Do you think aliens exist?

[Sparta]

Planets are a lot easier to form than life...

The 'there are so many stars that there must be life' doesnt really hold water though. It all depends what you think the chances of life arising were. It may have been pretty unlikely that it arose at all anywhere and we got lucky. We simply cant extend the fact of our own existence into evidence for any other life unless we can quantify the conditions for the abiogenisis of life.

Most arguments reduce to acts of faith, belief or wish fulfilment - and thats not a very scientific way to proceed.

What is the evidence! No evidence. No aliens.

But if mere lightning in a primordial atmosphere (water, methane, ammonia, and hydrogen) can generate amino acids (Miller-Urey), I'm inclined to view it as more likely than not that such circumstances have arisen at least once throughout the vastness of the universe. The more times those (or similar) circumstances have arisen, the better the odds that one such setup would have gone on to evolve into complex life forms. Given the quantities we're talking about, I personally take those as pretty high odds, although I think I follow you in that the odds you're accepting are what it all comes down to. Nonetheless, assuming we don't gather concrete evidence one way or the other in my lifetime (and I don't believe you can disprove something like that, for eons at least), I still feel a whole lot safer assuming the possibility of alien life rather than the converse.

What is the evidence! No evidence. No aliens.

Edit @ a space oddity: (I'd gotten more of a 'teacher spurring his students to present more thoughtful arguments' vibe from that myself .)

 

[IglooDame]

In the absence of evidence, I don't think they do, but I'm not going to be stunned and amazed if some show up anytime soon.

 

[a space oddity]

I'm the exact opposite: I believe they do exist, but I would be very surprised and upset should they show up anytime soon!

 

[Rambuchan]

Very nice!
(I had actually dug through a bookshelf in a futile effort to find an Asimov book to reference for a post in this thread as well (it's lent out I think ). FWIW, it was "Of Matters Great and Small", which featured an essay called "The Inevitability of Life". A review was all I could dig up)

Regarding doubts as to the possibility of generating of life:
The Miller-Urey Experiment
The same, seeded by comets
Either way, you've got amino acids, and you're off and running. Asimov had actually written about the comet/space angle decades ago too (man that guy was a genius).

Well I am glad some people visiting this thread have bothered to take note of the post introducing this fascinating and quite thorough book by Asimov (which is not a work of fiction). I'm particularly disappointed to see Col's comments avoid it altogether.

I should really clarify that this book is not so much a document providing evidence, rather he works through to find the probability that life exists elsewhere in the universe. The final figure for possible intelligent life forms he ended up with was quite quite staggeringly high. Can't remember it exactly but it was a high 6 figure number.

Perhaps the use of the word 'Alien' is what causes many to revolt against the idea of there being 'intelligent life' elsewhere in the universe?

 

[col]

Iclick Asimove is following the methodology of the seminal book in this area by Schlokovskii (sp?) and Sagan written in the late 1960s. The problem of course is assigning any quantifiable probability to each factor. There is little doubt that by manipulating the probabilities, you can basically get any answer you want.

Lets approach the problem from the point of view of evidence. We have had radio telescopes scanning our galaxy and beyond for about 50 years now. I was a student of Hewish when he discovered pulsars and thought he'd found the first evidence of intelligent life in the 1970s. Since then, despite SETI and all other experiments we have found nothing. Our instruments are good enough to detect any emission inside our galanxy or from the nearer local galaxies. Yet nothing.

Yes you can conjecture various motives from quarantine to secrecy but the simplest explanantion is that there isnt any other life in our galaxy emitting radio signals becasue there isnt any other intelligent life in our galaxy.

Why not?

Because the chances of intelligent life evolving are less than we hope. Maybe we have missed a key step. Its a long way from aminoacids to intelligent life.
Suppose there is a only 1 in 10^20 chance of it happening. It means that we are probably the only intelligent life anywhere.

Thats what the evidence tends to suggest.

 

[Rambuchan]

I know you've spent way more time and effort looking into these areas than me Col but isn't our reach with such detection somewhat limited - both technologically and distance-wise?

 

[Rik Meleet]

With the probability calculation Col uses, he starts from the assumption that there have to be 2 locations in the Universe where life started. 1 is the location we descend from and the other 1 is the location the other originated from.
But it is known that there is lifeforms that can survive extreme circumstances for a very long period of time. It is known that non-earth material does get to earth. It is not impossible theoretically that we have "brother" lifeforms from the same origin.

Not that I find that more realistic than starting on several locations, but Col is stepping over that too easily for my taste.

 

[Bozo Erectus]

Because the chances of intelligent life evolving are less than we hope. Maybe we have missed a key step. Its a long way from aminoacids to intelligent life.
Suppose there is a only 1 in 10^20 chance of it happening. It means that we are probably the only intelligent life anywhere.

