Thread: Hunt for Aliens on National Geographic Channel

Hunt for Aliens premieres Thursday, April 1st at 8 PM ET on the National
Geographic Channel. It’s a strong show that’s chock a block with cool science.

Beyond stereotyped images of UFOs and little green men, if you press many
leading scientists, they will make a startling admission. Deep in their
bones they believe that intelligent life exists elsewhere in the universe.
In this mind-bending special, scientists will reveal the evidence that has
changed expectations about the existence of alien life. From an underground
ocean on a planetary moon, to the discovery of distant planets, to a
detailed imagining of what contact could be like, Hunt for Aliens takes a
serious and scientific look at the greatest question of all: How will we
meet ET?

Hunt for Aliens features Peter Smith, Richard Greenberg, University of
Arizona; Geoff Marcy, University of California Berkeley; Debra Fisher, Yale,
Seth Shostak, SETI; Simon Conway Morris, Cambridge University; and Geoffrey
Landis, NASA.

More info at: http://channel.nationalgeographic.co.../4276/Overview

Hi,

Well yes I agree....to say that life only exists on this ball of rock defies logic!

Life only exists on this ball of rock.

To accept belief as fact is illogical and the facts are that we have not found any evidence of life, let alone intelligent life, anywhere. Microbes may eventually turn up lots of places, but we haven’t found one of them yet. Multi-cellular creatures have only existed here for a fraction of the Earth’s existence. The number of species that have existed on Earth is something like 10^12. The number that could build a campfire is less than ten.

Probabilty also states that we arent alone. The Milky Way has 200 Billion Stars, many of these will have planets orbiting them and the milky way is one of billions of galaxies. This makes it logical to assume that somewhere there is life besides on Earth but it will be so far away that we will never know about it never mind find evidence.

Probability makes no such statement, because we do not know what the odds are. If the odds are one planet with life in a hundred billion galaxies, and there are only a hundred billion galaxies, then we are it. Logic is a discipline of philosophy, not science. Let’s say that I assume that creatures live in the core of the Sun. I arbitrarily set the chance to be only 1 in 200 billion. Then I could point out that there are 200 billion stars in the Milky Way, so logically the Sun could be the populated one. For science, this assumption would remain as such until I could prove my claim. There is still no proof of life elsewhere.

When it comes to statistics, it would be sensible to assume that the Earth is not special or statistically abnormal. Life here = life elsewhere.

I would imagine that the Universe is teeming with life, although I'm not too sure of there being a great deal of intelligent life out there. In fact, it wouldn't surprise me at all if there wasn't. Then again, perhaps numbers are on our side since estimates of habitable planets within just our own galaxy range from 10 million to 40+ billion.

Originally Posted by Zwirko

When it comes to statistics, it would be sensible to assume that the Earth is not special or statistically abnormal. Life here = life elsewhere.

Thats what I was getting at. I just didn't express myself properly perhaps.

Originally Posted by Zwirko

When it comes to statistics, it would be sensible to assume that the Earth is not special .

Since we have not determined the pathway(s) of abiogenesis we cannot assume that the Earth is not special. Some bizarrely unlikley step, or combination of steps may have been responsible. We simply do not know. Once we have established plausible pathways in detail and have explored these in the laboratory it would be possible to make such statements (or not).

Originally Posted by Zwirko

I would imagine that the Universe is teeming with life, .

Imagine all you want. Imagination is a great thing and can serve as the inspiration for great science, but it is not science.

Originally Posted by Zwirko

Then again, perhaps numbers are on our side since estimates of habitable planets within just our own galaxy range from 10 million to 40+ billion.

Estimates range from one to 40+billion.

There is no reason at all to assume that life on earth is special or unique, regardless of how we understand its beginnings or not, in the same way that cosmologists assume that our corner of the Universe is not unusual. On the contrary, there are strong evidentiary reasons to assume to that life, particularly of the microbial variety, is very common. What we know currently would suggest that life is very common - whether it is or not is another story, obviously, and remains to be determined.

I've never seen as estimate of only one habitable planet in this galaxy before; can you provide a reference for that?

Actually I am instead very confident that intelligent life exists elsewhere in the universe deep in my brain. My bones don't know , or even believe, anything.

Originally Posted by Zwirko

When it comes to statistics, it would be sensible to assume that the Earth is not special or statistically abnormal. Life here = life elsewhere.

I would imagine that the Universe is teeming with life, although I'm not too sure of there being a great deal of intelligent life out there. In fact, it wouldn't surprise me at all if there wasn't. Then again, perhaps numbers are on our side since estimates of habitable planets within just our own galaxy range from 10 million to 40+ billion.

For us to be unique, abiogenesis would have to be extraordinarily rare event. We don't even know if whether there was one episode of abiogenesis on our own planet--though early hostile conditions might suggest multiple events. We don't know the conditions or evolutionary pathways from that initial life. So far though we simply don't know.

Not sure if you were agreeing or disagreeing with what I said, Lynx_Fox...

I'm not saying life is definitely out there, or how rare or inevitable its evolution was/is. I'm making an assumption as to how special the earth is or is not. To consider the earth a statistical freak requires a great deal more justification than to assume it's an average place for this particular class of object. From that starting point one could tentatively conclude that life was fairly common (Note, that this is very different from saying that life is definitely common in the Universe). The physical laws that underpin the Universe, it's chemistry and its distribution of astronomical objects would lend support to this assumption. Offhand, I can't think of any compelling reasons that would lead us to assume that the Earth is unique in harbouring life. Occam's razor, while not the arbiter of truth, is certainly useful.

Originally Posted by Zwirko

There is no reason at all to assume that life on earth is special or unique, regardless of how we understand its beginnings or not,

There is no reason to form any position on this matter since we are working with a sample size of one. We may readily form opinions, but these opinions are baseless in science. (My opinion is that life is quite common, though I am unsure about intelligent life. It is either incredibly common, or extremely rare, not something in between.)

Originally Posted by Zwirko

........ in the same way that cosmologists assume that our corner of the Universe is not unusual...

They do not assume this. They observe this. It is the similarity of galaxies, stars, stellar evolution, stellar composition, etc, all observable, that leads cosmologists to conclude that our corner of the universe is not unusual. There are tens of thousands of observations that confirm this. There is not a single observation of other life, so to assume that there is likely life elsewhere, based on our present total ignorance, is not an assumption, but a presumption.

Originally Posted by Zwirko

..On the contrary, there are strong evidentiary reasons to assume to that life, particularly of the microbial variety, is very common. ?

Great. Then since there is strong evidence for this you will readily be able to give me two specific examples.

Originally Posted by Zwirko

...What we know currently would suggest that life is very common -

You can say this as often as you want. It doesn't make it true.

Originally Posted by Zwirko

...I've never seen as estimate of only one habitable planet in this galaxy before; can you provide a reference for that?

Certainly. My own computations, using the Drake equation, produce a lower limit of less than one, which I have rounded up to 1, taking account of actual observations.

Edit: I should add for clarity that I consider that habitable includes within it the implicit notion of habitable for more than a few million years.

Originally Posted by Lynx_Fox

For us to be unique, abiogenesis would have to be extraordinarily rare event. .

I agree completely.

Originally Posted by Lynx_Fox

We don't even know if whether there was one episode of abiogenesis on our own planet--.

or whether it was inevitable, or the result of some really complex purely fortuitous events. I think that addition is implicit in what you say.

Originally Posted by Lynx_Fox

So far though we simply don't know.

Which is absolutely my point. The specualtion is fascinating and should lead, with proper research, ultimately to an answer, but at the moment all we know is that we don't know.

