Chances of life existing elsewhere in the universe?

Floyd312 · 24th October 2007, 03:18 PM

The following quotes are from the "Aliens Knowing Of Human Life" thread in the Paranormal forum:

Originally Posted by Kilgore Trout

The universe is so huge, the chance seems pretty slim we're all there is.

Originally Posted by OldTigerCub

Considering the vastness of the universe, and the untold billions of potential solar systems in which there could be planets capable of sustaining life, it seems unlikely that we are the only intelligent life in the universe.

Originally Posted by Hindmost

Considering the size of the universe, I would suspect there has to be some life out there...but still no evidence.

I have often heard remarks such as these and, in fact, I have been known to say similar things myself. However, while reading that thread it occurred to me that I have always just assumed that the odds favored life existing elsewhere but I really have no actual quantifiable basis for thinking this way.

I do not know enough about current theories of the mechanisms of how life is thought to begin to know if there would even be any way to estimate the chances that the right chain of events would happen on a given planet to initiate life.

Is such a calculation even possible? And, if it is, would it then be possible to compare those numbers to our current estimates of the number of stars and planets in the universe and the current estimated age of the universe to see if it really is reasonable to assume that "the universe is so big that life must exist elsewhere"?

P.S. Although this is my first post, I have been lurking in the JREF forums for quite a while now. I just want to say that I am constantly amazed at the knowledge, insight, and humor of so many of the posters here.

Jimbo07 · 24th October 2007, 03:26 PM

You might be interested in starting with The Drake Equation. Personally, I find it a somewhat questionable exercise, but I suppose anything is better than nothing. It's not science per se, but it does make an interesting basis for speculation...

nimzov · 24th October 2007, 03:31 PM

The universe is huge but the probability of life appearing somewhere in that universe may be fantastically small. In that sense the size of the universe alone does not indicate that life must exist somewhere else. And we might be alone.

nimzo

Floyd312 · 24th October 2007, 03:34 PM

I also found the following comment fascinating. It is from a post in Nasa's "Astronomy Picture Of The Day" forums in a thread titled "NEWS" First earth size planet found.:

Quote:

There are so many factors controlling whether there is life outside out solar system. Are we the only ones? Is it common instead? Did it originate here or get transported here somehow? There are 10^22 stars or thereabouts and all the time in the universe, and yet is that enough? Could random chance make it happen if a new unique molecular combination were tried each nanosecond in each cubic angstrom of soup since the beginning of time? Odds are stacked against you if you accept that the minimum genome needs about 400,000 base-pair.

Still, life did happen at least once. Against the odds above. That strongly implies that what we believe we know about the model for the creation of life is not right in some fashion. If I live long enough, I may figure that one out. Then again, there are a very limited number of zeros in the life time left to me.

Is this statement accurate?

ETA: I mean the statement about the number of base-pairs for the minimum genome. Not his statement about whether the current model for the creation of life is right or not.

nimzov · 24th October 2007, 03:44 PM

January 9, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 1: Designs on Life"

http://realserver.princeton.edu:8080...9wardVN350K.rm

January 10, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 2: Designing a Habitable Solar System"

http://realserver.princeton.edu:8080...0wardVN350K.rm

January 11, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 3: The Construction of the Cosmos"

http://realserver.princeton.edu:8080...0wardVN350K.rm

nimzo

fuelair · 24th October 2007, 03:57 PM

Originally Posted by nimzov

January 9, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 1: Designs on Life"

http://realserver.princeton.edu:8080...9wardVN350K.rm

January 10, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 2: Designing a Habitable Solar System"

http://realserver.princeton.edu:8080...0wardVN350K.rm

January 11, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 3: The Construction of the Cosmos"

http://realserver.princeton.edu:8080...0wardVN350K.rm

nimzo

Thanks kindly for this info!! Well done!!!

tracer · 24th October 2007, 03:59 PM

Originally Posted by Floyd312

ETA: I mean the statement about the number of base-pairs for the minimum genome. Not his statement about whether the current model for the creation of life is right or not.

The simplest known self-replicating life form, Mycoplasma genitalium, has 580,070 nucleotide pairs in its DNA.

BenBurch · 24th October 2007, 05:07 PM

I'd say the universe is large enough that there is life out there somewhere.

But it might be in the next galaxy cluster over...

nimzov · 24th October 2007, 05:34 PM

Originally Posted by BenBurch

I'd say the universe is large enough that there is life out there somewhere.

But it might be in the next galaxy cluster over...

I see it this way.

There may be 10²⁰ stars in the universe. But if the probability of life is 10^-31 then life is still very unlikely.

We have a single instance so we do not know what the probability of life is.

nimzo

Floyd312 · 24th October 2007, 06:12 PM

Thanks everyone for the responses. And thank you nimzo for the links.

One of the reasons I asked the question is because it always seems to come up on occasions when friends or family are looking through my telescope. I usually gave the answer that with so many galaxies and stars there must be life elsewhere. Perhaps I will slightly revise my standard response to also include the alternative that the probability of life could be small enough to still be unlikely. And I think nimzo may have actually summed it up nicely with his response:

Quote:

We have a single instance so we do not know what the probability of life is.

OldTigerCub · 24th October 2007, 06:57 PM

Quote:

Is such a calculation even possible? And, if it is, would it then be possible to compare those numbers to our current estimates of the number of stars and planets in the universe and the current estimated age of the universe to see if it really is reasonable to assume that "the universe is so big that life must exist elsewhere"?

It seems unlikely that the chances of life elsewhere in the universe, namely intelligent lifeforms, and the quantity it might be found in, can be calculated mathematically until some point of reference is found (i.e.- some clear signs of any other life in the universe, it's distance from us, etc...).
Sadly, due to the laws of physics and the immense distances between us and potential life sustaining planets, it seems unlikely we will answer this question
in our lifetimes, but it is fun to speculate, and look at the stars, and wonder as you stare at the millions of points of light, "How could we possibly be the only ones here?"

BenBurch · 24th October 2007, 07:38 PM

Originally Posted by nimzov

I see it this way.

There may be 10²⁰ stars in the universe. But if the probability of life is 10^-31 then life is still very unlikely.

