Why we're the only intelligent life in our galaxy

[KimB]

In response to this post here, I (for once) decided to go ahead and reply in a different thread instead of going further off-topic. So in response to Druga Runda's post, I'd like to quantify why I think we're the only intelligent life in the galaxy at the current time.

First of all, bear in mind that I am only claiming that we are most likely the only intelligent life in our galaxy at present: I'm sure there are other galaxies out there somewhere that are inhabited by intelligent life.

Now, on to the argument.

First, consider the span of time required for a civilization to go from inception to space travel. In the case of the Earth, this is likely to be a few tens of thousands of years (roughly 30k or so years). Now, imagine such a civilization that has advanced to the point where it can detect and colonize nearby planets that are not habited by intelligent life (we may be capable of such in a couple hundred years, if not much sooner). We might imagine that such a civilization can reach said planet, colonize it, and grow to the point where it can send its own colony out again within 1000 years.

So, if we imagine that every habited planet in the above civilization founds a new colony every thousand years, and if there were a habitable planet around every single star in the galaxy (about 200 billion stars), such a civilization could colonize every star in our galaxy within 38,000 years.

Thus, total time from initial civilization to colonization of galaxy: roughly 60,000-70,000 years.

That is an absurdly miniscule timescale compared to the time scales that lead up to the evolution of intelligence.

 

[Tahir2]

Anyone and everyone read Are we Alone by Paul Davies.

 

[Guden Oden]

Flawed logic. Your argument assumes other civilizations develop in a pattern similar to mankind's (if what we got would count as that).

You also assume other civilizations would be interested in colonization...

Besides, every star in the galaxy most likely isn't capable of hosting (higher) life, so there falls that bit too.

Sorry. We can't REASON our way into concluding we're unique in a galaxy that consists of many billions of stars. That's as stupid as Aristothel's delusions about all matter consisting of various proportions of earth, water, air and fire.

 

[KimB]

Flawed logic. Your argument assumes other civilizations develop in a pattern similar to mankind's (if what we got would count as that).

Only in part. Most of the argument is merely about the evolution of life here on Earth. Life has existed on Earth for something like 3.5 billion years or so. For most of that time it would have been habitable to a species like us. If, upon obtaining the capacity to colonize the galaxy, it only takes a few tens of thousands of years for any intelligent life to spread across it (I believe my time scales for colonizing the galaxy provide a realistic upper bound on the amount of time it would take...it should require much less in reality), then why isn't intelligent life from elsewhere already here?

And it seems to be basically a law of evolution that as life forms become more complex, their evolution accelerates. The evolution of any life should follow this simple rule: that the evolution of the more complex species, and of a society once intelligence is obtained, will be much shorter than that which came before.

So, I think we can rule out pretty conclusively that no intelligent life in our galaxy evolved before about one million years prior to now (and I hope you will agree that this is a very generous time span, many times that of the evolution of Earth's society). If no intelligent life evolved prior to one million years before now among 200-400 billion stars, which includes most of the life span of the galaxy (many billions of years), then intelligent life must indeed be rare.

Although, there is an alternative conclusion: one alternate possibility that is completely consistent with the above argument would be that intelligent life is likely to destroy itself before obtaining the ability to leave the planet. In this scenario, we are a bit more likely to find primitive civilizations on other planets, but very likely to find dead ones, if we start spreading across the galaxy. I personally don't like this argument, as it seems to be fundamentally against that which we know about life: that its primary goal is to survive.

You also assume other civilizations would be interested in colonization...

Not as such. A civilization that would be interested in colonization is merely one that is interested in spreading itself. I propose that any civilization that is not interested in spreading itself would never become the dominant civilization on a planet.

Besides, every star in the galaxy most likely isn't capable of hosting (higher) life, so there falls that bit too.

Clearly. I was attempting to provide an upper-bound on the time it would take to colonize the galaxy.

 

[bloodbob]

So, if we imagine that every habited planet in the above civilization founds a new colony every thousand years, and if there were a habitable planet around every single star in the galaxy (about 200 billion stars), such a civilization could colonize every star in our galaxy within 38,000 years.

Your assuming this civilisation can travel faster then the speed of light. If that is the case maybe they have traveled to other galaxies rather then completely populating the current galaxy.

