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have they found anything?

Bill Thompson said:
Believing in ETI is a faith not a science.
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I'm not a "believer". I've stated my position clearly many times on this thread. That position is, "We don't know." I've been arguing against the position that the absence of evidence in this case is the evidence of absence.


Let me ask you this. Are YOU a scientist? What is your profession?
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Irrelevant. The logic stands on its own.


The logic to explain away Fermi's Paradox could just as easily be applied to the existance [sic] of Santa Claus.
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Wrong.

One could say "The North Pole is a huge area. It is absurd to think there is no Santa Claus there." just as logically as saying "There are billions of stars. It is absurd to think there is no other ETI near by".
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Straw man. (Generally when you have to make up quotes attributed to your opponent, you're engaging in an argument against a straw man position and not a real opponent.) I even numbered my points. Not one of them is this quote you just invented that no one said.

If you study logic you will see that it is not possible to prove a negative.
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Wrong.
The following argument:
P1. If P then not-Q.
P2. P.
C. Not-Q.​
is valid. If the two premises are valid it is sound. For example:
If it is raining out, I will not go to the game.
It is raining out.
I will not go to the game.​

I understand the statement, "You can't prove a negative" usually means something other than what you clearly claim it means.


Fermi did not have probes in mind. He had colonization. When he asked "where are they" he knew in his mathicaly genius mind that if life was common in the Universe, the galaxy should be colonized by now. That is it. That is the end of story. No probes, dude. Someone taught you a buchet of hog wash.
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I used probes because that's how many people today formulate it. The points I have to refute the argument work just as well with colonization. There is a false assumption (actually a false dichotomy) in saying either the entire galaxy should be colonized, or intelligent civilizations do not exist. And it's simple to demonstrate. We exist, and yet evidence of our existence is not ubiquitous in the galaxy.

Bill Thompson said:
We are late comers.
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How do you know that? At any rate, at best then you're simply arguing that long-lived intelligent civilizations substantially older than ours don't exist. (And even at that, it's a weak argument. It still relies on several assumptions any one of which might be false.)
If life like ours comes about frequently, the galaxy should be colonized by now.
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That doesn't follow. We are a "life like ours" and we haven't colonized the galaxy (and may never do so, for all we know).


It does not matter why they are not here and why we seem to be alone. THe point is that it seems we are.
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The point is that the fact that they are not here doesn't mean they don't exist. I can look into my back yard and see no sign of the existence of a dog. Does it follow that there are no dogs?


If life like ours statistically came about often in the universe, our galaxy should be colonized by now.
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You have no evidence to support this assumption. And yet your argument requires this assumption to be true.


Absence of evidence is evidence of absence in a court of law, in science, and in the scientific method.
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And that's why I specifically said "in this case". Absence of evidence where we have no good reason to expect that evidence is not evidence of absence. (See my no evidence of a dog in my backyard example.)
 
JoeTheJuggler said:
I'm not a "believer". I've stated my position clearly many times on this thread. That position is, "We don't know."
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You could just as logicaly insist that we do not know if Santa exists.

We know enough.

We know that we are here because of a series of very unlikely fortunate events.

We know that the universe is hostile to life.
 
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The following argument:
P1. If P then not-Q.
P2. P.
C. Not-Q.
​
is valid. If the two premises are valid it is sound. For example:
If it is raining out, I will not go to the game.
It is raining out.
I will not go to the game.
​
Click to expand...

This only proves that you do not get it.
"I will not go to the game" is not a negative just because the word "not" is in it.
It is not an example of a logical construct or proof.
"If I do not eat I will not trow up" can also be one of your examples. It is series of events, not a proof. You don't get it.

The logic to explain away Fermi's Paradox could just as easily be applied to the existance of Santa Claus.
JoeTheJuggler said:
Wrong.
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Explain yourself. Explain how your logic is any different. You say "absence of evidence is not evidence of absense". The same can be applied to Santa Claus.

You say that a negative can be proven. Take the challenge then. Prove that Santa does not exist.
 