We have a single instance so we do not know what the probability of life is.

nimzo

Well, we do know that life formed on earth VERY quickly after there was a solid crust. I would argue that this means is isn't horribly unlikely given what had to be terrible conditions here at that time.

nimzov · 24th October 2007, 07:47 PM

Originally Posted by BenBurch

Well, we do know that life formed on earth VERY quickly after there was a solid crust. I would argue that this means is isn't horribly unlikely given what had to be terrible conditions here at that time.

Hi.

The fact that life appeared on earth does not mean that it was a likely event.

It could have been an extremely unlikely event... that simply happened given the conditions at that time.

nimzo

Thabiguy · 24th October 2007, 07:48 PM

Originally Posted by Floyd312

One of the reasons I asked the question is because it always seems to come up on occasions when friends or family are looking through my telescope. I usually gave the answer that with so many galaxies and stars there must be life elsewhere.

Or perhaps life might be so common as to be almost unremarkable. Note that it is a plausible, scientifically investigated possibility that life exists or has existed on other bodies of our solar system - most notably Mars and Europa. If microscopic life is found on Mars tomorrow, it would certainly be an extremely exciting discovery - but you can't honestly say that it would be surprising, could you? It would be quite consistent with what we know so far, perhaps even to the point that some might say it was more or less expected. And I think there's a good chance that we may find out, one way or another, in our lifetime.

Now if we are seriously considering the possibility that life might have appeared at multiple places even in our very solar system, then given all we know about extra-solar planetary systems, by logical extension we are at the same time seriously considering the possibility that with so many galaxies and stars there must be life pretty much everywhere you look in the night sky.

(Primitive, microscopic life, that is. Advanced, multi-cellular life forms are a different story altogether and could arguably be very rare even if life itself was ubiquitous.)

nimzov · 24th October 2007, 07:57 PM

Originally Posted by Thabiguy

Now if we are seriously considering the possibility that life might have appeared at multiple places even in our very solar system, then given all we know about extra-solar planetary systems, by logical extension we are at the same time seriously considering the possibility that with so many galaxies and stars there must be life pretty much everywhere you look in the night sky.

If we find life in the solar system but if this life is the result of contamination from another planet or body it tells us absolutely nothing about the possibility of life outside the solar system.

But if the new life found is not the result of contamination, then I agree it is a totally different story, And it might increase the chance for life outside our solar system.

I think this is what Peter Ward explains in his second lecture, if I understood him correctly.

nimzo

BenBurch · 24th October 2007, 08:09 PM

Originally Posted by nimzov

Hi.

The fact that life appeared on earth does not mean that it was a likely event.

It could have been an extremely unlikely event... that simply happened given the conditions at that time.

nimzo

I disagree.

That it appears SO quickly after conditions allowed it strongly suggests that it is either a likely consequence of liquid water and hydrocarbons or that it was panspermia.

No, its not proof, but is very suggestive and makes a low probability unlikely.

Irony · 25th October 2007, 08:29 AM

Originally Posted by tracer

The simplest known self-replicating life form, Mycoplasma genitalium, has 580,070 nucleotide pairs in its DNA.

Yes, but Mycoplams genitalium has that many nucleotide pairs after billions of years of evolution. The earliest crude replicators were probably just simple self-replicating proteins and not nearly as complex as modern cellular organisms.

FireGarden · 25th October 2007, 09:04 AM

Quote:

The earliest crude replicators were probably just simple self-replicating proteins

RNA is put forward as a possible first:
http://www.geocities.com/capecanaver...948/orgel.html

Quote:

Anyone trying to solve this puzzle immediately encounters a paradox. Nowadays nucleic acids are synthesized only with the help of proteins, and proteins are synthesized only if their corresponding nucleotide sequence is present. It is extremely improbable that proteins and nucleic acids, both of which are structurally complex, arose spontaneously in the same place at the same time. Yet it also seems impossible to have one without the other. And so, at first glance, one might have to conclude that life could never, in fact, have originated by chemical means.

In the late 1960s Carl R. Woese of the University of Illinois, Francis Crick, then at the Medical Research Council in England, and I (working at the Salk Institute for Biological Studies in San Diego) independently suggested a way out of this difficulty. We proposed that RNA might well have come first and established what is now called the RNA world - a world in which RNA catalyzed all the reactions necessary for a precursor of life's last common ancestor to survive and replicate. We also posited that RNA could subsequently have developed the ability to link amino acids together into proteins. This scenario could have occurred, we noted, if prebiotic RNA had two properties not evident today: a capacity to replicate without the help of proteins and an ability to catalyze every step of protein synthesis.

uruk · 25th October 2007, 09:12 AM

Originally Posted by nimzov

Hi.

The fact that life appeared on earth does not mean that it was a likely event.

It could have been an extremely unlikely event... that simply happened given the conditions at that time.

nimzo

What would make you think that the formation of life is an unlikely event? We've been only been able to explore this little section of our universe.

Well given the shear number of stars and planets out there I'd say there is a pretty good probablity that conditions that exist here can exist elsewhere.

Since it happend here there is nothing to say that it can't happen elsewhere given that there are similar conditions elsewhere.

alfaniner · 25th October 2007, 09:34 AM

Well, the Universe is pretty big. If there is no other life out there, it would be an awful waste of space! (Contact - Carl Sagan)

Either we are utterly alone in the Universe, or we are not. In either case, I find the prospect quite staggering. (Arthur C. Clarke?)

Paraphrased from memory. My Google-fu does not find the exact quotes.

nimzov · 25th October 2007, 09:38 AM

Originally Posted by uruk

What would make you think that the formation of life is an unlikely event? We've been only been able to explore this little section of our universe.

I am not saying it is. I am saying that we cannot evaluate the probability of an event from a single instance of such an event.

nimzo

uruk · 25th October 2007, 03:03 PM

Originally Posted by nimzov

I am not saying it is. I am saying that we cannot evaluate the probability of an event from a single instance of such an event.

nimzo

But the fact that it happened here means that there is nothing to prevent it from happening elsewhere given that the conditions here can exist elsewhere. And the fact that those conditions exists here means that there is nothing to prevent these conditions from existing elsewhere given the vast number of oppurtunities or probabilities for these conditions to exist.

Whew! Can somebody check to see if my statement is circular?

