Likelyhood of Extraterrestrial Intelligence

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  • #1
CJames
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On first glance, it seems as though the universe is so big there simply must be other life out there. And that may be the case. But is it possible that life is as common as portrayed in the scifis?

Most likely, the answer is no. The truth is, if life were that common, it would be plainly visible. It doesn't take a huge knowledge of statistics to understand.

If an extraterrestrial civilization had existed before us, they should have had something close to half the galaxy's lifetime to collonize it. Collonizing the galaxy seems like a monumental task, especially when you take into account that it is unlikely superluminal velocity is possible. However, in comparison to the age of the galaxy, its size is quite small. It's easy to forget that the galaxy has rotated several times (at much slower than lightspeed) since life got started on EARTH. It's rotated once since the dinosaurs.

So if one extraterrestrial intelligence had existed before us, they had plenty of time to collonize the galaxy. And if they had done so, we would see something. Structure in the galaxy. Mined stars. Artifacts. Radio signals.

Does this mean there is no extraterrestrial intelligence? No. But it does mean it is almost certainly rare. Unless by some freak of coincidence another intellligent race emmerged within a few million years of ours, we are the only intelligent race in our galaxy.

If extraterrestrial intelligence exists, there are two options. They exist in distant galaxies, or they exist in the future.

On a sidenote, it at least seems highly unlikely that only 1 intelligent race would ever form in our galaxy, considering how long it has left to live. A likely time for another one to pop up would be somewhere around twice the age of the present Milky Way's age, assuming intelligent races pop up on a regular basis.

Any thoughts?
 

Answers and Replies

  • #2
jjalexand
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Self-organization (complexity theory?) argues for intelligent alien life.

Self-organization derives from positive feedback under constraint.

Gas clouds contract under self gravity (+ve feedback as density increases).

Initial random rotation leads to spin by conservation of momentum.

Spin leads to disks.

Disks lead to rings.

Rings lead to planets.

Thus most stars may have planets.

Co-operative positive feedbacks of self-catalytic loops of co-operating reactions lead to selective reproduction of certain catalytic molecules (+ve fbk).

Reproduction with limited resources leads to competition.

Competition leads to evolution.

Evolution leads to better self-oganization and co-operation.

Thus life will start as soon as there is a viable pathway, and evolve to fill all ecological niches. (As we see in cases of parallel evolution).

Intelligence is a competitive advantage, thus will be adopted by life if there is a viable pathway.

The parallel evolver does not need to know anything about the original or even be on the same planet.

Thus a percentage of planets probably hold life, and some intelligent life.

Why haven't we heard from them?

Perhaps someone somewhere invented computers which led to AI, which out-competed its creators and became inimical to life.

We'll probably know soon enough as the volume of the sphere of our detectable radio emissions (and thus the number of stars able to discover us) is increasing with the cube of time.

Sorry, I've had a few beers, I'm sure there's a better explanation.

:)
 
  • #3
Zefram
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Suppose intelligence doesn't necessarily imply science? Maybe they all write poetry and couldn't care less about galactic colonization and radio astronomy.

Somehow that seems worse to me than being alone in the galaxy... :wink:
 
  • #4
russ_watters
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Most likely, the answer is no. The truth is, if life were that common, it would be plainly visible. It doesn't take a huge knowledge of statistics to understand.
If most of what we know about science is even remotely accurate, then this is not correct. With current technology we could not even detect life 100ly away unless they are actively transmitting something we can receive. And through passive detection, we couldn't even find life 10ly away. We don't yet have the ability to even locate Earth sized planets anywhere outside the solar system, much less analyze one.

Our galaxy is roughly 150,000 ly in diameter. There could be THOUSANDS of planets with human level life/technology and we won't know it.

If an extraterrestrial civilization had existed before us, they should have had something close to half the galaxy's lifetime to collonize it. Collonizing the galaxy seems like a monumental task, especially when you take into account that it is unlikely superluminal velocity is possible. However, in comparison to the age of the galaxy, its size is quite small. It's easy to forget that the galaxy has rotated several times (at much slower than lightspeed) since life got started on EARTH. It's rotated once since the dinosaurs. So if one extraterrestrial intelligence had existed before us, they had plenty of time to collonize the galaxy. And if they had done so, we would see something. Structure in the galaxy. Mined stars. Artifacts. Radio signals.
There are a couple of problems with this. For starters the technology you describe is not even theoretically possible: Interstellar travel will likely not ever be possible for anyone.

Second, time isn't as wide open as you think: planets with life require second or third generation stars because the ingredients for (solid) planets and life didn't exist in the early universe: they were created in supernovas. So even though the universe is about 15 billion years old, earthlike planets have likely only existed for about the past 5. It also takes a few billion years for the planet to cool enough for life to arise. Then a few billion more for life to evolve. Altogether, intelligent life has probably only been possible in the galaxy for the past billion years.

Also there is the issue of concurrence: It can't be assumed that any life that has ever existed still exists. Hell, many people still think humans will destroy themselves within the next 100 years. Thousands of intelligent species could have lived and died and there is virtually no chance we will ever know about it.

