Question: Should I Believe in Aliens?

[RoshanBBQ]

So here is the setup: I know a bunch of people who think it is the dumbest thing ever or absolutely ridiculous to say, "I don't believe aliens exist."

What is your stance on that question?

Here is what I currently know:
+I have seen no evidence for alien existence

Therefore, I don't believe in aliens. Now, if there is some evidence, I would change my tune. That is partly why I'm making this thread, to make sure there is no evidence as I have encountered.

Here are some common arguments for alien existence:

+Drakes equation
Giving names to unknown probabilities does not mean we know them. Don't make me laugh.

+"Pyramids! Therefore, aliens visited us, and by extension, aliens exist (since non-existent beings cannot visit us).
First off, arguments of this flavor basically say, "We have no idea how [...]. Therefore, we do know how [...]." Ridiculous! The conclusion and premise are exact 180s of each other. As a demonstration of the insanity of this argument, consider the possibility of ultra-advanced humans coexisting with "tribal" humans, oh, for example how Americans coexist with small tribes in the middle of the Amazon jungle.

+"Space is SOOO huge! Therefore, aliens must exist."
This is a funny one. To this, I ask, "What is the probability of life spontaneously generating per unit of space"?" Without that probability, the number of trials for spontaneous generation mean nothing. In other words, (unknown probability of life generation per unit volume)*(known volume) = unknown expected value of instances of generated life.

+"Space is INFINITE. Therefore, aliens must exist."
This one tickles me more than the prior. It is extra misleading, because it is a valid argument. Given any nonzero probability of spontaneous generation of life and an infinite number of trials, life must have come about elsewhere. However, the premise that the universe is infinite is not known to be true as of now! So the conclusion based on it is dubious. I would go so far as to believe that premise is unprovable since it would take an infinite observation to verify something is infinite.

Please help me not be an idiot. I have way too many people telling me I am. Thank you! I have even seen astrophysicists and astronomers on T.V. (albeit possibly sensationalists) say "OF COURSE there are aliens out there." When they say this, it makes me wonder how they know so steadfastly.

 

[Arifz]

So here is the setup: I know a bunch of people who think it is the dumbest thing ever or absolutely ridiculous to say, "I don't believe aliens exist."

What is your stance on that question?

Here is what I currently know:
+I have seen no evidence for alien existence

Therefore, I don't believe in aliens. Now, if there is some evidence, I would change my tune. That is partly why I'm making this thread, to make sure there is no evidence as I have encountered.

Here are some common arguments for alien existence:

+Drakes equation
Giving names to unknown probabilities does not mean we know them. Don't make me laugh.

+"Pyramids! Therefore, aliens visited us, and by extension, aliens exist (since non-existent beings cannot visit us).
First off, arguments of this flavor basically say, "We have no idea how [...]. Therefore, we do know how [...]." Ridiculous! The conclusion and premise are exact 180s of each other. As a demonstration of the insanity of this argument, consider the possibility of ultra-advanced humans coexisting with "tribal" humans, oh, for example how Americans coexist with small tribes in the middle of the Amazon jungle.

+"Space is SOOO huge! Therefore, aliens must exist."
This is a funny one. To this, I ask, "What is the probability of life spontaneously generating per unit of space"?" Without that probability, the number of trials for spontaneous generation mean nothing. In other words, (unknown probability of life generation per unit volume)*(known volume) = unknown expected value of instances of generated life.

+"Space is INFINITE. Therefore, aliens must exist."
This one tickles me more than the prior. It is extra misleading, because it is a valid argument. Given any nonzero probability of spontaneous generation of life and an infinite number of trials, life must have come about elsewhere. However, the premise that the universe is infinite is not known to be true as of now! So the conclusion based on it is dubious. I would go so far as to believe that premise is unprovable since it would take an infinite observation to verify something is infinite.

Please help me not be an idiot. I have way too many people telling me I am. Thank you! I have even seen astrophysicists and astronomers on T.V. (albeit possibly sensationalists) say "OF COURSE there are aliens out there." When they say this, it makes me wonder how they know so steadfastly.

What is the probability of finding H2O on other planets? Zero?? life must exist if water is found, that's why NASA is spending billions of dollars just to find water on other planets.

 

[Astronuc]

So here is the setup: I know a bunch of people who think it is the dumbest thing ever or absolutely ridiculous to say, "I don't believe aliens exist."

What is your stance on that question?

Here is what I currently know:
+I have seen no evidence for alien existence

Therefore, I don't believe in aliens. Now, if there is some evidence, I would change my tune. That is partly why I'm making this thread, to make sure there is no evidence as I have encountered.

Here are some common arguments for alien existence:

+Drakes equation
Giving names to unknown probabilities does not mean we know them. Don't make me laugh.

+"Pyramids! Therefore, aliens visited us, and by extension, aliens exist (since non-existent beings cannot visit us).
First off, arguments of this flavor basically say, "We have no idea how [...]. Therefore, we do know how [...]." Ridiculous! The conclusion and premise are exact 180s of each other. As a demonstration of the insanity of this argument, consider the possibility of ultra-advanced humans coexisting with "tribal" humans, oh, for example how Americans coexist with small tribes in the middle of the Amazon jungle.

+"Space is SOOO huge! Therefore, aliens must exist."
This is a funny one. To this, I ask, "What is the probability of life spontaneously generating per unit of space"?" Without that probability, the number of trials for spontaneous generation mean nothing. In other words, (unknown probability of life generation per unit volume)*(known volume) = unknown expected value of instances of generated life.

+"Space is INFINITE. Therefore, aliens must exist."
This one tickles me more than the prior. It is extra misleading, because it is a valid argument. Given any nonzero probability of spontaneous generation of life and an infinite number of trials, life must have come about elsewhere. However, the premise that the universe is infinite is not known to be true as of now! So the conclusion based on it is dubious. I would go so far as to believe that premise is unprovable since it would take an infinite observation to verify something is infinite.

Please help me not be an idiot. I have way too many people telling me I am. Thank you! I have even seen astrophysicists and astronomers on T.V. (albeit possibly sensationalists) say "OF COURSE there are aliens out there." When they say this, it makes me wonder how they know so steadfastly.

In the absence of direct evidence, we don't know if aliens exist or not. Even if they did, it doesn't necessarily imply that aliens would be humanoid.

We do know that there are other planets that have oxygen and water, and possible the other elements/compounds that are requisite for life similar to that found on earth. However, that only indicates a potential.

It would be amazing to find life on another planet in this galaxy, but most stars are beyond our reach. Life in other galaxies is even more beyond our reach.

 

[Jobrag]

That Aliens exist somewhere in the Universe probability approaching one, chances of communicating with said Aliens probability approaching zero, that Aliens have visited Earth probability zero.

 

[phinds]

That Aliens exist somewhere in the Universe probability approaching one, chances of communicating with said Aliens probability approaching zero, that Aliens have visited Earth probability zero.

+1 on that

 

[Whovian]

What is the probability of finding H2O on other planets? Zero?? life must exist if water is found, that's why NASA is spending billions of dollars just to find water on other planets.

Ummmm ... ? Why must life exist if water is found? Water's necessary for life, but that doesn't mean other requirements are met, and even if all requirements are met, that doesn't mean life will exist.

Anyways, I have some suspicion that they might not be primarily water as most Earth species are if they exist.

