we really lowered our expectations in the first place. I have an old book, about the Viking Mars lander, describing the technical details, before the rover succesfully landed on mars. It is full of optimism and a strong expectation, that it will find evidence of at least bacteria.

And before we had strong telescopes and rockets, there was a strong expectation, that Mars has developed life.

We know, that bacteria can survive in stasis mode on asteroids - yet we have not found life on any other planet.

Those original expectations weren’t based on evidence though.

> we find evidence that life is more likely than expected

The easy steps for abiogenesis keep getting easier and easier.

Meanwhile, we keep having absolutely no idea of the difficulty of the hard steps. Yes, technically that means life is easier than we expected, by some completely insignificant margin.

I once heard: „The universe is unbelievably huge and unbelievably old so rare events happen all the time.“

I think it meant that even if life started itself accidentally by some unbelievably slim chance, this could happen somewhere else as well simply because the dice are rolled that often.

I think time is the factor here. When you take into account not only the size of the universe but also it‘s age, the chance that life started somewhere, somewhen and ended long ago could be larger than zero, even if we are not able to calculate it.

All dimensions are a factor. Life could exist on different time-scales (e.g. it moves so slow we thought it was inanimate). It could exist on different physical-scales (be so large we don't realize we are a part of it). Or, it could exist on an entirely different plane of existence (on a desolate planet in a shard of silicon that is turing complete and quietly simulating its own recursive universe).

> be so large we don't realize we are a part of it

While these are valid and interesting ideas from science fiction, I personally doubt that there's some fundamental property about human life that we haven't noticed yet, like some fundamental connection to other matter.

Simply because there's no evidence that our primitive understanding about what is life, has fundamentally changed in history. I guess a few thousand years ago people understood that we, plants and animals are alive and rocks are not and we still think the same. (nature religions aside)

So if there was no shift in understanding for such a long time, why should we now realize we are part of something a part from an eco system?

I think it meant that even if life started itself accidentally by some unbelievably slim chance, this could happen somewhere else as well simply because the dice are rolled that often.

That might be true, but we have no basis the probability of how rare life is so we can't say it is. We may assume the probability is high enough that it happens often in trillions of chances, but if the probability is one in a quintillion then we're simply wrong.

Humans are incredibly bad at thinking about both probability and thinking about large numbers, so when we combine the two we're likely to be quite wrong.

Almost certainly there is more life out there somewhere. But if the level of rarity is “for every billion years, it happens once in every thousand galaxies” rare, then unless FTL travel is real humanity will probably never get to see it. And until we see a second example, we can’t begin to calculate the level of rarity.

But it’s also not like we’ve looked at enough of our galaxy to say it’s rare either. We just don’t know.

> It’s worth remembering that there is not one single shred of evidence that life has ever existed anywhere in the observable universe but Earth.

I’m curious how your epistemology is working here. It seems to me that this will also be true in the future if we have found life on a hundred other planets. There still won’t be a shred of evidence of life anywhere else, and we still won’t have the faintest estimate of how likely it is to occur, right?

idk, I think if we see even simple life at multiple points in our own system that we can increase our expectations for the prevalence of life very significantly.

And of course given how vast and indifferent to life the universe is, life would still be vanishingly rare in the universe. It's going to be always precious and a gem.

I agree, if — that’s an enormous “if”.

But it’s actually possible to explore our solar system! We’ve been at it since the 70s!

Yes and I’m glad we’re doing it! No life or fossilized remains of life of any kind has yet been found.

Have we sent up any archeological tools for sample prep and whatnot? Can’t find what we don’t look for, no?

Yup! We've sampled the Moon a number of times, and we're currently trying to figure out how to get one back from Mars...

https://mars.nasa.gov/msr/

Why? That could just mean our solar gave rise to life and not earth alone. Still don’t see why that increases the odds outside of our solar system

If it can spread between planets, it could conceivably spread between stars.

If, in a volume of space, there are N exoplanets and 100 spontaneously created life, then I’d crudely estimate the probability of life at 100/N for a given exoplanet.

Currently, we have only an upper limit on the probability and barely even that. All observations are consistent with a probability less that 10^-40, meaning it certainly wouldn’t happen a second time in the observable universe.