 

[KimB]

Your assuming this civilisation can travel faster then the speed of light. If that is the case maybe they have traveled to other galaxies rather then completely populating the current galaxy.

The milky way is about 12,000 light years in diamter. No faster-than-light travel needed. Near-light travel isn't that hard if you have a constant, long-duration power source.

Some stats on the Milky Way:
http://www.encyclopedia.com/html/section/MilkyWay_SizeandShapeoftheMilkyWay.asp

 

[bloodbob]

The milky way is about 12,000 light years in diamter. No faster-than-light travel needed. Near-light travel isn't that hard if you have a constant, long-duration power source.

Some stats on the Milky Way:
http://www.encyclopedia.com/html/section/MilkyWay_SizeandShapeoftheMilkyWay.asp

Chalnoth read the whole thing its talking about the size of the bludge.

That is unless we are no longer in the milkyway
http://www.encyclopedia.com/html/section/MilkyWay_SizeandShapeoftheMilkyWay.asp

he sun lies roughly two thirds of the way from the center of the disk, which is some 28,000 light-years distant, and in the galactic plane.

 

[KimB]

Oh, damn, you're right. Here's the correct number from the same source:

The diameter of the disk is c.100,000 light-years; its average thickness is 10,000 light-years, increasing to 30,000 light-years at the nucleus.

This places our galaxy at about 3 times the size of your average spiral galaxy, which is why I didn't balk at the numbers I originally came up with.

Anyway, 40k years vs. 100k years doesn't change the argument one bit. At 100,000 light years diameter, with us at about 28,000 light years from the center, the furthest point from us is about 70,000 light years distance, so 100,000 years for colonization isn't unreasonable, but we could put it at 200,000 years and it still doesn't change the argument.

 

[NANOTEC]

Ok let me see if I got this right. Our galaxy has 200 billion stars correct? I think from the number alone, we can probably say with a certain amount of certainty that there are other forms of intelligent life in our own galaxy. Question is are they more intelligent or less intelligent than we are? If they are more intelligent than we are why would they want to interfere with our species? Why would they want to interfere with our evolutionary process? Why not just study us from a distance? Maybe they've already visited us without our knowledge? Maybe they've already taken samples of our species and cloned them for further analysis? What woulld they benefit by contacting us? How do we know that we're not just an experiment created by them? Of course all of this assumes they've developed a mechanism to travel to distant stars.

Think about it. If we had the means don't you think we would use one of the billions of planets out there to conduct evolutionary experiments? I certainly would. If I had the biotechnology to bioengineer an alternate life form and put it into an environment to see it evovlve I would. In fact we're do that right now but with cells instead of compete organisms. If you could, what kind of organism woud you bioengineer? Why? Where would you let it live?

 

[nutball]

Flawed logic. Your argument assumes other civilizations develop in a pattern similar to mankind's (if what we got would count as that).

You also assume other civilizations would be interested in colonization...

Can you name an environmental niche on Earth which is capable of supporting life but has not been colonized by some species or other?

 

[nutball]

Ok let me see if I got this right. Our galaxy has 200 billion stars correct? I think from the number alone, we can probably say with a certain amount of certainty that there are other forms of intelligent life in our own galaxy.

Why? Why do you think it's possible to say that with any certainty whatsoever? Do you magically have some sort of estimate for the probability of evolution of intelligent life? (an estimate which as elluded the greatest minds working on the problem, because errr... it's impractical and fruitless to try to calculate it)?

 

[NANOTEC]

Why? Why do you think it's possible to say that with any certainty whatsoever? Do you magically have some sort of estimate for the probability of evolution of intelligent life? (an estimate which as elluded the greatest minds working on the problem, because errr... it's impractical and fruitless to try to calculate it)?

Simply because life may be capable of evolving in ways that are different than our own. The flaw in thinking by the greatest minds is using what we KNOW instead of what we DON'T know. 300 years ago, nobody ever thought we'd be able to fly or clone organisms. What we know is likely a drop in the bucket. The greatest minds think evolutiion was due to spontaneous generatiion. Where is this proof? Where is the proof that other life forms need to follow this theory?