Ophiolite, what are you trying to demonstrate here? You have almost the exact same opinion on this matter as I do; namely, that life is probably common but smart life probably not. Nobody knows the definitive answers to these questions, this much is obvious and I've said as much myself. Making assumptions is part of the scientific process, as is speculation. As is having an opinion guided by the evidence available or lack thereof. This is one of the ways in which theoretical and hypothetical areas of science progress. You seem to think I am making statements of fact and absolute truth, or least responding as if I were. Do you honestly imagine I'm trying to "make it true" by suggesting that life is fairly common? Do you consider that I don't entertain the possibility that we are alone? Do you imagine that I think that we have answered any of these questions? To answer the question of life elsewhere requires direct observational evidence, clearly. We can, however, still ask the questions and use our existing knowledge to attempt to constrain the answers. We can also just talk and speculate as to what might be, or not be. Throwing our hands up in the air and saying "we simply don't know" in agnostic-fashion is pointless and not very helpful, and I daresay, not all that relevant to much of what I have said, since I already made qualifications to my own arguments and declared that we don't know.

Assuming that the Earth is unique is more of stretch than assuming it's average, in my view. Stars like our own are common. Other types of stars that would produce habitable zones are even more common. Planets exist around other stars. The same chemistry that exists here exists elsewhere. All the ingredients necessary do exist. Life here exists in the most surprising and unlikely places. These factors lend credence to the opinion that we are not a special case. What sort of evidence would lead you to consider the possibility that the earth is special, other than the possibility that it indeed just might be?

How did you get the Drake Equation to give you less than 1 habitable planet in the galaxy? Do you mean <1 habitable planet with intelligent life? The quote you made of my text was simply referring to the number of planets with conditions capable of supporting life as we understand it. I would suggest that less than 1 is a slight error. Europa, if it has liquid oceans beneath the surface, is theoretically capable of supporting life. Whether it actually does or not is not even relevant to the point I was making.

Cosmologists do indeed assume that our corner of Universe is not unusual. The assumption even has a name - The Cosmological Principle. It's observed to be true (as far as can be determined) in the observable Universe and is assumed to hold true here and beyond, in both time and space.

This is a science forum, not a Yahoo blog. Life exists on Earth. This is a factual statement supported by observation. You cannot make this statement about anywhere else in the universe. We don’t know how physics and chemistry conspire to create biology, so we don’t know what the odds are of life anywhere else.

Arch2008, I thought you said this was a science forum?

If we don't know the odds, then it would be safe to assume that it's either highly improbable or so probable (under the right conditions) that it was effectively inevitable. Which one is it? We don't know. Is there anything we do know, right now, that can help us swing the balance more one way than the other? Even for the sake of speculation or hypothesis? Can't you think of something? Perhaps design an experiment to test that something? What about thinking of something that would preclude some other opposing idea? Does it really matter that we on this forum, or science in general, can't actually determine the answer right now?

We will never know what the probability of life forming here on Earth was. Ever. All we can say for sure, right now, is that its onset was rapid. To make a case for improbable it'd be nice to at least try and think of things that would make it so. Is talking about odds even the right way to go about this? ID, anyone? Why not try and determine how common are environments where we think life, as we understand it, could possibly arise? That the best we can do. Forget any imagined need for odds, it makes it sound as if you are looking for a divine spark or something.

Thinking about life elsewhere in the universe falls squarely within the domain of science. There is nothing wrong in being of the opinion that life is common out there. I'm not scared to stick my neck out and speculate, are you? If I was running around this forum declaring that science proves the universe is full of life, then that would indeed be a problem. So far, I ain't done that and don't plan to. I'm fully aware of what we do know and don't know and what we are in principle capable of knowing or not knowing.

NASA has a department dedicated to discovering Astrobiology and Exobiology. SETI has been listening for signs of intelligent life for decades. I applaud and support their efforts. However, there is a Mariner canyon between fact and assumption. We will eventually know what the mechanism was that created life on Earth. Why wouldn’t we?

Simply put, we will never know without time travel.

We can only ever guess or come up with possible solutions as to how life got its start. We could create abiogenic scenarios in the lab, but how would we ever know which one was the one that actually happened? How would we know how many failed attempts there were before that, or even after that? Or if the leftovers of one were used as substrate for another? We can't, because the early details have been lost and erased in the depths of time. Best that we could do is to limit the range of possibilities. It's also likely that we will never even know the exact conditions of the early earth under which life evolved for the first time. Likewise, finding life on another planet will tell us nothing about how probable the evolution of life on earth was. If we did manage to produce a detailed possible mechanism, then how would you go about calculating its "probability"? Is such a calculation possible? Or even meanigful?

You could, however, estimate how likely it was for conditions that we think are conducive to life to occur elsewhere. Places where life could evolve would appear to be abundant in the Universe. Whether they do or do not harbour life is a completely different story and one we can't answer right now. Our astrobiology friends keep extending the range of places where we think life is potentially possible.

If we can calculate what is going on in the universe at 10^-34 seconds after the Big Bang, why couldn’t we calculate the mechanism for creating life on one planet? These are the things that science does. We just need more data and that will come with time, but we ain't there yet.

Well, how would you know your "calculated mechanism" was the actual mechanism that occurred and not just one possibility out of many? Would you make an assumption? Would it be an inconvertible fact? Your mechanism might be one that the Universe has never even seen before - maybe even a better one.

I wonder if it's even experimentally observable?

And once you had a mechanism, how could you go about assigning it a probability? All you could do, as I have already stated, is to estimate how many places there are where such conditions might exist.

The physical nature of the universe is a lot simpler than life, which is why we are able to talk about early periods such as fractions of a second after the BB. Life is some weird emergent property of the universe that can't be pinned down so easily. The path life took from A to B in deep time will never be known for definite, in my opinion. You'd really need to go back and witness it.

Originally Posted by Zwirko

Ophiolite, what are you trying to demonstrate here?

I am seeking to demonstrate that the assumptions on which you are basing your opinions are flawed; that you are making categorical statements without substantiation.

Originally Posted by Zwirko

Making assumptions is part of the scientific process, as is speculation. .

As I noted earlier you were making unwarranted assumptions that became presumptions. That is not science.

Originally Posted by Zwirko

Throwing our hands up in the air and saying "we simply don't know" in agnostic-fashion is pointless and not very helpful,

You entirely miss the point. I am not throwing my hands in the air. I am clear defining the current limits of our knowledge and indicating ways in which these limits may be pushed back. My position contains no 'assumptions' that cannot be fully justified.

Originally Posted by Zwirko

What sort of evidence would lead you to consider the possibility that the earth is special, other than the possibility that it indeed just might be? .

Perhaps I have been unclear. I do not find it unlikely that there are several planets with very similar environment to the Earth. My sticking point lies with the process of abiogenesis. Until the contraints on this are determined with much greater acuity than at present then on the low probability end of the spectrum life on Earth may be unique.

Originally Posted by Zwirko

Cosmologists do indeed assume that our corner of Universe is not unusual. The assumption even has a name - The Cosmological Principle. It's observed to be true (as far as can be determined) in the observable Universe and is assumed to hold true here and beyond, in both time and space.

And that is based upon the observation that stars here are the same as stars there. That planets here are the same as planets there. That galaxies there are the same as galaxies here. That the chemistry here is the same as the chemistry there. We have observed all of this.

We cannot say the same about life because we have not observed it anywhere else.

Making testable predictions based on assumptions can not be accused as "not science". As stated several times now, I entertain both possibilities but have chosen in this thread to argue one particular corner. The assumptions I make are not unwarranted. My only assumptions are (i) the universe is the same everywhere and (ii) that there is nothing unique about the earth (it's physical, chemical and geological processes). Neither of these claims is controversial, unwarranted, unscientific, unjustified or untestable; they do not fall outside the domain of science.