Given all of the statistical analysis I have seen, I think it is possible, even likely that there is other life out there. Intelligent life. But there would need to be THOUSANDS of civilizations existing today for us to even have a chace to find ONE. Despite all of that, I think in the next 20-30 years we WILL find one.
 
  • #5
cragwolf
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Originally posted by Zefram
Suppose intelligence doesn't necessarily imply science? Maybe they all write poetry and couldn't care less about galactic colonization and radio astronomy.

Somehow that seems worse to me than being alone in the galaxy... :wink:

Yes, I agree with you! Dirac once said the following:

"In science one tries to tell people, in such a way as to be understood by everyone, something that no one ever knew before. But in poetry, it's the exact opposite."

Lately I've been thinking that what Dirac said about poetry is true about all art. It seems to me that art is basically just intellectual obfuscation and mental masturbation. Hence the reason it needs to seduce or manipulate our emotions. So for me, an intelligent lifeform that didn't pursue science, but instead pursued some artistic goal, would be a very sad thing. Solipsism of the worst kind.

I think ETs are rare, but the universe is also pretty large. I also think that carbon chemistry need not be the only possibility for self-aware structures. Unfortunately, my imagination is far too limited to dream up alternatives to it.
 
  • #6
Janus
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Couple of things;

I think its already been pointed out that Interstellar travel just might be to difficult or resource consuming for anyone to have achieved.

Another Possibility is the Intelligence turns out to be, in the vast majority of cases, an evolutionary dead-end. That very very few intelligent races survive long enough to develop high-end technology.

Or that upon reaching a certain level, they slip back to a lower level. (A hole that they won't be able to pull themselves out of, because the previous technological society has already used up the easily obtainable resources on their world. )

The universe could be full of low-technology races, and maybe only one or two higher-end technology races per galaxy.
 
  • #7
russ_watters
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So for me, an intelligent lifeform that didn't pursue science, but instead pursued some artistic goal, would be a very sad thing. Solipsism of the worst kind.
I'll go one step further: An intelligent life form that does not pursue science is an oxymoron.
 
  • #8
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And given the importance of science on this planet, shortly a dead oxymoron.
 
  • #9
Mentat
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Also, Michio Kaku once pointed out (in "Journey through the tenth dimension) that the probability of intelligent creatures evolving somewhere else is rather high - but that they would soon discover Uranium, and the probability then becomes extremely high that they would destroy themselves.
 
  • #10
Zefram
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Lately I've been thinking that what Dirac said about poetry is true about all art. It seems to me that art is basically just intellectual obfuscation and mental masturbation. Hence the reason it needs to seduce or manipulate our emotions. So for me, an intelligent lifeform that didn't pursue science, but instead pursued some artistic goal, would be a very sad thing. Solipsism of the worst kind.

Agreed. If only more of our own species saw this.
 
  • #11
Loren Booda
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As I posted elsewhere previously: remember your statistics - just one incidence of life's origin does not carry any significance toward the probability of other, similar occurences.
 
  • #12
Njorl
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Originally posted by Loren Booda
As I posted elsewhere previously: remember your statistics - just one incidence of life's origin does not carry any significance toward the probability of other, similar occurences.

I agree with you for the most part, and have made jokes about extrapolating from a single point, but there are some "single instances" with notable impact. The observation of evolution on our one planet is telling. It is not a single point of statistics, it is an observation of the nature of life. I don't think it is unreasonable to assume a high likelyhood that if life exists elsewhere, it will evolve. It is a bit of a jump though to assume that evolution leads to intelligence. It has only been recently that intelligence has proven very useful to life.

I think the biggest flaw in CJames theory is that a civilization would colonize the galaxy just because it could. We are primitive compared to such a civilization, and yet we have begun to develop non-interference philosophies regarding wildlife studies and anthropology. If a civilization learned to satisfy all of its wants before developing interstellar travel, it could plausibly develop the same ideals, applicable on a galactic scale. Assume one civilization is particularly precocious. It then monitors the galaxy with a light touch, preventing latecomers from "despoiling" other planets. I would imagine that would be our own philosophy...after we despoiled a few dozen planets first.

Njorl
 
  • #13
CJames
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Excellent arguments by everybody. Let's see how badly I can defend my "theory." (It's not actually mine. Idea's been around for a while. And it's not a theory.)

First, let me reitorate my point. I hadn't said there is no other intelligent species in the universe. I said intelligent life is rare or nonexistant.

Russ_Walters,
There are a couple of problems with this. For starters the technology you describe is not even theoretically possible: Interstellar travel will likely not ever be possible for anyone.
It is certainly theoretically possible. As you have said, the galaxy is 150,000 lightyears across. That means an absolute bare minimum of 75,000 years allowed to collonize the galaxy. Obviously, that is ridiculous. However, limited to an expansion rate of .01c, for a civilization that first formed on the outer rim of the galaxy, that means 15 million years to collonize the galaxy. So, it is easy to establish that it is at least possible by this time.