If Jesus was real, how would you explain it? Was he a life form from another planet sent here for whatever purpose? Did he evolve from apes? We cannot even prove whether Jesus was real or not.

 

[Guden Oden]

Can you name an environmental niche on Earth which is capable of supporting life but has not been colonized by some species or other?

There are some that are capable of supporting life, but the highest order life able to survive there are mollusks and crustaceans. You won't get far as a space-faring race with tubeworms and crabs as your mothers and fathers.

Besides, both mars and venus are technically capable of supporting A kind of life, but so far we haven't found any...

 

[nutball]

Simply because life may be capable of evolving in ways that are different than our own. The flaw in thinking by the greatest minds is using what we KNOW instead of what we DON'T know. 300 years ago, nobody ever thought we'd be able to fly or clone organisms. What we know is likely a drop in the bucket.

So you're basing the truth of your assertion deliberately and specifically on lack of knowledge to the contrary?

But none of what you've said backs up your assertion that there must be intelligent life elsewhere in our galaxy. The "great minds" are (or bloody well should be) well aware of where the gaps are in the knowledge, it's precisely the reason why it's impractical to come up with an estimate of the probability of the evolution of intelligent life -- because there are too many unknowns.

It is not correct to think that the holes in scientific knowledge can be filled with whatever you can imagine. OK it makes for a good science ficition book, but the Universe is the way the Universe is, regardless of our knowledge or imagination.

The greatest minds think evolutiion was due to spontaneous generatiion.

Do they? That's news to me.

 

[nutball]

There are some that are capable of supporting life, but the highest order life able to survive there are mollusks and crustaceans. You won't get far as a space-faring race with tubeworms and crabs as your mothers and fathers.

So the rules of the game for life on Earth seem to be "grab all you can get, if there's something going free make a grab for it"? Would you agree?

(Kind of like the rules which govern human "civilization")?

 

[NANOTEC]

So you're basing the truth of your assertion deliberately and specifically on lack of knowledge to the contrary?

But none of what you've said backs up your assertion that there must be intelligent life elsewhere in our galaxy. The "great minds" are (or bloody well should be) well aware of where the gaps are in the knowledge, it's precisely the reason why it's impractical to come up with an estimate of the probability of the evolution of intelligent life -- because there are too many unknowns.

It is not correct to think that the holes in scientific knowledge can be filled with whatever you can imagine. OK it makes for a good science ficition book, but the Universe is the way the Universe is, regardless of our knowledge or imagination.


Do they? That's news to me.

So basically you're saying the greatest minds are saying that they don't know how life on earth evolved? I could've told you that.

As to why I think that there are likely other forms of life in our own galaxy, well it comes down to probability. I think the probablility that we are the only intelligent life in our galaxy is low. I come to this conclusion based on the things we don't know. I think everyone can agree that we don't know much since we're discovering news things everyday.

 

[nutball]

As to why I think that there are likely other forms of life in our own galaxy, well it comes down to probability. I think the probablility that we are the only intelligent life in our galaxy is low.

I'm asking for a scientific justification of why the probability is low. Not a religious one, a scientific one. What is your scientific justification for assigning a "high" probability to the existence of life elsewhere in the galaxy?

I come to this conclusion based on the things we don't know.

That's not scientific, that's religious. We don't know that God doesn't exist; by your logic that proves that God does exist.

OK try this:

nutball says: "I think that the probability of the existence of intelligent life elsewhere in the galaxy is very low, based on a total lack of information".

Now my assertion totally contradicts yours, and it is based on the same logical foundation as yours so must carry the same weight. Where do we go from here? We have two baseless and diametrically opposed hypotheses and zero information as to which is closer to the truth. We've generated a lot of entropy and zero insight. We are to all intents and purposes having a religious/philosophical debate and not a scientific one.

Look, if you want to postulate the existence of life elsewhere as the pre-cursor to some other thought experiement by all means go ahead. But it is a postulation, it's not a basis for an argument in fact.

 

[Mintmaster]

This argument is a bit sketchy, Chalnoth. You're assuming everything occurs as it has here on Earth.

