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primummobile
2012-Jul-14, 03:37 PM
Note: This is a reply I posted to RAF in another thread, arguing what assumptions, if any, one should make about the existence of alien life. As my time is somewhat limited, I also meant for it to serve as a response to some of the arguments advanced by Selfsim and noclevername. I copied my response to here so we could continue the discussion without derailing the other thread. I did not copy other posts because without moderator privileges it would be too tedious to do so.


First, the Nessie or Sasquatch question. I was using those as examples of an absurdity. Namely, that no one here is advocating any of the absurd claims that you see from cryptozoologists, but I don't see a real distinction between how some react to cryptozoology claims and how they react to claims that extraterrestrial life exists.

Personally, I am inclined to believe that life in the universe is relatively rare, and intelligent life even more rare. Please note, I make a very strong distinction between belief and knowledge. But, I am unwilling to discount the possibility of other life in the universe simply because of what we do know about life on earth. We know that life on earth arose almost immediately after the Late Heavy Bombardment, which is probably just about as early as it was able to exist. Absent some other mechanism for creation, that leads me to believe that it is not difficult for life to, at minimum, get started. Some form of life probably started many times on the ancient earth. It's unlikely that mother nature got it right on the first try.

We also know that the entire universe, including where both of us are sitting, started in the same initial conditions. So, unless Earth is really special, it is mathematically unlikely that no other life exists. Of course, as you would say, the mathematical likelihood of something happening does not constitute evidence. And I agree with that, which brings me to my final point.

No one is assuming that life exists. The exact statements were all of the variety of "I wouldn't assume life does not exist." You are equating "I assume something" with "I do not assume not-something" when they are not logically equivalent. To make any kind of assumption, a reasonable person requires evidence to back up that assumption. We almost universally reject the notion that sasquatch exists because we have explored almost every square foot of the land surface of the earth and never found any evidence to confirm his existence, yet we have found evidence of all other types of life spanning billions of years. Therefore, it is absurd to assume Sasquatch exists because the overwhelming evidence says he does not.

In the case of Sasquatch, we have clear and overwhelming evidence of absence. In the case of alien life, what we have is absence of evidence. Again, evidence of absence and absence of evidence are not equivalent. A doctor who thoroughly examines a patient and finds no evidence of cancer can safely say, "I assume there is no cancer." But a doctor who has examined only the tip of a patient's nose can only say, "I cannot assume that there is not cancer." No other statement about whether or not the patient has cancer can be logically made.

In the case of the question of existence of alien life, the absence of evidence overwhelms the evidence of absence. We have only closely examined a vanishingly small part of even our own solar system. We don't even know how to look for extraterrestrial life. We don't know if there are microbes in the middle cloud layers of Venus, the supposed oceans of Europa, or the hydrocarbon lakes on Titan. We know so little about them that it is logically impossible to assume that life does not exist. The only thing we can do is to not assume that life does not exist. If you are not assuming something, it means that you are assuming nothing. Taking any other position with so little information available cannot be logically supported.

R.A.F.
2012-Jul-14, 03:58 PM
Taking any other position with so little information available cannot be logically supported.

If you just started this thread to say "RAF is wrong", well, you won't get any argument from me....I'm "wrong" most of the time...:D



...however as I posted, there is no "right" answer to this question...not until/unless we "discover" other life. That is why I left the other thread (and this one, too), as I have no need to persue "pointless" discussions.

...or will you "argue" that is not logical, too??

primummobile
2012-Jul-14, 04:05 PM
I don't see why you are being defensive, and though I would like for you to stay I certainly don't expect it from you. If I didn't think what you said had a lot of merit I wouldn't reply to your arguments. And I never said that you were being illogical, I said that it is illogical to draw a conclusion from a lack of evidence, which I am sure you agree with.

If I wanted to argue that you were wrong I would just PM you. I just want to discuss the logic of assuming whether or not life exists, not point out that someone is wrong. To do that, I would need to know that you are wrong. And I don't know that.

R.A.F.
2012-Jul-14, 04:22 PM
While I appreciate your reasonableness, I simply do not want to "play".

Noclevername
2012-Jul-14, 06:52 PM
Assuming? None. Speculating on? Plenty.

primummobile
2012-Jul-14, 07:09 PM
Assuming? None. Speculating on? Plenty.

Are you saying that you assume there is no life? Or that you assume nothing?

Noclevername
2012-Jul-14, 07:12 PM
Are you saying that you assume there is no life? Or that you assume nothing?

Neither. I'm saying that I speculate on the possibility of life ..or lifelessness.. elsewhere in the Universe.

Noclevername
2012-Jul-14, 07:19 PM
Speculating about something is not the same as assuming it.

profloater
2012-Jul-14, 07:21 PM
To start a logical argument you begin with your assumptions and then develop what logically follows from that (or those). You can in argument challenge either the assumption(s) or the logic. But those two challenges are quite different.

If you start by an assumption of ignorance there is no logical way forward. Usually people assume that what seems to be, is. So we accept "evidence" as "real" and then argue logically from the evidence.

Since you seem to be interested in Alien life the general view seems to be that unless it is inside our solar system the time factor for information alone is evidence that we cannot know about it. Inside our solar system we know the basic conditions that support life on our planet are not found anywhere else but we can also extend out acceptance of the range of possible life forms. Therefore we might assume there is no advanced lifeforms outside Earth in our solar system, but the sheer numbers of stars in the universe might allow many planets out there with assumed intelligent but we are too far away to ever find out.

primummobile
2012-Jul-14, 07:48 PM
Speculating about something is not the same as assuming it.

I don't disagree with that. My point was that I am not assuming anything. I can say that something is likely (speculate) without assuming it to be true or untrue.

profloater
2012-Jul-14, 07:55 PM
The assumption of a probability is rather similar to agnosticism but setting some arbitrary value close to 0 and 1, to exclude those extreme probabilities. True agnosticism is to assume that you cannot know.

"So let us never ever doubt, what nobody is sure about"

Van Rijn
2012-Jul-14, 08:11 PM
First, the Nessie or Sasquatch question. I was using those as examples of an absurdity. Namely, that no one here is advocating any of the absurd claims that you see from cryptozoologists, but I don't see a real distinction between how some react to cryptozoology claims and how they react to claims that extraterrestrial life exists.


I haven't been following your discussion with RAF, but I did want to comment on this statement. Perhaps you haven't seen some of the absurd ET claims that I've seen, but there often is little distinction between ET and cryptozoology claims. A discussion of, for instance, the possibility of life on Mars is one thing. But claims that images from Mars show buildings, various creatures, plants, petrified wood, etc. are very much like Nessie or Big Foot claims. We've seen a number of "aliens in the picture" claims. We've also seen a lot of claims about visiting ET spaceships that exhibit magical capabilities. Many people consider magical spaceship sighting claims to be more plausible than mythical creature sighting claims. Yet, barring solid supporting evidence, the only real difference between a magical ET spaceship claim and a flying dragon claim is that a belief in magical alien spaceships is more acceptable in our culture.

Anyway, one reason you'll see people react strongly in ET life discussions is that we have seen a lot of absurdity in such discussions. Discussions that avoid absurdity are rare.

primummobile
2012-Jul-14, 08:24 PM
To start a logical argument you begin with your assumptions and then develop what logically follows from that (or those). You can in argument challenge either the assumption(s) or the logic. But those two challenges are quite different.

If you start by an assumption of ignorance there is no logical way forward. Usually people assume that what seems to be, is. So we accept "evidence" as "real" and then argue logically from the evidence.

I'm not making any assumption of ignorance. I'm not making any assumption at all. Maybe I need to be a little more clear about what I am advocating.

Some have said, according to the way I understand them, that the only logical assumption we can make is that life outside of Earth does not exist since we have seen no evidence of it. I am merely advocating that we cannot make any assumptions about it because we don't know. In other words, it is just as egregious to assume ET life does exist as it is to assume it does not. I am further saying that while we may find some condition to be likely, it is not the same thing as assuming the truth value of that condition.

I think that the most pure way to gather knowledge is to make no assumptions about anything until you have sufficient information to do so. Being human, that is pretty difficult to do. But we should really refrain from making assumptions until we know what we are trying to find. I expounded in another post the difference between an assumption and a belief. Maybe RAF was right about it being all semantics. But I think that they are distinct. But really, that's neither here nor there. The point is that I think it is more logically correct, in the face of underwhelming evidence, to assume nothing rather than to assume anything at all. Better to wait until some substantial evidence is gathered.


Since you seem to be interested in Alien life the general view seems to be that unless it is inside our solar system the time factor for information alone is evidence that we cannot know about it. Inside our solar system we know the basic conditions that support life on our planet are not found anywhere else but we can also extend out acceptance of the range of possible life forms. Therefore we might assume there is no advanced lifeforms outside Earth in our solar system, but the sheer numbers of stars in the universe might allow many planets out there with assumed intelligent but we are too far away to ever find out

To be honest, the thought of alien life really doesn't interest me that much, and for precisely the reasons you stated. Ir there was intelligent life in any nearby stars I think we could have communication, especially if we were to send probes to those stars. (or they to us) But I think the chances of intelligent life being nearby is highly unlikely. And as I've detailed in other posts, it is probable that civilizations only use radio for a very short time, or at least that they only use it in a high-power low-gain format (like we do) for a short amount of time. I also think it is probable that we would be unable to communicate with any civilization that was more that a few thousand years ahead of us in technological development. The distances involved are, in my opinion, insurmountable. I do think if there are other civilizations in our galaxy and we all survive long enough, we will gain knowledge of each other. But we won't interact.

Now, that whole preceding paragraph was my speculation on ET life. If I had to do some kind of study, that would be my starting point, albeit with a lot more detail. But I assume absolutely none of what I just said. When I first started learning astronomy in elementary school over thirty years ago my textbook said that Jupiter had 16 moons and Saturn 12. It said we didn't know what quasars were and there was not one mention of a neutron star. I could go on and on, but you get the point. The point is that we know very little. Certainly not enough to assume that life doesn't exist simply because we haven't been provided with evidence to the contrary.

And if a flying saucer landed on my yard tomorrow I would immediately have assumptions about ET life.

primummobile
2012-Jul-14, 08:31 PM
I haven't been following your discussion with RAF, but I did want to comment on this statement. Perhaps you haven't seen some of the absurd ET claims that I've seen, but there often is little distinction between ET and cryptozoology claims. A discussion of, for instance, the possibility of life on Mars is one thing. But claims that images from Mars show buildings, various creatures, plants, petrified wood, etc. are very much like Nessie or Big Foot claims. We've seen a number of "aliens in the picture" claims. We've also seen a lot of claims about visiting ET spaceships that exhibit magical capabilities. Many people consider magical spaceship sighting claims to be more plausible than mythical creature sighting claims. Yet, barring solid supporting evidence, the only real difference between a magical ET spaceship claim and a flying dragon claim is that a belief in magical alien spaceships is more acceptable in our culture.

Anyway, one reason you'll see people react strongly in ET life discussions is that we have seen a lot of absurdity in such discussions. Discussions that avoid absurdity are rare.

I realize that, although I hadn't taken it into consideration. I've read through some of the UFO threads. To be fair, the title of the thread was something along the lines of "Alien Attack Scenarios". It was just my opinion that the view being taken by some was too minimalist. i.e. "extraterrestrial life does not exist because we have seen no evidence of it." I'll go along with "there haven't been any extraterrestrial visits to Earth". I just think that saying there is no extraterrestrial life is extreme. As I said before, I make no claim about the truth value of that statement. I only question the foundation.

primummobile
2012-Jul-14, 08:33 PM
The assumption of a probability is rather similar to agnosticism but setting some arbitrary value close to 0 and 1, to exclude those extreme probabilities. True agnosticism is to assume that you cannot know.

"So let us never ever doubt, what nobody is sure about"

I believe that it is impossible for us to know about many things. I think all we can do is get ever closer to the truth.

Paul Beardsley
2012-Jul-14, 08:34 PM
It was just my opinion that the views being taken by some was too minimalist. i.e. "extraterrestrial life does not exist because we have seen no evidence of it."

I read the thread in question - I must have missed the bit where somebody said that. Can you provide the quotation?

primummobile
2012-Jul-14, 08:44 PM
I read the thread in question - I must have missed the bit where somebody said that. Can you provide the quotation?


I wouldn't be too quick to presume there isn't something else unusual out there in our solar system.


Why not?


Still...I wouldn't be too quick to presume there isn't something else unusual out there in our solar system.

There's no evidence of any.


All they are saying is that you shouldn't assume that life does not exist elsewhere.


Why is it that Nessie and Sasquatch require evidence before belief, yet a much more important question...if life exists elsewhere in the universe, is "given a pass"...is "assumed" to be correct?


… All they are saying is that you shouldn't assume that life does not exist elsewhere.


Why not assume that ?
It seems completely appropriate to do so … particularly if we simultaneously assume that life exists elsewhere, (and I see an abundance of that .. right here !)



They go on from there for a few more posts.


This is sidetracking from the issue. I just want to know if it is more correct to:

a) assume no life exists because we haven't seen evidence of it

b) assume nothing about other life because we have no evidence either way other than sheer numbers.

Noclevername
2012-Jul-14, 08:49 PM
None of those quotes actually say that ET life definitely does not exist. You seem to have overgeneralized from an exercise in speculation to a presumption of absolute belief.

For someone who "assumes nothing" when it comes to science, you certainly appear to jump to conclusions when dealing with other people.

Paul Beardsley
2012-Jul-14, 10:07 PM
None of those quotes actually say that ET life definitely does not exist.

Agreed.

When I asked who in the thread had said, "Extraterrestrial life does not exist because we have seen no evidence of it," the correct answer would have been, "Nobody in the thread said that."

And no, it's not sidetracking, it was a (presumably accidental) misrepresentation of other people's opinions that needed clearing up.

profloater
2012-Jul-14, 10:51 PM
I believe that it is impossible for us to know about many things. I think all we can do is get ever closer to the truth. Talking about "the truth" always makes me smile especially after declaring that we cannot know many things. Truth is a property of truth tables, arithmetic and the possible number of chess games, maybe. It is a false friend in seeking answers to life's puzzles. I wish you good luck.

marsbug
2012-Jul-14, 10:57 PM
............... I just want to know if it is more correct to:

a) assume no life exists because we haven't seen evidence of it

b) assume nothing about other life because we have no evidence either way other than sheer numbers.

My default position would be to assume nothing without evidence - although that does not prevent useful speculation based on what we know of the available environments off Earth, the environments we know life can inhabit on Earth, and what we can reasonably assume about the environment needed for abiogenesis to occur.

