An interesting thought

[eburacum45]

Oxygen is a good biomarker on Earth. If a planet has oxygen and a rocky surface, it may, or may not have life. Oxygen is a reactive element and on Earth, it remains in the atmosphere by being constantly renewed.

Undiscovered exo-planetary processes may well be possible for renewing atmospheric oxygen, and may also not necessarily be related, in the slightest, to the presence of exo-life.

Oxygen is an element which can exist in many forms .. volumes have been found in space, and elsewhere.

What does it mean if it is discovered on an exo-planet if the interpretation model has no empirical basis ?

To be honest, if oxygen is discovered in the atmosphere of an exoplanet, my first thought isn't 'Aha- life!' it is 'Aha- photodissociation of water'. On a planet coverd in water oxygen would be produced by the effect of light on water vapour. Hydrogen would then be lost by Jeans escape.

But on Earth this process is slower than the rate of absorption of oxygen by the crust, so without photosynthesis the oxygen produced by photodissociation would be minimal.

Waterworlds, and icy worlds like Europa, could quite likely have oxygen atmospheres. In fact O₂ is present on many of the icy moons of the Solar system.

According to A. Leger a better biomarker would be ozone.
see
http://arxiv.org/ftp/astro-ph/papers/0308/0308324.pdf

The only way to have a significant amount of O₃ in the atmosphere spectrum is that O₂ is produced at low altitude, eg by biological photosynthesis...

There may be abiotic mechanisms to produce and retain O₃ , but its detection in an exoplanetary atmosphere is likely to be an encouraging sign.

[Extrasolar]

Or maybe there are very complex life-forms on other worlds, but they are so different from us (and from each other) that terms like "intelligence" and "advanced" are hardly applicable?

While I understand the idea of there being lifeforms so different from us that we fail to recognize it in the first place, a measure of intelligence or advancement that is similar to ours or similar to what we have been (simple tool makers) would be obvious. Mathematics is universal, and evidence of its use would be intelligence.

[Colin Robinson]

Well, this idea wasn't so much "directed" as " microscopic survivor goes native." though I have heard of that as well, both as a serious discussion and as a basis for science fiction.

True. Not so much "directed panspermia" as "accidental panspermia", a scenario discussed by the astrophysicist Thomas Gold.

[Colin Robinson]

While I understand the idea of there being lifeforms so different from us that we fail to recognize it in the first place,

True, humans might conceivably mistake an unfamiliar life-form for a mineral. This is a somewhat different scenario that what I had in mind though.

a measure of intelligence or advancement that is similar to ours or similar to what we have been (simple tool makers) would be obvious.

I'd agree that their intelligence might be obvious, if they did stuff that was obviously similar to what we do today, or to what we did in the stone age.

But consider a scenario like this...

Astronomers detect an exoplanet that looks promising for life. An interstellar space probe is sent to have a look. The probe arrives, sends back pictures of what are obviously motile living things – an abundant species, though an unfamiliar one – the creatures resemble vertebrates in certain respects, but other things about them are more like insects, molluscs or cnidarians. The probe also finds and photographs structures which the creatures have made, and in which they live: weird structures, but impressively large and stable.

The question arises: Are these structures the equivalent of humans' cities? Or are they more comparable to termite mounds? Or to the great underwater structures created here on Earth by the coral polyp?

How would you go about answering such questions?

Mathematics is universal, and evidence of its use would be intelligence.

What would qualify as "evidence of its use"?

An alien organism that could construct a regular hexagon might be no more (or less) "intelligent" that a honey bee.

[Extrasolar]

True, humans might conceivably mistake an unfamiliar life-form for a mineral. This is a somewhat different scenario that what I had in mind though.



I'd agree that their intelligence might be obvious, if they did stuff that was obviously similar to what we do today, or to what we did in the stone age.

But consider a scenario like this...

Astronomers detect an exoplanet that looks promising for life. An interstellar space probe is sent to have a look. The probe arrives, sends back pictures of what are obviously motile living things – an abundant species, though an unfamiliar one – the creatures resemble vertebrates in certain respects, but other things about them are more like insects, molluscs or cnidarians. The probe also finds and photographs structures which the creatures have made, and in which they live: weird structures, but impressively large and stable.

The question arises: Are these structures the equivalent of humans' cities? Or are they more comparable to termite mounds? Or to the great underwater structures created here on Earth by the coral polyp?

How would you go about answering such questions?