It can't be assumed that any life that has ever existed still exists.
I agree entirely. As I said, my point was that we are probably the only intelligent species in our galaxy at this time.

Njorl,
I think the biggest flaw in CJames theory is that a civilization would colonize the galaxy just because it could.
This is a very good point. Considering population growth, however, I would imagine any intelligent species would be scrambling for the nearest planet as fast as possible. If there is another intelligent species in the galaxy, it has either learned to slow it's population growth, or has am extremely slow population growth. (Perhaps living in a different life-expectancey.)

Take care everybody.
 
  • #14
cragwolf
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Originally posted by russ_watters
I'll go one step further: An intelligent life form that does not pursue science is an oxymoron.

I think you're confusing wisdom with intelligence. Beethoven's Ninth Symphony was clearly created by an intelligent mind. A life form which did nothing of note except create equivalents of Beethoven's Ninth Symphony would be intelligent, but not very wise.

Originally posted by Zefram
Agreed. If only more of our own species saw this.

Don't get me wrong, though. I'm often moved by a great work of art. But to what end? It's mostly my emotions that are affected. As for what intellectual content there is, and there's usually very little of it, I find myself asking, "It took him 500 pages to say that humans are contradictory beings?"
 
  • #15
Zefram
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Yes, I get very frustrated with "intellectuals" who talk a great deal but end up saying practically nothing. I like it clear, concise, and straightforward; to some extent, that's why I enjoy the sciences.
 
  • #16
russ_watters
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I think you're confusing wisdom with intelligence. Beethoven's Ninth Symphony was clearly created by an intelligent mind. A life form which did nothing of note except create equivalents of Beethoven's Ninth Symphony would be intelligent, but not very wise.
Thats fine, but I think the two go together. The brain power associated with the writing of Beethoven's Ninth is similar to the brain power associated with figuring out relativity. Its just brain power applied in a different direction. Intellectual art.

There *IS* a lot of art that is not intellectual though. I tend to think most painging and sculpture it that way. Van Gough for example made some great paintings, but he was certifiably insane. Modern art is even worse. You can sneeze on a piece of paper and sell it.

And since I am of the opinion that "good" art is intellectual, not purely creative, I think an intelligent species will create both intellectual art and science. One that creates purely creative art is not intelligent and it will reflect in the art.
 
  • #17
CJames
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The reason I assume intelligent life would seek to collonize the galaxy is because of the nature of intelligence. Intelligence arises from a curiosity to know things. It is my assumption, and yes it is an assumption, that this curiosity would be a major factor in the desire to collonize the galaxy.
 
  • #18
all I can say is hopefully curiosity won't kill the cat if we go explore other galaxies someday. Haha



But on a more serious matter I think that what you said (the part about how curiosity could possibly lead to the colonizaatino of galaxies) is correct, CJames
 
  • #19
Don't forget about mass extictions due to asteroids and comets (if not dying stars). They happen roughly every 50-100 million years on Earth, most recent 65 million years ago with the Dinosaurs. Who knows if any other civilization has even gotten the time to develop the technology needed to colonize outside of their home planet.
 
  • #20
drag
Science Advisor
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Greetings !

My very rough SWAG for the MW galaxy :

About 200 * 10^9 stars in the MW.

- double/tripple and so on...
- galaxy core
- probably - stars with low or high metalicity (leaving
mostly the central galactic radius range)
- stars that are too massive and produce
a great deal of UV radiation
- very "light" and cool stars

= let's say 10 - 20 * 10^9 stars.

- stars that are aged over 2-3 billion years
- stars that do not have planets in the
habitable zone around the star (allowing for
liquid water ) or gas giants that allow
water on their moons (example: Europa)
- planets that do not have the appropriate
materials to form a solid core and a stable
surface and materials to result in creation of
large water masses

= let's say 10 - 20 * 10^6 stars and about
a 10% addition for planets

- planets where living cells haven't formed

= let's say (and this is beggining to be very
tricky to estimate) about a half remains

- no complex life forms evolved or they were
destroyed by asteroids/high radiation events/
collisions with other star-systems/system
star's life span ends

= (very very tricky) a complete SWAG - 50,000

- planets where complex life formed but no
"intellegent" life on our level, at least (There is
a great argument about this part, I believe.
Are we a natural stage or a fluke ?)

= unbelievable SWAG : 500

How was I ?

"Does dice play God ?"

Live long and prosper.
 
  • #21
CJames
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My point is essentially that if there had been even one intelligent species created before us, they would literally be almost everywhere in the galaxy. And the more intelligent species that came before us, and even greater chance that many of them are spread throughout the galaxy. Given five hundred civilizations before us, we would probably see activity as close as the very nearest earthlike planet.

Within our own galaxy, we are most likely the only intelligent species at this time. If that is not the case, I wouldn't expect much more than 3 or so as an absolute maximum, considering the amount of time life has had to spread across the galaxy. Remember, it is life's goal to multiply and recreate itself. Those that recreate less often are killed off evolutionarily. Evolutionary predisposition seems to dictate that any species capable of leaving the planet most likely will.