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It is a fact though that lovers of S/F as I am also but not the far fetched stuff like Star Wars, do think that the universe is teeming with intelligent ETs.
But when it's considered the many almost miraculous events that led to intelligent life to form on this planet, it's doubtful that that is the case. There's no denying that given the almost infinite number of stars in the cosmos there's bound to be other Earths out there somewhere, but not anywhere near the number some people like Joe like think.
 
Bill Thompson said:
Believing in ETI is a faith not a science.

"Refuting" it would be like refuting Mormonism to a Mormon.
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Which is very easy. The fact that the mormon doesn't accept the refutation doesn't mean it's not easy to refute.
If you can refute what Joe presented, do so. If you can't, perhaps that shows something...

As technology advances and we learn more we find that the Universe is Life Hostile and we are just very lucky to have had Earth form the way it did. Fermi had a point. There is no paradox. People call it a paradox because they refuse to believe it.
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What do you mean when you say that universe is life hostile? Please be specific.

I remember you had some sort of elaborate and incorrect interpretation on what Fermi meant. So I am going to pass on reading your apologist postings supporting your faith.
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Did you read my post above? The fermi paradox is simply noting two aparently contradictory things to both be true.
The solution to the paradox is to realize that they either are not contradictory, or not both true.
You've chosen one of them and decided that it is not true, but there are many other ways to reconcile it with reality.

Why not start a discussion threat supporting the existance of Santa Claus. I am completely serious. The logic to explain away Fermi's Paradox could just as easily be applied to the existance of Santa Claus. One could say "The North Pole is a huge area. It is absurd to think there is no Santa Claus there." just as logically as saying "There are billions of stars. It is absurd to think there is no other ETI near by".
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The two are not in any way analogous.

There is absolutely no reason to believe that an impossible being would exist at the north pole, no matter how big it is.
On the other hand, intelligent life is possible. It is possible for it to come into existence without any outside interference. How frequently that happens is up for debate, but we know it does happen, because we have an example of it having happened once.
Whatever the likihood that life will evolve on any particular planet, the more planets there are, the more chance that it evolved on at least one of them, and the same is true of intelligent life.
All that is necessarily true. It doesn't mean that intelligent life is common, of course. If we want to look at how likely it is, we need to look closer, but there is certainly some probability greater than zero.
 
Bill Thompson said:
This only proves that you do not get it.
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ETA: revised response: That was a well reasoned and thoughtful reply to the points I made. Oh wait--no it wasn't.



"I will not go to the game" is not a negative just because the word "not" is in it.
It is not an example of a logical construct or proof.
"If I do not eat I will not trow up" can also be one of your examples. It is series of events, not a proof. You don't get it.
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ETA: Yes--the presence of the word "not" before a proposition is exactly what makes it a negative.
How about an even more trivial example:
P1. If a team loses a game, they do not win it.
P2. My team lost today.
C. My team did not win the game today.


You specifically made the claim that one cannot logically prove a negative. I pointed out that you're wrong, and you are.

I also pointed out that I understand that that's not what most people mean when they say "you can't prove a negative". (They actually mean it's difficult to prove the non-existence of something.)

As you pointed out wrt Santa Claus, in terms of science, we can indeed provide reasonable proof of the non-existence of something. (The example I like to use is the non-existence of phlogiston. By measuring the result of a combustion reaction with hydrogen, we get a result that is inconsistent with the theory of phlogiston, so we have effectively proven the non-existence of phlogiston.)


Explain yourself. Explain how your logic is any different. You say "absence of evidence is not evidence of absense". The same can be applied to Santa Claus.

You say that a negative can be proven. Take the challenge then. Prove that Santa does not exist.
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Predictions made by the Santa Claus theory repeatedly fail to come true.

At any rate, I'm not asking you or anyone to prove the non-existence of ETIs. I'm merely pointing out that the evidence or lack of evidence available to us does not support that conclusion--not even tentatively. The fact is, we don't know.

Again, the best analogy is if I glance in my backyard and look for evidence of the existence of dogs. I see none. Is it reasonable to conclude that dogs do not exist? Or even that they're scarce? About all you can conclude is that evidence of the existence of dogs is not ubiquitous. It's wrong to assume that either evidence of the existence of dogs ought be ubiquitous or dogs either don't exist or are scarce. The fact is, based solely on a glance in the backyard, I don't know whether dogs exist and if they do how frequent they are.

