Evidence for ET is mounting daily, but not proven.

[Colin Robinson]

well, as a member of the public, i found Pilchers quote in the article to be overzealous...
The quote from Chris McKay in the same article read like a much more realistic (responcible) thing to say.

Is there such a big difference between Pilcher's statement

The evidence is just getting stronger and stronger...I think anybody looking at this evidence is going to say, 'There's got to be life out there.'

and McKay's?

There are real things we can point to and show that being optimistic about life elsewhere is not silly.

It's true that they use different words. Pilcher says "evidence", McKay says "real things we can point to".

But isn't that what "evidence" is -- real stuff you can point to that show a particular view is not unreasonable?

There is a subtle, but important difference between evidence and proof...

Evidence "is information that helps form a conclusion". Proof is "factual information that verifies a conclusion". (From http://www.thefreedictionary.com/evidence)

Do you disagree with these definitions of evidence and proof? If so, may I see your definitions?

[djellison]

There is a HUGE different between 'There's got to be life out there' and 'being optimistic about life elsewhere is not silly'

Now - both are simply opinions - they are not scientific conclusions of any sort - but one is orders of magnitude more certain...indeed, the first is frankly untenable given the fact there is no evidence of ET life. There is evidence of a building blocks, habitability, but none of actual life itself.

To hold the first view, imho, you need evidence of life itself. To hold the second just requires evidence of building blocks and habitability.

[mutleyeng]

needless to say colin, i agree with the above post.
One is saying youd have to be a complete whacko conspiracy theory nut job not to accept there is life out there-
the other is saying, hey we have reason to do the exploration to see if there is.

I am exagerating a little....but only a little

[mutleyeng]

to answer the direct question re evidence/proof.
I have no problem with your definitions.
the problem with you trying to break it down like that is that you are conflating evidence of one thing to imply evidence of something else.
Pilchers words seem do that ...that evidence of things such as potential habitat is conflated into evidence of life.
McKays words do not do that

[Paul Beardsley]

Q. When is a green dog most likely to enter a house?

A. When the door is open.

We are discovering more and more houses with open doors. We haven't yet seen a green dog.

[Jeff Root]

There is a HUGE different between 'There's got to be life out
there' and 'being optimistic about life elsewhere is not silly'

There *may* be a huge difference. But the two people who
made those statements *may* have meant exactly the same
thing by them in context. I could use them that way.

Now - both are simply opinions - they are not scientific
conclusions of any sort -

They are opinions based on science. That is, they are rational
extrapolations from observations.

but one is orders of magnitude more certain...

How many orders of magnitude?

indeed, the first is frankly untenable given the fact there is
no evidence of ET life.

I have no problem holding it.

There is evidence of a building blocks, habitability, but none
of actual life itself.

Terrestrial life is life. There is evidence of life. One instance
isn't much, but it is enough.

To hold the first view, imho, you need evidence of life itself.

If you reject terrestrial life as evidence of life, then your
opinion is wrong, because I hold the first view despite the
absence of any evidence of life according to your definition
of "evidence of life".

I'll repeat what I said last year, near the start of this thread:
There isn't any known good evidence *of* extraterrestrial life,
but there is lots of evidence *for* extraterrestrial life, and it
is mounting practically if not actually daily, as the thread
title asserts.

-- Jeff, in Minneapolis

[djellison]

w

there is lots of evidence *for* extraterrestrial life

Cite it.

There is evidence of phenomenon that COULD be explained by extraterrestrial life - but as far as I know there is none that could ONLY be explained by extraterrestrial life.

[Jeff Root]

there is lots of evidence *for* extraterrestrial life

Cite it.

Just one, to start with. I don't consider the request
to be worth much effort at this point.

Other suns exist than ours. That is evidence which
supports the expectation that extraterrestrial life exists.
In other words, it is evidence for extraterrestrial life.

-- Jeff, in Minneapolis

[Selfsim]

They are opinions based on science. That is, they are rational
extrapolations from observations.

What says that 'extrapolation from observations' is a valid, rational 'operation', (when it comes to predicting exo-life) ?

The thing being tested is the 'idea' that there may be a 'standard' model of life.
If exo-life is discovered, the model may then have some validity.
But until exo-life is discovered, that model ONLY has validity for making predictions here on Earth ... nowhere else.
It is thus not valid, nor rational, to 'extrapolate', and make predictions of any degree of certainty, from model which has only one data point.