Ah, yes, if the scenario is limited by information from a probe, then I can totally see that we could miss all kinds of things, including a possible knowledge of mathematics. (They could be under-dwellers that barely make a scene on the surface or a billion other scenarios). However, lets say the probe indeed finds a planet with life on it, and we go there. In that situation, I believe it would be fairly easy to tell. Complex structures require math, even if we found them beneath the ground of a mostly barren planet. A civilization would have to be very paranoid to deliberately make their society look like they don't know or use math when they really do.

What would qualify as "evidence of its use"?

An alien organism that could construct a regular hexagon might be no more (or less) "intelligent" that a honey bee.

Indeed, but it is measurable.

[Colin Robinson]

Ah, yes, if the scenario is limited by information from a probe, then I can totally see that we could miss all kinds of things, including a possible knowledge of mathematics. (They could be under-dwellers that barely make a scene on the surface or a billion other scenarios). However, lets say the probe indeed finds a planet with life on it, and we go there. In that situation, I believe it would be fairly easy to tell. Complex structures require math, even if we found them beneath the ground of a mostly barren planet.

What if we landed on a planet, observed a range of complex structures, whose design would require mathematical knowledge...

but then we did some archeology, and found that the builders of these structures had been doing the same sort of thing for hundreds of thousands of years, with no apparent change or innovation...?

[Selfsim]

What if we can't travel to any such planet, as this is beyond our range of our transit and communications technologies ?

Which happens to be real-world reality (as opposed to Sci-fi conjecture).

Regards

[Colin Robinson]

What if we can't travel to any such planet, as this is beyond our range of our transit and communications technologies ?

Then we ought to keep an open mind about what may or may not be out there.

Which happens to be real-world reality (as opposed to Sci-fi conjecture).

The OP of this thread refers to the fact that we haven't yet received any message from intelligent extra-terrestrials. This bit of negative evidence is consistent with many possibilities. All of which will remain conjectures till we know which is right.

[Extrasolar]

What if we landed on a planet, observed a range of complex structures, whose design would require mathematical knowledge...

but then we did some archeology, and found that the builders of these structures had been doing the same sort of thing for hundreds of thousands of years, with no apparent change or innovation...?

Then I would say the definition of intelligence would be applicable.

The assertion being made is:

Or maybe there are very complex life-forms on other worlds, but they are so different from us (and from each other) that terms like "intelligence" and "advanced" are hardly applicable?

I don't want to debate special scenarios, I'll only say we can only know as much as our machines tell us, and if we had some good enough to visit a civilization, then we would determine intelligence or not. It would always be applicable.

[Colin Robinson]

Then I would say the definition of intelligence would be applicable.

The assertion being made is:

I didn't make an assertion. I asked a question. To which you replied:

Mathematics is universal, and evidence of its use would be intelligence.

If so, could the concept of SETI (Search for Extraterrestrial Intelligence) be equally well expressed as SETM (Search for Extraterrestrial Mathematicians)?

[Extrasolar]

I didn't make an assertion. I asked a question. To which you replied:



If so, could the concept of SETI (Search for Extraterrestrial Intelligence) be equally well expressed as SETM (Search for Extraterrestrial Mathematicians)?

Right, the question you asked, not the assertion you made. I would say yes to the SETI question.

[ravens_cry]

Ah, yes, if the scenario is limited by information from a probe, then I can totally see that we could miss all kinds of things, including a possible knowledge of mathematics. (They could be under-dwellers that barely make a scene on the surface or a billion other scenarios). However, lets say the probe indeed finds a planet with life on it, and we go there. In that situation, I believe it would be fairly easy to tell. Complex structures require math, even if we found them beneath the ground of a mostly barren planet. A civilization would have to be very paranoid to deliberately make their society look like they don't know or use math when they really do.

Or they could be like termites,honey bees and ants on a larger scale, their individual efforts working together on some instinctual level to create what we would call "structures".
They could be using mathematics, they just might not be aware of it.

True. Not so much "directed panspermia" as "accidental panspermia", a scenario discussed by the astrophysicist Thomas Gold.

I believe there was a thread wondering if we have been doing just that with some of our probes and landers.
To be honest, my response was meant in as a humbling of the grandiose "we might be descendants of people from the sky"! to "we might be the the descendants of quasi-intestinal flora!"
Still yes, it is something to think about and I am sure many good thoughts have been thought.