How many exoplanets would you say we have proven have no life? You imply 10^40 exoplanets are known to harbor no life. That is probably vastly more than the number of planets in the observable universe (something in the wide region of 10^20 to 10^25).

Something like 5,000 exoplanets have even been discovered. We can’t cross off many of those as certainly lacking life.

I’m certainly not claiming the actual probability is 10^-40 , only using this as an example consistent with an upper limit, which probability would imply life has not arisen a second time in the observable universe. Actually this is way overkill — as you say, even if the probability is as high as 10^-25, life on Earth is still probably the only instance in observable universe. The point is that we have no idea what this all important parameter is.

Our upper limit is something like 10^-1. After all, there is life on earth! Our lower limit is 10^-25 or so.

Why pick the lower limit? Existence of life on earth is extremely powerful evidence.

Ah, but in my opinion we can't call 10^-25 a lower limit since, if life didn't occur in this collection of planets, we wouldn't be here asking the question in the first place!

You've not accounted for the tiny number of observations that we've made nor the limited power of our observations. We're not even sure if life existed on the planet literally next to us, let alone these exoplanets. Otherwise I could argue that all observations are consistent with a probability less than 10^-10 or 10^-20 or any other number I feel like.

Ask yourself this, from how many planets in the universe would you be able to observe life on Earth?

the epistemology rests on how you construct the question, and the underlying logic.

"Does life exist anywhere besides earth" is a very different question than "does life exist outside these 100 planets". Because they are different questions, the relevancy of data and hypotheses are different.

Using this same logic (in an ad absurdum context) we could also say you will never die because no one anywhere has any evidence that you have. That doesn’t falsify your statement, but using ad absurdum shows a statement is not true in every context. I tend to think that shows less conclusion and more investigation may be warranted. That’s how I think of it, but I could be off base and I’m open to being mostly if not entirely wrong.

We have pretty good explanations for why people die and why we expect everyone alive today to die unless we acquire new knowledge that enables us to prevent it.

The God of the gaps.

People are reacting negatively to your comment, the reason is that however accurate your complaint may be about most such reporting (IMO you are correct), you have chosen to attach it to this article. I find no evidence in this article of “tone implying life is about to turn up”.

I think you have misread the tone. The article certainly has a tone of excitement throughout. But it’s excitement for further knowledge, in general.

Of the possibility of life showing up elsewhere, it says only this: “Scientists are still a long way from answering whether life could originate on Enceladus”

Fair enough. On the other hand, to my ear the title "NASA finds life-sparking energy source and molecule" sets the tone, as though life was sparked, or that we even know could be sparked by the presence of these ingredients with some degree of confidence.

Life is much more than a mix of ingredients. A dead bacteria cell has all the ingredients needed for life, but is not alive.

Good point, I had glossed over the title. That is definitely clickbait, “life-sparking” is not the same as “potential life precursor”. The rest of the article seems unusually restrained, though.

Sure, I don’t think that’s lost on anyone. The headline of “life found outside earth” is going to be a big deal.

But I also think we are zeroing in on the inevitable outcome. The math of probability and the simple components to life make it seem pretty likely we’ll get there unless there is something more fundamental that hasn’t been seen yet.

We haven’t reproduced proto-life yet, but we also don’t have millions of years and a planet sized laboratory at our disposal.

Don't mean to pick on words, but your statement that "the math of probability and the simple components to life" makes life elsewhere an "inevitable outcome" proves my point that the dialogue around this topic is currently distorted. The probability of life arising from simple components is totally unknown. Equally likely, sparking life requires a combinatoric threading of a needle to the tune of 10^-25 even when all ingredients are gathered in proximity.

I prefer the glass half full view of possibility is all. No one has 100% certainty that life exists elsewhere, but its certainly higher than 0% certainty.

For me this is nothing but a mental perspective. Historically we trended toward a very strict heliocentric view of the known universe, to the point that evidence was ignored. I would like to stay away from that side of scientific curiosity and keep wondering and exploring. It doesn't negate what you're saying at all, but its certainly more optimistic.

> It’s worth remembering that there is not one single shred of evidence that life has ever existed anywhere in the observable universe but Earth.

It is hard for me to believe that in the mind boggling vastness of space and time, we are the sole singularity in the history of the universe.

Many things which are hard to believe are nevertheless true.

Sure, but in this case, we don't know.

When Everest was first measured, it was exactly 29,000 feet.