Life may not have the same DNA fingerprint in other galaxies. The time constants for evolution could be different by orders of magnitude. The environmental influences may not favour intelligence to the same degree as here. The lifespan of these beings may not permit acquiring enough cumulative knowledge to get as far as space travel. Their cognotive thought may not be transferable from survival tactics to abstract concepts like ours. There may be a dearth of resources needed for sophisticated industrialization. Their planets may only be able to sustain a fraction of the population, thus statistically increasing the time between super geniuses that make the next leap. Etc, etc.

Another factor I've always thought about is how lucky we are that civilization took so long to form. It's only taken ~30K years for civilization to rapidly develop for us, and I don't think we've genetically changed much for ~200K years. Something sparked civilization for us, and today we can clearly see that our capacity for thought is overkill for simply having a functioning society. Now, our standards/ethics have heavily nullified the natural selection that got us where we are, so IMHO our biological evolution (especially intellectually) will proceed at a greatly reduced rate, if not stop completely. So what if that spark happened a million years ago or earlier? We may have much lower ceilings on our intelligence level.

Anyway, you can see that there's a myriad of factors that paved the way for the history of earth and our civilization's formation. To assume that others would come about in the same manner with the same capability is rather myopic.

 

[Druga Runda]

hey thanks Chalnoth

I'd say that the argument is about "if we are not alone why doesn't someone capable come and contact us" which seems the only plausible conclusion from our "human" POV.
While technically I agree with your reasoning, on speed of colonization I do not agree with the premise that colonization is necessary outcome of intelligence capable to execute it. Your conclusion does not take an important aspect into account - and that is social development of "us" the intelligent civilization of this planet. That aspect is clearly observable here on earth with us humans, and I think that you could agree with the proposition which would say that more we develop - more different are our goals from pure "natural selection" goals.

The social development goals are markedly different from pure natural selection which was the driver of evolution until we developed. We as "the civilization" are able to comprehend and act on some ideas which have nothing to do with natural selection process. Natural selection is not the driver of evolution anymore, it is us - the civilization. While we still at this point go by "stronger makes the rules" and "fittest survies" for the most part, we did evolve to the point where we can recognize the ideas such as "greater good" for all including other life forms. Many of us already understand that sustainable development, coexistance etc are the only long term solution for our survival on this planet.

Thinking just how far we came as a society from lets say 500 years ago to today, it is not hard to imagine that we will change (and need to) in next 1000 in order to be able to live in acceptable conditions just on this planet. (not to mention potential million or billion further years of social and technological development)

Further social development of a civilization should make it to become benevolnet and "seamlessly integrated*" in the environment as opposed to the "destroy and conquer" attitude. The civilization going by "fittest survives" rules is almost certain to destroy itself, and it is just the matter of time that just an individual in a society with such premise will execute it on its own and create a real catastrophe that will almost anhilate it. (think Hitler with more advanced technology available) I assume that after that kind of shock a civilization - if it manages to survive - is bound to became one that cares more about the whole than just about itself, and if that does not change "Hitler" will appear again and again until that civilization either destroys itself or changes to one that "seamlessly integrates" with other individuals and with the environment around it. Thus I'd say it is most likely that whatever is out there is more keen to let us get to this point on our own and the "colonization (or contact) is a certainty" idea for the spread of intelligent life across the galaxy does not necessarily hold true.

That is the "social" part of the reasoning, for no "official contact" fact on this planet.

With the evolutionary part I agree with Chalnoth that with the numbers involved it should be reasonable to expect some kind of life to evolve elsewhere, even in our galaxy. The reason for it is just looking at the timescales involved for our own evolution comparing with the timescales involved in the age of our universe or just our own galaxy, the abundance of stars, and the abundance of life >everywhere< on our own planet including the vulcanic vents at the bottom of the oceans with no light source available. It shows us that life could exist in much harsher conditions than we though of previously.

For Nutball - comparing intelligent life with primitive life forms, is not really comparing like with like, in order to conclude that intelligent life would spread so readily as the lower life forms spread on this planet. As for magically comparing the numbers, well that cannot be done of course, and this is why we as the civilization are not capable of "confirmation" that there is something out there, nevertheless I would say that circumstantial evidence should point out in this direction as opposed to the "we can't see it so it's not there" type of reasoning.