Given 500 intelligent civilizations that came before us, the galaxy would probably be so populated by now that even Mars would have been collonized. It seems obvious that 500 civilizations is over the top.

Again, this is not proof. But if there are intelligent species out there, they are reclusive. It's hard for me to imagine a world in which it is an evolutionary advantage to multiply slowly, especially if such a world is the type that would harbor intelligent life.

Thank you so much for these debates. Keep it up. --Carter
 
  • #22
chosenone
183
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what do you want to know about them,we havbe long talks all the time,they like the name the grays,if you want to know what they like to be called,but anything else you'll have to get pass me being a lunitic,because they still don't give them a reason to lock me up yet,so I am doing good!
 
  • #23
drag
Science Advisor
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Greetings !

Hmm... CJames,
What if they don't multiply ?
What if they put their brains in "jars" and living in
great computer simulations where they are
all powerful ?
What if their progress was greately halted by
wars ?
What if they don't want to contact us ?
What if FTL travel is impossible so they saw
life's here and decided not to visit and interfere ?

I can think of a great deal of reasons really.

"Does dice play God ?"

Live long and prosper.
 
  • #24
Raavin
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We already have examples on Earth of civilisations that don't have technology as the west would recognise it. There could also be religious or cultural ethical consideration that would disallow the applications of technologies even if they knew about them. I once worked on a sci-fi story where all the technology was chemistry based and electricity, as in radio etc., was not a part of it. A race could have developed theory purely mathematically and applied it at a more advanced stage so that transmissions might posess chaotic principles that wouldn't be seen by us to have enough of a pattern to be discerned as created by an intelligence. I have a theory about dolphin communication that they communicate by 'transmitting' abstract images rather than 'words' or patterns which is why we have identified dolphins referring to others by 'name' sounds but uncovered little else.

All that said, if you don't believe in devine intervention, there would seem to be no reason why, chemically speaking, the development of life here could have been pure luck and that the chain of events has never occurred anywhere else. Depending on the balance of elements on the planet, they may have achieved a steady state before any 'life-like' properties took over. Perhaps it takes the exact balance of elements that, per chance, happened on Earth to achieve life.

Do I believe that there is intelligent life out there? I'd like to think so, but then again...

Raavin [?]
 
  • #25
ObsessiveMathsFreak
406
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If intelligent life were around they would undoubtedly have either colonised or exploited this solar system by now.

I think the range of conditions on all the planets in the solar system is rather diverse, Earth might be toxic to them. And the fact that it has nine planets would make it very important tatically, wouldn't it?

I really, really doubt that they would be benevolent enough to let us stew for a while.
 
  • #26
cragwolf
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Originally posted by ObsessiveMathsFreak
If intelligent life were around they would undoubtedly have either colonised or exploited this solar system by now.

Why? Why should interstellar travel be inevitable? Why should colonisation be inevitable?
 
  • #27
CJames
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I'm glad somebody here agrees with me lol.

Why is collinization inevitable? It's not entirely inevitable, but it seems the most likely action. Again, life has always tried its hardest to spread. Why do bacteria live in some of the most harsh places on Earth? Because life expands, it breaks into new territories. If the bacterial fossils on Mars were real, we may find that this entire galaxy is inhabited by many forms of life. But it is unlikely any of them are intelligent, because if they had been, they would have left behind remnants, or we would see them nearby. If we don't see evidence of intelligent life within the next few decades, I would put money into the idea that we will never find an intelligent species in this galaxy the same time as us.

Hi drag, love your debates always

Hmm... CJames,
What if they don't multiply ?
What if they put their brains in "jars" and living in
great computer simulations where they are
all powerful ?
What if their progress was greately halted by
wars ?
What if they don't want to contact us ?
What if FTL travel is impossible so they saw
life's here and decided not to visit and interfere ?

I can think of a great deal of reasons really.
All these "what if"s would solve the problem. That's not the point. How likely is it that any of these are the case? Evolution dictates that life multiply. Why would they put their brains in computer simulations when doing so would jepardize their safety from the death of their star? Wars wouldn't halt expansion, it would encourage it. They don't have to want to contact us. If they are close enough, we would see plenty of signs of their existence. And considering how long they've had to get close, they would be close. It doesn't matter if FTL travel is impossible, I demonstrated how that doesn't matter when you are collonizing the galaxy.

So of course it's possible there is other intelligent life in our galaxy. But it appears to be an unlikely scenario.

Take care. --Carter
 
  • #28
DrChinese
Science Advisor
Gold Member
7,694
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Originally posted by drag
Greetings !

My very rough SWAG for the MW galaxy :

About 200 * 10^9 stars in the MW.

- double/tripple and so on...
- galaxy core
- probably - stars with low or high metalicity (leaving
mostly the central galactic radius range)
- stars that are too massive and produce
a great deal of UV radiation
- very "light" and cool stars

= let's say 10 - 20 * 10^9 stars.

