"Exo-life" or "life in the universe"?

[Colin Robinson]

Does it matter whether we think in terms of "exo-life" or "life in the universe"? Which concept is more in keeping with Copernican astronomy?

If we think in terms of "exo-life", or "extra-terrestrial life", the first question that arises is: "Does it exist?"

It is possible to compare "extra-terrestrials" with elves or mermaids: Like elves and mermaids, extra-terrestrials often appear in imaginative literature, but hard evidence of their physical existence is lacking.

On the other hand, if we think in terms of "life in universe", the question of its existence is already answered: There is life on Earth; and Earth is in the universe.

The question then is: "How common or how rare is life in the universe?"

[Paul Wally]

On the other hand, if we think in terms of "life in universe", the question of its existence is already answered: There is life on Earth; and Earth is in the universe.

The question then is: "How common or how rare is life in the universe?"

I agree with this view of "life in the universe" and I think "terrestrial" and "extra-terrestrial" represents an artificial distinction in a universe that is obviously neither geocentric nor anthropocentric. From the perspective of a neutral observer, say a visitor from another galaxy, the Earth will be one instance of life in this galaxy. This neutral observer won't draw the distinction of Earth-life and Exo-life. Relative to this neutral observer all life in this galaxy will be exo-life.

[R.A.F.]

It is possible to compare "extra-terrestrials" with elves or mermaids...

"If" the ET's are of the flying saucer variety, then the comparison has validity.

On the other hand, if we think in terms of "life in universe", the question of its existence is already answered: There is life on Earth; and Earth is in the universe.

The question is usually posed as "is there life elsewhere in the Universe?"...anyhow, semantically speaking, I wonder if the same thing said in different languages would have the same "pun" value.

The question then is: "How common or how rare is life in the universe?"

Well, that's an easy one...we don't know....personal opinion is that there is in fact other advanced civilizations somewhere out there, but the distances involved are so vast, I think it quite possible that we will never meet ET's.


I'd love to be proved wrong.




Oh...one other thing....

Does it matter whether we think in terms of "exo-life" or "life in the universe"? Which concept is more in keeping with Copernican astronomy?

What does one have to do with the other? How does Copernican astronomy relate to what terms are used to describe "other life"???

[Selfsim]

Does it matter whether we think in terms of "exo-life" or "life in the universe"? Which concept is more in keeping with Copernican astronomy?

If we think in terms of "exo-life", or "extra-terrestrial life", the first question that arises is: "Does it exist?"

It is possible to compare "extra-terrestrials" with elves or mermaids: Like elves and mermaids, extra-terrestrials often appear in imaginative literature, but hard evidence of their physical existence is lacking.

On the other hand, if we think in terms of "life in universe", the question of its existence is already answered: There is life on Earth; and Earth is in the universe.

The question then is: "How common or how rare is life in the universe?"

The generalisation of 'life' beyond the one sample we have undeniable evidence for, is the issue I see here.
If such generalisation is supportable by physical evidence, then we might have a chance of coming up with a 'Universal' theory of life which is testable, (by physical exploration/discovery), and would then have scientific relevance.

The only ways I can see to make the leap from the one unique life model we presently have, to a generalised model, is to:

i) discover another instance of independent life emergence either on, or beyond Earth or;
ii) discover life in the lab (ie: discover how to synthesise it from scratch).

We cannot yet predict the necessary details of what we could then learn from such discoveries. If such a discovery represents a second independent emergence of life, then I would think we would be well on the way towards developing a generalised 'Universal' model, but until that happens, all that remains is pure speculation. It seems to me this needs to become much, much clearer

The Copernican Principle may still be valid at the large astronomical scales, but it is not a sufficient enough basis to extrapolate from about 'life', (ie: granular enough), as it says nothing about the diversity of what we observe around us at the smaller scales. In fact, its application at the microscopic levels is irrelevant and moot. Its like trying invoke quantum mechanical principles to explain how a planet orbits its star.

The 'commonness' or 'rareness' question you pose, is unanswerable without further discoveries and a lot more data.
Even then, a 'likely' outcome is not a dead certainty.

The presence of life on Earth does not imply life elsewhere, and the number of exo-planets discovered in the observable universe, is a moot point until another discovery is made within it.

[Selfsim]

I agree with this view of "life in the universe" and I think "terrestrial" and "extra-terrestrial" represents an artificial distinction in a universe that is obviously neither geocentric nor anthropocentric. From the perspective of a neutral observer, say a visitor from another galaxy, the Earth will be one instance of life in this galaxy. This neutral observer won't draw the distinction of Earth-life and Exo-life. Relative to this neutral observer all life in this galaxy will be exo-life.

