Never tell me the odds.

Odds are a funny thing.  If one takes the macro view that gee there are billions of stars out there then the odds must indicate life, intellegent or otherwise, it must exist even if we can't prove it because there are so many possibilities it must be so.

But the micro view tells a different story.  The odds of life developing on this world were really small, the odds that it managed to survive all the change and catastrophie of geologic time are even slimmer, and that an intellegent species has managed to arrive on the scene without blasting itself and everything else to bits in short order is even more amazing and it still remains a very, very strong possibility according to many scientists involved with setting the doomsday clock I might add.

In short, each and every planet has the very same slim odds of allowing life to arise and then survive.  Like a Vegas one armed bandit that paid off big time once, there is absolutely no guarantee that it will pay off again even if that handle is pulled, or that button pushed,  billions of times more because the odds remain the same every single time.

The history of life on our rather perfect little ball of rock is amazing in that it has managed through all the eons to hang on despite some 99% of all species having died out. How much harder then for marginal worlds or simply bad luck on others for it to survive let alone long enough to develop intellegence?

Odds are fun to play around with but they are essentially meaningless.  When it comes to life out there the metaphor of a glass half full or empty doesn't even come close to describing the situation. It should be more in the line of does that olympic sized swimming pool contain a single drop of water, or not.

L

   Could it be possible that the rare earth people are overstating the difficulty of life arising? Difficult as compared to what?!  What do we KNOW?

  While you point out that 99% of species are extinct as  evidence of just how tough it is, I see the fact that these species arose in the first place!  Life reinvented itself, in situ, over 4 billion + years.  Life is in fused in the rocks deep within the earth, on the ocean floors, in the polar wastes.  Life has engineered a multitude of mechanisms for survival, with the simplest and core lifeforms being the most resilient of all, and the seed organisms for more complex evolution.

  The rare earth arguments are certainly descriptions of our solar sytems and Earth's conditions, but the causal link is inferrred, not demonstrated, and certainly not repeated or empirically validated, no more than the arguments of plurality.

  For example:  Jupiter and our moon staved off destruction from asteroids and comets, etc.. ?? Oh yeah?  Jupiter assisted in the DEVELOPMENT of the asteroid belt that it then subsequently saved us from.  Without Jupiters interference, we might have another planet in this region--no asteroids,m and another "team player".  If the moon shielded us, it might just as well have destroyed us when Theia slammed into proto Earth.  Following that, asserting that the moon was some sort of miracle shield ignores the fact that many huge asteroids did impact--and life survived.  The moon certainly has drawn a % of incoming solar system objects.  This would be a minimum and safe description of its function.  "The moon saved Earth" is clearly an overstated interpretation of our continued prescence.  No on knows for sure.

  Recent indications are that complex molecules form in the interstellar medium, giving life a head start prior to planetary development.  Amino acids, hydrocarbons, and other materials of life are abundant and "waiting in the wings" in the very dusty regions where stars and solar systems form.  A planet may very well have thousands to many millions of start-up opportunities in the first few billions years  after initial formation to catch the life bug.  No one knows for sure.

  There is a difference between pulling numbers from the shadowed region and numbers drawn from a base of accumulating facts--exoplanets and current selection effects, interstellar spectroscopy, extremophiles, early solar system dynamics.... Implying that pluralists arguments are fantasy and rare Earth arguments are fact is severely skewing available evidence.  As a minimum, they both deserve to exist as reasonable positions, given the available knowledge of a vast, mysterious cosmos.

  The ratio of Earth-like planets capable of supporting life was stated at 100 billion.  If we put the number of intelligent species at 1,000, this is 100 million to 1.   These are slim odds indeed, yet the final number is not insubstantial.  Perhaps this is the "bad luck' rock bottom number you write of?  But it is not Zero.  

  All anyone with an interest (and we are few) can do is wait and observe the discovery process unfold.  The only appropriate "final analysis"  at this point is we do not know.  Speaking of odds is warranted, it would seem vs. "impossible".

cyberpatzer:

The rare earth arguments are certainly descriptions of our solar sytems and Earth's conditions, but the causal link is inferrred, not demonstrated, and certainly not repeated or empirically validated, no more than the arguments of plurality.