You're right in that life on earth may well be unique (I even harbour a fear that it might be). However, ignorance of how life got it's start is no reason to dismiss my arguments. All you have done, really, is to state that life here might be unique and that we don't know enough to say either way. That's true enough, but what I find interesting is why people often assume abiogenesis to be an incredibly improbable event - almost miraculously so at times (not accusing you of this). To me, it's just chemistry. I don't think we'll ever know how it started or how likely/unlikely its occurrence on earth was. It would seem to be an impossible experiment to determine. As such, it appears a weak argument to make, since the evidence will not be forthcoming and won't shed much light on the problem that we are discussing here, if it was.

It is only by detecting life elsewhere in the universe that the issue of how common life is and how improbable/probable it is will be settled. So far, we are detecting places that we think are capable of supporting life and that such places are abundant. Until then, I agree, we simply don't know.

Other than musing that life may be highly improbable, I see no sound arguments here to swing the pendulum further to the unique side other than keeping an open mind to the possibility that that just might be the case.


---- edit:

Lets imagine that we finally elucidated the full sequence of events that led to the development of life on Earth. Say, a sequence of steps from simple chemistry through some critical pre-biotoc steps such as self-replicating systems and so on all the way up to some kind of primitive proto-cell and beyond. With this knowledge at hand, what would it actually tell us about how common life was in the universe? Or how likely it was on Earth? Wouldn't we be in the exact same position we are in now? We already know life evolved here via a process that was governed by a common set of physical and chemical laws that are shared throughout the universe. Our dicovered abiogenesis pathway would also be constrained by these laws. All we'd know is how it happened, as opposed to knowing that it did happen. That leaves in the same boat - did it happen eleswhwere? It would only be by discovering some truly bizarre chemical behaviour, unique to the earth, that the abiogenesis argument can be considered as interesting. Neither do I think you could assign this sequence of events a probability.

What is far more tenable is the idea that events in the Earth's formation were maybe important - and possibly that a strange sequence of events was required to set up the initial conditions under which abiogenenesis could take place. But given the size of the universe, this would suggest the earth is not even remotely anywhere near unique. I think I'm saying here that the conditions under which abiogenesis took place are of more relevance to this issue than discovering the details of the process itself.

Here’s the Drake equation:
http://en.wikipedia.org/wiki/Drake_equation
Scientists have been trying to find data to determine the actual hard value of the terms in the equation. We have a pretty good idea of average rate of star formation and we are working on the fraction of stars that have planets. So why wouldn’t we attempt to figure out the average number of planets that can potentially support life? To do this, we would have to better understand the mechanism that created life here. The mechanism may be quite simple. Some spectroscopy evidence already suggests that stars only slightly different than the Sun do not create certain chemical pre-cursor compounds in their proto-planetary disks. Without these compounds there may be no chance for life.

Well. that's more or less what lies at the heart of my argument, arch. It's the conditions necessary for the development of life that interest me here. Given the size of the universe (and that it's made of the same stuff everywhere) then it's difficult to imagine a plausible situation in which the earth ends up with an early environment that is radically different from anywhere else. Yes, many locations can be deficient in certain molecular species, but the Drake equation itself (and its modern equivalents), using our current knowledge, yields large numbers for venues capable of supporting life.

I agree that understanding how life started here would be helpful. But I have doubts that we will ever know the details well enough - simply because the information has been permanently erased from history as life transitioned to a nucleic acid- and cellular-based existence. We already have some plausible abiogenesis scenarios being hypothesised, but how to tell which is right? Will we ever understand the formation of life, here on earth, in precise chemical detail? We know that life did evolve here, so understanding the early conditions of the earth via the tools of geology will likely be as fruitful, or more so, than postulating a possible pathway for abiogenesis.

Often when folks use the abiogenesis argument they fall down the trap of thinking about probabilities of fantastical chemical reactions (thinking like intelligent design followers) in a way that's not helpful. Maybe I mistakenly assumed people here are thinking that way. It's thinking about environments that are key here, to my mind. Which then begs the question: is it really likely that the environment of the early earth was unique?

All I'm really arguing here is, not that life is actually common, but that the life-is-common argument is ever so slightly more justified than the life-is-rare argument (excluding direct observation of only one planet with life, of course). Most of the life-is-rare arguments are really just based upon "we don't know" and it "could be" - both points, I agree, may well be true. While statistical anomalies pop up all the time, I'm not keen, right now (nor see any evidence) that there is something strange going on in our patch of the universe. Tell will tell though...

That life on Earth is rare and unique isn’t an argument, it’s a fact until we disprove it. There have been something like a total of 320 billion human beings, but so far it is a fact that Albert Einstein and Mother Teresa were rare and unique individuals. Just because there are hundreds of billions of possible places for life doesn’t automatically mean that there are more instances of life. Science is based on fact. Research is based on logical assumptions. Ancient peoples assumed that there were half human half animal creatures. It didn’t seem logical to them that humans should be rare and unique. Now, we know for a fact that this is not possible, because different species cannot interbreed. We know how DNA controls this mechanism of creating life. We will continue to do research until we learn the rest of the mechanism of life.
The atoms in my body were created in a supernova. There are no miracle molecules or divine atoms in me. However, this is the only place we know of where molecules evolved to make organisms.

Arch2008: Your claims are pseudoscientific.

hmmm i wonder what aliens would look like if they were intelligent (id like to think they look precisely like us but that would be to much to ask for. lol there body's would probably be composed out of several elements we have never even heard of lol

Originally Posted by Arch2008

That life on Earth is rare and unique isn’t an argument, it’s a fact until we disprove it. There have been something like a total of 320 billion human beings, but so far it is a fact that Albert Einstein and Mother Teresa were rare and unique individuals. Just because there are hundreds of billions of possible places for life doesn’t automatically mean that there are more instances of life. Science is based on fact. Research is based on logical assumptions. Ancient peoples assumed that there were half human half animal creatures. It didn’t seem logical to them that humans should be rare and unique. Now, we know for a fact that this is not possible, because different species cannot interbreed. We know how DNA controls this mechanism of creating life. We will continue to do research until we learn the rest of the mechanism of life.
The atoms in my body were created in a supernova. There are no miracle molecules or divine atoms in me. However, this is the only place we know of where molecules evolved to make organisms.

That life is rare is not a fact at all. We don't know enough to make a definitive statement either way, surely? If I argue that life is probably common (or rare), then it's an argument by definition.

What the heck is a fact anyway?

Mount Everest is the highest mountain on Earth.
The Pacific Ocean is the largest ocean on Earth.
Life on Earth is rare and unique.
All of these are factual statements based on observation until someone discovers a higher mountain, a bigger ocean or life elsewhere.
Life exists elsewhere. This is a statement that is not supported by observation and is therefore not a fact.

The philosophy of the word "fact" is a little more complicated than what you have attempted to illustrate. That's besides the point though.


You can't state "life is rare" and claim it as fact. It's a hypothesis; it's not a statement of truth. My own argument is also a hypothesis, and not a statement of fact. That life does not exist elsewhere is, by your own definition, not a fact either because it's not supported by any evidence.

As I keep saying over and over: we don't have any evidence one way or the other to make any definitive statements as to whether life is common or rare. What we can do, while we look for evidence, is discuss whether it is likely to be rare or common. Those who think life might be rare make their arguments largely on the grounds that it is statistically possible that we are indeed unique. I accept that as plausible. I think it's unlikely, for the exact same reasons - statistics.

I'm curious why we stop at humanoid intelligence. On Earth, we're the smartest creature (perhaps not smarter than whales and dolphins, but certainly close.) In space, there's no reason to assume that the IQ scale wouldn't go way above us.

Just as we create wild life preserves for tigers and elephants, and try to keep poachers and other miscreants from disturbing them, it's totally possible that some more intelligent species has decided to create a wild life preserve for us, and that's why aliens have been avoiding contact. I know it's not a very comforting, or flattering thought, but if one leaves their own feelings out of the equation, it's not entirely improbable. Just very insulting to our collective ego.

