What do you think is the most likely explanation for the Fermi paradox?

[Noclevername]

Do you think Venus is less likely for life than Mars? Why?

I do, primarily because known upper atmosphere life is largely dependent on interaction with the greater biosphere. Venus' conditions would seem to make such a niche much more tenuous.

Underground and Arctic life that we know of has direct access to moisture and minerals and protections which give such life forms something of an advantage, IMO.

Glad you mentioned sunlight and abiogenesis.

It's true that the ice moons including Titan get a lower flux of energy from the sun than Earth or Mars.

But due to the composition of Titan's atmosphere (hydrogenating rather than oxidising), it's able to turn a substantial part of the solar energy it gets into chemical energy. E.g. by producing acetylene (C₂H₂) alongside free hydrogen (H₂) in its ionosphere. This is comparable to what happened in the Urey/Miller experiment, and to what presumably happened in Earth's atmosphere 4 billion years ago, when abiogenesis occurred.

That's one reason I think Titan may tell us more than Mars about questions like how common or uncommon abiogenesis is throughout the Galaxy.

Well, it would tell us something about organic chemistry under cryo conditions. We still have no idea if such conditions could originate life. As you said, it takes more than the right molecules.

I think Enceladus and Europa might be places to watch. They're thought to have oxygenation from radiation flux on the ice, making for plenty of potential chemical "oomph".

[Van Rijn]

I would put Mars first because, based on the evidence we have, conditions underground in some places could be able to support Earth life (at least some single cell life). It has a decent chance of having earthlike microenvironments. I’m not aware of anything similar elsewhere. Europa’s possible oceans would likely be very different from Earth environments, for example.

[Colin Robinson]

I do, primarily because known upper atmosphere life is largely dependent on interaction with the greater biosphere. Venus' conditions would seem to make such a niche much more tenuous.

Underground and Arctic life that we know of has direct access to moisture and minerals and protections which give such life forms something of an advantage, IMO.





Well, it would tell us something about organic chemistry under cryo conditions. We still have no idea if such conditions could originate life. As you said, it takes more than the right molecules.

I think Enceladus and Europa might be places to watch. They're thought to have oxygenation from radiation flux on the ice, making for plenty of potential chemical "oomph".

I'd agree that Enceladus and Europa are intriguing worlds. They are two more reasons why Mars should not be thought of as the only place in the Solar System where we might conceivably find extraterrestrial life.

But what about the point you made in your last message, about relevance of sunshine to life? How much energy from the Sun reaches the subsurface ocean of Europa?

[Colin Robinson]

I would put Mars first because, based on the evidence we have, conditions underground in some places could be able to support Earth life (at least some single cell life). It has a decent chance of having earthlike microenvironments. I’m not aware of anything similar elsewhere.

That line of argument is presumably why the idea of life on Mars gets so much attention.

But we don't know whether the sort of Earthlike microenvironments which may exist on Mars are enough for a living ecosystem to function.

David Grinspoon thinks microenvironments may not be enough. Like James Lovelock, he sees life on Earth as the property of a global biosphere, in which living things and non-living things (such as atmospheric composition) have co-evolved, i.e. developed together.

So he expects life activity beyond Earth to be found on a planet or moon which, like Earth, is active in other ways, such as having cycles of liquid formation and evaporation, and an atmosphere which is far from chemical equilibrium.

[Van Rijn]

But we don't know whether the sort of Earthlike microenvironments which may exist on Mars are enough for a living ecosystem to function.

Of course, but I thought the discussion was about how one would order worlds in terms of most likely to least likely to have habitable environments. I’d put Mars at the top because, based on current evidence, it is the most likely to have microenvironments that could support some kinds of earth life. Whereas for others we generally have to posit various significant differences from Earth life to survive anywhere.

[Noclevername]

I'd agree that Enceladus and Europa are intriguing worlds. They are two more reasons why Mars should not be thought of as the only place in the Solar System where we might conceivably find extraterrestrial life.

But what about the point you made in your last message, about relevance of sunshine to life? How much energy from the Sun reaches the subsurface ocean of Europa?

I never said it was the only place.

I consider Mars more likely than the ice moons specifically because of sunlight. But the moons do have alternative sources of energy.

[Colin Robinson]

Of course, but I thought the discussion was about how one would order worlds in terms of most likely to least likely to have habitable environments. I’d put Mars at the top because, based on current evidence, it is the most likely to have microenvironments that could support some kinds of earth life. Whereas for others we generally have to posit various significant differences from Earth life to survive anywhere.