- stars that are aged over 2-3 billion years
- stars that do not have planets in the
habitable zone around the star (allowing for
liquid water ) or gas giants that allow
water on their moons (example: Europa)
- planets that do not have the appropriate
materials to form a solid core and a stable
surface and materials to result in creation of
large water masses

= let's say 10 - 20 * 10^6 stars and about
a 10% addition for planets

- planets where living cells haven't formed

= let's say (and this is beggining to be very
tricky to estimate) about a half remains

- no complex life forms evolved or they were
destroyed by asteroids/high radiation events/
collisions with other star-systems/system
star's life span ends

= (very very tricky) a complete SWAG - 50,000

- planets where complex life formed but no
"intellegent" life on our level, at least (There is
a great argument about this part, I believe.
Are we a natural stage or a fluke ?)

= unbelievable SWAG : 500

How was I ?

"Does dice play God ?"

Live long and prosper.

Not bad - actually very good - but I think you are off on the high side.

Realistically, you have to allow 4.5 billion years for life to evolve on the planet. That being what it took here, and certainly you would have say the laws of chance were with us. So planets less than 4.5 billion years old... well, that means their sun is also a yellow star like ours, which is rare. Most burn out much quicker, 10-100 million years. And would have to have formed about the same time as our sun, universe about 9 billion years old. Could not have formed too much earlier, because there weren't enough heavy elements around. So perhaps high by a factor of 100, since you did mention some of these factors.

As to planets, the planet would have to be very close to the exact orbit we are in. You mentioned this. Also, can't have an elliptical orbit either. High by another factor of 100.

Probably need a moon as well. And the ocean. And an atmosphere. High by a factor of 1000.

As to the formation of life, this is far and away the biggest issue we have. Because of the complexity of our genetic structure, it must have taken a lot of random mutations to get where we are today. I can easily imagine thousands of other planets in the universe filled with plants and fish.

And then there is human life. Humans having several rather unique attributes when you think about it: a voice box capable of speech; unusally large brain (compared to other mammals even); fingers; walk on 2 legs; extremely long development period after birth before can even walk. I'd say one in a million on this one.

Net, I would say odds are more like one in 200 million galaxies. I think we live in a very lonely universe.
 
  • #29
drag
Science Advisor
1,100
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Greetings !
Originally posted by DrChinese
Not bad - actually very good - but I think you are off on the high side.
Thanks !
I think...
It was an amateur attempt (I actually done this
some time ago in a more consistent manner, but
the result was about the same - a few hundred.)
Originally posted by DrChinese
Realistically, you have to allow 4.5 billion years for life to evolve on the planet. That being what it took here, and certainly you would have say the laws of chance were with us. So planets less than 4.5 billion years old...
First of all, the Earth exists less than 4.5
billion years which is the time the Sun formed.
Second, life formed about 3.5-3.9 billion years
ago.
Third, "complex" life formed almost half a billion
years ago.
Fourth, there's no apparent reason why this
couldn't've happened earlier and I disagree
with the chance part - "If the conditions
are right...".
Originally posted by DrChinese
well, that means their sun is also a yellow star like ours, which is rare. Most burn out much quicker, 10-100 million years. And would have to have formed about the same time as our sun, universe about 9 billion years old. Could not have formed too much earlier, because there weren't enough heavy elements around. So perhaps high by a factor of 100, since you did mention some of these factors.
I DID say - "stars that are too massive and produce
a great deal of UV radiation".
Stars that peak at visible wavelenght and lower
do exist for billions of years. Even if you have
a smaller star with peaks at infrared - I can
see no reason why a close enough planet couldn't
have water and evolve life. The larger stars are
not a majority.

Also, the Universe is about 13.7 billion years old...:wink:
And, I did talk about the mettalicity factor.
Originally posted by DrChinese
As to planets, the planet would have to be very close to the exact orbit we are in. You mentioned this. Also, can't have an elliptical orbit either. High by another factor of 100.
Well we are probably in an almost ideal location,
but I think that this could easily be a 100 million
kms or wider distance range (depending on the
planet too - its own rotation cycle, material
and so on). I do not think that an elliptical
orbit is a great hazard.
(I once read "The Fire Cycle" by Hall Clement -
it's a sci-fi book but he talks of a planet
that has an elliptical orbit and is populated
by two civilizations. One "wakes up" during the
"summer" and the other during the "winter".
Of course, it's a sci-fi book... :wink:
However, on Earth, life is found EVERYWHERE !
So, after it forms, the rest is not that
difficult - adaptation.)
Originally posted by DrChinese
Probably need a moon as well. And the ocean. And an atmosphere. High by a factor of 1000.
Moon/s - why ?
Ocean - I included water - not necessarily in
the form of surface oceans like ours (look at Europa).
Atmosphere forms with time and effected by life,
the "start" conditions are local.
Originally posted by DrChinese
As to the formation of life, this is far and away the biggest issue we have. Because of the complexity of our genetic structure, it must have taken a lot of random mutations to get where we are today. I can easily imagine thousands of other planets in the universe filled with plants and fish.
So, it won't be "us"... So what ?
It is an intellegent civilazation of
non-humans, not possible in your opinion ? :smile:
Do you know that we only have about 50%
more genes than the most primitive organisms ?
If you are in general familiar with Chaos
theory and your PC then you know that the simplest
patterns and the simplest differences in them
can produce great complexity and differences in it.
Originally posted by DrChinese
And then there is human life. Humans having several rather unique attributes when you think about it: a voice box capable of speech; unusally large brain (compared to other mammals even); fingers; walk on 2 legs; extremely long development period after birth before can even walk. I'd say one in a million on this one.
Like I said, the question is - Are we a natural
stage or a fluke ?
My personal opinion is that we are a "fluky"
natural stage...
Originally posted by DrChinese
Net, I would say odds are more like one in 200 million galaxies. I think we live in a very lonely universe.
"Net" = are you Russian ?
Anyway, I hope you're wrong !
Even if the opposite is not good for humanity,
it would be sad if the Universe as a whole
was such an "empty" place, in my opinion.
Be optimistic ! And ready your X-ray gun !