[Colin Robinson]

I believe there was a thread wondering if we have been doing just that with some of our probes and landers. To be honest, my response was meant in as a humbling of the grandiose "we might be descendants of people from the sky"! to "we might be the the descendants of quasi-intestinal flora!" Still yes, it is something to think about and I am sure many good thoughts have been thought.

Our human grandiosity can benefit from a little humbling, I think.

Perhaps an even more humbling hypothesis about how life came to Earth is the "metabolism-first" one.

As if it wasn't enough to be told that our ancestors were apes, and before that reptiles, fish, microbes...

Now comes the rumor of a not-yet-living quasi-ancestor who was a cycle of mineral-catalysed chemical reactions – a bunch of carboxylic acids, four to six carbon atoms long, quietly consuming carbon dioxide and hydrogen, and excreting vinegar.

[Githyanki]

I think there's more to consider about alien life than math alone. Probably the assumption that all intelligent life turns out like us and wants to conquer the universe.

[cosmocrazy]

According to the 'Drake' equation there might be as many as 50,000 life forms of some intelligence across this Galaxy.

and that being so does not suggest we will ever find it., or any traces of it..

Time and distance are the enemy's we can not beat. That we should and must keep looking is also real.

Mark @ 39' 55", 52.92 South.

Absolutely!

But, this is based on what we (humans) are not capable of.
Time and distance may be experienced differently by alien species. By this I mean, what we may consider a long time or a far distance might not be the same for ET.
All we have to go on is our own experience of life here on Earth. We only assume that life out there is no more resiliant as life here on Earth.

What if there exists an alien species that live much much longer than what we experience. What if they are able to live in much more hostile enviroments? What if they can with stand more enviromental extremes or are much better at repairing/healing than us? What if when they reproduce, genetically they pass on directly all their learned information and experiences so that the next generation automatically gaines a wealth of knowledge, experience and understanding? what if they have access to unimaginable amounts of energy? What if they are capable of crossing interstella distances with what seems like ease to them? What if they are capable of travelling near light speeds? What if they can somehow warp spacetime like gravity, able to manipulate it at will?...

Ok these variables all sound very sci-fi, but they are not impossible or should I say they cannot yet be proved either way.

I believe the chances of us being the only intelligent life in the universe is near on impossible. Simply because there are so many stars in the universe that will have so many planets orbiting them. But I cannot see how it would ever be possible for them or us to make contact unless one or more of those sci-fi variables I mentioned were possible.

So for now all we can do is keep looking and wait.

[Ara Pacis]

I suspect that humans are the only intelligent and potentially spacefaring creatures in the galaxy, and possibly beyond. There may be intelligent species on other worlds, as there are on earth, but they may not have the physical ability to travel off-world or even use tools in anything more than a rudimentary fashion.

If there were, we'd probably be able to tell if we saw them in person. While it's not impossible for different species to experience time at different speeds, I don't think it's probable that there would be extreme variations. After all, chemistry, thermodynamics and radiation act on molecular biology in their own frames of reference that limit how fast or slow information can be transmitted. Maybe they might be mistaken for trees but not rocks, ignoring camouflage.

[Colin Robinson]

I think there's more to consider about alien life than math alone.

Yes, I think there is a lot more.

Probably the assumption that all intelligent life turns out like us

Yes. If we are looking for beings like ourselves, why not just look in the mirror?

and wants to conquer the universe.

If they really are like us, they are very good at making movies about themselves conquering the universe…

[Colin Robinson]

If there were, we'd probably be able to tell if we saw them in person. While it's not impossible for different species to experience time at different speeds, I don't think it's probable that there would be extreme variations. After all, chemistry, thermodynamics and radiation act on molecular biology in their own frames of reference that limit how fast or slow information can be transmitted. Maybe they might be mistaken for trees but not rocks, ignoring camouflage.

You think that (apart from camouflage) a living thing could never be mistaken for a non-living object?

What about corals? Some have shapes like trees, but others can look very like rocks. As far as I know, this has nothing to do with camouflage, it is the way they use calcium carbonate for stability.

[Selfsim]

You think that (apart from camouflage) a living thing could never be mistaken for a non-living object?

What about corals? Some have shapes like trees, but others can look very like rocks. As far as I know, this has nothing to do with camouflage, it is the way they use calcium carbonate for stability.

The real question is what are the odds for misdiagnosis by using remote sensing technologies, over light-year distances ?
How does this compare with diagnosis performed onsite, by human beings armed with life detecting laboratory equipment ?

Regards

[Colin Robinson]

The real question is what are the odds for misdiagnosis by using remote sensing technologies, over light-year distances ?