Have you seen this essay by Peter Vickers of Durham University — Alien life is out there, but our theories are probably steering us away from it?

He suggests that perhaps we've been thinking about life and habitability too narrowly. "Under-explored areas need exploring, and we can’t know in advance what we will find."

It seems to me that Venus and Titan are under-explored in comparison with Mars.

Over the last half century, study of the Solar System, and of exo-planets, has shown that planetary environments are very diverse.

Other worlds have all sorts of significant differences from Earth. So perhaps we should be open to the possibility that life on other worlds has significant differences from Earth life?

Diversity of biospheres may explain why we don't see colonists from other worlds here on Earth.

A very diverse Galaxy means that would-be colonists would face a different environmental challenge on every world they tried to colonise.

The challenges may be too great for colonisation to work at all; or may mean that even the most successful colonising life-forms spread through the Galaxy at a rate vastly slower than predicted by people like Michael Hart and Robin Hanson.

[Noclevername]

Ideally we could explore everywhere in detail and our resources could be allocated by the experts' best judgement.

As far as colonizing, I agree trying to integrate yourself into an alien biosphere would be much harder than establishing a closed artificial one. Even given best possible compatibility, there's sure to be major differences.

[Roger E. Moore]

Earth's Habitability Today Is Basically Due to Luck, Millions of Simulations Show (implying advanced life elsewhere is unlikely).

https://www.sciencealert.com/are-we-...lions-of-years

[cosmocrazy]

Earth's Habitability Today Is Basically Due to Luck, Millions of Simulations Show (implying advanced life elsewhere is unlikely).

https://www.sciencealert.com/are-we-...lions-of-years

Though my personal opinion favours this logic, I'm also aware that there are potential flaws in it that could have a significant impact on the outcome of such experimental models. The single most obvious one, is that we only have one example to use as our base criteria.
Additional to that is that we currently observe the universe to be a finite size and age, this could be accurate or vastly under estimated. Next is many of the parameters inputted into these models are estimates and/or best guesses, based on our current understanding.

Its this ambiguity that keeps me positive, in the hope that we do discover ET life and even better we discover technological ET.

[Noclevername]

Though my personal opinion favours this logic, I'm also aware that there are potential flaws in it that could have a significant impact on the outcome of such experimental models. The single most obvious one, is that we only have one example to use as our base criteria.
Additional to that is that we currently observe the universe to be a finite size and age, this could be accurate or vastly under estimated. Next is many of the parameters inputted into these models are estimates and/or best guesses, based on our current understanding.

Its this ambiguity that keeps me positive, in the hope that we do discover ET life and even better we discover technological ET.

While I agree that the limits of the simulation are self evident, and my own sense is that intelligent life is rare, I tend to draw the conclusion that it's unlikely that we'll find life in my own time. There's just too many necessary make-or-break variables and the Universe, even if it's finite (which isn't testable), is still far too big to make discovering intelligent life outside our Solar System seem like a realistic goal.

[Noclevername]

Added to that, if the Copernican principle has any value at all, then we're "about average" in our location in the Universe too. So life would then be fairly evenly distributed, making nearby neighbors unlikely.

[Roger E. Moore]

BIG QUESTION: Is there anything that we can definitively say about what we are looking for, given this thread's title? In other words, what ARE we looking for, exactly?

If we are looking for intelligent life, how can we tell if it is intelligent? If we want intelligent life that communicates with us, what can we definitely say about what that life will be like?

[Noclevername]

BIG QUESTION: Is there anything that we can definitively say about what we are looking for, given this thread's title? In other words, what ARE we looking for, exactly?

If we are looking for intelligent life, how can we tell if it is intelligent? If we want intelligent life that communicates with us, what can we definitely say about what that life will be like?

We can say nothing definite. It'll be a judgement call. There's only one template to examine and the outer parameters are unclear.

For all we know "they" have been trying to communicate and we haven't recognized it. (Cue X Files theme song)

[Roger E. Moore]

We can say nothing definite. It'll be a judgement call. There's only one template to examine and the outer parameters are unclear.

Why even have this thread, then? If nothing can be said except empty possibilities, why bother to talk about the Fermi question at all? It seems some harder ground can be established if we are to examine the paradox.

[Van Rijn]

Why even have this thread, then? If nothing can be said except empty possibilities, why bother to talk about the Fermi question at all?