Such a hypothetical 'neutral' observer would have to be something along the lines of Maxwell's demon, otherwise its own presence biases the outcome of the observation (thus not achieving 'neutrality'). How this demon would then define life, might be a perplexing question, as it itself, would be neither living nor non-living. If it was neither living nor non-living, it would be incapable of distinguishing between the two observations ... so, how would it recognise 'life' anywhere? If it couldn't recognise life anywhere, then the distinction between the terms Earth-'life' and non-Earth 'life', disappears as well.

The frame of reference from which it observes other parts of the universe, would be irrelevant.

[Colin Robinson]

What does one have to do with the other? How does Copernican astronomy relate to what terms are used to describe "other life"???

A term like "extra-terrestrial" involves a conceptual separation of the Earth from the rest of the universe.

Today, thanks to Copernicus we think of the Earth as a planet comparable to other planets. And yet, many relics of pre-Copernican thinking remain in the way we talk about the universe.

For instance, the very fact that we speak of "the Earth" is based on the old idea that Earth is an object in a class of its own. We don't speak of "the Mars" or "the Jupiter".

We do speak of "the Moon" and "the Sun", but only because each of these bodies looks unique when viewed from Earth. We don't speak of "the Ganymede" or "the Sirius".

The term "extra-terrestrial" -- as in "extra-terrestrial life" -- is based on the same old idea, that Earth is in a class of its own. We might as well speak of the highlands of the Moon as "extra-terrestrial mountains", or the lakes of Titan as "exo-lakes".

Well, that's an easy one...we don't know....

I agree that we don't know how frequent or rare life is in the universe.

We know a little more than we did in the days of Kepler, when it was thought that the Moon might have life on it.

personal opinion is that there is in fact other advanced civilizations somewhere out there, but the distances involved are so vast, I think it quite possible that we will never meet ET's.

I'm inclined to think that worlds with advanced civilizations on them may be a lot less frequent than those with ecosystems of microbes. This conjecture is based on how long our own world has had micro-organisms on it, compared with how long it has had our civilization.

I'd love to be proved wrong.

If we hope to learn more than we know now, it is important that we don't jump to premature conclusions, either positive or negative.

An example of a premature negative conclusion is Senator
Richard Bryan's famous dismissal of radio SETI:

"The Great Martian Chase... may finally come to an end. As of today millions have been spent and we have yet to bag a single little green fellow."

Would you agree that cynicism like that is unhelpful to research?

[Ara Pacis]

A term like "extra-terrestrial" involves a conceptual separation of the Earth from the rest of the universe.

It is separate, with regards to life, as far as we can tell.

Today, thanks to Copernicus we think of the Earth as a planet comparable to other planets. And yet, many relics of pre-Copernican thinking remain in the way we talk about the universe.

No we don't. It means we think of the earth as not favored or unique, not that we think that it's like everything else. That's not incompatible with the idea that the conditions for life are uncommon enough that we'll never find it elsewhere. the Copernican Principle is about how we view probability, but has no bearing on the physical reality that determines probability.

For instance, the very fact that we speak of "the Earth" is based on the old idea that Earth is an object in a class of its own. We don't speak of "the Mars" or "the Jupiter".

Provincialism is provincial, and semantics is semantic. We use articles with it because earth can have different meanings in normal conversation. The moon is often referred to that way because we use the word generically instead of using a proper name for it in common conversation. you may notice that sometimes people don't capitilize earth or moon unless its used without an article.

We do speak of "the Moon" and "the Sun", but only because each of these bodies looks unique when viewed from Earth. We don't speak of "the Ganymede" or "the Sirius".

On the contrary, Ganymede is "a moon" and Sirius is "a sun" for bodies in its system.

The term "extra-terrestrial" -- as in "extra-terrestrial life" -- is based on the same old idea, that Earth is in a class of its own. We might as well speak of the highlands of the Moon as "extra-terrestrial mountains", or the lakes of Titan as "exo-lakes".

Geographic features are characteristics of extra-terrestrial objects, not extra-terrestrial objects on their own. One of these things is not like the others.

We know a little more than we did in the days of Kepler, when it was thought that the Moon might have life on it.

IIRC, the moon does have life on it that we put there.

[Selfsim]

Today, thanks to Copernicus we think of the Earth as a planet comparable to other planets. And yet, many relics of pre-Copernican thinking remain in the way we talk about the universe.

This reads like an ode to Copernicus !
The modern perspective is that uniqueness, diversity and ubiquity all co-exist simultaneously, at varying scales of granularity.
The quest is to discover the scales at which each exists, doesn't exist, or co-exist.

The blanket rejection of the idea of uniqueness at arbitrary scales within the observable universe, is just as much a philosophical stance as geocentrism !