Originally Posted by Ophiolite

Originally Posted by Zwirko

When it comes to statistics, it would be sensible to assume that the Earth is not special .

Since we have not determined the pathway(s) of abiogenesis we cannot assume that the Earth is not special. Some bizarrely unlikley step, or combination of steps may have been responsible. We simply do not know. Once we have established plausible pathways in detail and have explored these in the laboratory it would be possible to make such statements (or not).

I think in general, it is better to assume that you haven't won the lottery, and everything you see around you is not a fluke. Flukes are rare events. The norm is not a rare event. This leads me to conclude that, absent any evidence to the contrary, we should assume the likelihood of any given event being normal vs. that same event being abnormal overwhelmingly favors it being normal.

That said: many mid-evil astronomers thought there would be humanoid populations on Mars, Venus,.... etc..... and they were clearly wrong. At least among the 8 known planets nearby, the Earth is clearly abnormal.

Originally Posted by Zwirko

That life is rare is not a fact at all. We don't know enough to make a definitive statement either way, surely? If I argue that life is probably common (or rare), then it's an argument by definition.

Zwirko,

It's called the goldilocks zone or the habitable zone (HZ). Life is rare, but the Universe is huge (that's an understatement) and rare things happen all the time. Just think of it like this - most likely, there is life on another planet in the Universe somewhere, but it's probably "In a galaxy far far away . ."

I was thinking more along the lines of the Principle of Mediocrity: we're not special and don't occupy a special place. As far as we can see we're composed of the same stuff as everywhere else.

The idea of a Goldilocks Zone is a great starting point when thinking about where life may be possible and where to point our next generation of telescopes - indeed, finding out how many terrestrial-sized planets are found in the so-called habitable zone of various types of stars is one of the primary objectives of the Kepler mission.

However, looking at life on this planet it becomes clear that the range of possible places life could potentially exist is greater than one would imagine at first. As we explore our own planet it is becoming apparent that life seems to have no problem living in some quite brutal environments - boiling springs, hydrothermal vents, miles underground, under ice etc. Some of these ecologies do not even use the Sun as the primary source of energy. In this solar system alone there are perhaps three places that would be fascinating to explore in detail in the search for life: Mars, Europa and Enceladus. While I wouldn't bet on finding anything in those places, I hope you can see that the possibility exists.

“Life exists on Earth.” This is a fact.
“We have found no life anywhere else.” This is also a fact until disproved by observation (not arbitrary statistics).
“Something that exists in one instance is rare and unique.” This is a definition.
“Therefore, life on Earth is rare and unique.” This is also a fact, by logical conclusion, until evidence to disprove this is found.
“We believe that life exists elsewhere.” This is a belief (one that I share).
“We think that life exists elsewhere.” This is an assumption.
“We really, really want there to be life elsewhere.” This is a desire.
“Life exists elsewhere.” This is a statement that is not supported by any observation.
If you can get the latest copy of Astronomy magazine, there’s an article on the newest data for the terms in the Drake equation. However, a statistical argument for life elsewhere is not an observation that life exists elsewhere.

Zwirko
Here’s a link to an advertisement for the Astronomy article:
http://www.astronomy.com/asy/default.aspx?c=a&id=9457
Star clusters produce huge stars that fuse hydrogen into the heavier elements and then go supernova after only a few million years. Many solar masses of these elements pepper the surrounding cloud and the shockwave may hasten the creation of stars like the Sun. A star can thus acquire a proto-planetary disk very rapidly. Apparently the chemical building blocks of DNA are simple to produce. We know of organisms as small as 400 nm in diameter and viruses based only on RNA are a fraction of this size. Finding something like this on Mars would be incredible. Even a fossil could be studied on the ISS without fear of creating an Andromeda strain. The problem with Europa or Enceladus is that the life may lie under miles of ice. Although the surface of these moons cracks and breaks, creating areas of easier access, any specimen must survive a return trip of many years to bring them to the ISS.

Originally Posted by Arch2008

“Something that exists in one instance is rare and unique.” This is a definition.
“Therefore, life on Earth is rare and unique.” This is also a fact, by logical conclusion, until evidence to disprove this is found.

That sounds more like a hasty generalization than solid logic. Given the tiny sample size (less than a dozen planets or large moon we even have good remote sensor for) there is insufficient data to conclude life is rare or unique.

Nonetheless, it is a fact until disproved. I'm not etching this in stone. All we have to do is find life elsewhere...which no one has.

Also, is it a hasty generalization to say that a species is endangered? After all, we haven't checked out the rest of the universe.

Originally Posted by Arch2008

Nonetheless, it is a fact until disproved. I'm not etching this in stone. All we have to do is find life elsewhere...which no one has.

You are engaging in a logical fallacy, outside the realm of modern science or formal logic...what makes it worse is you aren't qualifying your conclusion (which you mistakenly refer to as a "fact.")

Also, is it a hasty generalization to say that a species is endangered? After all, we haven't checked out the rest of the universe.

No because we have a great deal of credible evidence that the specific and long path of more than 3 billion years of evolution make an identical species on another planet a practical impossibility. It a completely invalid comparison.

Arch...

Really, "facts" is such a slippery word with many meanings and we're wasting a decent discussion going down this route. It's a pointless semantic game. Facts, as we should be using the word here, are things that are known or assumed to be true (whether they be in error or not). Yes, known facts can be overturned and shown to be false by new evidence. We don't know diddley about how common or rare life is. That we simply don't know the answer to this question is surely the correct and only sensible way as describing this situation? Not having any evidence to answer the question one way or the other does not default one of the possible answers to the status of fact.

I would suggest that you are one of the few people on this planet that would say “... life on Earth is rare and unique” and call it a fact in the sense that discussion on this forum would warrant. Yes, we are rare and unique in the sense that this is the only life we know of - you can call that a factual statement, because it's true. But it's not a fact in the scientific sense because we haven't determined our rareness or uniqueness yet. We are asking the question, not overturning something that is already known. What is the absolute truth? The fact that remains to be determined unequivocally and objectively via observation, and not a reflection of our current inability to answer the question?

Let me ask you this: do you think Europa, Mars and Enceladus are possible places that would be good places to look for alien life? Three possible places right on our own doorstep. 400 billion stars in this galaxy. That makes a stronger case for life being common than merely stating that the earth might be unique purely by chance. I don't know the absolute truth. Nobody does. Why do you find the life-is-rare-and-unique "argument/fact" more compelling? Lack of evidence to the contrary is not an acceptable answer because it tells us nothing about why the earth is unique.

So you can imply that 3 billion years of evolution would make all species on Earth rare and unique, but it is an illogical fallacy for me to imply that the 10 billion years that the universe evolved prior to that might make the first species on earth rare and unique? Got it.
I’m not talking about a philosophical argument as to whether or not life in the universe is rare or common. We would have to examine 100 billion galaxies to attempt to resolve that. I’m not trying to make points in modern science or formal logic. We know that life exists on Earth. We have not found life elsewhere. I have not said that we won’t, just that we have not. This makes life on Earth both rare and unique at the moment that I say it.

Originally Posted by Arch2008

I’m not trying to make points in modern science or formal logic.

I don't mean to be harsh...but you should be since that is the point of this forum.

Your statement that life is rare and unique as a fact isn't an application of either modern science or formal logic specifically because of the reason we both agree with--we don't have enough information.