If you role a billion dice and they all come up sixes once, chances are pretty good that they will all roll up sixes again if you roll them long enough seeing as the possibility is there for them to roll up all sixes in the first place.
Though, I could be making the gambler's fallacy in this instance.

nimzov · 25th October 2007, 03:24 PM

Originally Posted by uruk

If you role a billion dice and they all come up sixes once, chances are pretty good that they will all roll up sixes again if you roll them long enough seeing as the possibility is there for them to roll up all sixes in the first place.
Though, I could be making the gambler's fallacy in this instance.

To stay with you dice analogy. I think the problem is that we do not know how many faces the dice has. The more faces, the less likely it will happen again.

nimzo

Complexity · 25th October 2007, 03:26 PM

Greater than 0 (sorry, fundies), less than 1 (sorry, abductees).

Jimbo07 · 25th October 2007, 03:29 PM

Originally Posted by Complexity

Greater than 0 (sorry, fundies), less than 1 (sorry, abductees).

I'm not a fundy. I'm not even religious. It may still be 0. We may be the only ones even without FSM having anything to say about it...

BenBurch · 25th October 2007, 03:57 PM

The dice analogy is not apt. More apt is that we understand that the dice HAS faces, and have set some upper and lower bounds on the number of these faces, representing our understanding of cosmology, nucleosynthesis, organic chemistry, and biology that allows us to establish these parameters.

JJM · 25th October 2007, 05:26 PM

Originally Posted by nimzov

January 9, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 1: Designs on Life"

http://realserver.princeton.edu:8080...9wardVN350K.rm

{snip}

I cannot get audio on my computer. However, I am well-aware of Ward's nonsense, often published along with an equally confused fellow named Brownlee, and their Young Earth Creationist friend Gonzalez. The latter likes these ideas because he can tell his congregation that science proves we are god's unique creation.

They begin with the the ideas that life can only exist within a certain distance of a Sun-like star in a certain region of a Milky Way-like galaxy. Then they assign life-promoting reasons for Solar system features, such as Saturn and our Moon. They have quite a list of requirements, and they proceed to calculate a small probability for all these features to come together to allow "life" elsewhere.

What is wrong? They are drawing a line through the single data point they have on "life" (us) and extrapolating to the dimensions of the Universe. They have no idea how life could adapt to other situations, or how other system features could replace Jupiter or the Moon.

When Ward talks about finding "life," he is talking about finding other Earth-like planets in Solar-like stellar systems, nothing more. His ideas that life is extremely rare are baseless, and can be safely discarded.

In other news, Ward and Brownlee wrote a book after finding a computer program that would extrapolate plate tectonics for hundreds of millions of years into the future. Using that, they learned that the continents are headed for a configuration that would give rise to an uninhabitable Earth at some time. Do you see how easy it is to use extrapolation, and a fevered imagination, to come up with a just-so story?

I don't know if Ward does anything useful in science; but his popular writings are junk.

uruk · 25th October 2007, 05:33 PM

Originally Posted by nimzov

To stay with you dice analogy. I think the problem is that we do not know how many faces the dice has. The more faces, the less likely it will happen again.

nimzo

Good point.
I just think that since it happened here there's no reason to believe that it could not happen elsewhere.

And if the mechinisims to create life exists in the first place well then.......

uruk · 25th October 2007, 05:42 PM

Originally Posted by BenBurch

The dice analogy is not apt. More apt is that we understand that the dice HAS faces, and have set some upper and lower bounds on the number of these faces, representing our understanding of cosmology, nucleosynthesis, organic chemistry, and biology that allows us to establish these parameters.

There is some evidence to support that life can exists (even in a dormant state) in conditions that are very harsh.

Earth bacteria remained viable even after spending several years in the environment on the moon.
See Apollo 12 and the surveyor camera that was returned to Earth.
Doesn't that open up the possibilites any?

Whack01 · 25th October 2007, 05:48 PM

Originally Posted by Complexity

Greater than 0 (sorry, fundies), less than 1 (sorry, abductees).

Why does fundamentalism imply that life cannot exist elsewhere in the universe? Doesn't it merely imply that life would have had to be created elsewhere in the universe as opposed to evolving?

ETA: I'm not interested in debating the merits/demerits of the position, just what it actually is.

Jimbo07 · 25th October 2007, 08:33 PM

Originally Posted by Whack01

Why does fundamentalism imply that life cannot exist elsewhere in the universe? Doesn't it merely imply that life would have had to be created elsewhere in the universe as opposed to evolving?

ETA: I'm not interested in debating the merits/demerits of the position, just what it actually is.

I think it has more to do with Biblical literalism and the garden on Earth and being created in the FSM's image, etc.

Again, though, if it were fact that we were the only ones... it would be a quite independent piece of information from that of Ed's influence.

Badger · 25th October 2007, 08:55 PM

I remember reading about clay being involved in the development of replicating molecules. A quick google search supplies:

http://www.origins.rpi.edu/claycatalyzed.html

and

http://www.springerlink.com/content/p8w6w63012773566/

My personal opinion is that the existence of self-replicating molecules elsewhere in the universe holds high probability, as the basic chemical reactions and interactions would be pretty common.

What they turn into after they start self-replicating....well, who knows.

Corsair 115 · 25th October 2007, 09:28 PM

Originally Posted by JJM

They begin with the the ideas that life can only exist within a certain distance of a Sun-like star in a certain region of a Milky Way-like galaxy. Then they assign life-promoting reasons for Solar system features, such as Saturn and our Moon. They have quite a list of requirements, and they proceed to calculate a small probability for all these features to come together to allow "life" elsewhere.

That was the case laid out in Brownlee's and Ward's book Rare Earth: Why Complex Life is Uncommon in the Universe.

As someone who has purchased the book some years ago and read it, I would say your criticisms are way off base.

First off, their conclusion is that bacterial life is most likely very widespread in the universe, but complex life (e.g. animals, humans) is likely very rare. The reason: bacterial life is simple, can exist in a vast variety of environments (many of which would be fatal to complex lifeforms), and can survive environmental changes which would eliminate more complex organisms. Complex life, on the other hand, tends to need much narrower ranges of environments in which to survive, and is much more susceptible to changes in the environment which can kill it off.

The case they lay out in their book is well supported by the studies and works of a great many other scientists. The reference section of the book is 26 pages long, and lists quite specifically all the other works they reference in their book.

I found the case the book makes to be compelling, well constructed, and well supported. I would recommend it to anyone interested in the subject matter.

You are free to try and refute the claims made in it by either demonstrating the references they use are inaccurate or by pointing to material which directly disproves the material they use to support their thesis.