Oh--to make the analogy more correct, I should specify that there is a dog inside my house sitting by my feet. So I know that at least one dog exists. (Unlike anything similar to the Santa Claus analogy.)

ETA: And wrt to the existence of ETIs, they are really just Intelligent Civilizations that are not ours. We already know ours exists, so we know that at least one intelligent civilization exists. So your idea of not proving a negative is moot. We've already disproven the negative. (While it might be difficult to prove that no black swans exist, it is easy to prove that they exist by providing one example.)
 
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Roboramma said:
Which is very easy. The fact that the mormon doesn't accept the refutation doesn't mean it's not easy to refute.
If you can refute what Joe presented, do so. If you can't, perhaps that shows something...

What do you mean when you say that universe is life hostile? Please be specific.
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G.D.!! Just google, "Refuges for Live in A Hostile Universe"
I will put a copy online and send you a book list.

http://www.google.com/search?hl=en&...ns_inline&ct=unquoted-query-link&ved=0CAYQgwM

JoeTheJuggler said:
Of interest to this thread: a "super-earth" where liquid water is possible:
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Even our Earth ought not have life apart from microbial. Pointing to other earths and claiming that intelligent life must be abundant shows you do not know Earth's history.

ETA: Yes--the presence of the word "not" before a proposition is exactly what makes it a negative.
How about an even more trivial example:
P1. If a team loses a game, they do not win it.
P2. My team lost today.
C. My team did not win the game today.
Click to expand...

That is a case statment, not a proof.

Now, take up my challenge and prove that Santa does not exist.
 
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Bill Thompson said:
Even our Earth ought not have life apart from microbial. Pointing to other earths and claiming that intelligent life must be abundant shows you do not know Earth's history.
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Do tell, Bill. I'd certainly like to know what in Earth's history necessarily rules out the the fact that we shouldn't have multicellular life here. I'm all ears.
 
Bill Thompson said:
Even our Earth ought not have life apart from microbial.
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Science doesn't deal with "ought" for issues like these.

ETA: And it's statements like these that make me think rare Earthers are arguing a Creationist/ID agenda.
 
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Bill Thompson said:
That is a case statment, not a proof.
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http://www.thefreedictionary.com/logical+proof

I dunno, but I think maybe you're confusing computer programming with logical proof.

Another example:

If phlogiston existed, a sample that is burned would always weigh less after burning than it does before.
When you burn a sample of hydrogen gas, you get a sample of water that weighs more than the hydrogen gas did.
Phlogiston doesn't exist.

It's the same thing. Also the same with Santa Claus. If Santa Claus were true, predictions made by the Santa Claus theory would come true consistently, but they don't. For example, if Santa Claus were real, we predict sleigh tracks on the roof and gifts appearing under the tree that no normal human put there.

So far, no prediction that would come true only if ETIs didn't exist has come true. There is no reason to rule out the possibility of the existence of ETIs.

Again, the analogy you keep ignoring about the existence of extra-my-house dogs based on a quick glance at my backyard is appropriate.
 
Joe, do you spend a lot of time here because you are knowledgeable about this subject and you want to inform us, or is there some other reason?

Assuming that you are knowledgeable, can you answer these 10 questions and tell me if you have seen the three articles I have listed below?

  1. Why is the moon essential for our existence?
  2. What is what Dana Mackenzie calls "The Big Splat" and why is it important to understanding how our Earth-Moon set up is uncommon in the Universe?
  3. Why is Jupiter essential for our existence?
  4. Why is a system of plate tectonics vital for the development of life forms?
  5. How did early microbial life shape the world and set the stage for later life forms and what is that uncommon in the universe?
  6. How did early plant life shape the world and set the stage for later life forms and what is that uncommon in the universe?
  7. What effects did mass extinctions have on evolution?
  8. What effect did the "Snow Ball Earth" have on the evolution of life on Earth?
  9. What does the fact that "Snow Ball Earth" existed have on the liklihood life being common in the universe?
  10. What does human psychology have to do with the fact that so many people believe in extra-terrestrial life?
Galactic Chemical Evolution: Implications for the Existence of Habitable Planets.
Virginia Trimble in Extraterrestrials: Where Are They?
Edited by M. H. Hart and B. Zuckerman. Cambridge University Press, 1995.
http://astro.wsu.edu/hclee/pasa_review_GCE.pdf