Selfsim
2012-Jul-14, 11:42 PM
... it was a (presumably accidental) misrepresentation of other people's opinions that needed clearing up.Well for my part, I have been trying to clear up any misinterpretations of where I'm coming from. Its no small task. I hope some of my recent posts in other threads may help … see my post #66 in the Expose-E(d) thread, here. (http://cosmoquest.org/forum/showthread.php/135808-EXPOSE-E(d)-life-in-space!?p=2043826#post2043826)


… I just want to know if it is more correct to:

a) assume no life exists because we haven't seen evidence of it

b) assume nothing about other life because we have no evidence either way other than sheer numbers.'Sheer numbers' is not evidence for exo-life !!!

If you think it is, please demonstrate this for us.

Colin Robinson
2012-Jul-14, 11:51 PM
We also know that the entire universe, including where both of us are sitting, started in the same initial conditions. So, unless Earth is really special, it is mathematically unlikely that no other life exists.

This is the key issue -- whether Earth is special? Over the last few centuries, science has established that Earth is not special in the sense that everything else goes around it, not special in the sense of being composed of different elements, not special in the sense that its solar system is near the centre of the galaxy...


We almost universally reject the notion that sasquatch exists because we have explored almost every square foot of the land surface of the earth and never found any evidence to confirm his existence, yet we have found evidence of all other types of life spanning billions of years. Therefore, it is absurd to assume Sasquatch exists because the overwhelming evidence says he does not... In the case of the question of existence of alien life, the absence of evidence overwhelms the evidence of absence. We have only closely examined a vanishingly small part of even our own solar system. We don't even know how to look for extraterrestrial life. We don't know if there are microbes in the middle cloud layers of Venus, the supposed oceans of Europa, or the hydrocarbon lakes on Titan.

I agree. To think that beyond-Earth life is in the same category as Sasquatch is to overlook how thoroughly we've explored this Earth (especially North America, the presumed habitat of Sasquatch!), in comparison with how little we've explored in places beyond Earth, even within our own Solar System.

Colin Robinson
2012-Jul-14, 11:56 PM
I haven't been following your discussion with RAF, but I did want to comment on this statement. Perhaps you haven't seen some of the absurd ET claims that I've seen, but there often is little distinction between ET and cryptozoology claims. A discussion of, for instance, the possibility of life on Mars is one thing. But claims that images from Mars show buildings, various creatures, plants, petrified wood, etc. are very much like Nessie or Big Foot claims.

Perhaps you haven't seen some of the anti-ET claims that I've seen... E.g. websites arguing that that belief in aliens is actually a secular substitute for belief in God...


Anyway, one reason you'll see people react strongly in ET life discussions is that we have seen a lot of absurdity in such discussions.

I'd put it this way. In discussions about ET life we can see plenty of unrigorous arguments both for and against its existence. Perhaps this is simply because it's an unresolved question that greatly interests all sorts of people?

primummobile
2012-Jul-15, 12:28 AM
Well for my part, I have been trying to clear up any misinterpretations of where I'm coming from. Its no small task. I hope some of my recent posts in other threads may help … see my post #66 in the Expose-E(d) thread, here. (http://cosmoquest.org/forum/showthread.php/135808-EXPOSE-E(d)-life-in-space!?p=2043826#post2043826)

'Sheer numbers' is not evidence for exo-life !!!

If you think it is, please demonstrate this for us.

I'm not saying that it is evidence in the way that a dead alien in hand is evidence. I'm saying that the numbers increase the odds. Remember, I am assigning no value to the truth of either statement. If one person buys a lottery ticket, chances are pretty good he will not win. If 200 million people buy a ticket chances are pretty good at least one person will win. And before you say it, that was only an example. I'm not saying it's the same thing. I'm just saying that the only thing that the argument for exo-life has going for it is the fact that there are so many chances for it to have developed.

primummobile
2012-Jul-15, 12:37 AM
None of those quotes actually say that ET life definitely does not exist. You seem to have overgeneralized from an exercise in speculation to a presumption of absolute belief.

For someone who "assumes nothing" when it comes to science, you certainly appear to jump to conclusions when dealing with other people.

There is no reason to make this personal, nor is there any call for it. I didn't do that to you and I'd appreciate if you showed me the same courtesy. The entire reason I started this thread is to continue the conversation so I could understand what people meant by what they said without continuing to sidetrack the other thread. Everyone makes generalizations. At least I do you the courtesy of explicity asking you to expand on your thoughts. If I understood what you were saying I wouldn't have asked.

primummobile
2012-Jul-15, 12:42 AM
Agreed.

When I asked who in the thread had said, "Extraterrestrial life does not exist because we have seen no evidence of it," the correct answer would have been, "Nobody in the thread said that."

And no, it's not sidetracking, it was a (presumably accidental) misrepresentation of other people's opinions that needed clearing up.


No, you did not ask WHO said it. You asked for QUOTES. I gave you the quotes leading up to it. In the last quote, I asked "why you woukd you not assume that life does not exist?" and the reply was "why not assume that?" That's the thrust of this entire thread. I want to understand that statement.

mutleyeng
2012-Jul-15, 12:45 AM
I'm confused.
I read your opening post, and then i read the options you present us are



a) assume no life exists because we haven't seen evidence of it

b) assume nothing about other life because we have no evidence either way other than sheer numbers.

where was option c) assume there probably is without claiming it as knowledge
Your opening post was firmly in option c)
which is very different from assume nothing.
Because people may question the validity of your assumptions does not mean they reject an, as yet, unquantifiable possibility

R.A.F.
2012-Jul-15, 12:49 AM
Because people may question the validity of your assumptions does not mean they reject an, as yet, unquantifiable possibility

Thankyou....

Noclevername
2012-Jul-15, 12:51 AM
There is no reason to make this personal, nor is there any call for it. I didn't do that to you and I'd appreciate if you showed me the same courtesy. The entire reason I started this thread is to continue the conversation so I could understand what people meant by what they said without continuing to sidetrack the other thread. Everyone makes generalizations. At least I do you the courtesy of explicity asking you to expand on your thoughts. If I understood what you were saying I wouldn't have asked.

I apologize, I meant no insult. I also have trouble with understanding non-explicit statements (I have Asperger's Syndrome) and I sometimes need it pointed out to me if I am misinterpreting something.

primummobile
2012-Jul-15, 01:03 AM
I apologize, I meant no insult. I also have trouble with understanding non-explicit statements (I have Asperger's Syndrome) and I sometimes need it pointed out to me if I am misinterpreting something.
No need to apologize. I have Asperger's too, and that's probably half the reason I am having trouble understanding this. But it makez me good at certain things, and one of those is computer programming, so, for all my faults, one of the things I am very good at is following all the "nots" in a statement. I think someone in all this is misinterpreting one of my "nots" and I am misinterpreting their reply. I too need things explicity explained. I have trouble with irony or riddles and I feel like a lot of the replies are riddles.

primummobile
2012-Jul-15, 01:08 AM
I'm confused.
I read your opening post, and then i read the options you present us are



where was option c) assume there probably is without claiming it as knowledge
Your opening post was firmly in option c)
which is very different from assume nothing.
Because people may question the validity of your assumptions does not mean they reject an, as yet, unquantifiable possibility

Because I also said in my first post that I make a very strong distinction between belief and knowledge. To me, assumptions can only be made when you some kind of evidence to back it up. Others may equate belief with assumptions. I don't. If you or anybody else doesn't think the same way, all you have to do is tell me. To my knowledge, you are the first person to say that.

mutleyeng
2012-Jul-15, 01:19 AM
Because I also said in my first post that I make a very strong distinction between belief and knowledge. To me, assumptions can only be made when you some kind of evidence to back it up. Others may equate belief with assumptions. I don't. If you or anybody else doesn't think the same way, all you have to do is tell me. To my knowledge, you are the first person to say that.

There are a number of threads on here about what is "evidence" for ET life. The arguments have been gone over in quite some detail in those.
I think it fairly safe to say that those you think were claiming a non existence position where actually only rejecting your evidence and assumptions.
Its fine to have assumptions, but if you use them to justify a position then you should expect to have them challenged.

primummobile
2012-Jul-15, 01:33 AM
There are a number of threads on here about what is "evidence" fo

r ET life. The arguments have been gone over in quite some detail in those.
I think it fairly safe to say that those you think were claiming a non existence position where actually only rejecting your evidence and assumptions.
Its fine to have assumptions, but if you use them to justify a position then you should expect to have them challenged.

I accept that. But I want to make it clear that what you would call an assumption I only call a reasonable belief. If someone thinks I am being unreasonable I would expect to be told that. I guess you could say that I assume that some form of exo life is more likely than not to exist, but I think that is an oversimplification.

I lurkex around these boards for a while before joining. I was very active over on Wikipedia before joining here, and most of my time was consumed by making editors find reputable sources for what they were putting in articles. I pay a lot of attention to detail and so I guess I was just taken aback when I interpreted replies to my posts to mean that I was being unreasonable in my beliefs because I thought I was being explicit in saying that my beliefs are not assumptions. I guess it's pretty silly to start all of this over the definition of a word.

primummobile
2012-Jul-15, 01:37 AM
There are a number of threads on here about what is "evidence" for ET life. The arguments have been gone over in quite some detail in those.
I think it fairly safe to say that those you think were claiming a non existence position where actually only rejecting your evidence and assumptions.
Its fine to have assumptions, but if you use them to justify a position then you should expect to have them challenged.


And I really only wanted to know the truth value of "not assuming aliens do not exist". Throwing what I believe into the mix probably muddied the waters, but that was not my intention. I just wanted to make clear what I believe because I think that is important to know for someone who is evaluating your statements.

mutleyeng
2012-Jul-15, 01:50 AM
well, if you came to these boards and claimed it as knowledge that ET existed, you'd get carried away in a straight jacket.
The debates here are essentially between those with your position, who consider they have grounds for a reasonable belief - and those who do not consider your evidence leading you to that belief as legitimate.
I am entirely neutral on the question of life - that means that I neither think it likely or unlikely - its just unknown. I think thats where most you thought denied the possibility of ET life also sit.

chrlzs
2012-Jul-15, 02:32 AM
I may have missed this point being raised earlier, if so I apologise for skimming..!

But it seems to me that the claim we have an abundance of life here on earth is VERY misleading. By definition (assuming you accept evolution), 'abundance' is what inevitably happens once you have a SINGLE outbreak of life. And as far as I am aware there is no evidence of anything but one single outbreak of life, somewhere on this planet, at some particular time, under very precise (and at this stage, unknown) conditions. In all the time before or since, no other life has sprung into existence. In all of our (perhaps crude and simplistic) experiments, not once have we managed to duplicate those conditions. In other words, rather than it being very likely that life will spring up given the right earth-like conditions, I would argue exactly the reverse...

So based on what I see (or rather DON'T see) here on Terra, I think the chance of life existing elsewhere is pretty much vanishingly small. While I don't dispute there may be some of it elsewhere, given the tyranny of distance and all the other factors of timing, self- and cosmological- destruction, the chance of it becoming intelligent/sentient let alone technological, let alone interested in 'reaching out'... I'll happily accept that we are, for all intents and purposes, currently - and likely for the duration of our race - quite alone.

And btw, that doesn't depress me at all - I find plenty of other stuff easily interesting enough to keep me occupied.. :D

Paul Wally
2012-Jul-15, 02:34 AM
In the case of the question of existence of alien life, the absence of evidence overwhelms the evidence of absence. We have only closely examined a vanishingly small part of even our own solar system. We don't even know how to look for extraterrestrial life. We don't know if there are microbes in the middle cloud layers of Venus, the supposed oceans of Europa, or the hydrocarbon lakes on Titan. We know so little about them that it is logically impossible to assume that life does not exist. The only thing we can do is to not assume that life does not exist. If you are not assuming something, it means that you are assuming nothing. Taking any other position with so little information available cannot be logically supported.

Why do you have to assume anything? My approach would be to make suppositions, not assumptions. Suppose X is true, what follows if X is true? Suppose X is false, what follows etc.
There's a difference between making assumptions and making suppositions. Look, I just supposed X and then I supposed not(X) (no problem), but it would be irrational to assume both X and not(X).

For me, science operates at the level of supposition (not assumption), and that's where all the interesting (original) work is going on. I think it's far more interesting to have a rational discussion around different suppositions around alien life, than to have these dead-end discussions about who assumed what, and what can be assumed, and what can be said and what cannot be said. Sometimes these type of dead-end discussions even lead to restrictions on what can be thought and what cannot be thought, and this I find quite strange, because why must lack of evidence for something prevent us from thinking about the different logical possibilities?

Selfsim
2012-Jul-15, 03:01 AM
We also know that the entire universe, including where both of us are sitting, started in the same initial conditions. So, unless Earth is really special, it is mathematically unlikely that no other life exists.This is the key issue -- whether Earth is special? Over the last few centuries, science has established that Earth is not special in the sense that everything else goes around it, not special in the sense of being composed of different elements, not special in the sense that its solar system is near the centre of the galaxy... a) Colin: Why is this a key issue? I would've thought the key issue would have been whether life is special1?
b) Initial conditions: There is theoretical evidence that the observable universe started out chaotically. Randomness and order would seem at home in the aftermath .. and it is !
c) Primummobile: 'Mathematically unlikely: Could you please demonstrate for us, the mathematics behind such a statement ? I keep seeing 'mathematics' being used to make a point, and yet there is nothing from mathematics I know of, which would suggest that such a statement is anything more than pure arm-waving and a hijack of mathematics.


Footnotes:
1. I dislike using the term 'special' .. something unique, doesn't have to be 'special'. That being said, I only used the term as a quote of what was said.

mutleyeng
2012-Jul-15, 03:26 AM
For me, science operates at the level of supposition (not assumption),


I'm good with this - but then i was also good with a methodical sonar weep of Loch Ness too. That didnt mean i gave any of the evidence any credibility.

Van Rijn
2012-Jul-15, 03:27 AM
And as far as I am aware there is no evidence of anything but one single outbreak of life, somewhere on this planet, at some particular time, under very precise (and at this stage, unknown) conditions. In all the time before or since, no other life has sprung into existence.


We don't know that. We wouldn't know about other abiogenesis events unless they happened to have current and distinct descendents, or if there was something very distinct left in the fossil record. It's possible there have been multiple abiogenesis events on Earth.


In all of our (perhaps crude and simplistic) experiments, not once have we managed to duplicate those conditions. In other words, rather than it being very likely that life will spring up given the right earth-like conditions, I would argue exactly the reverse...