Live long and prosper.
 
  • #30
drag
Science Advisor
1,100
1
Greetings !
Originally posted by CJames
Hi drag, love your debates always
Thanks !
Originally posted by CJames
All these "what if"s would solve the problem. That's not the point. How likely is it that any of these are the case? Evolution dictates that life multiply. Why would they put their brains in computer simulations when doing so would jepardize their safety from the death of their star?
Who cares ?
In a perfect simulation you can have infinite
fun ! Many sufficiently advanced civilizations,
in my opinion, will realize that that's the most
important thing... :wink:
Originally posted by CJames
Wars wouldn't halt expansion, it would encourage it.
That was a "shallow" argument, wan't it...
You're right, of course.
(Unless they almost totally destroy themselves.)
Originally posted by CJames
They don't have to want to contact us. If they are close enough, we would see plenty of signs of their existence. And considering how long they've had to get close, they would be close. It doesn't matter if FTL travel is impossible, I demonstrated how that doesn't matter when you are collonizing the galaxy.
I'm not certain about that. What if we're
not evolved enough to detect those signs ?
Or, they take measures for us not to be able
to detect them ?
Originally posted by CJames
So of course it's possible there is other intelligent life in our galaxy. But it appears to be an unlikely scenario.
Aah... pessimists... :frown:

"When I examine myself and my methods of thought,
I come to the conclusion that the gift of fantasy
has meant more to me than my talent for absorbing
positive knowledge."
Albert Einstein

Live long and prosper.
 
  • #31
DrChinese
Science Advisor
Gold Member
7,694
1,543
Originally posted by drag
Greetings !

Thanks !
I think...

First of all, the Earth exists less than 4.5
billion years which is the time the Sun formed.
Second, life formed about 3.5-3.9 billion years
ago.
Third, "complex" life formed almost half a billion
years ago.
Fourth, there's no apparent reason why this
couldn't've happened earlier and I disagree
with the chance part - "If the conditions
are right...".

I DID say - "stars that are too massive and produce
a great deal of UV radiation".
Stars that peak at visible wavelenght and lower
do exist for billions of years. Even if you have
a smaller star with peaks at infrared - I can
see no reason why a close enough planet couldn't
have water and evolve life. The larger stars are
not a majority.

Also, the Universe is about 13.7 billion years old...:wink:
And, I did talk about the mettalicity factor.

Well we are probably in an almost ideal location,
but I think that this could easily be a 100 million
kms or wider distance range (depending on the
planet too - its own rotation cycle, material
and so on). I do not think that an elliptical
orbit is a great hazard.

Moon/s - why ?
Ocean - I included water - not necessarily in
the form of surface oceans like ours (look at Europa).
Atmosphere forms with time and effected by life,
the "start" conditions are local.
I was trying to pay a compliment. Naturally, one of the problems of this kind of analysis is that different people will come up with different estimates. I acknowledge that mine is no more "correct" that yours or anyone elses'. If there are a statistically large number of civilizations predicted to exist in the universe, then the analysis becomes more meaningful. I am biased towards the lower end of predictions: so few that we can't expect to make contact during the next million years.

The requirement that the sun be of the right type is pretty restrictive. Ok, there is a range of possible start times for the creation of the star. Sure seems that the Earth was created fairly late in the game given the amount of iron on the planet. Yet, we have needed 99.9999+% of the lifetime of the planet to get to this point. It is certainly possible a candidate planet could have formed a bit earlier, and it is certainly possible that intelligent life could have formed in less time. But there is still a narrow time window and a narrow solar type range.

I believe you already excluded binary star systems, correct?