I know this is the prevailing view of the scientific establishment today, but once so was an Earth centered universe. This is no different. Its natural to assume the Earth and humanity are somehow special. Not long ago life elsewhere in our own solar system was casually dismissed by the establishment. Now we know its just a matter of time before we discover it on Mars

 

[El_Machinae]

It is quite arrogant to assume that humans are the only sentient life in the universe, the universe isn't just for humans

Until I'm shown elsewise, I think that we should expand and colonize and take advantage of as much as possible. My policy is good because either:

a) there is unlimited wealth per capita available (there are about 20 stars in our galaxy alone for every living person).

b) we need to be as advanced and wealthy as possible before the aliens start competing with us.

 

[betazed]

@col: I accept the part - no evidence -> hence do not exist (as of now).

But I do not think you can scientifically put a number on the probability of life occurring anywhere else. That essentially amounts to guessing the factors in Drake's equation. For all we know the factors actually favor life. We do not know either way.

All we know is that life is possible.

Also, as for our hunting for SETI argument, our hunt have been abysmally narrow. We have searched only a narrow band of the galaxy. Also, a good assumption is that as a civilization matures it might get radio silent (as we are doing). So even if a radio search reveals nothing it does not prove anything. Even, otherwise, we assume that an intelligence will always develop technology. Why is that necessary? We were intelligent for a long time before we developed rudimentary technology. Maybe it is development of technology that is rare and not life and intelligence. If that is so then it may be that intelligent life is abundant but will remain largely undetectable.

 

[col]

Of course, the search goes on - but it is more in hope than in expectation.

We know that life happened once - and all life on Earth is pretty much the same. We hope that the conditions that lead to our existence may not be too unlikely to happen elswhere. We simply dont know. Intelligent life may be an even longer shot.

Of course we have scratched only a small part of the universe - but we have covered a substantial part of the galaxy and zilch. Nothing.

I'd like to point out the anomaly between folk that argue vociferously for scientific rationalism on such topics as evolution yet dont apply the same standards on their attitudes to aliens. They prefer to hope and believe and act on faith rather than evidence. Something they often accuse others of doing.

The hypothesis is: life here is unique. There is currently no evidence to disprove this hypothesis and until there is, it is the only reasonable position to adopt scientifically.

 

[betazed]

I know you've spent way more time and effort looking into these areas than me Col but isn't our reach with such detection somewhat limited - both technologically and distance-wise?

I have not done much studying on the subject (SETI/Astrobiology is a big field) but i have done a little and will try to answer this question a bit.

Given our current technology if there was a earth like planet with a earth like technologically advanced civilization even 10 parsecs away we will not be able to detect the planet or the civ as of now. We maybe able to detect some of our military radars (our strongest radio emitters apart from Arecibo) if we happen to point in teh right direction luckily. But the signals would not be persistent and will only be a blip - easily mistaken for radio noise. (Which interestingly we have detected. We have detected may strong blips and a really strong wow signal. http://en.wikipedia.org/wiki/Wow_signal So who knows maybe there is a real military radar within a few parsecs ) So to say that we have searched the galaxy for technology is really not correct.

However, that said we have technology to detect technology from the other side of the galaxy if we are lucky. For example, it is possible for teh Arecibo telescope to detect transmission from another Arecibo like telescope on the other side of the galaxy. Both have to be tuned to the same frequency and have to point to each other (a fantastically difficult and lucky setup). So all our SETI search was just that. Hoping to be fantastically lucky.

I will be more interested when the Terrestrial Planet Finder comes online. Then we can first seach for earth like planets and see how frequent they are. Then we will have at least one factor for life like us nailed down.

 

[Rik Meleet]

(..)I'd like to point out the anomaly between folk that argue vociferously for scientific rationalism on such topics as evolution yet dont apply the same standards on their attitudes to aliens. They prefer to hope and believe and act on faith rather than evidence. Something they often accuse others of doing.

Sorry, that language is too difficult for me. Can you please translate that into easier english ??

The hypothesis is: life here is unique. There is currently no evidence to disprove this hypothesis and until there is, it is the only reasonable position to adopt scientifically.

Very shaky theorem, Col. Where is "here" for instance.
Definately true nonetheless, because we are yet barely able to scratch outside our "here". However, I feel it is incorrect to state this when we have so little knowledge of the rest. Imagine being a scorpion in the desert. Whereever he goes (1 mile to each direction) there are only sanddunes. The statement "There is no water on this world" is definately true for him, although untrue. I don't like making these hard statements without proper and enough measurements.