The fossil record shows a fairly solid time-line for the development of life on Earth, and the effects of tides and plate tectonics of the development of more complex life.  So there is solid evidence of those factors, not inferrence.  Other mechanisms like the shielding effect of the magnetosphere and the climate stabilizing effect of a large moon are also demonstrated and validated.  We also know that life as it has existed here could not have developed outside (or inside) of a very narrow (I believe it's from about .85AU to 1.15AU) habitable zone. 

The fact is we don't know what conditions are necessary for life to form.  We don't even know what it means to 'be alive'.  All we know is that on this one planet, under conditions we have not yet found anywhere else, life began and survived.  Of the millions of species which evolved here over time one developed what we call intelligence, and that species is far too young to yet be considered a success in biological terms.  Large numbers like 100 billion Earth-like planets, have no statistical relevence at all, even if they prove to be more than guesses, until we either begin to find other Earth-like planets (not super-earths, or others with qualified descriptions), or we find evidence of real life on other sorts of worlds.  Statistically speaking one data point that is significantly outside the data set must be considered an outlier (anomaly) until enough equally divergent data points are found.  So to use the vast numbers that are so easy to speculate about actually means nothing.

cyberpatzer:

... For example:  Jupiter and our moon staved off destruction from asteroids and comets, etc.. ?? Oh yeah?  Jupiter assisted in the DEVELOPMENT of the asteroid belt that it then subsequently saved us from.  Without Jupiters interference, we might have another planet in this region--no asteroids,m and another "team player". 

That's not the prevailing view, completely. You are correct that Jupiter's gravitational influence helped to create the Asteroid Belt. But in earlier epochs the Solar System was teeming with meteoroids, up to planetoid ane even planetary sizes, according to the model currently used by planetary scientists and meteoriticists. After something like one-half billion years, the rubble that permeated the Solar System was less widely distributed and much of it was headed fror the inner Solar System. There ensued a period of nearly a billion years of heavy bombardment (actually, there were two discrete periods of intense bombardment during this time). After that, most of the material had be incorporated into planets and satellites or flung from the system, or 'trapped' by gravitational resonances between Jupiter and Mars (and in a few other places), or moved outward and trapped in the Kuiper Belt and Oort Cloud along with comets that formed there.

There is even more to the story that we already surmise, and likely some we haven't figured out yet. But it's not as simple as Jupiter caused it and/or prevented it.

If the moon shielded us, it might just as well have destroyed us when Theia slammed into proto Earth.  Following that, asserting that the moon was some sort of miracle shield ignores the fact that many huge asteroids did impact--and life survived.  The moon certainly has drawn a % of incoming solar system objects.  This would be a minimum and safe description of its function.  "The moon saved Earth" is clearly an overstated interpretation of our continued prescence.  No on knows for sure.

Hmmm ... a simple look at the Moon with a telescope shows that at least some of the impactors that hit the Moon might otherwise have hit us. The currently accepted theory of the Moon's formation shows that just prior to the periods of heavy bombardment mentioned above a Mars-sized impactor struck Earth and glancing blow and the debris from that sideswipe eventually coalesced into the Moon. Granted, both before and after there have been many direct hits on the Earth. But it's hard to ignore the Moon's cratering as evidence that it has acted as a very effective shield. If you look at the the giant impact basins, it's pretty clear that a hit on the Moon by such bodies was much better for life here than a direct impact by the same bodies on Earth itself. Any one of those impactors would have created an extinction event had it hit the Earth. Many of them are several times the size of impactors thought to have contributed to extinction events on the Earth.

As to "who knows", who knows how many extinction events life can ultimately survive? If life on Earth survived a half-dozen, could it survive 20 more? ?Quien sabe? I'll warrant that a smaller number is better than a larger number, even though I can't establish a boundary condition ...

Jeff-

  Of course I recognize that the moon has been duly abused.  I just object to assigning it some absolute role in preserving life on earth.  And yes, fewer large impactors are probably better than many.  And yes, NO ONE can establish a boundary condition, which is a part of my point.

  I understand these things.  But again, they are simply descriptions of conditions on Earth, and shouldn't; be taken as the sole recipe for life.

    A planet would probably have to have a magnetosphere, and a suitable mass, as mMars demonstrates.  As far as stabilizing our wobble with the moon, could we imagine a planet that had much less of an axial precession, less of a tilt relative to the plane of orbit?  Would these things modify surface conditions?  Probably.  Could we imagine a planet of 1.5 Earth masses and thicker atmosphere, ameliorating variances in temperature DESPITE tilt/precession?  Probably.