But, we have an ocean and an atmosphere. And a moon that creates tides, which is what I was referring to. I am guessing that the sloshing of the ocean was needed to create and distribute early simple life. Assuming (and it is an assumption) that these are necessary for the ultimate formation of intelligent life, you have some additional restrictions. Mars has no atmosphere (ok, a little) and no ocean (ok perhaps some buried ice). So how did Earth end up with all the water, and Mars has no intelligent life? Or is that a coincidence?

It is generally (?) believed that the Earth's atmosphere was at one time primarily CO2. It was later "cooked" by cyanobacteria into O2. This may have taken 500 million years.

Another - as you mentioned - restrictive requirement is the orbit shape and distance from the star. A planet like Earth could orbit at any distance from the sun, even as far out as Pluto. Yet only a small range - perhaps 80-100 million miles from the sun (depending on mass of the star) would provide a temperature for water which would allow life to exist. If an elliptical orbit brought the planet too close to the sun, life would boil off. So the eccentricity could not be much.

So personally, I can't imagine more than a few hundred earthlike planets orbiting suns of the correct mass/age and in the proper orbit per galaxy. And that is before we start talking about the evolution of intelligent life on such a planet.

Just my thoughts :)
 
  • #32
drag
Science Advisor
1,100
1
Greetings DrChinese !
Originally posted by DrChinese
I was trying to pay a compliment.
Like I said - thanks ! :smile:
Originally posted by DrChinese
Naturally, one of the problems of this kind of analysis is that different people will come up with different estimates.
Indeed. I simply prefer optimism, and you with
CJames apparently side with the pessimists.
Originally posted by DrChinese
The requirement that the sun be of the right type is pretty restrictive.
Why ?
Is there a problem with a smaller star with
radiation mainly around the infrared ?
Originally posted by DrChinese
Yet, we have needed 99.9999+% of the lifetime of the planet to get to this point. It is certainly possible a candidate planet could have formed a bit earlier, and it is certainly possible that intelligent life could have formed in less time. But there is still a narrow time window and a narrow solar type range.
I don't know. How narrow and why ?
After all, the "surge" of complex life forms
on the planet began just a few million years
ago. I don't know what triggered it (there was
a lot of orgamisms for billions of years before
that). Also, if it weren't for that Yukatan
astroid, you'd probably have huge dino-cities
covering the planet by now and dinos expanding
in the galaxy. I recently saw a program where
they were talking about a dinosour just a bit
larger than us that had a brain as complex as
that of our pets. It evolved "just" before the
above "accident".

If someone does know what triggerd "complex"
life - please tell us !
Originally posted by DrChinese
I believe you already excluded binary star systems, correct?
Yes, I excluded all multiple star-systems.
Originally posted by DrChinese
I am guessing that the sloshing of the ocean was needed
to create and distribute early simple life.
Hmm... I suppose that the Moon did help a bit,
but I think that surface instabilities and
planetery rotation have considrable roles too.
Originally posted by DrChinese
Mars has no atmosphere (ok, a little) and no ocean
(ok perhaps some buried ice).
According to the latest estimates that "some"
buried ice could've covered the entire planet's
surface (if it were flat) and be 100 meters deep.
There's also the part about oxygen on Earth
being freed by microbes or something over the years.

Mars is too far-away from the Sun and hence
too cold, and it has a lower mass which also
makes the atmosphere part problematic.

BTW, if all the CO2 that is estimated to be in
the "dirty" ice covering its poles is relased
into the atmosphere the planet can "heat up"
considrably, I think.
Originally posted by DrChinese
Another - as you mentioned - restrictive requirement is the orbit shape and distance from the star. A planet like Earth could orbit at any distance from the sun, even as far out as Pluto. Yet only a small range - perhaps 80-100 million miles from the sun (depending on mass of the star) would provide a temperature for water which would allow life to exist. If an elliptical orbit brought the planet too close to the sun, life would boil off. So the eccentricity could not be much.
I'm not certain about the range being so limmited.
If Earth was as far as Mars it is possible that
life could form and exist there. (Denser CO2
atmosphere - higher tempratures.) And, like I
mentioned before, there are other options
(like the case of Europa).

As for eccentricity, I don't have the scientific
data and calcs to support this, but I think that
planets at relativly close proximity to the star
(below say half a billion miles for Sun-like and
smaller stars) would not ussualy have very eccentric
orbits becuase of the way they are formed.
Originally posted by DrChinese
So personally, I can't imagine more than a few hundred earthlike planets orbiting suns of the correct mass/age and in the proper orbit per galaxy. And that is before we start talking about the evolution of intelligent life on such a planet.
My estimate was about 50,000 for planets
that at least evolved the most basic life forms
(bacteria) including those that evolved more
complex life but not intellegent yet or where
intellegent life was already destroyed.
NOT necessarily earthlike planets.

I'm optimistic, I know... :wink:

Live long and prosper.
 