I would argue that we can't say very much about that based on current laboratory experiments. These laboratory experiments are extremely small scale compared to the planet over geological periods. Now, if you were conducting experiments with something like the volume of the Pacific Ocean, and you couldn't get results after a few hundred million years, then you might have a significant argument.

Colin Robinson
2012-Jul-15, 03:55 AM
it seems to me that the claim we have an abundance of life here on earth is VERY misleading. By definition (assuming you accept evolution), 'abundance' is what inevitably happens once you have a SINGLE outbreak of life. And as far as I am aware there is no evidence of anything but one single outbreak of life, somewhere on this planet, at some particular time, under very precise (and at this stage, unknown) conditions. In all the time before or since, no other life has sprung into existence. In all of our (perhaps crude and simplistic) experiments, not once have we managed to duplicate those conditions. In other words, rather than it being very likely that life will spring up given the right earth-like conditions, I would argue exactly the reverse...

Perhaps it depends whether you think of the origin of life as an single event or a process —

Was it a sudden, perhaps fortuitous, emergence of a replicating molecule out of a random soup of organic chemicals?

Or did relatively simple catalytic cycles, favored by the principles of thermodynamics, gradually become more efficient and more complex -- cycles along the lines of the reductive Krebs process, where carboxylic acids are formed out of an energy-rich mixture of hydrogen and carbon dioxide?

If we think of it as a single event, it may seem very significant that such an event happened only once.

If we think of it a process, I'm not sure whether you would expect it to happen a second time on a planet where it has already happened -- a planet where the energy from those energy-rich chemical mixtures already has channels to flow thru.

Here are links to two articles in which abiogenesis is understood more as a process than a single event:

Christian de Duve The Beginnings of Life on Earth (http://www.americanscientist.org/issues/id.864,y.0,no.,content.true,page.1,css.print/issue.aspx)

James Trefil, Harold Morowitz, Eric Smith The Origin of Life (http://www.americanscientist.org/issues/feature/2009/2/the-origin-of-life/1)

Colin Robinson
2012-Jul-15, 05:06 AM
Why do you have to assume anything? My approach would be to make suppositions, not assumptions. Suppose X is true, what follows if X is true? Suppose X is false, what follows etc.
There's a difference between making assumptions and making suppositions. Look, I just supposed X and then I supposed not(X) (no problem), but it would be irrational to assume both X and not(X).

For me, science operates at the level of supposition (not assumption), and that's where all the interesting (original) work is going on. I think it's far more interesting to have a rational discussion around different suppositions around alien life, than to have these dead-end discussions about who assumed what, and what can be assumed, and what can be said and what cannot be said. Sometimes these type of dead-end discussions even lead to restrictions on what can be thought and what cannot be thought, and this I find quite strange, because why must lack of evidence for something prevent us from thinking about the different logical possibilities?

Yes, I think this is a very important point!

It's an important part of science to look at suppositions (not yet established as facts), and ask: If this were true, what would follow?

I'm reminded of the distinction which Karl Popper made between a "bucket" theory of knowledge and a "searchlight" theory. Whether science is like lowering a bucket into water, or more is it like aiming a searchlight? In "the searchlight" model, you have to think about where and how the searchlight is to be directed -- it isn't just a matter of letting data pour in, like water into a bucket...

Selfsim
2012-Jul-15, 05:29 AM
Why do you have to assume anything? My approach would be to make suppositions, not assumptions.
...
For me, science operates at the level of supposition (not assumption), and that's where all the interesting (original) work is going on. I think it's far more interesting to have a rational discussion around different suppositions around alien life, than to have these dead-end discussions
...
why must lack of evidence for something prevent us from thinking about the different logical possibilities?Thinking about logical possibilities is fine ... but no progress will be made in the real world, (about the existence or otherwise of life elsewhere), unless such 'thinking' returns useful real-world data. I see the discussion of exolife, as not falling into any category of productive reasoning (deductive, inductive or abductive). The problem is there is no data that allows a conclusion to be formed, or allows the construction of a premise.

(Similarly, the lack of data cannot in itself, be considered as a valid basis for formulation of the premise that exo-life doesn't exist either, as this leads to the logical fallacy of 'argumentum ad ignorantium').

Cheers

Paul Beardsley
2012-Jul-15, 06:00 AM
No, you did not ask WHO said it. You asked for QUOTES. I gave you the quotes leading up to it. In the last quote, I asked "why you woukd you not assume that life does not exist?" and the reply was "why not assume that?" That's the thrust of this entire thread. I want to understand that statement.

You said It was just my opinion that the views being taken by some was too minimalist. i.e. "extraterrestrial life does not exist because we have seen no evidence of it."

I said I read the thread in question - I must have missed the bit where somebody said that. Can you provide the quotation?

Obviously, I meant the quotation that supported your claim that some were being too minimalist.

You then gave me a load of quotations, none of which support your claim that some were being too minimalist, none of which stated or implied "extraterrestrial life does not exist because we have seen no evidence of it." So perhaps you can withdraw the claim now.

Selfsim
2012-Jul-15, 06:02 AM
Yes, I think this is a very important point!

It's an important part of science to look at suppositions (not yet established as facts), and ask: If this were true, what would follow?

I'm reminded of the distinction which Karl Popper made between a "bucket" theory of knowledge and a "searchlight" theory. Whether science is like lowering a bucket into water, or more is it like aiming a searchlight? In "the searchlight" model, you have to think about where and how the searchlight is to be directed -- it isn't just a matter of letting data pour in, like water into a bucket...Important ?? I don't think so !

Due to the paucity of data, one has to go wherever the data leads. And the data comes from exploration of the real-universe.
What's more, it is just as likely to be completely unanticipated, as it is expected from purely philosophically motivated speculation.
Our best attempts at directed searches, in the light of having no data-based premises, are basically akin to searching in near infinite space, in darkness, for something we know we can only just barely detect in our local neighbourhood, in full light, right under our noses !

With such little understanding, focussing too heavily on logical reasoning as a basis for prioritising the search space, is nothing more than being led by philosophy, metaphysics, politics and delusion.

Where is the scientific importance in that ?

Colin Robinson
2012-Jul-15, 06:06 AM
a) Colin: Why is this a key issue? I would've thought the key issue would have been whether life is special1? Footnotes:
1. I dislike using the term 'special' .. something unique, doesn't have to be 'special'. That being said, I only used the term as a quote of what was said.

Well, if life is special/unique, and if Earth is the only place that has it, out of the astronomical number of planets in the universe... then I would have thought that made Earth a special/unique place? Wouldn't it?

Colin Robinson
2012-Jul-15, 06:29 AM
Important ?? I don't think so !

Due to the paucity of data, one has to go wherever the data leads. And the data comes from exploration of the real-universe.
What's more, it is just as likely to be completely unanticipated, as it is expected from purely philosophically motivated speculation.

I agree that data comes from exploration, and that what's found may be unanticipated. Still... scientists have debated whether to look for life beyond Earth via a "follow the water" strategy or a "follow the carbon" strategy, or what... One thing that is understood by all sides in such a debate is that there needs to be a strategy of some sort, there needs to be a program of research. This means having some conception (or "supposition", as Paul Wally says) of what the possibilities are...

Selfsim
2012-Jul-15, 06:51 AM
This is the key issue -- whether Earth is special? Over the last few centuries, science has established that Earth is not special in the sense that everything else goes around it, not special in the sense of being composed of different elements, not special in the sense that its solar system is near the centre of the galaxy...
a) Colin: Why is this a key issue? I would've thought the key issue would have been whether life is special?Well, if life is special/unique, and if Earth is the only place that has it, out of the astronomical number of planets in the universe... then I would have thought that made Earth a special/unique place? Wouldn't it?Hmm .. yet another speculative response with a bunch of 'ifs' (or leading assumptions).

Here's one that's not speculative: The existence of life on Earth, does not imply life exists elsewhere.

Earth may not be unique at the scales of, and in the attributes you mention ... and that implies nothing about life.

Selfsim
2012-Jul-15, 06:56 AM
I agree that data comes from exploration, and that what's found may be unanticipated. Still... scientists have debated whether to look for life beyond Earth via a "follow the water" strategy or a "follow the carbon" strategy, or what... One thing that is understood by all sides in such a debate is that there needs to be a strategy of some sort, there needs to be a program of research. This means having some conception (or "supposition", as Paul Wally says) of what the possibilities are...The strategy of feasible exploration, suffices.
Suppositions are superfluous.

Colin Robinson
2012-Jul-15, 07:33 AM
Hmm .. yet another speculative response with a bunch of 'ifs' (or leading assumptions).

Here's one that's not speculative: The existence of life on Earth, does not imply life exists elsewhere.

Earth may not be unique at the scales of, and in the attributes you mention ... and that implies nothing about life.

??? But the scale I mentioned was the planets of the universe, and the only attribute I mentioned was presence of life...

Logically, non uniqueness of Earth at that scale, and in that attribute, must surely imply presence of life somewhere else?

Colin Robinson
2012-Jul-15, 07:40 AM
The strategy of feasible exploration, suffices.

What do you mean by a "strategy of feasible exploration"? Does it mean sending robotic probes, or humans, here and there at random thru the solar system, with no idea what they are looking for? That would be "feasible", and it would be "exploration" of a sort... Would that "suffice"? If so, what would it suffice for?


Suppositions are superfluous.

I have to disagree.

Parallel Universes
2012-Jul-15, 07:50 AM
I find it tragic that every discussion gets derailed by this discussion. The factions who want to argue about whether aliens exist are destroying the possibility of fresh discussion. How can we ever philosophise about the possible nature of otherworldly beings when the same nay sayers keep popping their heads up and shouting "HOGWASH!"

We get it. Ok. A minority of you simply can't get past this stumbling block. You would rather raise this same tired debate over and over rather than let a discussion unfold based on an assumption.

We once thought our individual nations were the centre of the world and all of creation. Clearly many of us still do.

Selfsim
2012-Jul-15, 08:07 AM
I find it tragic that every discussion gets derailed by this discussion. The factions who want to argue about whether aliens exist are destroying the possibility of fresh discussion. How can we ever philosophise about the possible nature of otherworldly beings when the same nay sayers keep popping their heads up and shouting "HOGWASH!"

We get it. Ok. A minority of you simply can't get past this stumbling block. You would rather raise this same tired debate over and over rather than let a discussion unfold based on an assumption.

We once thought our individual nations were the centre of the world and all of creation. Clearly many of us still do.Huh ?
If ever there was a thread to hammer this out .. its this one !

Your desire to "philosophise about the possible nature of otherworldly beings" would be the "derail" ... sorry to leave you in a 'tragic' state ... and all at your own calliing, I might add !

Paul Beardsley
2012-Jul-15, 08:49 AM
I find it tragic that every discussion gets derailed by this discussion. The factions who want to argue about whether aliens exist are destroying the possibility of fresh discussion. How can we ever philosophise about the possible nature of otherworldly beings when the same nay sayers keep popping their heads up and shouting "HOGWASH!"

We get it. Ok. A minority of you simply can't get past this stumbling block. You would rather raise this same tired debate over and over rather than let a discussion unfold based on an assumption.

We once thought our individual nations were the centre of the world and all of creation. Clearly many of us still do.

What Selfsim said, 100%. Parallel Universes, I suspect you might have got confused about which thread you were replying to.

Here on BAUT (as it was) we've had all manner of speculative discussion about possible extraterrestrial life. There was even one about whether other civilisations would listen to music. And whereas one or two people did indeed fail to "get it" (i.e. that the discussion was purely speculative) they did not derail the thread.

profloater
2012-Jul-15, 08:55 AM
This thread started about logic and assumptions. In fiction we can examine weird starting assumptions using logic and imagination. Usually fiction writers who then claim the details are factual are disapproved.

It is important to separate what we regard as evidence from extrapolation and imagination when using the mantle of logic to arrive at conclusions.

If we are separated by too many light years, the mathematical possibility of life on distant planets surely remains a subject for fiction, we cannot expect to find evidence.

Van Rijn
2012-Jul-15, 09:04 AM
Thinking about logical possibilities is fine ... but no progress will be made in the real world, (about the existence or otherwise of life elsewhere), unless such 'thinking' returns useful real-world data. I see the discussion of exolife, as not falling into any category of productive reasoning (deductive, inductive or abductive). The problem is there is no data that allows a conclusion to be formed, or allows the construction of a premise.


Are you referring to this thread, or all discussions about exolife?

When we study the universe, we make hypotheses based on known physics. Sometimes we've found things that didn't fit known physics, but a lot of it has. It has certainly been something to build on.

Similarly, if we're going to look for exolife (as I think everyone here agrees with the possibility of exolife and that it is a possibility that should be investigated, correct?) it would seem reasonable to make hypotheses based on known life. That doesn't stop anyone from considering other possibilities, but it would be a reasonable place to start.

chrlzs
2012-Jul-15, 10:19 AM
We don't know that.
Which is why I prefaced those comments with the 'as far as I am aware' bit..


We wouldn't know about other abiogenesis events unless they happened to have current and distinct descendents, or if there was something very distinct left in the fossil record. It's possible there have been multiple abiogenesis events on Earth.
But that is sorta my point - either:
1. There is/was one very precise, extremely unlikely set of conditions and chemicals from which life can appear - which is the one I'm betting on...
or
2. There is a range of conditions and chemicals, or if they are precise, those conditions were (even briefly) widespread - in which case we *would* very likely see distinct descendants (in a regional sense) / differing biochemistry / fossil records

Do we? AFAIK, we don't, and I think we probably should. I'll happily admit I'm not widely read on this aspect of abiogenesis, but I've never seen any references to multiple 'beginnings'. Perhaps the books that were cited give some clues, but it would be nice if this aspect got a bit of coverage here..


I would argue that we can't say very much about that based on current laboratory experiments. These laboratory experiments are extremely small scale compared to the planet over geological periods. Now, if you were conducting experiments with something like the volume of the Pacific Ocean, and you couldn't get results after a few hundred million years, then you might have a significant argument.
I'm not sure I agree. If we had no idea of what we are after, then yes, but we DO know what we are after! We have examples of the primitive starting points of life all around us - they are chemically analysable, we understand the basic processes, the chemical structures... It's a pretty good example of reverse engineering where you not only have the blueprints, you also have as many samples as you need to dissect / analyse..

Of course we can't quantify it meaningfully in mathematical terms, but I think it's fair to say it is really, really difficult to get life started. Maybe even a few more reallys...

So I stand by my point - saying that life is 'abundant' on Earth is misleading, in this context.