The Laws of Physics may apply regardless of one's frame of reference within the observable universe, at the same (or different) time(s), but the adoption of different values of the constants by natural processes, (in the solutions to the fundamental equations), may also occur beyond it.

[Colin Robinson]

The generalisation of 'life' beyond the one sample we have undeniable evidence for, is the issue I see here.

I agree that we should be careful about generalizing from a single example.

But how many examples do we know, of planets which are habitable, and yet do not have life?

The closest thing we have to such a case (habitable yet lifeless) is Mars... except that we don't yet have undeniable evidence either for its habitability or for the absence of life there....

The presence of life on Earth does not imply life elsewhere,

Conversely, if it is confirmed that Mars has no life on it...

would the absence of life on Mars imply absence of life elsewhere?

If we were to draw sweeping conclusions from a lifeless Mars, wouldn't we be generalizing from a sample size of one?

[Colin Robinson]

It is separate, with regards to life, as far as we can tell.

Perhaps that depends on what you mean by "as far as we can tell". I would agree that as yet we have no conclusive direct evidence of life on other worlds.

Please consider another class of things we have no conclusive direct evidence for yet -- exomoons, i.e. natural satellites of planets in other solar systems.

Would you say that our own solar system is in a separate category, with regard to moons, as far as we can tell?

On the contrary, Ganymede is "a moon" and Sirius is "a sun" for bodies in its system.

True. Nonetheless, when we speak of "the Moon" we don't usually mean Ganymede, and when we speak of "the Sun", we don't usually mean Sirius.

[Selfsim]

I agree that we should be careful about generalizing from a single example.

But how many examples do we know, of planets which are habitable, and yet do not have life?

The closest thing we have to such a case (habitable yet lifeless) is Mars... except that we don't yet have undeniable evidence either for its habitability or for the absence of life there....

If the test for a generalised hypothesis returns null or positive results .. then progress can be made.

If the test returns no result, then the test should be revised, or change the hypothesis.

That the test results might be hard to obtain, is of no concern to theoretical science.

If one seeks to establish a physical theory, one needs real-world results, consistent with that theory.

Marching on, assuming that a mapping between theory and the real world exists, is delusional.

The presence of life on Earth does not imply life elsewhere

Conversely, if it is confirmed that Mars has no life on it... would the absence of life on Mars imply absence of life elsewhere?

No.

If we were to draw sweeping conclusions from a lifeless Mars, wouldn't we be generalizing from a sample size of one?

Yes.

What's your point here, Colin ?

[Colin Robinson]

What's your point here, Colin ?

My point is that there is more than one kind of speculation.

Please consider the following propositions:

1.Out of the total number of habitable worlds in the universe, the majority have some form of life on them.
2.Out of the total number of habitable worlds in the universe, the majority are without life.

Presumably one or other of these is true. (Unless the proportion of habitable worlds with life is exactly 50 percent...)

I'd agree with you that proposition 1 is not proven. Although we do have one example of a habitable world with life on it, namely Earth, that does not prove proposition 1. To prove it (as you've pointed out) we would either need a very thorough understanding of abiogenesis, or else we would need to find other habitable worlds and identify organisms on them.

On the other hand, proposition 2 is not proven either. We don't yet even have one confirmed example of a habitable world without life on it. Mars may turn out to be an example of this, but we don't actually know that yet. Even if Mars does turn out to be both habitable and lifeless, it will still be one example only. We would then need a larger sample of habitable worlds to determine whether Earth or Mars is more typical. Or else we would need a thorough understanding of abiogenesis, and why it is a low-probability event.

[Selfsim]

My point is that there is more than one kind of speculation.

Please consider the following propositions:

1.Out of the total number of habitable worlds in the universe, the majority have some form of life on them.
2.Out of the total number of habitable worlds in the universe, the majority are without life.

Presumably one or other of these is true. (Unless the proportion of habitable worlds with life is exactly 50 percent...)

Well, no.
Assuming 'the universe' refers to the 'observable universe' (only), the following statement is present-day physical fact ... ('truth' has nothing to do with it):
3. Out of the total number of habitable worlds in the universe, we know of extant life on one planet only.

I really dislike the term 'habitable worlds', but for the sake of harmony .. I'll ride along with it ... for the moment.
We should also discount any lifeforms sent along on our probes, etc, also.

Statements #1 and #2 are not practically verifiable or falsifiable, because it is not feasible to travel to the necessary number of 'habitable worlds', in order to apply the necessary tests, and retrieve the results, (distances being the main limiting factor).