An Estimate of the Age Distribution of Terrestrial Planets in the
Universe: Quantifying Metallicity as a Selection Effect.
Charles H. Lineweaver in Icarus, Vol. 151, No. 2, pages 307–313; June 1,
2001. Preprint available at astro-ph/0012399
http://arxiv.org/abs/astro-ph/0012399
http://arxiv.org/PS_cache/astro-ph/pdf/0012/0012399v2.pdf

The Galactic Habitable Zone: Galactic Chemical Evolution. Guillermo
Gonzalez, Donald Brownlee and Peter D. Ward in Icarus, Vol. 152, No. 1,
pages 185–200; July 1, 2001. Preprint available at astro-ph/0103165
http://arxiv.org/abs/astro-ph/0103165
http://arxiv.org/PS_cache/astro-ph/pdf/0103/0103165v1.pdf
 
JoeTheJuggler said:
Science doesn't deal with "ought" for issues like these.

ETA: And it's statements like these that make me think rare Earthers are arguing a Creationist/ID agenda.
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It is all a matter of simple statistics. If something happens rarely, the odds are low that it happens commonly.
 
shadron said:
Do tell, Bill. I'd certainly like to know what in Earth's history necessarily rules out the the fact that we shouldn't have multicellular life here. I'm all ears.
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Ice reflects light. The sea does not as much. Each one hundred thousand years we have an ice age and each one is a roll of the dice. If the ice sheet advances past where St. Louis is, we have crossed the point of no return.

The idea of "snow ball earth" was discovered by a Russian scientist and Carl Segan when they crunched the numbers of what an all out nuclear war would do to the earth. If the sun was blocked out and if temperatures went down far enough for long enough we would hit a tipping point.

The idea of snow ball earth was made before it was discovered that it had once really happened.

Also, it should be like that right now if not for a stroke of luck.

It was dumb luck that volcanic activity broke us from the "snow ball earth" according the discovery channel episode. If we did not win that proverbial lottery, we would be locked in ice.

Like I said, ice reflects light. The sea does not as much. Each one hundred thousand years we have an ice age and each one is a roll of the dice. Glacier evidence on the equator now proves that during one of those ice ages, the ice sheet advanced past the point of no return and the advancing ice sheet form the north and the south met at the equator.

Luckily we have tectonic plates. Luckily they just happened to make enough volcanoes all at the same time (after about 30 million years of being an ice planet, as I recall) and broke the snowball earth.

The Earth was young then. Somehow microbial life existed and survived but more complex life would be impossible to evolve.
 
JoeTheJuggler said:
It's the same thing. Also the same with Santa Claus. If Santa Claus were true, predictions made by the Santa Claus theory would come true consistently, but they don't. For example, if Santa Claus were real, we predict sleigh tracks on the roof and gifts appearing under the tree that no normal human put there.
Click to expand...

The same holds true for Fermi's observation. If the rise of intelligent life was common in the universe, they should be EVERYWHERE and proof of their existance would be unavoidable.
 
JoeTheJuggler said:
It's the same thing. Also the same with Santa Claus. If Santa Claus were true, predictions made by the Santa Claus theory would come true consistently, but they don't. For example, if Santa Claus were real, we predict sleigh tracks on the roof and gifts appearing under the tree that no normal human put there.
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Finally we are getting somewhere. Santa made the tracks disappear.
Predictions? Santa does not follow your schedule, he has his own schedule. The ways of Santa are mysterious.

You say that if you make a prediction about Santa and it does not come true, then he does not exist? Dude, EVERY prediction of if and when we would get a signal from SETI@HOME has been wrong!!
 
Bill, everything you're raising has been answered in this thread already.