Originally Posted by JJM

What is wrong? They are drawing a line through the single data point they have on "life" (us) and extrapolating to the dimensions of the Universe.

Depends on how you define data point, doesn't it? Is life on Earth a single data point or millions? After all, a human being is not a crab which is not a maple tree which is not a bacteria.

Originally Posted by JJM

His ideas that life is extremely rare are baseless, and can be safely discarded.

See first reply. In the aforementioned book, the case is quite clearly that bacterial life is likely very widespread but complex life is likely very rare.

Originally Posted by JJM

In other news, Ward and Brownlee wrote a book after finding a computer program that would extrapolate plate tectonics for hundreds of millions of years into the future. Using that, they learned that the continents are headed for a configuration that would give rise to an uninhabitable Earth at some time.

I saw that book in the bookstore but not happen to purchase it. My recollection, from having thumbed through it, was that their contention was that in the very long-term Earth would have too little carbon in the atmosphere and thus would become too cold for life. I didn't thumb through enough of it to see or recall the plate tectonics part you to which you are alluding.

JJM · 26th October 2007, 02:22 AM

Originally Posted by Corsair 115

That was the case laid out in Brownlee's and Ward's book Rare Earth: Why Complex Life is Uncommon in the Universe.

As someone who has purchased the book some years ago and read it, I would say your criticisms are way off base. {snip}

I found the case the book makes to be compelling, well constructed, and well supported. I would recommend it to anyone interested in the subject matter.

I don't have the book at hand. Can you look and tell me how many stellar systems they examined, and how many had "life" however they define it? I am pretty sure the answer to both questions is one, and everything else is pure speculation. Theirs is an interesting notion, and seems well-written for the lay audience; such that a lot of people found it compelling. Nonetheless, it is science fiction.

Originally Posted by Corsair 115

{snip}

SomeGuy · 26th October 2007, 02:52 AM

Originally Posted by Jimbo07

I'm not a fundy. I'm not even religious. It may still be 0. We may be the only ones even without FSM having anything to say about it...

You are wrong, the number of other life forms in the universe can be 0, but we're discussing the chance that other life forms exists.

The chance is necessarily non-zero, because we know that life can come into existence given the right circumstances, else we wouldn't be discussing this.

So he is completely right that the chance (untill we've fully explored the universe) is non-zero. Note that the provisional chance that there are other life forms in this universe will go down if we discover more and more planets without life forms on them.

cloudshipsrule · 26th October 2007, 05:27 AM

Even if there is a chance that other life forms exist 'out there', the chance that they are at the same spot on the evolutionary line as humans is even more remote.

Life elsewhere could easily be plus or minus a billion years from where we are evolution-wise. That could mean extremely intelligent mega-beings, or it could mean a minute organism with no brain.

SomeGuy · 26th October 2007, 05:31 AM

Originally Posted by cloudshipsrule

Even if there is a chance that other life forms exist 'out there', the chance that they are at the same spot on the evolutionary line as humans is even more remote.

Life elsewhere could easily be plus or minus a billion years from where we are evolution-wise. That could mean extremely intelligent mega-beings, or it could mean a minute organism with no brain.

Eventhough I agree with the general idea of your post, it does seem to assume a rather oversimplified linear progressive type of evolution.

Jimbo07 · 26th October 2007, 06:54 AM

Originally Posted by Corsair 115

Depends on how you define data point, doesn't it? Is life on Earth a single data point or millions? After all, a human being is not a crab which is not a maple tree which is not a bacteria.

I think the planet is treated as the data point, since we have yet to find conclusive evidence of multicellular life on any other planetary body. Were we to find even one conclusive example of an independently evolved multi-cellular organism on Mars, say, the entire nature of this speculative exercise would be radically altered. I believe that is why the expensive search continues, in spite of a so-far null result.

Originally Posted by SomeGuy

You are wrong, the number of other life forms in the universe can be 0, but we're discussing the chance that other life forms exists.

Ooh! Fair play. You're right that I can't prove a universal negative (although I did use "may"). The chance, while demonstrably not zero, may still be inifinitessimally small, as far as we know.

Quote:

The chance is necessarily non-zero, because we know that life can come into existence given the right circumstances, else we wouldn't be discussing this.

Actually, we do not yet know whether the conditions for life on Earth are unique. There may be good reasons to suspect not, but with no other data, we just don't know.

Quote:

So he is completely right that the chance (untill we've fully explored the universe) is non-zero. Note that the provisional chance that there are other life forms in this universe will go down if we discover more and more planets without life forms on them.

Agreed... the only thing we're safe in concluding is that our local neighbourhood is not filthy with extraterrestrial lifeforms phoning in to 97.7MHz on your FM dial, the station that ROCKS! ROCKS! ROCKS! with more daily prizes than those other guys...

JoeTheJuggler · 26th October 2007, 08:43 AM

To the question put by the OP, the only argument that ET life is probable (in our current state of ignorance of any ET life) is that the history of theories based on our occupying a central or unique place in the universe have pretty much all proven wrong.

However, we still have no evidence to say that ET life is probable.

For the question of intelligent life, using our sample of one and the huge distances between things in the universe, AND the fact that we've only had a radio technology for less than 100 years in the 4.5 billion year history of our life, I'd say the Drake Equation for scoring a SETI hit in our lifetimes (or the lifetime of our civilization) is nearly zero.

Though I'd love to be wrong about that.

From Carl Sagan:

Quote:

I'm often asked the question, "Do you think there is extraterrestrial intelligence?" I give the standard arguments--there are a lot of places out there, and use the word billions, and so on. And then I say it would be astonishing to me if there weren't extraterrestrial intelligence, but of course there is as yet no compelling evidence for it. And then I'm asked, "Yeah, but what do you really think?" I say, "I just told you what I really think." "Yeah, but what's your gut feeling?" But I try not to think with my gut. Really, it's okay to reserve judgment until the evidence is in.

From the introduction to The Outer Edge: Classic Investigations of the Paranormal edited by Joe Nickell, Barry Karr and Tom Genoni.

bokonon · 26th October 2007, 09:58 AM

Originally Posted by uruk

There is some evidence to support that life can exists (even in a dormant state) in conditions that are very harsh.

Earth bacteria remained viable even after spending several years in the environment on the moon.
See Apollo 12 and the surveyor camera that was returned to Earth.
Doesn't that open up the possibilites any?