Because people like to talk about it. It’s far from the only subject where nothing solid can be said but people have pet positions and like to argue about them.

It seems some harder ground can be established if we are to examine the paradox.

What harder ground are you referring to?

[Noclevername]

Why even have this thread, then? If nothing can be said except empty possibilities, why bother to talk about the Fermi question at all? It seems some harder ground can be established if we are to examine the paradox.

We have a starting point, a center to build from; similarity with our kind of life. We just don't know the boundaries of where to end our search.

And I echo Van Rijn's question, what is the harder ground?

[Roger E. Moore]

What harder ground are you referring to?

How could an extraterrestrial civilization communicate with us over interstellar distances? Is there a simple and cheap way to do so?
Does the fact that certain aliens might communicate with us over interstellar distances imply something about them, such as they do not live entirely underground or undersea?
Could there be a method of communicating that only civilizations of a certain technical ability can manage, such as the difference between sending radio waves, laser beams, or coherent beams of neutrons or more exotic particles?
Is it true that nothing can be learned by studying an example of one (humans)? Can we at least postulate that evolution is likely to be encountered with alien life?

[Roger E. Moore]

What about the Solaris dilemma, from Stanislaw Lem's book "Solaris"? Is it even imaginable that we would encounter alien life that appears intelligent in some way, but cannot possibly be communicated with? Can we possibly picture a type of intelligence that we would have trouble recognizing as intelligent?

I am going here with the idea that we can predict nothing from looking at ourselves as an example of a communicative intelligent technological species.

[Roger E. Moore]

I guess I was thinking that through a process of logical elimination (e.g., the aliens cannot be incorporeal) one could develop a picture of what a communicative alien is like. Then, ask why this race would not wish to communicate or would be unable to communicate with anyone.

I think from my perspective, intelligence is just extremely rare, and technological intelligence is rarer, and the ability to communicate over interstellar distances is even rarer. Cultural and psychological reasons for not wishing to communicate are fun to speculate about, but in the realm of something "harder", if evolution is commonplace in life across the universe, then the eat-or-be-eaten idea is also common, and fear of predators might be an issue.

[Noclevername]

I guess I was thinking that through a process of logical elimination (e.g., the aliens cannot be incorporeal) one could develop a picture of what a communicative alien is like.

Incorporeal is a nebulous term (pun). Would it apply to life made of cold plasma? Of exotic particles? Structural spacetime? Extra dimensions? None of these long shots are really able to be proven or ruled out because at present we have no way to test for them.

We know of only one life domain that exists, using amino acids and other complex organic molecules in a liquid water solvent. We can use us as a starting point of similarity and work outward from there. But there's no clear picture of where to end, what the boundaries should be. How different is too different to be life? How different is too different to be a mind? How different is too different to be meaningful communication?

Then, ask why this race would not wish to communicate or would be unable to communicate with anyone.

We can come up with a million scenarios as to why, (this thread is almost there! ) but there's just no information to clarify anything.

We know it would be hard, probably a non-trivial undertaking, to send a clear, coherent electromagnetic signal more than a tiny fraction of a Galaxy away. We can assume fairly surely that making a message (even "We're here!") understandable and distinct from a natural phenomenon is not simple. Even within our own species, many forms of communication are context-specific, easily misinterpreted or mutually incomprehensible. See the Star Trek TNG episode Darmok as a fictional example; the "universal" translators were next to useless without cultural references.

And that's just for signals we can detect using current technology!

[Colin Robinson]

I guess I was thinking that through a process of logical elimination (e.g., the aliens cannot be incorporeal) one could develop a picture of what a communicative alien is like. Then, ask why this race would not wish to communicate or would be unable to communicate with anyone.

I think from my perspective, intelligence is just extremely rare, and technological intelligence is rarer, and the ability to communicate over interstellar distances is even rarer. Cultural and psychological reasons for not wishing to communicate are fun to speculate about, but in the realm of something "harder", if evolution is commonplace in life across the universe, then the eat-or-be-eaten idea is also common, and fear of predators might be an issue.

We humans have put a lot more time and effort into listening for communications (SETI) than in sending out communications to others (METI). One reason is concern with potential dangers of sending out messages. Another reason is that SETI seems to offer a pay-off in knowledge for our own species, whereas the initial pay-off of METI would go to someone else... And it seems we humans are less interested in providing free information to other intelligent species than in receiving information from them.