You're entirely too hostile for conversation.
 
Bill Thompson said:
Joe, I ask you to provide proof that Santa does not exist. I am still waiting.
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Not to step on Joe's toes here, but the entire fable of Santa is well know in its origins and can be traced through all the numerous permutations that finally arrived at the current fable. Also, specific statements regarding Santa are patently false. We have explored the surface and underside of the North Pole quite extensivelly, and found no workshop. The stories indicate that one should be there, but it's not, so the story itself is false.

After that, people invoking magic or whatnot to desperately try to keep the story alive are grasping at straws.

Kind of reminds me of other stories that people cling to.

So far, no prediction or statement about ETI having any measurable effect on us has been made, thus the jury is still out.
 
LarianLeQuella said:
Not to step on Joe's toes here, but the entire fable of Santa is well know in its origins and can be traced through all the numerous permutations that finally arrived at the current fable. Also, specific statements regarding Santa are patently false. We have explored the surface and underside of the North Pole quite extensivelly, and found no workshop. The stories indicate that one should be there, but it's not, so the story itself is false.
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That is not a proof. Prove that he does not exist. Saying that there are fables that can be traced back regarding Santa does not prove that he does not exist.

ET and ETI and ETL all have fables too that date back longer than the fables regarding Santa.

By the way, people thought Mountain Gorillas were fables too once. Saying that something is based on fables does not prove that it does not exist.

Also saying that "Santa is not there" is not proof that he does not exist!! You could fly over the North Pole and say "see, he is not there" to someone and they could easily just say that Santa knew you were coming and he is hiding.
 
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arthwollipot said:
Wait - is Bill actually asking someone to prove the nonexistence of something?
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No, he's suggesting that those who think that the probability of extraterrestrial intelligence elsewhere in our galaxy is high are doing so.

Basically he says, "I can't prove that ETIs don't exist just like you can't prove that there's no Santa Claus, but the lack of evidence for them suggests that they don't exist, just like the lack of evidence for Santa Claus suggests that he doesn't exist."

Of course, there's a problem with that. The problem with Santa Claus is that we are lacking evidence for his existence that we would expect to have if he existed. That's not the case with ETIs.
 
Bill Thompson said:
Joe, I ask you to provide proof that Santa does not exist. I am still waiting.

You say that there is no Santa because there is no evidence.
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We know there is no Santa because there is no evidence where we would expect to find it.

I remember when I was about 5 years old, I wondered if Santa was real. I knew it was possible that my parents were simply putting the presents there for me, so I decided that I'd have to wait until I was older and had moved out on my own to see if Santa brought presents for me.
Of course, long before that I had other evidence of Santa's non-existence, but even as a five year old I could think of a test for the existence of not of Santa.

Regarding ETI, what particular test are you suggesting has been done and found that the evidence showed that ETI doesn't exist?
 
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Roboramma said:
No, he's suggesting that those who think that the probability of extraterrestrial intelligence elsewhere in our galaxy is high are doing so.

Basically he says, "I can't prove that ETIs don't exist just like you can't prove that there's no Santa Claus, but the lack of evidence for them suggests that they don't exist, just like the lack of evidence for Santa Claus suggests that he doesn't exist."

Of course, there's a problem with that. The problem with Santa Claus is that we are lacking evidence for his existence that we would expect to have if he existed. That's not the case with ETIs.
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Thanks for summarising. I've only been skim-reading this thread for some time now.
 
Bill Thompson said:
Ice reflects light. The sea does not as much. Each one hundred thousand years we have an ice age and each one is a roll of the dice. If the ice sheet advances past where St. Louis is, we have crossed the point of no return.

The idea of "snow ball earth" was discovered by a Russian scientist and Carl Segan when they crunched the numbers of what an all out nuclear war would do to the earth. If the sun was blocked out and if temperatures went down far enough for long enough we would hit a tipping point.

The idea of snow ball earth was made before it was discovered that it had once really happened.

Also, it should be like that right now if not for a stroke of luck.

It was dumb luck that volcanic activity broke us from the "snow ball earth" according the discovery channel episode. If we did not win that proverbial lottery, we would be locked in ice.