All right then. What part of intellectual cowardice is it to shoot the messenger instead of debating the message? Life on Earth is rare and unique until you find life elsewhere. True or false? As long as you have not found it elsewhere, that statement is true. I do not have to explore 100 billion galaxies to say that because that is an absurd condition. If I say that the Easter Bunny really exists and that all I need is a little more time to find the evidence, then no one has to disprove this. We don’t have to explore the universe looking for the Easter Bunny, because I would have to present the evidence first. In the mean time, there are no Easter Bunnies or life elsewhere. Show how modern science or formal logic denies this.
You posted that life on Earth right now is rare and unique because evolution makes it practically impossible to repeat elsewhere. So when does it stop being rare and unique? Were dinosaurs less rare or unique? How about the first fish? Why do a few billions of years of biological evolution create life that is rare and unique, yet the 10 billion years of the physical and chemical evolution of the universe that preceded that event do not create the initial life on Earth as rare and unique? Modern science demands predictions that match observation. The search for El Dorado did not have a matching observation.
I am not a creationist or an intelligent designer. I commend and respect the astro biologists and exobiologists at NASA that are looking for life elsewhere. I watched the NatGeo show from the OP and it was really interesting, if you are 12 years old. You don’t need more information, you need proof. You can have all the time that you want, but until you get an observation, there is no life elsewhere.

Originally Posted by Arch2008

All right then. What part of intellectual cowardice is it to shoot the messenger instead of debating the message? .

Cut the crap. What is intellectually cowardly about pointing out to you gently that if you are not going to make points in a scientific and logical fashion then you are probably wasting your time on a forum ostensibly devoted to such pursuits.

Lynx Fox is trying to help you out, act as a mentor, and give you pertinent, accurate, useful advice. Your response is to adopt an injured defense posture. Grow up. (If you are in fact thirteen or fourteen I apologise. Your response is quite reasonable for someone of that age.)

Now to the message:

Originally Posted by Arch2008

Life on Earth is rare and unique until you find life elsewhere. True or false?

False. Completely, absolutely, irrevocably, undeniably, comprehensively, unmitigatedly false.
Our ignorance of the presence or absence of life elsewhere in the universe does not effect whther life is rare or common.
Let us suppose that there is life in every tenth solar system. By your argument if we don't know about that life then Earth life is either unique or rare. That's just wrong. Totally. (I'm shooting the message, not the messenger.)

Originally Posted by Arch2008

Show how modern science or formal logic denies this..

As stated above the existence of life elsewhere in the universe is wholly independent of our knowledge of it. (With the exception if we start to destroy such life upon discovering it.)

Originally Posted by Arch2008

You can have all the time that you want, but until you get an observation, there is no life elsewhere.

Again. this is pure and utter nonsense.
It is true that until you get an observation of life elsewhere then there is no definite knowledge of life elsewhere. If that is what you are trying to say then you need to improve your writing skills.

100% shoot the messenger. Let’s not suppose there is life elsewhere. Then what? What part of the scientific method says that you can suppose something exists without proof and that it is then beyond question?

When you say that we don’t know enough to say whether life elsewhere is common or rare, you make the logical fallacy that there is life elsewhere without proving it.
When you say that there must be life elsewhere in the huge universe, you make the logical fallacy that this means that you don’t have to prove it.
When I say that life on Earth is rare and unique, this is not a logical fallacy, because I added “until disproved”.

As for modern science, I have been through NASA’s Astrobiology and Exobiology sites and they do not state that life exists elsewhere.

I have the impression that I should intervene as an moderator before this discussion derails. Up to now, I quite ignored it because of lack of interest.

Scientific method: You need to prove your hypothesis.

Hypothesis 1: Life on Earth is unique in the universe.
Proof: Examine every single spot in the universe and see, whether there is no life anywhere else than earth.

Hypothesis 2: There are other worlds harbouring life.
Proof: Find a single spot except Earth, where life is present.

As long as you can't proof either, the question is undecided. Not finding any evidence does not mean that hypothesis 1 is true nor that hypothesis 2 is false. Until proof is found, we can only say that we know of no other place in the universe than Earth, where life exists. One of these possibilities is true, regardless of what we know. Up to now, we can't say anything, because we haven't even really started looking for life - maybe except Mars.

So, please calm down guys.

Wouldn't it be actually much more interesting to discuss, on what life and its emergence depends? For example, this infamous Drake equation is not worth very much, because the uncertainties involved with each single term are huge. I wonder, how significant any result would be, if you applied a correct error propagation.

In addition, how sensible is the so called inhabitable zone in a planetary system? Aren't there more parameters to include than just the combination of distance from and the effective temperature of the star? What about eccentricity of planetary orbits? What about atmospheres (pressure, density) and their chemical compositions?

Originally Posted by Dishmaster

Hypothesis 1: Life on Earth is unique in the universe.
...
Hypothesis 2: There are other worlds harbouring life.

What I was actually discussing (not through choice) are the assumptions that underpin such hypotheses. That is, are the underlying assumptions behind Hypothesis 1 weaker than those that Hypothesis 2 is based upon? It's a weird point to discuss perhaps, but one that few people seemed to have grasped. Everyone seems to think I'm arguing that life does indeed live in every nook and cranny of the universe. I've no idea if does or not.

To me, Hypothesis 1 is something that has a large cultural bias to it - something that is interesting in itself and likely more suited to another sub-forum.

I'm happy to call a truce on this somewhat irrelevant point that I got side-tracked on.

We could also add the idea that life did not even evolve on the Earth. This too is an unknown and something that it is taken seriously in origins of life studies. Getting some paleo guys to Mars would be a great step in answering this and shedding some light on the bigger question of is life unique to the Earth.

Re the habitable zone: I'm not particularly keen on the idea of a habitable zone. The early Earth was, somewhat paradoxically, someplace that we'd be inclined not too look for life. A real hell-hole of a place, yet life took to it incredibly rapidly.

Originally Posted by Zwirko

Originally Posted by Dishmaster

Hypothesis 1: Life on Earth is unique in the universe.
...
Hypothesis 2: There are other worlds harbouring life.

What I was actually discussing (not through choice) are the assumptions that underpin such hypotheses. That is, are the underlying assumptions behind Hypothesis 1 weaker than those that Hypothesis 2 is based upon?

This is a philosophical question rather than an empirical science question. As said, within science, the situation is undecided. Even though (nearly) all exoplanetary candidates are most likely not capable of sustaining life, we still cannot conclude anything on this question, because this is due to an observational bias. We are just not yet sensitive enough to detect meaningful signs. Philosophically, it depends on your attitude, whether you assume that Earth is something special or that it is quite ordinary. Scientifically, there is no reason to assume one or the other.

Dishmaster, my prior posts and this one are wholly calm. I am simply making observations in a direct and robust manner. Arch can either heed these and learn something, or place me on ignore.

Originally Posted by Arch2008

100% shoot the messenger..

Please tell me how the second half of my last post 'shoots the messenger'. If you cannot do so please retract the quoted statement.

I shall try this one more time.

1. I have no idea whether life exists elsewhere in the universe or not. I have made this clear in this thread.
2. I have some opinions on the matter, but even though they are informed opinions, that is all they are.
3. There may be life eslewhere in the universe, there may not.
4. We may choose to postulate the existence of other life or we may not.
5. Points 3 and 4 are completely unrelated. Do you understand that? It does not matter what we think about the matter, the existence of life elsewhere in the universe is not contingent upon our knowledge or expectation of it, yet that is exactly what you are claiming.

First off, I never claimed hypothesis 1. Not once, ever. So this is a strawman argument. I have stated throughout that life on Earth is rare and unique until we find life elsewhere. I have pointed out the logical fallacy of asking whether life is common or rare elsewhere in the universe without ever proving that it exists elsewhere in the first place. I did the same with the statement that the universe is huge so there must be life elsewhere, again without ever actually proving it. Science is the brutal guardian of what we can actually say that we know about the universe. We do not know that life exists elsewhere and that is what I’ve said throughout. Here is how logical debate works (check out “argument to ignorance or appeal to numbers):
http://www.csun.edu/~dgw61315/fallac...rn%20fallacies
I have never presumed to be anyone’s mentor. I hope that we are all adults here.