Maybe other species are similar to us in that respect — more interested in getting information for themselves than in sending it out to others...

Which is why we aren't hearing from them...

[Tom Mazanec]

Maybe the ants have the explanation?
https://xkcd.com/638/

[Noclevername]

Getting back to the principle of mediocrity, we simply can't say anything about how common or rare we are. The results would look the same to us if life were a unique local fluke, or a universally distributed constant; we would exist either way. It makes no sense to call anything "typical" in an endlessly varied Universe.

Until and unless we detect other occurrences of life to establish a baseline, we're an isolated case. Maybe the only one, maybe one of trillions, we just don't know.

[cosmocrazy]

What about the Solaris dilemma, from Stanislaw Lem's book "Solaris"? Is it even imaginable that we would encounter alien life that appears intelligent in some way, but cannot possibly be communicated with? Can we possibly picture a type of intelligence that we would have trouble recognizing as intelligent?

I am going here with the idea that we can predict nothing from looking at ourselves as an example of a communicative intelligent technological species.

Well, we have "intelligent" species here on our own planet that we can't have any meaningful communication with e.g octopi, dolphins... so yeah, there is a very good possibility that if there is other life out there that is intelligent we may not recognise it as such because it differs so much from what we consider as life. The universe could be teeming with intelligent life that may not be technological. So unless we visited their planet, we would never even have a chance at communication in the first place.

[cosmocrazy]

Getting back to the principle of mediocrity, we simply can't say anything about how common or rare we are. The results would look the same to us if life were a unique local fluke, or a universally distributed constant; we would exist either way. It makes no sense to call anything "typical" in an endlessly varied Universe.

Until and unless we detect other occurrences of life to establish a baseline, we're an isolated case. Maybe the only one, maybe one of trillions, we just don't know.

Yes, and to make things even tougher, even if there is/was/will be life similar to our own the chances of it being around at the same time and with the same technological capability as us is unlikely.

[Noclevername]

Well, we have "intelligent" species here on our own planet that we can't have any meaningful communication with e.g octopi, dolphins... so yeah, there is a very good possibility that if there is other life out there that is intelligent we may not recognise it as such because it differs so much from what we consider as life

Haven't we already communicated with dolphins? We're also in the process of learning today about interpreting how other undomesticated species communicate, with birdsong etc. Rudimentary communication, but communication nevertheless.

. The universe could be teeming with intelligent life that may not be technological. So unless we visited their planet, we would never even have a chance at communication in the first place.

Well, the question arises, would a species like that have enough common referents to understand us more than vaguely? It's now thought that our tool use long predated language development and may have driven our evolution in complex ways. Would they have better understanding of such an alien concept than an octopus?

[7cscb]

Why even have this thread, then? If nothing can be said except empty possibilities, why bother to talk about the Fermi question at all? It seems some harder ground can be established if we are to examine the paradox.

Hi Roger,

I suppose the unease related to SETI is that we have vague definitions for Life and Intelligence.

While we are hampered by the above, it happens that we are finally getting astronomical data unimaginable just a few decades ago. For the first time, actual data is being used while speculatively contemplating the paradoxes you mention.

And new telescopes and techniques promise even more. It will not be long till we can detect telltale chemical signs of life through atmospheres at interstellar distances. While such a find would be exciting, it will be just as mysterious to find nothing as the count of exoplanets increases.

cheers,

[Colin Robinson]

Maybe life is widespread, but technological life is rare. Not because it doesn't crop up, but because it never survives very long...

What if human-level intelligence is like the strength it takes to grab a pillar of a classical temple and pull the roof down on your own head? The temple in this metaphor being the ecosystem of your planet...

This may not be a pleasant hypothesis. But it's a possible one.

[Colin Robinson]

Haven't we already communicated with dolphins? We're also in the process of learning today about interpreting how other undomesticated species communicate, with birdsong etc. Rudimentary communication, but communication nevertheless.

Our communications with dolphins are rudimentary. Their communications with each other may be far from rudimentary, as we're only beginning to understand how they communicate. It's fairly well established that individual dolphins have "signature whistles" comparable to names, but what else they do with their whistling is still an open question.

I'd also make the point that when studying dolphins and other Earth animals, including birds, we know a lot of things that we wouldn't necessarily know about an ET species that we got some sort of message from. For instance we know what shape a dolphin is, how it moves around, what it feeds on, how it reproduces, the size of its social groups... and all these things are potentially clues to what dolphins might communicate about...