If 'the universe' is theoretically infinite, (in time, and spatially), then in theory:
4. There would be an infinite number of life instances throughout the universe, including exact duplicates of Earth-life, in every detail.
The problem here of course, is that it in practice, it is also not feasible to test this statement. I doubt that it would be theoretically feasible either, although there is a theoretical/philosophical argument called 'Infinite Tasking', which might just sneak it over the line, as far as theoretical testability is concerned.

I'd agree with you that proposition 1 is not proven. Although we do have one example of a habitable world with life on it, namely Earth, that does not prove proposition 1. To prove it (as you've pointed out) we would either need a very thorough understanding of abiogenesis, or else we would need to find other habitable worlds and identify organisms on them.

On the other hand, proposition 2 is not proven either. We don't yet even have one confirmed example of a habitable world without life on it. Mars may turn out to be an example of this, but we don't actually know that yet. Even if Mars does turn out to be both habitable and lifeless, it will still be one example only. We would then need a larger sample of habitable worlds to determine whether Earth or Mars is more typical. Or else we would need a thorough understanding of abiogenesis, and why it is a low-probability event.

'Proofs' exist in mathematics ... and Courts of Law .. I'm not aware of such in physics. Verification/falsification of the 'majority' term, would involve testing the necessary number of 'habitable worlds' within the finite set, within the observable universe .. which is not practically feasible.
If we gain knowledge of biological, environmental causative and inhibitive factors from discoveries, and this knowledge then goes into an abiogenesis theory, then probablisitic estimates might gain some evidence-based credibility.

Regards

[R.A.F.]

My point is that there is more than one kind of speculation.

Well, evidenced speculation isn't speculation anymore, so there is only one "type", that being unevidenced speculation.

[Paul Wally]

Such a hypothetical 'neutral' observer would have to be something along the lines of Maxwell's demon, otherwise its own presence biases the outcome of the observation (thus not achieving 'neutrality'). How this demon would then define life, might be a perplexing question, as it itself, would be neither living nor non-living. If it was neither living nor non-living, it would be incapable of distinguishing between the two observations ... so, how would it recognise 'life' anywhere? If it couldn't recognise life anywhere, then the distinction between the terms Earth-'life' and non-Earth 'life', disappears as well.

What you are saying implies that there are no neutrally observable differences between living and non-living systems, which is absurd.

If one seeks to establish a physical theory, one needs real-world results, consistent with that theory.

Yes that's right, consistent with, but this theory must also have implications that might possibly be inconsistent with future real-world results.

Marching on, assuming that a mapping between theory and the real world exists, is delusional.

The whole point of testing a theory is to check the "mapping between theory and real world", so complete mapping is never assumed. But a theory must have implications beyond the available evidence, otherwise it is really completely useless as a scientific theory.

If 'the universe' is theoretically infinite, (in time, and spatially), then in theory:
4. There would be an infinite number of life instances throughout the universe, including exact duplicates of Earth-life, in every detail.
The problem here of course, is that it in practice, it is also not feasible to test this statement. I doubt that it would be theoretically feasible either, although there is a theoretical/philosophical argument called 'Infinite Tasking', which might just sneak it over the line, as far as theoretical testability is concerned.

We have a much stronger theoretical base of scientific discoveries in physics, chemistry, geology etc. to work from than the empty "in theory" scenario you're sketching above. What is needed is an explanation of how life emerges in a universe working according to laws we have discovered until now. Once we have such an explanation then that explanation can be tested against the evidence.

Well, evidenced speculation isn't speculation anymore, so there is only one "type", that being unevidenced speculation.

Well, in a scientific context, it's called "conjecture" and it's purpose is usually to explain something.

[Colin Robinson]

Out of the total number of habitable worlds in the universe, we know of extant life on one planet only.

Out of the total number of habitable worlds in the universe, we have tested for extant life on two planets only.

What we know is limited. The question is, how can we know more?

I really dislike the term 'habitable worlds',

Why do you dislike the term "habitable worlds"?

We should also discount any lifeforms sent along on our probes, etc, also.

Agreed. Claimed survival of earth microbes on devices sent to the Moon doesn't tell us much about how common or rare life is in the universe. Except that it makes the idea of spacecraft-assisted panspermia seem a little more feasible.

If we gain knowledge of biological, environmental causative and inhibitive factors from discoveries, and this knowledge then goes into an abiogenesis theory, then probablisitic estimates might gain some evidence-based credibility.

I agree that greater understanding of abiogenesis would help us to estimate how many worlds abiogenesis has happened on.

Regards
Colin

[Ara Pacis]

Perhaps that depends on what you mean by "as far as we can tell". I would agree that as yet we have no conclusive direct evidence of life on other worlds.

As far as we can tell we can't rule out pre-historic cross-contamination in our own solar system, so even if we find life elsewhere in this solar system, we may not be able to show that it came from a separate abiogenesis event.