Selfsim
2012-Jul-15, 11:15 AM
Thinking about logical possibilities is fine ... but no progress will be made in the real world, (about the existence or otherwise of life elsewhere), unless such 'thinking' returns useful real-world data. I see the discussion of exolife, as not falling into any category of productive reasoning (deductive, inductive or abductive). The problem is there is no data that allows a conclusion to be formed, or allows the construction of a premise. Are you referring to this thread, or all discussions about exolife?I cannot speak of all discussions on exo-life (some are carefully worded to denote the speculative bases of what is being discussed), but I was referring generally to forum discussions involving speculations which presume the existence of exo-life, as a given.


When we study the universe, we make hypotheses based on known physics. Sometimes we've found things that didn't fit known physics, but a lot of it has. It has certainly been something to build on.

Similarly, if we're going to look for exolife (as I think everyone here agrees with the possibility of exolife and that it is a possibility that should be investigated, correct?) it would seem reasonable to make hypotheses based on known life. That doesn't stop anyone from considering other possibilities, but it would be a reasonable place to start.Sure, but don't forget the testability part of a proper hypothesis. In isolation, I don't challenge the 'reasonableness' of the general idea of looking for Earth-life, if one chooses to pursue the search for exo-life ... after all, there is no other choice once one embarks on such a quest. Carbon based biological life tests have to be conducted locally (or via return sample ... oh, SETI signals or ET poking faces at a robotic camera might suffice as well). This limits the practicality of the testing. Such tests cannot be applied over light year distances. This means that the hypothesis is severely constrained by practical testing limitations which ultimately limits the ability to gather the data, and form conclusions. No amount of 'reasonableness' (or logical reasoning) will overcome this practicality imposed limitation. Also, we simply don't have any data to make the firm connection between what we can measure these scales, and the presence/absence of life (whist excluding other unknown non-biological processes).

Using Physical theories to make exo-life hypotheses: the raw fundamental laws of physics dominate at astronomical scales, (and on astronomical objects), but in complex systems, their complex interactions can have entirely unexpected and unpredictable results. In the absence of any data on exo-life, it is also reasonable to say that deterministic physical theories can only be used to infer where exo-life may exist elsewhere (at best). Using Earth-life as a substitute for Physical Law as you have suggested, comes with all the limitations outlined above.

Regards

primummobile
2012-Jul-15, 12:57 PM
Why do you have to assume anything? My approach would be to make suppositions, not assumptions. Suppose X is true, what follows if X is true? Suppose X is false, what follows etc.
There's a difference between making assumptions and making suppositions. Look, I just supposed X and then I supposed not(X) (no problem), but it would be irrational to assume both X and not(X).

For me, science operates at the level of supposition (not assumption), and that's where all the interesting (original) work is going on. I think it's far more interesting to have a rational discussion around different suppositions around alien life, than to have these dead-end discussions about who assumed what, and what can be assumed, and what can be said and what cannot be said. Sometimes these type of dead-end discussions even lead to restrictions on what can be thought and what cannot be thought, and this I find quite strange, because why must lack of evidence for something prevent us from thinking about the different logical possibilities?

That's my whole point. That I am NOT assuming. I started this thread based upon the belief that others were assuming no life exists.

primummobile
2012-Jul-15, 01:30 PM
a) Colin: Why is this a key issue? I would've thought the key issue would have been whether life is special1?
b) Initial conditions: There is theoretical evidence that the observable universe started out chaotically. Randomness and order would seem at home in the aftermath .. and it is !
c) Primummobile: 'Mathematically unlikely: Could you please demonstrate for us, the mathematics behind such a statement ? I keep seeing 'mathematics' being used to make a point, and yet there is nothing from mathematics I know of, which would suggest that such a statement is anything more than pure arm-waving and a hijack of mathematics.


Footnotes:
1. I dislike using the term 'special' .. something unique, doesn't have to be 'special'. That being said, I only used the term as a quote of what was said.


I said IF THE EARTH IS NOT SPECIAL, and you may substitute unique for that, the mathematical odds would seem to indicate thrlere may be other life. Latest estimates put the number of stars in the observable universe to be anywhere from 10 sextillion to 1 septillion. If other stars have planets we would consider habitable, (ie Earth is not unique, part of the original premise ) then the chances of finding exo life increases every time you find another earth. I'm not going to do any hand waving and pull numbers out of the air like Drake or Sagan always did. But I can say this: if the likelihood of life developing was equal to rolling a "six" on a six-sided die then the universe should be teeming with life. If, on the other hand, the likelihood of life devoloping is equal to a deck of cards being randomly shuffled and come up in one particular order, then you could say that it is unlikely for there to be other life in the universe. The real likelihood is somewhere in the middle of those two extremes. There is no equation to make because we would have to guess at the numbers. But it still remains that if A sometimes causes B, the more iterations you have of A the more likely you are to have outcome B. There is nothing difficult about that.

You are attacking a straw man here. I didn't say that I assumed anything. Again, I am saying is it better to assume life does not exist because of the lack of evidence, or ia it better to NOT assume life does NOT exist because we just don't have the information to assume ANYTHING. I don't know how many ways I can say this. I'm guessing we may have pretty close to the same opinion on this matter. Not assuming = assuming nothing.

primummobile
2012-Jul-15, 01:40 PM
You said It was just my opinion that the views being taken by some was too minimalist. i.e. "extraterrestrial life does not exist because we have seen no evidence of it."

I said I read the thread in question - I must have missed the bit where somebody said that. Can you provide the quotation?

Obviously, I meant the quotation that supported your claim that some were being too minimalist.

You then gave me a load of quotations, none of which support your claim that some were being too minimalist, none of which stated or implied "extraterrestrial life does not exist because we have seen no evidence of it." So perhaps you can withdraw the claim now.

Ok, one more time. I was saying that someone else was assuming NOTHING. (All he is saying is that you should NOT assume life does not exist. ) The reply was "why not assume that"? In other words, assuming life does not exist. I provided the other quotes to give you context to the conversation. Whether or not how I am reading it is what they meant is the feason, I started this thread. As I have not received an answer to that question yet, it would be a little difficult to retract my assertation.

primummobile
2012-Jul-15, 01:55 PM
Selfsim, I was typing on my phone, and I now see that I left out something in my last post. I had meant to say that if habitable planets are nothing special that the real chances were probably somewhere between the two extremes I happened to mention. I don't want you to think that I am claiming to know any kind of number because the whole point is that I don't and neither does anyone else.

mutleyeng
2012-Jul-15, 04:11 PM
Selfsim, I was typing on my phone, and I now see that I left out something in my last post. I had meant to say that if habitable planets are nothing special that the real chances were probably somewhere between the two extremes I happened to mention. I don't want you to think that I am claiming to know any kind of number because the whole point is that I don't and neither does anyone else.

you cant make a case with numbers and then expect it not to be challenged just because you finish by saying "i dont know and neither does anyone else". Whether you intended to or not, you made a case as to why it is more likely that other life exists than not. That is not a neutral position. That is what i suspect Selfsim meant about being careful how you phrase yourself.
You end by saying you dont know, but in the text you slip in that the mathematical odds suggest there is other life - Thats what is getting the reaction. You said you wernt going to do any hand waving of numbers, and then you went right ahead and did it. ETA ok, you used a math argument without the numbers- no better

Colin Robinson
2012-Jul-15, 11:34 PM
But that is sorta my point - either:
1. There is/was one very precise, extremely unlikely set of conditions and chemicals from which life can appear - which is the one I'm betting on...
or
2. There is a range of conditions and chemicals, or if they are precise, those conditions were (even briefly) widespread - in which case we *would* very likely see distinct descendants (in a regional sense) / differing biochemistry / fossil records

Do we? AFAIK, we don't, and I think we probably should. I'll happily admit I'm not widely read on this aspect of abiogenesis, but I've never seen any references to multiple 'beginnings'. Perhaps the books that were cited give some clues, but it would be nice if this aspect got a bit of coverage here..

I'm not sure I agree. If we had no idea of what we are after, then yes, but we DO know what we are after! We have examples of the primitive starting points of life all around us - they are chemically analysable, we understand the basic processes, the chemical structures... It's a pretty good example of reverse engineering where you not only have the blueprints, you also have as many samples as you need to dissect / analyse..

Of course we can't quantify it meaningfully in mathematical terms, but I think it's fair to say it is really, really difficult to get life started. Maybe even a few more reallys...

So I stand by my point - saying that life is 'abundant' on Earth is misleading, in this context.

There are two questions here:

1. What conclusions can be drawn from the fact that abiogenesis has not be duplicated in laboratories?
2. What about the fact that abiogenesis appears to have occurred only once on this Earth? Why hasn't it been repeated?

1. I think it's a little arrogant of us humans to suppose that something difficult for us must be difficult for nature. For instance, we have yet to make a practical fusion reactor. Whereas nature has made billions, we call them "stars".

2. Maybe because the first organisms cornered the market in easily available energy? That is, they began by taking advantage of the most easily processed chemical energy sources (like a mixture of substances containing both H2 and CO2). Afterwards some of their descendants evolved to use more difficult energy sources like photosynthesis (where you transform light energy into chemical energy, before doing something with the chemical energy), and reactions involving O2 (a challenging stuff to use, because of its tendency to break down life's building blocks, the organic compounds)...

I have another, more general issue with your argument...

Either the Earth is a typical example of what happens on a habitable planet, or it isn't. If Earth is a typical example, then life gets started exactly once on other habitable planets too. On the other hand, if Earth is not typical, why should we suppose that on other habitable planets life typically gets started less times than here? Why not more times?

Selfsim
2012-Jul-16, 12:19 AM
Selfsim, I was typing on my phone, and I now see that I left out something in my last post. I had meant to say that if habitable planets are nothing special that the real chances were probably somewhere between the two extremes I happened to mention. I don't want you to think that I am claiming to know any kind of number because the whole point is that I don't and neither does anyone else.Well, I think we're roughly on the same page … however, the point needs to be made that the 'numbers game' is a meaningless argument, because the existence of life on Earth, does not imply life exists elsewhere … and this remains no matter how many 'habitable' planets/moons exist out there.

One can portray conditional 'ifs' and possibles' as much as one likes, (usually done to lead others to a desired outcome), but the inescapable fact is, as I've stated above. The mathematical language which follows, (ie: the chances, odds, etc, etc), is not particularly relevant when one sets the initial 'going-in' conditions in concrete, beforehand.

Regards

Colin Robinson
2012-Jul-16, 01:22 AM
Well, I think we're roughly on the same page … however, the point needs to be made that the 'numbers game' is a meaningless argument, because the existence of life on Earth, does not imply life exists elsewhere … and this remains no matter how many 'habitable' planets/moons exist out there.

Is it logically possible for billions of planets to be habitable, yet uninhabited by any sort of life? Yes, it is possible... but the existence of even one habitable-yet-lifeless planet is at present a supposition, a conjecture, and not an established empirical fact...


One can portray conditional 'ifs' and possibles' as much as one likes, (usually done to lead others to a desired outcome),

Do we want discussion about life in the universe to avoid words such as "if" and "possible"? Would that be rigor? Or rigor mortis?

Selfsim
2012-Jul-16, 02:49 AM
Is it logically possible for billions of planets to be habitable, yet uninhabited by any sort of life? Yes, it is possible... but the existence of even one habitable-yet-lifeless planet is at present a supposition, a conjecture, and not an established empirical fact…Well, there are already a couple of planets which have 'habitable zones', but alas, there are no human beings sending us probes and radio signals from them.

I know ! There must be exceptions !

Under such rationale, will it ever be possible to confirm 'no life' on 'billions of habitable planets' (/moons) ?
Will it ever be practically possible to search every HZ on a such a set of planets, in order to make such a confirmation ? If not, the hypothesis is unverifiable from a practical perspective, and is not a workable hypothesis. (It is falsifiable in practice however .. which demonstrates the bias, yet again).

The statement: "the existence of life on Earth, does not imply life exists elsewhere", on the other hand, is demonstrably present-day fact, and is falsifiable and verifiable in practice, even when projected into an uncertain future.


Do we want discussion about life in the universe to avoid words such as "if" and "possible"? Would that be rigor? Or rigor mortis?Whatever ..

Colin Robinson
2012-Jul-16, 03:55 AM
Is it logically possible for billions of planets to be habitable, yet uninhabited by any sort of life? Yes, it is possible... but the existence of even one habitable-yet-lifeless planet is at present a supposition, a conjecture, and not an established empirical fact...Well, there are already a couple of planets which have 'habitable zones', but alas, there are no human beings sending us probes and radio signals from them.


Do you really think "No human beings sending us probes and radio signals" is the same thing as "uninhabited by any sort of life"? Doesn't the category "life" include things like aardvarks, and baobab trees, and yaks, and zooxanthellae?


I know ! There must be exceptions !

If life has appeared only on Earth, that would make Earth an extreme exception.


Under such rationale, will it ever be possible to confirm 'no life' on 'billions of habitable planets' (/moons) ?
Will it ever be practically possible to search every HZ on a such a set of planets, in order to make such a confirmation ? If not, the hypothesis is unverifiable from a practical perspective, and is not a workable hypothesis. (It is falsifiable in practice however .. which demonstrates the bias, yet again).

The statement: "the existence of life on Earth, does not imply life exists elsewhere", on the other hand, is demonstrably present-day fact, and is falsifiable and verifiable in practice, even when projected into an uncertain future.

"Falsifiability" was one of the favorite concepts of Karl Popper, the great philosopher of science. Were you aware of that, Selfsim? I find it funny that you use the term so much, even though you think scientific discussion should avoid philosophy...

Van Rijn
2012-Jul-16, 06:03 AM
Which is why I prefaced those comments with the 'as far as I am aware' bit..


I was referring to the statement, "In all the time before or since, no other life has sprung into existence." That isn't something that can be concluded based on existing evidence. Evidence points to life starting at least once, but it could have started multiple times.




But that is sorta my point - either:
1. There is/was one very precise, extremely unlikely set of conditions and chemicals from which life can appear - which is the one I'm betting on...
or
2. There is a range of conditions and chemicals, or if they are precise, those conditions were (even briefly) widespread - in which case we *would* very likely see distinct descendants (in a regional sense) / differing biochemistry / fossil records


I don't agree those are the only options, and I definitely don't agree with the argument in item 2. Most species don't fossilize well (certainly most bacteria do not) and it's hard to say much about biochemistry unless there are currently living examples. So many things could be missed. Also, if there had been examples of distinctly alternate life, they might have disappeared for many reasons. They might never have had a large ecological niche. They could have been out competed, or faded out when conditions changed, or just could have been unlucky.


Do we? AFAIK, we don't, and I think we probably should. I'll happily admit I'm not widely read on this aspect of abiogenesis, but I've never seen any references to multiple 'beginnings'.