+"Space is SOOO huge! Therefore, aliens must exist."
This is a funny one. To this, I ask, "What is the probability of life spontaneously generating per unit of space"?" Without that probability, the number of trials for spontaneous generation mean nothing. In other words, (unknown probability of life generation per unit volume)*(known volume) = unknown expected value of instances of generated life.

This is almost my argument. You did point out that there is no way to know (which I agree with), but due to the sheer size of the Universe, any probability other than a ridiculously small one of life being on a random planet will likely result in at least a few planets with life. I do, however, highly doubt they were ever on this planet. Note that I do not claim aliens exist, I do claim there is a good possibility they exist.

At the moment, we have no evidence for aliens' existence (History Channel's Ancient Aliens basically just takes a few things we don't think ancient cultures had the technology to do, not all of which are valid, that they clearly did, and say it was aliens. Or just say "there's an uncanny resemblance between the Ark of the Covenant and a Nuclear Reactor." Hogswash.), but the only evidence we have for their nonexistence is the fact that we haven't found any. So it's all a bit uncertain. Those that claim that they definitely do exist have absolutely ridiculous arguments, and those that claim they don't just have to say "we haven't found any yet." So one must just come up with one's own opinion on how likely we are to find alien life and hope they're right.

 

[phinds]

It would be amazing to find life on another planet in this galaxy, but most stars are beyond our reach. Life in other galaxies is even more beyond our reach.

I assume you mean only that it would be amazing for us to IDENTIFY such life, not amazing that it would exist. Given the billions of stars in the Milky way, I'd say it would be quite amazing if there were no life other than us.

 

[RoshanBBQ]

It looks like it's happening here too. Can you guys tell me why you believe there are aliens? Astronuc seems to be on my page, though, that there is no evidence of alien existence.

 

[Whovian]

It looks like it's happening here too. Can you guys tell me why you believe there are aliens? Astronuc seems to be on my page, though, that there is no evidence of alien existence.

I'd say us believing there are aliens is too bold a statement, we believe that there are quite probably aliens.

 

[mfb]

Well, our knowledge is quite limited:

We know that there are a lot of planets, and some planets have conditions similar to Earth (similar star, similar distance, mass and chemical composition). The estimates about the numbers are quite rough today, but that should get improved within the next decade.
The big unknown number is the probability that life evolves on planets which can support it.


However, there is an anthropic argument that some other planets should have developed intelligent (!) life. Let's assume 10^10 earth-like planets in the observable universe - this is some orders of magnitude below the real number, as observations showed.

Now, what could the probability that intelligent life on a specific earth-like planet developes?
...
10^(-20)?
10^(-19)?
...
10^(-1)?
~1?

We don't know. However, I would expect that 10^(-10) (one planet with intelligent life) is not 100.000 times more likely than 10^(-5) (10^5 planets with intelligent life). Therefore, if we follow bayesian statistics for a while, the probability of being one of 10^5 intelligent species is higher than the probability of being the only one.

 

[Jobrag]

"It looks like it's happening here too. Can you guys tell me why you believe there are aliens? Astronuc seems to be on my page, though, that there is no evidence of alien existence."

There is no direct evidence of alien existence, however there is growing evidence that Earth like planets exist in abundance in our galaxy making it an almost certainty that they exist in other galaxies.
We have managed to produce ribonucleotides in the laboratory by simulating conditions found in on a primitive Earth the fact that this was possible suggests that the basic building blocks of life are relatively easy to make making life in other parts of the Universe far more likely.
The combination of a great number of possible life supporting planets plus the apparent ease at which the basis of life can be created makes the probability of alien life very very high.

 

[Drakkith]

This is easy to answer. We do not know if there are aliens out there. Since we do not know, we can only say that we either believe that they exist, or do not believe that they exist. Whether you believe aliens exist or not will depend on your own reasons.

So, in the end, YOU will have to decide whether you believe in aliens or not. You already have most of the most common reasons for believing in them.

Edit: Perhaps a third option is needed. Believing they exist, not believing they exist, and neither believing nor disbelieving.

 

[mfb]

Since we do not know, we can only say that we either believe that they exist, or do not believe that they exist.

This is not a binary decision. You can think of it as more or less probable (with a lot of freedom to choose). Recent discoveries of exoplanets shift it towards the "more probable" region, and an observation of extraterrestrial life would change the whole situation, of course.

 

[Drakkith]

This is not a binary decision. You can think of it as more or less probable (with a lot of freedom to choose). Recent discoveries of exoplanets shift it towards the "more probable" region, and an observation of extraterrestrial life would change the whole situation, of course.

You are correct. I will amend my previous post with a third option. Neither believing nor disbelieving.

 

[Vagn]

+"Space is SOOO huge! Therefore, aliens must exist."
This is a funny one. To this, I ask, "What is the probability of life spontaneously generating per unit of space"?" Without that probability, the number of trials for spontaneous generation mean nothing. In other words, (unknown probability of life generation per unit volume)*(known volume) = unknown expected value of instances of generated life.

This part is based on the fact that life on Earth appeared not long after the late heavy bombardment, with evidence that life was present 100-500 million years after the end of it, about 3.9-3.5 billion years ago.
There's something called the argument to the mean, where we can say that if we have one instance of something, then it is most likely to be close to the average value.
Using this we can say that if the time taken for life to appear on Earth is typical, then the probability of life arising must by necessity be quite high, in the right circumstances.
Hence if the probability of life arising is large, then there probably is extra-terrestrial life elsewhere in the universe, as it seems that Earth-like planets are common, as we have begun to see them, despite only just being able to detect Earth-sized planets.

There are problems with this conclusion though, one of which is the Rare Earth Hypothesis, which says that the conditions for life to occur are rare. Another issue is we don't know whether assuming the argument to the mean is valid in this case as we only have one example of life occurring.

 

[RoshanBBQ]

Well, our knowledge is quite limited:

We know that there are a lot of planets, and some planets have conditions similar to Earth (similar star, similar distance, mass and chemical composition). The estimates about the numbers are quite rough today, but that should get improved within the next decade.
The big unknown number is the probability that life evolves on planets which can support it.However, there is an anthropic argument that some other planets should have developed intelligent (!) life. Let's assume 10^10 earth-like planets in the observable universe - this is some orders of magnitude below the real number, as observations showed.

Now, what could the probability that intelligent life on a specific earth-like planet developes?
...
10^(-20)?
10^(-19)?
...
10^(-1)?
~1?

We don't know. However, I would expect that 10^(-10) (one planet with intelligent life) is not 100.000 times more likely than 10^(-5) (10^5 planets with intelligent life). Therefore, if we follow bayesian statistics for a while, the probability of being one of 10^5 intelligent species is higher than the probability of being the only one.

Your argument should have stopped there. And as for your probability argument, you're going to have to state it a bit more clearly, perhaps symbolically at first. There is no reason to disguise a simple probability relation by calling upon an arbitrary name without even defining the probabilities associated in that relation clearly.

"It looks like it's happening here too. Can you guys tell me why you believe there are aliens? Astronuc seems to be on my page, though, that there is no evidence of alien existence."

There is no direct evidence of alien existence, however there is growing evidence that Earth like planets exist in abundance in our galaxy making it an almost certainty that they exist in other galaxies.
We have managed to produce ribonucleotides in the laboratory by simulating conditions found in on a primitive Earth the fact that this was possible suggests that the basic building blocks of life are relatively easy to make making life in other parts of the Universe far more likely.
The combination of a great number of possible life supporting planets plus the apparent ease at which the basis of life can be created makes the probability of alien life very very high.