They figured no one would believe this, so they told people it was 29,002 feet

Sometimes things just are, regardless of what we expect.

Waugh is sometimes playfully credited with being "the first person to put two feet on top of Mount Everest".

The "observable" universe is very small. We can take a look at things that are at the "ebd" of the universe, but those happened multiple billion years ago. Earth itself is 2-3 billion years old and life in terms of mammals is is a couple hundred million years old.

So to say, there may be another earth with human-like life. But it's so far away, life isn't here (therefore not observable) and life may already be gone there (but it will take another billion years until we can observe it).

But we barely know anything about how life on our own works, much less came about. We barely know anything concrete about anything.

We’re just hairless (mostly) apes running amok having discovered how to trap fire inside little bits of copper and sand.

We’ll look as primitive to our descendants in 10,000 years as our ancestors of 10,000 years look to us.

I guess I’m saying that, I think, our views on the universe and life are only very slightly more accurate than they were when those ancestors were painting what they saw in caves.

I think our hubris tells us we understand far more than we do. I think if you take that into account, the possibility for life existing elsewhere in the universe is an absolute fact.

I surmise, that for us to think that we’re the only sentient life in the unimaginably vast universe is the ultimate manifestation of our drive for self-preservation.

We want to survive and propagate our DNA above all else, therefor we must be vigilant against all threats, therefor if we consider ourselves at the center of the universe, we can be sure to never neglect anything that might indeed be a threat.

The problem with this instinct is that it clouds our conscious judgement into thinking that the universe does indeed revolve around us and then we make conclusions according to that fallacy.

I think life in the universe is as ubiquitous as rocks. It’s everywhere in all manner of forms and sophistication. We just won’t have the tools to see or hear it for maybe a couple hundred years or so. But once we do, we’ll have a chuckle at how we could be so arrogant as a species to ever think we were alone.

Is it actually worth remembering? I don't know, man. It kind of sounds not worth remembering if I'm honest. It's kind of like telling us that there is not one single shred of evidence that artificial flight has ever existed or that exoplanets have ever existed or anything of the sort.

Sure, that's the base case. It's not "worth remembering" at all. It's as much worth remembering as the fact that my clothes are in the dryer right now.

I think it's "worth remembering" precisely because it seems not to be the base case anymore! To see this, just look at all the expressions of confidence in life's ubiquity throughout the rest of this thread!

> Moreover, no one has succeeded in hatching living matter from non living matter and we must honestly say we do not know how this process came about or the faintest estimate of how likely it is to occur (despite much speculation

Just want to comment on this point. The research in this field is pretty esoteric. It doesn't really benefit us to understand how this process came about (ie, there is little practical gain here, no medical advancements or otherwise), and moreover it requires a simulation which can estimate behavior over hundreds of millions of years. The usefulness of cracking the early earth/life creation part of our history is really not immediately clear, and thus research is limited.

That said, the Miller-Urey experiment (https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment) showed animo acids organizing over conditions similar to early earth, and a follow up experiment dubbed Planet Simulator (https://en.wikipedia.org/wiki/Planet_Simulator) was extended to show the organization of protocells as part of this early earth environment.

It seems only a matter of time before science can connect the dots along the rest of the hundreds of millions of years regarding this process to show the line between chemical young earth evolving to be biological.

As an aside, why do you think it is "important to remember" that we haven't found life or that we don't fully understand the process by which biology evolved from chemistry? Why exactly is it "important to remember" such things?

It is “important to remember” precisely because these days people are not remembering this and speak with a sense of inevitability about discovering life elsewhere, which sense of inevitability is totally unsupported. I may gently point out, your own post says “it is only a matter of time before science can connect the dots”, reflecting this (in my view) distorted sense. The abiogenesis research you cite is absolutely worthwhile, but it is not even clear if it is in the right direction and certainly far, far from successfully sparking the sustained chain reaction of life. To my eye, equally consistent (as some different research may suggest) is that a combinatorial needle must be threaded to the tune of p < 10^-23 per exoplanet, making it unlikely to happen again in our observable universe.

Edit: to cite just the one “combinatorial abiogenesis” reference, see for instance https://www.nature.com/articles/s41598-020-58060-0

> It is “important to remember” precisely because these days people are not remembering this and speak with a sense of inevitability about discovering life elsewhere

Could you expand on this a bit. Whether someone speaks with a sense of inevitability or not, why is it important either way? Why is it "important" to remind people we haven't (yet) found life on other planets?