Regards

[djellison]

Just one, to start with. I don't consider the request
to be worth much effort at this point.

Other suns exist than ours. That is evidence which
supports the expectation that extraterrestrial life exists.
In other words, it is evidence for extraterrestrial life.

-- Jeff, in Minneapolis

Seriously? Umm - that doesn't speak to extraterrestrial life at all. It's evidence that there may be other habitable worlds, but it doesn't say one single thing about if they are inhabited or not. Seriously - that's NOT evidence for ET life - not even slightly.

It's no more valid to say that than to say me owning a toolbox is evidence I own allen keys.

Guess what....I don't own allen keys. I could...I have a place where they might go - but the fact that I have such a place doesn't in any way infer if I do or not.

Other suns existing is NOT evidence of ET life. Period.

[Colin Robinson]

There is a HUGE different between 'There's got to be life out there' and 'being optimistic about life elsewhere is not silly'

Now - both are simply opinions - they are not scientific conclusions of any sort - but one is orders of magnitude more certain...indeed, the first is frankly untenable given the fact there is no evidence of ET life. There is evidence of a building blocks, habitability, but none of actual life itself.

To hold the first view, imho, you need evidence of life itself. To hold the second just requires evidence of building blocks and habitability.

I'm glad you mentioned the building blocks. They are relevant and important. But are building blocks and habitable places the only reasons for considering life beyond Earth as a serious possibility?

I'll quote from the NASA statement about scientific goals of the MSL rover...

MSL will also be able to evaluate the concentration and isotopic composition of potentially biogenic atmospheric gases such as methane, which has recently been detected in the modern atmosphere.

(This is the statement cited by Selfsim in post 744)

"Biogenic" means produced by living things. "Potentially biogenic" means possibly produced by living creatures.

The presence of potentially biogenic features on a planet is a completely different question from its habitability.

[Colin Robinson]

Q. When is a green dog most likely to enter a house?

A. When the door is open.

We are discovering more and more houses with open doors. We haven't yet seen a green dog.

There are plenty of houses without dogs, no matter what color. Are there habitable worlds without organisms?

As far as I know, just one habitable world has been examined by biologists with any thoroughness. And they've found organisms all over it. Though not green dogs.

[djellison]

The presence of potentially biogenic features on a planet is a completely different question from its habitability.

Yup - and the presence of potentially biogenic features is a completely different thing from the presence of features that can ONLY be biogenic.

One suggest ET life is possible. One is evidence it exists.

We have a few of the first. We have none of the second.

[Jeff Root]

Other suns exist than ours. That is evidence which
supports the expectation that extraterrestrial life exists.
In other words, it is evidence for extraterrestrial life.

Seriously?

Yes. Seriously.

The final line of your post shows that you don't get it.

Umm - that doesn't speak to extraterrestrial life at all.

Yes it does.

It's evidence that there may be other habitable worlds, but it
doesn't say one single thing about if they are inhabited or not.

Correct. Exactly correct.

The fact that other suns exist -- determined over the course of
the 17th through 19th centuries -- is evidence that there may be
other planets than those around our Sun. And indeed, such
planets have been discovered in the last decade or so.

The fact that extrasolar planets exist is evidence that there may
be other habitable worlds (whatever "habitable" means). After
all, there can't be other habitable worlds if there aren't other
worlds.

I haven't examined the evidence fully enough to determine
whether it suggests that any of the other worlds should be
considered "habitable". But such "habitable" worlds appear
to be completely inevitable. It would be super-weird if they
did not exist. Billions of planets, but only one which could
support life? And that one lone planet which *could* support
life actually *does* support life? That would be totally freaky.

The existence of other "habitable" worlds would be evidence
that there may be other inhabited worlds. The near-certainty
that other "habitable" worlds exist is evidence that there may
be other inhabited worlds.

Seriously - that's NOT evidence for ET life - not even slightly.

Yes it is. Definitively and unambiguously.

It's no more valid to say that than to say me owning a toolbox
is evidence I own allen keys.

Guess what....I don't own allen keys. I could...I have a place where
they might go - but the fact that I have such a place doesn't in any
way infer if I do or not.

The wording of this assertion makes it somewhat ambiguous,
but I can say that your owning a toolbox *is* evidence that you
may own allen keys. That makes the wording parallel the
wording you used in the third sentence of your post. To use
my wording, your owning a toolbox is evidence for your owning
allen keys.