The in bold is quite remarkable. You state in the same conjoined sentence that there is no evidence for A and that A is almost certainly true.

Now, from what I can extract, you are stating our ability to manufacture ribonucleotides on planets 'like ours' combined with an abundance of planets 'like ours' means alien life almost certainly exists. However, you haven't cited any source saying how likely ribonucleotides spontaneously generate, or how likely it is that once they spawn, life will follow (which is sort of an important step in the equation... because correct me if I'm wrong, but ribonucleotides are not living).

This is easy to answer. We do not know if there are aliens out there. Since we do not know, we can only say that we either believe that they exist, or do not believe that they exist. Whether you believe aliens exist or not will depend on your own reasons.

So, in the end, YOU will have to decide whether you believe in aliens or not. You already have most of the most common reasons for believing in them.

Edit: Perhaps a third option is needed. Believing they exist, not believing they exist, and neither believing nor disbelieving.

The in bold is a plain fact about anything -- that is, we can believe it or not believe it due to our own reasons. The qualifier to your observation ("Since we don't know...") is an unnecessary partition of the set of all possibilities. That is, it applies equally to things we "do know."

The first thing you stated was you sizing up how much evidence there currently is, which you admitted was naught. Hence, you should (as I do) not believe in alien existence.

This is not a binary decision. You can think of it as more or less probable (with a lot of freedom to choose). Recent discoveries of exoplanets shift it towards the "more probable" region, and an observation of extraterrestrial life would change the whole situation, of course.

You have made an awful mistake by playing this word game. What you are stating is a complete falsehood. You basically side-stepped the question. Let me explain:

There are four possibilities:
1.) "I believe aliens exist" & "I believe it is likely aliens exist"
2.) "I believe aliens exist" & "I do not believe it is likely aliens exist"
3.) "I do not believe aliens exist" & "I do believe it is likely aliens exist"
4.) "I do not believe aliens exist" & "I do not believe it is likely aliens exist"

In other words, the belief of whether aliens exist and of whether it is likely aliens exist are two different beliefs. It is unimportant that they are related (as in, no one should take on case 2). The proof that they are different is that case 3 is perfectly logical for some circumstances. We are talking about the former whereas you have pulled a red herring by bringing in the latter.

And despite what you say, belief is binary. You cannot neither believe nor not believe something. The union of these possibilities contains all.

This part is based on the fact that life on Earth appeared not long after the late heavy bombardment, with evidence that life was present 100-500 million years after the end of it, about 3.9-3.5 billion years ago.
There's something called the argument to the mean, where we can say that if we have one instance of something, then it is most likely to be close to the average value.
Using this we can say that if the time taken for life to appear on Earth is typical, then the probability of life arising must by necessity be quite high, in the right circumstances.
Hence if the probability of life arising is large, then there probably is extra-terrestrial life elsewhere in the universe, as it seems that Earth-like planets are common, as we have begun to see them, despite only just being able to detect Earth-sized planets.

There are problems with this conclusion though, one of which is the Rare Earth Hypothesis, which says that the conditions for life to occur are rare. Another issue is we don't know whether assuming the argument to the mean is valid in this case as we only have one example of life occurring.

To paraphrase, you stated, "A is a typical argument, but it is not a good argument (in bold)." Can I infer you are implying we should not believe in alien existence?

 

[Constantin]

Not long ago we thought the Earth was the center of the Universe, and the Sun was revolving around it. It also made perfect sense for most people, while the fact the Earth was just a planet seemed ridiculous.

Actually, until very recently, just years ago, most people didn't even believe planets are a normal occurrence outside of our own solar system. Until technology evolved enough to find such planets around other stars.

 

[rbj]

i'm pretty sure that ET aliens have never visited this planet (although it makes for and interesting premise in science fiction), simply because of the known distance between stars and the known speed of light and the known facts regarding special relativity. but i also think it unlikely that there are no other planets even in our galaxy that have never supported life. and once any kind of life emerges, i doubt that, once you give it a billion years or two (and assuming their sun doesn't burn out or go supernova on them), that more sophisticated life will not evolve from it.

in other words, i am picking up on this:

+"Space is SOOO huge! Therefore, aliens must exist."
This is a funny one.

ask yourself what is the probability, knowing that life can emerge somewhere (because it has, at least at one place) in the galaxy, what is the probability that it has never emerged anywhere else in the galaxy. 100 billion stars out there. leaving our sun out of it (because we know what the answer is for that star), if the probability of life emerging on some planet around any particular star is very small, but not zero since we exist, then the probability of life not emerging on a planet around any particular star is not quite equal to 1. so it's 0.9999999999999999999999999999999999 or something like that. now multiply that probability times itself 100 billion times and see how close to 1 it remains and if it is still so likely that no where (else) life has ever emerged.

it doesn't take a very large probability coming out of the Drake equation for it to be more likely than not that life has emerged somewhere else at some time in the past or the future. not terribly likely to be within 10 or 100 lightyears from us. and not terribly likely that they would become intelligent enough to send out radio signals that would be detected by us in the sliver of time our species would be listening. and very unlikely that we'll ever detect evidence of their presence since we will not measure any radio signal from them if they live halfway across the Milky Way (they would have to be within 100 lightyears, unless they send Morse code by detonating very large H-bombs in space - they got to compete with the radiant output of stars).

 

[thorium1010]

This thread is about whether I should believe in aliens. It's not about whether argument for or against that belief resembles religious debate or whether such debates should be against the rules of the forum.

I think the word belief would be very difficult to justify in science, given the nature of science that it should be verified by evidence. science grows stronger in confidence when evidence grows stronger. Ex : Higgs boson - evidence for its existence grows stronger.Belief has very little use in science.

 

[twofish-quant]

What's wrong with saying "I don't know"?

I remember there was a conversation in which someone was asking me whether I thought there were aliens or not, and they had enormous difficulty accepting the fact that "I don't know, and since I don't know, I don't have an opinion."

 

[Astronuc]

A reminder: Please do not interject religion into the discussion.

A couple of definitions of belief:

Conviction of the truth of some statement or the reality of some being or phenomenon especially when based on examination of evidence or in the absence of evidence. (Merriam-Webster)

An opinion or conviction, especially one expressing confidence in the truth or existence of something not immediately susceptible to rigorous proof. (derived from Dictionary.com)


Belief is a starting point. One can certainly conject that life might exist elsewhere. Then it is a matter of discovering the evidence to support that conjecture (or belief) through the scientific process.

There is an active field, astrobiology, which is the study of the origin, evolution, distribution, and future of extraterrestrial life.
http://en.wikipedia.org/wiki/Astrobiology
http://astrobiology.nasa.gov/
http://www.astrobio.net/ = Astrobiology Magazine

 

[RoshanBBQ]

What's wrong with saying "I don't know"?

I remember there was a conversation in which someone was asking me whether I thought there were aliens or not, and they had enormous difficulty accepting the fact that "I don't know, and since I don't know, I don't have an opinion."

From what I understand, the lack of belief that aliens exist is a prerequisite to saying "I don't know." "I don't know" is a combination of a lack of belief that aliens exist as well as a lack of belief that aliens do not exist.

A reminder: Please do not interject religion into the discussion.