It is sometimes discussed as a possibility. Remember the Mono lake "arsenic life"? That turned out to be wrong, but folks were hoping that would be an example of an alternate path for life.



I'm not sure I agree. If we had no idea of what we are after, then yes, but we DO know what we are after! We have examples of the primitive starting points of life all around us


Sorry, but we don't. In any scientific abiogenesis argument, it's agreed there would have been simpler life forms than any that currently exist. See for instance:

http://exploringorigins.org/protocells.html




Of course we can't quantify it meaningfully in mathematical terms, but I think it's fair to say it is really, really difficult to get life started. Maybe even a few more reallys...


Again, we don't know that. There's a lot about abiogenesis we've yet to learn.

It could be, after we work out some more details, that we'll be able to repeat abiogenesis in the lab when anyone wants to. One day it might become a common school experiment. Or maybe we'll never get there.

We might find life on Mars. Or we might not.

It could turn out that abogenesis is virtually certain in conditions similar to that of early Earth. Or it may be that it would be uncommon, rare, extremely rare, or unique. All of those options would fit existing evidence.

Van Rijn
2012-Jul-16, 06:25 AM
I cannot speak of all discussions on exo-life (some are carefully worded to denote the speculative bases of what is being discussed), but I was referring generally to forum discussions involving speculations which presume the existence of exo-life, as a given.


Around here, people usually get an argument if they make that assumption. :)




Sure, but don't forget the testability part of a proper hypothesis. In isolation, I don't challenge the 'reasonableness' of the general idea of looking for Earth-life, if one chooses to pursue the search for exo-life ... after all, there is no other choice once one embarks on such a quest. Carbon based biological life tests have to be conducted locally (or via return sample ... oh, SETI signals or ET poking faces at a robotic camera might suffice as well). This limits the practicality of the testing. Such tests cannot be applied over light year distances. This means that the hypothesis is severely constrained by practical testing limitations which ultimately limits the ability to gather the data, and form conclusions. No amount of 'reasonableness' (or logical reasoning) will overcome this practicality imposed limitation. Also, we simply don't have any data to make the firm connection between what we can measure these scales, and the presence/absence of life (whist excluding other unknown non-biological processes).


But our abilities to study exoplanets will continue to improve. If scientists find many Earthlike (and I mean really Earthlike exoplanets - not worlds with five times the mass, or with Venus-like insolation) having a combination of properties associated with life that would be very hard to explain without life, then the most reasonable explanation is that there is life on those planets.

Selfsim
2012-Jul-16, 07:49 AM
But our abilities to study exoplanets will continue to improve. If scientists find many Earthlike (and I mean really Earthlike exoplanets - not worlds with five times the mass, or with Venus-like insolation) having a combination of properties associated with life that would be very hard to explain without life, then the most reasonable explanation is that there is life on those planets.Oh .. I'm under no misapprehension about that being very likely to happen. That is the stage which has been set for us. But we're expected to accept that life exists on another planet light years away on the basis of an inferred model ?

That might work in classical scientific astronomy circles, (which is dominated by classical Physical Laws), but somehow I can't see it being acceptable when it comes to explaining the existence of complex exo-life. (Y'know ... something about 'extraordinary claims requiring extraordinary evidence' ..??..). I mean for instance, how can one state that science has a complete enough knowledge to rule out other, as yet unknown, natural processes capable of generating so called 'bio-signs' remotely detectable from such an environment ?

Frankly to assume that it will be accepted, seems naive in the extreme !
And what happens when it isn't accepted ? What then ? Nothing is capable of making a trip of light-year distances to gather 'first-hand' data. How will society cope with that ? Is it scientifically responsible to make such an extraordinary claim on the basis of nothing more than an incomplete inferred model, which is based purely on Earth-like conditions ?
You mention the arsenic-based claim ... that would pale into miniscule obscurity in comparison with an exo-life claim based purely on inference !

Has anyone really thought all this through, or are we simply expected to blindly follow the lead set for us by hyped up mass media ?

iquestor
2012-Jul-16, 11:05 AM
Oh .. I'm under no misapprehension about that being very likely to happen. That is the stage which has been set for us. But we're expected to accept that life exists on another planet light years away on the basis of an inferred model ?

That might work in classical scientific astronomy circles, (which is dominated by classical Physical Laws), but somehow I can't see it being acceptable when it comes to explaining the existence of complex exo-life. (Y'know ... something about 'extraordinary claims requiring extraordinary evidence' ..??..). I mean for instance, how can one state that science has a complete enough knowledge to rule out other, as yet unknown, natural processes capable of generating so called 'bio-signs' remotely detectable from such an environment ?

Actually, it should be possible to directly infer or at least provide strong arguments for life processes at work through spectroscopy in 10-15 years. Kepler is finding many cadidates for Earth analogs, showing that reasonably Earthlike Planets (small, rocky planets around similar stars within the liquid water region) are not uncommon. Spectroscopic analysis of light diffracted through the atmosphere (where they exist) of these planets can show the presence of CHON, evidence of photosynthetic processes, and other indicators of life. Detection of artifical elements and compounds in the atmosphere would provide almost irrefutable evidence of industrial intelligent life. See Dr. Garik Israelian's TED Talk See Dr. Garik Israelian's TED Talk (http://www.ted.com/talks/garik_israelian_what_s_inside_a_star.html)


If you see, in the spectrum of a planet host star, strange chemical elements, it can be a signal from a civilization which is there.” (Garik Israelian)
If there is abundant life on one of these planets it is not out of the question that we could provide strong evidence for it using remote technology such as Spectroscopy.

kzb
2012-Jul-16, 11:52 AM
If we are talking about life only, then your only logical position at present is an open mind. The observations to collect any supporting or negating evidence have not been done yet. Hopefully this will be forthcoming in our lifetimes, but probably not absolute proof in either direction.

There will be some interesting evidence from our own solar system, maybe life will be found on Mars or Europa, and then the discussion will centre on whether it has a joint origin with Earth life or not. If it definitely has independent origin, the logical conclusion must be that life is commonplace in the universe.

If we are talking about intelligent, technological life, after our model, then there is plenty of logic that says this is incredibly rare. The central argument being, it would be obvious if we were living in a galaxy-wide civilisation. Lots of people are unconvinced by this argument, citing the extreme difficulty of interstellar travel and communication.

But I personally think we've got the MW at least all to ourselves. It's really comes down to just opinion at this stage of the argument, and we've been round the houses on this several times on here.

primummobile
2012-Jul-16, 12:26 PM
you cant make a case with numbers and then expect it not to be challenged just because you finish by saying "i dont know and neither does anyone else". Whether you intended to or not, you made a case as to why it is more likely that other life exists than not. That is not a neutral position. That is what i suspect Selfsim meant about being careful how you phrase yourself.
You end by saying you dont know, but in the text you slip in that the mathematical odds suggest there is other life - Thats what is getting the reaction. You said you wernt going to do any hand waving of numbers, and then you went right ahead and did it. ETA ok, you used a math argument without the numbers- no better

I'm not trying to make a case. I am trying to ask a question. Is it better to assume nothing, because the only thing going for that is the numbers involved? Is it better to assume life does not exist, because we have not seen any evidence. Which is more persuasive? The ambiguity of the numbers involved is EXACTLY the reason I am asking the question.

This is simple probability theory. They start teaching it in junior high. In any random system, most things have a probability of happening. We assign it a value of between 0 and 1, with 0 meaning it cannot ever happen. 1 means it is a certainty. Personally, I don't know of any events that would be assigned a 0 or 1. Everything I know of is between the two.

If quantum mechanics is true, there is a non-zero probability that if you walk into a wall you will pass right through it. It's awfully close to zero, but it's still not. I don't know what the probability is, but i do know that you would have to wait much longer than the lifetime of the universe before you would actually see it happen. The point I was making is that it doesn't matter what the initial probability is. If it's one in a googol, and you walk into the wall twice, you have doubled the chances you will walk through the wall. Whatever the probability of it happening, your chances are still doubled. I'm asking if the mathematical probability argument is enough to let us assume anything. I'm not saying the numbers increase the probability to closer to 1, because I don't know the answer to that.

As for life in space, we don't know most of the parameters of what we would expect to possibly cause life. The only thing we know is that, unless the universe was designed, the probablility of life arising is not zero. If after we take all the parameters that we do not know into account, and we find that the probability of life arising is equal to the probability of a deck of cards being shuffled and coming out arranged in one particular order, which is 1 in 52!, we would expect to not find any other life. In fact, it would make it surprising that life is even here, since 52! is 43 orders of magnitude larger than the largest estimate I have seen for the number of stars in the universe. But even if those were the odds, two planetary systems with all parameters being equal would still give you twice the chance that one would give you. A million planetary systems of the type needed would give you a million times the chance. It would still be a miniscule chance, (1 in 8.06x10^61 instead of 1 in 8.06x10^68) but your chances are increasing with every instance of the right planetary system.

I'm getting frustrated with this because no one can see that I am not presenting this as evidence of anything. It should be obvious to anyone that the more "stuff" the universe has in it, the more chances you have for life developing. It may be a good chance, or it may be a not-so-good chance. That is why I opened the thread with the questions. They involve a whole lot of different things, and I wanted to have a discussion about it without it getting sidetracked by people asking me for numbers that I wasn't claiming to know. It would involve things like:

1) Is it logical to assume nothing about exo life?
a) Is the probability of other life, while increasing with each new planetary system, so low that we shouldn't expect to see a second instance of it yet?
b) Is the earth unique or special?
c) How many ways could life develop?
All of these deal with the probability of life developing in a random system. I just wanted to have a discussion about it without people asking for equations that no one on the planet can produce since we don't know any of the parameters.

or

2) Based on the lack of evidence, can it be assumed that we are alone?

That's it. No demands for math to prove that probability increases with frequency. No stuff about retracting statements when no one has told me explicitly what they meant. No interpreting my gut feeling to mean that I am advocating a position, because I'm not. This may have started by something I misunderstood, but that doesn't make the question any less valid.

primummobile
2012-Jul-16, 12:47 PM
Selfsim, after reading through what you wrote since I was last on here, I am clear about what you meant. So I withdraw the assertation that you were claiming no other life exists.

mutleyeng
2012-Jul-16, 01:55 PM
This is simple probability theory. They start teaching it in junior high.


yes i know the argument...really i do.
I just dont think its a valid argument, or a needed one as I didnt think people here denied the possibility of other life anyway.

primummobile
2012-Jul-16, 02:48 PM
yes i know the argument...really i do.
I just dont think its a valid argument, or a needed one as I didnt think people here denied the possibility of other life anyway.

I'm not implying that you or anyone else doesn't understand probability. I'm pointing out that I'm talking about only simple probability like they teach to kids, not making any claims about what the probability actually is, or when in multiple instances of favorable planetary systems you would expect to see the first occurrence.

Think of it this way. We know that there is a non-zero chance of life arising in a random system with our physical laws because we know it has happened at least once. I'm asking if the chance is closer to 1 or closer to 0 in similar planetary systems with similar stars. Or would a completely different biochemistry be more likely to develop?

Now, you answered the question, that you don't think it is a valid argument. So do you think the probability is close to 0?

mutleyeng
2012-Jul-16, 02:56 PM
Now, you answered the question, that you don't think it is a valid argument. So do you think the probability is close to 0?

I have absolutely no idea - double the number of supposed environments and i would still have no idea. Use any multitude you wish and i would still have no idea.

Paul Wally
2012-Jul-16, 06:05 PM
Thinking about logical possibilities is fine ... but no progress will be made in the real world, (about the existence or otherwise of life elsewhere), unless such 'thinking' returns useful real-world data.

How so? Theory makes predictions which can be tested empirically in the real world.


I see the discussion of exolife, as not falling into any category of productive reasoning (deductive, inductive or abductive). The problem is there is no data that allows a conclusion to be formed, or allows the construction of a premise.

There already exists a premise to work from; established scientific theory. The question is: What follows from established scientific theory?




(Similarly, the lack of data cannot in itself, be considered as a valid basis for formulation of the premise that exo-life doesn't exist either, as this leads to the logical fallacy of 'argumentum ad ignorantium').

You don't seem to understand the nature of the problem. Why must exo-life existence be formulated as a premise?? Exo-life existence/ non-existence is a possible conclusion of some premise. The premise could then be something like the laws of nature as formulated in our currently established scientific theories. The problem is then, roughly, something like: Do these laws of nature make the emergence of life a likely/unlikely occurrence? Possible conclusions are:
1) Life is an unlikely occurrence.
2) Life is a likely occurence.
3) The question of the emergence of life is undecidable on the premise.

Note that undecidability is something that will have to be proven mathematically, perhaps a Godel-type undecidability, but this hasn't been proven to my knowledge. You keep mentioning that some assume "classical physics", but say we take classical physics as our premise; has any of the above-mentioned conclusions been proven to follow from classical physics? If not, then we cannot say that the assumption of classical physics leads to the conclusion (2): "Life is a likely occurrence". Classical physics does however predict the existence of chaos, so your view that there is some fundamental incompatibility between classical physics and chaos is pure myth, but it's a myth that you strongly believe in because it holds your arguments together.

Van Rijn
2012-Jul-16, 08:15 PM
But we're expected to accept that life exists on another planet light years away on the basis of an inferred model ?


Why not, if the evidence is strong and there aren't any good non-biological models that would fit the evidence? We accept the existence of exoplanets based on evidence and models, why would this be different?



That might work in classical scientific astronomy circles, (which is dominated by classical Physical Laws), but somehow I can't see it being acceptable when it comes to explaining the existence of complex exo-life. (Y'know ... something about 'extraordinary claims requiring extraordinary evidence' ..??..).


What would be so extraordinary about a claim of life on an Earthlike world as compared to a claim of exoplanets around other stars? Reasonable standards for evidence should be expected, naturally, but I'm not aware of any good scientific argument for why there shouldn't be life on Earthlike worlds. It would be no more extraordinary than many other claims that have been accepted based on supporting evidence.



I mean for instance, how can one state that science has a complete enough knowledge to rule out other, as yet unknown, natural processes capable of generating so called 'bio-signs' remotely detectable from such an environment ?


How can we rule out other explanations for the evidence we believe points to exoplanets? Maybe it's all an illusion, and there are no exoplanets.

It is important to be careful, be sure you have solid evidence, and verify there are no reasonable alternative explanations for the evidence. But if you reject solid evidence when there are no reasonable alternative explanations, you're no longer looking at this scientifically.


Has anyone really thought all this through, or are we simply expected to blindly follow the lead set for us by hyped up mass media ?