Please consider another class of things we have no conclusive direct evidence for yet -- exomoons, i.e. natural satellites of planets in other solar systems.

Would you say that our own solar system is in a separate category, with regard to moons, as far as we can tell?

There is no such thing as an exo-moon. Moons cannot be described as exo because moons cannot be exo. A moon, by definition, is always subject to identification with a planet. A planet may be exo, and thus an exo-planet may have a moon, but no planet, local or exo, can have an exo-moon because at that point it is no longer a moon.

True. Nonetheless, when we speak of "the Moon" we don't usually mean Ganymede, and when we speak of "the Sun", we don't usually mean Sirius.

If we lived on Jupiter, we might, if we chose to ignore all the other moons. If we lived in the Sirian system we almost certainly would. A frame of reference is a reference for framing.

[Selfsim]

I agree with this view of "life in the universe" and I think "terrestrial" and "extra-terrestrial" represents an artificial distinction in a universe that is obviously neither geocentric nor anthropocentric. From the perspective of a neutral observer, say a visitor from another galaxy, the Earth will be one instance of life in this galaxy. This neutral observer won't draw the distinction of Earth-life and Exo-life. Relative to this neutral observer all life in this galaxy will be exo-life.

Such a hypothetical 'neutral' observer would have to be something along the lines of Maxwell's demon, otherwise its own presence biases the outcome of the observation (thus not achieving 'neutrality'). How this demon would then define life, might be a perplexing question, as it itself, would be neither living nor non-living. If it was neither living nor non-living, it would be incapable of distinguishing between the two observations ... so, how would it recognise 'life' anywhere? If it couldn't recognise life anywhere, then the distinction between the terms Earth-'life' and non-Earth 'life', disappears as well.

What you are saying implies that there are no neutrally observable differences between living and non-living systems, which is absurd.

No more absurd than your hypothetical 'neutral' alien observer.
How can an alien observer possibly be 'neutral' in this case ?

If one seeks to establish a physical theory, one needs real-world results, consistent with that theory.

Yes that's right, consistent with, but this theory must also have implications that might possibly be inconsistent with future real-world results.

Why must it ?
How would anyone possibly know, in the present-day, about any 'future real-world inconsistencies', such that they would form part of a present-day 'theory', for an as yet unobserved phenomenon?

The whole point of testing a theory is to check the "mapping between theory and real world", so complete mapping is never assumed. But a theory must have implications beyond the available evidence, otherwise it is really completely useless as a scientific theory.

Well, we're starting to make progress … finally ! (Only in as far as your scoping of what abiogenesis is to be used for, (ie: prediction), from your own perspective).

Evolutionary molecular biological research is far from being 'completely useless'. Its interpretation within the context of predictions of abiogenesis elsewhere, cannot realise value in science until it has evidence in direct support of a second emergence .. and for all the other reasons cited in the other thread.

We have a much stronger theoretical base of scientific discoveries in physics, chemistry, geology etc. to work from than the empty "in theory" scenario you're sketching above. What is needed is an explanation of how life emerges in a universe working according to laws we have discovered until now. Once we have such an explanation then that explanation can be tested against the evidence.

Why is this needed ? If there is a purpose, then philosophical determinism is the driver.
Its becoming much clearer that this 'theory' is really a speculative hypothesis bounded by known Physics (which I don't have a problem with) … it is not a scientific theory, because it cannot predict specifically emergence, as it has no basis in empiricism until a second emergence is either synthesised in the lab or discovered someplace.

I am concluding that the "must" term you keep citing, is evidence of a desire, driven by a philosophical belief, that the universe and life emergence, be fundamentally determinable .. which is falsified in general, by many physical examples so far cited in other threads.

Well, in a scientific context, it's called "conjecture" and it's purpose is usually to explain something.

I'm not sure what definitions of scientific Theory and Hypothesis you're drawing from, but as a first blush, mine are (roughly):

Hypothesis: A tentative statement such as ‘if A happens then B must happen’ that can be tested by direct experiment or observation. A repeatedly verified hypothesis can be expressed as a law or a theory. A disproven hypothesis can sometimes be re-tested and found to be subsequently verified, as measurements improve.

Theory: An explanation for why/how certain laws and facts exist, that can be tested to determine its accuracy. It takes only one negative example to disprove a theory and one can't examine all examples of a phenomenon throughout all time and space, (the problem of induction). Theories are used to make predictions.

The highlighted and underlined parts of the above distinguish for me, what you're describing is actually a hypothesis, (a speculative one at that), which doesn't predict, due to a lack of description of directly applicable, relevant laws and fact, (in this case specific to life emergence). Inferences drawn from other areas of science do not inevitably form a solid basis for prediction in complex systems, such as life, or complex biochemical pathways.