It opens up the possibility that bacteria can survive interstellar journeys in a dormant state to "seed" life elsewhere if conditions are right. I doubt that a "dormant bacteria" can be created from chemical soup under conditions which would not favor the creation of a non-dormant specimen.

24th October 2007, 03:18 PM	#1
Floyd312 Student Join Date: Aug 2007 Posts: 25	Chances of life existing elsewhere in the universe? The following quotes are from the "Aliens Knowing Of Human Life" thread in the Paranormal forum: Originally Posted by Kilgore Trout The universe is so huge, the chance seems pretty slim we're all there is. Originally Posted by OldTigerCub Considering the vastness of the universe, and the untold billions of potential solar systems in which there could be planets capable of sustaining life, it seems unlikely that we are the only intelligent life in the universe. Originally Posted by Hindmost Considering the size of the universe, I would suspect there has to be some life out there...but still no evidence. I have often heard remarks such as these and, in fact, I have been known to say similar things myself. However, while reading that thread it occurred to me that I have always just assumed that the odds favored life existing elsewhere but I really have no actual quantifiable basis for thinking this way. I do not know enough about current theories of the mechanisms of how life is thought to begin to know if there would even be any way to estimate the chances that the right chain of events would happen on a given planet to initiate life. Is such a calculation even possible? And, if it is, would it then be possible to compare those numbers to our current estimates of the number of stars and planets in the universe and the current estimated age of the universe to see if it really is reasonable to assume that "the universe is so big that life must exist elsewhere"? P.S. Although this is my first post, I have been lurking in the JREF forums for quite a while now. I just want to say that I am constantly amazed at the knowledge, insight, and humor of so many of the posters here.
Floyd312 Student Join Date: Aug 2007 Posts: 25

24th October 2007, 03:26 PM	#2
Jimbo07 Illuminator Join Date: Jan 2006 Posts: 3,417	You might be interested in starting with The Drake Equation. Personally, I find it a somewhat questionable exercise, but I suppose anything is better than nothing. It's not science per se, but it does make an interesting basis for speculation...
Jimbo07 Illuminator Join Date: Jan 2006 Posts: 3,417	__________________ This post approved by your local jPac (Jimbo07 Political Action Committee), also registered with Jimbo07 as the Jimbo07 Equality Rights Knowledge Betterment Action Group. Atoms in supernova explosion get huge business -- Pixie of key

24th October 2007, 03:31 PM	#3
nimzov Muse Join Date: Apr 2004 Location: Montréal Posts: 917	The universe is huge but the probability of life appearing somewhere in that universe may be fantastically small. In that sense the size of the universe alone does not indicate that life must exist somewhere else. And we might be alone. nimzo
	Last edited by nimzov; 24th October 2007 at 03:42 PM.

24th October 2007, 03:34 PM	#4
Floyd312 Student Join Date: Aug 2007 Posts: 25	I also found the following comment fascinating. It is from a post in Nasa's "Astronomy Picture Of The Day" forums in a thread titled "NEWS" First earth size planet found.: Quote: There are so many factors controlling whether there is life outside out solar system. Are we the only ones? Is it common instead? Did it originate here or get transported here somehow? There are 10^22 stars or thereabouts and all the time in the universe, and yet is that enough? Could random chance make it happen if a new unique molecular combination were tried each nanosecond in each cubic angstrom of soup since the beginning of time? Odds are stacked against you if you accept that the minimum genome needs about 400,000 base-pair. Still, life did happen at least once. Against the odds above. That strongly implies that what we believe we know about the model for the creation of life is not right in some fashion. If I live long enough, I may figure that one out. Then again, there are a very limited number of zeros in the life time left to me. Is this statement accurate? ETA: I mean the statement about the number of base-pairs for the minimum genome. Not his statement about whether the current model for the creation of life is right or not.
Floyd312 Student Join Date: Aug 2007 Posts: 25	Last edited by Floyd312; 24th October 2007 at 03:39 PM.

24th October 2007, 03:57 PM	#6
fuelair Cythraul Enfys Join Date: May 2006 Posts: 28,936	Originally Posted by nimzov January 9, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 1: Designs on Life" http://realserver.princeton.edu:8080...9wardVN350K.rm January 10, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 2: Designing a Habitable Solar System" http://realserver.princeton.edu:8080...0wardVN350K.rm January 11, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 3: The Construction of the Cosmos" http://realserver.princeton.edu:8080...0wardVN350K.rm nimzo Thanks kindly for this info!! Well done!!!
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24th October 2007, 03:44 PM	#5
nimzov Muse Join Date: Apr 2004 Location: Montréal Posts: 917	January 9, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 1: Designs on Life" http://realserver.princeton.edu:8080...9wardVN350K.rm January 10, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 2: Designing a Habitable Solar System" http://realserver.princeton.edu:8080...0wardVN350K.rm January 11, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 3: The Construction of the Cosmos" http://realserver.princeton.edu:8080...0wardVN350K.rm nimzo

24th October 2007, 03:59 PM	#7
tracer Graduate Poster Join Date: Jul 2003 Location: Silicon Valley, Calif. Posts: 1,356	Originally Posted by Floyd312 ETA: I mean the statement about the number of base-pairs for the minimum genome. Not his statement about whether the current model for the creation of life is right or not. The simplest known self-replicating life form, Mycoplasma genitalium, has 580,070 nucleotide pairs in its DNA.