Yes, many of us have thought this through.

Selfsim
2012-Jul-16, 09:53 PM
Think of it this way. We know that there is a non-zero chance of life arising in a random system with our physical laws because we know it has happened at least once. I'm asking if the chance is closer to 1 or closer to 0 in similar planetary systems with similar stars. Or would a completely different biochemistry be more likely to develop?

Now, you answered the question, that you don't think it is a valid argument. So do you think the probability is close to 0?No, its not a valid argument - far from it, in fact.

Firstly what is the 'random system' and how does this apply to life in our observable universe ? The physics of our obs. universe at astronomical scales, is certainly dominated by the known fundamental forces, described by a set of physical laws and constants, which have overwhelming empirical supporting evidence … and yet uniqueness and diversity are abundant. There are radically different effects at different scales (eg: quantum effects at small scales .. classical effects at planetary and upwards … relativistic at near light speeds … chaotic at everyday scales … (the list goes on)) .. All this renders physical predictability far from a 'given'.

Secondly, if you are assuming the parent population of the distribution of life in the obs. universe to be a normal one, there is no evidence of that. As a matter of fact, there is measured evidence that the distribution of galaxy clusters is fractal … so at the galaxy cluster level, the distribution of hypothesised life, (under current also invalid assumptions of being galaxy cluster-bound with a one-to-one correspondence), would be fractal with dimension around 2 .. which vastly differs from a normal distribution .... so, once again your assumptions about the parent distribution, renders the subsequential analysis inappropriate and moot (at one's most forgiving). Scale dependency exists !

Thirdly, we know of only one occurrence of life on Earth … there is no 'least' in 'one'. 'One' is fact. 'Least' is an unsupported speculative premise .. whereas it is actually stated as 'fact' in your post above .. !...

Statistics do not reveal 'truths'.
The answer to your question of Mutleyeng, based on the above real-world evidence-based rationale, is a definitive and emphatic: "Unknown" !

Colin Robinson
2012-Jul-16, 11:04 PM
First, the Nessie or Sasquatch question. I was using those as examples of an absurdity. Namely, that no one here is advocating any of the absurd claims that you see from cryptozoologists, but I don't see a real distinction between how some react to cryptozoology claims and how they react to claims that extraterrestrial life exists... We almost universally reject the notion that sasquatch exists because we have explored almost every square foot of the land surface of the earth and never found any evidence to confirm his existence, yet we have found evidence of all other types of life spanning billions of years. Therefore, it is absurd to assume Sasquatch exists because the overwhelming evidence says he does not.

In the case of Sasquatch, we have clear and overwhelming evidence of absence. In the case of alien life, what we have is absence of evidence.

Perhaps another key difference between aliens and sasquatch is this...

As you've mentioned, the proposition that extraterrestrial life does not exist, logically implies that the planet Earth is special -- radically exceptional, in fact. By contrast, the proposition that sasquatch does not exist, does not logically imply anything about a particular place being exceptional.

primummobile
2012-Jul-17, 12:06 AM
Perhaps another key difference between aliens and sasquatch is this...

As you've mentioned, the proposition that extraterrestrial life does not exist, logically implies that the planet Earth is special -- radically exceptional, in fact. By contrast, the proposition that sasquatch does not exist, does not logically imply anything about a particular place being exceptional.

That's a good point.

primummobile
2012-Jul-17, 12:14 AM
No, its not a valid argument - far from it, in fact.

Firstly what is the 'random system' and how does this apply to life in our observable universe ? The physics of our obs. universe at astronomical scales, is certainly dominated by the known fundamental forces, described by a set of physical laws and constants, which have overwhelming empirical supporting evidence … and yet uniqueness and diversity are abundant. There are radically different effects at different scales (eg: quantum effects at small scales .. classical effects at planetary and upwards … relativistic at near light speeds … chaotic at everyday scales … (the list goes on)) .. All this renders physical predictability far from a 'given'.

Secondly, if you are assuming the parent population of the distribution of life in the obs. universe to be a normal one, there is no evidence of that. As a matter of fact, there is measured evidence that the distribution of galaxy clusters is fractal … so at the galaxy cluster level, the distribution of hypothesised life, (under current also invalid assumptions of being galaxy cluster-bound with a one-to-one correspondence), would be fractal with dimension around 2 .. which vastly differs from a normal distribution .... so, once again your assumptions about the parent distribution, renders the subsequential analysis inappropriate and moot (at one's most forgiving). Scale dependency exists !

Thirdly, we know of only one occurrence of life on Earth … there is no 'least' in 'one'. 'One' is fact. 'Least' is an unsupported speculative premise .. whereas it is actually stated as 'fact' in your post above .. !...

Statistics do not reveal 'truths'.
The answer to your question of Mutleyeng, based on the above real-world evidence-based rationale, is a definitive and emphatic: "Unknown" !

Sorry, but nothing can convince me that our existence is due to anything but random chance. Our physical lawz do govern much of how the universe unfolds, but we can't just rule out all the randomness. The quantum realm is rife with randomness and that eventually leads to randomness in ever larger systems. Uniqueness does not imply something isn't random. It implies that there are many different ways for the universe to unfold.

I also don't see any distinction between "one" and "at least one". If I say that I have at least one dollar, it means that I have one dollar and I may have more. If I say I have one dollar, it means I have one. But until I find that second dollar I will never have any more than just one dollar.

What you say does intrigue me, though. I will give it some thought.

Selfsim
2012-Jul-17, 12:49 AM
Is it logically possible for billions of planets to be habitable, yet uninhabited by any sort of life? Yes, it is possible... but the existence of even one habitable-yet-lifeless planet is at present a supposition, a conjecture, and not an established empirical fact…Under such rationale, will it ever be possible to confirm 'no life' on 'billions of habitable planets' (/moons) ?
Will it ever be practically possible to search every HZ on a such a set of planets, in order to make such a confirmation ? If not, the hypothesis is unverifiable from a practical perspective, and is not a workable hypothesis. (It is falsifiable in practice however .. which demonstrates the bias, yet again).

The statement: "the existence of life on Earth, does not imply life exists elsewhere", on the other hand, is demonstrably present-day fact, and is falsifiable and verifiable in practice, even when projected into an uncertain future."Falsifiability" was one of the favorite concepts of Karl Popper, the great philosopher of science. Were you aware of that, Selfsim? I find it funny that you use the term so much, even though you think scientific discussion should avoid philosophy...So, now it seems, there is wry amusement through ignoring (and undermining) the distinctly different, evidence based, applied philosophical tenets of scientific methodology, in order to defend a fundamentally flawed attempt at a scientific hypothesis, presented embedded in an inference based wrapper ?

A classic reaction to exposure through scientific rigour … and precisely why:

I see the discussion of exolife, as not falling into any category of productive reasoning (deductive, inductive or abductive). The problem is there is no data that allows a conclusion to be formed, or allows the construction of a premise.

Selfsim
2012-Jul-17, 12:57 AM
I also don't see any distinction between "one" and "at least one". If I say that I have at least one dollar, it means that I have one dollar and I may have more. If I say I have one dollar, it means I have one. But until I find that second dollar I will never have any more than just one dollar.

What you say does intrigue me, though. I will give it some thought.Have a read through this thread (from my post #89 onwards) (http://cosmoquest.org/forum/showthread.php/132352-Evidence-and-belief?p=2020727#post2020727). Caveman1917 explains the basis of validity (from a mathematical principals perspective).

Colin Robinson
2012-Jul-17, 01:41 AM
So, now it seems, there is wry amusement through ignoring (and undermining) the distinctly different, evidence based, applied philosophical tenets of scientific methodology, in order to defend a fundamentally flawed attempt at a scientific hypothesis, presented embedded in an inference based wrapper ?

If your intention is to apply philosophical tenets of scientific methodology, then I respectfully suggest that you take the philosophy of science a little more seriously. I'd specifically suggest that you have a look what Karl Popper says about the relation between falsifiability and conjecture (or "supposition" as Paul Wally calls it), for instance in Popper's book Conjectures and Refutations.

Selfsim
2012-Jul-17, 09:01 AM
But our abilities to study exoplanets will continue to improve. If scientists find many Earthlike (and I mean really Earthlike exoplanets - not worlds with five times the mass, or with Venus-like insolation) having a combination of properties associated with life that would be very hard to explain without life, then the most reasonable explanation is that there is life on those planets.
But we're expected to accept that life exists on another planet light years away on the basis of an inferred model ?Why not, if the evidence is strong and there aren't any good non-biological models that would fit the evidence? We accept the existence of exoplanets based on evidence and models, why would this be different?Well, you've qualified the hypothetical scenario under the assumption of 'strong evidence'. Strong evidence would be prior biological test results, sourced from some local planet other than Earth, (after all, we are talking about biology as the subject, aren't we ?), or perhaps evidence sourced from some kind of lab synthesised, second abiogenesis, or the reception of an intelligible SETI signal(s), ET(s) poking faces into a remotely monitored robotic camera, etc, etc.

I am dubious about the non-existence of 'any good non-biological models that would fit the evidence', but, for the sake of the hypothetical, I'll go a long with it.

The existence of life on Earth, does not imply life exists elsewhere, is a present-day fact. It needs to be countered with falsifying new evidence of equal 'weight'. If this is presented, then I see no problems overturning the statement.



That might work in classical scientific astronomy circles, (which is dominated by classical Physical Laws), but somehow I can't see it being acceptable when it comes to explaining the existence of complex exo-life. (Y'know ... something about 'extraordinary claims requiring extraordinary evidence' ..??..).What would be so extraordinary about a claim of life on an Earthlike world as compared to a claim of exoplanets around other stars? Reasonable standards for evidence should be expected, naturally, but I'm not aware of any good scientific argument for why there shouldn't be life on Earthlike worlds. It would be no more extraordinary than many other claims that have been accepted based on supporting evidence.In the case of a firm conclusion of exo-life, I think there's a clear need for way more justification, over and above what is needed to support the claim of the discovery of 'Earth-like worlds'. The weight of hundreds of years of observational evidence and physical theory, leading onto planetary development theory, and repeatable local tests on the measurement techniques, tightly constrains interpretation of the measured data, which serves to eliminate uncertainties. Similar constraints don't exist for exo-life, particularly when it comes to the details of the 'precise' environmental conditions when life emerged. (Admittedly, there are constraints for steady-state existence however, in the form of critical sensitivities to environmental habitability).

Anyway, theoretically, there still exists the case of an Earth-like planet which has no life. This scenario still requires evidence in order for it to be eliminated, thus allowing for the firm exo-life conclusion. (I guess this comes back to the no 'good non-biological models to fit the evidence' ... ). In this same category, there is also a class of dynamic system where the tiniest difference in initial conditions (on any scales), could make all the difference in the outcome of a subsequent 'trial'. If life is hypothesised to have emerged from such a system, (and I'm not saying it did), then it would also require elimination from consideration, in order to conclude life (at least in theory). How would one go about doing this ..?.. (same answer as above, I guess).


How can we rule out other explanations for the evidence we believe points to exoplanets? Maybe it's all an illusion, and there are no exoplanets..... The weight of hundreds of years of observational evidence and physical theory, leading onto planetary development theory, and repeatable local tests on the measurement techniques, tightly constrains interpretation of the measured data. Similar constraints don't exist for exo-life.
(If you were fishing for Astrophysical/Astronomy ATM from me, you won't find it .. unless I've made an unintentional error somewhere … :) )


It is important to be careful, be sure you have solid evidence, and verify there are no reasonable alternative explanations for the evidence. But if you reject solid evidence when there are no reasonable alternative explanations, you're no longer looking at this scientifically.Agreed .. who was rejecting any evidence ? In this case, there isn't any to reject. The explanation: 'Unknown' with accompanying solid evidence, is still a perfectly valid scientific state for something to be in.


Yes, many of us have thought this through.I look forward to seeing the evidence which might lead me to this conclusion. :)

Regards

Selfsim
2012-Jul-17, 11:01 AM
Thinking about logical possibilities is fine ... but no progress will be made in the real world, (about the existence or otherwise of life elsewhere), unless such 'thinking' returns useful real-world data.How so? Theory makes predictions which can be tested empirically in the real world. When I last checked, 'logical possibilities' (meaning pure speculations) are vastly different from proper theories the latter of which, I agree, should ultimately lead to useful real-world data.


There already exists a premise to work from; established scientific theory. The question is: What follows from established scientific theory?Which established scientific theory leads to the emergence of universal life ?


You don't seem to understand the nature of the problem. Why must exo-life existence be formulated as a premise?? It doesn't ! Did I say it had to ?
Exo-life existence/ non-existence is a possible conclusion of some premise. The premise could then be something like the laws of nature as formulated in our currently established scientific theories. The problem is then, roughly, something like: Do these laws of nature make the emergence of life a likely/unlikely occurrence? Specifically, which laws of nature, and which currently established scientific theories are you formulating your premise on ... and why ?


Possible conclusions are:
1) Life is an unlikely occurrence.
2) Life is a likely occurence.
3) The question of the emergence of life is undecidable on the premise.

Note that undecidability is something that will have to be proven mathematically, perhaps a Godel-type undecidability, but this hasn't been proven to my knowledge. You keep mentioning that some assume "classical physics", but say we take classical physics as our premise; has any of the above-mentioned conclusions been proven to follow from classical physics? If not, then we cannot say that the assumption of classical physics leads to the conclusion (2): "Life is a likely occurrence". But that's just my point ! The usage of purely classical physics theory, to justify either (1) or (2), is inappropriate.


Classical physics does however predict the existence of chaos,I would've said that mathematics exposed the existence of chaotic behaviours in theory. Measured data then confirmed its existence in nature. The expected determinism inherent in theoretical mathematics however, doesn't nessarily map across into the real world .. and that is one of the big lessons from Chaos Theory.
so your view that there is some fundamental incompatibility between classical physics and chaos is pure myth, but it's a myth that you strongly believe in because it holds your arguments together.Huh ?? Please explain further the concepts you are trying to express on my behalf !??!
I do not recognise them from your paraphrasing !

Paul Wally
2012-Jul-17, 04:07 PM
When I last checked, 'logical possibilities' (meaning pure speculations) are vastly different from proper theories the latter of which, I agree, should ultimately lead to useful real-world data.

Obviously what I'm referring to, are those logical possibilities consistent with established scientific theory. Say for instance that if models derived from established scientific theories of physics and chemistry predict a high exo-life likelihood would you then consider such a prediction to be "pure speculation" too? I wouldn't call it speculation if it just follows logically from such a premise, i.e.,if the conclusion follows logically from the premise then it's truth value is conditional on the truth value of the premise.