The fact that you have a toolbox shows that you have things.
Someone who has no things at all cannot own allen keys. Since
you have some things, you may have others. Even if you have
no allen keys in your toolbox, you may have one or more which
are not in your toolbox. I have thought of getting a set numerous
times, including just recently. None of the three keys which I've
acquired from various sources was the right size. I was able to
use a phillips screwdriver. I don't own a toolbox. I thought of
getting one of those recently, too.

Look around your place. I bet you'll find an allen key somewhere.

Of course, you said "keys", plural. Keep looking. You might find
another one. I keep the three I know I have together, but they
could easily become separated, and have in the past...

It seems tactically advantageous to pounce on a minor error and
point out that the word you meant was "imply", not "infer". It was
there, I might as well take advantage of it.

Other suns existing is NOT evidence of ET life. Period.

This is the line which prompted me to say above that you don't
get it. Although other suns existing is not evidence of ET life,
it certainly *is* evidence for ET life, and that is what the title of
this thread claims. It is also what I said in the text you quoted
that you were responding to.

-- Jeff, in Minneapolis

[mutleyeng]

somebody not accepting your line of reasoning as valid does not mean they do not understand the line of reasoning you are using.
i have no problem anyone on this forum believing that other life in the universe is just a given, using your line of reasoning.
What i have a problem with is the people doing the science presenting the same conclusion with the same reasoning...because it is BAD science.

[djellison]

Although other suns existing is not evidence of ET life,
it certainly *is* evidence for ET life, and that is what the title of
this thread claims.

No - it just is not. You're categorically wrong on this. You are saying that evidence of potential = evidence for. This is just not true.

Let me put it another way. A lack of preclusion of something is not evidence for it.

It's an odds game. Maybe a horse is standing on the start line with odds of 10-1.

You are stating that's evidence 'for' the horse winning.

The ONLY valid stance until that race is over is that we don't know. It might - but we simply do not know.

I think there could very well be life elsewhere in the universe. The sheer number worlds speaks volumes on the possibility of life. Is there evidence of many worlds? Yes. Is there evidence some are habitable? Yes.

Is there evidence that they are inhabited. No.

You are making a massive massive leap in essentially projecting evidence of habitability as evidence for life. It isn't. The possibility or even probability of something existing is not evidence for it.

The wording of this assertion makes it somewhat ambiguous,
but I can say that your owning a toolbox *is* evidence that you
may own allen keys.

Correct. I MAY own allen keys. It's possible, probable even.

To use
my wording, your owning a toolbox is evidence for your owning
allen keys.

Incorrect. That I own a toolbox says nothing about allen keys actually existing. Period. You have to open the toolbox and look at it before you can state that. It would be a good place to look - that's where they tend to be - but you have ZERO data about allen keys until you open that box. You have NO evidence for them at all. None.

This may be a pedantic or semantic argument - but I feel, very very strongly, that it is catastrophically wrong to say 'We have evidence for ET life'

We don't. We have evidence of places it might occur and things it might be made of. These do not amount to evidence for it.

[Paul Beardsley]

I totally agree with djellison over the last few posts.

If it turns out that djellison owns an allen key or two, chances are he keeps them in his toolbox. But the existence of the toolbox is not evidence of an allen key. Jeff's logic is not lined up in the correct order here. (I have forgotten the Latin term here - something like modus ponens. I'll look it up when I have time.)

Likewise, a planet found in a goldilocks zone (have we in fact discovered such a beast?) is merely the most likely location for a hypothetical lifeform. It does not in any sense strengthen a case for a lifeform being located there.

[Selfsim]

Likewise, a planet found in a goldilocks zone (have we in fact discovered such a beast?) is merely the most likely location for a hypothetical lifeform. It does not in any sense strengthen a case for a lifeform being located there.

It would seem it is perceived to:

i) strengthen the case, when coming from the optimistic perspective;
ii) be detrimental to the case, when coming from the pessimistic perspective.

Many notice that both of these, depend on preconceived subjective optimistic and pessimistic worldviews.

From a scientific perspective, both (i) and (ii) are totally meaningless, and independent of getting on with exploration, which is the only way to ultimately resolve the evolving opinionated argument.

Regards

[Colin Robinson]

This may be a pedantic or semantic argument - but I feel, very very strongly, that it is catastrophically wrong to say 'We have evidence for ET life'

We don't. We have evidence of places it might occur and things it might be made of.