  • #33
CJames
369
0
I don't think it is pessimistic to look at the data and come to conclusions about the odds. Then again, maybe I'm pessimistically construing the data. ;)

Who cares ?
In a perfect simulation you can have infinite
fun ! Many sufficiently advanced civilizations,
in my opinion, will realize that that's the most
important thing...
I hate to say it drag but that...that sounds pessimistic! To think that every intelligent species out there surrenders reality and decides to live connected to meaningless existences in simulated realities is about as depressing an idea to me as I can think of...sorry.

I probably won't be able to respond for a while my iternet is down and this is somebody elses. :(
 
  • #34
DrChinese
Science Advisor
Gold Member
7,694
1,543
Originally posted by drag
Greetings DrChinese !

I don't know. How narrow and why ?
After all, the "surge" of complex life forms
on the planet began just a few million years
ago. I don't know what triggered it (there was
a lot of orgamisms for billions of years before
that). Also, if it weren't for that Yukatan
astroid, you'd probably have huge dino-cities
covering the planet by now and dinos expanding
in the galaxy. I recently saw a program where
they were talking about a dinosour just a bit
larger than us that had a brain as complex as
that of our pets. It evolved "just" before the
above "accident".
Mammals started about 120+ million years ago. I don't see anything that requires that an intelligent species would come to dominate a planet as we do (I guess "dominate" may be subjective). Anyway, what I am saying is that there could be 1000 planets with tigers and monkeys as the highest intelligent lifeforms for every one that ends up with intelligent civilizations.

Hmm... I suppose that the Moon did help a bit,
but I think that surface instabilities and
planetery rotation have considrable roles too.

According to the latest estimates that "some"
buried ice could've covered the entire planet's
surface (if it were flat) and be 100 meters deep.
There's also the part about oxygen on Earth
being freed by microbes or something over the years.

Logically, buried ice itself means very little. Look at Antarctica - not exactly a hotbed. And the oxygen on Earth came from our CO2 atmosphere. So there is clearly a minimum size of planet - so as to provide an atmosphere.

As for the tides, I admit that rotation of the planet makes a difference. The planet would then need to rotate, which it probably does anyway to insure that the temperatures don't get too extreme. So I am not certain I am right about the moon being necessary.

But I think the ocean is a requirement so as distribute early life forms over the planet to give them new areas to evolve. Patches of water would essentially require all of the early evolution - before the advent of legs - to occur in a tiny area.

Mars is too far-away from the Sun and hence
too cold, and it has a lower mass which also
makes the atmosphere part problematic.

BTW, if all the CO2 that is estimated to be in
the "dirty" ice covering its poles is relased
into the atmosphere the planet can "heat up"
considrably, I think.
An atmosphere from buried ice? I think you watched "Total Recall" too many times. (Just a little joke.) That's definitely a stretch, because it would have to melt, release an entire planet's worth of gas, and then not blow out into space. Considering we are trying to talk about the probabilities, not the possibilities, I say that doesn't fly.

I would be the last person to deny the possibility of another intelligent species in the universe. Obviously, what was possible on Earth is possible elsewhere.

I'm not certain about the range being so limmited.
If Earth was as far as Mars it is possible that
life could form and exist there. (Denser CO2
atmosphere - higher tempratures.) And, like I
mentioned before, there are other options
(like the case of Europa).

As for eccentricity, I don't have the scientific
data and calcs to support this, but I think that
planets at relativly close proximity to the star
(below say half a billion miles for Sun-like and
smaller stars) would not ussualy have very eccentric
orbits becuase of the way they are formed.

Live long and prosper.

I would grant that life could possibly exist on a planet whose orbit went out farther than Earth's, not sure about all the way to Mars. But it couldn't go much farther in, either. Maybe the range is 80-110 millions miles from the Sun. That would need to be the limits for the eccentric orbit as well.
 
  • #35
drag
Science Advisor
1,100
1
Greetings !
Originally posted by DrChinese
Mammals started about 120+ million years ago. I don't see anything that requires that an intelligent species would come to dominate a planet as we do (I guess "dominate" may be subjective). Anyway, what I am saying is that there could be 1000 planets with tigers and monkeys as the highest intelligent lifeforms for every one that ends up with intelligent civilizations.

Ooops... Did I say "a few million years" ?!
I meant "a few hundred million years"(400-500).

But, after that I made a point about the
dinasours heading in the big brain direction too.
So, this may not be a must, but I think that
given sufficient time (say up to a billion years),
complex life is likely to evolve "intellegent"
(at similar to our level) beings. It took a lot
less on Earth, after all.

Then again, dolphins have brains that are larger
than ours and yet you don't see them building
civilizations. I guess this is an open question
until we get some alien "examples".
Originally posted by DrChinese
An atmosphere from buried ice? I think you watched "Total Recall" too many times.
Arnold Shwartzneger rocks !
Originally posted by DrChinese
That's definitely a stretch, because it would have to melt, release an entire planet's worth of gas, and then not blow out into space. Considering we are trying to talk about the probabilities, not the possibilities, I say that doesn't fly.
Yeah, it's a VERY long shot, but I once considered
what would happen if we nuked the poles
"big time". All that CO2 got'ta add a degree
or two...

Live long and prosper.
 

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