Why are the existing gaps in abiogenesis "important" to point out?

What is so "important" about these things?

Well, first, I take it to be an axiomatic goal of science to believe that which is true, disbelieve that which is false and to be agnostic about things we have no evidence about; I.e to calibrate our model of world to the world as it is.

But, further, I’ve seen what happens when a subfield reports its findings in a way that misleadingly raises expectations of a titanic discovery just around the corner. When the discovery fails to materialize, over-optimism curdles into its opposite, over-cynicism. Better to calibrate expectations accurately — slow and steady wins the race.

The lack of interest in abiogenesis in most circles is truly outstanding.

And here’s another thing. With how difficult it is to probe new physics, we stand to do a lot more research by simply inspecting all the observable universe than trying to build colliders.

Finding a new particle doesn't necessarily threaten strictly up held religious beliefs like finding life somewhere other than this rock

Catholics officially believe in aliens, and that we should save them (if they weren’t visited by Jesus)

Jews wouldn’t care either. Don’t know about Muslims, but it’s not threatening to the other Abrahamic religions

> Catholics officially believe in aliens,

A definitive position on the existence of aliens is not part of the Catholic faith.

But, the church admits the possibility and church institutions have done some explorations about what the implications of such contact might be, and how Catholic doctrine might apply to different possibilities.

Apparently you are correct!

https://www.catholic.com/qa/whats-the-catholic-position-on-t...

Catholics officially believe in aliens, and that we should save them (if they weren’t visited by Jesus)

Reminds me of the punch line to an amusing first-contact cartoon, one that makes the (unstated) previous line easy enough to guess: "Yeah, he comes by every couple of years. We gave him a nice box of chocolates when he first visited. What'd you guys do?"

Muslims recite that Allah is “lord of all the worlds” every day. Think they’ll be fine. This is true of every religion I think, it’s only the non religious projecting that state it would “upend widely held beliefs”

Inspecting the universe can be a lot harder than building colliders. Observing some of the short-lived high-energy particles would require shipping detectors to a high-energy location like the sun, then pulling a signal from all that noise.

There's quite a bit of interest; e.g. ex-colleagues of mine have spent lots of effort on refining the 'chemoton' model. I think it's a fascinating subject.

"The basic assumption of the model is that life should fundamentally and essentially have three properties: metabolism, self-replication, and a bilipid membrane.[3] The metabolic and replication functions together form an autocatalytic subsystem necessary for the basic functions of life, and a membrane encloses this subsystem to separate it from the surrounding environment. Therefore, any system having such properties may be regarded as alive, and it will be subjected to natural selection and contain a self-sustaining cellular information."

https://en.wikipedia.org/wiki/Chemoton

https://www.nationalgeographic.com/premium/article/he-may-ha...

Bilipid membrane is not necessary for life - life may have evolved inside naturally occurring bacteria sized pores inside inorganic material.

It's like saying that mathematicians are uninterested in the Collatz conjecture. Scientists usually work on problems where they have a reasonable expectation of making progress. Attempts to replicate abiogenesis so far have been largely haphazard, with ill-defined criteria of what progress means.

Life almost certainly exists elsewhere in the universe (particularly if you consider that which is beyond what we define as ”observable”). As others have commented, it’s too large for it not to exist.

However, it does seem extremely rare and could be so rare that it doesn't exist in the observable universe (it's almost certainly not in our Local Bubble).

It is interesting to also think about the likelihood of "intelligent" life. Because while basic, simple organisms are bound to appear somewhere else considering the universe's vastness, the idea that they could develop this intelligence and self-awareness is another big leap that doesn't seem like it necessarily needs to happen wherever life is happening.

> But, for decades, I’ve been reading reports of the discovery of evidence for the trappings of life elsewhere: water and organics and “habitable” exoplanets. These are valuable discoveries, but the tone of the reports suggest they imply life is about to turn up.

I agree that life is not very likely. We appear to have gotten lucky. Aka, “the rare earth hypothesis.” As far as habitable zones, both Mars and Venus are in the habitable zone of our solar system, and they appear to be barren.