24th October 2007, 05:07 PM	#8
BenBurch Gatekeeper of The Left Join Date: Sep 2007 Location: The Universe 35.2 ms ahead of this one. Posts: 32,150	I'd say the universe is large enough that there is life out there somewhere. But it might be in the next galaxy cluster over...
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24th October 2007, 05:34 PM	#9
nimzov Muse Join Date: Apr 2004 Location: Montréal Posts: 917	Originally Posted by BenBurch I'd say the universe is large enough that there is life out there somewhere. But it might be in the next galaxy cluster over... I see it this way. There may be 10²⁰ stars in the universe. But if the probability of life is 10^-31 then life is still very unlikely. We have a single instance so we do not know what the probability of life is. nimzo

24th October 2007, 06:12 PM	#10
Floyd312 Student Join Date: Aug 2007 Posts: 25	Thanks everyone for the responses. And thank you nimzo for the links. One of the reasons I asked the question is because it always seems to come up on occasions when friends or family are looking through my telescope. I usually gave the answer that with so many galaxies and stars there must be life elsewhere. Perhaps I will slightly revise my standard response to also include the alternative that the probability of life could be small enough to still be unlikely. And I think nimzo may have actually summed it up nicely with his response: Quote: We have a single instance so we do not know what the probability of life is.
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24th October 2007, 06:57 PM	#11
OldTigerCub Striped Shapeshifting Reptoid Join Date: Sep 2007 Location: Steeler Nation, Pa. Posts: 1,633	Quote: Is such a calculation even possible? And, if it is, would it then be possible to compare those numbers to our current estimates of the number of stars and planets in the universe and the current estimated age of the universe to see if it really is reasonable to assume that "the universe is so big that life must exist elsewhere"? It seems unlikely that the chances of life elsewhere in the universe, namely intelligent lifeforms, and the quantity it might be found in, can be calculated mathematically until some point of reference is found (i.e.- some clear signs of any other life in the universe, it's distance from us, etc...). Sadly, due to the laws of physics and the immense distances between us and potential life sustaining planets, it seems unlikely we will answer this question in our lifetimes, but it is fun to speculate, and look at the stars, and wonder as you stare at the millions of points of light, "How could we possibly be the only ones here?"
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24th October 2007, 07:38 PM	#12
BenBurch Gatekeeper of The Left Join Date: Sep 2007 Location: The Universe 35.2 ms ahead of this one. Posts: 32,150	Originally Posted by nimzov I see it this way. There may be 10²⁰ stars in the universe. But if the probability of life is 10^-31 then life is still very unlikely. We have a single instance so we do not know what the probability of life is. nimzo Well, we do know that life formed on earth VERY quickly after there was a solid crust. I would argue that this means is isn't horribly unlikely given what had to be terrible conditions here at that time.
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24th October 2007, 07:47 PM	#13
nimzov Muse Join Date: Apr 2004 Location: Montréal Posts: 917	Originally Posted by BenBurch Well, we do know that life formed on earth VERY quickly after there was a solid crust. I would argue that this means is isn't horribly unlikely given what had to be terrible conditions here at that time. Hi. The fact that life appeared on earth does not mean that it was a likely event. It could have been an extremely unlikely event... that simply happened given the conditions at that time. nimzo

24th October 2007, 07:48 PM	#14
Thabiguy Muse Join Date: Feb 2007 Posts: 783	Originally Posted by Floyd312 One of the reasons I asked the question is because it always seems to come up on occasions when friends or family are looking through my telescope. I usually gave the answer that with so many galaxies and stars there must be life elsewhere. Or perhaps life might be so common as to be almost unremarkable. Note that it is a plausible, scientifically investigated possibility that life exists or has existed on other bodies of our solar system - most notably Mars and Europa. If microscopic life is found on Mars tomorrow, it would certainly be an extremely exciting discovery - but you can't honestly say that it would be surprising, could you? It would be quite consistent with what we know so far, perhaps even to the point that some might say it was more or less expected. And I think there's a good chance that we may find out, one way or another, in our lifetime. Now if we are seriously considering the possibility that life might have appeared at multiple places even in our very solar system, then given all we know about extra-solar planetary systems, by logical extension we are at the same time seriously considering the possibility that with so many galaxies and stars there must be life pretty much everywhere you look in the night sky. (Primitive, microscopic life, that is. Advanced, multi-cellular life forms are a different story altogether and could arguably be very rare even if life itself was ubiquitous.)
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24th October 2007, 07:57 PM	#15
nimzov Muse Join Date: Apr 2004 Location: Montréal Posts: 917	Originally Posted by Thabiguy Now if we are seriously considering the possibility that life might have appeared at multiple places even in our very solar system, then given all we know about extra-solar planetary systems, by logical extension we are at the same time seriously considering the possibility that with so many galaxies and stars there must be life pretty much everywhere you look in the night sky. If we find life in the solar system but if this life is the result of contamination from another planet or body it tells us absolutely nothing about the possibility of life outside the solar system. But if the new life found is not the result of contamination, then I agree it is a totally different story, And it might increase the chance for life outside our solar system. I think this is what Peter Ward explains in his second lecture, if I understood him correctly. nimzo

24th October 2007, 08:09 PM	#16
BenBurch Gatekeeper of The Left Join Date: Sep 2007 Location: The Universe 35.2 ms ahead of this one. Posts: 32,150	Originally Posted by nimzov Hi. The fact that life appeared on earth does not mean that it was a likely event. It could have been an extremely unlikely event... that simply happened given the conditions at that time. nimzo I disagree. That it appears SO quickly after conditions allowed it strongly suggests that it is either a likely consequence of liquid water and hydrocarbons or that it was panspermia. No, its not proof, but is very suggestive and makes a low probability unlikely.
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25th October 2007, 08:29 AM	#17
Irony Muse Join Date: Jan 2007 Posts: 872	Originally Posted by tracer The simplest known self-replicating life form, Mycoplasma genitalium, has 580,070 nucleotide pairs in its DNA. Yes, but Mycoplams genitalium has that many nucleotide pairs after billions of years of evolution. The earliest crude replicators were probably just simple self-replicating proteins and not nearly as complex as modern cellular organisms.
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25th October 2007, 09:04 AM	#18
FireGarden Philosopher Join Date: Aug 2002 Location: Spannungsbogen -- without a visa Posts: 5,043	Quote: The earliest crude replicators were probably just simple self-replicating proteins RNA is put forward as a possible first: http://www.geocities.com/capecanaver...948/orgel.html Quote: Anyone trying to solve this puzzle immediately encounters a paradox. Nowadays nucleic acids are synthesized only with the help of proteins, and proteins are synthesized only if their corresponding nucleotide sequence is present. It is extremely improbable that proteins and nucleic acids, both of which are structurally complex, arose spontaneously in the same place at the same time. Yet it also seems impossible to have one without the other. And so, at first glance, one might have to conclude that life could never, in fact, have originated by chemical means. In the late 1960s Carl R. Woese of the University of Illinois, Francis Crick, then at the Medical Research Council in England, and I (working at the Salk Institute for Biological Studies in San Diego) independently suggested a way out of this difficulty. We proposed that RNA might well have come first and established what is now called the RNA world - a world in which RNA catalyzed all the reactions necessary for a precursor of life's last common ancestor to survive and replicate. We also posited that RNA could subsequently have developed the ability to link amino acids together into proteins. This scenario could have occurred, we noted, if prebiotic RNA had two properties not evident today: a capacity to replicate without the help of proteins and an ability to catalyze every step of protein synthesis.
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25th October 2007, 09:12 AM	#19
uruk Philosopher Join Date: Apr 2003 Location: In the land of the Shatner stealing Mexico touchers Posts: 5,313	Originally Posted by nimzov Hi. The fact that life appeared on earth does not mean that it was a likely event. It could have been an extremely unlikely event... that simply happened given the conditions at that time. nimzo What would make you think that the formation of life is an unlikely event? We've been only been able to explore this little section of our universe. Well given the shear number of stars and planets out there I'd say there is a pretty good probablity that conditions that exist here can exist elsewhere. Since it happend here there is nothing to say that it can't happen elsewhere given that there are similar conditions elsewhere.
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25th October 2007, 09:34 AM	#20
alfaniner Penultimate Amazing Join Date: Aug 2001 Location: Sorth Dakonsin Posts: 11,385	Well, the Universe is pretty big. If there is no other life out there, it would be an awful waste of space! (Contact - Carl Sagan) Either we are utterly alone in the Universe, or we are not. In either case, I find the prospect quite staggering. (Arthur C. Clarke?) Paraphrased from memory. My Google-fu does not find the exact quotes.