A couple of definitions of belief:

Conviction of the truth of some statement or the reality of some being or phenomenon especially when based on examination of evidence or in the absence of evidence. (Merriam-Webster)

An opinion or conviction, especially one expressing confidence in the truth or existence of something not immediately susceptible to rigorous proof. (derived from Dictionary.com)Belief is a starting point. One can certainly conject that life might exist elsewhere. Then it is a matter of discovering the evidence to support that conjecture (or belief) through the scientific process.

There is an active field, astrobiology, which is the study of the origin, evolution, distribution, and future of extraterrestrial life.
http://en.wikipedia.org/wiki/Astrobiology
http://astrobiology.nasa.gov/
http://www.astrobio.net/ = Astrobiology Magazine

This is a mighty point. I haven't even defined what belief is.

As far as this discussion is concerned, if I have a belief in something, I consider it true. However, that does not mean a lack of belief in something indicates belief in a falsehood. It simply means at that time, you do not consider it true. By this definition, anything of which I am unaware also has a lack of belief by me. As an example, the Romans did not believe in general relativity (since they didn't even know what it is, and it is impossible to think something is true without knowledge of it). However, they also did not believe it was false (since again, they had no knowledge of it).

It is interesting to note that the definition of belief can be reworked to include belief itself, which might be problematic. If I "consider it true", an equivalent statement is to say "I have the belief that it is true." So then, belief in it is having the belief it is true. In other words, my definition becomes "belief in A is belief in A". I don't know what else to do.

i'm pretty sure that ET aliens have never visited this planet (although it makes for and interesting premise in science fiction), simply because of the known distance between stars and the known speed of light and the known facts regarding special relativity. but i also think it unlikely that there are no other planets even in our galaxy that have never supported life. and once any kind of life emerges, i doubt that, once you give it a billion years or two (and assuming their sun doesn't burn out or go supernova on them), that more sophisticated life will not evolve from it.

in other words, i am picking up on this:
ask yourself what is the probability, knowing that life can emerge somewhere (because it has, at least at one place) in the galaxy, what is the probability that it has never emerged anywhere else in the galaxy. 100 billion stars out there. leaving our sun out of it (because we know what the answer is for that star), if the probability of life emerging on some planet around any particular star is very small, but not zero since we exist, then the probability of life not emerging on a planet around any particular star is not quite equal to 1. so it's 0.9999999999999999999999999999999999 or something like that. now multiply that probability times itself 100 billion times and see how close to 1 it remains and if it is still so likely that no where (else) life has ever emerged.

it doesn't take a very large probability coming out of the Drake equation for it to be more likely than not that life has emerged somewhere else at some time in the past or the future. not terribly likely to be within 10 or 100 lightyears from us. and not terribly likely that they would become intelligent enough to send out radio signals that would be detected by us in the sliver of time our species would be listening. and very unlikely that we'll ever detect evidence of their presence since we will not measure any radio signal from them if they live halfway across the Milky Way (they would have to be within 100 lightyears, unless they send Morse code by detonating very large H-bombs in space - they got to compete with the radiant output of stars).

How on Earth are you coming up with these probabilities?

 

[Whovian]

How on Earth are you coming up with these probabilities?

I think that was just a guess, for the sake of example.

 

[Travis_King]

And despite what you say, belief is binary. You cannot neither believe nor not believe something. The union of these possibilities contains all.

I neither believe you are wearing a red shirt, nor do I disbelieve it. I simply do not know. Belief, in matters of uncertainty, doesn't even come into play unless you want it to.

As for the topic at hand. As far as I'm concerned you'd have to be crazy to think that life doesn't or hasn't existed elsewhere at some point in the history of the universe.

 

[jpopplewell]

When in doubt, I ALWAYS defer to Ancient Alien Theorists! ;)

 

[mfb]

Your argument should have stopped there. And as for your probability argument, you're going to have to state it a bit more clearly, perhaps symbolically at first. There is no reason to disguise a simple probability relation by calling upon an arbitrary name without even defining the probabilities associated in that relation clearly.
[...]
The in bold is quite remarkable. You state in the same conjoined sentence that there is no evidence for A and that A is almost certainly true.

I rolled dice 1000 times. Do you think I got at least one 6?
You have no evidence for this. In addition, as I already did it in the past, I either rolled at least one 6 or I did not. However, you can assign a high confidence to the event that I rolled at least one 6.Your arguments show that we cannot be certain that life exists on other planets. So what? We all know this.
You cannot be sure about anything anyway.
Should you believe that I am human? Probably. Can you be sure that I am? No, I could be an AI.
Maybe Earth does not exist, and your brain lives in some simulated environment? Maybe your state of mind is the result of a sufficiently advanced computer program in a universe with completely different laws of nature?
You can assign a really low probability to that, but these events are possible.

In other words, the belief of whether aliens exist and of whether it is likely aliens exist are two different beliefs.

If the former does not follow from the latter, it is called religion. In that case, it is pointless to discuss it. It is possible to estimate the probability, everything else does not give any interesting results in a discussion.

I don't see circumstances where '3.) "I do not believe aliens exist" & "I do believe it is likely aliens exist' is "perfectly logical". But I think we have a different opinion what a "belief" is:

And despite what you say, belief is binary. You cannot neither believe nor not believe something. The union of these possibilities contains all.

Roll a fair die, and I'll believe that face x was rolled with 1/6, for all 6 faces.
If I think something has a probability really close to 1, I might neglect the difference for practical reasons. Therefore, I am sure that Earth exists and orbits the sun - the probability (given the information I have) that this is wrong is negligible. But for cases where the probability is somewhere in between, I don't "believe one of the sides". I keep both in mind, with relative probabilities (which can be highly subjective).

 

[RoshanBBQ]

I think that was just a guess, for the sake of example.

Well, if it's just an arbitrary guess, what good is it?

I neither believe you are wearing a red shirt, nor do I disbelieve it. I simply do not know. Belief, in matters of uncertainty, doesn't even come into play unless you want it to.

As for the topic at hand. As far as I'm concerned you'd have to be crazy to think that life doesn't or hasn't existed elsewhere at some point in the history of the universe.

So your first portion describes the state of "I don't know" in "matters of uncertainty".

First off, everything real is a matter of uncertainty. That is where induction comes into play. For example, if I get an AIDS test that comes back positive, I will induce that I have AIDS; in other words, I will believe I have AIDS since it is so certain despite the small probability of the test's failure. And I will not beat around the bush by saying "I don't know if I have AIDS since this is a matter of uncertainty" if a sexual partner asks me whether I have AIDS

Now, on to your definition. You state IDK with respect to A is a combination of a lack of belief in A and lack of disbelief in A. In other words, IDK is a stronger case of "I do not believe in A". All people who IDK with respect to A do not believe in A. So you have basically stated a vacuous truth with regards to our current discussion. The thread is not about whether you should IDK with respect to the existence of aliens. It is whether you should believe they exist. If your stance is IDK, it naturally follows you also have the stance you should not believe they exist (It is part of the definition as you have stated - and as I stated to 2fishquant).

But on to the text in bold: That is a funny way to argue! You are insulting me (ad hominem fallacy) and bringing up no evidence.

All in all, your post was fully rhetorical with no actual contribution to the argument. Thank you.

When in doubt, I ALWAYS defer to Ancient Alien Theorists! ;)

What has the history channel become?!

I rolled dice 1000 times. Do you think I got at least one 6?
You have no evidence for this. In addition, as I already did it in the past, I either rolled at least one 6 or I did not. However, you can assign a high confidence to the event that I rolled at least one 6.