Ophiolite:
“Grow up. (If you are in fact thirteen or fourteen I apologise. Your response is quite reasonable for someone of that age.)”
Yeah, that was a wholly calm response you made in a direct and robust manner.

“Again. this is pure and utter nonsense.” (from the second part of your post)
You don’t consider this trying to shoot the messenger?

“5. Points 3 and 4 are completely unrelated. Do you understand that? It does not matter what we think about the matter, the existence of life elsewhere in the universe is not contingent upon our knowledge or expectation of it, yet that is exactly what you are claiming.”
We have no knowledge of something because it has not been proven to exist. When you insist that we must include it anyway because it exists in our ignorance, then you are again claiming that it exists without proof. Really read the link on logical debate and try some honest introspection.

It's amazing how hard it is to convince someone their logic is flawed. To be a wise ass I could simply point out that life does exist outside of earth. The last time I checked the International space station does in fact contain life, and it's not on earth.

The statements Arch is making about life on earth being rare and unique can only be answered if we know absolutely everything about everything. Until then it's neither true nor false. Until then it's a mute point to conclude either direction. Even basing life on statistics is flawed. We are not even sure if what we see is in fact real and can be reached. Until we have visited other solar systems we just assume they do in fact exist in a form we can reach. Granted this dives in to other subject matter entirely, it however is the same kind of paradox in logic. You can't prove anything beyond our solar system exists in a true physical form, so therefore you can't even statistically calculate the odds of life outside our solar system.

A thread that could have been useful has turned in to a bit of a waste of time. It would be better to set a foundation all the participants can agree on and discuss from that point forward. It's the same as saying if a tree falls in the forest and no one is around does it make a sound? It's a paradox of logic, it can't be proven either way with absolute certainty. It can also be argued for an eternity. I hope everyone see's my point.

Arch I amsure you are a nice guy, kind to cats and prepared to help old ladies across the road. However, your grasp of basic logical thinking is non-existent. I see no point in continuing to discuss this with you, since you seem incapable of understanding.

I'll pick on one simple thing that you ought to be able to understand.
I said of a portion of one of your posts
“Again. this is pure and utter nonsense.”

In other words what you had written - the message - was pure and utter nonsense. I did not say you were pure and utter nonsense. I shot the message, not the messenger. Surely even you can see this simple distinction. But apparently not for you claim this is attacking you.

You say:
I have stated throughout that life on Earth is rare and unique until we find life elsewhere.

Consider. In 1,000 years we develop interstellar spaceflight. We discover that almost every system in the galaxy has some form of life on one or more of its planets. That life has been there for over one billion years, yet according to you before we knew it was there life on Earth is rare and unique. That is a logical non sequitur, a monstrosity of unreason.

I suspect you will still refuse to recognise this, in which case I give up. Have a great life, but try not teach squirrels how to find nuts.

(In)Sanity I have been writing this post for an hour or more between phone calls and mini-meetings, so was unaware of your post and implicit request.

INsanity-Well if your point was to make a bunch of strawman arguments that I have not posted anywhere and thereby conclude something, then you made your point.

Ophiolite-You continue to shoot the messenger. Read the link on logic before you pretend to be using logic.

Originally Posted by Arch2008

Well if your point was to make a bunch of strawman arguments that I have not posted anywhere and thereby conclude something, then you made your point.

What strawman argument have I erected? These are your words:

I have stated throughout that life on Earth is rare and unique until we find life elsewhere.

Those words are illogical. This has been my point from the outset.
Are you claiming you did not write these words?
Are you claiming these words mean something else?
Are you claiming they are not illogical?

Well actually compare your posts to the links on logical fallacies and see for yourself if you have been logical. (although I was not responding to you.)
I’m not anti-exobiology. If…if there is life elsewhere we are doing what we can to try to find it. This is commendable. This does not mean that we have found it or that it is a given that it is out there. This is a distinction that some of you need to realize.

Originally Posted by Arch2008

Well actually compare your posts to the links on logical fallacies and see for yourself if you have been logical. .

I am confident that I have been logical in my posts in this thread. I am open to the possibility that I am mistaken. Please point me to where you think I have been illogical.

Secondly, do you accept that the quote of yours that I have included in both of my last posts is illogical?

I am confident that you can read the link on logical fallacies and do the comparison yourself. I have already pointed out the fallacies. As I posted, I was responding to Insanity, but you posted before me and then took offense that my post was directed at you. So I edited my post and then you responded before I could do this.

Originally Posted by Arch2008

I am confident that you can read the link on logical fallacies and do the comparison yourself..

I am very familiar with logical fallacies. I am wholly unaware of using any in this thread, so I ask again please specify wherein I have used a logical fallacy, or with draw the accusation. Or are you trying to say that someone else was posting an illogical fallacy? Please answer these direct questions directly and we can save each other a great deal of time.

I took no offense at anything you have posted. I see nothing in any of your posts to cause offense, unless one is offended by wooly thinking and poorly structured arguments. I certainly could take no personal offense at anything.

I am still waiting for you to answer these points. You stated:
I have stated throughout that life on Earth is rare and unique until we find life elsewhere.

Those words are illogical. This has been my point from the outset.
Are you claiming you did not write these words?
Are you claiming these words mean something else?
Are you claiming they are not illogical.

Now are you going to answer these or are you going to continue avoiding an answer? These questions are central to everything I have been raising with you. They are not strawmen. It was your persistent posting of such contradictory, illogical statements that caused me to begin raising these points with you. So for the third or fourth time of asking........ anything.........do you have answers? Well?

I'm still trying to figure out how something based on an assumption due to lack of evidence can be considered a fact. One can say at the present time we only know of life on earth. One can not say life on earth is unique. One could say life on earth is unique based on our current knowledge of existing life. There is very little that can be disputed as hard core fact, mathematics is one area where I would say something is a fact. Everything else can be countered by the unknown. As I said before, until we know everything and I do mean everything our 'facts" are subject to change. Math being an exception.

We can make assumptions based on our current knowledge and come to accept that as a theoretical fact. The "laws" of physics are subject to possible disruption, we however have come to assume these laws are solid enough to be considered theoretical facts. They are close enough to be factual in our known scope, outside that scope they could change. It's common place for people to accept certain repeatable outcomes as "facts". They are still however theoretical until nothing is left to question and even at that we simply are not capable of asking all the right questions.

It's a waste of time to split hairs on the semantics of logic. True logic can only be applied to mathematical outcomes, everything else is subject to scrutiny about the outcome. A thousand people can do a test and come to a conclusion they accept as fact. Someone else can come along and claim they were under the influence of mind altering drugs and what they witnessed didn't really happen. This loop of doubt can continue forever. Math on the other hand can't be disputed in such a way.

1+1 = 2, one assumption + another assumption doesn't = fact. Get it ?

Ophiolite
“Grow up. (If you are in fact thirteen or fourteen I apologise. Your response is quite reasonable for someone of that age.)”
“Arch I amsure you are a nice guy, kind to cats and prepared to help old ladies across the road. However, your grasp of basic logical thinking is non-existent. I see no point in continuing to discuss this with you, since you seem incapable of understanding.”
“I suspect you will still refuse to recognise this, in which case I give up. Have a great life, but try not teach squirrels how to find nuts.”
“I took no offense at anything you have posted. I see nothing in any of your posts to cause offense, unless one is offended by wooly thinking and poorly structured arguments.”
This is “Argumentum ad hominem (argument directed at the person). This is the error of attacking the character or motives of a person who has stated an idea, rather than the idea itself.”

“Our ignorance of the presence or absence of life elsewhere in the universe does not effect whther life is rare or common.
Let us suppose that there is life in every tenth solar system. By your argument if we don't know about that life then Earth life is either unique or rare. That's just wrong. Totally.”
“Consider. In 1,000 years we develop interstellar spaceflight. We discover that almost every system in the galaxy has some form of life on one or more of its planets. That life has been there for over one billion years, yet according to you before we knew it was there life on Earth is rare and unique. That is a logical non sequitur, a monstrosity of unreason.”
This is “Circulus in demonstrando (circular argument). Circular argumentation occurs when someone uses what they are trying to prove as part of the proof of that thing.”
You imply that my statement is invalid by posing an unproven hypothetical situation that makes it invalid.