"1 is not a prime. 2 is a prime. 3 is a prime number. Thus all numbers greater than 1 are primes."

 

[a space oddity]

I'd like to point out the anomaly between folk that argue vociferously for scientific rationalism on such topics as evolution yet dont apply the same standards on their attitudes to aliens. They prefer to hope and believe and act on faith rather than evidence. Something they often accuse others of doing.

The hypothesis is: life here is unique. There is currently no evidence to disprove this hypothesis and until there is, it is the only reasonable position to adopt scientifically.

Hmm, I don't think that this is entirely fair: that there *is* life in the universe is a given. Like I said earlier it's not so much 'hope' that makes it likely IMO. If alien life *should* visit us, we are in big trouble! Remember what the flu did in the America's... and that was of earthern origine.

It is more the likeness of the argument to when people thought the Earth was the center of the universe, had to be. All the stars were evolving around us, pure observation. It is not until someone thought to measure how they evolved, that people found that reasoning was flawed. But if the Earth is not that our Sun should be... Oh it's not, well then our Sun must be unique... oh, it's not. Solar systems? No? Well then ultimately, life is surely unique to Earth. And when it's not life, then surely intelligence is limited to us... and if not intelligence then certainly our technology is!

 

[Rambuchan]

Well I'm defering to other people's greater knowledge on the subject now. But I'm reading with interest. Just in case you were expecting a response.

 

[Dida]

We have enough problems to worry about on this planet. Let's leave alien affairs to aliens.

 

[Archbob]

Why is it so hard for some people to comprehend that a god might exist?

Alot of people do, but they just don't believe in the Christian God or religion. Just because God exists, doesn't mean it has to be your God.

 

[Perfection]

I regard belief in aliens as essentially the same as belief in fairies. Cute but non scientific.

I don't. I view at as a sort of "lesser evil". That is we know that there is some finite chance that some extraterrestrial civilization does exist. The fallacy is alleging that the probability must be greater then a certain threshold.

The simplest explanation for the lack of evidence of life elsewhere is that there isnt any other life in the universe.

I should note that while your explination does fit well with intelligence (which does seem rather flukish), the application to life may not be as apt. You will note the relative rapidness of abiogenesis. While it could be dismissed as merely coincidental it may make more sense to call the chemical processes behind it relatively easy given the right circumstances. This leads me to believe that extraterrestrial life may not be all that rare.

I refuse to believe that life on Earth is a unique experience in the whole Universe. Lack of evidence doesn't imply non-existence of. Given the size of the universe the propability of another planet approximating Earth's condition is likely. Life could arise from earth, it can arise on another planet.

Remember though, the universe is finite, what is the probability of a second intelligence developing elsewhere in the universe? What is the probability of them ever meeting?

Lets approach the problem from the point of view of evidence. We have had radio telescopes scanning our galaxy and beyond for about 50 years now. I was a student of Hewish when he discovered pulsars and thought he'd found the first evidence of intelligent life in the 1970s. Since then, despite SETI and all other experiments we have found nothing. Our instruments are good enough to detect any emission inside our galanxy or from the nearer local galaxies. Yet nothing.

I'm skeptical of SETI's methodology. SETI couldn't pick up Earth even if it was very close because it would be overwhelmed the sheer amount of radio noise of the star.

I know this is the prevailing view of the scientific establishment today, but once so was an Earth centered universe. This is no different. Its natural to assume the Earth and humanity are somehow special. Not long ago life elsewhere in our own solar system was casually dismissed by the establishment.

Actually there is a slight difference, those who proposed a different center for the universe (or none at all) actually had evidence

Now we know its just a matter of time before we discover it on Mars

Is it? I'm not conviced.

Sorry, that language is too difficult for me. Can you please translate that into easier english ??
Very shaky theorem, Col. Where is "here" for instance.
Definately true nonetheless, because we are yet barely able to scratch outside our "here". However, I feel it is incorrect to state this when we have so little knowledge of the rest. Imagine being a scorpion in the desert. Whereever he goes (1 mile to each direction) there are only sanddunes. The statement "There is no water on this world" is definately true for him, although untrue. I don't like making these hard statements without proper and enough measurements.

"1 is not a prime. 2 is a prime. 3 is a prime number. Thus all numbers greater than 1 are primes."

Now that's fair. This is very shaky. Col shouldn't be too attached to his numbers and neither should anyone else. There is not a lot of facts to grip on to here.

 

[PlutonianEmpire]

Yes, they exist, and according to Zecharias Sitchin, they visited Earth in the past (although I now doubt Sitchin).

 

[Perfection]

Like I said before PE:

Zecharia Sitchin knows nothing about astronomy.