I offer this as a possible way to describe where I'm coming from .. not as a way to promote argument. If my definition is not agreed, then at least we'll understand why we aren't seeing eye-to-eye on this.

Regards

[Colin Robinson]

There is no such thing as an exo-moon. Moons cannot be described as exo because moons cannot be exo. A moon, by definition, is always subject to identification with a planet. A planet may be exo, and thus an exo-planet may have a moon, but no planet, local or exo, can have an exo-moon because at that point it is no longer a moon.

You are thinking of what is called a rogue planet. The term exoplanet simply means a planet outside our own solar system. "Extrasolar planet" is a more longwinded synonym. If an exoplanet has a moon, it is termed an exomoon, or extrasolar moon.

Why did I mention extrasolar moons? Simply because:

1.We have zero direct evidence that they exist.
2.There are cogent indirect reasons for thinking that they would exist.
3.Looking for direct evidence is considered valid scientific work.
4.If they do exist, they will not be a basically new class of thing, rather members of an existing class of thing (moons), but in different and more remote locations.

All of which, as far as I can see, also applies to life beyond Earth.

[Selfsim]

Out of the total number of habitable worlds in the universe, we have tested for extant life on two planets only.

What we know is limited. The question is, how can we know more?

Fair enough .. agreed.
Exploration and direct testing is one way to know more.

Why do you dislike the term "habitable worlds"?

My definition, (including online dictionary definitions), of 'world' is:
"The Earth, (or planet in this case), together with its countries, peoples, societies, institutions, lifeforms and natural features."

In this case those other 'worlds' are more accurately termed as 'planets'.

If we gain knowledge of biological, environmental causative and inhibitive factors from discoveries, and this knowledge then goes into an abiogenesis theory, then probablisitic estimates might gain some evidence-based credibility.

I agree that greater understanding of abiogenesis would help us to estimate how many worlds abiogenesis has happened on.

I stand by my words above, (not necessarily what you said above). I'd prefer to change the exact wording by removing 'theory' and inserting 'hypothesis'. I also further qualified this perspective in my other statement with words to the effect of:
"Even a 'likely' outcome, is not a dead certainty".

Regards

[Colin Robinson]

In this case those other 'worlds' are more accurately termed as 'planets'.

I see... The reason I use the term "habitable worlds", is that I mean to include habitable moons, as well as habitable planets.

[Selfsim]

I see... The reason I use the term "habitable worlds", is that I mean to include habitable moons, as well as habitable planets.

The language lets us down a bit, eh ?

.. perhaps a 'planety moony thingy' ?

Cheers

[Selfsim]

Why did I mention extrasolar moons? Simply because:

1.We have zero direct evidence that they exist.
2.There are cogent indirect reasons for thinking that they would exist.
3.Looking for direct evidence is considered valid scientific work.
4.If they do exist, they will not be a basically new class of thing, rather members of an existing class of thing (moons), but in different and more remote locations.

All of which, as far as I can see, also applies to life beyond Earth.

So now, 'Wally's Neutral Demon' (analogous with 'Maxwell's demon') .. is defined as being incapable of distinguishing between 'life' and a 'moon', eh (??)

(Just kidding).

Cheers

[Ara Pacis]

You are thinking of what is called a rogue planet.

No, I'm not.

If an exoplanet has a moon, it is termed an exomoon, or extrasolar moon.

According to who? Did I miss an IAU vote?

I was attempting to show the absurdity of the term, but apparently other people have absurd notions about semantics. Anyways, until there is an official definition, I'll use mine.

Why did I mention extrasolar moons? Simply because:

1.We have zero direct evidence that they exist.
2.There are cogent indirect reasons for thinking that they would exist.
3.Looking for direct evidence is considered valid scientific work.
4.If they do exist, they will not be a basically new class of thing, rather members of an existing class of thing (moons), but in different and more remote locations.

All of which, as far as I can see, also applies to life beyond Earth.

You're making a classic mistake. You're confusing category for population.

[Colin Robinson]

So now, 'Wally's Neutral Demon' (analogous with 'Maxwell's demon') .. is defined as being incapable of distinguishing between 'life' and a 'moon', eh (??)

(Just kidding).

Cheers

Seriously, Selfsim, I don't see what you find so ridiculous about Paul's concept of a neutral observer.

This is what Paul originally wrote:

I agree with this view of "life in the universe" and I think "terrestrial" and "extra-terrestrial" represents an artificial distinction in a universe that is obviously neither geocentric nor anthropocentric. From the perspective of a neutral observer, say a visitor from another galaxy, the Earth will be one instance of life in this galaxy. This neutral observer won't draw the distinction of Earth-life and Exo-life. Relative to this neutral observer all life in this galaxy will be exo-life.