Which established scientific theory leads to the emergence of universal life ?

I didn't say that. What I'm saying is that if we take established scientific theories as our premise, then the question is: "What follows from established scientific theory?".
I explicitly phrased it as a question. How is it possible that you could have overlooked that?



It doesn't ! Did I say it had to ?Specifically, which laws of nature, and which currently established scientific theories are you formulating your premise on ... and why ?

This is what you said:

(Similarly, the lack of data cannot in itself, be considered as a valid basis for formulation of the premise that exo-life doesn't exist either, as this leads to the logical fallacy of 'argumentum ad ignorantium').

My point is, why would anyone attempt to formulate exo-life existence/ non-existence as a premise? Doesn't it make more sense to look at it as a possible conclusion of some premise?

On your question of "which laws of nature" I'm formulating my premise. Exactly which laws, is not really relevant in terms of my argument. Let's just call it X. Let's call "exo-life" L. The question would then be: Does X--> L? So I'm not formulating a premise. I'm explaining on a general level what the relation between premise and conclusion is, as far as it relates to the problem of life emergence.



Possible conclusions are:
1) Life is an unlikely occurrence.
2) Life is a likely occurence.
3) The question of the emergence of life is undecidable on the premise.

Note that undecidability is something that will have to be proven mathematically, perhaps a Godel-type undecidability, but this hasn't been proven to my knowledge. You keep mentioning that some assume "classical physics", but say we take classical physics as our premise; has any of the above-mentioned conclusions been proven to follow from classical physics? If not, then we cannot say that the assumption of classical physics leads to the conclusion (2): "Life is a likely occurrence". Classical physics does however predict the existence of chaos, so your view that there is some fundamental incompatibility between classical physics and chaos is pure myth, but it's a myth that you strongly believe in because it holds your arguments together.

But that's just my point ! The usage of purely classical physics theory, to justify either (1) or (2), is inappropriate.


On what basis are (1) and (2) "inappropriate"? All three are equally valid conjectures in the context of classical physics. To my knowledge, none of those three has been proven logically, and this doesn't imply that it cannot be logically proven. Only if (3) is proven can we say that the likelihood of exo-life is undecidable in classical physics.



I would've said that mathematics exposed the existence of chaotic behaviours in theory. Measured data then confirmed its existence in nature. The expected determinism inherent in theoretical mathematics however, doesn't nessarily map across into the real world .. and that is one of the big lessons from Chaos Theory. Huh ?? Please explain further the concepts you are trying to express on my behalf !??!
I do not recognise them from your paraphrasing !

Physical theory is mathematical at its core. You cannot separate mathematics from theory as you're doing, and what is "theoretical" mathematics supposed to refer to? Mathematics is theoretical. And how can mathematics be deterministic/ non-deterministic? If chaos theory is mathematical at it's core, how can it tell us how mathematics maps to the real world? How do we conceptualise this mapping transformation without mathematics? I suspect that this "big lesson" you've apparently learned from chaos theory is one big misconception.

Van Rijn
2012-Jul-18, 08:54 AM
Well, you've qualified the hypothetical scenario under the assumption of 'strong evidence'. Strong evidence would be prior biological test results, sourced from some local planet other than Earth, (after all, we are talking about biology as the subject, aren't we ?), or perhaps evidence sourced from some kind of lab synthesised, second abiogenesis, or the reception of an intelligible SETI signal(s), ET(s) poking faces into a remotely monitored robotic camera, etc, etc.


No. There is life on Earth. If you find evidence for things that would be reasonably explained by earthlike biology on earthlike worlds, but not reasonably explained by non-biological processes on an earthlike world, then you have strong evidence for life.


The existence of life on Earth, does not imply life exists elsewhere, is a present-day fact. It needs to be countered with falsifying new evidence of equal 'weight'.


What exactly is to be falsified? Let's apply this argument to exoplanets, going back a few years. Would you consider this a reasonable argument?

The existence of planets in the solar system does not imply planets exist elsewhere, is a present-day fact. It needs to be countered with falsifying new evidence of equal 'weight'.

I've earlier pointed out my disagreement with your implication claim. Now, it sounds like you're trying to argue for an assumption that life is unlikely, as opposed to an assumption of "we don't know yet." The existence of life would have to be established through reasonable evidence, but there is no non-life argument to falsify.

And, sorry, but life on Earth does have implications for life elsewhere. It doesn't guarantee that life exists elsewhere, but chemistry on Earth has implications for chemistry elsewhere, physics on Earth has implications for physics elsewhere, and so does Earth life (being based, after all, on chemistry and physics).


In the case of a firm conclusion of exo-life, I think there's a clear need for way more justification, over and above what is needed to support the claim of the discovery of 'Earth-like worlds'.


How Earth-like does it need to be? Sure, it isn't enough to say you have a planet that's roughly Earth's mass, but if you have multiple lines of evidence that would fit the results of Earth biology, but would not, taken together, be reasonably explainable by non-biological processes, would you say that was insufficient?

caveman1917
2012-Jul-18, 06:20 PM
We know that there is a non-zero chance of life arising in a random system with our physical laws because we know it has happened at least once.

That's incorrect, you cannot deduce prior probabilities that way. Suppose we have a game where you think of a natural number and i have to guess it. Suppose i get it right. Then we know the event "me getting it right" has happened at least once, but that doesn't mean there is a non-zero chance of that happening, the chance is identically zero.

But even if we did assume there is a non-zero chance of a random system having life then the distribution of life bearing systems could be approximated as a poisson distribution. This means there will be a chance that there is exactly one planet with life, and that chance can be made arbitrarily high by having an arbitrarily low chance per-system. Since you have no way to deduce that per-system chance, nor even deduce that it isn't zero, this probabilistic argument falls apart.

caveman1917
2012-Jul-18, 06:27 PM
Secondly, if you are assuming the parent population of the distribution of life in the obs. universe to be a normal one, there is no evidence of that.

Actually there is, it's called the central limit theorem. Given the combination of a sufficient number of independent identically distributed stochastic variables, the resulting distribution will approach a normal distribution. Because of the vast interstellar (and if not, intergalactic) distances, the chance of life appearing in one system is independent of it appearing in another. Since the same physical laws hold everywhere, the base distributions would be identical, and adding in the huge number of such independent systems the central limit theorem holds.

caveman1917
2012-Jul-18, 06:37 PM
Have a read through this thread (from my post #89 onwards) (http://cosmoquest.org/forum/showthread.php/132352-Evidence-and-belief?p=2020727#post2020727). Caveman1917 explains the basis of validity (from a mathematical principals perspective).

Not that i want to sidetrack this discussion as i may have done with the one being linked to, but i find it somewhat odd that you quote an explanation of mine as support for an incorrect application of it.

Let P equal "we know of only one" (what you say) and let Q equal "we know of at least one" (what primummobile said).

Then P \Rightarrow Q is true, and because (P \Rightarrow Q) \Leftrightarrow \neg P \vee Q that last statement is also true.

If you say that you are right and he is wrong then you state P \wedge \neg Q which is the negation of \neg P \vee Q (as P \wedge \neg Q \Leftrightarrow \neg (\neg P \vee Q)) and is thus false.

It is hypothetically possible that he is right and you are wrong (if we would know of some greater number than one), but not the other way around.

Selfsim
2012-Jul-19, 01:56 AM
Folks;

Due to the overwhelming number of responses requested by so many posters in this thread, I’m finding it extremely difficult to continue my part of this discussion given the amount of time I presently have available for responding. I also do not wish to appear to exhibit a greater than tolerable level of ‘tenacious’ behaviour, which would be required from this point onwards, (particularly with regard to a hypothetically-oriented exo-life discussion). I also have no desire to personally offend.

My position has been, and will continue to be, simply that the present state of knowledge on the question of the existence of exo-life, draws the generalised conclusion of ‘Unknown’. For me, this is a valid state, is clearly distinguishable from the speculative ‘exo-life exists’, or the equally speculative ‘exo-life does not exist’, and still allows for further exploration.

I find that many folk somehow relate this position to my attempting to rule out the speculative possibility that exo-life exists, which is not the point I’m making. Similarly, I am not attempting to rule out the speculative possibility for the non-existence of it, either. Thorough exploration of both of these views I find, results in a balanced view.

The key general point I'd like to make, is that present knowledge and speculation of any kind are distinguishable entities in science, and should be maintained that way, (in mind, and in conversation).

I’ve come to the conclusion that this medium for communications, when it comes to explaining this perspective is inadequate, as there is too much background and detail to cover. Frankly I’m surprised that so much is required, in order to explain an ‘Unknown’ state, coming from present knowledge.

As I presently have a choice of diplomatically, and respectfully, withdrawing from this discussion, for the benefit of preserving harmony by avoiding miscommunications within the community, and out of respect for those I have engaged with in this thread, I choose to exercise this option.

Kind regards

primummobile
2012-Jul-19, 03:15 PM
That's incorrect, you cannot deduce prior probabilities that way. Suppose we have a game where you think of a natural number and i have to guess it. Suppose i get it right. Then we know the event "me getting it right" has happened at least once, but that doesn't mean there is a non-zero chance of that happening, the chance is identically zero.

But even if we did assume there is a non-zero chance of a random system having life then the distribution of life bearing systems could be approximated as a poisson distribution. This means there will be a chance that there is exactly one planet with life, and that chance can be made arbitrarily high by having an arbitrarily low chance per-system. Since you have no way to deduce that per-system chance, nor even deduce that it isn't zero, this probabilistic argument falls apart.

I'm a little confused by what you mean, but I'd appreciate it if you could provide a critique about what I'm about to say...

In the game you reference, you are referring to natural numbers, which is an infinite set. If we changed it and said that I am thinking of a natural number between 1 and 10, inclusive, you would have a .1 probability of guessing it correctly on the first try if both my choice and your guess were truly random. In the next round, your chances of correctly guessing would be also .1, but the probability you would guess correctly twice in a row is .01, three times in a row .001, and so on. But you know that. I'm not seeing how you are equating the probability of guessing a number in an infinite set to a finite set.

As to my statement, I don't believe that there was an infinite set of possible quantum states to begin the universe, nor do I believe that there is an infinite set now. If I had a handful of dice and dropped them on the floor, there would be a finite number of ways they could land. It does not matter to my argument how many dice I have or what style they are. Any combination that could happen has a probability of happening. Now there are combinations, such as a six-sided die coming up a seven, that could not happen. But, if we were to see even one instance of a six-sided die coming up a seven, we would have to assume that the probability of that happening is not zero.

If you extend that to the universe, and an outside observer were to note that the formation of Earth and the development of life was impossible according to the physical laws of the universe, that observer would have to conclude that the probability of it happening is zero. But if he were to observe even one instance of that zero probability event occuring, he would have no choice but to conclude that the probability was, in fact, non-zero.

I guess it would help if you were to use examples from a finite set of possibilities to explain your thinking, if you would be so kind. Or just explain to me why it wouldn't matter if you had a finite set of possible outcomes versus an infinite set, if that is the case.

Thanks.

Paul Wally
2012-Jul-19, 03:24 PM
The process in between not knowing and knowing is what scientific research is all about. Now, there's not one correct process to follow, because it's a matter of heuristics. One way is to look at what we currently know and then to see what can be deduced from that. Does physics and chemistry, as we currently understand it, imply that life must be a common phenomenon? That is still an open question. To say that all we can conclude from our current state of knowledge is that the existence of exo-life is unknown, is like being presented with a mathematical problem and then coming to the conclusion that the solution is unknown!

primummobile
2012-Jul-19, 03:29 PM
Folks;

Due to the overwhelming number of responses requested by so many posters in this thread, I’m finding it extremely difficult to continue my part of this discussion given the amount of time I presently have available for responding. I also do not wish to appear to exhibit a greater than tolerable level of ‘tenacious’ behaviour, which would be required from this point onwards, (particularly with regard to a hypothetically-oriented exo-life discussion). I also have no desire to personally offend.

My position has been, and will continue to be, simply that the present state of knowledge on the question of the existence of exo-life, draws the generalised conclusion of ‘Unknown’. For me, this is a valid state, is clearly distinguishable from the speculative ‘exo-life exists’, or the equally speculative ‘exo-life does not exist’, and still allows for further exploration.

I find that many folk somehow relate this position to my attempting to rule out the speculative possibility that exo-life exists, which is not the point I’m making. Similarly, I am not attempting to rule out the speculative possibility for the non-existence of it, either. Thorough exploration of both of these views I find, results in a balanced view.

The key general point I'd like to make, is that present knowledge and speculation of any kind are distinguishable entities in science, and should be maintained that way, (in mind, and in conversation).

I’ve come to the conclusion that this medium for communications, when it comes to explaining this perspective is inadequate, as there is too much background and detail to cover. Frankly I’m surprised that so much is required, in order to explain an ‘Unknown’ state, coming from present knowledge.


Kind regards

I get what you are saying, and I respect that. I just want to point out, in the hopes that you read this, that I don't disagree with you in principle. I just think it is interesting to speculate about what could be, all the while knowing that speculation is distinct from knowledge. For lack of a better way to put it, my gut tells me that there is probably other intelligent life out there. But it also tells me that other intelligent life is probably either exceedingly rare or short lived. When I present an "argument for" that belief, it would be more rightly interpreted as an "argument for why it is not impossible."

You don't know me, but I like to discuss possibilities. Astrophysicists theorize about quark stars, and have even worked out formulae for how a quark star would form and what we would expect to see. But we have never observed a quark star. When I was in junior high, I was taught that black holes were merely mathematical curiousities of GR. That information I was being taught may have been dated, but it still, at one time, represented the mainstream view. We have enough information, from the earth and universe around us, to make guesses as to how things could develop. They may be unlikely and they may not be very rigorous. But it's still interesting to speculate about.

caveman1917
2012-Jul-19, 11:27 PM
If we changed it and said that I am thinking of a natural number between 1 and 10, inclusive, you would have a .1 probability of guessing it correctly on the first try if both my choice and your guess were truly random. In the next round, your chances of correctly guessing would be also .1, but the probability you would guess correctly twice in a row is .01, three times in a row .001, and so on.

True, but we don't know the prior distribution of life-bearing systems. And the evidence we have (life on earth) is perfectly correlated with our existence and therefor useless.