Like I said, ice reflects light. The sea does not as much. Each one hundred thousand years we have an ice age and each one is a roll of the dice. Glacier evidence on the equator now proves that during one of those ice ages, the ice sheet advanced past the point of no return and the advancing ice sheet form the north and the south met at the equator.

Luckily we have tectonic plates. Luckily they just happened to make enough volcanoes all at the same time (after about 30 million years of being an ice planet, as I recall) and broke the snowball earth.

The Earth was young then. Somehow microbial life existed and survived but more complex life would be impossible to evolve.
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OK, fine. Without plate tectonics we would not have multi-cellular life. Then, what do you suppose is the probability that a planet of our size will be sufficiently tectonically active to escape a snowball event?

That would be a function of our internal temperature, I presume. Our internal temperature depends on several things:

- The raw size of the planet, providing sufficient materials described in the next three points and a sufficiently insulative mantle blanket to promote an active interior.
- The initial kinetic/potential energy available to convert to heat, which, if our size is constant would be roughly the same.
- The proportion of iron available, which, while falling towards the core in the "iron catastrophe", also gives up its potential energy into heat.
- The amount of uranium, thorium and other radioactive species/isotopes available to decay and this give up heat.

I don't see how tectonics would be a low probability occurrence for any given rocky planet of our general size placed within a liquid water domain. Both the freezing and the melting appear to be limited run-away thermal processes, and therefore inevitable if the triggering conditions are available, therefore I don't see why the snowball earth would be an ultimate peril for multi-cellular life. Indeed, it would have to be held in abeyance for perhaps 50 million years, that could well be enough to start multicellular creatures. It was only about 40 million years from the end of the Marinoan snowball to the first appearance of multicellular creatures (sponges, jellyfish, nidarians) in the Ediacarian period.
 
The arguments put forward of why ET is not yet here is weak in a galaxy that is up to 13 billion years old. Every possibility is possible in such a vast galaxy with possibly up to 400 billion stars. At least some of these stars would have sprouted a life bearing planet perhaps billions of years ago. And at least some of a nearby advanced planet perhaps a million years more advanced than us should by now have discovered us. They haven't which could mean we are alone in this part of the galaxy at least, or we are one of the first.
 
amb said:
The arguments put forward of why ET is not yet here is weak in a galaxy that is up to 13 billion years old. Every possibility is possible in such a vast galaxy with possibly up to 400 billion stars.
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Every possibility is possible? Well, yeah.

But impossible things aren't. And things which are improbable enough remain improbable even after many billions of years.

It really is possible that interstellar travel simply doesn't happen. It might be technically impossible (there was a thread recently in which quite a few people argued just that).

At least some of these stars would have sprouted a life bearing planet perhaps billions of years ago. And at least some of a nearby advanced planet perhaps a million years more advanced than us should by now have discovered us.
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That's the part that you need to justify. What makes you think that they would necessarily have the means and the motivation do to so?
 
Roboramma said:
It really is possible that interstellar travel simply doesn't happen. It might be technically impossible (there was a thread recently in which quite a few people argued just that).
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How could it be technically impossible when it happens naturally? Over the time frames involved the natural velocities of comets and the stars themselves are sufficient for a lot of migration.
 
Roboramma said:
No, he's suggesting that those who think that the probability of extraterrestrial intelligence elsewhere in our galaxy is high are doing so.

Basically he says, "I can't prove that ETIs don't exist just like you can't prove that there's no Santa Claus, but the lack of evidence for them suggests that they don't exist, just like the lack of evidence for Santa Claus suggests that he doesn't exist."
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Kind of. I pointed out that in this case (existence of ETIs) the absence of evidence is not evidence of absence, to which Bill said that you can't logically prove a negative. I pointed out that as the statement was worded, it's wrong and gave several examples of logical proofs of negatives. I even indicated that I was aware that what he probably meant was that it's difficult to prove the non-existence of something. (The "there are no black swans" issue--it's easy enough to disprove, but how do you prove it?)