“As stated above the existence of life elsewhere in the universe is wholly independent of our knowledge of it.”
This is “Argumentum ad ignorantiam (argument to ignorance). This is the fallacy of assuming something is true simply because it hasn't been proven false.”
For example, the existence of a unicorn elsewhere in the universe is also wholly independent of our knowledge of it.

“I have stated throughout that life on Earth is rare and unique”
This would be the logical fallacy of an argument to ignorance on my part, except that I added…
“…until we find life elsewhere.”
thus admitting the burden of proof.
“The accused is innocent until proven guilty.” is also not an illogical statement.

Originally Posted by Arch2008

“The accused is innocent until proven guilty.” is also not an illogical statement.

Actually it is an illogical statement that's based on a social courtesy rather then fact. They may in fact be vary guilty and never be proven such, it doesn't make them any less guilty. So I'm trying to see the logic in this statement. If you said in some countries they have laws that state "The accused is innocent until proven guilty" then perhaps that would be logical. I think the word logically and true logic have become far removed from one another.

I could logically conclude that this thread is going nowhere. It would however be illogical for me to state that it is.

Originally Posted by Ophiolite

“Our ignorance of the presence or absence of life elsewhere in the universe does not effect wehther life is rare or common.
Let us suppose that there is life in every tenth solar system. By your argument if we don't know about that life then Earth life is either unique or rare. That's just wrong. Totally.”
“Consider. In 1,000 years we develop interstellar spaceflight. We discover that almost every system in the galaxy has some form of life on one or more of its planets. That life has been there for over one billion years, yet according to you before we knew it was there life on Earth is rare and unique. That is a logical non sequitur, a monstrosity of unreason.”
This is “Circulus in demonstrando (circular argument). Circular argumentation occurs when someone uses what they are trying to prove as part of the proof of that thing.”

Originally Posted by Arch2008

You imply that my statement is invalid by posing an unproven hypothetical situation that makes it invalid.

You are partially correct, but mostly wrong. It would be a circular argument, if the conclusion was that life is common. But this not the case. The logical conclusion is that life might be common, or not. This only demonstrates that we cannot exclude this possibility, although we do not know, what's correct.

Originally Posted by Ophiolite

“As stated above the existence of life elsewhere in the universe is wholly independent of our knowledge of it.”

Originally Posted by Arch2008

This is “Argumentum ad ignorantiam (argument to ignorance). This is the fallacy of assuming something is true simply because it hasn't been proven false.”
For example, the existence of a unicorn elsewhere in the universe is also wholly independent of our knowledge of it.

Incorrect. Again, this would be an argument to ignorance, if the conclusion drawn from this would be that life is common. But the suggested conclusion from this argument is that we do not know, and we can certainly not say that life is rare or unique, because we do not have the necessary information. Since the argument portrays a possibility that has not been falsified, it can be used to invalidate the conclusion that life is rare or unique. However, it does not invalidate the possible fact that it is.

Originally Posted by Arch2008

“I have stated throughout that life on Earth is rare and unique”
This would be the logical fallacy of an argument to ignorance on my part, except that I added…
“…until we find life elsewhere.”
thus admitting the burden of proof.
“The accused is innocent until proven guilty.” is also not an illogical statement.

This demonstrates that your statement is a paradox. The first half sentence is still written in indicative mode, not in subjunctive mode. It would be a valid statement, if you said, "Life on Earth may be rare and unique until we find more proof for or against it". Your statement reads like, "This ball is blue until I look at it (and confirm it or see it is red instead)."

In fact, YOU are using an argument "non sequitur", because you take one side of the two possibilities without any grounds to decide which is true. Your second half sentence does not change this, it just turns it into a paradox.

Your last sentence is a legal definition and not based on logic. The law is that any accused should be regarded as if he was innocent. This does not mean that he actually is. It is simply assumed to be a social rule.

My client is innocent until proven guilty.
Let’s be really coy. Suppose your client may or may not be innocent. By covering both possibilities, one can perhaps introduce doubt without the need for proof.
Well, let’s examine this. If my client is innocent then that is that. If my client is guilty, then you have to prove it. Until then, my client is still innocent until proven guilty (which is most certainly not a mere social convention). The oceans on Earth are rare and unique until we find another planet with oceans of water. Life on Earth is still rare and unique until proven otherwise.
Saying that life may or may not exist elsewhere is not some kind of loophole. If life doesn’t exist elsewhere, then life on Earth is rare and unique. If life exists elsewhere, then prove it. Prediction requires observation. It’s the same rules for every other question that science has answered. If you state that life elsewhere is some kind of a given, because the universe is so large, or the physics and chemistry are so basic, or that the statistics are overwhelming, then these are fallacies in reasoning and not a substitute for proof. You have a prediction, now make an observation.

Originally Posted by Arch2008

My client is innocent until proven guilty.
Let’s be really coy. Suppose your client may or may not be innocent. By covering both possibilities, one can perhaps introduce doubt without the need for proof.
Well, let’s examine this. If my client is innocent then that is that. If my client is guilty, then you have to prove it. Until then, my client is still innocent until proven guilty (which is most certainly not a mere social convention). The oceans on Earth are rare and unique until we find another planet with oceans of water. Life on Earth is still rare and unique until proven otherwise.
Saying that life may or may not exist elsewhere is not some kind of loophole. If life doesn’t exist elsewhere, then life on Earth is rare and unique. If life exists elsewhere, then prove it. Prediction requires observation. It’s the same rules for every other question that science has answered. If you state that life elsewhere is some kind of a given, because the universe is so large, or the physics and chemistry are so basic, or that the statistics are overwhelming, then these are fallacies in reasoning and not a substitute for proof. You have a prediction, now make an observation.

You're really not seeing the flaws in your logic. The clients innocence or guilt is irrelevant of proving whether or not he or she is. Your "client" exists and is aware of their own guilt or innocence. Society may not be able to convict your client until he or she is proven guilty, this however doesn't change the fact that he or she is guilty. The same is true for life, we may not be able to prove if it exists or not, this doesn't change the fact if it does or does not.

Not being able to prove the client is guilty doesn't make them not guilty if they know they are or even if they somehow don't know. It's a math problem, 1+1 = 2. Inability to solve the equation doesn't change the answer.

Not being able to prove life exists elsewhere in the universe doesn't make it not exist. Again, it either does or doesn't, our inability to solve the equation doesn't change the answer.

To your defense you have changed your wording on some of your statements, still your logic is based on assumptions. We really can't assume life on earth is unique or not unique. It either is or it isn't. It may turn out that we live in the desert of the universe and other areas have more life then we can imagine. We don't have the facts, so assumptions are illogical.

You will often see the word logically attached to "assume". We logically assume your client is innocent until proven guilty based on the lack of supporting evidence. This still doesn't change the "logic" in whether or not he or she is, it only changes the logical assumption. We can logically assume life on the sun doesn't exist. Even if we could never categorically prove either direction it doesn't change the truth. It either is or isn't.

So while your statements are understood they are just a bit too liberal in their usage. With a few extra words added they leave open the room for lack of Boolean proof. You need to be sure assumptions are not stated as fact.

Again, all of you take it for granted that there is life elsewhere. Sure one can state that a guilty man can be found innocent, so perhaps life can exist elsewhere and we just don’t know it? Except that we did not yet prove that life can exist elsewhere. If we find life on say Mars and we don’t find it ever again, then for the rest of history we can say with scientific proof that life may exist elsewhere and we just haven’t found it (again). Until then, saying that life may exist elsewhere (or “may or may not” for the timid) is still a prediction without an observation. None of you seem to get this distinction.