Surely, it is clear (in this context) that a "neutral observer" means someone who observes things in this galaxy without beginning with the assumption that one particular planet or solar system is in a different category from all the rest?

We earthlings have actually been working towards this sort of conceptual neutrality for the past few centuries. It is what the Copernican revolution in astronomy is all about.

Why would a neutral observer use a term like "exomoons" for any moons of any solar systems except one? Would it not be more consistent with neutrality to speak of "moons of the Milky Way Galaxy"?

Why would a neutral observer use a different term like "exolife" for any living things on any planet except one? Would it not be more consistent with neutrality to speak of "life in the Milky Way Galaxy"?

[Colin Robinson]

If an exoplanet has a moon, it is termed an exomoon, or extrasolar moon.

According to who?

According to, for instance, the astronomers engaged in the Hunt for Exomoons with Kepler project (HEK).

I was attempting to show the absurdity of the term, but apparently other people have absurd notions about semantics.

I actually find the term "exomoon" somewhat absurd too. But no more absurd than the term "exolife"…

You're making a classic mistake. You're confusing category for population.

According to which classical authority is that a classic mistake? How is the mistake defined, and why do you think I am making it?

[Selfsim]

Seriously, Selfsim, I don't see what you find so ridiculous about Paul's concept of a neutral observer.
.. {snip} ...
We earthlings have actually been working towards this sort of conceptual neutrality for the past few centuries. It is what the Copernican revolution in astronomy is all about.

If you want to get serious about it, then I would recommend dropping the semantic games immediately.

The point is that the Copernican Principle has only loosely and scantily, indirectly inferred applicability only, when it comes to distinguishing 'Earth life'/'exo-life', 'terrestrial life'/'extra-terrestrial life', (or whatever hypothetical semantic flavour one chooses) at biological scale levels. As a matter of fact, the observer cannot escape the bias introduced by noticing the nature of its own existence (biology), in a universe where no other comparative life-forms have been observed. 'Neutrality' when it comes to observing a one-life model observable universe, is meaningless.

If the so-called neutral observer has developed knowledge of a universal model of life, courtesy of an astronomical amount of prior testing, then this would be the testing basis for distinguishing differences ... not a philosophical posit about the ubiquity of physical laws and environments throughout an observable universe.

[Colin Robinson]

If you want to get serious about it, then I would recommend dropping the semantic games immediately.

Not quite sure what you mean by "semantic games"...

The topic I raised in the opening post of this thread was the difference between thinking in terms of "exo-life" or "life in the universe"... Are you saying that this whole topic is just a semantic game?

As a matter of fact, the observer cannot escape the bias introduced by noticing the nature of its own existence (biology), in a universe where no other comparative life-forms have been observed. 'Neutrality' when it comes to observing a one-life model observable universe, is meaningless.

It's true that no other life-forms have been observed by us terrestrials. Does that mean we are in a "one-life model observable universe"? Are "observed" and "observable" the same thing?

Has everything observable on the surface of Mars (for instance) already been observed? If so, why do we bother to send new devices there, such as the Curiosity rover?

[Paul Wally]

How can an alien observer possibly be 'neutral' in this case ?

Maybe because I defined it as neutral. But your argument implies that neutrality is impossible, and that's why I'm asking, how can the distinction between living and non-living not be a neutral observation, i.e. how can life not be objectively recognizable as life? Is life relative? That would make the fact that we are alive relative too, which is absurd.

Why must it ?
How would anyone possibly know, in the present-day, about any 'future real-world inconsistencies', such that they would form part of a present-day 'theory', for an as yet unobserved phenomenon?

A theory must have implications beyond the evidence, otherwise it's completely useless as a theory. Now these implications might be inconsistent with future real-world discoveries. Scientific theories are not infallible.

Evolutionary molecular biological research is far from being 'completely useless'. Its interpretation within the context of predictions of abiogenesis elsewhere, cannot realise value in science until it has evidence in direct support of a second emergence .. and for all the other reasons cited in the other thread.

I'm not referring to "evolutionary molecular biological research". I'm saying that anything that doesn't make predictions beyond current evidence is completely useless as a scientific theory. It shouldn't even be called a scientific theory. The Ptolemaic system of the solar system is an example of a theory that's incapable of making novel predictions and it's not even wrong, as Wolfgang Pauli would say. The research program that you're proposing implies that we cannot proceed theoretically unless we have evidence of a second instance of life, but if we cannot proceed theoretically with one instance there's no guarantee that a second instance is going to bring us any closer to solving the problem of abiogenesis. There's no guarantee that an n-th instance is going to solve the problem. That is because the problem is theoretical, that is, to explain how abiogenesis is possible in this universe.