25th October 2007, 09:38 AM	#21
nimzov Muse Join Date: Apr 2004 Location: Montréal Posts: 917	Originally Posted by uruk What would make you think that the formation of life is an unlikely event? We've been only been able to explore this little section of our universe. I am not saying it is. I am saying that we cannot evaluate the probability of an event from a single instance of such an event. nimzo

25th October 2007, 03:03 PM	#22
uruk Philosopher Join Date: Apr 2003 Location: In the land of the Shatner stealing Mexico touchers Posts: 5,313	Originally Posted by nimzov I am not saying it is. I am saying that we cannot evaluate the probability of an event from a single instance of such an event. nimzo But the fact that it happened here means that there is nothing to prevent it from happening elsewhere given that the conditions here can exist elsewhere. And the fact that those conditions exists here means that there is nothing to prevent these conditions from existing elsewhere given the vast number of oppurtunities or probabilities for these conditions to exist. Whew! Can somebody check to see if my statement is circular? If you role a billion dice and they all come up sixes once, chances are pretty good that they will all roll up sixes again if you roll them long enough seeing as the possibility is there for them to roll up all sixes in the first place. Though, I could be making the gambler's fallacy in this instance.
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25th October 2007, 03:24 PM	#23
nimzov Muse Join Date: Apr 2004 Location: Montréal Posts: 917	Originally Posted by uruk If you role a billion dice and they all come up sixes once, chances are pretty good that they will all roll up sixes again if you roll them long enough seeing as the possibility is there for them to roll up all sixes in the first place. Though, I could be making the gambler's fallacy in this instance. To stay with you dice analogy. I think the problem is that we do not know how many faces the dice has. The more faces, the less likely it will happen again. nimzo

25th October 2007, 03:26 PM	#24
Complexity The Woo Whisperer Join Date: Nov 2005 Location: Minnesota, USA Posts: 9,263	Greater than 0 (sorry, fundies), less than 1 (sorry, abductees).
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25th October 2007, 03:29 PM	#25
Jimbo07 Illuminator Join Date: Jan 2006 Posts: 3,417	Originally Posted by Complexity Greater than 0 (sorry, fundies), less than 1 (sorry, abductees). I'm not a fundy. I'm not even religious. It may still be 0. We may be the only ones even without FSM having anything to say about it...
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25th October 2007, 03:57 PM	#26
BenBurch Gatekeeper of The Left Join Date: Sep 2007 Location: The Universe 35.2 ms ahead of this one. Posts: 32,150	The dice analogy is not apt. More apt is that we understand that the dice HAS faces, and have set some upper and lower bounds on the number of these faces, representing our understanding of cosmology, nucleosynthesis, organic chemistry, and biology that allows us to establish these parameters.
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25th October 2007, 05:26 PM	#27
JJM Graduate Poster Join Date: Nov 2006 Posts: 1,855	Originally Posted by nimzov January 9, 2007 - Peter Ward, Professor of Biology and Earth and Space Sciences, University of Washington: "The Undesigned Universe: Part 1: Designs on Life" http://realserver.princeton.edu:8080...9wardVN350K.rm {snip} I cannot get audio on my computer. However, I am well-aware of Ward's nonsense, often published along with an equally confused fellow named Brownlee, and their Young Earth Creationist friend Gonzalez. The latter likes these ideas because he can tell his congregation that science proves we are god's unique creation. They begin with the the ideas that life can only exist within a certain distance of a Sun-like star in a certain region of a Milky Way-like galaxy. Then they assign life-promoting reasons for Solar system features, such as Saturn and our Moon. They have quite a list of requirements, and they proceed to calculate a small probability for all these features to come together to allow "life" elsewhere. What is wrong? They are drawing a line through the single data point they have on "life" (us) and extrapolating to the dimensions of the Universe. They have no idea how life could adapt to other situations, or how other system features could replace Jupiter or the Moon. When Ward talks about finding "life," he is talking about finding other Earth-like planets in Solar-like stellar systems, nothing more. His ideas that life is extremely rare are baseless, and can be safely discarded. In other news, Ward and Brownlee wrote a book after finding a computer program that would extrapolate plate tectonics for hundreds of millions of years into the future. Using that, they learned that the continents are headed for a configuration that would give rise to an uninhabitable Earth at some time. Do you see how easy it is to use extrapolation, and a fevered imagination, to come up with a just-so story? I don't know if Ward does anything useful in science; but his popular writings are junk.
JJM Graduate Poster Join Date: Nov 2006 Posts: 1,855	Last edited by JJM; 25th October 2007 at 05:42 PM.