Originally Posted by Arch2008

Again, all of you take it for granted that there is life elsewhere.

No, we don't. Nobody has said that. We always said, we don't know. And you don't know either. Based on the knowledge we have, both conclusions are unjustified.

When exobiologists tell someone, “We do not have enough information to say whether or not there is life elsewhere in the universe.”, they are doing this to get funds to look for the life elsewhere. This statement is meant to imply that there is life to be found as a given. Replace “life” with “a leprechaun” or “a fairy” and the public will no longer be interested. Of course, leprechauns and fairies are not as certain as life elsewhere. Why is that? Saying "may or may not" is not a magic loophole that creates the possibility of something without proof existing beyond our knowledge.
From the second post on, people have stated how life elsewhere is logical or a statistical certainty without a shred of proof. To think otherwise is reason for scorn (trust me, I speak from experience). What I do know is that we cannot make empty statements about life existing elsewhere until we prove that there is life elsewhere. When we have found life one other place, then and only then can we say with scientific certainty that life can exist elsewhere.

Unfortunately, I must eat and sleep. My wife has plans for me this weekend, but on Monday I shall read whatever posts are added and respond to any that are patiently directed my way. My humble thanks to those of you who have politely suffered my stubborn impudence thus far.

Arch,

In astrobiology there are two hypothesis that have been discussed in the literature at length on this very question. One is called the Rare Earth hypothesis, as originally put forth by Ward & Brownlee. The opposing view to this, which I have been supporting here, is known as the Mediocrity Principle, as advanced by many people including the likes of Sagan and Drake. Discussing the merits and/or problems of either view is an entirely legitimate point to discuss. Finding the Principle of Mediocrity more appealing than the Rare Earth Hypothesis does not equate to stating that there is in fact a universe teeming with life. And neither is it a logical fallacy of any kind.

And just to repeat: I don't know if life is common or not, nobody does. What I did say was that I think life will be common and that I base this on the Mediocrity Principle. By the same reasoning, I think that much of this life will likely be microbial in nature.

I also find some of the Rare Earth arguments, absent from this thread though they may be, quite compelling too.

I'd just like to say that I agree with both points as I previously struggled to point out in my last post in this thread. In my opinion, life is both rare and not. For example, let's say 5-10% of the universe is teeming with goldilocks zones that resemble Earth. On a Universal scale, it would be said as being abundant with life, right? However, from Earth, the perspective of life would be practically nonexistent elsewhere simply because of the distance between planets. It's rare in the sense that we may never reach or find evidence of life for another 2,000+ years, but this does not mean life could be said as being rare or unique. In simple terms, this is why I say that life is rare, but rare things happen all of the time considering the vast and plentiful gargantuan size of the Universe.

I consider looking for life elsewhere as a great endeavor, but I do not expect humans to find much of anything. Saying: 'it's like finding a needle in a haystack' isn't even a good analogy. With that said, I applaud any and all attempts towards finding such life on another planet, even if it's just a microorganism. Who knows, we could find something as crazy as a water bear, which is quite an extraordinary little guy.

One planet with life every other galaxy would give us a hundred billion (at least) planets with life, and we'd likely never discover any of them ever - what a depressing thought. A good point though, I like it.

Originally Posted by Zwirko

One planet with life every other galaxy would give us a hundred billion (at least) planets with life, and we'd likely never discover any of them ever - what a depressing thought. A good point though, I like it.

Thank you, i've been reading through these posts and was trying to express in words what was in my mind about how life could be said as both rare and not.

Originally Posted by Arch2008

When exobiologists tell someone, “We do not have enough information to say whether or not there is life elsewhere in the universe.”, they are doing this to get funds to look for the life elsewhere.

They may be doing this in part to obtain funds, bu they are primarily doing it because that is what they believe and the believe that because that is a well founded position to take that is wholly consistent with the evidence. Do you disagree?

Originally Posted by Arch2008

This statement is meant to imply that there is life to be found as a given. .

No it isn't. That is an unwarranted presumption of intent. Justify it, or retract it.

Originally Posted by Arch2008

Saying "may or may not" is not a magic loophole that creates the possibility of something without proof existing beyond our knowledge.

For the eighty seventh time ( ) whether or not life exists elsewhere is wholly independent of our knowledge of that life. What don't you get about this simple concept?

Originally Posted by Arch2008

What I do know is that we cannot make empty statements about life existing elsewhere.

And you have persitently made exactly such empty statments, declaring that until we find life elsehwere then life in the Universe is rare.

Originally Posted by Arch2008

When we have found life one other place, then and only then can we say with scientific certainty that life can exist elsewhere.

Finally something we can agree on and that would meet, I believe, agreement from everyone else here.

Originally Posted by Ophiolite

Originally Posted by Arch2008

When we have found life one other place, then and only then can we say with scientific certainty that life can exist elsewhere.

Finally something we can agree on and that would meet, I believe, agreement from everyone else here.

I think the main error made here is that Arch seems to think that there are only two options, and nothing in between. But this depends on the statement to be made.

The question on the existence of life anywhere else than on Earth indeed only allows two options: There is or there isn't.

The question on the knowledge, whether there is life anywhere else than on Earth actually allows more than two answers:
a) We know that life exists outside Earth.
b) We know that life only exists on Earth.
c) We do not know, if life exists outside Earth.
d) We do not know, if life only exists on Earth.

Only if we can securely answer the second question with a) or b), we can answer also the first question. Neither a) nor b) can be logically derived from any of the answers c) or d).

Moderator mode:
This discussion does not seem to go anywhere. If it continues to move in circles, I will consider locking this thread.

Dishmaster
(Moderator)

Zwirko and korben, have you heard the phrase, “Don’t count your chickens until they hatch”? How can you count something that has not been proven to exist? Well someone is implying that life elsewhere is a given that doesn’t require proof when they ask if it is common or rare. They can’t prove it exists, so they skip over that point. This is what I’ve tried to point out.

Ophiolite, they don’t give Nobel Prizes in science out to people for really, really, really believing something. They give it to the people who figure it out. Here’s how predictions work. When we recognize that things have an effect called mass, Higgs predicted that there might be a field that conducts mass to particles and a particle that communicates this mass to those particles. Now we are searching for an observation of this. What effect does life elsewhere answer? We’re supposed to accept that there might be life elsewhere because it answers the question, “Is there life elsewhere?” If we found fossils on Mars, this would be an effect that life elsewhere can exist. Then we could scientifically ask, “Maybe there is life elsewhere that we don’t know?” We haven’t done that, which doesn’t stop people from skipping over that part.
“…whether or not life exists elsewhere is wholly independent of our knowledge of that life.”
This always gets lots of applause at the forum for the Loch Ness Monster. Science is exactly about what we accept as knowledge. That which is not knowledge does not affect that which is. It’s a simple concept.
SETI was once part of NASA, until it got defunded. Now we are just looking for simple life forms…until the Astrobiology Department gets defunded. Actually, the Air Force is perfectly capable of doing all the commercial lifting of satellites without NASA (which would then get…you guessed it). But wait, NASA is going to the Moon and Mars (except for the funding thing). If you think that NASA is not worried about funding, then I guess you haven’t watched the news lately. Of course NASA is looking for a way to get public support to continue the exploration of space.

Dishmaster
e) We only know that life exists on Earth.

Predictions that do not have observational evidence remain predictions. Someone predicted that Big Foot, the Yeti and life elsewhere exist. They just have to prove this, which no one has.
I think that we can find out which basic processes turn atoms into simple molecules that can reproduce themselves. The smallest virus is only a few nanometers long. Kepler is searching for Earth-like planets. We’ve come a long way. However, let’s not get the cart a few parsecs in front of the horse.