Let's try an example with a dice. Suppose that you want to find the prior distribution over the result of throwing it (ie how fair the dice is) and in order to do that you throw the coin. However suppose that the probability of say 4 given that you throw it is 1. You throw the dice and it lands 4, that didn't give you any information about the distribution. Likewise the probability that there is at least one planet with life given that we are conducting the survey is 1, so that data point does not give any information as to the actual distribution of life-bearing planets. So while it's true that for a finite set the probability is not zero, it can still be arbitrarily small, we didn't constrain it. For that we need evidence that is not correlated with our existence. And a bigger sample.

primummobile
2012-Jul-19, 11:57 PM
True, but we don't know the prior distribution of life-bearing systems. And the evidence we have (life on earth) is perfectly correlated with our existence and therefor useless.

Let's try an example with a dice. Suppose that you want to find the prior distribution over the result of throwing it (ie how fair the dice is) and in order to do that you throw the coin. However suppose that the probability of say 4 given that you throw it is 1. You throw the dice and it lands 4, that didn't give you any information about the distribution. Likewise the probability that there is at least one planet with life given that we are conducting the survey is 1, so that data point does not give any information as to the actual distribution of life-bearing planets. So while it's true that for a finite set the probability is not zero, it can still be arbitrarily small, we didn't constrain it. For that we need evidence that is not correlated with our existence. And a bigger sample.

Ok, I really don't have an argument with that. My point was more along the lines that, because of our existence, we know that our physical laws don't preclude the possibility of life existing.

Paul Wally
2012-Jul-20, 01:41 AM
Ok, I really don't have an argument with that. My point was more along the lines that, because of our existence, we know that our physical laws don't preclude the possibility of life existing.

Yes, we know that our physical laws (if they are a true reflection of reality) do not preclude the possibility of life. My preferred approach, however, is not to attempt a statistical inference from the fact that there's life on Earth but rather, to look at the physical laws and how they make life possible. It is this how-question that I find more interesting than the question of whether or not other life exists. Initially, I think that some kind of simple model must be constructed based on these physical laws or perhaps much simpler laws. Then, "life" must be defined, beginning with a simple definition e.g. life is any structure that can self-replicate and evolve. The model must then be adjusted until "life", as defined emerges. But, the life-outcome must emerge implicitly, and not be explicitly coded within the model. Once such a simple model is discovered, it can be studied further mathematically so that a more general abstract theory can be developed and further refined through application to empirical reality.

You're probably familiar with the field of artificial life, where life-like phenomena in the form of computer simulations are studied. What I would like to see in such studies is an example of artificial abiogenesis, where self-replicating and evolvable artificial organisms emerge from a system wherein no artificial organisms existed prior to emergence. Such a model, even if just a toy-model, should give some valuable insights into the general nature of abiogenesis.

Colin Robinson
2012-Jul-21, 05:09 AM
True, but we don't know the prior distribution of life-bearing systems. And the evidence we have (life on earth) is perfectly correlated with our existence and therefor useless.

I'd agree that we can't conclude very much from the fact that the planet we live on has life. That much, I grant you, is perfectly correlated with our existence. Perhaps a more significant point is how long Earth has had life. As mentioned by the OP of this thread


We know that life on earth arose almost immediately after the Late Heavy Bombardment, which is probably just about as early as it was able to exist.

From studying the fossil record we know it is possible for a habitable planet to lack intelligent life. Earth has been like that for nearly all its history. We also know it is possible for a habitable planet to be inhabited by unicellular life only. Earth was like that for billions of years. So there would be little reason for surprise if we find another world with life but no intelligent life, or if we find one inhabited by unicellular life only.

What we don't know is whether there is, or ever has been, a habitable world uninhabited by anything. It is logically conceivable, yes. But there is, as yet, no empirical example of such a world. If we find one, it will be a scientific breakthrough -- we will then know that the probability of life on a habitable world is less than 1.

ZunarJ5
2012-Jul-21, 05:20 AM
Disclaimer - This thread has a lot of material... I'm pretty sure this post isn't covering old ground, but I may have missed something.

Something that may be significant when figuring the probabilities or determining the logic either for or against the existence and/or frequency of exolife; AFAIK, life has not been synthesized definitively from base chemical components. Amino acids on their own do not count. PLEASE, correct me if I am wrong, I would be fascinated to find out if I am.

If this is true... why? There must be something we are missing in either our assumptions about he conditions of primordial Earth or about the basic components of life. If we have the right materials, and we have the right conditions... shouldn't we be able to create life? What am I missing?

Colin Robinson
2012-Jul-21, 06:00 AM
Disclaimer - This thread has a lot of material... I'm pretty sure this post isn't covering old ground, but I may have missed something.

Something that may be significant when figuring the probabilities or determining the logic either for or against the existence and/or frequency of exolife; AFAIK, life has not been synthesized definitively from base chemical components. Amino acids on their own do not count.

You're right -- the simplest known life is vastly more intricate that amino acids. And there hasn't been a full laboratory demonstration of how it got started.


If this is true... why? There must be something we are missing in either our assumptions about he conditions of primordial Earth or about the basic components of life. If we have the right materials, and we have the right conditions... shouldn't we be able to create life? What am I missing?

A somewhat similar point actually was raised earlier in this thread by chrisz. Van Rijn responded:


I would argue that we can't say very much about that based on current laboratory experiments. These laboratory experiments are extremely small scale compared to the planet over geological periods. Now, if you were conducting experiments with something like the volume of the Pacific Ocean, and you couldn't get results after a few hundred million years, then you might have a significant argument.

primummobile
2012-Jul-21, 01:42 PM
Disclaimer - This thread has a lot of material... I'm pretty sure this post isn't covering old ground, but I may have missed something.

Something that may be significant when figuring the probabilities or determining the logic either for or against the existence and/or frequency of exolife; AFAIK, life has not been synthesized definitively from base chemical components. Amino acids on their own do not count. PLEASE, correct me if I am wrong, I would be fascinated to find out if I am.

If this is true... why? There must be something we are missing in either our assumptions about he conditions of primordial Earth or about the basic components of life. If we have the right materials, and we have the right conditions... shouldn't we be able to create life? What am I missing?

I agree with Colin's take on this. I would like to add that I'm inclined to believe that life arose more than once on the ancient earth, and that most of those were simply not viable long enough to develop a stable population and so did not survive. While our physical laws do govern how things can happen, I also think that the seemingly random nature of the universe also has something to do with what things do happen. There's nothing to say that RNA-based molecules are the only form of life that initially arose, and I'd be surprised if that was the only kind because when something is random (as I believe it was) it's unlikely for there to be only one possible solution. The only thing you can expect is a best solution, or to put it better, a more successful solution.

So, it's possible that we could develop life in a laboratory and simply not recognize it as life because we weren't looking for the right thing. Also, as Colin said, when we talk about the early earth, we're talking about geological time scales. What is a blink of an eye to the Earth is a very long time to us. I think we haven't been able to produce life in the laboratory because in those time scales many different things can happen that we aren't accounting for.

primummobile
2012-Jul-21, 02:29 PM
Yes, we know that our physical laws (if they are a true reflection of reality) do not preclude the possibility of life. My preferred approach, however, is not to attempt a statistical inference from the fact that there's life on Earth but rather, to look at the physical laws and how they make life possible. It is this how-question that I find more interesting than the question of whether or not other life exists. Initially, I think that some kind of simple model must be constructed based on these physical laws or perhaps much simpler laws. Then, "life" must be defined, beginning with a simple definition e.g. life is any structure that can self-replicate and evolve. The model must then be adjusted until "life", as defined emerges. But, the life-outcome must emerge implicitly, and not be explicitly coded within the model. Once such a simple model is discovered, it can be studied further mathematically so that a more general abstract theory can be developed and further refined through application to empirical reality.

You're probably familiar with the field of artificial life, where life-like phenomena in the form of computer simulations are studied. What I would like to see in such studies is an example of artificial abiogenesis, where self-replicating and evolvable artificial organisms emerge from a system wherein no artificial organisms existed prior to emergence. Such a model, even if just a toy-model, should give some valuable insights into the general nature of abiogenesis.

I didn't reply to this earlier because I am a little confused by the last part. When I think of something artificial, I am thinking of something created by another entity. So, I'm not sure how that something arising spontaneously could be considered artificial. I think you could be getting at something a little different, but you probably need to elaborate on what you are saying, if you would.

As to the other, I understand what you are saying. But I think that the first step is establishing that our physical laws don't preclude life elsewhere. When that is established we may speculate on the genesis of other life. But I am a pessimist in that regard. I'm not naturally inclined to look for the path. Rather, I am inclined to look for the roadblocks on the path. I think a combination of both approaches is probably the best.

Paul Wally
2012-Jul-21, 06:46 PM
I didn't reply to this earlier because I am a little confused by the last part. When I think of something artificial, I am thinking of something created by another entity. So, I'm not sure how that something arising spontaneously could be considered artificial. I think you could be getting at something a little different, but you probably need to elaborate on what you are saying, if you would.

It would be artificial in the sense that some algorithms are defined in a computer program. It was discovered that in some of these programs very simple rules of interaction between multiple agents can lead to complex pattern formation, for example Conway's game of life cellular automata. So the purely mathematical discovery is that some simple rules of interaction can lead to complex pattern formation.

I take it that with "something arising spontaneously" you refer to what I said about artificial abiogenesis. What I mean by that is not actual life in the real world, but something emerging purely from within the computer program, as I explained above with complex pattern formation. But firstly, "life" must be defined. Initially, I think, this definition is not going to be the actual definition of life (in the real world) but a very oversimplified definition. The idea is to define certain rules and then to see whether life, according to the oversimplified definition emerges from those rules. Once a model like this is discovered, in a sense, it could then be studied mathematically in order to get some kind of mathematical concept of the emergence of life-like phenomena.



As to the other, I understand what you are saying. But I think that the first step is establishing that our physical laws don't preclude life elsewhere. When that is established we may speculate on the genesis of other life. But I am a pessimist in that regard. I'm not naturally inclined to look for the path. Rather, I am inclined to look for the roadblocks on the path. I think a combination of both approaches is probably the best.

My approach would be to do the above kind of general mathematical/computational study and then to apply the generic concepts learned in that study to the specific physical laws. This approach might help with establishing whether our physical laws don't preclude life, as you say. I'm more inclined to look for a path! Any path will give us something to study mathematically, and perhaps give us some idea as to what the path/s might be. I'm not quite clear on what you mean by "roadblocks" though; could you perhaps clarify that concept for me?

primummobile
2012-Jul-21, 08:47 PM
My approach would be to do the above kind of general mathematical/computational study and then to apply the generic concepts learned in that study to the specific physical laws. This approach might help with establishing whether our physical laws don't preclude life, as you say. I'm more inclined to look for a path! Any path will give us something to study mathematically, and perhaps give us some idea as to what the path/s might be. I'm not quite clear on what you mean by "roadblocks" though; could you perhaps clarify that concept for me? I was hoping you wouldn't ask me to clarify that! But I'll try. While you are looking for the path, I am taking any path you find and examining it for problems. My wife tells me that I am a "Debbie Downer", but I don't think I am. I think people like me are needed because being a pessimist allows me to see things other people might miss. At the same time, I may not see the way to get there because I'm hung up on the problems. That's why I said that a combination of the two works best.

I'm not saying that your approach is not valid, or that I don't ever do that. I'm just saying that I'm inclined to look at it as "why couldn't this happen" as opposed to "how could this happen". If I am able to establish first that there is nothing saying something couldn't happen, in this case-the emergence of life- then I am free to look at it how it could happen.

We're probably getting too bogged down in the details here.

I do have comments to make about the artificial thing, but you need to let me stew on them for a while. I do find it interesting, though... and it is something I have given thought to.

headrush
2012-Jul-22, 10:34 PM
I was hoping you wouldn't ask me to clarify that! But I'll try. While you are looking for the path, I am taking any path you find and examining it for problems. My wife tells me that I am a "Debbie Downer", but I don't think I am. I think people like me are needed because being a pessimist allows me to see things other people might miss. At the same time, I may not see the way to get there because I'm hung up on the problems. That's why I said that a combination of the two works best.

I'm not saying that your approach is not valid, or that I don't ever do that. I'm just saying that I'm inclined to look at it as "why couldn't this happen" as opposed to "how could this happen". If I am able to establish first that there is nothing saying something couldn't happen, in this case-the emergence of life- then I am free to look at it how it could happen.

We're probably getting too bogged down in the details here.

I do have comments to make about the artificial thing, but you need to let me stew on them for a while. I do find it interesting, though... and it is something I have given thought to.

I agree with your point of view. If one is to succeed in a venture, it is important to examine the potential for failure. Otherwise time is wasted in redesigning later to overcome such issues. Some people see that as a negative attitude, I see it as profoundly positive, because the job gets done more quickly and is more likely to be successful. I like to do a job properly.

But then some people I know say I have an attitude problem. When describing events at work I might say " I was performing this task when I was interrupted and had to perform another task". They then say that the other task was more important so my use of the term "interrupted" indicates my focus is wrong. Not at all, interrupted is interrupted. Words have taken on too many social aspects and connotations to be really as useful as they could be, which is why maths is the language of science.

I would say there is no logic in assuming the nonexistence of ET life. The main question might be better phrased as - how many times has life arisen in the universe ?
Then we get down to the argument over the difference between one and at least one. For myself, at least means the minimum, which in this case is one So I would answer, life has arisen in the universe at least once.
We don't know any more, so that is a fair statement. It would not be fair to say only once, without exploring the entire universe. Only implies a conclusive figure, unless you qualify it with "that we know of".
Let the semantics begin (again) :-)

primummobile
2012-Jul-23, 02:59 PM
I agree with your point of view. If one is to succeed in a venture, it is important to examine the potential for failure. Otherwise time is wasted in redesigning later to overcome such issues. Some people see that as a negative attitude, I see it as profoundly positive, because the job gets done more quickly and is more likely to be successful. I like to do a job properly.

But then some people I know say I have an attitude problem. When describing events at work I might say " I was performing this task when I was interrupted and had to perform another task". They then say that the other task was more important so my use of the term "interrupted" indicates my focus is wrong. Not at all, interrupted is interrupted. Words have taken on too many social aspects and connotations to be really as useful as they could be, which is why maths is the language of science.

I would say there is no logic in assuming the nonexistence of ET life. The main question might be better phrased as - how many times has life arisen in the universe ?
Then we get down to the argument over the difference between one and at least one. For myself, at least means the minimum, which in this case is one So I would answer, life has arisen in the universe at least once.
We don't know any more, so that is a fair statement. It would not be fair to say only once, without exploring the entire universe. Only implies a conclusive figure, unless you qualify it with "that we know of".
Let the semantics begin (again) :-)

I don't have any semantics arguments for you, especially since we agree. If you don't have "negative" people looking for problems you can waste a lot of time on a path that will turn out to be fruitless.