Of course, there's a problem with that. The problem with Santa Claus is that we are lacking evidence for his existence that we would expect to have if he existed. That's not the case with ETIs.
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Exactly. The argument for the non-existence of ETIs based on lack of evidence assumes that existence of an ETI must be ubiquitous in the galaxy. There are any number of reasons why they might not be.

It's not that we have to prove which if any of these (the numbered points I've made on this thread for nearly a year now) is true. It's enough that any one of them is possible to show that the evidence of ETIs (if they exist) need not be ubiquitous. Thus, the absence of evidence in this case is not evidence of absence.

The analogy I've been making is this situation: I've got a dog here in the house next to me, but when I glance out the window to my back yard, I don't see any evidence of extra-in-my-house dogs. It's absurd to claim therefore that there are no dogs anywhere else in the world other than the one here in my house.

Proving the non-existence of Santa Claus or phlogiston (surely we have!) is beside the point anyway. No one is claiming you've got to have proof of the non-existence of ETIs.

I'm just pointing out that the argument for the non-existence of ETIs based on the lack of evidence is not valid. Again, we are an intelligent civilization, and evidence of our existence (whether self-replicating probes, galaxy-wide colonization or whatever) is not ubiquitous. Another civilization contemplating our existence and using your reasoning would incorrectly conclude that we do not exist. Yet here we are.

Also the Rare Earth arguments have been thoroughly debunked, and the connection of these arguments to Creationist/ID proponents has been shown. That's why the backward thinking that every aspect of conditions here MUST be prerequisite to complex or intelligent life is so similar to Creationist/ID and Fine Tuning arguments.
 
Roboramma said:
It really is possible that interstellar travel simply doesn't happen. It might be technically impossible (there was a thread recently in which quite a few people argued just that).
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Also, one of my numbered points, it might be technically possible but for other reasons something no civilization ever ends up making use of. (Or technically possible but something no civilization ever discovers.)

Again, the argument amb and Bill have been pushing rests on the assumption that it's not only technically possible but absolutely inevitable that an intelligent civilization would discover it and be motivated to exploit the technology and make evidence of their existence ubiquitous throughout the galaxy.

There are all sorts of possible explanations why this assumption doesn't have to be true. (And for the argument to work, the assumption must be true.)

It could be technologically impossible (and rather than address FTL, interstellar travel, self-replicating probes or ANY specific formulation of Fermi's Paradox, I'm referring to the very general proposition that an ETI would make evidence of its existence ubiquitous in the galaxy).

It could be possible, but no civilization lasts long enough to discover it.

It could be possible and civilizations could last long enough, but it could be that civilizations at that level always (or even usually) lack the motivation to do it.

It could be possible and civilizations could last long enough and have the motivation, but the technology could be economically impractical.

It could be that all those things are in place, but evidence doesn't last long enough to remain ubiquitous throughout the galaxy for any length of time. (In my dog analogy, what if a dog had just walked through my back yard a few minutes before I looked out? What if a civilization had colonized all of the universe, but then abandoned some bits of it a mere 100 million years ago, so that our corner of it shows no sign of their presence? What if a probe had passed near or even through our solar system a mere 1000 years ago?)
 
shadron said:
OK, fine. Without plate tectonics we would not have multi-cellular life. Then, what do you suppose is the probability that a planet of our size will be sufficiently tectonically active to escape a snowball event?
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Almost nill.

Seems like a pretty unlikely balancing act to me.

A reoccurring inferno like Venus or a dead dirt ball like Mars I think would be more common. Earth has threaded a proverbial needle by astronomically absurd good luck.

It is not just plate tectonics. It is plate tectonics and them all making big enough volcanoes all at the same time to break the freeze. Otherwise, we would be a snowball planet today. That was winning the lottery in a big way. And I do not think such a thing has happened since. So it is perfect timing as well.

We owe our existance to the fact that there are so many stars. Otherwise, the odds would not be in favor for us to exist.
 
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Roboramma said:
We know there is no Santa because there is no evidence where we would expect to find it.
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That does not make any sense. We are talking about Santa.

But If you are drawing a parallel with ETI, then we are alone for all practical purposes. Because there are less and less places we find that are life-friendly the more we learn about the Universe.
 
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