We have evidence of places it might occur and things it might be made of. And also of things it might be doing, e.g. putting methane into the atmosphere of Mars.

These do not amount to evidence for it.

Found a quote that seems relevant, from Phil Plait. For anyone here who doesn't know, Phil is also known as the Bad Astronomer. He is a well-qualified professional astronomer, and an energetic campaigner against fringe theories, conspiracy theories etc. He is also (along with Fraser Cain of the Universe Today) one of the founder/owners of the forum BAUT.

Anyway, here is something which Phil wrote a couple of years ago about the question of life on Titan, and about the definition of evidence, and the distinction between evidence and proof.

First, have we found life on Titan? No. Have we found evidence that there might be life on Titan? Sorta. The results are preliminary and not yet confirmed; in fact, some of the evidence is from computer modeling and has not been directly observed. Bear in mind as well that evidence is not proof. Evidence just means an observation was made that is consistent with life...

Source: No, we haven't found life on Titan Emphasis as in original, with underlining in place of italics.

[Paul Beardsley]

So we sort of have evidence that there might be life of Titan? And that somehow equates to "we have evidence of extraterrestrial life"?

[mutleyeng]

and in the article by phil plait, he provides a link to a responce to the speculation by Chris McKay.
in that responce, he says that it is not evidence "of" life,
and his conclusions are,
(note the list in order of likely reality.)

"In conclusion, there are four possibilities for the recently reported findings, listed in order of their likely reality:

1. The determination that there is a strong flux of hydrogen into the surface is mistaken. It will be interesting to see if other researchers, in trying to duplicate Strobel's results, reach the same conclusion.

2. There is a physical process that is transporting H2 from the upper atmosphere into the lower atmosphere. One possibility is adsorption onto the solid organic atmospheric haze particles which eventually fall to the ground. However this would be a flux of H2, and not a net loss of H2.

3. If the loss of hydrogen at the surface is correct, the non-biological explanation requires that there be some sort of surface catalyst, presently unknown, that can mediate the hydrogenation reaction at 95 K, the temperature of the Titan surface. That would be quite interesting and a startling find although not as startling as the presence of life.

4. The depletion of hydrogen, acetylene, and ethane, is due to a new type of liquid-methane based life form as predicted (Benner et al. 2004, McKay and Smith 2005, and Schulze-Makuch and Grinspoon 2005)."

[Colin Robinson]

So we sort of have evidence that there might be life of Titan? And that somehow equates to "we have evidence of extraterrestrial life"?

Who is saying: "we have evidence of extraterrestrial life"?

The title of this thread says: "Evidence for ET is mounting... but not proven."

The hypothesis of methanogenic life on the surface of Titan, sufficiently prolific to do measurable things to atmospheric composition, is far from proven. But there is a growing set of observations consistent with that hypothesis.

A statement attributed to Isaac Asimov: "The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but rather 'hmm....that's funny...' "

"Hmm... that's funny" is pretty much what scientists are saying about Titan.

Am I the only one here who finds that sort of exciting?

[Colin Robinson]

and in the article by phil plait, he provides a link to a responce to the speculation by Chris McKay.
in that responce, he says that it is not evidence "of" life,
and his conclusions are,
(note the list in order of likely reality.)

4. The depletion of hydrogen, acetylene, and ethane, is due to a new type of liquid-methane based life form as predicted (Benner et al. 2004, McKay and Smith 2005, and Schulze-Makuch and Grinspoon 2005)."
[/I]

Chris McKay's response to the mid 2010 findings about Titan is indeed well worth reading.

It is appropriate that Chris McKay should respond to the "speculation" (as you call it), as he himself was one of the original "speculators"!

You see, the words you've quoted, "McKay and Smith 2005", refers to a paper co-authored by the same Chris McKay.

That is, back in 2005, Chris McKay found the idea of methanogenic life on Titan plausible enough to write a scientific paper about what observable consequences such life would have. The paper concluded that if such organisms were present, they would result in levels of hydrogen and acetylene markedly lower than otherwise expected. The argument was that living things need an energy source, and the likely energy source for Titan organisms would be a hydrogen-acetylene reaction.

Around June 2010, two papers by other scientists concluded that levels of both hydrogen and acetylene in Titan's atmosphere actually are anomalously low near the surface. D.F.Strobel (writing in the peer-reviewed, mainstream journal Icarus) found that hydrogen molecules are flowing (diffusing) down from the upper atmosphere to the surface, and disappearing there.