In this circumstance, I inductively believe you rolled at least one six. In other words, I believe you rolled at least one six. I take the statement "He rolled at least one six" as true. The evidence is overwhelming. Take a look at the AIDS example I gave in this same post to someone else. Belief is binary. I must either believe you rolled at least one six or not believe you rolled at least one six.

Your arguments show that we cannot be certain that life exists on other planets. So what? We all know this.
You cannot be sure about anything anyway.
Should you believe that I am human? Probably. Can you be sure that I am? No, I could be an AI.
Maybe Earth does not exist, and your brain lives in some simulated environment? Maybe your state of mind is the result of a sufficiently advanced computer program in a universe with completely different laws of nature?
You can assign a really low probability to that, but these events are possible.If the former does not follow from the latter, it is called religion. In that case, it is pointless to discuss it. It is possible to estimate the probability, everything else does not give any interesting results in a discussion.

You are simply stating vacuous truths regarding the nature of induction. I am not asking how induction works. I am asking for something that is inductively appealing to alter my belief on whether aliens exist. As of now, there is no evidence from which to induce, so I do not believe aliens exist.

I don't see circumstances where '3.) "I do not believe aliens exist" & "I do believe it is likely aliens exist' is "perfectly logical". But I think we have a different opinion what a "belief" is:

For the sake of demonstrating how this can be logical, let us assume we calculate the probability of alien existence elsewhere to be 65%. In this case, I would not find the evidence inductively strong enough to alter my belief on alien existence. However, I would still believe it is likely they exist.

Roll a fair die, and I'll believe that face x was rolled with 1/6, for all 6 faces.
If I think something has a probability really close to 1, I might neglect the difference for practical reasons. Therefore, I am sure that Earth exists and orbits the sun - the probability (given the information I have) that this is wrong is negligible. But for cases where the probability is somewhere in between, I don't "believe one of the sides". I keep both in mind, with relative probabilities (which can be highly subjective).

Belief is binary. In this circumstance, the probabilities are not convincing enough. You cannot comfortably induce anything. Hence, you should not believe any particular face showed. Whether you should believe a face showed with probability 1/6 is a different statement entirely. You are basically pulling a straw man fallacy by restructuring the statement at hand for which we must evaluate its truth. My statement is of the type "This is true" whereas yours is of the type "A is true with probability B". They are entirely different.

 

[Chronos]

It seems highly improbable we are the only intelligent beings in the universe. It also appears even more improbable a civilization can master space travel. The energy demands are just too enormous. It would take about 20 kg of anti matter to send a ship to alpha centauri, and that is a lot of anti matter for a mere 4 light years.

 

[Travis_King]

And I will not beat around the bush by saying "I don't know if I have AIDS since this is a matter of uncertainty" if a sexual partner asks me whether I have AIDS.

This is quite obviously a ridiculous reduction of what I said...

I didn't make any mention of uncertainties, I simply made the point that there are instances where "belief" doesn't come into play. I don't believe that you are wearing a red shirt, but neither do I not believe it.

This was an aside to some of the arguments about belief that were going on in this thread, and is unrelated to my personal stance. Which is, as you might have guessed, that I do believe that life exists elsewhere in the universe. (though I do not go as far as to say that it has "visited" us, or anything like that)

If your stance is IDK, it naturally follows you also have the stance you should not believe they exist (It is part of the definition as you have stated - and as I stated to 2fishquant).

I don't accept this, not only because it's an ought, but because it isn't sound. I don't know states only that you do not have sound justification for basing your belief or disbelief. This problem arises because the choice we are faced with is itself binary. If you do not believe aliens exist, then you necessarily believe that they do not. This is the only reason the issue between "belief" and "non-belief" seems so binary as well. Because in this case, non-belief is equivalent to belief-in-the-contrary.

This is why I said that IDK is a valid stance in this case. non-belief, here requires justification just as belief does. IDK isn't saying "I don't believe it at the moment", it is saying, "maybe they do, maybe they don't." A little belief, a little non-belief.

But on to the text in bold: That is a funny way to argue! You are insulting me (ad hominem fallacy) and bringing up no evidence.

...well I didn't really insult you, I just think that, frankly, it's a little ridiculous to think that life is so rare. And it's not an ad hominem, really. I didn't use it to form an argument; I was just stating my stance.

In this circumstance, I inductively believe you rolled at least one six. In other words, I believe you rolled at least one six. I take the statement "He rolled at least one six" as true. The evidence is overwhelming. Take a look at the AIDS example I gave in this same post to someone else. Belief is binary. I must either believe you rolled at least one six or not believe you rolled at least one six.

No, you mustn't. Nowhere is it written that you have to believe anything...if someone asks you, "Do you think this guy rolled a six after all these trials?"
You don't have to rack your brain, you can just say, "I don't know." That isn't not believing he rolled a six; it's not giving credence to the question.

 

[RoshanBBQ]

This is quite obviously a ridiculous reduction of what I said...

I didn't make any mention of uncertainties, I simply made the point that there are instances where "belief" doesn't come into play. I don't believe that you are wearing a red shirt, but neither do I not believe it.

This was an aside to some of the arguments about belief that were going on in this thread, and is unrelated to my personal stance. Which is, as you might have guessed, that I do believe that life exists elsewhere in the universe. (though I do not go as far as to say that it has "visited" us, or anything like that)

You are the king of saying nothing with a whole bunch of words. I don't even know what all of this has to do with anything.

I don't accept this, not only because it's an ought, but because it isn't sound. I don't know states only that you do not have sound justification for basing your belief or disbelief. This problem arises because the choice we are faced with is itself binary. If you do not believe aliens exist, then you necessarily believe that they do not. This is the only reason the issue between "belief" and "non-belief" seems so binary as well. Because in this case, non-belief is equivalent to belief-in-the-contrary.

This is why I said that IDK is a valid stance in this case. non-belief, here requires justification just as belief does. IDK isn't saying "I don't believe it at the moment", it is saying, "maybe they do, maybe they don't." A little belief, a little non-belief.

Saying you do not believe something is not the same as belief in the complement. This is a fundamental, common misunderstanding, regarding the nature of belief.

Definitions:
belief in A means a person thinks A is true. Note, if you lack a belief in A, this just means you do not label it true. This does not imply you are labeling it false.
Disbelief in A means a person thinks A is false. Note, if you lack a disbelief in A, that just means you do not label it false. That does not imply you are labeling it true.

When someone does not know in regards to A, he has a lack of belief in A and a lack of disbelief in A. That is, he does not label A true nor false. In other words, when someone does not know in regards to A, he does not believe in A by necessity. Bringing up the stricter criteria of "I don't know" is unrelated to the topic at hand since I asked specifically about whether to believe in aliens.

...well I didn't really insult you, I just think that, frankly, it's a little ridiculous to think that life is so rare. And it's not an ad hominem, really. I didn't use it to form an argument; I was just stating my stance.

You accused people who lack belief in alien existence of insanity. You then followed it up with the blind declaration that aliens most certainly exist without any evidence.

No, you mustn't. Nowhere is it written that you have to believe anything...if someone asks you, "Do you think this guy rolled a six after all these trials?"
You don't have to rack your brain, you can just say, "I don't know." That isn't not believing he rolled a six; it's not giving credence to the question.

You are using a straw man fallacy. I never said someone has to have belief in something. I said in regards to each statement, they must either believe or not believe in it. Given your unfair rephrasing of my argument, the rest of this portion of your post becomes meaningless.