25th October 2007, 05:33 PM	#28
uruk Philosopher Join Date: Apr 2003 Location: In the land of the Shatner stealing Mexico touchers Posts: 5,313	Originally Posted by nimzov To stay with you dice analogy. I think the problem is that we do not know how many faces the dice has. The more faces, the less likely it will happen again. nimzo Good point. I just think that since it happened here there's no reason to believe that it could not happen elsewhere. And if the mechinisims to create life exists in the first place well then.......
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25th October 2007, 05:42 PM	#29
uruk Philosopher Join Date: Apr 2003 Location: In the land of the Shatner stealing Mexico touchers Posts: 5,313	Originally Posted by BenBurch The dice analogy is not apt. More apt is that we understand that the dice HAS faces, and have set some upper and lower bounds on the number of these faces, representing our understanding of cosmology, nucleosynthesis, organic chemistry, and biology that allows us to establish these parameters. There is some evidence to support that life can exists (even in a dormant state) in conditions that are very harsh. Earth bacteria remained viable even after spending several years in the environment on the moon. See Apollo 12 and the surveyor camera that was returned to Earth. Doesn't that open up the possibilites any?
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25th October 2007, 05:48 PM	#30
Whack01 Thinker Join Date: Oct 2007 Posts: 199	Originally Posted by Complexity Greater than 0 (sorry, fundies), less than 1 (sorry, abductees). Why does fundamentalism imply that life cannot exist elsewhere in the universe? Doesn't it merely imply that life would have had to be created elsewhere in the universe as opposed to evolving? ETA: I'm not interested in debating the merits/demerits of the position, just what it actually is.
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25th October 2007, 08:33 PM	#31
Jimbo07 Illuminator Join Date: Jan 2006 Posts: 3,417	Originally Posted by Whack01 Why does fundamentalism imply that life cannot exist elsewhere in the universe? Doesn't it merely imply that life would have had to be created elsewhere in the universe as opposed to evolving? ETA: I'm not interested in debating the merits/demerits of the position, just what it actually is. I think it has more to do with Biblical literalism and the garden on Earth and being created in the FSM's image, etc. Again, though, if it were fact that we were the only ones... it would be a quite independent piece of information from that of Ed's influence.
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25th October 2007, 08:55 PM	#32
Badger Member of the Peanut Gallery Join Date: Jul 2002 Location: In the country Posts: 3,441	I remember reading about clay being involved in the development of replicating molecules. A quick google search supplies: http://www.origins.rpi.edu/claycatalyzed.html and http://www.springerlink.com/content/p8w6w63012773566/ My personal opinion is that the existence of self-replicating molecules elsewhere in the universe holds high probability, as the basic chemical reactions and interactions would be pretty common. What they turn into after they start self-replicating....well, who knows.
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25th October 2007, 09:28 PM	#33
Corsair 115 Philosopher Join Date: Apr 2007 Location: Tranquility Base Posts: 8,572	Originally Posted by JJM They begin with the the ideas that life can only exist within a certain distance of a Sun-like star in a certain region of a Milky Way-like galaxy. Then they assign life-promoting reasons for Solar system features, such as Saturn and our Moon. They have quite a list of requirements, and they proceed to calculate a small probability for all these features to come together to allow "life" elsewhere. That was the case laid out in Brownlee's and Ward's book Rare Earth: Why Complex Life is Uncommon in the Universe. As someone who has purchased the book some years ago and read it, I would say your criticisms are way off base. First off, their conclusion is that bacterial life is most likely very widespread in the universe, but complex life (e.g. animals, humans) is likely very rare. The reason: bacterial life is simple, can exist in a vast variety of environments (many of which would be fatal to complex lifeforms), and can survive environmental changes which would eliminate more complex organisms. Complex life, on the other hand, tends to need much narrower ranges of environments in which to survive, and is much more susceptible to changes in the environment which can kill it off. The case they lay out in their book is well supported by the studies and works of a great many other scientists. The reference section of the book is 26 pages long, and lists quite specifically all the other works they reference in their book. I found the case the book makes to be compelling, well constructed, and well supported. I would recommend it to anyone interested in the subject matter. You are free to try and refute the claims made in it by either demonstrating the references they use are inaccurate or by pointing to material which directly disproves the material they use to support their thesis. Originally Posted by JJM What is wrong? They are drawing a line through the single data point they have on "life" (us) and extrapolating to the dimensions of the Universe. Depends on how you define data point, doesn't it? Is life on Earth a single data point or millions? After all, a human being is not a crab which is not a maple tree which is not a bacteria. Originally Posted by JJM His ideas that life is extremely rare are baseless, and can be safely discarded. See first reply. In the aforementioned book, the case is quite clearly that bacterial life is likely very widespread but complex life is likely very rare. Originally Posted by JJM In other news, Ward and Brownlee wrote a book after finding a computer program that would extrapolate plate tectonics for hundreds of millions of years into the future. Using that, they learned that the continents are headed for a configuration that would give rise to an uninhabitable Earth at some time. I saw that book in the bookstore but not happen to purchase it. My recollection, from having thumbed through it, was that their contention was that in the very long-term Earth would have too little carbon in the atmosphere and thus would become too cold for life. I didn't thumb through enough of it to see or recall the plate tectonics part you to which you are alluding.
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26th October 2007, 02:22 AM	#34
JJM Graduate Poster Join Date: Nov 2006 Posts: 1,855	Originally Posted by Corsair 115 That was the case laid out in Brownlee's and Ward's book Rare Earth: Why Complex Life is Uncommon in the Universe. As someone who has purchased the book some years ago and read it, I would say your criticisms are way off base. {snip} I found the case the book makes to be compelling, well constructed, and well supported. I would recommend it to anyone interested in the subject matter. I don't have the book at hand. Can you look and tell me how many stellar systems they examined, and how many had "life" however they define it? I am pretty sure the answer to both questions is one, and everything else is pure speculation. Theirs is an interesting notion, and seems well-written for the lay audience; such that a lot of people found it compelling. Nonetheless, it is science fiction. Originally Posted by Corsair 115 {snip}
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26th October 2007, 02:52 AM	#35
SomeGuy Critical Thinker Join Date: Mar 2007 Posts: 497	Originally Posted by Jimbo07 I'm not a fundy. I'm not even religious. It may still be 0. We may be the only ones even without FSM having anything to say about it... You are wrong, the number of other life forms in the universe can be 0, but we're discussing the chance that other life forms exists. The chance is necessarily non-zero, because we know that life can come into existence given the right circumstances, else we wouldn't be discussing this. So he is completely right that the chance (untill we've fully explored the universe) is non-zero. Note that the provisional chance that there are other life forms in this universe will go down if we discover more and more planets without life forms on them.
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