Chris McKay then made his statement responding to the new findings. He offered four possible hypotheses to account for the just-published results, and gave top place to the possibility that Strobel's results were simply mistaken.

He also wrote (as you've quoted): "This is a still a long way from 'evidence of life'."

But then the punch line: "However, it is extremely interesting."

[mutleyeng]

yes i was well aware it was the same Chris McKay that was the origin of the speculation.

I dont think anyone here would suggest that it isnt extremely interesting.
Its about how you present it. He does a pretty good job IMO

[Selfsim]

I have seen McKay admit in an interview that he has published ideas in papers that were subsequently found to be basically wrong.

That he openly states such, with no defence other than: 'in Astrobiology almost nothing can be ruled out or stated as correct', I find to be a sad indictment of Astrobiolgy in so far as being regarded as a science discipline.

Why should McKay be viewed as a credible source of anything scientific ?

[Colin Robinson]

I have seen McKay admit in an interview that he has published ideas in papers that were subsequently found to be basically wrong.

That he openly states such, with no defence other than: 'in Astrobiology almost nothing can be ruled out or stated as correct', I find to be a sad indictment of Astrobiolgy in so far as being regarded as a science discipline.

Why should McKay be viewed as a credible source of anything scientific ?

Is a good scientist someone whose hypotheses always turn out to be right?

Or is a good scientist someone who knows how to think through a hypothesis to the point where it leads to testable predictions, and then reconsider the hypothesis in the light of new data?

[Selfsim]

My point is that McKay seems to only ever offer hypotheses and opinions.

What makes his papers any different from any of the other gazillion scientists who, I might add, also have opinions and hypotheses, but keep them to themselves, (thus actively demonstrating scientific discipline) ?

Usually one is found to be 'wrong', where a view is exposed as being merely opinionated.

Is what he finds, 'extremely interesting', just another opinion, which may also turn out to be wrong, for the same reason ? I mean, by his own words, he doesn't seem to care much whether what he says is 'right' or 'wrong', so why say what he says, at all ?

Regards

[Colin Robinson]

My point is that McKay seems to only ever offer hypotheses and opinions.

What makes his papers any different from any of the other gazillion scientists who, I might add, also have opinions and hypotheses, but keep them to themselves, (thus actively demonstrating scientific discipline) ?

Usually one is found to be 'wrong', where a view is exposed as being merely opinionated.

Is what he finds, 'extremely interesting', just another opinion, which may also turn out to be wrong, for the same reason ? I mean, by his own words, he doesn't seem to care much whether what he says is 'right' or 'wrong', so why say what he says, at all ?

Why do mainstream scientific journals publish papers containing hypotheses?

Perhaps it is because they think formulating and testing of hypotheses is an integral part of science...

[Selfsim]

Why do mainstream scientific journals publish papers containing hypotheses?

Perhaps it is because they think formulating and testing of hypotheses is an integral part of science...

Well, there's a big difference between a hypothesis based mostly on someone's opinions, and one which has prior theoretical and/or some kind of constrained empirical basis behind it (eg: say, the Oort Cloud ... still formally a hypothesis it seems, and yet, almost no-one questions it anymore).

McKay states 'the theory' for astrobiology 'is hard'. (I'm not at all surprised to hear him say this). For example, as he says, no-one has yet developed life from scratch in the lab .. (there are lots of other examples). Whilst I'd be prepared to allow some leeway on this aspect, I question the 'need' for a 'theory' at all ! Where is the 'need' to explain something which has never been observed ? (Other than manipulating perceptions of priorities).

He says this is a case of 'follow the data' .. (which makes sense), but once again, the reason for doing this, continually points back to justifying the belief/opinion that life exists .. so: 'all we gotta do, is find it' ... which seems to be why the term 'evidence' is being used/confused .. ie: to justify the political stance .. the confusion seems premeditated and entirely deliberate, to me.

So what ?? .. one might say ... well, when such a stance/strategy is competing with other priorities, one cannot avoid calling it, for what it appears to be ... and it would seem to have little to do with any scientific approach, I can see.

Regards

[mutleyeng]

it looks to me like McKay is doing exactly what an astrobiologist should be doing within a space program.
NASA is about going places and looking whats there.
It isnt driven by science alone...never has been.