Interesting question...

If ET astronomers detected O2 and organic compounds being produced in Earth's atmosphere at or near the surface, would they said: "Eureka, photosynthesis!"

Or would they said: "Hmm, very interesting chemistry. Must be some sort of catalyst involved here..."

How does this compare with diagnosis performed onsite, by human beings armed with life detecting laboratory equipment ?

... or even a robot lander, which could not only test for complex molecules, but could also take photos of microscopic structures?

[Selfsim]

Interesting question...

If ET astronomers detected O2 and organic compounds being produced in Earth's atmosphere at or near the surface, would they said: "Eureka, photosynthesis!"

Or would they said: "Hmm, very interesting chemistry. Must be some sort of catalyst involved here…"

Well, I took the time to read through the paper eburacum45 linked in post #31 (thanks eburacum45 .. much appreciated ). As he mentions, A. Leger seems to think O₃ is a better litmus test than O₂. Beats me why … Leger still seems to be assuming photosynthesised O₂ is the supply chain source, so I'm not sure what the difference is, except O₃ would be at higher altitudes, unable to be interfered with by hypothesised ground-hugging reactive H, OH and HO₂, and hence, perhaps easier to detect. (Many, many, many hidden assumptions, glossing over many, many, many hidden variables here).

In the overall scheme of a truly vast exo search-space, of vast physical environment diversity, for something we have trouble remotely diagnosing, even on Earth, (ie: 'life'), I still find it difficult to understand the seemingly unswerving fixation of looking for Earth-like life, and metabolic by-products over vast interstellar distances. Other than by circumstances of pure lack of exo-life instance data, for which a strategy for overcoming it by searching locally, would seem to be the priority, I find building search strategies on top of such a myopic perspective, to be limiting in the extreme, and ultimately no better, … no .. I mean … actually worse than, the good 'ol coin-toss approach applied to existing Kepler-like data, filtered by scientific intuition.

... or even a robot lander, which could not only test for complex molecules, but could also take photos of microscopic structures?

… and then be unable to return this valuable data .. because of the vast distances which cannot be feasibly bridged by present-day communications technologies ..??..
… Which kind of answers my question about misdiagnosis by using remote sensing technologies, over light-year distances … the answer seems to be, from a practical perspective .. 100%.

Regards

[Ara Pacis]

You think that (apart from camouflage) a living thing could never be mistaken for a non-living object?

What about corals? Some have shapes like trees, but others can look very like rocks. As far as I know, this has nothing to do with camouflage, it is the way they use calcium carbonate for stability.

And how intelligent are coral?

[Colin Robinson]

Well, I took the time to read through the paper eburacum45 linked in post #31 (thanks eburacum45 .. much appreciated ). As he mentions, A. Leger seems to think O₃ is a better litmus test than O₂. Beats me why … Leger still seems to be assuming photosynthesised O₂ is the supply chain source, so I'm not sure what the difference is, except O₃ would be at higher altitudes, unable to be interfered with by hypothesised ground-hugging reactive H, OH and HO₂, and hence, perhaps easier to detect.

Leger's point, if I understand it correctly, isn't that the reactive H, OH, and HO₂ are ground-hugging exactly. Rather that in photosynthesis they don't get produced, or at least don't accumulate, as happens in straightforward photolysis of H₂O.

The difference is this: Both photolysis and photosynthesis involve breaking up the water molecule into oxygen and hydrogen, but in photosynthesis, the hydrogen is then combined with CO₂ to produce organic compounds such as sugars. Leaving the oxygen free to form ozone...

So if you detect O₃ in the atmosphere of a water-rich planet, you may conclude that not only is water being dissociated, but there is something going on to consume the resulting hydrogen, e.g. by combining it with CO₂.

So far so good... but what if hydrogen and CO₂ can be combined by some process not involving a living organism? Such as a reductive Krebs cycle involving carboxylic acids and mineral catalysts instead of enzymes?

Which is something recent lab work suggest can indeed happen... I mentioned this finding in an earlier posting, but here it is again for your convenience.

http://astrobio.net/exclusive/3359/shallow-origins

Other than by circumstances of pure lack of exo-life instance data, for which a strategy for overcoming it by searching locally, would seem to be the priority,

If you count the worlds of this solar system as "local", then yes, I agree -- we are most likely to find unambiguous exo-life data by searching with robot missions to Mars, Europa, Enceladus and Titan.