 

[mfb]

For the sake of demonstrating how this can be logical, let us assume we calculate the probability of alien existence elsewhere to be 65%. In this case, I would not find the evidence inductively strong enough to alter my belief on alien existence. However, I would still believe it is likely they exist.

In this context, I would not call 65% a "high probability". I thought about something like 99% or more.

I don't like your discussion style. It is not about aliens, it is about how you dislike other posts. In addition, you attack the way other posters use words, if it does not fit in your way to use them.


I think one should assign a high probability that life exists on other planets in the observable universe (and beyond). I don't care about the religious aspects of belief in this context.

 

[jreelawg]

When someone does not know in regards to A, he has a lack of belief in A and a lack of disbelief in A. That is, he does not label A true nor false. In other words, when someone does not know in regards to A, he does not believe in A by necessity. Bringing up the stricter criteria of "I don't know" is unrelated to the topic at hand since I asked specifically about whether to believe in aliens.

Your use of the word belief, may be correct, but not consistent with that of most people in the context.

So you position more simply put is, I don't know. I think if you just said that in the first place, the people your referring to wouldn't have thought your position was ridiculous.

All this talk about probability is ridiculous in my opinion. I don't think many people know what probability is or how to calculate it. It is impossible to know the probability of aliens existing, or visiting Earth given the evidence we have to base this discussion on.

 

[jreelawg]

I could say that I don't believe physics forums will exist in the morning. Would you take it that I think that will be the case, or just that there is some possibility of it? I think there certainly is the possibility physics forums could be wiped out no matter how unlikely. So I guess anyone who believes that physics forums won't be wiped out in the morning is full of it.

 

[Bikersquirrel]

I have high doubts about whether we will ever identify alien life. Are there any aliens in the universe right now? Maybe, maybe not. I would not however say there has never been aliens nor that there will never be aliens. There just might not be any right now (according to our perspective of course) :)

 

[Travis_King]

No, to his credit, RoshanBBQ did say that his point has nothign to do with uncertainty. I agree with that, at least. Belief doesn't require certainty, that's why it isn't called knowledge.

You can recognize the potential for your belief to be wrong, and yet still have that belief, i.e. you can recognize that physics forums might exist in the morning, and still believe that they will not. The degree to which your belief clings to reality, and the probability of it being true describe how rational your belief is.

(1) I believe X will happen
(2) I do not believe X will happen
(3) I believe X will not happen
(4) I do not believe X will not happen (epistemically different than 1)

So you can have 1&3, 2&3, 2&4
These are three logically consistent and epistemically different combinations of stances on this matter. Thus, the issue is not binary.

As far as probabilities actually go, I agree with jreelawg. We cannot know the probability of life existing, or the probability of abiogenesis. But we know that it is non-zero, and that life is pretty darn resilient and can survive in incredibly hostile environments. We also know that there is a limited number of different kinds of stuff in this universe, and the stuff that makes up life (at least as we know it) are extremely abundant. Does the evidence suggest that life exists elsewhere? That's up for debate. But it surely doesn't pit against that notion.

 

[rbj]

ask yourself what is the probability, knowing that life can emerge somewhere (because it has, at least at one place) in the galaxy, what is the probability that it has never emerged anywhere else in the galaxy. 100 billion stars out there. leaving our sun out of it (because we know what the answer is for that star), if the probability of life emerging on some planet around any particular star is very small, but not zero since we exist, then the probability of life not emerging on a planet around any particular star is not quite equal to 1. so it's 0.9999999999999999999999999999999999 or something like that. now multiply that probability times itself 100 billion times and see how close to 1 it remains and if it is still so likely that no where (else) life has ever emerged.

it doesn't take a very large probability coming out of the Drake equation for it to be more likely than not that life has emerged somewhere else at some time in the past or the future. not terribly likely to be within 10 or 100 lightyears from us. and not terribly likely that they would become intelligent enough to send out radio signals that would be detected by us in the sliver of time our species would be listening. and very unlikely that we'll ever detect evidence of their presence since we will not measure any radio signal from them if they live halfway across the Milky Way (they would have to be within 100 lightyears, unless they send Morse code by detonating very large H-bombs in space - they got to compete with the radiant output of stars).

How on Earth are you coming up with these probabilities

I think that was just a guess, for the sake of example

Well, if it's just an arbitrary guess, what good is it?

it's good for framing questions. or re-framing questions. would you like me to do that?

so let's say that if you pick any star you see in the Milky Way at random (but leave out our sun, since we know what the outcome is for that particular star).

so the Drake equation (copied from Wikipedia) is:

N = R^{\ast} \cdot f_p \cdot n_e \cdot f_{\ell} \cdot f_i \cdot f_c \cdot L

where:

N = the number of civilizations in our galaxy with which communication might be possible;

and

R^* = the average rate of star formation per year in the Milky Way
f_p = the fraction of those stars that have planets
n_e = the average number of planets that can potentially support life per star that has planets
f_ℓ = the fraction of the above that actually go on to develop life at some point
f_i = the fraction of the above that actually go on to develop intelligent life
f_c = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into spaceso, just to keep the discussion simpler, i want to fold a bunch of probabilities together into a single probability:

p = f_p \cdot n_e \cdot f_{\ell} \cdot f_i

that appears to me to be about the right expression for the probability that if you pick any old star out there, there will be intelligent life at some time around it. let's all agree that this probability is very, very small. like, for the sake of illustration, it's 0.0000000000000000000000000000000001. i just pulled the number out of my butt.

this means that the probability that, if you pick some star outa the sky at random, the probability that no life has ever existed on any planet around that star is 1-p = 0.9999999999999999999999999999999999 which is less than 1.

now, how many times can you multiply (1-p) times itself to get below 1/2? that is when the likelihood that there are no ETs out there is less than the likelihood that there are. since there are 100 billion stars in the Milky Way, even if p is that small, the likelihood that there are ETs somewhere in the Milky Way still comes out pretty close to 1.

so then invert the question and ask what must p be in order to get the total probability to 1/2?

(1-p)^{100000000000} = \frac{1}{2}

p doesn't have to be very large for it to be more likely there are ETs than not.

 

[RoshanBBQ]

Your use of the word belief, may be correct, but not consistent with that of most people in the context.

So you position more simply put is, I don't know. I think if you just said that in the first place, the people your referring to wouldn't have thought your position was ridiculous.

All this talk about probability is ridiculous in my opinion. I don't think many people know what probability is or how to calculate it. It is impossible to know the probability of aliens existing, or visiting Earth given the evidence we have to base this discussion on.

My position is I don't know, which means I do not believe aliens exist. As for the in bold portion, that is largely what I suspect, which is why I have the position I have. It is also why I opened up this thread -- to see if my concept of the current state of evidence on the topic was right.

I could say that I don't believe physics forums will exist in the morning. Would you take it that I think that will be the case, or just that there is some possibility of it? I think there certainly is the possibility physics forums could be wiped out no matter how unlikely. So I guess anyone who believes that physics forums won't be wiped out in the morning is full of it.

We have to be careful with your sentence structure. What exactly is "I don't believe physics forums will exist tomorrow" saying? It is the same as saying, "I lack the belief that the physics forums will exist tomorrow." In other words, you do not assign truth to the statement, "The physics forums will exist tomorrow."

Now, as far as I can tell, no probability enters into this equation. I would think you're saying exactly what you're saying. You do not assign truth to that statement. But I would be quite assuming to think you would assign false to the statement, "The physics will exist tomorrow." That is to say, you could be in a state of "I don't know."