Why is this needed ? If there is a purpose, then philosophical determinism is the driver.

The purpose is understanding, and in order to understand something we need to explain it.

Its becoming much clearer that this 'theory' is really a speculative hypothesis bounded by known Physics (which I don't have a problem with) … it is not a scientific theory, because it cannot predict specifically emergence, as it has no basis in empiricism until a second emergence is either synthesised in the lab or discovered someplace.

The theory I'm referring to, which explains abiogenesis from established empirically based scientific theories, doesn't exist yet. Since it doesn't exist yet, you cannot know beforehand what it will be capable of predicting.

I am concluding that the "must" term you keep citing, is evidence of a desire, driven by a philosophical belief, that the universe and life emergence, be fundamentally determinable .. which is falsified in general, by many physical examples so far cited in other threads.

"Fundamentally determinable" is a bit vague, therefore it is not at all clear what it is that is falsified, according to you. I proceed on the premise that the universe and life emergence is intelligible , but that's not the same as deterministic.

I'm not sure what definitions of scientific Theory and Hypothesis you're drawing from, but as a first blush, mine are (roughly):

Hypothesis: A tentative statement such as ‘if A happens then B must happen’ that can be tested by direct experiment or observation. A repeatedly verified hypothesis can be expressed as a law or a theory. A disproven hypothesis can sometimes be re-tested and found to be subsequently verified, as measurements improve.

In the definitions I've seen, the hypothesis is the antecedent of the conditional statement (if A then B), where only A is the hypothesis and B is that which requires explanation.
See the Wikipedia article on hypothesis: "A hypothesis (from Greek ὑπόθεσις; plural hypotheses) is a proposed explanation for a phenomenon."

Inferences drawn from other areas of science do not inevitably form a solid basis for prediction in complex systems, such as life, or complex biochemical pathways.

As I repeatedly tried to make clear: Complexity is a mathematically implicit possibility, and therefore it can follow implicitly from a system defined purely on the basis of physical and chemical laws. These have been computationally demonstrated. The point is that you don't know that these "other areas of science", combined with purely mathematical complexity theory, are insufficient for the development of a theory of abiogenesis capable of making testable predictions.

I offer this as a possible way to describe where I'm coming from .. not as a way to promote argument. If my definition is not agreed, then at least we'll understand why we aren't seeing eye-to-eye on this.

Yes, your definition of hypothesis is not agreed upon. It appears to limit hypothesis to mere mechanical inductive generalization; something a computer can be taught to do. You assume that evidence leads like breadcrumbs to a comprehensive theory of phenomena. Inductive generalization leaves hardly any room for human creativity, conceptual inventiveness and originality.

[Ara Pacis]

According to, for instance, the astronomers engaged in the Hunt for Exomoons with Kepler project (HEK).

Doesn't make them an authority on nomenclature.

I actually find the term "exomoon" somewhat absurd too. But no more absurd than the term "exolife"…

Then don't use it. You have agency in what you do and what you say. I'm not a fan of the term exolife either, but it does have a different basis and description. A moon is a class of object, and is itself meaningless without a plant about which it orbits. A more proper formulation would be exoplanet moon because exo is not useful for defining the object moon due to the different degrees of separation in concept. I wouldn't be so hardcore about this, except the IAU has bent over backwards to make a ridiculous definition of "planet" such that we can't actually know if any object we detect in another system can be considered a planet (ignoring the fact that it doesn't orbit our sun). Some asteroids have objects orbiting them, we don't call those asteroid-moons, we just call them moons, or more properly, satellites.

According to which classical authority is that a classic mistake? How is the mistake defined, and why do you think I am making it?

Group Dynamics Theory, for one. Have you no conception in the english language that you cannot determine the difference in meaning yourself? A group or population are part of a single system through interaction: it's a physical organization. A category or collection is based only on similar traits: it's a logical organization. For example, The student body of a college is a group, because they all interact in some manner. However, "freshmen of colleges across the country" is a category, since they do not interact as part of a unitary system.

Life is a system. Life, so far as we can tell, starts and continues and in a manner of thinking is, what I'll call, a hyper-organism with a continuous existence going back billions of years perhaps to a single origin. Life on Mars might be part of that hyper-organism but we don't know if there is life or if it is part of the same genesis because we have reason to believe that dispersal is plausible within our solar system. Life anywhere else in the universe is likely to not be related unless and until a link can be established. Thus, exo has some sort of distinction between us and them. However, balls of matter with certain arbitrary definitions scattered throughout the observable universe is exactly that, unrelated blobs of matter that merely present similar characteristics to a definition.