But do not despair! A new approach has been identified. Look much wider and farther, and as opposed to biosignatures, we should look for signs of technosignatures. This would be much harder to mistake for natural chemical processes.

Choza et al. (2023; breakthrough listen search for extra-galactic technosignatures) - https://seti.berkeley.edu/galaxies/choza.pdf

https://youtu.be/2RQWiJ0x_R4?t=121

Technosignatures in general seem to be a good idea to satiate our curiosity.

https://youtu.be/BtSn_PTQtds?t=1966

The universe is 13 billion years old.

Planet earth is 4.5 billion years old.

Life on earth started 3.7 billion years ago.

We sent our first radio wave just 125 years ago.

Probably life is not than unusual and we just don’t have a way to verify this (yet).

What is this probability based upon?

The probability is based on the fact that everywhere we look, we find building blocks of life, life started on earth basically as soon as it could have, life exists at all and is capable of asking said question, life is remarkably adaptable, we estimate billions of earth like planets just in our galaxy.

I know that there is a burning desire to think we’re special, but the truth of the matter is that we’re almost definitely not.

We are the universe though. I.e. the universe has at least one mind (yours) and it thinks that it is special :)

The three and a half facts you listed (life may have started earlier if it came to Earth from Mars or elsewhere) do not logically lead to your conclusion.

We’re looking for the shreds of evidence. What would you prefer people do?

I think you enjoy the top comment for the phrase

>> It’s worth remembering that there is not one single shred of evidence that life has ever existed anywhere in the observable universe but Earth.

There is nothing like the blunt expanse of a simple fact to sharpen the mind. If the consequent should be that, based on the evidence we are alone and therefore first, I postulate an obligation to seed the cult of Apollo throughout the universe -- the god of the one thing without which life itself would be a mistake.

I leave it to HN to fuck up the answer.

What a fun thread. I've always heard this as one of The Great Filters related to the Fermi paradox. FWIW the wikipedia for the Fermi paradox even mentions that:

> The most commonly agreed-upon low probability event is abiogenesis

...which I read as saying that the most commonly agreed-upon reason we haven't found life anywhere else yet is because we _are_ special and abiogenesis is the rare event (the great filter).

All the various great filter theories are pretty fun reading.

"It’s worth remembering that there is not one single shred of evidence that life has ever existed anywhere in the observable universe but Earth"

Dude considering we're barely scratching the surface of the scratch on the scratch of the surface, I'd say this is really arrogant. We haven't found anything because our universe is a haystack and we're looking for the quark of a needle in that haystack. Perspective.

This is true. It is also true that we have found “not one single shred of evidence that life has ever existed anywhere in the observable universe but Earth”.

What you say is true, but thinking of ourselves as the only life feels like hubris. It reminds me of geocentrism.

I happen to agree with you. I am in the "we are it" crowd but still agree with should explore.

I am too - I think it’s the moon plus Jupiter that is extremely unique and makes complex life possible

I also think it’s a lot of pressure if it’s only us, so it’s easier to imagine we’re one of billions.

Honestly, honestly think it’s just us. Maybe not in the entire universe but in our local cluster.

Personally I think articles like this are actually the shreds of evidence you say don't exist.

If there isn't life on Enceladus this is still incredibly exciting because then it might make the perfect lab for us to put life and study how it evolves.

What you are touching upon, imo, is the idea that science is NOT actually some independent, objective means of understanding the world, in contrast to religious thinking. Whereas the reality is that science is actually a belief based system, that cloaks itself in a (thin) veneer of objectivity. The scientific method is venerated but not applied personally.

So, the reality is that adherents accept a reality intermediated for them by priests/scientists (and journals, trusted sources). Adherents talk about truth/reality while having little or no personal experience of the matter at hand. It is group behaviour, evidence is paid lip service to but there is very little critical thought or assessment of said 'evidence' by any individual adherents. When the scientific authorities make a pronouncement, this is simply accepted.

Religion. Believers.

But the other possibility that some intelligent super being created life on Earth is even bizarre. If that’s what you believe then who created that creator? You can go on and on, there is no end to this question. That very first creator must have come out from a “non living” thing.

Your parent comment isn't suggesting creationism, just pointing out that the beginning of life could be an astronomically rare event.

The math is the evidence. The math is not in your naysaying favor.

I can't even conceive what evidence maths could provide!

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