So to answer your question in bold, you haven't stated any belief -- so I don't take it you believe in any particular thing with probability or no probability. I take it you lack belief in something.

No, to his credit, RoshanBBQ did say that his point has nothign to do with uncertainty. I agree with that, at least. Belief doesn't require certainty, that's why it isn't called knowledge.

You can recognize the potential for your belief to be wrong, and yet still have that belief, i.e. you can recognize that physics forums might exist in the morning, and still believe that they will not. The degree to which your belief clings to reality, and the probability of it being true describe how rational your belief is.

(1) I believe X will happen
(2) I do not believe X will happen
(3) I believe X will not happen
(4) I do not believe X will not happen (epistemically different than 1)

So you can have 1&3, 2&3, 2&4
These are three logically consistent and epistemically different combinations of stances on this matter. Thus, the issue is not binary.

As far as probabilities actually go, I agree with jreelawg. We cannot know the probability of life existing, or the probability of abiogenesis. But we know that it is non-zero, and that life is pretty darn resilient and can survive in incredibly hostile environments. We also know that there is a limited number of different kinds of stuff in this universe, and the stuff that makes up life (at least as we know it) are extremely abundant. Does the evidence suggest that life exists elsewhere? That's up for debate. But it surely doesn't pit against that notion.

Now I'm starting to like your posts. However, there is a small problem I detect. Belief with respect to a single statement is binary -- you can either belief it or lack belief in it. The reason you came up with 4 statements of belief (or lack of belief) is you analyzed two statements from each two statements (the binary ones of which I speak) derived. The two statements were: "X will happen" and "X will not happen." More concisely, X happening and X not happening are all possibilities. So you analyzed two statements: "X" and "Not X (The complement of X)".

As for the in bold, I agree we don't have the evidence as you put it. The only deviation I have is it's not up for debate. I feel ironclad with my lack of belief in alien existence.

it's good for framing questions. or re-framing questions. would you like me to do that?

so let's say that if you pick any star you see in the Milky Way at random (but leave out our sun, since we know what the outcome is for that particular star).

so the Drake equation (copied from Wikipedia) is:

N = R^{\ast} \cdot f_p \cdot n_e \cdot f_{\ell} \cdot f_i \cdot f_c \cdot L

where:

N = the number of civilizations in our galaxy with which communication might be possible;

and

R^* = the average rate of star formation per year in the Milky Way
f_p = the fraction of those stars that have planets
n_e = the average number of planets that can potentially support life per star that has planets
f_ℓ = the fraction of the above that actually go on to develop life at some point
f_i = the fraction of the above that actually go on to develop intelligent life
f_c = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space


so, just to keep the discussion simpler, i want to fold a bunch of probabilities together into a single probability:

p = f_p \cdot n_e \cdot f_{\ell} \cdot f_i

that appears to me to be about the right expression for the probability that if you pick any old star out there, there will be intelligent life at some time around it. let's all agree that this probability is very, very small. like, for the sake of illustration, it's 0.0000000000000000000000000000000001. i just pulled the number out of my butt.

this means that the probability that, if you pick some star outa the sky at random, the probability that no life has ever existed on any planet around that star is 1-p = 0.9999999999999999999999999999999999 which is less than 1.

now, how many times can you multiply (1-p) times itself to get below 1/2? that is when the likelihood that there are no ETs out there is less than the likelihood that there are. since there are 100 billion stars in the Milky Way, even if p is that small, the likelihood that there are ETs somewhere in the Milky Way still comes out pretty close to 1.

so then invert the question and ask what must p be in order to get the total probability to 1/2?

(1-p)^{100000000000} = \frac{1}{2}

p doesn't have to be very large for it to be more likely there are ETs than not.

You're going to have to be a bit more reasonable than this. It seems the discussion of aliens is the only place some scientists accept completely made up numbers as evidence.

 

[rbj]

You're going to have to be a bit more reasonable than this. It seems the discussion of aliens is the only place some scientists accept completely made up numbers as evidence.

you need to stop blowing smoke.

what's unreasonable? that the probability of no life circling either stars A or B is the product of the probability of no life circling star A times the probability of no life circling star B? is that unreasonable?

what number did i make up? that there are 100 billion stars in the Milky Way?

BBQ, do you know how to do math? in case the answer is "yes", here is a number i didn't just make up (i was going to let you calculate it but you didn't rise to the challenge):

7 × 10^-12

that's 0.000000000007 , a helluva lot bigger than the number i pulled outa my butt.

if you pick at random any old star you see in the sky, if it is more probable than 0.000000000007 that around that star ET lives (or had lived or will live) and is looking up at his sky and asking the same question about you that you are asking about him/her/it, if the the probability is at least that, then it is more likely than not that there is (or was or will be) ET circling around some star in the galaxy.

can you do the math and tell us why?

 

[RoshanBBQ]

you need to stop blowing smoke.

what's unreasonable? that the probability of no life circling either stars A or B is the product of the probability of no life circling star A times the probability of no life circling star B? is that unreasonable?

what number did i make up? that there are 100 billion stars in the Milky Way?

BBQ, do you know how to do math? in case the answer is "yes", here is a number i didn't just make up (i was going to let you calculate it but you didn't rise to the challenge):

7 × 10^-12

that's 0.000000000007 , a helluva lot bigger than the number i pulled outa my butt.

if you pick at random any old star you see in the sky, if it is more probable than 0.000000000007 that around that star ET lives (or had lived or will live) and is looking up at his sky and asking the same question about you that you are asking about him/her/it, if the the probability is at least that, then it is more likely than not that there is (or was or will be) ET circling around some star in the galaxy.

can you do the math and tell us why?

That number doesn't matter, because we don't know what the actual number is. There is no reason to believe the number is anywhere close to what it needs to be to satisfy your 1/2 equation. The probability of life around a star could be 10^-500 for example. I'm also not well-versed enough on the spontaneous creation of life to suppose the events per sun are independent. Basically, we know almost nothing about the phenomena since we cannot observe it or recreate it.

 

[Ophiolite]

I'm also not well-versed enough on the spontaneous creation of life to suppose the events per sun are independent.

Exactly. And the key point is that no one is that well versed, although some believe they are.

We may suspect certain values apply in the Drake equation. We may think that if the value differs radically from the one we suppose that we should be utterly amazed. We may ague eloquently as to why the value will fall with in a give range, but - as you say - we do not know. Therefore any estimates based upon wholly uncertain numbers are interesting, but they are meaningless - other than as a thought experiment.

 

[jreelawg]

That number doesn't matter, because we don't know what the actual number is. There is no reason to believe the number is anywhere close to what it needs to be to satisfy your 1/2 equation. The probability of life around a star could be 10^-500 for example. I'm also not well-versed enough on the spontaneous creation of life to suppose the events per sun are independent. Basically, we know almost nothing about the phenomena since we cannot observe it or recreate it.

The point is that the universe is very, very large. There are so many places other than Earth in which there could be life. To assume Earth to be so rare as to be the only place where life has begun seams very ridiculous. We have found that on earth, life thrives all over the place. There is life deep deep underground, there is life at the bottom of the Ocean living without the need for sunlight. There is life living in extreme cold, in extreme heat. Life is very adaptable.

I think the question to ask, is why would there not be life in other places? Is it that Earth is an unimaginably rare place. I don't think so, do you? Why?