  Earth does have plate tectonics and tides.  As far as I know, we don't have a patent on these things, and they could vary be degree on other worlds, to what end and in conjunction with other factors, we do not know.  The variables and potnentialities are dizzying.   Evolution in large measure depends on destruction and pinch-points to serve as a driver.   If we are focusing on the mere existence of life, we have to ask what would absolutely annihilate all living things on a planet.  On Earth, several large asteroids didn't do it.  Ice ages didn't do it.   Vulcanism didn;t do it.  Perhpas a gamma ray burster, a planet destroying collision (literally), or a solar anomaly.

  Much more likely in our experience is not annihilation but winnowings and reinvention.  And there is some evidence that even so-called catastrophic events, though they would destroy high life forms, wouldn't effect many extremophiles.  Life survives, of course, if one life form survives.   And while humanity is by no means a success, there are preconditons that have been met for a chance of success--self and contextual awareness and some capacity for reason.   We might be  able to imagine a species that emerges from another pinch-point that is better adapted for long-term survival.  We might imagine a species that developed elsewhere with a less aggressive, more pro-social, perhaps "hive" mentality.  And I don't minimize the surivial enhancement bestowed by culture, a tipping point phenomena, it appears.

   So, while "vast numbers" and statistical inference means nothing, perhaps we could back off attributing cosmic significance to local descriptions of one set of conditions that led to life, which is commensurate with another avenue to meaninglessness.  You argue that a sample of one should be considered an outlier, while statistical theory argues that the odds are that considering it a median or average would be more prudent.

   Leaving  your front door on a foggy morning and you stumble upon a rock.   Should you consider the rock an anomoly, or are more out there in the fog? 

cyberpatzer:

...  I just object to assigning it some absolute role in preserving life on earth.  ...

There is also the view that it might significantly have contributed to conditions being favorable for life to form here in the first place. If I remember the argument right, it was along the lines of the Moon's tidal influence on the oceans stirring shallow basins to create something like a "nursery" for microorganisms. I don't remember now where I read/saw/heard about this, but it likely was in one of the Universe programs in the Discovery Channel series ...

cyberpatzer:

   So, while "vast numbers" and statistical inference means nothing, perhaps we could back off attributing cosmic significance to local descriptions of one set of conditions that led to life, which is commensurate with another avenue to meaninglessness.  You argue that a sample of one should be considered an outlier, while statistical theory argues that the odds are that considering it a median or average would be more prudent.

I take your point (and generally agree), but words like nothing and meaningless are absolutes -- which is one of the things you're arguing against.

I do not think one can overstate the difficulty that life has undergone on this planet.  So far as we know, this is still the only planet that is anywhere near hospitable enough to harbor life.  Yes, I know there are those who hold out the possibility for Europa or Titan, or that even Mars had/has life but so far these are nothing more than guesses.  I have lived long enough to see many of these optimistic experts proven wholly wrong on their basic assumptions and hypothesis concerning other planets in our solar system.  Anyone remember the vast oceans and tropical climate of Venus that was projected just some forty years ago based on telescopic data and Venus' similarities to Earth?  How much more in the dark we are about planets orbiting other suns light years away let alone what may be going on there.  It is exciting though that we are progressing in our ability to reach out this far but being able to find life seems unlikely.

All we have to go on right now is the evidence we can see first hand on our own little world.  Perhaps in the next hundred years or so if we don't recede into barbarism or world wide disaster we might be able to answer some basic questions about the other worlds in our Solar System. 

cyberpatzer:

Leaving  your front door on a foggy morning and you stumble upon a rock.   Should you consider the rock an anomoly, or are more out there in the fog? 

It all depends on where on is walking.  If I stumbled on the rock while walking on the sidewalk it would indeed be an anomoly, if however I stumble on one because I live in a quarry then your anology would be apt. We are indeed walking in the fog and have no idea as of yet what environment we are walking in to make an accurate determination as to whether that proverbial rock is indeed rare or common.  I just hope that we do find that out before we discover that we have been playing in the street and the local bus happens along.

L

  Yeah, I was being a bit tongue-in-cheek.  I don't really think either sets of arguments mean nothing, but rather it is difficult to assign just exactly what they do mean, to what degree, etc...  I think taking what CAN ONLY be description and elevating it to prescription from a sample of one is highly suspect, as a minimum.

    At times I am prone to hyperbole (I am told...).

Will someone please ring the time out bell!