I find Titan especially attractive, because we already know there are complex chemical reactions there, and life can be viewed as a subset of complex chemistry…

[Colin Robinson]

And how intelligent are coral?

I concede they may not be geniuses. Still, they are probably smarter than the average tree. Coral polyps don't have brains as such, but do have nerve nets, which trees do not have.

This seems relevant because in your last post you suggested that intelligent aliens might possibly be mistaken for trees...

[eburacum45]

I can imagine an extraterrestrial lifeform that secretes complex nerve-like structures into its substrate so that numerous individual polyp-like organisms can be connected neurally into a single responsive organism; eventually such creatures could become intelligent (assuming suitable evolutionary pressure).

I call this imaginary species Brain-coral (the hyphen is there to differentiate it from the somewhat less responsive examples found on our world).

One day in the far future our descendants may face the challenge of communicating with thinking coral reefs. Or something else equally as unexpected and outside our experience.

[Ara Pacis]

I concede they may not be geniuses. Still, they are probably smarter than the average tree. Coral polyps don't have brains as such, but do have nerve nets, which trees do not have.

This seems relevant because in your last post you suggested that intelligent aliens might possibly be mistaken for trees...

only insofar as I think the concept is merely improbable instead of impossible with regard to intelligences experiencing time at different rates. Something that experiences time slowly might be slow moving and mistaken for what we consider flora. That a dumb such organism on earth or another planet might exist seems plausible, that a smart such organism might exist seems unlikely, and that we would remotely detect its intelligence without detailed longitudinal analysis and vivisection seems even less likely.

[Selfsim]

So far so good... but what if hydrogen and CO₂ can be combined by some process not involving a living organism? Such as a reductive Krebs cycle involving carboxylic acids and mineral catalysts instead of enzymes?

Which is something recent lab work suggest can indeed happen... I mentioned this finding in an earlier posting, but here it is again for your convenience.

http://astrobio.net/exclusive/3359/shallow-origins

Thanks for the link (again) .. much appreciated .. and interesting.
And this is just one example of such a process ... how many other ones could one dream up from amongst a selection of vast environmental diversity ? (Please .. a purely rhetorical question .. )

If you count the worlds of this solar system as "local", then yes, I agree -- we are most likely to find unambiguous exo-life data by searching with robot missions to Mars, Europa, Enceladus and Titan.

I find Titan especially attractive, because we already know there are complex chemical reactions there, and life can be viewed as a subset of complex chemistry…

Yep .. that's kind of what I'm talkin' 'bout .. except, IMHO, robotics are best, only for rudimentary data gathering. Even within our own system, the risk of losing one, 'locally', is far from insignificant. However, if we lose track of the priority of finding evidence 'locally', the quest to solicit light-year distant sensed data alone, cannot possibly progress knowledge of exo-life distributions (if it exists at all).

Unless robotically sensed 'local life' is glaringly obvious .. declaration of exo-life without human contact, is also difficult to envisage.

Regards

[Solfe]

I think there's more to consider about alien life than math alone. Probably the assumption that all intelligent life turns out like us and wants to conquer the universe.

I would settle for conquering the tri-state area.

[Gomar]

Or maybe there are very complex life-forms on other worlds, but they are so different from us (and from each other) that terms like "intelligence" and "advanced" are hardly applicable?

If any species has gone beyond making fire, stone tools, and living in caves to develop math and writing,
building pyramids, then electricity, then TV and radio, then skyscrapers, then airplanes, then computers,
then space flight, then flying to other planets and galaxies... then they are intelligent, and _very_ advanced, no matter how they look.

If 1+1=2 could be understood by any alien species, whether beavers, penguins, or dolphins on any planet then they are intelligent.

[Colin Robinson]

If any species has gone beyond making fire, stone tools, and living in caves to develop math and writing,
building pyramids, then electricity, then TV and radio, then skyscrapers, then airplanes, then computers,
then space flight, then flying to other planets and galaxies... then they are intelligent, and _very_ advanced, no matter how they look.

You are saying that if their bodies are different from ours, but their technologies are the same, then they are intelligent... But how likely is it that their technologies really would be the same?

If 1+1=2 could be understood by any alien species, whether beavers, penguins, or dolphins on any planet then they are intelligent.

We express mathematical concepts by means of symbols: either sounds or written characters. What if we encounter a complex life form which uses symbols we can't understand, and neither can they understand our symbols? How would we know whether they do or don't have a concept corresponding to "1 + 1 = 2" ?