Rather than dancing around the semantics of what it means to believe; why not hold a position worth discussing? Do you suspect there exists life in other solar systems? How strongly do you suspect it? If not, how strongly do you suspect life does not exist?

 

[rbj]

if you pick at random any old star you see in the sky, if it is more probable than 0.000000000007 that around that star ET lives (or had lived or will live) and is looking up at his sky and asking the same question about you that you are asking about him/her/it, if the the probability is at least that, then it is more likely than not that there is (or was or will be) ET circling around some star in the galaxy.

That number doesn't matter, because we don't know what the actual number is. There is no reason to believe the number is anywhere close to what it needs to be to satisfy your 1/2 equation. The probability of life around a star could be 10^-500 for example. I'm also not well-versed enough on the spontaneous creation of life to suppose the events per sun are independent. Basically, we know almost nothing about the phenomena since we cannot observe it or recreate it.

Exactly. And the key point is that no one is that well versed, although some believe they are.

We may suspect certain values apply in the Drake equation. We may think that if the value differs radically from the one we suppose that we should be utterly amazed. We may ague eloquently as to why the value will fall with in a give range, but - as you say - we do not know. Therefore any estimates based upon wholly uncertain numbers are interesting, but they are meaningless - other than as a thought experiment.

i think that astrobiologists would disagree. take a different component of the Drake equation f_p and n_e. 2 or 3 decades ago they had no experimental evidence other than our own solar system what the values of those might be. now we see exoplanets all over the place and it begins to look like f_p might be nearly unity and n_e might be 1.6 . we, as a species with intelligence, are starting to get a grip on those parameters. there are several scientists that work in abiogenesis that have both discovered life on Earth that has no need of sunlight (it only requires water and an energy gradient in order to exist) and they have discovered evidence of H₂O on other planets and moons in our solar system. they are working out the means to see if H₂O on certain exoplanets will be detectable in the light reflected from them. there is the Miller–Urey experiment that demonstrates the possibility of the emergence of organic molecules out of inorganic precursors.

so, maybe what you need to think about is the Strong Anthropic Principle. i don't know if i buy into it or not (everybody buys into the Weak Anthropic Principle, since it is essentially a tautology). essentially, the SAP says that, if you shuffle an honest deck of cards and draw a single card offa the top, that eventually (if you repeat this experiment and give it a few billion years), you will draw the Ace of Spades. even if there are a helluva lot more cards in the deck than 52, eventually the "life-giving" card will be drawn, unless there is something physical that prevents it. but if you have the right kind of "petri dish" on the right kind of planet circling the right kind of sun, give it a billion years or so and the SAP says that eventually the right combination of molecules (and they have an idea what this combination may be) will fall together, chemical reactions will occur, organic molecules will emerge, complexity will increase, proteins, metabolism and self-replication emerge, etc. the probability of this cannot be zero because it happened here. as long as that Ace of Spades lies in the deck somewhere, eventually we will run the experiment and it will pop out.

i don't know why you think that the Copernican principle or Mediocrity principle is untrue. we got past the denial of that obviousness hundreds of years ago.

 

[RoshanBBQ]

The point is that the universe is very, very large. There are so many places other than Earth in which there could be life. To assume Earth to be so rare as to be the only place where life has begun seams very ridiculous. We have found that on earth, life thrives all over the place. There is life deep deep underground, there is life at the bottom of the Ocean living without the need for sunlight. There is life living in extreme cold, in extreme heat. Life is very adaptable.

I think the question to ask, is why would there not be life in other places? Is it that Earth is an unimaginably rare place. I don't think so, do you? Why?

Rather than dancing around the semantics of what it means to believe; why not hold a position worth discussing? Do you suspect there exists life in other solar systems? How strongly do you suspect it? If not, how strongly do you suspect life does not exist?

This is clearly a false dichotomy. You are positing I must either believe aliens exist or believe aliens do not exist. You forward this position through the question of why I would think life on Earth is so rare and so forth [Something I never said, nor would I say without backing].

The truth is a person has or lacks belief for these two statements:
There are aliens.
There are not aliens.

I lack the belief in both statements due to the lack of evidence for both of them. This action follows the foundations of science and induction.

i think that astrobiologists would disagree. take a different component of the Drake equation f_p and n_e. 2 or 3 decades ago they had no experimental evidence other than our own solar system what the values of those might be. now we see exoplanets all over the place and it begins to look like f_p might be nearly unity and n_e might be 1.6 . we, as a species with intelligence, are starting to get a grip on those parameters. there are several scientists that work in abiogenesis that have both discovered life on Earth that has no need of sunlight (it only requires water and an energy gradient in order to exist), they have discovered evidence of H₂O on other planets and moons in our solar system. they are working out the means to see if H₂O on certain exoplanets will be detectable in the light reflected from them. there is the Miller–Urey experiment that demonstrates the possibility of the emergence of organic molecules out of inorganic precursors.

so, maybe what you need to think about is the Strong Anthropic Principle. i don't know if i buy into it or not (everybody buys into the Weak Antrhopic Principle, since it is essentially a tautology). essentially, the SAP says that, if you shuffle an honest deck of cards and draw a single card offa the top, that eventually (if you give it a few billion years), you will draw the Ace of Spades. even if there are a helluva lot more cards in the deck than 52, eventually the "life-giving" card will be drawn, unless there is something physical that prevents it. but if you have the right kind of "petri dish" on the right kind of planet circling the right kind of sun, give it a billion years or so and the SAP says that eventually the right combination of molecules (and they have an idea what this combination may be) will fall together, chemical reactions will occur, organic molecules will emerge, complexity will increase, metabolism and self-replication emerge, etc. the probability of this cannot be zero because it happened here. as long as that Ace of Spades lies in the deck somewhere, eventually we will run the experiment and it will pop out.

i don't know why you think that the Copernican principle or Mediocrity principle is untrue. we got over the denial of that obviousness hundreds of years ago.

Drake's equation is merely a sequence of common sense probabilities with which a college student could come up if asked to do so for a project in his undergraduate probability class. It is basically a ploy to dress ignorance with a fancy name and fancy symbols for the purpose of giving an authoritative feeling as its user declares whatever he wants to declare with it. (It has been used, by the way, as 'evidence' for both sides of the argument.)

But that is beyond the point. The real point is in this sequence of n probabilities multiplied by the others, it wouldn't matter if we had accurately figured n - 1 of them. If there is but one unknown, it makes the entire product unknown. Your argument does not work.

And regarding this "anthropic principle", I have no idea what that is, and I don't intend to know what it is. If it says something evidentiary, go on and state it clearly instead of disguising the message with a fancy philosophical name. I will then judge it. But since no evidence exists as of now, I can assure you it is not a valid argument.

But the worst part of your post was its end, shown in bold. I never stated anything regarding these principles. I have no idea how you can transform my repeated, stated lack of belief in something into a belief in the complement of something else. That is logically impossible. I would appreciate if you staid away from the straw man fallacy, friend.

 

[jreelawg]

This is clearly a false dichotomy. You are positing I must either believe aliens exist or believe aliens do not exist. You forward this position through the question of why I would think life on Earth is so rare and so forth [Something I never said, nor would I say without backing].

You misinterpreted what I said. I asked you what you think and why? Your position could be anything. Having no position one way or the other about a subject doesn't make for a very interesting discussion.

 

[micromass]

This thread has gone way out of hand. It appears that the posters are just throwing around opinions and unverified claims. This is outside the scope of this forum.