My point has never been to lobby for a zero chance of extraterrestrial life, but that with every varriable that we have identified as a contributing factor the potential number of like situations decreases.  Decreases, in my opinion, to a point where those conditions would be far more rare than an estimation of billions in our galaxy alone. 

I also agree that once life gets a foothold it is very difficult to eliminate, but it must first get that foothold, and even in our solar system where we know many of the conditions exist it has only happened once with any success at all.

Since those local conditions are the only ones we can study and really learn any thing from it's not appropriate to "back off" using them as a baseline.  If we did that we would have to ignore extreemophiles as examples of how robust life can be also since they are a local phenomena.

cyberpatzer:

Leaving  your front door on a foggy morning and you stumble upon a rock.   Should you consider the rock an anomoly, or are more out there in the fog? 

That would depend on what you've learned from your local area, wouldn't it?.

Cyberpatzer,

Although I know it is dangerous to do so, I will extrapolate from a sample of one (me), to say that I think the vast majority of skeptics on this issue actually hope that your point of view is the correct one.  I would assume that none of the participants in this thread have staked a scientific reputation on the Rare Earth hypothesis, and thus would be overjoyed to be proven wrong.

Also, if we were to actually fashion some sort of wager out of this, the correct position would be yours.  We'll never prove definitively that life doesn't exist elsewhere. 

I suppose there are mission planning and budgetary aspects that hinge partially on this debate, but it seems to me that those who want to look for life hold the upper hand at this point

cyberpatzer:

Will someone please ring the time out bell!

BRRRRRRRIIIIINGGGGG!  It's been a good discussion though .

Thanks for the bell.

 Yes, we've certainly covered the bases for the uninitiated, and maybe even forged ahead into new realm of imponderables...

  Beats thinking about my shrinking retirement account, overpriced house, and continued employment prospects....

  Until the next news clipping, Sith lord...

cyberpatzer:

Thanks for the bell.

 Yes, we've certainly covered the bases for the uninitiated, and maybe even forged ahead into new realm of imponderables...

  Beats thinking about my shrinking retirement account, overpriced house, and continued employment prospects....

  Until the next news clipping, Sith lord...

You know, if you and I can get through a thread amicably there might be hope for the economy yet . . .?

I've discovered there are FAR worse things in the world than disagreements over astronomy.

  And yes, you would think there would be a chance,

  but no, probability says we are toast!

  Of course, our assumptions on what constitutes "life" may be totally off. We should probably keep some of our own extreme forms of life in mind when feebly attempting to place odds. We've discovered bacteria living in conditions that a couple of decades ago would have been considered inhospitable. The only thing we seem to know for sure, is that when life appears it's a tenacious thing. Sure, %99 of all lifeforms on this planet may go extinct, but, something always seems to survive the extinction event.

 The odds on life forming that is intelligent enough to look up in the sky and wonder what's out there is probably quite rare. I think even IF there were other civilizations out there, the chance of "hearing" one with SETI or something would be remote at best.

 Personally, I think the attitude that there isn't any life out there is laughable. For one thing the odds are that it would exist elsewhere. The second reason is I think it's biased to making us feel special in th Universe.

kuzinov:

We've discovered bacteria living in conditions that a couple of decades ago would have been considered inhospitable. The only thing we seem to know for sure, is that when life appears it's a tenacious thing. Sure, %99 of all lifeforms on this planet may go extinct, but, something always seems to survive the extinction event.

Extreemophiles are often held up as evidence that life can exist on planets with much more extreem conditions than here.  The problem with that example is that extreemophile probably did not begin as extreemophiles, but rather, adapted to those niches opportunisticaly.  I agree, once life gets a foothold it has proven impossible, so far, to eradicate (like the grubs in my yard).  All indications are, however, that the conditions were very favorable when life actually began.  Duplicating those conditions will be more rare than just finding a wet, warm planet.

kuzinov:

Personally, I think the attitude that there isn't any life out there is laughable. For one thing the odds are that it would exist elsewhere. The second reason is I think it's biased to making us feel special in th Universe.

 No, we shouldn't. Cosmology at least has observable data, until we find something xenobiology isn't much of a science, but, a what if.

kuzinov:

 No, we shouldn't. Cosmology at least has observable data, until we find something xenobiology isn't much of a science, but, a what if.

That's my point exactly.  Too many people talk about the odds of life as if it is a foregone conclusion.