However one of the points that I made in the first post, is that there are plenty of weird beliefs and teachings across all earths cultures indiscriminately, which should indicate that "no contact proposition" is not so straight forward as it seems. All big religions at their core have the "love thy neighbour", moral codes, plus stuff like angels etc... pretty much at its heart, (even thought it is all corrupted with organizing that religions into human lead institutions for profit and explotiation, the core teachings are still preserved) Assigning it all to imagination is to me a bit of a far fetched propositon. The proposition that there are reasons why there is "no official" recognition at this moment in time are much more plausible for me.

 

[KimB]

Life may not have the same DNA fingerprint in other galaxies. The time constants for evolution could be different by orders of magnitude.

That's fine. But if the time constraints are much shorter, then they'd be here. If the time constraints are much longer (by more than a factor of two), then they wouldn't be able to evolve very far before being reset by mass extinctions, and would eventually just be killed off by their own star. Or, even if by chance they managed to survive long enough to produce intelligence, if their evolution is one order of magnitude slower than ours, they wouldn't have had time to develop yet.

But beyond that, it seems that the more we learn about the origins of life, the more it seems that life as it exists on Earth is an inevitable consequence of having the right conditions. As one quick example, take ATP. ATP is used for basically all of cell metabolism in all life forms on Earth. But there are three other molecules that would do just as well as ATP for the job, and are also made use of: GTP, CTP, and UTP. Why aren't these used for energy? When you get the right conditions, you can create these molecules randomly, but ATP is produced in much larger quantities. So early life forms that relied upon the use of ATP survived. This isn't due to the environment of the Earth: it's due to basic chemistry.

The lifespan of these beings may not permit acquiring enough cumulative knowledge to get as far as space travel.

Life span appears to be directly tied to metabolism, and metabolism to body mass. Organisms which are smaller tend to have shorter lifespans, but if the organism was too small, it most likely could not develop intelligence.

Their cognotive thought may not be transferable from survival tactics to abstract concepts like ours.

Then they wouldn't be considered intelligent.

There may be a dearth of resources needed for sophisticated industrialization.

The chemical composition of the planet may indeed vary greatly. But to have a planet at all you essentially need to have the planet made largely out of metal, which is basically the only thing that industry needs but life does not. So there's bound to be some metal near the crust (besides, Iron is the most stable element, and is therefore relatively abundant among the heavy elements).

Their planets may only be able to sustain a fraction of the population, thus statistically increasing the time between super geniuses that make the next leap. Etc, etc.

But planet mass is directly tied to the atmosphere. Too little mass and the atmosphere evaporates before life can evolve (see Mars). Too much mass and you end up with a large atmosphere with a greenhouse effect killing off life (see Venus). Remember that for life to evolve, current understanding is that you need liquid water. Thus, the temperature of the planet must be similar to that of Earth, and thus for it to hold an atmosphere of the right composition, it must be roughly the same mass as Earth's.

Another factor I've always thought about is how lucky we are that civilization took so long to form. It's only taken ~30K years for civilization to rapidly develop for us, and I don't think we've genetically changed much for ~200K years. Something sparked civilization for us, and today we can clearly see that our capacity for thought is overkill for simply having a functioning society.

Sure. But you need to have a functioning society for intelligence to be recognized. Hell, the chances are a bit higher that we'll find another planet that has a pre-intelligence species (similar to the pre-human species) than we find one with a functioning society. But not that much higher (pre-intelligence humanoid species were in existence for ~4 million years or so...still miniscule in cosmic time). Yet if we did manage to stumble across a planet with such a species, we would consider them to be unintelligent animals, until we discovered how much they could be trained. Such a situation would produce a moral conundrum for the colony.

Now, our standards/ethics have heavily nullified the natural selection that got us where we are, so IMHO our biological evolution (especially intellectually) will proceed at a greatly reduced rate, if not stop completely. So what if that spark happened a million years ago or earlier? We may have much lower ceilings on our intelligence level.

And then we wouldn't have spread so quickly across the globe, and another species with higher intelligence potential would arise and take over instead. Humans are the only intelligent species on Earth precisely because we were able to produce a fully-functioning society that was able to spread across the globe and begin to dramatically alter the landscape. We are naturally supressing the development of a new intelligent species: if we were much less intelligent, we couldn't do that.